BACKGROUND The aim of this study was to investigate coronary compliance in patients early and 71.8 weeks after orthotopic heart transplantation. METHODS Thirty patients (mean age 51.4 years, women n = 6) underwent coronary angiography early after orthotopic heart transplantation (mean interval 11.6 +/- 5.5 weeks), by which time 12 recipients had already been treated for episodes of rejection. A total of 153 different coronary segments were investigated using a mechanical 30 MHz intravascular ultrasound system. In all segments, the intimal index and the circumferential extension of the vessel wall, which had a three-layered appearance, were assessed. Systolic-diastolic changes in area, and pressure with respect to vessel wall area, were used to study normalized compliance. All measurements were repeated in a subgroup of 13 patients 71.8 +/- 10.7 weeks after transplantation. RESULTS At the first investigation, the mean intimal index of all estimated cross-sectional areas was 0.07 +/- 0.10. The mean circumferential extension of the 'three-layered' coronary vessel wall was 74 degrees +/- 101 degrees. No correlation could be found between normalized compliance and the intimal index (r = -0.322, P < 0.001) or between normalized compliance and the circumferential extension of the three-layered vessel wall (r = -0.362, P < 0.001). Donor age did not correlate with normalized compliance either (r = -0.515, P = 0.004). In 12 patients with proven rejection periods before the first investigation, normalized compliance was significantly lower (1.76 +/- 0.81 mmHg-1) than in those without rejection (2.95 +/- 1.22 mmHg-1, P = 0.005). Both the intimal index and the circumferential extension of the three-layered architecture of the vessel wall were significantly higher in recipients with rejection periods. A comparison of the subgroup of 13 recipients between first and second investigation showed that the intimal index increased slightly from 0.03 +/- 0.03 to 0.09 +/- 0.13 (ns) 71.8 weeks after transplantation, but that normalized compliance did not differ significantly between the first and the follow-up investigation. CONCLUSIONS Early after orthotopic heart transplantation, normalized compliance does not correlate with donor age or the extent of atherosclerotic vessel alterations identifiable by intravascular ultrasound. Early rejection periods are associated with reduced coronary arterial compliance. Using intravascular ultrasound, this adverse functional effect on arterial compliance can be observed together with an increase in the intimal index.