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Exercise-improved heart rate recovery increased cardiac survival in patients with recent MI
Hai J. Heart Rhythm. 2010;7:929-936.
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Exercise training improved the heart rate recovery of patients who had recently experienced MI, which subsequently increased cardiac survival, suggested new study data.
Researchers in this study enrolled 386 consecutive patients with recent MI into their cardiac rehabilitation program from 1996 to 2007. Patients underwent symptom-limited treadmill testing at baseline and after exercise training, and were prospectively followed in the outpatient clinic.
What researchers found was that treadmill testing led to improved heart rate recovery after eight weeks of exercise training (17.5 ± 10.0 beats/min to 19.0 ± 12.3 beats/min, P=.011). After a 79 ± 41 month follow-up, 40 (10.4%) patients died from cardiac events. Multivariate Cox regression analysis revealed the following independent predictors of cardiac death: diabetes (HR=2.28; 95% CI, 1.01–5.19), statin use (HR=0.36; 95% CI, 0.16–0.80), baseline resting heart rate ≥65 beats/min (HR=5.37; 95% CI, 1.33–21.61), post-training heart rate recovery <12 beats/min (HR=2.49, 95% CI, 1.10–5.63), left ventricular ejection fraction ≤30% (HR=4.70; 95% CI, 1.34–16.46), and exercise capacity of or less than four metabolic equivalents (HR 3.63, 95% CI 1.17–11.28). Furthermore, patients who did not improve heart rate recovery from <12 beats/min to ≥12 beats/min after exercise training had higher mortality (HR=6.2; 95% CI, 1.3–29.2).
These findings, wrote researchers, suggest that modulation of CV autonomic control with training may contribute to the long-term beneficial effects of a cardiac rehabilitation program. “Its clinical application as a therapeutic target for exercise prescription and medication titration needs to be further addressed in future studies,” they concluded. – By Brian Ellis
This is an interesting study. What they are showing is that patients who have early abnormal heart rate recovery after exercise testing, which is associated with adverse outcomes, had improvement in this measure with exercise training. We know that exercise training provides benefits, and improvement in heart rate recovery may be one of the mechanisms that explains some of the benefits, at least in a subset that has abnormal heart rate recovery.
– Nanette Wenger, MD
Cardiology
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