Sep 26, 2011 11:15 PM
Sept. 26, 2011 -- Cardiac rehabilitation can be extremely effective, yet most people choose to avoid it. New research may make them think twice.
"Time and time again, cardiac rehabilitation has been shown to improve survival, to improve quality of life, and of course improve exercise capacity," says researcher Leslie Cho, MD, section head of preventive cardiology and rehabilitation at the Cleveland Clinic.
However, experts debate whether it's possible to reverse an abnormally slow return to a normal heart rate, and if doing so can lengthen life.
The new research sheds light on both points. "For the first time, we have shown that cardiac rehabilitation can train the heart to return to its normal rate quickly after exercise and improve survival. This is better than any medicine," Cho says.
The study is published in Circulation: Journal of the American Heart Association.
The researchers evaluated 1,070 patients who were referred for cardiac rehabilitation, three-quarters of them men. The average age was 61. They looked at the ability of the heart rate to return quickly to normal, also known as heart rate recovery. While 544 had an abnormal heart rate recovery at the start, the other 526 had a normal heart rate recovery.
They took part in a 12-week cardiac rehabilitation program. Typically, such a program includes doctor-supervised exercise sessions of about an hour or more, three times a week. It includes a warm-up and stretching and about 30 or more minutes of continuous aerobic activity followed by a cool-down.
Before and after the program, patients took exercise stress tests. Researchers measured how quickly their heart rate returned to normal afterward.
Heart rate recovery is also defined as the number of beats the heart rate declines during the first minute after stopping exercise.
"Abnormal is less than 12," Cho says. For instance: "If your peak was 100 beats per minute and it falls to 95 in the first minute after stopping, that's not good."
Experts have known that an abnormal heart rate recovery can predict an increased risk of death. Some small studies have found that heart rate recovery can be improved by exercise training.
However, it isn't known, the researchers write, if that improvement actually produces benefits such as longer survival.
Among the 544 who started with an abnormal heart rate recovery, 41% had a normal one by the end of the program.
Of the 526 who started with a normal heart rate recovery, 89% maintained it. (The others, Cho says, may have had worsening heart disease, explaining the decline even with exercise.)
The average heart rate recovery was 13.2 overall at the study start. At the end it was 16.6. Those less likely to return to a normal heart rate quickly were older, had a history of congestive heart failure, used nitrates, or had peripheral artery disease.
During the follow-up of eight years, 197 patients died.
Here is the most important point: Those who had an abnormal heart rate recovery at the study end were twice as likely to die as those whose heart rate recovery was normal.
Having a good heart rate recovery "means your autonomic nervous system is in good shape," Cho says. "If the autonomic nervous system is in good shape, you live longer, have fewer heart attacks."
The system regulates the heart and other organs. One of its jobs is to ''rev you up'' when you need to be, Cho says, such as when you encounter danger. However, an unhealthy autonomic nervous system is constantly revved up, and that's hard on the heart.
The study results suggest more patients should heed the advice to go to cardiac rehab, Cho says. About 80% of those who are eligible don't go, she says. Many cite time constraints.
She hopes her study results will make them think again. "Not only are you learning how to exercise, but you are improving survival," she says.
Cardiac rehab programs recommended by a doctor after a heart attack, heart surgery, or other conditions may be covered by insurance. Medicare Part B, for instance, partially covers programs for patients who meet certain conditions.
"This is a strong study; it has over 1,000 subjects," says Noel Bairey Merz, MD, medical director of the Preventive and Rehabilitative Cardiac Center at Cedars-Sinai Medical Center in Los Angeles.
She reviewed the study findings for WebMD but was not involved in the research.
The doubling of survival found by Cho's team, she says, "is huge."
"I think this is telling us once again that exercise conditioning is important," she says. "A rapid return to the baseline [starting] heart rate is an essential marker of fitness. An unfit cardiovascular system will have a really slow heart rate recovery."
For heart patients, she says, the message is clear. "Exercise conditioning deployed properly -- that is, in cardiac rehabilitation -- reduces death rates."