First myocardial infarction in smokers

In 484 patients with a first myocardial infarction 155 were smokers at the time of infarction. Their unadjusted survival was superior to the non-smokers at 3 months follow-up, with a relative risk of 0.36 (95% confidence interval 0.22-0.59). Major baseline differences existed between the two populations. When these inequalities were taken into account through a multivariate Cox regression the relative risk was increased to 0.55 (95% confidence interval 0.33-0.93), but was still significantly lower than in non-smokers (P = 0.017). No difference in rate of reinfarction was observed between the two populations. The smokers tended to have a 'less serious infarction' than the non-smokers. However, adding variables that accounted for this into the Cox model did not cancel the impact of smoking. From the results it is suggested that the reduced mortality in smokers is due to a thrombus occurring at an earlier stage of the coronary artery disease. Thus, at the time of infarction smokers' left ventricular function tends to be less affected, and this is reflected in the improved survival rate among smokers in the first months after an acute myocardial infarction.