Further elevation of the ST segment during the first hour of thrombolysis. A possible early marker of reperfusion.

OBJECTIVES

To evaluate the clinical implications of early electrocardiographic changes during thrombolysis in a randomized study in patients with an acute myocardial infarction.

BACKGROUND

Re-elevation of a rapidly resolving ST segment during thrombolysis is currently interpreted as a sign of re-occlusion, but a further elevation at very early stages of lytic therapy may not necessarily have the same implications.

METHODS

In 214 patients with a first transmural acute myocardial infarction of < or = 4 h randomized to fibrinolytic (streptokinase group, n: 110) vs non fibrinolytic medical therapy (control group, n: 104), a standard 12 lead ECG was continuously recorded during the first 60 min and at 2, 4, 10, 16 and 24 h. Serial enzymes were measured during 72 h, and in 156 patients (73%) a coronary angiogram was performed at 10-15 days.

RESULTS

Within the first 20-40 min there was an additional ST segment elevation in 50 patients (45%) from the streptokinase group and in 19 from control group (18%) (P < 0.0001) but the increment was greater in the streptokinase group (1.2 +/- 1.4 vs 0.3 +/- 1.4 mm, P < 0.0001). In the streptokinase group, the interval from onset of pain to peak creatine kinase MB was shorter in patients with additional ST segment elevation than in those without it (699 +/- 193 vs 856 +/- 299 min, P < 0.01). Moreover, in-hospital mortality tended to be lower in patients whose ST segment was elevated than in those without such elevation (2150, 4%, vs 6160, 10%). Incidence of recanalization was high but comparable in these two subsets. In recanalized patients, with or without additional ST segment elevation, the ST segment declined significantly at 1 h (-1.0 +/- 1.7, P < 0.001, vs 0.1 +/- 1.5 mm, ns).

CONCLUSIONS

Additional ST segment elevation is frequently observed during the first hour of intravenous thrombolysis with streptokinase. Its' association with a subsequent early decline of ST elevation, reduced mortality, a shorter time interval to peak creatine kinase, and a high rate of late recanalization, suggest that in some patients it is one of the earliest markers of reperfusion.