Percutaneous Pulmonary Valve Implantation for RVOT Defects

C ongenital cardiac defects involving the right ventricular outflow tract (RVOT) require initial surgical interventions as early as the neonatal period. These defects may include severe pulmonic valve stenosis, pulmonary atresia with or without ventricular septal defect, tetralogy of Fallot, transposition of the great arteries, and truncus arteriosus. In addition, congenital aortic valve defects can be corrected by placing the patient’s own pulmonary valve into the aortic position and using a homograft or bovine jugular vein in the pulmonic position (Ross procedure). The initial surgical repair for these complex conditions, or repeated surgery for free pulmonary regurgitation, often includes the creation of an artificial right ventricle (RV)-to-main pulmonary artery (PA) connection (RV-PA conduit). Over time, these conduits are prone to develop valve dysfunction, leading to pulmonic regurgitation, stenosis, thrombosis, infections, and calcification. Such complications are not uncommon.1-4 There is clear evidence that pulmonary stenosis and regurgitation are associated with exercise intolerance, arrhythmias, heart failure, and an increased risk of sudden death.4 Therefore, treatment of the obstruction with balloon dilatation and/or stent placement has been performed. RV-PA conduit stenting has been proven to decrease RV pressures and, potentially, prolong conduit lifespan.5,6 Nevertheless, this treatment option comes at the expense of free pulmonary regurgitation. Significant pulmonic regurgitation may result in the same cycle of progressive RV dilatation, RV dysfunction, atrial and ventricular arrhythmias, and sudden cardiac death.4 Although the appropriate timing for pulmonary valve replacement is an area of controversy, it can halt (and may reverse) such unfavorable outcomes and lead to improved symptoms, restore RV function, and decrease the incidence of arrhythmias.7 However, this means that patients must undergo multiple open heart surgeries to reduce the hemodynamic burden on the RV. Patients may require three to five operations over a lifetime because the mean time to reoperation is approximately 10.3 years for xenografts and 16 years for homografts.8,9 Nevertheless, significant perioperative mortality exists as a result of advanced RV dysfunction in these patients. Reoperations are usually complex with mortality increasing with each reoperation.10 Delaying repeat surgeries because of their associated morbidity and mortality must be weighed against the increased risks associated with deteriorating RV function. The need for repeat surgeries in this patient population, coupled with the surgical risks of mortality and morbidity, makes a percutaneous procedure to replace an obstructed and/or regurgitant pulmonic valve an attractive alternative. In 2000, Bonhoeffer et al11,12 reported the first experimental and clinical human appliPercutaneous Pulmonary Valve Implantation for RVOT Defects