Evidence of ischemic preconditioning in patients experiencing first non-ST-segment elevation myocardial infarction (NSTEMI)

Background: Several studies have demonstrated the protective effects of preinfarction angina in Q wave myocardial infarction, implicating the role of ischemic preconditioning but this role remains uncertain in patients with a NSTEMI. Subendocardial viability in NSTEMI patients, is thought to be less dependent on collateral circulation and thus more likely to be protected by other mechanisms such as preconditioning. Methods: We have studied prospectively 40 patients with first NSTEMI and with angiographically proven poor or no collateral development and compared two groups; those with versus those without preinfarction angina. All in-hospital events, such as recurrent angina, congestive heart failure, arrhythmias and reinfarction were recorded. Serum markers of myocardial necrosis (CPK, CPK-MB, AST) and discharge QTc values were estimated. Results: Preconditioned patients suffered less recurrent angina (18 vs. 55% P=0.014), congestive heart failure (0 vs. 22%, P=0.02), arrhythmic events (0 vs. 27%, P=0.008) and had significant smaller values of mean peak CPK (381±152 vs. 859±496 I.U./l, P=0.0008), mean peak CPK-MB (45.5±24.6 vs. 105.2±87 I.U./l, P=0.01), mean peak AST (59.8±23.1 vs. 112.4±64.3 I.U./l, P=0.003) and QTc value at discharge (0.42±0.03 vs. 0.46±0.05 s, P=0.005) than patients without preconditioning. Multiple logistic regression analysis confirmed that the absence of preinfarction angina (relative risk 9.10, 95% CI 2.08–40.00, P=0.003) was a significant predictor of in-hospital complications. Conclusions: Preinfarction angina constitutes a strong clinical correlate to ischemic preconditioning in patients with first NSTEMI, offering serious protection, by improving in-hospital outcome and reducing infarct size.