Effects of acute cellular injury on coronary vascular reactivity in awake dogs.

Abstract

Effects of acute cellular injury on regional myocardial blood flow (RMBF) and coronary vascular reactivity were examined. Before myocardial infarction in 14 dogs, RMBF was measured using 7-10.mu. microspheres during the hyperemic response following a 60 s transient ischemic stimulation (TIS). Myocardial infarction was induced by complete occlusion for 2 h and then inflow to the injured area was re-established. RMBF was measured 4 h later during basal conditions, following a 60 s TIS and during infusion of adenosine, 1.0 mg/kg 1 min. Effects of acute cellular injury were examined by measuring RMBF in multiple myocardial samples, grouped according to extent of histologic necrosis. At 4 h after reperfusion, RMBF was decreased when infarction exceeded 50%. The decrements in flow were directly proportional to the extent of infarction. The vasculature was capable of delivering additional flow to the injured area since both TIS and adenosine infusion effected increases in RMBF in excess of 100% in each region of the ischemic zone. Blood flow responses to these stimuli fell in proportion to the extent of infarction. RMBF responses to TIS and adenosine infusion were comparable, indicating ischemia which effects irreversible myocardial injury also directly alters vasomotor properties of the intramural vasculature.