Coronary hemodynamics in the transplanted human heart

Abstract

The basal features of the coronary circulation, including coronary reserve, were assessed in 12 nonrejecting heart transplant recipients and compared to similar data obtained in 10 innervated subjects. Coronary sinus blood flow (CSBF) was determined by thermodilution, and coronary reserve was measured as the increment in flow after maximal coronary vasodilatation induced by 10 mg intracoronary papaverine. Heart rate and mean aortic pressure were significantly higher in the transplanted group. Basally, transplanted patients showed lower coronary resistance (0.65 ± 0.12 vs 0.90 ± 0.24 mmHg/ml/minute, p < 0.01), higher CSBF (172 ± 24 vs 116 ± 31 ml/minute, p < 0.0001), similar myocardial oxygen consumption (15.3 ± 4.0 vs 13.6 ± 4.7 ml/minute, NS), and narrower myocardial arteriovenous oxygen difference (8.9 ± 2 vs 11.6 ± 2 ml/100 ml, p < 0.01). After papaverine, innervated subjects had a greater increase in CSBF (148 ± 40 vs 100 ± 37%, p < 0.01) and also a larger reduction in coronary resistance (59 ± 5.3 vs 48.7 ± 9%, p < 0.01). Maximum levels of CSBF attained were higher in transplanted patients (340 ± 60 vs 283 ± 68 ml/minute, p < 0.05), whereas minimum levels of coronary resistance were similar in both groups (0.33 ± 0.06 vs 0.36 ± 0.06 mmHg/ml/minute, NS). According to our results, nonrejecting heart transplant patients have decreased resting coronary resistance, with a subsequent increase in CSBF for a given myocardial oxygen consumption probably due to lack of adrenergic tone and increased aortic pressure. As a consequence, coronary reserve appears diminished, though maximal coronary flow attained after papaverine may be higher than in normal individuals, depending on a superior perfusion pressure.