ST segment reelevation after acute myocardial infarction: marked differences in the electrocardiographic pattern between early and late episodes

This study assesses the electrocardiographic (ECG) morphologic differences between early (<24 h) and late (>24 h) episodes of ST segment reelevation after acute myocardial infarction. We studied the records of 101 consecutive patients with acute myocardial infarction whose admission ECG demonstrated ST segment elevation with positive T waves, without pathological Q waves in the relevant leads, and without signs of bundle branch block or left ventricular hypertrophy. Thirty-five patients had 44 episodes of early ST segment reelevation, while 22 patients experienced 26 late episodes of ST segment reelevation. Seven patients experienced both early and late episodes. Early episodes of ST segment reelevation was seen more often after thrombolytic therapy: 43% (32 of 74 patients) versus 11% (3 of 27 patients) (P < 0.006). No differences were found in the incidence of late episodes between those who underwent (23%) or did not undergo (19%) thrombolytic therapy. Two patterns of ST segment elevation were distinguished. Pattern A with positive T waves, ST segment elevation (≥0.1 mV), but without distortion of the terminal portion of the QRS complex. Pattern B characterized by positive T waves, ST segment elevation (≥0.1 mV) with distortion of the terminal portion of the QRS complex. Each ECG was categorized according to these two patterns. The admission ECG pattern was A in 75 patients, and B in 26. No significant differences were found between patients with early, late, or no episodes of ST segment reelevation in the appearance of pattern A or B on admission. Pattern A was found in 32 episodes of ST reelevation, while pattern B was found in 38 episodes. Ten (23%) and 34 (77%) of the early episodes were of pattern A and B, respectively, while 22 (85%) and 4 (15%) of the late episodes were of pattern A and B, respectively (P < 0.000002). No relation was found between the ECG pattern on admission and the pattern recorded during episodes of ST reelevation. The differences in the morphologic pattern of ST segment reelevation between early and late episodes, shown in this study, may signify different pathophysiological mechanisms. There is a need to further characterize the different ECG patterns of ST reelevation after acute myocardial infarction, and to try to relate the differences to different pathophysiologic mechanisms of myocardial ischemia and injury.