Study with dogs shows devices much more than a mechanical fix for ailing patients
FRIDAY, March 21 (HealthDay News) -- In dogs with damaged hearts, implanted pacemakers triggered fast improvements in tissue levels and the activity of a number of proteins crucial to heart health, says a Johns Hopkins study.
The researchers said their findings are believed to be the first detailed chemical analysis of the biological effects a pacemaker has on the heart. This new information could lead to improvements in the use of combined pacemaker/drug treatments for congestive heart failure patients.
"We are learning that pacemaker therapy does profoundly more than just mechanically correct how the heart beats; in fact, it produces major chemical changes that benefit the muscle," lead investigator Khalid Chakir, a postdoctoral cardiology research fellow at Hopkins, said in a prepared statement.
In this study, Chakir and colleagues induced "wobbly, discoordinated contraction" in the hearts of 22 dogs. In half the dogs, this asymmetric heart failure was allowed to take its natural course. The other dogs received a cardiac pacemaker.
Tissue analysis found major changes in the production or activity levels of 17 proteins known to be involved with heart cell stress, survival and death. These changes were especially notable in the dogs that didn't have their hearts "retuned" by a pacemaker.
In the dogs that did receive a pacemaker, the tissue levels and activity of these proteins were restored toward normal. The findings were published online in Circulation.
"Our results really help explain how pacemakers act much like a drug, actually changing the biology of the heart, and also explain why people can feel so much better after just two to six months with the device," study senior investigator Dr. David Kass, a cardiologist and professor at the Johns Hopkins University School of Medicine and its Heart Institute, said in a prepared statement.
Each year in the United States, more than a million people are diagnosed with congestive heart failure, in which the heart weakens and isn't able to pump enough blood to the rest of the body. About 25 percent of congestive heart failure patients suffer from non-uniform heart contraction, which requires implantation of a pacemaker to restore normal heartbeat, according to background information in a news release about the study.
Pacemakers can help extend people's lives for month or years or help them return to normal daily activities. It had been believed that pacemakers simply provided a mechanical solution for heartbeat malfunction.
"Now that we have found that resynchronization is doing more fundamental things to the heart muscle, we should be able to better combine these devices with drugs to maximize long-term survival and outcomes," Kass said.
The U.S. Food and Drug Administration has more about cardiac pacemakers.
-- Robert Preidt
SOURCE: Johns Hopkins Medicine, news release, March 6, 2008
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