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Study: Implanted Shock Devices Highly Effective Against Cardiac Arrest

November 14, 1991

ANAHEIM, CALIF. (AP) _ Implanted devices that shock the heart back to life after cardiac arrest are almost 100 percent effective in stopping people from dropping dead suddenly, a study shows.

Researchers said these devices - which are about the size of a deck of cards and are implanted in the abdomen - may someday become more common than pacemakers, which are given to about 100,000 Americans each year.

″There are a lot of patients out there who should have these devices and don’t,″ said Dr. Roger A. Winkle of Stanford University, who directed the study.

His work, the most extensive study ever of these devices, called defibrillators, shows that they virtually eliminate the risk of a second cardiac arrest. About 300,000 Americans annually drop dead suddenly.

In a review of 650 patients, the doctors found that just 1 percent per year died of cardiac arrest over 10 years of follow-up. An average of 3 percent a year died of heart failure, stroke, cancer and a variety of other diseases.

Winkle said that without defibrillators, at least 30 percent would have died over one to two years. About 60 percent would die over five years, and nearly everyone would be dead within 10 years.

Winkle presented his results Wednesday at a meeting of the American Heart Association.

Dr. Ross D. Fletcher of Georgetown University said the implantable defibrillators are becoming the stardard treatment for people who are lucky enough to have been revived by CPR from cardiac arrest.

″It’s becoming a better and better therapy,″ he said. ″Nothing else comes close to this effect.″

During cardiac arrest, the heart quits beating in an organized fashion, and circulation stops. The defibrillator detects this and automatically delivers a powerful electrical shock, which jolts the heart back to work.

In Winkle’s study, 60 percent of the defibrillators had fired at least once to restart people’s hearts.

The device, made by Cardiac Pacemakers Inc. of St. Paul, Minn., costs about $50,000 when implanted.

It was developed by Dr. Michel Mirowski of Johns Hopkins University and first used in 1980.

Although the devices are now much smaller than the first models, they are still about five times larger than pacemakers, which are also implanted in the body to regulate heartbeats.

Dr. Debra Echt of Vanderbilt University said a research goal is to make the devices so small they can be implanted in the chest, like pacemakers. But this will require new technology to develop smaller capacitors to store energy.

Many doctors once thought that drug therapy would be the best way to control abnormal heartbeats. But these medicines have worked poorly, and some have even turned out actually to cause cardiac arrest rather than stop it.

Instead, the use of defibrillators has grown rapidly in recent years, and about 8,000 to 10,000 are now implanted annually in the United States.

Winkle said the devices will be much more widely used if studies show that they prevent death in people who have damaged hearts but have not yet suffered cardiac arrest.

Until recently, they required major operations to be implanted, but new ones can be inserted non-surgically, just as pacemakers are.

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