Percutaneous pulmonary valve replacement: a new development in the lifetime strategy for patients with congenital heart disease

Advances in congenital heart surgery over the past few decades have led to increasing numbers of long-term survivors, and there are now as many adults with congenital heart disease as children. In the Netherlands the total number of patients with congenital heart disease is presently estimated to be around 50,000. The current generation of patients with repaired congenital heart disease, however, is exposed to increasing reintervention rates. Recognition of the deleterious long-term effects of the residual consequences of early repair has also contributed to a more aggressive surgical strategy. The interventional approach to the management of congenital heart disease is becoming increasingly recognised as the preferred treatment option for a wide number of congenital cardiac conditions. Nonsurgical cardiac valve replacement is one of the more exciting developments in the field of interventional cardiology. In this issue of the Netherlands Heart Journal an illustrative case report is presented of a percutaneous pulmonary valve replacement.¹

Percutaneous valve therapy developed initially with aortic valve replacement, as described by Anderson et al.² The authors demonstrated that percutaneous implantation of a stent-mounted bioprosthetic valve was feasible. Soon after, in 2003, Bonhoeffer et al. reported the use of a stent-mounted bioprosthesis for pulmonary replacement. ³ Pulmonary valve replacement (PVR) with this percutaneous approach has been remarkably successful. Currently, over 200 patients have been treated with only a single procedure-related mortality and good results. Percutaneous PVR now uses a bovine jugular venous valve sutured inside a balloon-expandable stent. Several congenital heart diseases involving the right ventricular outflow tract (RVOT) require surgical repair in early childhood. These procedures often require further revision of the RVOT at a later stage. Tetralogy of Fallot and its subtypes remain the commonest defects in this category. Pulmonary regurgitation, patch aneurysm and valvar or conduit stenosis encompass many of the late complications seen following early intracardiac repair. Long-term follow-up has revealed the detrimental haemodynamic effects on regurgitation of the right and left ventricular function. Atrial arrhythmias, heart failure, prolongation of the QRS duration with increased risk of malignant ventricular arrhythmias and sudden death are all linked to pulmonary regurgitation during late follow-up after tetralogy of Fallot repair. Preservation or restoration of pulmonary valve competence has resulted in improvement of right ventricular function, incidence of arrhythmias and exercise capacity.⁴

The optimal timing of pulmonary valve replacement in these patients remains controversial. When an early PVR is advocated, an important issue is the need for future reoperations for a failing homograft, the most commonly used type of valve replacement. The decrease in right ventricular volumes after PVR has to be weighed against the risk of subsequent homograft failure. In a recent nationwide study in the Netherlands, 53% of the patients had a significant homograft stenosis or regurgitation within ten years of PVR.⁵ Following the current guidelines, the onset of symptoms, progressive RV dilation, progressive tricuspid valve regurgitation or diminishing exercise tolerance are indications for pulmonary valve replacement.

Despite the fact that surgical pulmonary valve replacement can be performed with very low mortality, patients are reluctant to have reoperations. The number of reoperations may become substantial when patients receive their first PVR at a relatively young age. The risks of reoperations, including bleeding and infection, increase with the number of previous conduit implantations.

Transcatheter interventions for pulmonary valve replacement are less invasive, avoid the risks associated with cardiopulmonary bypass, avoid the risks of bleeding and infection and might reduce the costs by avoiding postoperative intensive care. After a series of successful animal experiments to show the feasibility, safety, and efficacy of this technique and device, human implantation was performed in patients with pulmonary valve dysfunction. The patient selection for percutaneous PVR was crucial to the success of this technique. The homograft provides an excellent bed for implantation of a stented valve. In most cases, homograft deterioration provides a combination of stenosis and regurgitation. The stenotic component is helpful for creating an implantation point for the valve, which leads to successful anchoring. In contrast, patients with a native outflow tract with repair of tetralogy of Fallot involving only a valvotomy or valvectomy may not provide a very discrete implantation point at the site of the pulmonary valve annulus. In many Fallot patients the right ventricular outflow tract appears to be dilated or may form part of a right ventricular outflow tract aneurysm. In a recent Dutch study, the RV outflow tract was considered enlarged (>20 mm/m²) in 65% (26/40) of Fallot patients undergoing surgical PVR.⁶ These are the most unfavourable outflow tracts for transcatheter techniques with currently available devices. The dimensions of the outflow tract do not provide any secure anchorage to the valve-stent assembly. MRI is an excellent technique for investigating the form and function of the RVOT and the consequences of its dysfunction on the right ventricle. It provides excellent images of the RVOT and provides accurate quantitative information on RV and LV volumes, ejection fraction and pulmonary regurgitation fraction.⁷

The currently available device is not suitable for use in patients with outflow tracts >22 mm. On the other hand, a small conduit <16 mm, which cannot be dilated to the diameter of the device, will lead to an incompletely expanded valve-stent assembly. Undilatable stenosis remains another problem with severely calcified homografts with extrinsic constraints due to the retrosternal position. A transcatheter course through an extra-anatomic conduit can be difficult, especially in the presence of severe stenosis and calcification, as has been demonstrated in the case presented in this issue.¹

Transcatheter implantation of pulmonary valves is the first clinical experience for nonsurgical management of valvular regurgitation. It has been shown to be feasible and safe in selected patients. Homografts between 16 and 22 mm, with a stenosis length <5 mm, would form the most suitable outflow tracts for percutaneous pulmonary valve implantation. There are still various unanswered questions about the durability of this valve in the long term. However, sequential percutaneous pulmonary valve implantation is feasible and could delay the need for surgery, which still remains a viable option for patients with valvular dysfunction. The early evidence indicates that percutaneous pulmonary valve replacement offers a promising alternative to the conventional surgical strategy. At present, it is not suitable for all patients and does not address the problems of RVOT patch aneurysm or subvalvar hypertrophied muscle bundles. With more experience and the results of long-term follow-up, nonsurgical pulmonary valve implantation may expand the boundaries of PVR in patients with pulmonary regurgitation. However, the management of these patients requires a lifetime strategy with cooperation between the cardiologist, the paediatric cardiologist and the surgeon. Concentration of these new treatment options in specialised centres is required for optimal results. At present, a percutaneous stent-valve prothesis is CE marked for use in patients up to the age of 18 years. This will undoubtedly be extended to adult patients in the near future. CAHAL, the Centre for Congenital Heart Disease Amsterdam-Leiden, represents a close collaboration between three large university hospitals – Academic Medical Centre (AMC), VU University Medical Centre (VUMC) and Leiden University Medical Centre (LUMC) and serves as a good example to show that by combining skills and expertise a large volume centre can be created. After a process of joint discussion and decision-making, paediatric cardiac surgery and percutaneous interventions are – by formal agreement – mostly concentrated at LUMC, while cardiac surgery and percutaneous interventions for adult patients with congenital heart disease are mainly located at AMC.⁸ In this way, larger numbers within a solid infrastructure and specific facilities may lead to increased experience and optimal results of treatment.