September 26, 2003

Arrhythmia treatment, research hand-in-hand at VUMC

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Dr. Dawood Darbar examines Connie Dill in the genetic arryhthmia clinic. (photo by Dana Johnson)

Arrhythmia treatment, research hand-in-hand at VUMC

Atrial fibrillation — irregularity of the heartbeat — is the most challenging and common heart rhythm disorder seen in hospitals. And doctors at VUMC are in a unique position to not only treat the irregularity, but also investigate the causes of the arrhythmia and develop new therapies that will lead to major advances in how abnormal rhythm is managed.

Often referred to as both the “disease of the elderly” and the “epidemic of the 21st century,” symptoms include palpitations, dizziness, chest pains, rapid heartbeat and shortness of breath. As the population ages, the incidence is dramatically increasing; about 5 million Americans currently have suffered from atrial fibrillation, and the condition is becoming increasingly recognized in younger patients. Predisposing factors including high blood pressure, valvular heart disease and hyperthyroidism are frequently associated with atrial fibrillation. Stroke is the most feared risk.

“We are in an exceptional position at Vanderbilt,” said Dr. Dawood Darbar, assistant professor of Medicine and Clinical Pharmacology. “We not only manage patients with atrial fibrillation, but carry out research that investigates the underlying causes for the arrhythmia.

“There are many centers offering treatment and management, but very few have the resources to develop new therapies and advance the field. We are able to go from the bench to the bedside, and back to the bench again. It is the whole continuum of care.”

Currently, the goals of treatment for atrial fibrillation patients are threefold: improve symptoms, control the heart rate, and reduce the risk of stroke. Much of this is achieved with medications.

But doctors caution that even with medication, the condition is often difficult to manage.

“The medications currently available are only effective in achieving the goals of reducing heart rates and preventing further episodes,” Darbar said.

“And now, we have discovered another group of patients with atrial fibrillation with no obvious causes or reasons,” he said. “These patients with ‘lone’ atrial fibrillation tend to be much younger, to not respond well to traditional drug therapies, and be difficult to detect, leading to misdiagnosis.”

In patients with “lone” atrial fibrillation, the trigger for the symptoms commonly arises from the pulmonary veins. Recently, a relatively new treatment called pulmonary vein (PV) ablation has become available for this form of atrial fibrillation. The latter involves applying radio frequency energy directly to the PV to rid the patient of all symptoms.

Doctors are cautious when using the technique because of the unknown long-term success and complication rates and the complexity of the procedure. It is also only available for a select group of patients.

The use of nonpharmacological therapies to treat atrial fibrillation is an area of active research at Vanderbilt. PV ablation is one such therapy. Another is AV node ablation and pacemaker implantation that calls for specially trained cardiologists, called clinical cardiac electrophysiologists, to ablate the AV node so that it does not conduct electrical impulses from the upper chamber to the lower chamber of the heart. A pacemaker is implanted to help the lower chamber of the heart beat at the appropriate rate. A more aggressive approach is open-heart surgery, called the maze procedure. With this technique, cardiac surgeons create channels or scars in the upper chambers to keep the electrical impulses confined to one area.

This option for atrial fibrillation is usually reserved for patients that are already undergoing heart surgery for some other reason. The success rates of the procedure are very high.

“In the area of PV ablation, we don’t know which group of patients do the best with this therapy,” Darbar said. “So far, it has worked well in patients with ‘lone’ atrial fibrillation, but it takes a while to determine the durability of this treatment and to develop the optimal criteria for treatment. And patient selection is a top priority. We have made advancements in this area, but are constantly taking new steps for improvement.”

Vanderbilt is known for developing new drug treatments and therapies, and the Arrhythmia Group is currently involved in evaluating new treatments for atrial fibrillation like PV ablation as well as testing novel ways of treating arrhythmias. Patients with atrial fibrillation are usually seen in the Arrhythmia Clinic but recent creation of the Genetic Arrhythmia Clinic has provided an additional resource for patient recruitment for studies.

Members of the adult arrhythmia service who see patients with atrial fibrillation and collaborate in the clinical research include Drs. John T. Lee, associate professor of Medicine, Mark Stephen Wathen, assistant professor of Medicine and Jeffrey N. Rottman, associate professor of Medicine and Pharmacology.

“To complement our clinical research, we have a renown group of basic science investigators,” Darbar said.

Some of the examples of Vanderbilt’s work include that of Drs. Dan Roden, William Stokes Professor of Experimental Therapeutics and professor of Medicine and Pharmacology, on arrhythmia drug therapies and their genetics, and the work of Kathy Murray, associate professor of Medicine and Pharmacology, on the causes of atrial fibrillation and how it can cause heart damage.

Recently, the members of the Vanderbilt Arrhythmia Services, directed by Dr. Mark Anderson, associate professor of Medicine and Pharmacology, have teamed up with researchers from the Division of Clinical Pharmacology and other scientists at the Cleveland Clinic Foundation to apply for a multi-investigator group with a focus on novel approaches to treating cardiac arrhythmias, including atrial fibrillation and the pioneering work of Anderson on how newer therapies affect atrial fibrillation.

“They study the basic mechanisms involved with human arrhythmias,” Darbar said. “In addition, the recent recognition that many arrhythmias, including atrial fibrillation, may have a genetic basis has meant that our collaborations with genetics experts at Vanderbilt will ultimately prove very fruitful.”