MONDAY, Aug. 6 (HealthDay News) -- Implantable cardioverter defibrillators -- small devices placed in the chest to detect potentially fatal heart rhythms -- reduce the number of cardiac arrests caused by ventricular fibrillation, a type of abnormal heart rhythm, according to a new study.
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Researchers in the Netherlands estimate that the cardioverter defibrillators prevented 81 cardiac arrests related to ventricular fibrillation between 2005 and 2008 in greater Amsterdam. They further estimate that the devices accounted for one-third of the decline seen in cardiac arrests caused by ventricular fibrillation between 1995 and 2008.
The study was published Aug. 6 in Circulation.
"At least one in 20 [implantable cardioverter defibrillator] carriers can expect a life-saving shock from their device each year," the study's senior author, Dr. Rudolph Koster, associate professor of cardiology at the Academic Medical Center in Amsterdam, said in a journal news release.
In conducting the study, the researchers examined data on cardiac resuscitations by emergency medical services in Amsterdam from 1995 to 1997 as well as all emergency cardiac arrest interventions in the area between 2005 and 2008.
After singling out people who had ventricular fibrillation when emergency help arrived, the study revealed an estimated 339 shocks were able to stop 194 potentially fatal heart rhythms in 166 people. The researchers also found the percentage of patients with ventricular fibrillation dropped from 63 percent from 1995 through 1997 to 47 percent from 2005 through 2008.
Annual ventricular fibrillation cardiac arrests also dropped dramatically -- from 21.1 to 17.4 people per 100,000. In contrast, cardiac arrests related to other abnormal heart rhythms jumped from 12.2 to 19.4 per 100,000 each year.
The researchers said it is unclear why other abnormal heart rhythms have increased, or what else accounted for the decline in ventricular fibrillation cardiac arrests.
"The possible mechanisms are only guesses without much solid evidence," Koster said.
-- Mary Elizabeth Dallas
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SOURCE: American Heart Association, news release, Aug. 6, 2012