Monday, March 26, 2007

Heart Test Shows Who Needs Implantable Defibrillators

(HealthDay News) -- A new study provides more evidence that a special heart test could give cardiologists guidance on which patients need implanted defibrillators.

The research, which looks at patients who have weak heart muscles but no underlying coronary disease, suggests that the test, known as T-wave alternans, can predict which patients are at highest risk of suffering heart rhythm disorders. They can then get the implanted defibrillators, while the others could potentially avoid the procedure.

Still, more research is needed, said Dr. Andrea Russo, an electrophysiologist at the University of Pennsylvania. "We need more studies that are confirmatory before we start excluding patients from implantable defibrillators," she stressed.

A number of conditions, including viral infections and alcoholism, can weaken parts of the heart even when someone doesn't have clogged arteries. In some cases, there's no apparent cause.
People with this condition -- including some young people -- can suffer from abnormal heart rhythms and die. But doctors often try to boost their chances with implanted defibrillators designed to shock their hearts back into a proper rhythm when necessary.

Doctors have been looking for a way to predict which patients need defibrillators and which would be fine without them. Enter the T-wave test, which Russo said is similar to an EKG.
Patients typically undergo the test, which requires electrodes to be placed on the body, while exercising. According to Russo, it detects whether the heart's electrical system has the rough equivalent of a short circuit that could cause a heartbeat so fast that the heart can't handle it.
In the new study, Italian researchers examined what happened after 446 patients with heart failure -- defined here as moderate heart muscle damage -- were given the T-wave test. None of the patients had significant cardiovascular disease.

The findings were to be presented Sunday at the American College of Cardiology's annual meeting in New Orleans.

Researchers followed the patients for 18 to 24 months, and found that those with an abnormal T-wave test (65 percent of patients) were four times more likely to suffer from cardiac death or life-threatening disruptions in heart rhythm. The study authors suggest the other patients aren't ill enough to need implanted defibrillators.

"Knowing this, we are able to better treat the two-thirds of patients that really need the device," contributing author Dr. Gaetano De Ferrari, of the San Matteo Hospital in Pavia, Italy, said in a statement.

While there have been other studies supporting the T-wave test, cardiologists haven't embraced it, said Dr. Paul Chan, a fellow in cardiovascular medicine at the University of Michigan Medical School. According to him, some cardiologists are worried about the legal ramifications if the test suggests that someone doesn't need a defibrillator and then the patient dies.

Meanwhile, he said, "the ultimate question that hasn't been answered really well is whether or not those patients who screened as normal [would] have any benefit" from getting a defibrillator.
Cost could be another factor: T-wave machines cost about $25,000. However, implantable defibrillators are hardly cheap themselves: by one estimate, they can cost $90,000 over a lifetime.

More information
Visit the Heart Rhythm Society for more on implantable defibrillators.

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