Percutaneous interventional cardiovascular medicine: The PCR-EAPCI Textbook

Summary

Structural heart disease includes a heterogeneous group of non-coronary heart diseases where catheter-based interventions have become a feasible therapeutic option in the last decade. Accurate preprocedural evaluation and optimal guidance are crucial to optimise the results and minimise the complications of these procedures. Fluoroscopic and haemodynamic assessments have been the key to guiding percutaneous treatment of structural heart disease. However, the wide spectrum of structural abnormalities and the poor soft-tissue resolution of cine-angiography demand the use of complementary imaging techniques with higher spatial resolution to characterise better the structural lesion and select the most appropriate therapeutic approach. Non-invasive imaging techniques such as echocardiography, magnetic resonance imaging (MRI) and multi-detector row computed tomography (MDCT) are currently considered the foremost imaging tools to diagnose structural heart disease and play a central role in patient selection for percutaneous interventions. In addition, fusion of these imaging technologies (MRI and MDCT) with live x-ray is a promising tool to guide the procedures. Furthermore, novel techniques such as videodensitometric quantitative angiography has been introduced as a potential tool for guidance of aortic and mitral interventions [1, 2] There is also emerging tools with a potential for personalised transcatheter interventions using in silico modelling and procedural simulation.

In this chapter, the role of non-invasive imaging techniques to characterise structural heart disease and select candidates for transcatheter treatment will be reviewed, with special focus on valvular heart disease and atrial and ventricular septal defects. In addition, a detailed description of the procedural guidance and evaluation of the results with non-invasive imaging modalities will be provided.

Transcatheter aortic valve implantation

View chapter "Transcatheter aortic valve implantation"

The results of the Placement of Aortic Transcatheter Valves (PARTNER) trial confirmed the superior efficacy of transcatheter aortic valve implantation (TAVI) compared to medical treatment and balloon valvuloplasty in patients with severe symptomatic aortic valve stenosis who are considered inoperable [3]. Patients who were treated with TAVI had superior long-term prognosis as compared to patients who received conservative treatment (including balloon valvuloplasty) [3]. With more than 60,000 patients treated worldwide in 2013, which was increased to >250.000 patients worldwide in 2017 [4]. TAVI has established as a feasible therapy for patients with severe symptomatic aortic stenosis who are deemed not operable, later in, the United States Food and Drug Administration (FDA) has approved TAVI in patients with severe aortic stenosis at intermediate risk [5] and low risk[6] for death or major complications associated with open-heart surgery [7, 8, 9, 10, 11, 12]. Recently, the ESC guidelines recommended TAVI for patients (≥75 years) with severe symptomatic aortic stenosis with favourable anatomy and at high or intermediate risk for surgical aortic valve replacement[13]. In contrast, the American guidelines extended the TAVI indications into younger (> 65 years) and lower surgical risk patients[14]. Non-invasive multimodality imaging is crucial to accurately select the patients who are candidates for this therapy and provides a valuable aid to fluoroscopy during the procedural guidance. In addition, the procedural results are better evaluated with a combination of different imaging modalities that integrate function and anatomy. ( Table 1 ) summarises the role of multimodality imaging during the various procedural steps (screening, procedural guidance and evaluation of the results) [15].

EVALUATION BEFORE TRANSCATHETER AORTIC VALVE IMPLANTATION

Accurate selection of candidates for this therapy is crucial to maximise the results and minimise the complications. The various steps that form the preprocedural evaluation are summarised in ( Table 1 ).

Confirmation of aortic valve stenosis severity

Echocardiography is the mainstay technique to evaluate aortic stenosis severity. Current European guidelines define severe aortic stenosis by the presence of [mean gradient >40 mmHg, peak velocity >4.0 m/s and valve area <1.0 cm² (or <_0.6 cm²/m²)] [13] [16]. Diagnosis of severe aortic stenosis may be challenging in patients with anatomically severe aortic stenosis and severe left ventricular systolic dysfunction, who often present with Low-flow, low-gradient aortic stenosis (mean gradient <40 mmHg, aortic valve area <1 cm2, LVEF <50%, stroke volume index (SVI) <35 mL/m2.[13]. In these patients, differentiation of a true severe aortic stenosis from a pseudo-severe aortic stenosis has important clinical implications since patients with true severe aortic stenosis will benefit from TAVI whereas patients with pseudo-severe aortic stenosis will not exhibit any significant clinical benefit. In true severe aortic stenosis, the fixed small aortic valve area determines an increased pressure afterload that further reduces the stroke volume. By contrast, in pseudo-severe aortic stenosis, myocardial disease is the primary cause of low-flow and incomplete opening of the aortic valve. Dobutamine stress echocardiography may help to unmask a pseudo-severe aortic stenosis, showing an increase of aortic valve area without significant increase in transvalvular systolic gradient [17].

Aortic valve annulus sizing

Accurate measurement of the aortic valve annular dimensions is crucial to select the most appropriate prosthesis size. Current transcatheter aortic valve prostheses with CE mark include the self-expandable Medtronic CoreValveEvolut-R/Evolut-PRO® (Medtronic, Minneapolis, MN, USA) and the balloon-expandable SAPIEN XT/SAPIEN3® valve (Edwards Lifesciences, Irvine, CA, USA), ACURATE neo/neo2 (Boston Scientific, Marlborough, Minnesota, USA), Portico transcatheter aortic valve system (Abbott, St Paul, MN, USA), JenaValve™ (JenaValve Technology, Inc., 4 Cromwell, Irvine, CA), Allegra (NVT GmbH, Germany), Myval (Meril Life Sciences Pvt. Ltd., India) and Hydra (Sahajanand Medical Technology Private Ltd., India).

The Medtronic THV prosthesis consists of a nitinol frame that holds a trileaflet porcine pericardium valve. The valve is currently available in four different sizes (23, 26, 29 and 34mm for an aortic valve annular diameter ranging between 18 mm to 20 mm, 20-23 mm, 23-26 mm or 26-30 mm, respectively).

The SAPIEN XT/SAPIEN 3 valve consists of a cobalt chromium cylindrical frame which holds a trileaflet bovine pericardium valve. Four different sizes are also available, according to the aortic valve annular dimensions (20, 23, 26 and 29 mm for an aortic valve annular diameter ranging between 16-19 mm,18 to 22 mm, 21 to 25 mm, 24 to 28 mm, respectively).

The ACURATE neo transcatheter self-expanding bioprosthetic aortic valves comprised of a nitinol frame with axial, self-aligning stabilization arches and supra-annular porcine pericardium leaflets. ACURATE neo2 represents an evolution of the valve design as it features an enhanced sealing skirt for further reduction of paravalvular leak. Three different sizes are available (S-small, M-medium, and L-large with respectively 23mm, 25mm and 27mm nominal diameter at waist level) for native annulus diameter range between 21 and 27mm[18] .

The Myval prosthesis is a next generation balloon expandable transcatheter heart valve, made of Nickel Cobalt alloy frame with hybrid honeycomb cell design with open cells towards the aortic end and closed cells towards ventricular end. It is equipped with AntiCa “anti-calcification” treated bovine pericardium tri-leaflet valve and an internal PET sealing cuff for lower profile and puncture resistance and an external PET buffing to minimise paravalvular leaks. The Myval aortic prosthesis are available in different sizes, (20mm, 21.5mm, 23mm, 24.5mm, 26mm, 27.5mm, 29mm, 30.5mm, and 32mm) for an aortic valve annular diameter ranging between 16-19 mm,17.5 to 20.5 mm, 18 to 22 mm, 19.5 to 23.5 mm, 21 to 25 mm, 22.5 to 26.5 mm, 24 to 28 mm, 25.5 to 29.5 mm, and 27 to 31 mm, respectively)[19] .

The Portico valve consists of a self-expandable nitinol frame with 3 bovine pericardial leaflets and a porcine pericardial sealing cuff, it’s available in four sizes, (23, 25, 27 and 29 mm for an aortic valve annular diameter ranging between 19-21 mm, 21 to 23 mm, 23 to 25mm and 25 to 27mm, respectively). More recently, the Navitor™ TAVI system from Abbott has been introduced to the market with similar sizes to the original Portico prosthesis. The new prosthesis offers intelligent design advantages, including smart PVL-sealing NaviSeal™ Cuff, aiming at mitigation of paravalvular leak.

The ALLEGRA valve is composed of a self-expanding, nitinol stent frame with a sewn-in supra-annular bovine pericardial heart valve. It has three sizes (23, 27 and 31 mm for an aortic valve annular diameter ranging between 19-22 mm, 22 to 25 mm, and 25 to 28 mm, respectively).

The JenaValve™ is a second-generation self-expandable device composed of a trileaflet porcine root valve mounted on nitinol double bowed struts with three positioning feelers. It is available in three sizes (23, 25, and 27 mm) in Europe, covering an aortic annulus range of 21–27 mm. It’s the only valve designed to treat both aortic regurgitation and aortic stenosis.

The Hydra aortic valve is a self-expandable nitinol-based supra-annular aortic system. It is available in three sizes (22, 26 and 30mm) for native aortic annulus diameters ranging from 18-27mm.

During the initial TAVI experience, 2-dimensional echocardiography has been used to size the aortic valve annulus. However, 3-dimensional imaging techniques such as MDCT or MRI have shown superior accuracy and reproducibility to measure this structure ( Figure 1 ) [20, 21, 22]. Two-dimensional echocardiography assumes a circular geometry of the aortic valve annulus whereas 3-dimensional imaging techniques show the oval shape of this structure. In a recent study including 53 patients treated with TAVI, the accuracy of 2-dimensional and 3-dimensional transoesophageal echocardiography (TOE) to size the aortic valve annulus was evaluated using MDCT as standard reference [21]. The circular aortic valve annulus areas were calculated with 2-dimensional and 3-dimensional TOE whereas the planimetered aortic valve annulus area was measured with 3-dimensional TOE. Compared to MDCT, 2- and 3-dimensional TOE aortic annular geometric circular assumption significantly underestimated the aortic valve annulus area (by 16.4% and 12.9%, respectively). In contrast, 3-dimensional TOE planimetered aortic valve annular areas showed the best agreement with the MDCT planimetered cross-sectional areas (9.6% of underestimation on average) [21]. In addition, the methodology used to size the aortic valve annulus may significantly influence the procedural strategy. The size of the prosthesis may change if the minimum, maximum or mean aortic valve annular diameters are considered [22, 23]. The clinical implications of these different approaches to measure the aortic valve annulus have been evaluated in a few studies [24, 25]. Using the Edwards SAPIEN prosthesis, Messika-Zeitoun et al demonstrated that the measurement of the aortic valve annulus with MDCT would have changed the procedure in 40% of patients [25]. Furthermore, if a Medtronic CoreValve system is implanted, the measurement of the minimum or the maximum diameter of the aortic valve annulus with MDCT would contraindicate the procedure in 26% and 39% of patients due to too small or too large aortic valve annular dimensions respectively [22]. Schultz and co-workers showed that the mean aortic valve annular diameter calculated from the minimum and the maximum diameters or from the aortic valve annular area increased the eligibility for TAVI using a Medtronic CoreValve device and the procedure would be contraindicated in 10% of patients due to too large annular dimensions [22]. Currently, MDCT is considered the standard imaging modality for pre-TAVI assessment of aortic annulus, coronary heights, commissural alignment, aortic calcium quantification and vascular access [26] Alternative tools such as 3D Echocardiography or MRI could be only used if MDCT is not feasible.

Approach

First in human TAVI was done through the antegrade trans-septal approach [27], then the transfemoral artery has been the standard approach for most of the patients. In patients with significant femoral or iliac disease, the trans-axillary, trans-carotid, or trans-apical approach can be used. Trans-apical approach is the most invasive approach and can’t be used in some patient with poor LV function. Direct aortic approach with mini sternotomy has been used in selected cases with no available peripheral access. Trans-caval approach can be used is cases where all other arterial approaches are not available. [28]

Aortic root dimensions

In addition to the aortic valve annular size, the dimensions and spatial relationships of the aortic root are important aspects to be evaluated before TAVI. Manufacturer’s recommendations include sinus of Valsalva width, sinotubular junction and ascending aorta diameters as important anatomical requirements to be considered before TAVI. Particularly, the Medtronic CoreValve prosthesis, with a 50 mm frame length, covers the entire aortic root and the upper third of the device sits within the ascending aorta and orients the prosthesis in the direction of the ascending aorta and blood flow. A sinotubular junction diameter >40 mm and an ascending aorta diameter >43 mm are contraindications to implant this device.

Furthermore, it is important to assess the height of the coronary ostia relative to the aortic valve annular plane in order to anticipate potential fatal complications such as the occlusion of one of the coronary ostia ( Figure 2 ) [24]. When the transcatheter aortic prosthesis is deployed, the aortic valve cusps are displaced towards the aortic root walls. If the relative height of the coronary ostia is too low, severe bulky calcified aortic cusps may occlude one of them. This complication is infrequent and current prosthesis devices have permeable struts in the two third upper parts that allow normal blood flow. Neo-commissural alignment using pre-TAVI MDCT has become an important step in current TAVI practice to prevent coronary artery overlap and allows future coronary access or redo TAVI.[29]

Echocardiography is the most widely available imaging technique to evaluate these parameters. However, it is recommended to use 3-dimensional imaging modalities such as MDCT and MRI, which permit appropriate alignment of the multiplanar reformation planes to obtain the most accurate visualisation and measurements of these structures ( Figure 2 ) [26]

Peripheral arterial anatomy

In patients eligible for TAVI, assessment of the aorta and peripheral arteries is a crucial step in selecting the appropriate procedural approach. In patients who are candidates for TAVI, the prevalence of peripheral arterial disease is high. According to current guidelines and manufacturer’s recommendations, a small calibre (<6.5 mm to 5.5 mm for a 18F delivery system) [28] or heavily calcified ilio-femoral artery system are contraindications for a transfemoral approach [22]. Similarly, the risk of vascular injury or embolic complications during a transfemoral procedure is substantially increased in the presence of a tortuous ilio-femoral arterial tree or porcelain aorta. Accordingly, in such patients, the transapical, trans-carotid, direct aortic or trans-axillary approach may be preferred over the transfemoral approach. More refinement of technology is needed to overcome these limitations. Some techniques such as balloon angioplasty and/or lithotripsy could be used to facilitate transfemoral access in difficult cases [30, 31].

Invasive angiography has been the reference standard to assess the ilio-femoral artery system. However, non-invasive tomographic imaging approaches, such as MDCT and MRI, may allow more detailed evaluation of peripheral arterial size, tortuosity and extent of calcifications ( Figure 3 ). The experience with MRI to evaluate anatomy and dimensions of the peripheral arteries prior to TAVI is yet limited, but pre-procedural assessment of peripheral arterial anatomy with computed tomography has been demonstrated in various studies [25, 32]. Kurra et al evaluated 100 consecutive patients who underwent MDCT as part of the clinical workup prior to TAVI [32]. In 35% of those patients, unfavourable anatomy for transfemoral access was identified with 27 patients having a small minimal luminal diameter (defined as < 8 mm), 12 patients having severe calcifications at the iliac bifurcation (defined as >60% circumferential calcification) and 4 patients increased tortuosity of the iliac arteries (defined as an angulation of <90°). Currently, MDCT is the most widely used imaging modality to assess the peripheral vascular access [26] However, a major drawback of MDCT evaluation remains the risk of contrast-induced nephropathy, restricting its use in patients with reduced renal function. To overcome this limitation, Joshi et al evaluated the feasibility of ultra-low-dose intra-arterial contrast injection protocol for MDCT imaging of the ilio-femoral arterial tree and compared findings with conventional invasive angiography [25]. With the use of 12 ± 2 ml of contrast on average, excellent image quality was achieved in 92% of patients. Interestingly, MDCT angiography revealed arterial dimensions not suitable for transfemoral access in 17 out of 43 (40%) femoral arteries that were initially deemed suitable based on invasive angiography. Finally, in patients with contraindications to MDCT, magnetic resonance angiography may provide a useful alternative to evaluate the presence of peripheral arterial disease with high diagnostic accuracy [33].

Exclusion of contraindications

Other factors that remain to be evaluated prior to TAVI include coronary artery anatomy, left ventricular dimensions and function and concomitant severe organic mitral regurgitation. Since the presence of severe coronary artery disease not amendable for percutaneous intervention constitutes a relative contraindication for TAVI, prior knowledge of coronary artery integrity is preferred. The preprocedural MDCT (or potentially MRI) evaluation can be used for this purpose ( Figure 4 ). However, its diagnostic accuracy in the detection of significant coronary lesions is reduced in the presence of severe coronary calcifications, which are highly prevalent in TAVI candidates. Invasive coronary angiography therefore remains the preferred method.

Left ventricular function and geometry are important factors to take into consideration during the preprocedural screening. Severe left ventricular systolic dysfunction increases the risk of haemodynamic instability during the procedure. Impaired baseline global longitudinal myocardial strain has shown prognostic value especially in patients with normal left ventricular ejection fraction [34] . The presence of a pronounced hypertrophic sigmoid septum may challenge the procedure and stable position of the device may be difficult. Three-dimensional imaging techniques, such as MDCT or MRI provide detailed characterisation of the dimensions of the left ventricular outflow tract and the thickness of the septum. In addition, novel post-processing MDCT data software permits the anticipation and planning of the transapical approach ( Figure 4 ).

While MRI and to some extent MDCT allow evaluation of left ventricular function, routine echocardiography is most commonly applied to determine left ventricular ejection fraction. Administration of contrast can be used to enhance endocardial border delineation and thus provide more accurate assessment of left ventricular volumes and function. Finally, the administration of contrast also aids in the detection of intraventricular thrombus, which represents an important contraindication ( Figure 4 ).

Furthermore, the presence of severe organic mitral regurgitation is considered a contraindication for TAVI, and accurate evaluation of the severity of valvular dysfunction with Doppler echocardiographic techniques is mandatory. In addition, 3-dimensional echocardiographic techniques may help to accurately quantify the regurgitant volume and localise the lesion.

NON-INVASIVE IMAGING TO GUIDE TRANSCATHETER AORTIC VALVE IMPLANTATION

TOE has been widely used as complementary imaging modality to fluoroscopy to guide TAVI. A major drawback of TOE is the need for general anaesthesia. Currently, the majority of TAVI procedures in high volume centers particularly in Europe and USA use a minimalistic approach, which relies on conscious sedation and fluoroscopy for guidance. Yet, many centers relies on TOE during their initial TAVI experience.[35, 36] Novel fully-sampled matrix array transoesophageal transducers allowing 3-dimensional visualisation of cardiac structures provide excellent aid and overcome the poor soft-tissue resolution of fluoroscopy. In addition, there is growing interest on fusion imaging modalities, rotational angiography and real-time MRI to guide the procedure. These imaging techniques provide detailed and accurate 3-dimensional visualisation of cardiac structures in real time and may replace fluoroscopy for procedural guidance in the future.

During TAVI, aortic valve crossing, balloon dilatation and positioning and deployment of the prosthesis are the most important procedural steps. Aortic valve calcifications are used as fluoroscopic landmarks during crossing the aortic valve with the guide wire and, subsequently, the dilatation balloon is positioned ( Figure 5 ). TOE enables visualisation of the guidewire through the aortic valve using the short-axis view of the aortic valve (at 30° to 50º) or the long-axis view (110° to 130º). Three-dimensional TOE allows simultaneous visualisation of the long-axis and short-axis view of the aortic valve in real-time ( Figure 5 ). After crossing the aortic valve with the guide wire and positioning the balloon across the aortic valve, balloon dilatation under rapid right ventricular pacing is performed. The opening of the aortic valve and the presence of aortic regurgitation can be immediately evaluated with echocardiography at this stage. Following this step, the delivery catheter with the transcatheter aortic prosthesis is advanced retrograde (transfemoral) or antegrade (transapical) under fluoroscopic and echocardiographic guidance. Severely calcified and stenotic aortic valves may challenge this step and, according to different series, the failure rate of crossing the aortic valve with the delivery catheters ranges from 2.3% to 6% [37]. A combination of fluoroscopy and echocardiography may provide the most accurate approach to guide the prosthesis positioning as previously described [37]. Exact positioning of the transcatheter aortic valve is crucial to avoid potential complications. Unfavourable prosthesis positioning and deployment may lead to prosthesis migration or significant paravalvular leakage. In addition, very low implantation of the prosthesis may interfere with the motion of the anterior mitral leaflet. Deployment of the balloon-expandable SAPIEN XT valve is performed under rapid right ventricular pacing. In contrast, deployment of the Medtronic CoreValve system is performed in 3 sequential phases:

during the first phase, the prosthesis is partially deployed under patient’s native cardiac rhythm;
subsequently the two third lower parts of the frame are deployed and anchored to the left ventricular outflow tract and aortic valve annulus, at these stages, retrieval and repositioning of the prosthesis to optimise the results is still feasible;
the prosthesis is released within the aortic root. Furthermore, TOE is crucial during the procedure in order to assess complications such as severe paravalvular aortic regurgitation, pericardial effusion or aortic dissection.

Videodensitometric quantitative angiography

Quantitative videodensitometric angiographic assessment of aortic regurgitation (QAR) has emerged as a new tool to guide TAVI procedure ( Figure 6 ). This technique relies on time–density curves obtained from the region of interest (left ventricular outflow tract) and the region of reference (aortic root). The relative ratio of the two density curves provides a surrogate of regurgitation fraction expressed in percentage. The QAR is validated in animal [38], in vitro [39, 40], and in clinical settings comparing both transthoracic and transoesophageal echocardiography [41, 42]., Furthermore, videodensitometric QAR has been validated against cardiac magnetic resonance imaging [43]. On the long-term follow-up, a threshold of 17% in AR has been associated with increased mortality [44]. The long-term prognosis and AR improvement after post-balloon dilatation has also been demonstrated with this technique [45].

Although not introduced in routine clinical practice, advances in MRI and computed tomography have permitted the use of these modalities to guide the procedure. Initial in vitro experiences have shown the feasibility of interventional real-time MRI to guide TAVI procedure using current transcatheter valve systems [46, 47]. The development of MRI-compatible and MRI-tracked devices constitutes a step forward in this field allowing procedural guidance and real-time orientation for axial positioning and deployment of the device without need of fluoroscopy or iodinated contrast media. Real-time fast imaging with steady-state free precession (SSFP) sequences are utilised to advance the delivery systems and to position and deploy the prosthesis whereas T1-weighted 3-dimensional fast low-angle shot imaging sequences are acquired to evaluate the procedural results (correct positioning of the prosthesis). Finally, prosthesis haemodynamic can be evaluated with ECG-gated flow-sensitive phase contrast sequences ( Figure 7). Further improvements in MRI-compatible devices providing superior image quality and reducing radiofrequency related heating during MRI data acquisition may help to implement this imaging modality in clinical practice.

Finally, advances in rotational angiography have enabled 3-dimensional reconstructions of the aortic root during the procedure [48, 49]. With the DynaCT technique (Axiom Artis [Siemens Inc., Erlangen, Germany]) the intraoperative 3-dimensional reconstructions are overlaid onto x-ray life images and is a promising tool to guide the positioning and deployment of the prosthesis ( Figure 7 ).

EVALUATION OF TAVI RESULTS: SHORT- AND LONG-TERM FOLLOW-UP

Immediate decrease in transvalvular systolic gradients and left ventricular afterload relief can be observed after transcatheter valve deployment. TOE transgastric views permit accurate measurement of transvalvular gradients. In addition, post-procedural aortic regurgitation can be observed with colour Doppler TOE, from the long-axis view of the aortic valve (110° to 130º) or the transgastric view ( Figure 8 A ). Simultaneous visualisation of orthogonal views of the aortic valve permits accurate location of the leakage (paravalvular or intravalvular). The reported prevalence of mild post-procedural paravalvular or central aortic regurgitation ranges from 58% to 73% [50, 51]. The long-term consequences of mild post-procedural aortic regurgitation are unknown. However, most of the series shows that mild post-procedural aortic regurgitation tends to disappear at long-term follow-up. In contrast, moderate and severe post-procedural regurgitation is less frequent (11.8% to 20.8% of patients). The presence of haemodynamically significant post-procedural aortic regurgitation may indicate the need for re-dilatation of the deployed prosthesis to achieve better apposition of the frame to the aortic valve annulus. Less frequently, an emergency valve-in-valve procedure (1.7% to 4.3% of patients) or conversion to surgical aortic valve replacement (1%) is needed [3, 50].

MDCT has helped to understand the pathophysiological mechanisms underlying post-procedural aortic regurgitation. Severe calcification of the native valve may preclude complete and circular deployment of the prosthesis leading to dysfunction of the prosthetic leaflets or presence of gaps between the prosthetic frame and the aortic wall [52, 53]. In addition, suboptimal positioning of the Medtronic CoreValve is not infrequent (13.8%) and has been related to prosthesis dysfunction and significant post-procedural aortic regurgitation ( Figure 8 [B] ) [50].

At long-term follow-up, evaluation of the prosthesis haemodynamic is commonly performed with transthoracic echocardiography. So far, severe dysfunction of the prosthesis has been reported in a few case reports [54, 55]. Malposition of the prosthesis has been described as the cause of prosthesis dysfunction [54, 55].

MDCT plays an important role in the diagnosis of post TAVI of structural valve deterioration. It helps in the detection of subclinical leaflet thrombosis and leaflet motion abnormality. Ideally, high quality multi-phase MDCT is necessary to assess the leaflet motion. Other complications as contained aortic annular rupture, endocarditis, coronary mal-alignment can be assessed.[56] However, TOE is commonly used to assess leaflet motion abnormalities and morphological abnormalities such as endocarditis and cardiac masses.

FOCUS BOX 1Key points before, during and after TAVI

Before TAVI:

Confirmation of aortic stenosis severity
Clinical evaluation and assessment of the risk of surgery
Aortic valve annular dimensions for evaluation of prosthesis size selection
Peripheral artery anatomy evaluation for planning procedural approach
Evaluation of contraindications: aneurysm of ascending aorta (self-expandable prosthesis), intracavitary thrombus, coronary artery disease not amenable for percutaneous coronary intervention
Echocardiography is the non-invasive imaging technique most frequently used to evaluate candidates for TAVI
MDCT provides the most comprehensive pre procedural planning before TAVI including patient eligibility, device selection, device sizing and vascular access suitability.

During TAVI:

Fluoroscopy, invasive hemodynamic, quantitative aortography and transoesophageal echocardiography are complementary tools used for procedural guidance
The minimalist TAVI approach using fluoroscopy without TOE/general anaesthesia is widely used as the standard approach in many experienced high volume centers.
Aortic valve crossing, balloon dilatation and positioning and deployment of the prosthesis are the key procedural steps
Videodensitometric quantitative aortography provides accurate estimation of PVL grade and can guide the need for corrective manoeuvres for treating significant post-TAVI PVL including balloon post dilatation.

After TAVI:

Confirmation of position and function of the prosthesis
Echocardiography is the preferred method to evaluate presence and severity of paravalvular leakage
MRI 2D flow phase contrast or 4D flow could be used for accurate quantification of residual post TAVI aortic regurgitation.
MDCT is used for detection of reduced leaflet motion and subclinical leaflet thrombosis.
Evaluation of complications: pericardial effusion, detection of new left ventricular wall motion abnormalities that may indicate occlusion of coronary ostia, stroke, vascular complications

Transcatheter mitral valve procedures

MITRAL STENOSIS

View chapter "Percutaneous balloon mitral commissurotomy"

Although the prevalence of rheumatic disease is significantly reduced in industrialised countries, mitral stenosis still accounts for approximately 10% of valvular heart disease worldwide and is associated with relatively high morbidity and mortality [57]. Since its introduction by Inoue in 1984, percutaneous balloon mitral commissurotomy (PMC) is the first-line treatment in patients with symptomatic severe mitral stenosis [16]. However, this intervention should be performed only in patients with severe mitral stenosis (valve area 1.5 cm²), favourable anatomical and/or clinical characteristics and without specific contraindications [16]. According to the recent 2021 ESC/EACTS Guidelines for the management of valvular heart disease, PMC should be considered in asymptomatic patients without unfavourable clinical and anatomical characteristics for PMC and high thromboembolic risk (history of systemic embolism, dense spontaneous contrast in the LA, new-onset or paroxysmal AF), and/or High risk of haemodynamic decompensation (systolic pulmonary pressure >50mmHg at rest, need for major non-cardiac surgery, desire for pregnancy) [13]. Non-invasive imaging plays a central role in patient selection process, procedural guidance, and confirmation of the results.

Patient selection for percutaneous mitral balloon valvotomy

The assessment of mitral stenosis severity is crucial before referring a patient for percutaneous mitral balloon valvotomy. For this purpose, transthoracic echocardiography is currently considered the technique of choice, using direct valve planimetry, the pressure half-time method and the transvalvular gradient [16]. Next, evaluation of mitral valve morphology is also extremely important for selection of candidates for this procedure. Echocardiographic scores (Wilkins’ score and Cormier’s grading) based on valve (and sub-valvular apparatus) mobility, thickening and calcifications, have been developed to predict the feasibility and the results of percutaneous mitral balloon valvotomy [16]. ( Table 2 ) summarises the parameters that are relevant before percutaneous mitral balloon valvotomy. A Wilkins’ score >8 or a Cormier’s grade 3 and severe tricuspid regurgitation predict a less favourable percutaneous mitral balloon valvotomy outcome [58]. Importantly, the degree and nature (calcified and non-calcified) of commissural fusion is not assessed by these traditional echocardiographic scores and should be included in any preprocedural assessment. Other parameters that have been related to less favourable outcome include the haemodynamic consequences of mitral stenosis (left atrial dilatation, pulmonary hypertension) and concomitant valvular heart diseases. Transthoracic echocardiography permits comprehensive evaluation of all these parameters. TOE is crucial to exclude left atrial thrombosis, which is considered the main contraindication for percutaneous mitral balloon valvotomy.

Recently, real-time 3-dimensional echocardiography has been proposed to accurately measure the anatomic mitral valve area. Appropriate alignment of the multiplanar reformation planes provides the most accurate cross-sectional plane through the smallest orifice area ( Figure 9) [59]. Compared with 2-dimensional echocardiographic planimetry and Doppler-derived mitral valve areas, real-time 3-dimensional echocardiography showed the best agreement (r = 0.9) with invasive measurements (using the Gorlin formula) and lower intra-observer and inter-observer variability [59]. In addition, this technique provides unique views of the stenotic valve and is therefore highly suitable for an accurate assessment of valve morphology.

Procedural guidance and long-term follow-up evaluation

Two-dimensional or 3-dimensional TOE is extremely useful to guide the different steps of percutaneous mitral balloon valvotomy, such as trans-septal puncture and balloon positioning within the mitral valve. In addition, TOE is crucial for the immediate evaluation of procedural results, assessing the mitral valve area, transmitral gradients and the degree of commissural opening. Recently, in a series of 1,024 consecutive patients treated with percutaneous mitral balloon valvotomy, the post-procedural mitral valve area and the degree of commissural opening were predictors of good long-term functional results [60]. Furthermore, TOE permits the timely detection of potential procedural complications such as severe mitral regurgitation and cardiac perforation and subsequent cardiac tamponade.

Echocardiographic serial follow-up of asymptomatic patients with clinically significant MS is recommended yearly, and at (2_3 years) in patients with moderate stenosis. Finally, echocardiographic follow-up after successful PMC should be performed regularly similar to that of asymptomatic patients in order to exclude the presence of restenosis (15% rate at 5 years) or development of mitral regurgitation [61], and should be more frequent if asymptomatic restenosis occurs.

Degenerative mitral stenosis with mitral annular calcification (MAC)

MAC is a common finding in elderly patients with an estimated prevalence of 40% in comparison to 9-15% in general population. MAC is different entity from rheumatic mitral stenosis, which can cause mitral stenosis, mitral regurgitation or both. It is associated with poor prognosis due to severe comorbidities and high-risk profile. Mitral valve hemodynamic assessment is a challenge in the presence of MAC. Echocardiography assessment is limited as less reliable planimetry due to irregular mitral valve orifice and irregular calcifications while transmitral gradient has shown prognostic value. MDCT is necessary before any intervention for evaluation of location and degree of calcification and for proper procedural planning. [62]

Guerrero et al. reported the feasibility of transcatheter mitral valve replacement (TMVR) with balloon expandable valves in patients with severe degenerative mitral stenosis with high 30 day and 1-year mortality [63] One of potential but serious complication of TVMR is the LVOT obstruction (LVOTO) due to anatomical constrains within the mitral-aortic region. Therefore, it is important to select patients for TMVR without risk or with minimal risk of LVOTO. MDCT provides accurate measurements of projected neo-left ventricular outflow tract (neo-LVOT) area, mitral annular dimensions (perimeter and inter-trigonal, inter-commissural and septolateral distances) with qualitative and quantitative assessment of calcifications [64] Multiphase MDCT may play a role in neo-LVOT assessment to predict LVOT obstruction (LVOTO) with TMVR using early systolic instead of end-systolic phase. Using this approach can significantly increase TMVR eligibility in previously screen-failed patients because of perceived risk of LVOTO [65]

MITRAL REGURGITATION

View chapter "Transcatheter mitral valve repair"

In the last decade, technical advances in percutaneous interventions have provided feasible therapeutic alternatives to conventional surgery for patients with severe mitral regurgitation and high operative risk ( Table 3 ). These procedures aim to correct one of the main determinants of mitral regurgitation, such as annulus dilatation or leaflet abnormalities. Percutaneous mitral valve interventions includes: Transcatheter edge-to-edge leaflet repair (TEER) procedures,(coronary sinus) annuloplasty procedures and TMVR. In addition, alternative approaches, such as left ventricular or left atrium direct remodelling, are in development and limited clinical data are currently available.

Non-invasive imaging for procedure selection

Non-invasive imaging, and particularly echocardiography, is essential to assess the severity of mitral regurgitation and therefore to refer the patient for surgical or percutaneous treatment. For this purpose, current guidelines recommend applying a multi-parametric Doppler-echocardiographic approach that includes estimation of the amount of mitral regurgitation (measurement of colour-Doppler jet area, vena contracta width, regurgitant volume and effective regurgitant orifice area calculated by proximal isovelocity surface area method or quantitative pulsed-wave Doppler) together with the haemodynamic consequences such as left ventricular dilatation and dysfunction, left atrial dilatation or increased pulmonary pressures ( Figure 10 ) [16].

Recently, colour-Doppler 3-dimensional echocardiography has also become available and has been proposed as a new method to grade mitral regurgitation severity. This technique, allowing for an unlimited plane orientation and in particular for an “en face” view of the mitral valve, provides a direct assessment of size and shape of the effective regurgitant orifice area

( Figure 10 ). This overcomes the inaccuracies of 2-dimensional echocardiographic measurements of the effective regurgitant orifice area that assume a hemispheric shape of the flow convergence. Several studies showed the improved accuracy of 3-dimensional over a conventional 2-dimensional approach, particularly in functional mitral regurgitation, which is most frequently characterised by an elliptical rather than a circular regurgitant orifice [66, 67]. Although not implemented in routine clinical practice, velocity-encoded MRI has also been applied for transmitral flow quantification and provides an accurate assessment of mitral regurgitation severity ( Figure 10 ) [68].

Specifically, 3-dimensional 3-directional acquisition with retrospective valve tracking appears superior to conventional 2-dimensional one-directional acquisition, being able to cover the complete velocity vector field of the blood flow and to correct for the through-plane myocardial motion in the apical-basal direction [69, 70].

Once the severity of mitral regurgitation has been assessed, selection of the most appropriate mitral percutaneous procedure requires an accurate characterisation of the underlying lesion that leads to mitral leaflet coaptation failure and, in particular, differentiation between primary and secondary (functional) mitral regurgitation. In primary mitral regurgitation, one or more components of mitral valvular and sub-valvular apparatus are structurally abnormal. By contrast, in secondary mitral regurgitation the valve is structurally normal but the presence of global and/or regional left ventricular dilatation and dysfunction leads to papillary muscles displacement and mitral annulus dilatation, increasing valve tethering forces and resulting in leaflet coaptation failure. Consequently, non-invasive imaging plays an important role in procedural selection, providing crucial anatomical and functional details of the mitral valve apparatus, left ventricle and left atrium, together with other specific information related to the technical features of each percutaneous mitral valve procedure.

Transcatheter edge to edge leaflet repair (TEER) (double-orifice repair)

Percutaneous leaflet repair using the MitraClip® device (Abbott Vascular, Structural Heart, Menlo Park, CA, USA) improves mitral valve coaptation by opposing the central scallops of the anterior and posterior mitral leaflets with a mechanical clip, creating a double-orifice valve opening in a “bow-tie” configuration. Feasibility, safety and efficacy of this procedure have been demonstrated in the EVEREST I and in the EVEREST II trials [71], which included patients with both primary and functional mitral regurgitation and applying specific anatomical inclusion criteria. In particular, only patients with severe mitral regurgitation and a regurgitant jet originating from the central two thirds of the coaptation line were selected. Furthermore, in patients with functional mitral regurgitation, leaflet coaptation length and depth must have been at least 2 mm and ≤11 mm, respectively. In the presence of leaflet flail, the flail gap and width must have been <10 mm and <15 mm, respectively. Therefore, 2-dimensional TOE is crucial to assess these key anatomical features [72]. However, 3-dimensional TOE is more accurate in the evaluation of procedure feasibility, providing unique visualisation of the valve abnormalities (including leaflets, commissures and subvalvular apparatus) and 3-dimensional quantification tools [G14] [73]. Novel dedicated software is currently available for analysis and quantification of mitral valve geometry in 3 dimensions, providing accurate information on mitral annulus size, leaflet coaptation length and depth, and leaflet surface areas, which are important parameters for procedural planning ( Figure 11 ).

3D transesophageal echocardiography is more accurate than 2D echocardiography for defining the underlying mechanism of primary mitral regurgitation.

Recently, the MITRA-FR and COAPT randomized clinical trials have evaluated the safety and efficacy of MitraClip in patients with symptomatic heart failure and persistent severe secondary mitral regurgitation despite guidelines directed medical therapy (GDMT), who were ineligible or not appropriate for surgical repair by the Heart Team. Both trials indicate that MitralClip is safe and effectively reduces MR up to 3 years. But there was no impact on the primary endpoint of all-cause mortality or heart failure hospitalization at one and two years compared to GDMT alone in the MITRA-FR trial. On the other hand, MitraClip reduced the primary endpoint of cumulative hospitalizations for heart failure, in addition to several pre-specified secondary endpoints, including two years all-cause mortality in the COAPT trial. [74, 75, 76, 77]

A 3-dimensional analysis and quantification of mitral valve geometry can also be provided by MDCT. The high spatial resolution of this imaging technique permits accurate visualisation of the mitral valve complex including the mitral valve annulus, leaflets, left atrium and ventricle, together with an accurate analysis of the left ventricular geometry [78].

The Edwards PASCAL transcatheter mitral valve repair (TMVr) system (Edwards Lifesciences, Irvine, CA, USA) consists of a central spacer that is designed to fill the regurgitant orifice area and with paddles that are intended to maximise coaptation and reduce stress on the native leaflets. It has also clasps that allow for independent leaflet capture and offer the possibility to finetune leaflet positioning. In patients with grade 3+ or 4+ MR, the feasibility of PASCAL implant was first reported in 2017 with 96% technical success and increased reduction in severity of MR [79], , PASCAL repair system showed feasibility and acceptable safety, severity of MR, irrespective of etiology was significantly lower and with significant improvements in exercise capacity, functional status, and quality of life [80]. Typically, 2D and 3D TTE and TEE are used in periprocedural guidance of PASCAL repair similar to Mitral Clip procedure.

Coronary sinus annuloplasty

This percutaneous mitral intervention is specifically intended for the treatment of functional mitral regurgitation. The proximity of the coronary sinus to the mitral annulus has inspired the development of several devices that, after implantation within the coronary sinus, constrain the mitral annulus and reduce the mitral annular circumference improving mitral leaflet coaptation similarly to the surgical restrictive annuloplasty. The CARILLON® device (Cardiac Dimensions Inc., Kirkland, WA, USA) is a steel adjustable wire connected to distal and proximal stents, which are also positioned in the coronary sinus. The feasibility of these techniques relies on the anatomical relationship between the posterior mitral annulus and the coronary sinus. In addition, the spatial relationship between the coronary sinus and the circumflex coronary artery is an important determinant of the procedural feasibility. MDCT can accurately indicate the exact location of the coronary sinus relative to the mitral valve annulus and to the circumflex coronary artery ( Figure 12 ). In a recent series of 105 patients, including 34 patients with advanced heart failure and/or severe mitral regurgitation, MDCT showed that in the majority of patients the coronary sinus was located above the mitral annulus potentially limiting the efficacy of percutaneous annuloplasty procedures [81]. Furthermore, in 68% of patients the circumflex coronary artery coursed between the coronary sinus and the mitral annulus, implying a high risk of myocardial ischaemia due to coronary artery compression by the distal anchor of the percutaneous device. The feasibility of these procedures might also be reduced in the presence of a heavily calcified mitral annulus, which can be better assessed with MDCT.

Cardiac MRI is complimentary to echocardiography in assessment of MR, it provides accurate quantification of MR volume by the calculating the difference between left ventricular stroke volume and the aortic forward flow. It has also incremental for timing of intervention as it provides the precise change in ventricular volumes and function. Tissue characterisation is a unique feature which assess the degree of ischemia and predict the MR improvement after revascularisation.

Procedural guidance and follow-up evaluation

Non-invasive imaging plays an important role in addition to fluoroscopy for the guidance of these sophisticated procedures. In particular, during the MitraClip® leaflet repair or the PASCAL valve repair^TM, 2-dimensional and 3-dimensional TOE are invaluable imaging techniques to guide the trans-septal puncture and the positioning of the clip perpendicularly to the leaflet coaptation line and at the level of the regurgitant jet origin [72]. The mid-oesophageal short-axis view of the aortic valve is commonly used both to evaluate the distance between the aorta and tenting of the atrial septum prior to trans-septal puncture, and to guide the procedure itself. Other transoesophageal echocardiographic views of interest include the mid-oesophageal commissural or “2-chamber (60° to 90°)” view to assess medial-lateral orientation of the device, mid-oesophageal long-axis view or “left ventricular outflow tract (120° to 150°) view” to assess anterior-posterior orientation of the device and perpendicularity of the device to the mitral annulus, and transgastric short-axis view at the mitral valve level (0° to 30°) to assess the perpendicularity of the clip arms to the coaptation line and adequate insertion of leaflets in the clip. ( Figure 13 and Figure 14, Video 1 A-G) summarises the sequential procedural steps during MitraClip® leaflet repair.

During coronary sinus annuloplasty, fluoroscopy remains the mainstay imaging technique to guide the procedure. Cannulation of the coronary sinus, device implantation and confirmation of circumflex coronary artery patency are all guided with fluoroscopy.

A reduction in MR is confirmed with TOE. In this field, fusion imaging with MRI-derived roadmaps superimposed onto live x-ray may provide more detailed procedural guidance ( Figure 15 ) [82]. These techniques, however, are currently under investigation and further studies are needed before implementation in current clinical practice.

Echocardiography is fundamental for the assessment of the immediate results of the procedure, confirming a significant reduction of MR with a double-orifice mitral valve opening after leaflet repair procedures, and a decrease in mitral annulus dimension after coronary sinus annuloplasty.

Furthermore, the efficacy of these procedures can be evaluated at follow-up with echocardiography, by showing a significant and sustained mitral regurgitation reduction, left ventricular and atrial reverse remodelling, improvement in left ventricular systolic function and reduction in pulmonary artery pressures.

FOCUS BOX 2Transcatheter mitral valve procedures

Mitral valve stenosis

−Echocardiography is the method of choice to assess mitral valve area (≤1.5 cm2), leaflet mobility, calcification, and commissural fusion and subvalvular apparatus

−A Wilkins’ score >8 or a Cormier’s grade of >2 and severe tricuspid regurgitation predict a less favourable percutaneous mitral balloon valvotomy outcome

−During the procedure, TTE is the standard method, a novel 3-dimensional TOE method allows accurate guidance and assessment of the procedural results
Mitral valve regurgitation. Key procedural steps for transcatheter mitral valve repair techniques:

−Leaflet repair techniques (MitraClip®): Key anatomical inclusion criteria:
- Regurgitant orifice associated to A2-P2 levels of the mitral valve
- Flail gap <10 mm and flail width <15 mm
- Coaptation length ≥2 mm and depth <11 mm (for functional mitral regurgitation)
Procedural guidance and evaluation of the results:
- Transseptal puncture
- Axial alignment of the device directed towards the regurgitant orifice
- Alignment of the device perpendicular to the line of coaptation
- Leaflet grasping and capture
- Evaluation of mitral regurgitation reduction
−Indirect mitral annuloplasty (CARILLONTM): Key anatomical inclusion criteria:
- Functional mitral regurgitation as assessed with echocardiography
- Appropriate dimensions and course of the coronary sinus and spatial relationship of the coronary sinus with the circumflex coronary artery evaluated with MDCT
− Indirect mitral annuloplasty (CARILLONTM): Procedural guidance:
- Fluoroscopy to cannulate the coronary sinus is helpful
- Monitoring of the patency of the circumflex coronary artery with invasive angiography

PULMONARY VALVE DISEASE

View chapter "Percutaneous pulmonary valvuloplasty"

View chapter "Percutaneous pulmonary valve implantation"

Corrective surgery of congenital heart disease frequently involves repair and reconstruction of the right ventricular outflow tract. The lifespan of the prosthetic conduits used in these techniques is limited and at follow-up, pulmonary regurgitation or homograft conduit obstruction are frequently observed. Balloon dilatation and stent implantation have been effective transcatheter therapies for stenosis relief. However, pulmonary regurgitation has challenged the development of transcatheter therapies. In the past, pulmonary regurgitation after surgical repair of congenital heart disease was considered clinically not indicated and patients were managed conservatively for many years before referral for surgery. Recent evidence, however, has shown that severe pulmonary regurgitation leads to right and left ventricular dysfunction, symptomatic heart failure and increased risk of sudden death [83, 84].

Following the first-in-man transcatheter pulmonary valve implantation (TPVI) experience reported by Bonhoeffer et al in 2000 [85], several developments in prosthesis and delivery system design have provided a feasible alternative to surgery for patients with post-operative right ventricular outflow tract dysfunction, pulmonary regurgitation, stenosis, or both [86]. The Melody® device (Medtronic Inc., Minneapolis, MN, USA) provides the most extensive experience and consists of a bovine jugular vein valve sutured within a platinum iridium stent. The use of this device is approved for placement in dysfunctional right ventricular outflow tract conduits. It is available in three different sizes: 18, 20 and 22 mm, for right ventricular outflow tract diameter (RVOT) <22 mm and conduits diameter >16 mm at surgical insertion. The Edwards Sapien transcatheter heart valve (Edwards Lifesciences, Irvine, California) is now approved for TPVI [87]. It is available in different sizes: 20, 23, 26 and 29 mm for RVOT conduit landing zone diameter 16.5 – 20mm, 20 – 23mm, 23.0 – 26mm, 26 – 29mm respectively, which allows TPVI in some patients with a large native or patched RVOT. The morphology and size of the right ventricular outflow tract, main pulmonary trunk and its branches are the main determinants of the procedural feasibility. Previously, invasive angiography was used for assessment of right ventricular outflow diameter[86].

Echocardiography and MRI are the mainstay non-invasive imaging modalities to evaluate the patients before transcatheter pulmonary valve implantation. Echocardiographic evaluation includes estimation of right ventricular systolic pressure from the tricuspid regurgitation flow, evaluation of significant stenosis at the right ventricular outflow tract by measuring the systolic gradient with continuous wave Doppler and assessment of pulmonary regurgitation severity using colour-Doppler echocardiography. MRI provides accurate and detailed information on right ventricular volumes and function and right ventricular outflow tract morphology. In particular, the homografts and conduits of the reconstructed right ventricular outflow tract may display complex geometries that are better imaged with gadolinium contrast-enhanced MRI rather than echocardiography or angiography. Recently, 4-dimensional contrast-enhanced computed tomography has been used to obtain 3-dimensional volumes of the right ventricular outflow tract, pulmonary trunk and proximal branch pulmonary arteries and evaluate their deformation along the cardiac cycle [88]. Based on these reconstructions, a finite element model and prototype polymer models of these structures were created ( Figure 16 ). This novel analysis provides accurate information to select the most appropriate prosthesis size and to plan the interventional strategy. During implantation of the percutaneous valve, fluoroscopy and echocardiography are the most important imaging modalities to guide the procedure. The risk of coronary compression should be evaluated during implantation of a transcatheter pulmonary valve in the right ventricular outflow tract; especially as anomalous coronary arterial anatomy is rather frequent in this group of patients. However, even in patients with “normal” origin of the coronary arteries, implantation of the transcatheter pulmonary valve within the right ventricular outflow tract conduit may cause tissue displacement and increase the risk of coronary artery compression [86]. CMR is the chosen modality for primary assessment and follow-up of candidates for PPVI, while MDCT is helpful in cases with previous stent in situ or redo PPVI. [89]

At follow-up, transcatheter pulmonary valve haemodynamics and right ventricular volumes and function are routinely evaluated with echocardiography or MRI. In addition, late valve-related complications such as stent fracture should be ruled out. Specifically, stent fracture is a relatively common finding that can be detected by recurrent or new obstruction of the right ventricular outflow tract as assessed with echocardiography. Implantation of a new valve (valve-in-valve procedure) may resolve this complication.

FOCUS BOX 3Pulmonary valve disease

Before transcatheter pulmonary valve implantation:

−Echocardiography and MRI are the mainstay non-invasive imaging modalities to evaluate the patients before transcatheter pulmonary valve implantation

−Four-dimensional contrast-enhanced computed tomography has been used to obtain 3-dimensional volumes of the right ventricular outflow tract, pulmonary trunk and proximal branch pulmonary arteries and evaluate their deformation along the cardiac cycle

−Based on angiography, unfavourable outflow tract morphologies include right ventricular outflow tract diameter > 22 mm and conduits diameter <16 mm at surgical insertion

During the procedure:

−Risk of coronary compression should be evaluated during implantation of a transcatheter pulmonary valve in the right ventricular outflow tract

After the procedure:

−Transcatheter pulmonary valve haemodynamics and right ventricular volumes and function are routinely evaluated with echocardiography or MRI

−Stent fracture is a relatively common finding that can be detected by recurrent or new obstruction of the right ventricular outflow tract as assessed with echocardiography

TRICUSPID REGURGITATION

Several transcatheter tricuspid valve interventions (TTVI) have been developed for treating tricuspid regurgitation (TR), which offer less invasive transcatheter therapy for more high-risk patients. Similar to mitral repair techniques, TTVI repair techniques includes leaflet repair techniques such as leaflet edge-to-edge repair or annuloplasty or combination of both. List of available TTVI devices and role of imaging are summarised in Table 4.

Echocardiography is essential for pre-TTVI assessment, device selection, procedural guidance, post-TTVI follow up ( Figure 17, Video 2 A-H ). Recent European and American guidelines did not specify the role of Transthoracic Echocardiography (TTE) in TTVI. However, many published documents have outlined the use of TTE in TTVI.TTE is the ideal imaging technique for screening and procedural guidance of patients referred for TTVI. Furthermore, TTE is used for determination of procedural success and for long-term follow-up of patients after TTVI [90, 91, 92].

MDCT is crucial for procedure planning including assessment of tricuspid annulus (TA), sub valvular apparatus, tricuspid leaflets tethering area and height, right atrium and ventricle function and volumes, coronary anatomy in relation to tricuspid annulus and anatomy of femoral veins and venae cavae. Protocolized acquisition is necessary for MDCT imaging of the right heart and TV. Heart rate control, multi-phase ECG-gated acquisition using triphasic contrast protocol with specified contrast volume and injection rate is a key to avoid streak and motion artifacts. Newer generation MDCT scanners with larger z-axis coverage are better used due to less radiation, less contrast and short acquisition time, it is also more beneficial in case with atrial arrhythmias. In patients with implantable cardiac defibrillators or resynchronization therapy devices who may not be candidates to cardiac MRI, MDCT can provide accurate function and volumes of RA and RV.

Cardiac MRI is more helpful in patient with poor echo window, it overcomes echocardiography limitation in imaging of TV and RV without non-ionized radiation. It provides accurate quantification of TR volume, RV/RA function and volumes. In addition, cardiac MRI provides full regional wall motion analysis and myocardial tissue characterization . [93]

FOCUS BOX 3Tricuspid regurgitation

TOE is used for periprocedural assessment of TR severity, aetiology, and eligibility for the selected transcatheter repair approach. TR severity is graded into mild, moderate, and severe following recent EACVI and ASE guidelines.
For all devices:
- Severe TR should be confirmed using integrated approach (mean VC width >7 mm, EROA >40 mm2, RV >45 ml)[13].
For edge-to-edge devices repair devices:
- Confirm that TR etiology is: functional (secondary) with normal leaflets or TR is primary with valve prolapse.
- Measure leaflets: Coaptation depth <10 mm, Coaptation gap <7.2 mm (ideally <4.0 mm), Leaflet length >10 mm
- Location of main TR jet: Central or antero-septal
For leaflet coaptation repair devices:
- Coaptation depth <10 mm
  - Coaptation gap <18 mm
For restrictive annuloplasty devices:
- Measure the TV annulus: Adequate TA dimensions (e.g., TA diameter ≤55 mm and ≥2–4 mm posterior annular depth required for Trialign implantation)
- After final deployment of the device, TOE is used for the assessment of TV repair success and complications ( Figure 17 ).
MDCT has emerged as a complimentary imaging modality for TTVI:
- Specific acquisition/contrast protocol is necessary.
- MDCT can assess 3D anatomy of RV and tricuspid annulus
- RV and RA function and volumes can be obtained from multi-phase MDCT.
- Right coronary distance form TA is important to prevent injury during annuloplasty repair.
- MDCT is used for prediction of optimum fluoroscopy angle for procedure planning.
- MDCT can assess anatomical TR orifice area, tricuspid leaflet tethering area and height.
CMR overcomes echocardiography limitations:
- Reproducible and precise calculation of RV function and
- Regional wall motion analysis in any plane.
- Quantification of TR volume direct or indirect methods.
- Myocardial tissue
- Etiology of TR.

Prosthetic paravalvular leakage closure and valve-in-valve procedures

View chapter "Percutaneous closure of paravalvular leaks"

Repeat surgical procedures for failed surgical valve repair or replacement carry significant morbidity and mortality operative risks. Prosthetic valve dehiscence or degenerated bioprosthesis are not infrequent complications of valve repair/replacement surgeries and may lead to heart failure symptoms and haemolysis. In recent years, advances in intracardiac catheter based interventions have provided feasible alternative therapies to conventional surgery. Percutaneous closure of paravalvular leaks and valve-in-valve implantation procedures offer a less invasive alternative [94, 95]. In these procedures, combination of fluoroscopy and 3-dimensional imaging techniques is crucial to achieve the highest procedural success rate.

PERCUTANEOUS PARAVALVULAR LEAKAGE CLOSURE

Three-dimensional TOE enables accurate evaluation of the location, size and shape of the dehiscence to select the most appropriate occluder device. The 3-dimensional zoom mode provides “en face” views of the defect and the prosthetic valve or valvular ring, not available with other imaging modalities so far [96]. Recently, 4-dimensional reconstructions from MDCT data provide detailed characterisation of the location, size and shape of the defect with high spatial resolution ( Figure 18 ). During the procedure, 3-dimensional TOE permits visualisation of the entire length of the catheters and accurate localisation through the paravalvular dehiscence. In addition, initial experiences using 4-dimensional computed tomography angiography integrated with live x-ray have shown highly accurate guidance of the procedure with exact localisation of the catheters relative to the paravalvular dehiscence and the prosthetic valve.

VALVE-IN-VALVE (ViV) PROCEDURES

The feasibility of valve-in-valve technique to treat degenerated aortic or mitral bioprostheses has been demonstrated in several series and the recent Global Valve-in-Valve Registry [97] Recently, ViV TAVR showed favourable long-term outcomes for failed bioprosthetic aortic valve[98]. Mitral ViV using the SAPIEN 3 transcatheter heart valve was associated with increased technical success, reduced mortality at 30 days and at 1 year[99]. In this subgroup of patients, multimodality imaging is crucial for procedure planning and device selection. Exact measurement of the prosthesis dimensions and relationship with surrounding structures are crucial.

Three-dimensional TOE and MDCT are the chosen imaging modality for diagnosis of valve dysfunction and procedural planning.. 2-Dimensional or 3-dimensional TOE may be of value to complement fluoroscopy and guide the procedure. ( Figure 19 and Figure 20 ) summarises two different valve-in-valve procedures within a mitral bioprosthesis and within a failed bioprosthetic aortic valve.

FOCUS BOX 5Percutaneous closure of paravalvular leakage and valve-in-valve procedures

Planning the procedure:

−Three-dimensional TOE provides an accurate assessment of paravalvular leakage (location and dimensions of paravalvular dehiscence)

−MDCT permits the evaluation of dimensions, calcification and spatial relationships of the xenograft and surrounding structures (i.e. coronary ostia in aortic xenografts)

During the procedure:

−Fluoroscopy and TOE are crucial for optimal procedural guidance

After the procedure:
TOE will provide the most accurate evaluation of procedural results: resolution of paravalvular leakage

Atrial septal defect closure

View chapter "Atrial septal defect and patent foramen ovale closure"

Atrial septal defect (ASD) is the most frequent congenital heart disease treated with transcatheter-based interventions. Abnormal development of the interatrial septum at different stages of embryogenesis leads to different types and locations of ASD ( Figure 21 A ) [100].

ostium secundum: the most frequent type of ASD (60%). This defect is located at the area of the fossa ovalis or middle area of the atrial septum.
ostium primum: the lower part of the atrial septum is involved in this uncommon defect (15% of adults). Defects of the inlet part of the interventricular septum or atrioventricular valve abnormalities usually coexist with this defect.
sinus venosus: this defect accounts for 10% of ASDs and is located at the superior and posterior septum, in the vicinity of the junction of the superior vena cava. Abnormalities of pulmonary venous drainage are commonly associated.
coronary sinus: this extremely rare defect is located at the roof of the coronary sinus.

The majority of secundum ASDs (80%) can be treated percutaneously [100]. In contrast, sinus venosus, coronary sinus or primum defects are exclusively treated with surgery. Accurate evaluation of the morphology, location and haemodynamic consequences of the ASD determines the clinical decision making of these patients. Transthoracic echocardiography and TOE are the imaging techniques of choice to evaluate these aspects. In addition, MRI is a valuable tool to select the patients and plan the most appropriate therapeutic approach. During the intervention, TOE and intracardiac echocardiography provide additional information to fluoroscopy and permit evaluation of the immediate procedural results. Finally, echocardiography provides accurate information on the presence of residual interatrial shunt or occurrence of complications (erosion of the atrial or aortic wall, device migration).

SELECTING PATIENTS AND PLANNING PERCUTANEOUS CLOSURE STRATEGY

Percutaneous transcatheter closure of secundum ASDs is indicated for haemodynamically significant left-to-right shunts (ratio of pulmonary blood flow to aortic blood flow (Qp/Qs) >1.5), with right atrial or right ventricular enlargement with or without symptoms [100]. The development of symptoms frequently occur in the third decade of life, and closure of ASDs is usually indicated to prevent long-term complications such as pulmonary hypertension, severe tricuspid regurgitation, heart failure, right-to-left shunt and embolism and atrial arrhythmias [100].

Diagnosis of ASDs relies mainly on echocardiography. From the various acoustic windows, 2-dimensional transthoracic echocardiography permits accurate diagnosis of ASD type. With colour-Doppler echocardiography, the direction of the shunt can be identified ( Figure 21 B ). In addition, registration of the pulmonary and aortic flow with pulsed-wave Doppler echocardiography permits quantification of pulmonary and systemic stroke volumes and the shunt fraction. The atrial septum should be also imaged from the orifice of the superior vena cava to the orifice of the inferior vena cava to detect large secundum ASDs and sinus venosus defects. TOE provides improved image quality and permits accurate assessment of the dimensions, morphology and location of the ASD (particularly the sinus venosus type) and dimensions of the rims. Moreover, the measurement of the diameters of the defect and the dimensions of the rims is crucial to plan the procedural strategy ( Figure 21 C ). ASDs larger than 36 mm to 40 mm are preferably treated with surgery. In addition, a deficient inferior rim, inferior-posterior rim, postero-superior rim, coronary sinus rim or deficient rim toward the pulmonary veins (<5 mm) constitute contraindications for percutaneous closure of secundum ASDs. In contrast, a deficient anterior-superior rim (<5 mm) does not represent an absolute contraindication for transcatheter-based therapy. Furthermore, 4.5% of patients with secundum ASD show multiple defects that may require multiple closure devices. The advent of 3-dimensional TOE has enabled the visualisation of an “en face” view of the atrial septum from the right or left atrium. The wide-angle 3-dimensional zoom views, particularly, permit real-time visualisation of the entire interatrial septum and evaluation of the spatial relationships with other cardiac structures (aorta, atrioventricular plane, coronary sinus and inferior and superior vena cava) [101]. In addition, off-line reconstruction of full-volume or wide-angle 3-dimensional zoom views permit precise alignment of the multiplanar reformation planes, providing accurate measurement of the dimensions of the defect and the rims ( Figure 21 ). A recent series of 48 consecutive patients treated with transcatheter closure of secundum ASDs assessed the accuracy of 3-dimensional TOE to identify and characterise the defect compared to 2-dimensional TOE [102]. Optimal visualisation of the secundum ASD was feasible in 96% of patients with 3-dimensional TOE. Dropouts in the region of the fossa ovalis are the main limitations of this imaging technique and need careful adjustment of gain settings. In addition, the inferior rim may not be properly visualised.

Finally, MDCT and MRI are 3-dimensional imaging techniques that permit detection of ASDs [103, 104]. The high spatial resolution of MDCT images permits accurate characterisation of the ASD, evaluation of the spatial relationships with surrounding structures and detection of concomitant congenital abnormalities. However, this technique does not permit direct haemodynamic quantification of the shunt. By contrast, velocity-encoded MRI permits “en face” visualisation of the defect and assessment of the haemodynamic severity with direct quantification of the total flow across the defect ( Figure 22 ) [104]. In 44 patients referred for transcatheter or surgical closure of secundum ASD, “en face” velocity-encoded MRI was performed. Assessment of ASD and rim dimensions with MRI permitted highly accurate selection of the closure device size. In addition, quantification of ASD flow with direct “en face” velocity-encoded MRI showed a good agreement with invasive oxymetry (r=0.80, 95% limits of agreement ±3.9 L/min). More importantly, the detection of multiple septal defects, insufficient rim tissue and sinus venosus defect with anomalous drainage of the pulmonary vein with this imaging modality modified the treatment strategy in 20% of patients [104].

NON-INVASIVE IMAGING DURING TRANSCATHETER CLOSURE PROCEDURE

Intra-procedural echocardiography is essential to ensure accurate sizing and optimal positioning of the device before final release. Most of the centres combine fluoroscopy and echocardiography for procedural guidance in order to reduce the radiation time exposure. Two-dimensional TOE is the most commonly used imaging technique to guide the procedure.

The advent of phase-array intracardiac echocardiography catheters has increased the use of this imaging modality during secundum ASD closure [105]. Compared to rotational intracardiac echocardiography catheters, phase-array catheters are steerable and permit data acquisition at a higher frequency range and greater depth of field. In addition, Doppler and colour flow data can be acquired. Finally, intracardiac echocardiography does not require general anaesthesia and can be performed by the interventionist. However, this echocardiographic modality has some limitations such as its invasive nature and the high cost In addition, if intracardiac echocardiography is used for procedural guidance, preprocedural TOE is of help to accurately and comprehensively assess the morphology and number of defects. Finally, wide-angle 3-dimensional zoom images acquired with 3-dimensional TOE permit procedural guidance in real-time with accurate visualisation of the catheters in relation to the ASD and the surrounding cardiac structures ( Figure 23 ). The key steps during transcatheter ASD closure include: sizing of the defect and measurement of the rims, crossing the defect with the delivery device, positioning of the device across the septal defect and release of the device [106]. The maximum diameter of the septal defect is commonly measured with echocardiography or sizing balloons to subsequently select the most appropriate occluder device size. Thereafter, the device is mounted onto the delivery system and advanced across the defect. The left atrial disk is then deployed and pulled back in order to ensure good apposition of the left-side disk to the surrounding rims. Subsequently, the right-side disk is deployed to seal the atrial defect; before releasing the device, the position is confirmed. Unstable position of the device, demonstrated by partial prolapse of one of the discs, or impingement of the mitral apparatus, the superior or inferior vena cava or coronary sinus indicate the need of device repositioning before release. Residual shunt after device release can be observed. The haemodynamic severity of the interatrial shunt will determine the need of a second device. In most of patients, residual shunts are mild and will improve at follow-up. Finally, echocardiographic modalities permit evaluation of periprocedural complications such as device embolisation, perforation and cardiac tamponade.

NON-INVASIVE IMAGING AFTER TRANSCATHETER ASD CLOSURE

The complication rate at long-term follow-up after transcatheter ASD closure is low (0.8%) [107]. Erosion of the device into the surrounding structures, although rare (<0.1%), is the most serious manifestation. Patients with deficient anterior-superior rims and oversized devices are at the highest risk for developing this complication. Other complications include thrombus formation and moderate aortic regurgitation [107]. Echocardiography is the main technique used to evaluate these complications.

FOCUS BOX 6Atrial septal defect closure

Patient selection:

−Percutaneous transcatheter closure of secundum ASDs is indicated for haemodynamically significant left-to-right shunts (ratio of pulmonary blood flow to aortic blood flow (Qp/Qs) >1.5), with right atrial or right ventricular enlargement with or without symptoms

−TOE provides improved image quality and permits accurate assessment of the dimensions, morphology and location of the ASD and dimensions of the rims

−Key anatomic characteristics of ASDs:

- Dimensions of the ASD < 36-40 mm

- Deficient inferior rim, inferior-posterior rim, postero-superior rim, coronary sinus rim or deficient rim toward the pulmonary veins (<5 mm) are all contraindications for percutaneous closure of secundum ASDs

- A deficient anterior-superior rim (<5 mm) does not represent an absolute contraindication for transcatheter-based therapy

During the procedure:

−Fluoroscopy and TOE or intracardiac echocardiography is crucial for optimal procedural guidance

After the procedure:

−TOE and intracardiac echocardiography permit accurate evaluation of residual shunt

−Erosion of the device into the surrounding structures, although rare (<0.1%), is the most serious complication

Ventricular septal defect closure 400 Congenital ventricular septal defect

View chapter "Ventricular septal defect closure"

CONGENITAL VENTRICULAR SEPTAL DEFECT

Ventricular septal defects (VSD) are the most common congenital heart disease at birth. However, spontaneous closure of small defects during childhood leads to a significant decrease in the prevalence of this congenital heart disease in adults. According to current position statement established by the Society for Thoracic Surgery’s Congenital Heart Surgery Database Committee and the European Association for Cardiothoracic Surgery, 4 types of VSDs have been described ( Figure 24 ) [100, 108].

Type 1: this defect lies in the outflow portion of the right ventricle. Its incidence is rather high in Asian populations. Spontaneous closure of this type of defect is unlikely.
Type 2: also known as perimembranous, this type is the most frequent VSD (80%). On the right ventricular side, the defect is in close spatial relationship with the septal leaflet of the tricuspid valve that frequently forms an aneurysm of the defect. On the left ventricular side, the defect is spatially related to the aortic valve.
Type 3: this defect involves the inlet of the ventricular septum immediately inferior to the atrioventricular valve apparatus. This type is commonly observed in patients with Down’s syndrome.
Type 4: or muscular septal defect is the second most frequent VSD. Muscular VSDs can be located in the mid-ventricular septum, apically, or in the margin between the septum and the right ventricular free wall, and can be multiple in number. Spontaneous closure is common leading to a reduced incidence of these defects in the adulthood.

The size of isolated VSDs determines their clinical presentation. Small defects (< 25% of the size of the aortic annulus diameter) do not lead to significant left-to-right shunts, heart failure symptoms or increased pulmonary pressures. These defects are usually suspected by the presence of a systolic murmur. Moderate defects (25% to 75% of the size of the aortic annulus diameter) may determine moderate left-to-right shunts and left ventricular overload. Heart failure symptoms can be frequently observed in these patients. Finally, large VSDs (>75% of the size of the aortic annulus diameter) usually present with heart failure during the infancy due to moderate left-to-right shunts, severe left ventricular volume overload and increased pulmonary pressures. Eisenmenger syndrome (right-to-left shunt) can develop during the childhood or the adolescence [100].

VSD closure is recommended when there is a haemodynamically significant left-to-right shunt (Qp/Qs >1.5-2), heart failure symptoms, signs of left ventricular volume overload and increased pulmonary pressures or endocarditis [100]. In patients with irreversible pulmonary hypertension and Eisenmenger syndrome, VSD closure is not recommended.

Surgical closure remains as the treatment of choice of VSDs. However, recent developments in transcatheter-based therapies have increased the number of percutaneous closure procedures with procedural success rates around 95% and low complications rate (10%) [109, 110, 111]. Current evidence has demonstrated the feasibility of these percutaneous closure techniques in perimembranous and muscular defects. Complete atrioventricular block requiring pacemaker implantation and aortic or tricuspid regurgitation are the most frequent complications of these procedures.

In order to maximize the results of transcatheter-based closure procedures, accurate characterisation of VSDs is crucial. Echocardiography remains the imaging technique of choice to characterise VSDs and their haemodynamic consequences (left ventricular volumes and function, pulmonary hypertension). However, MRI is a promising technique that can also permit the accurate evaluation of the haemodynamics and location of the defect and integration of MRI data with life x-ray, providing highly accurate procedural guidance and improved results [112].

Non-invasive imaging before transcatheter-based closure

The evaluation of the number, size and location of VSDs is the first step. The accuracy of transthoracic echocardiography is highest for the diagnosis of type 1 (outflow of the right ventricle) and type 3 (inlet) septal defects, slightly less for perimembranous defects and least for muscular defects. Muscular septal defects can lie in a large area, are usually small and multiple in number and, during systolic myocardial contraction, these defects may be obscured, further reducing the accuracy of echocardiography to diagnose them. ( Figure 24 ) illustrates the most useful echocardiographic windows to localise the VSD. Next, evaluation of the flow direction and velocity of the shunt with colour and continuous wave Doppler imaging should be performed. When the septal defect is small, colour-Doppler imaging shows thin turbulent flow within the septum and continuous wave Doppler recordings demonstrates high velocity jet, indicating the high pressure gradient between the ventricles. In contrast, large defects appear as wide jets on colour-Doppler imaging and the peak velocity jet recorded with continuous wave Doppler is lower.

In perimembranous VSDs, measurement of the diameter of the VSD and the subaortic rim is crucial before percutaneous closure. In addition, the spatial relationship of the VSD and the atrioventricular and aortic valves should be evaluated. In patients with a “subaortic rim” of ≤1 mm or prolapse of one of the aortic cusps, surgical closure may be the preferred approach. Transthoracic or transoesophageal echo permits accurate evaluation of these aspects. In addition, MRI can accurately quantify the left-to-right shunt and measure the dimensions of the defect with phase-contrast cine MRI and ECG gated segmented SSFP sequences, respectively [112, 113]. In particular, from the various SSFP sequences, the VSD can be localised and the contours of the defect and the surrounding cardiac structures (aortic valve, right and left ventricles) can be traced providing a surface rendering of the MRI-derived contours. This surface rendering is thereafter overlaid onto live x-ray imaging allowing accurate procedural guidance ( Figure 25 ) [112]. For muscular VSDs, the size of the muscular defect, number and proximity to valves have to be determined in order to define the feasibility of the percutaneous closure procedure. The size of the defect can be determined based on the width of the regurgitant jet on echocardiography ( Figure 26 ). Furthermore, a distance of at least 4 mm should separate the defect from the mitral, tricuspid, aortic and pulmonary valves. It is necessary to distinguish between anterior, mid-muscular and inlet locations because the percutaneous procedure has to be modified accordingly to increase the chances of device delivery without collateral damage.

Non-invasive imaging for procedural guidance

Transthoracic echocardiography or TOE, in combination with fluoroscopy, remains the mainstay technique to guide percutaneous transcatheter VSD closure. The complexity of the procedure demands highly accurate guidance to ensure appropriate delivery of the occluder device [114]. Commonly, with the help of an initial left ventricular angiogram, the defect is localised and crossed retrogradely with the guidewire into the right ventricle and the inferior vena cava. Next, the wire is snared and exteriorised into the right internal jugular vein. At this phase, the severity of atrioventricular or aortic valve regurgitation should be evaluated. Increased valvular insufficiency may indicate an increased tension on the looped wire that may permanently damage the cardiac structures. Then, the delivery system with the occluder device inside is advanced from the right internal jugular vein through the VSD and terminating into the left ventricle ( Figure 26 ). The left ventricular disc is then deployed and the correct apposition on the left ventricular side is confirmed before release of the RV side. Finally, the right ventricular disc is deployed and the position of the occluder device and the presence of residual shunt are evaluated before release. In addition, the competence of the atrioventricular valves and aortic valve is evaluated. In addition, preliminary data have shown that fusion imaging of MRI data and live x-ray has improved image guidance and may simplify the procedure by allowing direct antegrade crossing of perimembranous septal defects [112].

POST-MYOCARDIAL INFARCTION VENTRICULAR SEPTAL DEFECT

Post-myocardial infarction VSD is a rare complication in the current era of primary percutaneous coronary intervention. Left untreated, post-myocardial infarction VSDs carry 90% mortality at 2 months follow-up. In contrast, surgical treatment provides superior outcome by reducing the mortality rate by half. Recently, a few experiences have demonstrated that percutaneous closure of these defects is also feasible with promising results [115].

Advanced age of the patients, associated comorbidities and haemodynamic instability are challenges to percutaneous transcatheter closure of this type of VSD. In addition, the defect is less well circumscribed and usually shows a fragile rim of infarcted myocardium that can be prone to further tearing. Detailed echocardiography is needed to determine the size, shape and location of the VSD. During the procedure echocardiographic guidance is essential as described above. Intra-procedural TOE may show that the VSD enlarges during the procedure due to the friability of the surrounding tissue and extension of the tear. Accordingly, more than one occluder device is commonly needed. In addition, an oversized device is preferentially used to anticipate necrosis of the septum around the defect.

TRAUMATIC VENTRICULAR SEPTAL DEFECT

Experience with transcatheter closure of traumatic VSD is limited. This type of VSD, including those that are haemodynamically significant, tends to be located in the muscular septum and may spontaneously close if the patient survives [116]. When percutaneous closure is considered, a detailed non-invasive imaging is necessary to exactly delineate the extent of trauma and presence of multiple injuries, which may indicate the need for surgery. ( Figure 26 ) shows an example of traumatic VSD visualised with TOE and closed percutaneously.

FOCUS BOX 6Ventricular septal defect closure

Congenital VSD:

−VSD closure is recommended when there is a haemodynamically significant left-to-right shunt (Qp/Qs >1.5-2), heart failure symptoms, signs of left ventricular volume overload and increased pulmonary pressures or endocarditis

−Surgical closure remains the treatment of choice for VSDs

−Transthoracic echocardiography or TOE, in combination with fluoroscopy, remains the mainstay technique to guide percutaneous transcatheter VSD closure

−Complete atrioventricular block requiring pacemaker implantation and aortic or tricuspid regurgitation are the most frequent complications of percutaneous closure of VSD

Post-myocardial infarction VSD:

−Percutaneous closure of this type of defects is challenged by haemodynamic conditions, less well-circumscribed defects and usually with fragile rims of infracted myocardium that can be prone to further tearing

Traumatic VSD:

−This type of VSD, including those that are haemodynamically significant, tends to be located in the muscular septum and may spontaneously close if the patient survives

Transcatheter left atrial appendage closure

Transcatheter left atrial appendage (LAA) closure has emerged as an alternative therapy for atrial fibrillation patients in whom oral anticoagulation (OAC) may be contraindicated. Two devices are currently available for LAAC: the WATCHMAN FLX (Boston Scientific, MN) and the Amplatzer Amulet device (Abbott, USA). The PROTECT AF (WATCHMAN Left Atrial Appendage System for Embolic Protection in Patients With Atrial Fibrillation) and PREVAIL (Watchman LAA Closure Device in Patients With Atrial Fibrillation Versus Long Term Warfarin Therapy) have proven the clinical effectiveness and safety of the WATCHMAN LAA closure device .[117, 118, 119] In patients with contraindications to OAC, the LAA closure may also reduce the risk cerebrovascular stroke.

Pre-procedural imaging is essential for intervention planning and success. TOE is the gold standard for device sizing, exclusion of LAA thrombosis and procedural guidance and follow-up.

Multiplanar MDCT reconstruction has improved pre-procedural planning through:

Accurate assessment of LAA shape/size and device selection in variable anatomies.
Exclusion of LAA thrombus using delayed contrast imaging.
Planning of trans septal puncture with prediction of optimal fluoroscopic angulation for procedure.
Computational modelling/ 3D printing for procedure optimization.
Multi-planar reconstruction of MDCT: The ostium of the LAA is defined by the plane connecting the base of the proximal left circumflex artery and the left upper pulmonary vein. Then, the LAA ostium cross-section is obtained from orthogonal projections. The LAA ostium maximum and minimum diameters are measured from the corresponding cross-sectional image. ( Figure 27 )

Device sizing is based on the landing zone maximum diameter, with 3- to 6-mm oversizing. Every device has specific guidelines for size selection.[120]

Transcatheter PFO closure

Patent foramen ovale (PFO) is involved in the pathogenesis of many medical conditions. The benefit of PFO device closure has been shown in randomized clinical trials (RCTs) compared to medical therapy in patients with cryptogenic stroke. In a recent document published by EAPCI, several techniques for diagnosis of PFO as contrast TOE, contrast-enhanced transthoracic echocardiography (c-TTE) have been recommended [121]

C-TOE allows PFO characterisation, optimum visualisation of the interatrial septum and intra cardiac shunt.

Contrast enhanced transcranial Doppler (c-TCD) is comparative to c-TOE with 94% sensitivity and 92% specificity. c-TTE was only 88% sensitive and 82% specific with an AUC of 0.91[121].

TOE is necessary before PFO closure to confirm the diagnosis, full delineation of the PFO tunnel and surrounding structure and to exclude any other intracardiac source of thromboembolism[122] .

Personal perspective – Jeroen J. Bax

Advances in transcatheter-based therapies have been one of the main therapeutic breakthroughs of the last decade. Various cardiovascular diseases that were exclusively treated with surgery can be currently treated with less invasive procedures yielding similar results. Particularly in the field of structural heart disease, percutaneous transcatheter therapies have been a revolution. In most of secundum ASDs, transcatheter closure is the first therapeutic option. The advent of self-expandable or balloon-expandable aortic prostheses and mitral valve transcatheter-based devices has provided a feasible and effective therapeutic option for patients with severe aortic stenosis or mitral regurgitation who have a high operative risk, respectively. Non-invasive imaging modalities are the cornerstone to select patients who are candidates for transcatheter-based procedures, to accurately guide the interventions and confirm the results. In particular, 3-dimensional imaging techniques have provided superb image quality to visualise the cardiac structures from unique orientations previously available only to the surgeons. These advances have changed the catheterisation laboratories into hybrid operating rooms with sufficient space to hold multimodality imaging capabilities. Image-fusion technologies (MRI and MDCT data integrated to live x-ray) have provided promising results and additional developments are needed in order to implement this equipment in daily clinical practice.

Non-invasive imaging for structural heart disease