Objectives: This study examined whether previous rejection episodes may have deleterious effects on coronary vascular reserve of heart transplant recipients months after transplantation.

Background: Coronary reserve has been demonstrated to be within the normal range in long-term transplant patients without previous episodes of rejection. Conversely, acute rejection is associated with a dramatic reduction of coronary reserve, which is rapidly restored after therapy.

Methods: Coronary flow velocity was measured by intracoronary Doppler catheter before and after a maximally vasodilating dose of intracoronary papaverine in 16 control subjects and in 59 transplant patients classified into three groups with respect to time after transplantation: 1 to 6 months (group 1, n = 17), 7 to 18 months (group 2, n = 22) and > 18 months (group 3, n = 20). Coronary vascular reserve was evaluated through peak/rest coronary flow velocity ratio and minimal coronary vascular resistance index. All patients had normal findings on left ventricular angiography and coronary arteriography and a normal left ventricular mass.

Results: Arterial pressure was normal in all groups. Heart rate in the three groups of transplant patients, mean aortic pressure in groups 1 and 2, left ventricular systolic pressure in group 2 and rate-pressure product in groups 1 and 2 were higher than in control subjects. Average number of rejection episodes per patient was similar in the three groups of patients (group 1, 2.4 +/- 1.4; group 2, 2.5 +/- 1.9, and group 3, 2.1 +/- 1.3). Results showed no difference between each group of transplant patients and control subjects for peak/rest coronary flow velocity ratio (control subjects, 5.2 +/- 0.8; group 1, 5.3 +/- 1.5; group 2, 4.9 +/- 1.2, and group 3, 4.4 +/- 1.6) and for minimal coronary vascular resistance index (control subjects, 0.18 +/- 0.03; group 1, 0.18 +/- 0.04; group 2, 0.20 +/- 0.06, group 3, 0.23 +/- 0.11). In addition, patients with zero or one rejection episode had similar values of peak/rest coronary flow velocity ratio and minimal coronary vascular resistance index (4.3 +/- 1.3 and 0.23 +/- 0.10, respectively, n = 22) as did those with one or two rejection episodes (5.1 +/- 1.5 and 0.19 +/- 0.07, respectively, n = 24), and those with four or more episodes (5.2 +/- 1.4 and 0.19 +/- 0.05, respectively, n = 13).

Conclusions: This study showed that coronary vascular reserve remains within normal range and is independent from the number of previous episodes of rejection until late after transplantation in human heart transplant patients with angiographically normal coronary arteries.