Heterogeneity of reperfusion after reversible regional myocardial ischemia in a canine model

Variability of regional myocardial blood flow (RMBF) during reflow after 20 minutes of left anterior descending (LAD) coronary occlusion was measured by the radioactive microsphere technique in nine open-chest dogs. Preocclusion RMBF in the LAD territory was 0.89 ± 0.27 ml/min/gm. Twenty minutes of LAD occlusion resulted in uniform and severe ischemia (RMBF < 0.25 ml/min/gm). After 1 minute of reperfusion, RMBF in the LAD territory rose to 3.48 ± 1.88 ml/min/gm, and declined to 1.06 ± 0.29 ml/min/gm after 20 minutes of reperfusion. RMBF variance increased significantly from 0.046 preocclusion to 0.2857 after 1 minute of reperfusion (p < 0.01) and declining to 0.086 after 20 minutes of reperfusion. By contrast, RMBF variance analysis of myocardial segments from the nonischemic left circumflex territory exhibited no significant change throughout the experiment. In any given dog this heterogeneous reperfusion of previously ischemic tissue resulted in a disorganized topography of blood flow rates. Myocardium with relatively high regioal flow was intermingled with islands of tissue with relatively low blood flow. In conclusion, despite a relatively uniform and severe myocardial ischemic insult, the subsequent initial hyperemic response during reperfusion exhibits marked spatial heterogeneity. The juxtaposition of myocardial regions exposed to vastly differing rates of oxygen delivery and washout of toxic metabolites may set the stage for nonuniform recovery of myocardial function.