Physiologic assessment of the coronary collateral circulation in transplanted human hearts

Coronary arteries of transplanted hearts frequently develop a vasculopathy characterized by severe lumenal narrowing in the distal coronary arteries. It has been thought, on the basis of angiographic studies, that the coronary circulation of transplanted hearts with vasculopathy fails to develop collateral vessels normally. To determine the extent of the collateral circulation in transplanted hearts with a significant coronary stenosis, we measured an index of the collateral circulation, the coronary artery occlusion pressure, during single-vessel coronary angioplasty in seven patients with allograft vasculopathy and 18 patients with atherosclerotic disease who did not undergo transplantation. Aortic and coronary artery pressure distal to the stenosis in the epicardial artery were measured during balloon occlusion (≥45 seconds). Measurement variability for determination of coronary occlusion pressure was assessed by measuring occlusion pressure on two separate balloon inflations (n = 17). The severity of the dilated stenotic lesion was assessed with quantitative angiography (Reiber-PIE Data method). The indexes of stenosis severity were similar in coronary arteries of transplanted and native hearts. Coronary occlusion pressure measurements were highly reproducible (mean absolute difference between measurements, 1 ± 1 mm Hg, r = 0.98). Coronary occlusion pressure in transplanted hearts (32 ± 4 mm Hg) was nearly identical to that measured in coronary arteries of native hearts (29 ± 2 mm Hg). When vessels with total occlusion were excluded and corrections were made for minor differences in hemodynamics (heart rate and blood pressure) were made, the coronary occlusion pressure in transplanted hearts remained nearly identical to native hearts. These data suggest that, in the setting of allograft vasculopathy and a severe coronary stenosis, the coronary circulation of transplanted hearts is capable of normally developing collateral vessels.