MYOCARDIAL BLOOD FLOW, ALTERNANS OF ST SEGMENT ELEVATION, CONDUCTION DELAY AND VENTRICUIAR ARRHYTHMIA DURING ACUTE MYOCARDIAL ISCHEMIA WITH AND WITHOUT RETROGRADE BLOOD FLOW IN CANINE HEARTS

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The technique of retrograde blood flow has been shown to decrease collateral flow into the ischemic myocardium, and to cause severe myocardial ischemia in dogs. Ischemia with retrograde blood flow in dogs is similar to ischemia in human hearts. Therefore, we examined the effect of retrograde blood flow on myocardial blood flow, ST segment elevation, alternans of ST segment elevation, conduction delay and ventricular arrhythmia in dogs. Sixty dogs were divided into two groups. In group A (N=32), the left anterior descending coronary artery was occluded for 10 min. In group B (n=28), ischemia was induced by the technique of retrograde blood flow for 10min. During ischemia, the myocardial blood flow at the ischemic zone measured by a H₂ gas clearance method was 11.21.6 in group A and 5.7±0.7ml/min/100g in group B (p<0.01). The maximal ST segment elevation was 13.6±1.9 in group A and 27.2±2.1mV in group B (p<0.001); the maximal alternans of ST segment elevation was 5.3±1.1 in group A and 10.1±1.4mV in group B (p<0.01); the maximal conduction delay was 51.6±8.4 in group A and 111.1±6.2 msec in group B (p<0.001); and the incidences of ventricular premature beats (>5/min), ventricular tachycardia and fibrillation were 34%, 41% and 22% in group A, and 68%, 79% and 25% in group B (p<0.01, p<0.01 and not significant, respectively). It is concluded that ischemia with retrograde blood flow can be used to examine occlusive and reperfusion ventricular arrhythmia in dogs. because the incidences of ventricular premature beats and ventricular tachycardia were high, but that of ventricular fibrillation was not high despite the severe ischemia.