Decreased Incidence of Ventricular Late Potentials after Successful Thrombolytic Therapy for Acute Myocardial Infarction

In some patients with acute myocardial infarction, low-amplitude potentials that prolong the QRS complex, termed "late potentials," can be recorded on a signal-averaged electrocardiogram. The presence of these late potentials is known to be associated with an increase in the risk of ventricular tachycardia and sudden death. Because patients with acute myocardial infarction who receive thrombolytic therapy have a reduced incidence of ventricular tachyarrhythmia and sudden death, we sought to determine whether such patients also have a decreased incidence of late potentials. We studied 106 patients less than 75 years of age who were admitted with a first myocardial infarction and in whom a signal-averaged electrocardiogram was recorded within 48 hours of admission. Within four hours of the onset of chest pain, tissue plasminogen activator (t-PA) was given to 44 patients, and 62 were treated conventionally. In the t-PA group, late potentials were recorded in 2 of 44 patients (5 percent), as compared with 14 of 62 (23 percent) in the conventionally treated group (P = 0.01). Furthermore, among the patients treated with t-PA, continued occlusion of the infarct-related artery was related to the presence of late potentials. In the t-PA group, late potentials were recorded within 24 hours of angiography in 2 of the 6 patients with an occluded infarct-related artery, as compared with none of the 38 patients with a patent infarct-related artery. Our data suggest that successful thrombolytic therapy is associated with a marked reduction in the incidence of late potentials on the signal-averaged electrocardiogram. Long-term follow-up will be required to determine whether this finding predicts a reduced incidence of subsequent ventricular tachyarrhythmia and sudden death. (N Engl J Med 1989; 321:712–6.) VENTRICULAR late potentials are bursts of low-amplitude potentials that prolong the QRS complex on a signal-averaged surface electrocardiogram. Their presence in patients with acute myocardial infarction has recently been described as a marker for the propensity to have both spontaneous and inducible ventricular tachyarrhythmia, as well as a predictor of sudden cardiac death. 1 , 7 These potentials have been demonstrated to be related to slow and inhomogeneous conduction within damaged cardiac tissue. 8 9 10 11 12 Thrombolytic therapy has been shown to reduce mortality after acute myocardial infarction 13 14 15 16 17 ; although this effect appears to be related primarily