Heart Health Special Report
Zapping Abnormal Heart Rhythms
Atrial fibrillation is a common heart rhythm abnormality in which the atria quiver chaotically, causing rapid and irregular contractions of the ventricles. For people with atrial fibrillation, the traditional treatment route is to try various medications first and opt for invasive procedures such as open-heart surgery as a last resort. Now a middle-of-the-road option, a minimally invasive procedure known as catheter ablation, is growing in popularity. Johns Hopkins explains catheter ablation.
In their latest guidelines for atrial fibrillation, the American College of Cardiology (ACC) and the American Heart Association (AHA) list catheter ablation as a "second-tier" therapy. This means that physicians can consider it after just one anti-arrhythmic drug has not controlled heart rhythm, rather than exhausting all medication options. In fact, catheter ablation may allow people with atrial fibrillation to stop taking anti-arrhythmic drugs altogether.
Traditionally, when medications to slow heart rate, such as beta-blockers, calcium channel blockers, and digoxin (Lanoxin, Lanoxcaps), and drugs to regulate heart rhythm, such as amiodarone (Cordarone, Pacerone), flecainide (Tambocor), and sotalol (Betapace, Sorine), did not control atrial fibrillation or caused intolerable or dangerous side effects, an operation known as the Maze procedure was considered.
In this procedure, a surgeon makes small incisions on the heart to create scar tissue that interferes with the abnormal electrical signals. The technique is highly successful in suppressing atrial fibrillation but is not widely used because it requires open-heart surgery.
Catheter Ablation Procedure
Like the Maze procedure, catheter ablation aims to correct the abnormal electrical signals but does so without major surgery. During the procedure, an electrophysiologist (a doctor who specializes in heart rhythm disturbances) inserts a catheter (a long, flexible tube) into a vein, typically in the groin, and threads it up to the heart. A special x-ray technique called fluoroscopy is used to visualize the catheter on a video screen.
Once positioned in the left atrium, electrodes at the catheter's tip gather data that allow the doctor to pinpoint the pathway that generates and maintains the abnormal electrical activity. After these "hot spots" are mapped, radiofrequency waves, delivered through a separate catheter, are used to heat and destroy tiny areas of tissue. The result: scar tissue that blocks the aberrant electrical signals.
Because it takes time for scar tissue to form after the ablation, people often take antiarrhythmic drugs for a few months to suppress any atrial fibrillation episodes. In some individuals, continued medication or a repeat ablation is necessary to become fully atrial fibrillation free.
The latest research suggests that atrial fibrillation episodes are safely suppressed in 75-80% of patients one year after ablation. In contrast, only about half of people on antiarrhythmic medications remain atrial fibrillation free for a year, and they often experience drug side effects.
Is Catheter Ablation for You?
According to the most recent ACC/AHA guidelines, an antiarrhythmic drug should be your first choice. But if medication fails to suppress your atrial fibrillation episodes or if the side effects are intolerable, you and your doctor can consider catheter ablation. The procedure can be safely and effectively performed in people of almost any age, with either periodic or chronic atrial fibrillation, as long as the left atrium is not significantly enlarged and no blood clots are detected in the left atrium. That said, the risk of complications does rise with age, and the outcome is better in people with only periodic atrial fibrillation symptoms.
Many people mistakenly believe they'll be able to discontinue anticoagulant therapy, such as warfarin, after the procedure. But this is true only for those at very low stroke risk. People at high risk -- those over age 75, those with a prior stroke or transient ischemic attack, and those with heart failure, high blood pressure, or diabetes -- must continue warfarin indefinitely, even if the procedure is successful. Thus, a desire to discontinue warfarin is not a valid reason for undergoing catheter ablation.
What the Future Holds
The catheter ablation procedure is still evolving, and the safety and efficacy of the procedure will likely continue to improve. But if you decide to have catheter ablation today, be sure to choose a doctor who is highly experienced in the procedure -- an electrophysiologist who performs at least 20-40 procedures a year. The experience of the hospital is important, too. Look for one that has performed more than 100 catheter ablations.
Posted in Heart Health on August 7, 2009