Acute myocardial infarction in women: survival analysis in first six months.

OBJECTIVE

To examine the influence that being female has on the outcome of acute myocardial infarction.

DESIGN

Observational follow up study.

SETTING

London district general hospital.

PATIENTS

216 women and 607 men with acute myocardial infarction admitted to a coronary care unit from 1 January 1988 to 31 December 1992.

MAIN OUTCOME MEASURES

All cause mortality and recurrent ischaemic events in the first six months.

RESULTS

Event free survival (95% confidence interval) at six months was 63.3% (56.3% to 69.4%) in women and 76.1% (72.4% to 79.4%) in men, P < 0.001. The difference was confined to the first 30 days but thereafter the hazard plots for women and men converged, with reduction of the hazard ratio from 2.36 (1.70 to 3.27) to 0.81 (0.44 to 1.48). Women were older, but their excess risk persisted after adjustment for age, other baseline variables, and indices of severity of infarction (hazard ratio 1.53 (1.09 to 2.15), P = 0.015). Women tended to be treated with thrombolysis less commonly than men but the difference was small. Substantially fewer women than men, however, were discharged taking beta blockers (23.3% v 41.4%, P < 0.001), and although additional adjustment for discharge treatment did not further reduce the point estimate of the hazard ratio (1.84 (0.89-3.83)), the 95% confidence interval was wide and statistical significance was lost.

CONCLUSIONS

Women with acute myocardial infarction have a worse prognosis than men but the excess risk is confined to the first 30 days and is only partly explained by age and other baseline variables. The tendency for women to receive less vigorous treatment than men must be remedied before gender can be considered to be an independent determinant of risk.