Joint effect of physical activity and body mass index on mortality for acute myocardial infarction in the elderly: role of preinfarction angina as equivalent of ischemic preconditioning.

Background Preinfarction angina (PrA), clinical equivalent of ischemic preconditioning, confers protection against inhospital mortality for acute myocardial infarction (AMI) in adult but not in elderly patients. This study aims to examine the interaction between physical activity and body mass index (BMI) in preserving the cardioprotective effect of PrA in elderly patients with AMI. Design Elderly patients (Z65 years old) with AMI admitted to Coronary Care Unit. Methods Elderly patients with AMI were retrospectively stratified for the presence and absence of PrA, and for quartiles of BMI and physical activity. In-hospital outcomes (death, cardiogenic shock, and reinfarction and creatine kinase-MB peak) were evaluated. Results In-hospital mortality of 1014 elderly patients with AMI was 19.2% in those with PrA and 22.7% in those without (P = 0.18, NS). Mortality further decreased with increased physical activity and reduced BMI, a trend that was not observed in patients without PrA. When physical activity and BMI were considered together, lowest in-hospital mortality was observed in patients with highest physical activity and normal BMI (from 18.2 to 9.6%; P < 0.01) with the greatest reduction observed in patients with PrA (from 18.3 to 5.1%; P =0.02). Multivariate analysis showed that PrA did not exert a protective effect in all patients irrespective of physical activity and BMI. A protective role was, however, observed in patients with highest physical activity or normal BMI and reached a maximum protective role in patients who showed both highest physical activity and normal BMI [odds ratio =0.08; 95% confidence interval = 0.02–0.72; P < 0.01]. Conclusion The cardioprotective effect of PrA was preserved in elderly patients who showed the highest physical activity and a normal BMI.