Objectives: We examined the impact of thrombolytic therapy and the prognosis of patients with non-Q wave myocardial infarction in a randomized placebo-controlled trial known as the Late Assessment of Thrombolytic Efficacy (LATE) study.
Background: Patients with non-Q wave as compared with Q wave myocardial infarction in the era before thrombolytic therapy were traditionally thought to have a higher rate of reinfarction and death between hospital discharge and 1 year such that the overall prognosis for outcome at 1 year was similar in the two groups.
Methods: The study patients began treatment with either recombinant tissue-type plasminogen activator (rt-PA) or matching placebo, 6 to 24 h after the onset of chest pain. Post hoc analysis of mortality and reinfarction was carried out by comparing rt-PA and placebo in various subsets of patients based on the presenting electrocardiogram (ECG) and the evolution of the ECG with respect to the development of Q waves.
Results: Among 5,711 participants, 4,759 had a confirmed myocardial infarction, including 1,309 classified as having a non-Q wave infarction at hospital discharge. Irrespective of treatment assignment, all patients with non-Q wave versus Q wave infarction had a lower 1-year mortality rate (13.3% vs. 17.1%, p = 0.001) and a similar 1-year reinfarction rate (8.6% vs. 7.9%, p = 0.7). Of the 4,759 patients with confirmed myocardial infarction, 2,973 presented with ST segment elevation or bundle branch block, 528 with ST depression and 1,258 with neither ST elevation nor depression. No overall benefit from rt-PA versus placebo with respect to mortality rate at 1 year was seen among patients presenting with ST elevation (21.2% vs. 22.4%, p = 0.5 [90% power to detect 20% relative difference]). Patients with ST elevation who were treated with rt-PA versus placebo <3 h after hospital admission had a lower mortality rate at 1 year (15.8% vs. 19.6%, p = 0.028) than did those treated after 3 h (17.6% vs. 13.0%, p = 0.055). Patients presenting initially with ST depression >2 mm had significant benefit from treatment with rt-PA with respect to 1 year mortality rate (20.1% vs. 31.9%, p = 0.006).
Conclusions: Patients with non-Q wave myocardial infarction constitute a heterogeneous group of patients. Although the observations presented here are limited by post hoc analysis, it is apparent that patients classified as having a non-Q wave infarction after thrombolytic therapy have a better prognosis than do those given placebo. Late admission of thrombolytic therapy (after 6 h) may also be beneficial in patients presenting with ST depression >2 mm and confirmed myocardial infarction. These hypotheses require prospective testing in a larger number of patients.