Deleterious effects of incomplete myocardial reperfusion on ventricular arrhythmias

Incomplete myocardial reperfusion (that is, reperfusion limited to part of the ischemic zone) can occur because of segmental release of diffuse coronary spasm, proximal thrombolysis with persistent distal occlusion or reversible spasm with persistent distal thrombosis. However, it is unknown whether incomplete reperfusion increases the risk of ventricular tachycardia and fibrillation (because of greater dispersion of electrophysiologic properties) or decreases it (because of the smaller size of the reperfused zone). Thus, 56 open chest dogs underwent coronary artery occlusion (mid-left anterior descending coronary artery) followed 25 minutes later by reperfusion. Dogs were given complete reperfusion (control dogs: release of the proximal obstruction with no distal occlusion) or incomplete reperfusion (release of the proximal obstruction after ligation of the distal artery). Size of ischemic and reperfused zones was determined by postmortem dye perfusion. In control dogs, the ischemic zone (which coincided with the reperfused zone) was 34 ± 1% (mean ± standard error) of left ventricle; in dogs with incomplete reperfusion, the ischemic zone was similar to that of-control dogs (30 ± 1% of left ventricle, probability [p] = not significant), whereas the reperfused zone was smaller (20 ± 2% of left ventricle, p < 0.001). Coronary collateral flow was similar in the two groups. Incomplete reperfusion increased the overall incidence of ventricular tachycardia (18 of 20 versus 20 of 36 in control dogs, p < 0.01), the incidence of “sustained” (≥10 beats) ventricular tachycardia (15 of 20 versus 16 of 36 in control dogs, p < 0.05) and the incidence of ventricular fibrillation (14 of 20 versus 15 of 36, p < 0.05). Thus, despite smaller reperfused zones, incomplete reperfusion markedly increased both incidence and severity of ventricular arrhythmias, possibly by enhancement of reentrant circuits. It is concluded that the risk of malignant arrhythmias on release of coronary occlusion is significantly augmented by the persistence of ischemic myocardium within the reperfused region.