Patent ductus arteriosus closure

Summary

The ductus arteriosus is a vascular structure that connects the proximal descending aorta to the roof of the main pulmonary artery near the origin of the left pulmonary artery. It normally closes spontaneously within 24 to 48 hours after birth by the contraction of medial smooth muscle in the vessel wall, due to the increased oxygen tension and reduced prostaglandin E2 and I2 levels. Endothelial adhesion followed by replacement of the muscle fibres with connective tissue results in the formation of the ligamentum arteriosum within two to three weeks. If this does not happen, there is a patent or persistent ductus arteriosus (PDA).

Introduction

The incidence of PDA is approximately 1 in 2,000 in full-term infants and represents 5% to 10% of all congenital heart disease in children. PDA is found twice as often in females than in males. In adulthood, a PDA is not often encountered since it is usually discovered and treated during childhood [11. Benson LN, Cowan KN. The arterial duct: its presence and patency. In: Anderson RH, Baker EJ, Macartney FJ et al. eds. Paediatric Cardiology, 2nd edition. London: Churchil Livingstone. 2002 - p-1404-59. ]. Presence of a PDA beyond the first week of life occurs in as many as 50% of premature babies and in more than 80% of severely premature extremely low birth weight (ELBW) infants (<1,000 g at birth). [22. Hamrick SE, Hansmann G. Patent ductus arteriosus of the preterm infant. Pediatrics. 2010;125(5):1020-1030. ].

The haemodynamic and the clinical significance of the PDA are determined by size, shape, length and age at presentation. Large and short PDAs have a greater haemodynamic impact compared to tortuous and stenotic PDA. In paediatric age range, the haemodynamic impact of PDA is related to the ratio between the PDA and aortic diameters: in a preterm infant a 2 mm duct can result in major haemodynamic consequences, whereas a 4 mm duct may result in no symptoms in an adolescent weighing 40 kg.

Haemodynamically insignificant or small ducts result in no symptoms. The indications and timing for closure of small ducts are controversial. Most paediatric cardiologists would hesitate to close clinically silent ducts, in spite of isolated case reports of endarteritis in patients with a silent PDA [33. Thilen U, Astrom-Olsson K. Does the risk of infective endarteritis justify routine pda closure? Eur Heart J. 1997;18:364-6. ]. In premature babies PDA is associated with adverse events such as necrotizing enterocolitis, chronic respiratory disease, pulmonary and cerebral hemorrhage, and death.

Haemodynamically significant ducts (moderate or large) may have symptoms such as wide pulse pressure, active precordial pulsation, and a loud continuous or systolic murmur.

The chest x-rays in those patients reveal increased pulmonary blood flow and cardiac enlargement. The ECG reveals prominent left ventricular forces (due to the increased left ventricular mass) with prominent Q-waves in lateral chest leads.

A detailed echocardiographic evaluation of the duct anatomy and physiology is important before starting the occlusion procedure. By echocardiography is possible to estimate the left chambers volume overload as well as the size and the shape of the PDA. A precise echo study is essential for patient selection and to plan the procedure. In particular, by obtaining an apical 4-chamber view it is possible to assess left atrial and ventricular dilatation as well as to exclude pulmonary hypertension. By obtaining a parasternal short axis view or by off-axis views (sub-clavicular views or suprasternal views) it is possible to estimate the size and shape of PDA, while continuous wave Doppler analysis can assess the systolic and diastolic gradient across the PDA in order to exclude pulmonary hypertension.

In adult patients, the acoustic window may be inadequate to make a careful evaluation of the PDA, however, additional exams like MRI or angioCT are rarely indicated [44. Baumgartner H, De Backer J, Babu-Narayan S V, Budts W, Chessa M, et al. 2020 ESC Guidelines for the management of adult congenital heart disease. Eur Heart J. 2020 Aug 29; 00:1-83. ].

Overview of the procedure

It is usual practice to perform the procedure under general anaesthesia in infants and children and with local anaesthesia in adolescents and adults.

Lidocaine is administered subcutaneously around the femoral vessels and then a short 4 to 6 Fr sheath is placed in either the right or left femoral vein, and a short 4 Fr sheath is placed in a femoral artery (preferably in the opposite groin from the venous sheath). Typically heparin (100 IU/kg) is administered thereby reducing the risk related to arterial puncture, especially in small babies.

Antibiotic prophylaxis is also necessary with a single dose of a second-generation cephalosporin at the beginning of the procedure.

A complete set of right heart haemodynamics (right atrium, right ventricle, and both left and right pulmonary arteries) should be recorded using a 4 or 5 Fr multipurpose catheter (Cordis Corp., Miami, FL, USA). It is essential to avoid having the catheter tip close to the duct orifice. The aortic pressure can be recorded using the arterial approach with a 4 Fr pigtail catheter. Calculation of the shunt and pulmonary pressures/resistances can be done, but it must be remembered that this is often inaccurate because the oxygen saturations from the MPA are deceptively high.

Adults with a large PDA and elevated pulmonary vascular resistance represent a specific challenge [33. Thilen U, Astrom-Olsson K. Does the risk of infective endarteritis justify routine pda closure? Eur Heart J. 1997;18:364-6. , 44. Baumgartner H, De Backer J, Babu-Narayan S V, Budts W, Chessa M, et al. 2020 ESC Guidelines for the management of adult congenital heart disease. Eur Heart J. 2020 Aug 29; 00:1-83. ]. In this specific type of case more tests should be performed to evaluate whether PDA occlusion would reverse pulmonary artery hypertension. An occlusion PDA test can be performed either by using a balloon end-hole catheter or by using a sizing balloon and monitoring the pulmonary pressures from a second venous vascular access with a multipurpose catheter. The systemic arterial pressure should be measured simultaneously. It is nevertheless frequently difficult to make the decision whether or not to close the PDA in such a patient. Recent ESC Guidelines suggest that the closure is feasible if there is evidence of LV volume overload and no PAH (invasive confirmation of PVR <3 WU) or with PVR 3-5 WU, PDA closure should be considered when there is still significant L to R shunt (Qp:Qs >1.5). Values of PVR >5 UW with Qp:Qs>1.5 should be evaluated individually in expert centres [44. Baumgartner H, De Backer J, Babu-Narayan S V, Budts W, Chessa M, et al. 2020 ESC Guidelines for the management of adult congenital heart disease. Eur Heart J. 2020 Aug 29; 00:1-83. ].

An aortogram (1-2 ml of contrast/kg) is performed through a 4 Fr pigtail catheter introduced retrogradely from the femoral artery and positioned in the descending thoracic aorta just distal to the aortic end of the ductus. By injecting in this position, the maximum concentration of contrast medium is delivered into the ductus during diastole with little dissemination into other areas. The lateral and the 45° right anterior oblique projections usually provide the best visualisation of the ductus and the relationships to the adjacent fixed landmarks. The minimum and maximum diameters as well as the length of the PDA are measured. Ductal spasm is not infrequent in infants and may be provoked by attempts to cross it.

By a lateral view aortography, the anatomy of PDAs may be divided in 5 types, according to Krichenko [55. Krichenco A, Benson LN, Burrows, Möes CA, McLaughlin P, Freedom RM. Angiographic classification of the isolated persistently patent ductus arteriosus and implications for percutaneous occlusion. Am Cardiol. 1989;67:877-80. ]:

Type A) conical shape: like a funnel

Type B) window-like: short and large, the aortic diameter may be less than the pulmonary diameter

Type C) tubular: the PDA may be straight (common finding in premature infants) or tortuous, the diameter is more or less constant in length

Type D) candy-like: there is a central aneurism with two or more stenosis at each side

Type E) elongated: similar to conical, but the pulmonary end is more anterior than the anterior rim of the trachea

These features are essential for the choice of the most appropriate device for PDA closure ( Figure 1).

Occlusion devices

Porstmann first reported a transcatheter occlusion of the PDA [77. Porstmann W, Wierny L, Warnke H. Der Verschluss des D.a.p ohne thorakotomie (1 Mitteilung). Thoraxchirurgie. 1967;15:199. ]. However, PDA occlusion in the cathleter laboratory was not popularised until the early 1980s, when the more practical Rashkind PDA occluder was introduced into clinical trials in the US and the rest of the world. Since the introduction of the Rashkind PDA device, many different devices and techniques for transcatheter occlusion of the PDA have been introduced and used around the world.

We can divide the occluder devices into three groups:

1. dedicated coil
2. dedicated occluder devices
3. off-label devices

In this chapter only the first two groups will be discussed. Off-label use of devices (muscular ventricular septal defect occluder, atrial septal occluder, vascular plug, etc) have been reported as case reports or case series in the literature. A description of these procedures, however, is beyond the scope of this chapter.

Generally, coil occlusion carries the lowest cost, and its efficacy is high when the narrowest diameter of PDA is less than 2-3 mm. On the other hand, an occluder device is particularly indicated in conical shape anatomy with a narrowest diameter >2 mm.

COIL OCCLUSION

Case selection and procedure
These general considerations must be taken into account for a successful procedure:

These general considerations must be taken into account for a successful procedure:

• the coil diameters have to be greater than or equal to twice the smallest diameter of the duct;
• the aortic duct ampulla should be large or long enough to accommodate the coil(s);

The Gianturco coil (Cook Inc., Bloomington, IN, USA), has been in clinical use for more than 3 decades: these are small lengths of special stainless steel spring guidewires which are pre-formed into “coils” or small “cylinders” of specific diameters. Each Gianturco coil has multiple fine filaments or fibres of nylon embedded within the twines of the coil wires to increase the thrombogenicity of the coil. The standard coils are available with 0.025”, 0.032” and 0.038” diameter wires. The different preformed diameters of the loops range between 3 mm and 15 mm. The different straightened lengths of the wire, along with the diameter of the loops of the specific coil, determine the number of loops that are formed by each coil. Because of the high incidence and continued potential for embolisation of these coils when they are delivered using the “free-release technique”, multiple modifications of the coils and the delivery techniques have been made: the most practical and the most accepted of these is the controlled-release Cook detachable coil (MReye® Flipper™ Detachable Embolization Coils; Cook Inc., Bloomington, IN, USA) ( Figure 2) often referred to as the Jackson coil.

The detachable coil has a very simple screw attachment mechanism at the proximal end of the coil. The detachable coil can be delivered from either the anterograde approach from a venous introduction or retrograde from the femoral artery: the retrograde approach is preferred and used predominantly. The numbers on the label represent (1) the diameter of the coil loops and (2) the number of the loops which the coil forms when it is extruded. All the detachable coils in Europe are 0.038” coils. The detachable coil is packaged as a straight wire in a thin, clear, straight plastic loading cartridge or tube. The mandril is advanced further out of the distal end of the delivery wire, ( Figure 3) introduced into the proximal end of the loading cartridge, and in through the coil to the distal end of the coil. Once the screw tip is engaged in the coil, the delivery wire is rotated gently clockwise approximately eight times, which tightens the screw to engage the whole length of the threads on the delivery wire into the end of the coil. Once the threads are completely into the coil, the cartridge is then rotated one turn anticlockwise to unwind or back the screw threads out of the coil approximately 1 mm in order to loosen the coil slightly.

The coil is then introduced into the proximal end of the delivery catheter (which is positioned across the duct from the arterial side) and advanced carefully to the tip. When the coil reaches the tip of the catheter, the mandril is fixed against the table and the delivery wire is advanced within the delivery catheter. The coil is advanced off the mandril and out of the catheter tip, and can start coiling.

The catheter is slowly pulled back until the protruding part reaches the pulmonary end of the duct. The coil is then delivered by slowly withdrawing the catheter: this manoeuvre tends to pull the protruding coil out of the MPA resulting in excessive coil protrusion. Small steps at all times will ensure that the coil length protruding out into the pulmonary artery is kept constant.

When the mandril is completely withdrawn, advancing the catheter towards the ampulla usually results in formation of coil turns that should, if possible, be kept within the duct or at the ampulla level in order to avoid protrusion into the aorta ( Figure 4).

The main advantage of the detachable coil is that, at any point during the extrusion, it can be withdrawn into the delivery catheter, repositioned and redeployed. The coil is released unscrewing the wire (anticlockwise rotation) once the position is deemed satisfactory.

In the absence of one of the newer and more suitable devices for occlusion of large PDA, two or even more coils may be delivered simultaneously through a venous-arterial approach.

Nit-Occlud PDA (PFM medical, Wankelstraße 60 50996 Köln, Germany) ( Table 1). is a dedicated coil for PDA occlusion. The degree of stiffness decreases from the aortic side to the pulmonary side, the distal (aortic) part is pre-formed to create larger discs, the body has many soft spirals in order to follow the anatomy of PDA and the last spiral is larger in order to anchor the pulmonary side. Except for the 4x4 mm coil, the prosthesis is asymmetrical, as a consequence the deployment is from the venous circulation. The coil has a dedicated delivery system, so the diagnostic catheter has to be exchanged after the PDA is crossed. The delivery system has three markers that identify the aortic spiral, the core spirals and the end of the detachable coil. The coil can be easily partially or totally withdrawn and replaced. Device release is completed by unscrewing the disposable handle. The definitive closure of the PDA is typically completed within 24 hours of the procedure.

The patient may be sent home the day after the procedure. An echocardiogram prior to discharge is mandatory to exclude the presence of residual shunt or iatrogenic aortic or pulmonary stenosis.

Antibiotic prophylaxis for endocarditis must be recommended for 6 months after the procedure. An echocardiographic follow-up must be perfromed 3 and 12 months after the procedure.

The conventional stainless coils are not MRI compatible and likely to produce artefacts during imaging.

Technical challenges

CROSSING THE DUCT

A challenge which can be encountered just at the beginning of the procedure is an inability to cross the duct from the pulmonary arterial end. In this specific situation a guidewire can be passed through a catheter advanced from the arterial side and snared from the venous side. The venous catheter is then advanced over the guidewire.

COIL POSITION

Excessive deployment of the coil turns in either the aortic or pulmonary end of the PDA may lead to coil embolisation or result in aortic/pulmonary stenosis.

EMBOLISATION

This complication can be encountered more often than others after coil release. The coil usually embolises to the smaller pulmonary branches depending on the diameter size of the coil. The coil can be retrieved using a gooseneck snare (from 5 mm up to 15 mm): when the coil has been captured, it must be retrieved into a long sheath in the pulmonary artery in order to avoid problems with the tricuspid valve tensor apparatus.

When a coil embolises in the aorta, it can be retrieved either from the arterial side or the venous side: in this latter case, when snared it can be deployed again in the duct once the catheter is pulled back towards the MPA.

It is rare to have embolisation to the intracranial arterial vessels. In this situation every effort should be made in order to retrieve it so as to avoid an ischaemic injury.

HAEMOLYSIS

Haemolysis is a rare but serious complication. It is related to a residual flow at the end of the procedure. Once haemolysis is established, it is often difficult to eliminate and other coils may be required.

In a small number of cases (0.3%), duct recanalisation can occur. If a murmur is audible, then a repeat attempt at closure is recommended.

PDA OCCLUSION WITH DEDICATED DEVICES

Small PDAs with a maximum diameter of 2.5-3.0 mm can be closed with detachable coils. Those with a larger diameter are generally not good candidates for PDA closure with coils because of the technical difficulty in achieving a stable position of the coils and the attendant complication of embolisation [1818. Santoro G, Gaio G, Carrozza M, Palladino MT, Russo MG, Calabrò R. Large patent ductus arteriosus closure with multiple controlled-release coils. Int J Cardiol. 2007;116:425-6. ]. For these reasons, in larger PDA a dedicated device is indicated ( Table 1). Since 1997, the Amplatzer Duct Occluder (ADO) (St Jude Medical, Golden Valley, MN, USA) was the first device that had a worldwide diffusion for percutaneous PDA ( Figure 5A and Figure 5B ). This is an asymmetrical device, with a retention disc on the aortic site and a stent able to fill the PDA. The shape of these devices resembles the one of a mushroom. In the last years, other manufacturing companies have designed similar devices for PDA occlusion. The Occlutech® PDA occluder (Occlutech La Cours Gata 2, S-252 31 Helsingborg, Sweden) is made of a flexible and self-shaping nitinol wire mesh. The main body of the device consists of a tapered “shank” and a retention disk on the distal aortic side of the device. The shank is meant to be positioned across the narrowest part of the PDA. The proximal end of the shank (pulmonic end) has a diameter that is 1.5–2.0 mm larger than that of its aortic end and the retention disc has a diameter which exceeds the size of aortic end of the shank by 5.5–8.0 mm. Finally, PET patches are integrated into the shank to facilitate initial sealing and closure of the shunt ( Figure 6). The Occlutech PDA occluder has underwent two designs modifications. It is available in two different shank lengths, each coming in various sizes. [88. Elbashier Abdelbasit M. A, Alwi M, Kandavello G, Che Mood M, Samion H and Ziyad M. Hijazi. The New OcclutechVR PDA Occluder:Initial Human Experience Catheter Cardiovasc Interv. 2015; 86:94–99. ]. Numerous studies have been published demonstrating the safety and the efficacy of transcatheter PDA occlusion with a device [99. Masura J, Walsh K, Thanopoulous B, Chan C, Bass J, Goussous Y, Gavora P, Hijazi ZM. Catheter closure of moderate to large-sized patent ductus arteriosus using the new Amplatzer duct occluder: Immediate and short-term results. J Am Coll Cardiol. 1998;31:878-82. , 1010. Faella HJ, Hijazi ZM. Closure of the patent ductus arteriosus with the Amplatzer PDA device: Immediate results of the international clinical trial. Catheter Cardiovasc Interv. 2000;51:50-4. , 1111. Bilkis AZ, Alwi M, Hasri S, Haifa AL, Geetha K, Rehman MA, Hasanah I. The Amplatzer duct occluder: Experience in 209 patients. J Am Coll Cardiol. 2001;37:258-61. ], and today percutaneous closure is the treatment of choice of PDA. The Amplatzer Piccolo Occluder device (Abbott Medical 5050 Nathan Lane North Plymouth, MN 55442 USA) got U.S. Food and Drug Administration (FDA) approval for transcatheter PDA closure in patients ≥700 g. The Amplatzer Piccolo Occluder is a self-expandable, Nitinol mesh device with a central cylindrical waist and low-profile retention discs that are marginally larger than the waist, resulting in a nearly isodiametric device (Figure….). The device comes pre-loaded on a delivery wire, which has a soft floppy distal end with a microscrew attachment at the tip. It can be delivered through a 4 F Amplatzer TorqVue LP catheter (Abbott Structural Heart, Plymouth, MN). The Amplatzer Piccolo Occluder (previously called ADO II AS) is available in nine sizes ( Figure 1) comprised of three waist diameters (3, 4, and 5 mm) and three lengths (2, 4, and 6 mm) [1212. Sathanandam S. K, Gutfinger D, O’Brien L, Forbes T. J, Gillespie M. J, Berman D. P, Armstrong A. K, Shahanavaz S, Jones T. K, Morray B. H, Rockefeller T. H, Justino H, Nykanen D. G, Zahn E. N. Amplatzer Piccolo Occluder clinical trial for percutaneous closure of the patent ductus arteriosus in patients ≥700 grams Catheter Cardiovasc Interv. 2020;1–11. ]. The technical feasibility of the percutaneous procedure depends on the PDA size and on the descending aorta diameter, because the use of large device increases progressively the risk of aortic or left pulmonary artery stenosis. Amplatzer duct occluder and Occlutech PDA Occluder devices have the best efficacy in type A and type E PDA. For type C and type D PDA some variants of the first device are available: ADO II and Amplatzer Piccolo Occluder previously called ADO II Additional Sizes (AS). These two devices are “candy-shaped”: they have two symmetrical discs proximally and distally while in the middle there is a central waist able to fill the PDA. If the ADO I has a fixed shape, ADO II and ADO II AS have two points of higher flexibility between the discs and the waist. As consequence the device is able to follow a kinked segment or a stenosis.

DISC AND STENT DEVICES

Large PDAs have frequently a conical shape. As consequence the disc and stent devices are most commonly used in the cath lab. These devices, with small variations between the factories, are a woven mesh of shape-memory nitinol wires, with one or more membranes sutured inside to enhance the occlusion. The PDA occluder self-expands into a slightly tapered, fat, tubular device, which is designed to fix within and occlude the patent ductus by expanding and stretching the walls of the lumen of the PDA. The tubular portion of the device tapers 1-2 mm from the largest to the narrowest diameter. The retention disc at the distal (aortic) end of the device is 4 to 6 mm larger in diameter than the larger part of the tubular portion, with small differences between the factories. Proportional to the diameters, the device length also increases, typically from 5 up to 10.5 mm, with significant differences between the factories.

Case selection and procedure

Both the femoral artery (left groin, 4 Fr sheath) and vein (right groin, 4-5-6 Fr sheath) are cannulated. In small infants (<2 Kg) only femoral vein is cannulated in order to avoid femoral artery complications.

After a complete pressure and oximetry assessment, the ductus is identified and measured from an aortogram in the descending aorta (Figure 7), exactly as for the other devices. As reported above, the lateral and the 45° right anterior oblique projections usually provide the best visualisation of the ductus and the relationships to the adjacent fixed landmarks. The minimum and maximum diameters as well as the length of the PDA are measured. Occasionally, having a large Mullins sheath across the duct during the aortogram may be helpful to outline the duct morphology better, particularly in adults. In adult patients, balloon sizing may be employed [1313. Pedra CA, Sanches SA, Fontes VF Percutaneous poclusion of the patent ductus arteriosus with the Amplatzer device for atrial septal defect. J Invas cardiol. 2003;15:413-17. ].

The long tubular ductus is more challenging to close and requires some technical modifications or even a different device. In adults with a large PDA, the duct length may be far in excess of the device length. For these reasons having the availability of a range of different devices or similar devices of different brands may give an advantage to the operator.

For the majority of PDAs, the device is chosen so that the larger diameter of the tubular part of the occluder is 1-2 mm larger than the narrowest diameter of the ductus (e.g., when the PDA narrowest diameter is 3.8 mm, a 6 mm stent device should be selected). This simple rule may be difficult to apply to large ducts, especially in adult patients because the ratio between the retention disc diameter and the distal device diameter becomes increasingly smaller with increasing device size. In these specific cases one or maybe two sizes bigger may need to be chosen. Another concern in adult patients is the ductus length.

The implantation of the device starts by advancing a 4 or 5 Fr multipurpose catheter from the venous side through the PDA and into the descending aorta (Figure 8). This catheter is then exchanged for the delivery sheath over a stiff 0.035” exchange guidewire. Some devices require a dedicated delivery system, in other cases a standard Mullins long sheath can be used. The size of the delivery system is reported in an accompanying manufacturer’s specification table. The appropriate device is soaked in flush solution. Some devices have to be loaded on the delivery cables, others are already attached to the delivery system. The device can be now stretched into the loader and flushed again. Under fluoroscopy monitoring, the device is advanced by pushing the delivery cable, and when it reaches the tip of the long sheath this is gently withdrawn to deploy the retention disc. The entire system (cable + long sheath) is then slowly withdrawn as the retention disc is seated in the aortic ampulla of the ductus (Figure 9). This position is well assessed on lateral projection either by comparing with the previous lateral aortogram using the tracheal air column as landmark or by the sensation of resistance to further withdrawal of the device. During this part of the procedure it is better to withdraw the pigtail left into the aorta just below the duct in order to avoid entrapment of the catheter by the retention disc.

Before deploying the rest of the device, it is advisable to push the pigtail up and repeating an aortogram, immediately adjacent and just distal to the aortic end of the ductus, to verify the correct position of the retention disc. When the position is correct, the delivery cable is fixed in place while the sheath alone is withdrawn out of the ductus and off the device, allowing the tapered tubular part of the device to extrude. A repeat descending aortogram is then performed ( Figure 10) to verify the device position in the ductus and the degree of occlusion. If the position is not satisfactory, the device can be withdrawn easily and safely into the sheath and repositioned or even withdrawn completely out of the body ( Figure 11). If the position is satisfactory, the device is easily released by the appropriate delivery system.

Special consideration in premature infants: Nowadays transcatheter closure of PDA in premature infants appears to be a safe and effective alternative to surgical ligation or after failure of pharmacological therapy or in cases where there is a contraindication to medical treatment. [66. Malekzadeh-Milani S, Akhavi A, Douchin S, Dauphin C, Chalard A, Mauran P, Bouvaist H, Bonnet D, Boudjemline Y Percutaneous closure of patent ductus arteriosus in premature infants: A French national survey. Catheter Cardiovasc Interv. 2020;95:71–77. ] In very small infants (under 2 Kg) it is essential to maintain eutermy throughout the procedure. The procedure can be done under echocardiography guidance from femoral vein in order to avoid femoral artery complication and renal injury. Hemodynamic data could be collected during the catheterization as soon as possible. The femoral vein is cannulated with a 4 Fr sheath. The implantation of the device starts by advancing a 4 Fr soft catheter (i.e. multipurpose glide catheter) and a soft coronary guidewire 0.014’’ from the venous side through the PDA and into the descending aorta ( Figure 8). This catheter is exchanged with a stiff 0.014’’ exchange guidewire. Over the wire can be advanced a 4 F delivery sheath (i.e. Amplatzer TorqVue LP catheter) into the descending aorta. Under echocardiography monitoring, the device is advanced by pushing the delivery cable, and when it reaches the tip of the long sheath this is gently withdrawn. If possible the distal retention disc and the entire device could be allocated into the tubular portion of the dutc in order to avoid aortic or pulmonary artery stenosis. Various devices were used to close PDA (i.e., Amplatzer Piccolo (St Jude Medical®, Minneapolis, Minnesota), coils and microvascular plug (MVP, Medtronic®, Minneapolis, Minnesota)). Devices were selected to be 1 mm larger than the PDA diameter and with a length as short as possible. Positioning and deployment of the device can be done using echocardiography and/or fluoroscopy without angiography. Before release, residual shunting and the presence of LPA or aortic obstruction were assessed. After the procedure, patients were transferred to the neonatal intensive care unit for close monitoring.

Complications

Embolisation

Embolisation is a rare complication but when it does happens, most of the time it is due to undersizing the device or positioning it too deeply within the ductus before its release. When the device is positioned too deep the retention disc may appear bulky, like a “bump”. In that case, although a complete occlusion is achieved, it is better to remove the device and reposition it one size bigger because it is probably undersized. Retrieval of an embolised device in the pulmonary artery is frequently difficult. Some device manufacturers recently proposed special catheters for device retrieval, however these catheters are device-specific.

For large and long PDAs a device with two retention discs can be used such as a muscular ventricular septal defect occluder (i.e Konar-MF VSD Occluder from Lifetech) or a self-centreing atrial septal defect occluder [1313. Pedra CA, Sanches SA, Fontes VF Percutaneous poclusion of the patent ductus arteriosus with the Amplatzer device for atrial septal defect. J Invas cardiol. 2003;15:413-17. ].

This is a situation encountered frequently in adult patients with a large conical PDA, which tends to be longer than the device length. Such large PDAs may be closed successfully with the largest (and longest) device available. However, the device can be pulled too deep within the duct and therefore the retention disc appears to be tenting the duct more than occluding it, causing a residual jet above it. In this situation a device with two retention discs would be more suitable.

CANDY-LIKE DEVICES

St Jude Medical proposed a second group of devices with a different geometry able to close challenging anatomy.The Amplatz Duct Occluder II is a self-expanding nitinol mesh device. Nitinol is a shape memory alloy of nickel and titanium. Each occluder is made of a multi-layered, flexible, fine nitinol wire mesh shaped into a cylindrical waist with retention discs on either end to secure it in the PDA ( Figure 12).

It has a “fabric-free” technology, which allows for a very low profile of the device and delivery system. Multi-layered mesh lobes create six planes of occlusion with full cross-sectional coverage for complete closure. Flexible mesh and dual articulations provide high conformability. The central waist is designed to fill the defect and the two retention discs are designed to be deployed on the arterial and venous sides of the defect. ( Figure 13).

These devices are available in 4 mm or 6 mm lengths with waist sizes of 3, 4, 5 and 6 mm in both lengths and each disc diameter is 6 mm greater than the waist size.

The wire mesh has 72 braided layers on its inner surface and 144 braided layers on its outer surface. In the 3 and 4 mm waist devices, there are 144 braided layers throughout. This device is suitable for patients weighing > 6 kg and > 6 months in age. The Amplatzer Duct Occluder II can treat all types of PDAs in the Krichenko classification system [1414. Jaspal D, Chessa M, Piazza L, Negura D, Micheletti A, Bussadori C, Butera G, Carminati M. Initial experience with the new Amplatzer Duct Occluder II. J Invasive Cardiol. 2009;21:401-5. ] from 2.5 mm to < 5.5 mm in diameter ( Figure 14). The “window-type” PDA is the only type that is unsuitable for closure with the ADO II. It is also contraindicated in PDAs measuring > 12 mm in length and > 5.5 mm in diameter on angiography. The device has a screw attachment for a delivery wire and radiopaque markers. The recommended sizes for the low-profile TorqVue® LP (AGA Medical Corporation [now part of Abbott, Nathan Lane North Plymouth, MN, USA]) braided and tapering delivery sheath are 4 Fr and 5 Fr. It has a flexible distal catheter segment that allows for easy approachability. The wire for device positioning and deployment is braided with a flexible nitinol tip. The device can be deployed, recaptured and redeployed for precise and secure placement. The same delivery system and cable are used for the venous or the arterial approach. When the delivery is made from the aortic side, the proximal disc tilts while the device is still attached to the cable but once it is released the device embraces the ductal ampulla provided tissue. The upcoming Amplatzer Piccolo Occluder previously called ADO II AS (The AMPLATZER Duct Occluder II Additional Sizes) ( Figure 12) is an occlusion device intended for duct types A, C, D, and E, for patients who weigh at least 6 kg and for patients older than 6 months of age. These devices will be available in 9 sizes: 3 waist sizes – 3, 4, and 5 mm, and 3 lengths – 2, 4, and 6 mm. It would be/is contraindicated for the following patients:

• who weigh less than 6 kg;
• younger than 6 months of age;
• with a window-type (B) patent ductus arteriosus (length of less than 3 mm);
• with a right-to-left shunt through the ductus;
• with an aortic ampulla diameter smaller than the diameter of the ductus at the pulmonary artery;
• with cardiac anomalies that require surgery or intervention;
• who have had more than 2 lower respiratory infections within the last year;
• with an active infection;
• with contraindications to anticoagulation treatment;
• with thrombus at the implant site;
• whose vasculature is not sufficient to reach the ductus with the specified catheter;
• with pulmonary hypertension with pulmonary vascular resistance of greater than 8;
• Wood units or an Rp/Rs of greater than 0.4;
• with a ductus longer than 8 mm (measured by angiography);
• with a ductus greater than 4 mm in diameter (measured by angiography).

How is this different from ADO II?

• smaller aortic and pulmonary disc diameters:
• ADO II minimum diameter is 9 mm (waist + 6 mm)
• ADO II AS minimum diameter 4 mm (waist +1-1.5 mm);
• greater recommended oversizing than ADO II;
• additional 2 mm device length.

At present, there are no guidelines regarding which PDAs should be closed preferentially from the venous or the arterial approach. The larger ducts, where operators felt the risk of device embolisation was high, may be occluded from the venous side. However, it is not possible to make specific recommendations. As experience with this device increases, it may be possible to create specific recommendations with regard to approach [1515. V. Bhole, P. Miller, C. Mehta,O. Stumper, Z. Reinhardt, J.V. De Giovanni. Clinical Evaluation of the New Amplatzer Duct Occluder II for Patent Arterial Duct Occlusion Cath. Cardiovasc Interv. 2009;74:762-9. ]. The shape of the duct itself does not directly influence the approach but, if it is considered difficult to cross the PDA from the venous side, the arterial approach may be used.

Amplatzer Piccolo Occluder has 9 different sizes, depending on the diameter (from 3 to 5 mm) and the length (from 2 to 6 mm) of the central waist. These devices have a smaller retention disc, ranging between 4 and 6.5 mm. This smaller device can be implanted with a dedicated 4 Fr catheter. As consequence, this device can be used also in very small patient; on the other hand, the main limitation for implantation of this device is the PDA size, because the narrowest PDA diameter have to be less than 3.5 mm. The device can be implanted from venous approach. It is not possible to check the device position by echocardiogram without arterial access. The device is already loaded on the delivery cable and can be deployed using a dedicated 4 Fr catheter or by using a 5 Fr guide catheter (internal diameter >0.040”).

Procedure

After a complete pressure and oximetry assessment, the ductus is identified and measured from an aortogram in the descending aorta exactly as for the other devices. A 4 or 5 Fr multipurpose catheter may be advanced from the venous side through the PDA into the descending aorta. A standard 150 cm (0.0035 inch) guidewire may be used to exchange the multipurpose catheter for either a 4 or a 5 Fr TorqVue LP delivery sheath that is advanced from the femoral vein into the descending aorta. An ADO II, 1–2 mm larger than the narrowest waist of the duct must be chosen.

The device is introduced into the delivery sheath and advanced under fluoroscopic guidance into the descending aorta, where the retention disc is deployed. Then the sheath and the delivery cable are pulled back until the retention disc is against the aortic end of the ampulla or in the ampulla. While gentle tension is maintained on the delivery cable, the introducer sheath is withdrawn into the pulmonary artery to deploy the waist of the ADO II, and then the second disc is deployed at the pulmonary end of the PDA. With the device still attached to the cable, a descending aortogram is recorded in the lateral projection to confirm the device’s position. Once proper device position is confirmed, the device is released by anticlockwise rotation of the delivery cable. A repeat descending aortogram is then recorded to check for residual shunting ( Figure 15).

Complications

In view of the presence of a retention disc on the pulmonary side, there is a risk of left pulmonary obstruction, especially in infants: this must be ruled out before release. The pulmonary artery angiogram in caudo-cranial angulation should define any pulmonary artery obstruction. The ADO II implantation usually does not exaggerate the LPA narrowing. Mild LPA obstruction has been reported [1616. Thanopoulos B, Eleftherakis N, Tzannos K, Stefandis C. Transcatheter closure of the patent ductus arteriosus using the new Amplatzer duct occuder: Initial clinical applications in children. Am Heart J. 2008;156:917el-917e6. ] in patients weighing 4 kg or less. Though technically it may be possible to use this device below the recommended weight of 6 kg, most practitioners adhere to the manufacturer’s recommendations since experience is limited with this device.

Aortic obstruction or watermelon seeding of central lobe is a possible complication. It is important to ascertain that the central lobe size is slightly bigger than the PDA mid-point and that it is deployed on the aortic side of narrowing irrespective of the approach: to achieve this, fine tuning of cable tension is required. Although the screw mechanism on the device sits prominently in the aorta when delivered from the artery, this does not seem to cause haemodynamic problems. Animal studies have shown effective endothelialisation of the whole device including this area [1717. Gruenstein DH, Bass JL. Experimental evaluation of a new articulated amplatzer ductal occluder device without fabric. Catheter Cardiovasc Interv. 2009;74:482-7. ].

Device embolisation is always a potential complication; the retention disc on either side of the waist should aid in stabilising the device.

Conclusions

The accepted standard treatment of the patent ductus arteriosus is currently transcatheter occlusion with one of the available devices. In all patients the present catheter occlusion procedures are superior to the trauma and morbidity of surgery for the correction of the PDA. Nowadays transcatheter closure of PDA in premature infants appears to be a safe and effective alternative to surgical ligation or after failure of pharmacological therapy or in cases where there is a contraindication to medical treatment.

PERSONAL PERSPECTIVE: MASSIMO CHESSA

In the next future, will be mandatory to compare the results of the PDA closure (transcatheter vs surgical) in small babies and pre-term babies. Smaller, softer, and more friendly devices will be welcomed, too.