Angina-induced protection against myocardial infarction in adult and elderly patients: a loss of preconditioning mechanism in the aging heart?

Objectives: The present study examined whether angina 48 h before myocardial infarction provides protection in adult and elderly patients.
Background: The mortality rate for coronary artery disease is greater in elderly than in young patients. In experimental studies, ischemic preconditioning affords an endogenous form of protection against ischemia-reperfusion injury in adult but not in senescent hearts. Angina before myocardial infarction, a clinical equivalent of experimental ischemic preconditioning, has a protective effect in adult patients. It is not known whether angina before myocardial infarction is also protective in aged patients.
Methods: We retrospectively verified whether antecedent angina within 48 h of myocardial infarction exerts a beneficial effect on in-hospital outcomes in adult (< 65 years old, n = 293) and elderly (> or = 65 years old, n = 210) patients.
Results: In-hospital death was more frequent in adult patients without than in those with previous angina (10% vs. 2.6%, p < 0.01), as were congestive heart failure or shock (10.7% vs. 3.3%, p < 0.02) and the combined end points (in-hospital death and congestive heart failure or shock) (20.7% vs. 5.9%, p < 0.0003). In contrast, the presence or absence of previous angina before acute myocardial infarction in elderly patients seems not to influence the incidence of in-hospital death (14.4% vs. 15.2%, p = 0.97), congestive heart failure or shock (11.0% vs. 11.9%, p = 0.99) and the combined end points (25.4% vs. 27.1%, p = 0.89). Logistic regression analysis models for in-hospital end points show that previous angina is a positive predictor in adult but not in elderly patients.
Conclusions: The presence of angina before acute myocardial infarction seems to confer protection against in-hospital outcomes in adults; this effect seemed to be less obvious in elderly patients. This study suggests that the protection afforded by angina in adult patients may involve the occurrence of ischemic preconditioning, which seems to be lost in senescent patients.