Methods:

A total of 96 HT recipients, including seven pediatric patients (12-19 years old), were randomized to ramipril or placebo in this prospective, multicenter, randomized, double-blind, placebo-controlled trial. Within 8 weeks of HT, the study cohort underwent coronary angiography, endothelial function testing, measurement of fractional flow reserve (FFR), coronary flow reserve (CFR) and the index of microcirculatory resistance (IMR), and intravascular ultrasound (IVUS) of the left anterior descending coronary artery. At 1 year, the invasive assessment was repeated. Circulating endothelial progenitor cells (EPCs) were quantified at baseline and 1 year. The primary endpoint of the study was the difference in plaque volume, as assessed by IVUS examination of the LAD at 1 year between those in the ramipril and placebo groups. The investigators assumed that with a plaque volume at 1 year of 170 mm³ in the control arm and a plaque volume of 133 mm³ in the ramipril-treated patients with a standard deviation of 60 mm³, a sample size of 43 was required in each arm to have 80% power to detect a significant difference. Key secondary endpoints included the safety and efficacy of ramipril administration early after HT, the effect of ramipril on coronary endothelial function, coronary physiology, and circulating endothelial progenitor cell number.