March 31, 2000

New pacemaker may jump-start treatment options

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Dr. Mark Wathen (seated) and Dr. Sai Hanumanthu check the x-ray of a patient who received the new pacemaker. (photo by Dana Johnson)

New pacemaker may jump-start treatment options

Vanderbilt University Medical Center researchers are investigating a new type of pacemaker that may expand the range of treatment options for patients suffering from congestive heart failure.

Currently, those options are limited to chronic drug therapy or transplant, and while advances continue, mortality rates for those suffering from congestive heart failure remain high and overall quality of life poor.

Dr. John R. Wilson, professor of Medicine and director of the Vanderbilt Heart Failure Program, and Dr. Mark S. Wathen, assistant professor of Medicine and director of the Electrophysiology Lab at Vanderbilt, are the principal investigators here of the Multicenter Insync Randomized Clinical Evaluation, or MIRACLE, study. VUMC is one of 30 centers in the United States and Canada participating in the study.

Traditionally, pacemakers are used in patients with faulty heart rhythms. Two leads, generally configured with one in the right atrium and one in the right ventricle, electrically stimulate the heart to produce normal heart contractions.

The new cardiac-pacing device, called Insync, involves the placement of a third lead in the left ventricle. The new system is used to pace both ventricles (the lower chambers of the heart) at the same time, simulating a "normal" heart beat.

This electrical stimulation to the heart provides more coordinated contractions, which may lead to improved pumping action by the heart. Published work from Europe has shown overall improvement in patient symptoms and well being, as well as sustained physiologic improvements.

"The key thing is that this pacemaker is for congestive heart failure patients," said Wathen. "This is not drug-therapy based. We are applying pacing to the patient who doesn't have slow heart rhythms. This is non-traditional and represents a new area that is device-based rather than pharmaceutical-based."

Congestive heart failure is a condition in which the heart is unable to pump enough blood to meet the needs of the body. Heart failure patients typically experience shortness of breath and have poor exercise tolerance. As the disease progresses, the heart's chambers become more and more dilated and enlarged. As the heart enlarges, its conduction system and mechanical properties change, contributing to an inefficient pumping ability.

Candidates for the "resynchronization" device must be diagnosed with congestive heart failure and show specific characteristic on an EKG. They also cannot have a pacemaker already in place.

Each patient will participate in a six-month randomized therapy, which will include regular follow-up. Patients will know if therapy is "on" or "off" at the time of implantation. All devices initially randomized to "off" therapy will be turned on at six months.

"Quality of life is a big issue," said Dr. Hanumanthu. "These are very sick people whose disease severely limits even the most routine daily activities.

"Pacing both ventricles at the same time and making your heart beat in a more organized fashion may improve its pumping ability and improve the ability to tolerate more physical activity," he said. "This is a quality of life issue. Preliminary data shows that the quality of life scores are five times better than any drug therapy used for congestive heart failure."

As part of the overall study, Vanderbilt has been selected to conduct a single-center substudy to investigate if biventricular pacing actually improves hemodynamic responses to exercise. Dr. Sai K. Hanumanthu, a Vanderbilt cardiology fellow, and Wilson will conduct this study.

Patients enrolled in the MIRACLE Trial can also participate in the substudy, which seeks to determine the underlying mechanisms of biventricular pacing that are leading to clinical improvements.

Doctors in the program hope to enroll at least 20 patients in the study. For more information, call the Vanderbilt Heart Failure program research trial coordinator, Andrea Delmotte, R.N., at 343-3735.