Irregular Heartbeats : Preventive Treatment, An Internal Jolt

by Food and Drug Administration (FDA)

(Page 3 of 3)

Preventive Treatment

Before starting any preventive drug treatment regimen, doctors first try to rule out reversible causes of ventricular arrhythmias: for example, caffeine, alcohol and tobacco consumption, and certain over-the-counter and prescribed medicines.

Also, because treatments pose substantial risks relative to the risk of the arrhythmias themselves, doctors tend not to treat ventricular arrhythmias unless they are tied to significant symptoms or are life-threatening. For this reason, FDA has not approved any treatments for premature ventricular beats.

However, there are several drugs approved for preventing ventricular tachycardia. The main types are beta blockers and sodium or potassium channel blockers. Most drugs to prevent ventricular tachycardias are taken orally up to four times daily and often must be taken for life.

Beta blockers, such as propranolol hydrochloride (Inderal and others), stem the automatic stimulation of heart contractions by the nervous system. Sodium and potassium channel blockers hamper transmission of electrical impulses in heart cells. Some sodium channel blockers are quinidine (Quinidex Extentabs, Quinaglute and others) and procainamide hydrochloride (Procan, Pronestyl and others). FDA approved in February 1996 a long-acting form of procainamide, Procanbid, which is taken only twice a day, compared with other procainamides, which must be taken four times daily.

Potassium channel blockers, such as amiodarone hydrochloride (Cordarone) and sotalol (Betapace), also are used to prevent ventricular tachycardias.

Doctors monitor the effectiveness of antiarrhythmia drug therapy with an ECG, or with electrophysiologic testing. Monitoring is essential not only to ensure effectiveness but safety, as well, because many of these drugs can make arrhythmias worse. Other side effects of antiarrhythmia drugs that can limit their use are low blood pressure, lung damage, nausea, and dizziness.

According to Wilber Aronow, M.D., a cardiologist with Mount Sinai School of Medicine in New York City, studies show that people treated with certain beta blockers following a heart attack have a significantly reduced risk of sudden cardiac death. But many large-scale studies of several different types of sodium channel blockers, as well as studies of certain potassium channel blockers, have shown that treatment with these drugs following heart attacks does not improve survival odds, or reduce them.

Ventricular arrhythmias are common within a month of a heart attack and are associated with an increased risk of sudden cardiac death.

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."

About the Author

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