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 in-hospital 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 (>/=65 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.