The study focuses on a genetic condition called hypertrophic cardiomyopathy (enlarged heartdue to thickened heart muscle).
ICDs are surgically implanted devices that are designed to note abnormal heart rhythms and deliver an electrical shock to make hearts beat properly.
Hypertrophic cardiomyopathy accounts for most cases of sudden cardiac death in young people, including trained athletes, write the researchers, who included Barry Maron, MD, of the Minneapolis Heart Institute Foundation.
Maron's team reviewed data on 506 people with enlarged hearts who got ICDs between 1986 and 2003 in the U.S., Australia, and Europe.
The patients were 42 years old, on average, when they got their ICDs. Nearly 90% of them had "no or only mildly limiting symptoms," write Maron and colleagues in The Journal of the American Medical Association.
ICDs and Enlarged Hearts
The researchers followed the patients for nearly four years, on average. During that time, the ICDs appropriately stopped dangerous heart rhythms in 20% of the patients.
The chance of that happening was roughly the same for patients with one, two, or three risk factors for sudden death.
However, ICDs fired inappropriately in 102 patients over the years, andone patient(who turned out to have a defective ICD) died as a result.
Other risks included infection, bleeding or clotting, and problems with the ICD.
Maron's team concludes that ICDs may help prevent sudden cardiac death in people with hypertrophic cardiomyopathy who have only one risk factor for sudden cardiac death.
But the researchers stress that "it is not our intention to promote a strategy for universal ICD implantation in patients with hypertrophic cardiomyopathy who have only one risk factor."
The study was funded in part by Medtronic, which makes ICDs. Two of the researchers (but not Maron) report financial ties to Medtronic and other ICD companies.
ICDs and Enlarged Hearts: Second Opinion
ICDs should "definitely" be considered by patients with hypertrophic cardiomyopathy who have already had a heart attack or sustained fast heartbeats, states an editorial published with the study in The Journal of the American Medical Association.
ICDs are likely warranted in patients with enlarged hearts who have two or more risk factors for sudden cardiac death, according to editorialists Rick Nishimura, MD, and Steve Ommen, MD, who work in the division of cardiovascular diseases and internal medicine at the Mayo Clinic College of Medicine in Rochester, Minn.
"However," the editorialists write, "the decision to implant an ICD in any patient, especially one with a single risk factor, must include a thorough and earnest discussion" of risks and benefits, as well as the patient's views on "procedures, devices, and death."