Heart Rate Recovery
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.
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."