Long-term outcome of patients with chronotropic incompetence after an acute myocardial infarction

Abstract

Background and aim. Chronotropic incompetence is risk marker of mortality in various populations, but its value in risk stratification of patients with a recent myocardial infarction (MI) is not known.Methods. A consecutive series of 494 patients with a recent MI underwent a symptom-limited bicycle ergometer test and echocardiography before discharge from the hospital. Cardiac death was the primary end-point and sudden cardiac death (SCD) the secondary end-point. Heart rate (HR) response to exercise was evaluated using maximal chronotropic response index (CRI = 100 × (peak HR – resting HR) × (220 – age – resting HR)−1).Results. During 8 years of follow-up, 40 patients (8.1%) experienced cardiac death, of whom 18 died suddenly (3.6%). Abnormal CRI (<39) was the most powerful predictor of the primary end-point with adjusted relative risk (RR) of 5.4 (95% CI 2.9–11.2; P < 0.001) and also a potent risk marker for SCD (adjusted RR 7.3; 95% CI 2.6–20.0; P < 0.001). Adjusted RR of decreased left ventricular ejection fraction (LVEF) (<45%) was 3.4 (95% CI 1.8–6.6; P < 0.001) for cardiac death. In the final predictive model of cardiac death, the removal of CRI decreased c-index from 0.817 to 0.778, whereas c-index was 0.791 after removal of LVEF.Conclusions. Chronotropic incompetence is a powerful predictor of cardiac mortality among post-MI patients.