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By Ed Edelson
Answers to that question are expected next year from two major international trials that are testing the drug, said Dr. Jeffrey S. Borer, a professor of cardiovascular medicine at Weill Cornell Medical College in New York City.
The resting heart rate is the natural heartbeat measured after someone has been at rest for at least 10 minutes. A number of studies have linked a lower resting heart rate with better outcomes among those with cardiovascular disease, said Borer, a member of a group summarizing that evidence in the Aug. 28 issue of the Journal of the American College of Cardiology.
"That group of authors is involved in the evaluation of a new approach to heart rate slowing," Borer said. "It allows us for the first time to determine the pure effect of heart rate slowing on cardiac health."
The new approach uses a drug called ivabradine, which acts specifically on the cells of the sino-atrial node, the heart's natural pacemaker. Other drugs, such as beta blockers, can slow the resting heart rate, but they have other effects that blur the impact of a slowed resting heart rate.
Ivabradine has been approved in Europe for treatment of the chest pain called angina, but Servier Laboratories, the French company that markets the drug, has not applied for U.S. approval because it has no American subsidiary.
A footnote to the journal paper says all of its 10 authors "have received honoraria and many have received research grants from Servier Laboratories, and all authors are a part of the advisory board of ivabradine."
But those physicians, who describe themselves as members of the Heart Rate Working Group, are interested more in the general effects of resting heart rate than in any one drug, Borer said.
"We have been publishing for several years, because it became apparent that the potential importance of resting heart rate in determining prognosis is not so well understood," he said.
Perhaps the first study to indicate the possible importance of the resting heart rate was done during World War II, looking at the medical records of 25,000 army officers, Borer said. "Those with a resting heart rate above 100, about 300 of them, had a very poor long-term outcome," he noted.
In recent years, studies done in Norway have looked at possible beneficial effects of lowering the resting heart rate, using drugs such as beta blockers, Borer said. Studies of people with heart failure, the progressive loss of the heart's ability to pump blood, and of those who had suffered heart attacks, did show a benefit from slowing the heart rate, he added.
And a report on 25,000 cardiac patients done by Dr. Jean-Claude Tardif, of the Montreal Heart Institute, showed "a clear distinction in outcome based on resting heart rate," Borer added.
While there obviously are differences among individuals as to the best resting heart rate, "it is probably best if it is somewhat lower than 70" for an adult, he said.
Definitive evidence on the value of using a drug to lower the resting heart rate is expected from the two international trials now in progress, one including people with coronary artery disease, the other including people with heart failure, Borer said.
Results of those studies should be available by the late summer of 2008, he said.
SOURCES: Jeffrey S. Borer, professor, cardiovascular medicine, Weill Cornell Medical College, New York City; Aug. 28, 2007, Journal of the American College of Cardiology
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