IS PRECONDITIONING BY NICOTINE RESPONSIBLE FOR THE BETTER PROGNOSIS IN SMOKERS WITH ACUTE MYOCARDIAL-INFARCTION

Cigarette smoking is a well-known risk factor for acute myocardial inf arction and sudden death. However, a history of smoking consistently h as been associated with better hospital outcome in patients with acute myocardial infarction. The mechanism for the better outcome in smoker s is not clear. It has been suggested that nicotine may have a ''preco nditioning-like'' effect. This study assesses whether nicotine attenua tes myocardial infarct size. Anesthetized rabbits were randomized to r eceive infusion of nicotine 80 mu g/kg (n = 13), or saline (n = 12) ov er 10 min. Twenty minutes after termination of infusion all rabbits un derwent 30 min of coronary artery occlusion and 4 h of reperfusion. Ri sk zone was assessed by blue dye and infarct size by tetrazolium stain ing. Nicotine did not affect regional myocardial blood flow 15 min aft er treatment, during occlusion or during reperfusion. Heart rate and m ean systemic blood pressure were similar between the groups. Nicotine serum levels during occlusion were 9.5-22.0 ng/ml in the treated group , which are comparable to levels found in human smokers. No difference s were found in the risk zone of nicotine compared to control rabbits (26 +/- 2% vs. 23 +/- 2% of the left ventricle, respectively). or infa rct size (31 +/- 5% vs. 37 +/- 4% of risk zone). Since no effect on in farct size was found, a third group receiving higher dose of nicotine, 320 mu g/kg (n = 6), was added. Infarct size was not different from t he control group (39 +/- 6% of risk zone). Nicotine, given intravenous ly before ischemic insult, does not protect the myocardium. A ''precon ditioning-like'' effect of nicotine is probably not the mechanism of r educed mortality in smoking patients with myocardial infarction.