HEART RATE RECOVERY AND CARDIAC REHABILITATION

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Exercise-based cardiac rehabilitation has been shown to reduce mortality and subsequent cardiac events in patients with coronary artery disease. Although the exact mechanism by which exercise reduces mortality is unclear, one hypothesis invokes the effect of exercise on autonomic tone. Recently, heart rate recovery immediately after exercise (defined as the decrease in heart rate from peak exercise to one minute into recovery) was shown to be a powerful predictor of all cause mortality. Values below twelve beats per minute were associated with a marked increase in the risk of death. Heart rate recovery is an easily measured parameter to assess autonomic tone. Although exercise training has been shown to modify the sympathovagal control of heart rate towards an increase in parasympathetic tone, no evaluation of the effect of cardiac rehabilitation on heart rate recovery has been demonstrated previously. This study aims to prospectively evaluate the effect of cardiac rehabilitation on heart rate recovery on follow-up exercise testing in patients with coronary artery disease. It also aims to evaluate the mechanism for the observed change in heart rate recovery in these patients by using parasympathetic blockade during the exercise test. If heart rate recovery does improve following a structured exercise training program, then this parameter may be useful as an outcome measure in an outpatient cardiac rehabilitation facility, and perhaps help to identify patients with increased risk for subsequent cardiac events.