 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. 