Alternation of ST segment and T wave in experimental acute myocardial ischemia

: Acute myocardial ischemia and reperfusion in 49 young pigs were produced by balloon occlusion of the left anterior descending coronary artery. Alternations of ST segment and T wave (STTA) were detected in 33 pigs during ischemia. They started at 30 seconds to 14 minutes (mean 5.4 +/- 4.1 minutes) after occlusion and maintained for 4.0 +/- 3.4 minutes. The start and end of STTA might be gradual or abrupt. Abrupt STTA provoked by ventricular premature beat (VPB), and might be reset by VPB and short run of non-sustained repetitive ventricular firing. In leads V1 and V4 simultaneously recorded, STTA showed concordant in most cases and the discordant alternation was transient STTA was a significant discriminator in identifying cases in whom ventricular fibrillation or tachcardia was inducible in acute myocardial ischemia (P < 0.01). We conclude that STTA may provide a non-invasion measure of cardiac electrical stability during acute myocardial ischemia.