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03-10-2011 | Article

Cardiac rehab helps normalize HRR, cuts mortality

Abstract

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MedWire News: Cardiac rehabilitation improves abnormal heart rate recovery (HRR) after exercise, thereby reducing mortality, a study in Circulation has shown.

"The beneficial autonomic effect of exercise training, specifically enhanced vagal reactivation, suggests a plausible explanation as to why exercise training may favorably improve HRR," write Leslie Cho (Cleveland Clinic, Ohio, USA) and co-authors.

Abnormal HRR is an established prognostic marker that is independent of functional capacity, ischemia, or coronary artery disease. In the largest study of its kind to date, Cho and colleagues examined the feasibility of reversing abnormal HRR through structured exercise training, and the impact on mortality.

They recruited 1070 consecutive patients and assessed them using symptom-limited exercise electrocardiography before and after completion of a "phase 2" cardiac rehabilitation program.

The program comprised a highly structured, physician-monitored environment in which patients followed a specific exercise prescription according to established protocols from the American Association of Cardiovascular and Pulmonary Rehabilitation. Patients exercised for 12 weeks, typically with three 1-hour sessions per week.

Abnormal HRR was defined as a ≤12 bpm difference between heart rate at peak exercise and at 1 minute into the recovery period. At baseline, 544 patients had abnormal HRR; after cardiac rehabilitation, HRR had normalized in 225 (41%) of these patients.

Baseline characteristics that predicted a failure to normalize HRR were older age, peripheral artery disease, and chronic heart failure.

Importantly, patients with an abnormal baseline HRR who did not normalize following rehabilitation were more than twice as likely to die during a median 8.1 years of follow-up (hazard ratio [HR]=2.24 vs those whose HRR normalized).

Other independent baseline predictors of mortality included older age (HR=1.67 per 10-year increase), peripheral artery disease (HR=2.31), male gender (HR=1.73), use of nitrates (HR=1.75), and use of statins (HR=0.59).

By contrast, patients whose HRR normalized following cardiac rehabilitation had comparable long-term mortality to patients whose HRR was normal at baseline.

"There's no medicine that can do that," remarked Cho in a press release accompanying the study. "If we had a medicine that could make this dramatic an impact it would be the blockbuster drug of the century."

The researchers say the next step is to encourage more patients to participate in structured exercise, noting that just 10-20% of candidates currently take part. "Cardiac rehabilitation is the most underused treatment in America," he noted.

Further research is also needed to determine whether extending cardiac rehabilitation beyond 12 weeks yields additional benefits and helps normalize HRR in a greater proportion of patients, conclude the authors.

By Joanna Lyford