The study infant will undergo cardiac catheterization and myocardial biopsy before pulmonary artery banding and at appropriate intervals during follow-up surveillance by the interventional cardiologist. Patients will be "listed" for heart transplantation, and rPAB will be applied in lieu of mechanical circulatory support or as an alternative to already existing mechanical circulatory support, in the form of extracorporeal mechanical oxygen (ECMO). Myocardial biopsies will be flash frozen for storage and eventual probing for cell type (mature or stem) as part of a separate study.
The addition of afterload rPAB to a normal-functioning right ventricle (in the setting of end-stage dilated cardiomyopathy) shifts the inter-ventricular septum toward the midline, thus significantly improving left ventricular geometry and function. It permits the infant or young child to operate from a much improved position on Starling's curve with gradual resolution of congestive heart failure and the potential for lethal ventricular dysrhythmia. An abundance of progenitor myocytes known to exist within the myocardium of this patient age group may then contribute to "permanent" left ventricular restoration.
A sternotomy incision is used for application of the rPAB. The band is tightened under echocardiographic control until the inter-ventricular septum becomes a midline structure. Myocardial function is augmented with inotropic and vasodilator agents. These agents are weaned off gradually over a period of 2-4 weeks. The infant is separated from mechanical ventilation within the first post-rPAB week, and enteric feeding is resumed. The infant is discharged on oral medications, and is kept under frequent clinical surveillance.
As the infant grows, the rPAB becomes relatively more obstructive to right ventricular outflow. Based on a finding of increasing right ventricular dilation, onset or worsening tricuspid valve regurgitation, or a gradual late increase in plasma B-type natriuretic peptide (BNP) levels, the band may be loosened in stages as a balloon catheter-based procedure. Band enlargement may be accomplished in stages, ultimately opting for a mild residual right ventricle-main pulmonary artery pressure gradient of 15-30 mmHg.
The infants' short- and long-term surveillance will include clinical examination, height, weight, cardiac catheterization, electrocardiogram, echocardiogram, chest x-ray, and plasma BNP levels.
