An Internal Jolt
Another treatment option for people at risk for life-threatening arrhythmias is an implanted cardioverter defibrillator. FDA approved the first implantable defibrillators more than 10 years ago.
Today's device typically consists of a generator slightly smaller than the size of a wallet attached to electrode catheters. The generator is surgically placed under or over chest or abdominal muscles. The catheters are threaded through veins to their permanent positions in the heart. Complications of implanting defibrillators are rare but serious and include bleeding, infections, and perforation of the heart.
Implanted defibrillators monitor the heart rhythm and automatically treat, with electrical stimuli or shocks, rhythms recognized as abnormal. Newer devices also can record and store data of the electrical activity of the heart that doctors can later download and evaluate for arrhythmias. The data also can be used to perform electrophysiologic testing.
Implanted defibrillators can often stem ventricular arrhythmias with low-energy shocks. Sometimes, however, high-energy shocks are needed. These shocks, though short-lasting, can be painful--somewhat akin to a kick in the chest.
The generators in implanted defibrillators usually last three to five years and can be replaced with a surgical procedure that usually requires only local anesthesia. The electrode leads tend to last longer, although they can develop cracks or component failures that require their replacement.
A recent study of heart attack survivors by Arthur Moss and colleagues from the University of Rochester (N.Y.) Medical Center found implantable defibrillators cut survivors' risk of death in half.
A National Heart, Lung, and Blood Institute study under way is assessing whether implanted defibrillators or drug therapy is more effective in extending the lives of patients with ventricular arrhythmias.
Opening the Chest
Open-heart surgery to remove heart tissue causing or contributing to arrhythmias may be warranted for patients whose ventricular arrhythmias cannot be controlled by drugs. But, this is feasible only for patients whose arrhythmias can be attributed to heart sites that are limited in size and number. Most patients who undergo this procedure survive.
To avoid the risks and painful recovery of this procedure, a number of clinical investigators have used radiofrequency energy, delivered via catheters threaded through veins to the heart, to destroy heart tissue at the root of ventricular arrhythmias. FDA has not yet fully evaluated the safety and effectiveness of this experimental procedure.
But the availability of other treatment options means that many patients with ventricular arrhythmias can be treated effectively.
That wasn't true a decade ago, cardiologist Epstein points out. 'We're a lot further along."
