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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.
Acknowledgements
Jari Tapanainen, MD, PhD, Jari Laukkanen, MD, PhD, Pirkko Huikuri, RN, Päivi Karjalainen, RN, and Ms Anne Lehtinen are sincerely acknowledged. The authors appreciate the technical support received from Heart Signal Co. (Oulu, Finland).
Declaration of interest: This study was supported by grants from the Research Council for Health, Academy of Finland (Helsinki, Finland), the Finnish Foundation of Cardiovascular Research (Helsinki, Finland), the Finnish Technology Development Centre (Tekes, Helsinki, Finland), and the Sigrid Juselius Foundation (Helsinki, Finland). The authors declare no other conflicts of interest.