Additional elevation of the ST segment: a possible early electrocardiographic marker of experimental myocardial reperfusion

OBJECTIVE: To analyze the early electrocardiographic changes during experimental coronary reperfusion after 1 to 4 h of coronary occlusion. METHODS: Recordings of epicardial and endocardial DC electrograms were performed in 35 open-chest pigs during coronary occlusions of 1 to 4 h duration followed by 1 h of reperfusion. RESULTS: During occlusion, maximal ST segment elevation was reached between min 10 and 30 which was followed by and a steady decline. During the first 30 min of reperfusion, however, there was a further elevation of the ST segment with a peak at 5 min. Thus, values at the end of occlusion and at 5 min of reperfusion were: (a) group with 1 h occlusion (n = 11), 15.5 +/- 7 and 37.4 +/- 11.4 mm, P < 0.005; (b) group with 2 h occlusion (n = 6), 10.2 +/- 4 and 24.7 +/- 9.4 mm, P < 0.03; (c) group with 3 h occlusion (n = 6), 7.5 +/- 3 and 16.8 +/- 5.6 mm, P < 0.03; and (d) group with 4 h occlusion (n = 12), 6.4 +/- 2.4 and 17.0 +/- 8.9 mm, P < 0.01. In 9 animals from the group with 1 h occlusion, a second cycle of 1 h occlusion and reperfusion also showed re-elevation of ST segment during reperfusion, although to a lesser extent than the first one (from 10.0 +/- 4.9 to 16.3 +/- 7.1 mm, P < 0.01). CONCLUSIONS: Thus, our findings provide experimental evidence of an additional and paradoxical ST segment elevation as the earliest electrocardiographic sign of coronary reperfusion after 1 to 4 h of coronary occlusion. These observations may help to improve the interpretation of early electrocardiographic changes during thrombolysis in acute myocardial infarction.