Comparison between regional myocardial perfusion reserve and coronary flow reserve in the canine heart

Diameter stenosis and flow reserve are indices of morphologicaland functional severity of coronary artery stenosis. Flow reservecan be determined at coronary arterial or at myocardial level.In the presence of functional collateral circulation, coronaryflow reserve and myocardial perfusion reserve may differ. We studied coronary flow, coronary flow reserve and myocardialperfusion reserve in an open chest dog model with intact collateralcirculation, before and after induction of coronary artery stenosis.Coronary flow was determined with perivascular ultrasonic flowprobes and myocardial perfusion reserve from digital angiographicimages, in the stenotic as well as the adjacent non-stenoticcoronary arteries. Before induction of a stenosis, a significant correlation existedbetween coronary flow reserve and myocardial perfusion reserveof the left anterior descending (r=0.59; P<0.005) and theleft circumflex arteries (r=0.84, P<0.005). In stenotic arteries,coronary flow reserve and myocardial perfusion reserve decreasedsignificantly (P<0.005), but in the adjacent non-stenoticarteries coronary flow reserve was not affected Myocardial perfusionreserve in the non-stenotic adjacent left anterior descendingartery decreased significantly (P<0.05) and no correlationwas found between coronary flow reserve and myocardial perfusionreserve, whereas in the adjacent non-stenotic left circumflexartery there was no statistically significant decrease (4.1± 1.6 3.5 ± 1.4) but there was a good correlationbetween coronary flow reserve and myocardial perfusion reserve(r=0.85; P<0.005). This study demonstrates that, in the presence of a stenosisand functioning collateral circulation, coronary flow reserveis not a reliable predictor of myocardial perfusion reserve;both parameters provide mutually complementary information.