Reduced risk of death at 28 days in patients taking a β blocker before admission to hospital with myocardial infarction

Abstract

Objective - To see whether patients taking an oral β blocker at the time of admission to hospital with myocardial infarction have a reduced risk of death at 28 days. Design - Retrospective analysis of data collected on patients admitted over four years. Setting - Community based study. Patients - 2430 Consecutive patients living in the Perth statistical division admitted to hospital with myocardial infarction during 1984-7. Main outcome measure - Survival at 28 days among patients taking a β blocker at onset of myocardial infarction. Results - Patients were grouped into those who were and were not taking a β blocker at the time of admission. Though patients taking a β blocker were older and more likely to have a history of myocardial infarction, angina, or hypertension, the overall mortality at 28 days was similar in the two groups. A logistic regression model used to adjust for factors predictive of cardiac death at 28 days confirmed that patients taking a β blocker at the time of admission had a significantly reduced risk of death (relative risk 0·50; 95% confidence interval 0·34 to 0·76). Though the incidence of fatal ventricular fibrillation was similar in the two groups, mean peak creatine kinase activity was significantly lower in the β blocker group. Conclusions - These data support the value of long term use of β blockers in patients at risk of myocardial infarction. They suggest that patients taking these agents before admission to hospital with myocardial infarction have a significant survival advantage at 28 days, which may be due to a reduction in infarct size.