PART III - BALLOON AORTIC VALVULOPLASTY
TABLE OF CONTENTS
BOOKSHOP
Updated on December 14, 2018
PART III

Balloon aortic valvuloplasty

Eric Durand, John Webb, Hélène Eltchaninoff

Summary

Balloon aortic valvuloplasty has become a straightforward and relatively safe procedure that plays an increasingly useful role as a part of a TAVI procedure and as an adjunct in the management of aortic stenosis, in particular, as a bridge to a more definitive procedure.

Background

Calcific aortic stenosis (AS) is the most frequent valvular heart disease in the Western world. Its prevalence increases with age. Community data documents the prevalence of moderate or severe AS as 0.6%, 1.4% to 4.6% in patients aged 55 to 64, 65 to 74, and ≥75 years of age, respectively [1]. Once moderate AS is present progression is somewhat predictable with an average reduction in aortic valve area of 0.1cm2/year [2], and simultaneous increase in the transvalvular gradient, eventually resulting in typical symptoms of angina, syncope and heart failure. Once these symptoms are present the average survival is 2 to 3 years [3, 4, 5].

Before the era of TAVI, only surgical aortic valve replacement (SAVR) was appropriate and possible to offer survival and symptomatic benefit. However, about one-third of the patients could not be operated either because of their advanced age or their co-morbidities [6].

Percutaneous balloon aortic valvuloplasty (BAV) for calcific aortic stenosis was first reported by Cribier in 1986 [7]. After a major initial enthusiasm of the cardiology community, it became apparent that initial haemodynamic and symptomatic improvement was transient and related to a very high rate of restenosis. Furthermore, survival was not improved and similar to that of untreated AS.

Since 2017, European Society of Cardiology and American College of Cardiology/ American Heart Association have revisited the indication for aortic valve intervention given the results of new randomized studies in particular in intermediate-risk patients. In summary, SAVR is indicated for low-risk patients with severe AS and symptoms, reduced LV function, and in some asymptomatic patients. TAVI has received growing attention and is now not limited to inoperable and high-risk patients and is an alternative to surgery in intermediate-risk patients when a transfemoral approach is feasible [8, 9]. In contrast, the place of BAV is very limited (class IIb, C) and may be considered: 1) as a bridge to SAVR or TAVI in haemodynamically unstable patients; 2) in patients with symptomatic severe aortic stenosis who require urgent major non-cardiac surgery; 3) as a diagnostic means in patients with severe aortic stenosis or other potential causes for symptoms (i.e. lung disease) and in patients with severe myocardial dysfunction, pre-renal insufficiency or other organ dysfunction that may be reversible with BAV when performed in centres that can escalate to TAVI [8, 9].

FOCUS BOX 1Aortic stenosis European guidelines
  • Aortic stenosis is the most frequent valvular disease in the Western world. Its prevalence increases with age
  • Current guidelines recommend surgical aortic valve replacement for low-risk patients with severe AS and symptoms, reduced LV function or concomitant heart surgery
  • Current guidelines recommend TAVI in patients with severe AS and symptoms, if inoperable or at high-risk for surgery. TAVI is also an alternative for surgery in intermediate-risk patients when a transfemoral approach is feasible.

THE PROCEDURE

The common femoral artery is punctured superior to its bifurcation into the superficial and deep femoral arteries, and below the inguinal ligament. The femoral acetabulum serves as a useful fluoroscopic landmark. Pre-closure of the puncture site can be performed, using a 10 Fr Prostar or one or two 6 Fr ProGlide suture devices (Abbott Laboratories, Abbott Park, IL, USA). Closure with Angio-Seal (St. Jude Medical, St. Paul, MN, USA) 8 Fr is another alternative. An 8 Fr to 14 Fr sheath is placed depending on the size and type of valvuloplasty balloon selected. Heparin is typically administered (70 IU/Kg) and frequently reversed by protamine at the end of the procedure.

A diagnostic coronary catheter is introduced into the aortic root over a standard J wire. An Amplatz left 1 for a narrow or vertical root and an Amplatz left 2 catheter for a larger or more horizontal root are typically favoured, although a Judkins right, multipurpose or pigtail catheter can be used. A straight tipped 0.035” wire is carefully manipulated in a probing manner making gentle passes across the central orifice of the stenotic valve [10]. After gaining access to the left ventricle the wire and catheter are exchanged for an 0.035” exchange 260 cm length stiff wire (e.g., Amplatz extra stiff 3 cm soft tip J; Cook Medical Inc., Bloomington, IN, USA DK) which offers optimal support but has a softer tip which must be manually-shaped by the operator to sit atraumatically within the ventricle.

In contrast to the common transarterial retrograde technique just described, a transvenous approach can be used in particular when a femoral approach is impossible [12]. This involves femoral venous puncture followed by transseptal access to the left atrium, through the mitral valve and then antegrade across the aortic valve. Potential advantages of this approach are the safety of large sheath access via the femoral vein, ease of crossing the stenotic aortic valve from the ventricle and balloon stability during inflation. This approach, however, is less commonly used due to complexity and the need for transseptal access and is usually restricted to patients with no suitable femoral arterial access.

FOCUS BOX 2Techniques of balloon aortic valvuloplasty
  • BAV has become simple and quite safe.
  • It is performed under local anaesthesia using the common femoral retrograde approach using standard catheterisation technique
  • Balloon inflation is performed under rapid ventricular pacing so as to stabilise the balloon across the aortic valve

BALLOON STABILISATION

Balloon catheter stability during valvuloplasty is crucial, because during inflation the balloon tends to be ejected into the aorta. A balloon length of 4 to 5 cm is generally preferred as 3 cm balloons are difficult to stabilise and 6 cm balloons require prolonged inflation, Self-seating hourglass shaped balloons can also improve stability markedly ( Figure 2).

Rapid ventricular burst pacing is often used to reduce systemic arterial blood pressure, transvalvular flow and cardiac motion during BAV [13]. Typically a transvenous right ventricular pacing lead is utilised with burst pacing at rates of 160 to 220 per minute ( Figure 3 - Panel A). Reliable 1:1 ventricular capture must be obtained ( Figure 3 - Panel B). There is potential for ischaemic left ventricular dysfunction with hypotension and ventricular arrhythmias. Burst pacing should be of short duration and defibrillation readily available. Patients must be warned beforehand that they may feel temporarily dizzy and presyncopal during balloon inflation. If the patient is hypotensive before or after BAV, 100 to 200 mcg of phenylephrine, repeated as necessary, may rapidly and very safely bring the pressure up without causing tachycardia or ventricular arrhythmia.

Of note, “direct left ventricular rapid pacing” is also possible to simplify BAV and

TAVI procedure. This technique consists in a left ventricular pacing through the 0.35 inch back up guidewire inserted into the left ventricle. The cathode of an external pacemaker is placed on the external end of the 0.35’ wire using an alligator clamp. The anode is placed (also using an alligator clamp) on a small needle piercing the subcutaneous tissue at the site of the anesthetized groin [14].

EVIDENCE FOR EFFICACY

BAV has never been subjected to a large scale randomised trial.

Informed practice is dependent on large multicentre registries from the late 1980’s, such as the Mansfield Scientific Balloon Aortic Valvuloplasty Registry [28, 29, 30, 31, 32, 33, 34, 35] and the NHLBI Balloon Valvuloplasty Registry [36, 37] and on single centre registries. [38, 39, 40, 41, 42, 43, 44, 45, 46].

Boone et al. summarised findings from 50 publications documenting results from over 2,400, primarily elderly non-operative or high-risk operative, patients [46]. All reports were case series (Level of Evidence C). Excluded were reports of BAV in young patients with congenital AS where BAV remains a Class I therapeutic option [46]. Changes in aortic valve area and mean transaortic gradient are summarised in table 1. Generally valve area increased to between 0.8 and 1cm2 ( table 1). It appeared that BAV was successful in reducing the transaortic gradient to < 25 mm a modest degree in most, but not all, patients with critical calcific AS.

Published series consistently report significant improvement in symptoms in 50% to 75% of survivors. Advanced age, poor left ventricular function and poor functional class appear to be the main pre-procedural predictors of poor outcome [36]. In one analysis less than half of those with a left ventricular ejection fraction <45% had symptomatic improvement [48]. Although most patients experience some haemodynamic and symptomatic improvement these changes were generally small. Moreover the benefit was not durable. The reported rate of valvular restenosis (defined as ≥50% loss in the valve area achieved following BAV) varies between 25 and 47% at 6 months [49, 50, 51, 52] and up to 80% at 15 months [53].

Survival ranged from 75-38% (average 65%) and 28-60% (average 35%) at one year and two years respectively. These survival statistics are similar to that of untreated AS in elderly patients [5, 54]. Furthermore, the impact of BAV in patients not undergoing aortic valve replacement in the PARTNER trial (cohort 1B) has been recently reported. Survival at 3 months was greater in the BAV group compared with the no BAV group (88.2% vs. 73.0%) whereas survival was similar at 6-month follow-up (74.5% vs. 73.1%). There was improvement in quality of life parameters when paired comparisons were made between baseline and 30 days and 6 months between the BAV and no BAV groups, but this effect was lost at 12-month follow-up [55].

It appears, therefore, that BAV alone does not alter the natural history of AS for the majority of patients. As a consequence current AHA/ACC guidelines give a class III recommendation to the concept of BAV as an alternative to surgical valve replacement ( Table 2) [46].

FOCUS BOX 3BAV results
  • BAV is successful in reducing the transvalvular gradient, improving symptoms and left ventricular ejection fraction
  • The restenosis rate is high, close to 80% at one year and BAV does not improve survival when performed as a stand-alone procedure

ESTIMATION OF ANNULUS SIZE

An estimate of aortic annular diameter is desirable to select an appropriate sized valvuloplasty balloon. As a very rough rule of thumb, small patients may be appropriately treated with an 18 to 20 mm balloon, medium patients with a 22 to 24 mm balloon and large patients with a 25 to 28 mm balloon. An undersized balloon will have little effect, while an oversized balloon runs the risk of annular injury. Echocardiographic assessment of annular size is more reliable. Aortography may be helpful, however it should be remembered that the left ventricular outflow portion of the aortic annulus is not visualised during aortography ( Figure 4).

The sizing of the aortic annulus diameter is important prior to TAVI in order to facilitate the selection of an appropriate implant. If the diameter of an inflated valvuloplasty balloon is known then this may assist in this evaluation. Balloon diameter can be determined according to the labelled balloon size or can be estimated with calibration software. Correlation with root size can be facilitated by a simultaneous aortic root contrast injection during balloon inflation. In addition an assessment can be made of the potential for coronary obstruction at the time of TAVI ( Figure 4).

’Push-back’’ pressure as measured from a manometer attached to the balloon lumen or inflation device has been correlated with aortic annular diameter. Pressure can be seen to rise abruptly as the balloon comes into contact with the annulus during inflation. This has been advocated as a sizing technique during TAVI [56].

COMPLICATIONS

The reported incidence of complications varied widely in the early registries ( table 1), with the overall complication rate ranging from 9% to 25%. The latest results of Rouen large experience on more than 300 patients suggest that risks in contemporary practice include renal failure, stroke (1.9%), vascular complications (1.9%), annular rupture (0.3%) and, exceptionally, pericardial tamponade [59]. Several groups confirm that procedural complications have been reduced considerably in comparison to early experience [31, 37, 40, 49, 52, 57, 58, 59]. It seems that with increased procedural experience, changes in technique and refinements in equipment the procedure is becoming safer and more routine, albeit not entirely without complications.

FOCUS BOX 4BAV complications
  • With improved technique and operator skills, complications are rare
  • Massive aortic regurgitation occurs in less than < 2%

RESTENOSIS AFTER BAV

BAV improves leaflet mobility by fracturing calcified nodules and creating cleavage planes within collagenous stroma [60, 61]. Unfortunately restenosis is a constant finding following BAV. The process of restenosis involves granulation tissue, fibrosis and active osteoblast mediated calcification within the valve leaflets [62].

Given the early benefit of BAV, repeat valvuloplasty has emerged as a potential therapeutic strategy. Repeat BAV does have a modest benefit in terms of valve area and symptoms in many patients [29, 39, 49]. However, the degree and duration of symptom relief is less with subsequent procedures [49]. This has led to the investigation of means to inhibit restenosis after BAV. The small RADAR pilot study of external beam radiation applied a few days following BAV found relatively low restenosis rates at 1-year of 21-30% [63]. The effect was dose-responsive and substantially lower than expected [53]. A potential role for balloon delivery of anti-restenosis pharmaceuticals to the aortic valve leaflets is also being investigated [64].

BRIDGE TO DEFINITIVE THERAPY

Several reports have suggested a potential role of BAV prior to surgical aortic valve replacement, an approach which reportedly can have a 2 year survival as high as 92% [44]. This may be an attractive strategy for selected patients with uncontrolled heart failure or haemodynamic instability [65]. However, most symptomatic patients might arguably be better served by avoiding unnecessary delay in proceeding to aortic valve replacement. Similarly BAV has been utilised as a bridge to TAVI as contemporary regulatory, funding and other limitations on this new technology often mean unavoidable delays with definitive treatment. Limited evidence suggests that definitive procedural outcomes may be improved in patients undergoing staged BAV prior to subsequent TAVI.

BAV has also been utilised to reduce the risk of non-cardiac surgery or as temporary relief in the setting of an acute illness when the risk of surgical valve replacement is prohibitive [59, 66, 67, 68, 69, 70]. Of particular interest is the use of BAV in patients with severe left ventricular dysfunction. On occasion left ventricular function may improve following successful valvuloplasty, facilitating acceptance for more definitive therapy. Low dose dobutamine echocardiography can help in predicting left ventricular functional recovery by assessing contractile reserve [71].

FOCUS BOX 5BAV indications in the TAVI era
  • There is an increasing role of BAV as a bridge to surgical aortic valve replacement or TAVI in patients who present with temporary contra-indications
  • Pre-dilatation is performed as the first step of the TAVI procedure
  • Non compliant balloons may be also used for post dilatation of balloon-expandable prosthesis at the exact diameter. Post-dilatation may be also performed in order to reduce the severity of residual paravalvular leak after balloon or self-expandable prosthesis.

AS A PART OF TAVI PROCEDURE

At the beginning of TAVI, pre-dilatation of the aortic valve has been regarded as an essential step during the TAVI procedure. Pre-dilatation was supposed to facilitate positioning and deployment of the prosthetic valve in particular for self-expanding valves. However, recent evidence has suggested that aortic valvuloplasty may cause complications and that high success rates may be obtained without prior dilatation of the valve. The feasibility, safety, and efficacy of “direct” TAVI, without pre-dilatation, has been recently reported in a systematic review and meta-analysis [72]. Mean device success with direct TAVI was 88% with <5% of bail-out techniques. There were no differences between direct and TAVI with pre-dilatation in short-term mortality or cerebrovascular events. Direct TAVI was associated with reduced moderate or severe paravalvular leak post-TAVR but not with a reduced risk of permanent pacemaker implantation. A slight increase in post-dilatation was observed in direct transfemoral-TAVI recipients [72]. Randomized studies are ongoing to determine the potential benefits of direct TAVR.

AS A PART OF TAVI FOR FAILED SURGICAL PROSTHESIS

Valve-in-valve (ViV) transcatheter aortic valve implantation has been established as a safe and effective treatment for failed surgical bioprosthetic valves in patients at high risk for complications related to reoperation. Patients who undergo ViV TAVI are at risk of patient-prosthesis mismatch, as the transcatheter heart valve is implanted within the ring of the existing surgical bioprosthesis, limiting full expansion and reducing the maximum achievable effective orifice area of the transcatheter heart valve. Importantly, patient-prosthesis mismatch and high residual transvalvular gradients are associated with reduced survival following VIV TAVI. Bioprosthetic valve fracture (BVF) using a high-pressure balloon can be performed to facilitate VIV TAVI. BVF can be performed before or after ViV TAVI by inflation of a high-pressure balloon positioned across the valve ring during rapid ventricular pacing. BVF was recently performed in 20 patients undergoing ViV TAVI with balloon-expandable or self-expanding transcatheter valves in Mitroflow, Carpentier-Edwards Perimount, Magna and Magna Ease, Biocor Epic and Biocor Epic Supra, and Mosaic surgical valves. Successful fracture was noted fluoroscopically when the waist of the balloon released and by a sudden drop in inflation pressure, often accompanied by an audible snap. BVF resulted in a reduction in the mean transvalvular gradient (from 20.5±7.4 to 6.7±3.7 mm Hg, P<0.001) and an increase in valve effective orifice area (from 1.0±0.4 to 1.8±0.6 cm2, P<0.001). No procedural complications were reported [73].

Personal perspective – Hélène Eltchaninoff

BAV does suffer from limited efficacy and occasional complications. Eventually we may see the role of stand-alone BAV recede as TAVI becomes a more routine, predictable, reproducible, definitive and readily available procedure. Currently an adjunctive role during TAVI seems relatively secure and the skills required to perform this procedure are fundamental for any TAVI operator. However improvements in valves and valve delivery systems are rendering routine BAV pre- and post-dilatation less necessary. Randomized studies evaluating the benefit of “direct” TAVI, without pre-dilatation, are ongoing. Bioprosthetic valve fracture, using high-pressure balloon, is a new promising approach for ViV TAVI procedures in order to reduce the incidence of patient-bioprosthesis mismatch.

Online data supplement

Moving image 1
Balloon inflation during valvuloplasty

SHARE YOUR COMMENT