Sex, survival bias, and mortality following acute myocardial infarction.

Several though not all studies have found an up to 2-fold increase in 30-day mortality in women compared to men admitted to hospital for ST-elevation myocardial infarction (MI), even after adjustment for baseline variables. These data however do not take into account the pre-hospital period. Indeed, three large WHO MONICA reports that included out-of-hospital events found no significant gender difference in overall 28-day mortality from MI, with more men dying before reaching the hospital (presumably of ventricular tachyarrhythmias) and more women dying after hospital admission (presumably of heart failure). Women compared to men exhibit enhanced vagal activity, both under basal conditions and during angioplasty-induced coronary occlusion, and this may afford protection against malignant ventricular arrhythmias. Epidemiological data indicate that women dying of ischemic heart disease are less prone to sudden death than men. Taken together, the above findings suggest that, following acute MI, significant gender differences lie not so much in overall mortality, but in the timing and mechanisms of death.