Temporal dependence of coronary collateral development

Objective: Previous evidence suggests that episodes of myocardial ischemia of sufficient duration and intensity are required to produce coronary collateral development during repetitive coronary occlusion. This investigation tested the hypothesis that coronary collateral development is also temporal-dependent, Methods: Chronically instrumented dogs (n = 16) were subjected to brief(2 min) left anterior descending coronary artery (LAD) occlusions, once every hour, 8 h a day, for 3 weeks or once every how, 24 h a day for 1 week. Collateral perfusion (radioactive microspheres), LAD contractile function (ultrasonic crystals), and post-occlusive now debt repayment (LAD flow probe) were measured during occlusions 1, 55, 105, and 155. Results: Increases (P < 0.05) in subendocardial collateral blood flow to ischemic myocardium, progressive normalization of contractile function during LAD occlusion, and successive reduction in flow debt repayment were observed in dogs receiving occlusions over 3 weeks. In contrast, dogs receiving the same number of coronary occlusions over 1 week demonstrated minimal increases in collateral blood flow, persistent regional contractile dysfunction, and sustained flow debt repayment. Conclusions: The results demonstrate that LAD collateral development in response to repetitive coronary occlusion requires sufficient time for growth adaptation of the collateral circulation to occur.