Determinants of coronary reserve in rats subjected to coronary artery ligation or aortic banding

OBJECTIVE: We investigated whether decreased coronary reserve in hearts after coronary artery ligation or in hearts from rats after aortic banding can be related to remodeling of resistance arteries. METHODS: Maximal coronary flow (absolute flow) and cardiac perfusion (flow corrected for heart weight) were determined in isolated, perfused rat hearts after adenosine or nitroprusside, at 3 and 8 weeks after coronary artery ligation or 4-5 weeks after aortic banding. Perivascular collagen and medial thickness of resistance arteries were determined by morphometry. RESULTS: maximal coronary flow of infarcted hearts had been restored to sham values at 3 weeks. Growth of cardiac muscle mass from 3 to 8 weeks exceeded the increase in maximal coronary flow, leading to a decreased perfusion at 8 weeks. A slight, transient increase in perivascular collagen, but no medial hypertrophy, was found after infarction. After aortic banding perivascular fibrosis and medial hypertrophy led to a decreased maximal coronary flow in both the hypertrophied left and the non-hypertrophied right ventricle. Consequently, perfusion of the left ventricle was most severely reduced. CONCLUSIONS: Reduced maximal perfusion after aortic banding is determined by both cardiac hypertrophy and vascular remodeling. In contrast, during infarction-induced remodeling, reduction of perfusion is not determined by vascular remodeling, but mainly by disproportional cardiac hypertrophy relative to vascular growth.