Background: Despite concern that hypertension increases the risk for intracranial hemorrhage during thrombolysis for acute myocardial infarction, the exact nature of the risk remains unclear.
Objective: To assess the effects of previous hypertension and blood pressure at study entry on the outcomes of patients who had acute myocardial infarction and received thrombolysis.
Design: Randomized trial.
Setting: 1081 hospitals in 15 countries.
Patients: 41 021 patients who had myocardial infarction accompanied by ST-segment elevation and who presented to hospitals within 6 hours of symptom onset.
Intervention: One of four thrombolytic regimens.
Main Outcome Measures: Mortality, stroke subtypes, and death plus disabling stroke in patients with previous hypertension and as functions of blood pressure at entry. Logistic regression analysis of relations among blood pressure at entry, baseline characteristics, and treatment effects.
Results: The incidence of total stroke and intracranial hemorrhage increased as systolic blood pressure at entry increased and was particularly high for systolic pressures of about 175 mm Hg or more (incidence of total stroke, 3.4% compared with 1.17% for pressures between 100 and 124 mm Hg). Patients who had systolic blood pressure of 175 mm Hg or more at entry and who received accelerated alteplase therapy had a lower rate of death within 30 days (4.3% compared with 7.8%; P = 0.044) and a lower rate of death plus disabling stroke (4.9% compared with 8.9%; P = 0.031) than patients treated with streptokinase, despite having higher rates of total and hemorrhagic stroke (incidence of hemorrhagic stroke, 2.3% compared with 1.5%). Assumptions based on previous trials and rates of stroke from the GUSTO-I (Global Utilization of Streptokinase and t-PA for Occluded Coronary Arteries) trial suggest that in hypertensive patients with low risk for death from cardiac causes (no previous infarction, Killip class I), the risk-to-benefit ratio with thrombolysis is about unity, with about 13 lives saved per 1000 persons treated at the risk of about 13 intracranial hemorrhages.
Conclusions: Patients with myocardial infarction and very elevated blood pressure who have thrombolysis and patients with myocardial infarction who do not have elevated blood pressure have a similar risk for death, but the risk for stroke is higher in the former group. Future studies should assess 1) the risk-to-benefit ratio of thrombolysis in these patients, especially those at low risk for death from cardiac causes, and 2) whether decreasing elevated blood pressure before thrombolysis reduces the incidence of stroke without increasing mortality rates.