Mapping (and Repairing) the Heart's Electrical Circuitry

The heart as a fuse box.

That may be offbeat imagery. But the figure of speech may be just as appropriate as "the heart as pump" or "the heart as engine" or any of the other mechanical metaphors that have been called up over the years to describe this four-chambered wonder, this sine qua non of our human body.

The fuse-box image springs to mind when you're in the company of James P. Daubert, M.D., Director of the Electrophysiology Service (EP) and a leader in the burgeoning subspecialty of electrophysiology. Dr. Daubert talks like a doctor who's also an electrician. The words "wiring" and "electrical pathways" pepper his conversation. More important, he turns his knowledge of the heart's complex circuitry into a life-saving technology that can both diagnose and cure.

"The heart has its own pacemaker," Dr. Daubert points out, losing no time in getting to the heart of the matter. "Usually that pacemaker is a cluster of specialized cells located in the sinus node of the right atrium, which acts as the heart's generator. When the heart is functioning properly, that pacemaker fires 50 to 100 times a minute. After each firing, the electrical activity spreads through the rest of the heart, down through the specialized wiring system, to activate the heart's lower chambers or ventricles - the pumping chambers." Unfortunately, the heart's electrical system often isn't functioning properly. Whether it's a mild flutter or a severe tachycardial arrhythmia, the result generally means trouble.

"Heart disease is the number one killer in the United States, and for most of these victims death comes suddenly," Dr. Daubert points out. "About 400,000 people die each year after they've experienced a sudden change in heart rhythm, some alteration in the electrical signal."

Arrhythmia - whether slow or fast - may happen suddenly, even to people with no previous symptoms. Abruptly, the heart stops beating; seconds may pass before the pump reactivates. Tragically, for some, the beat is gone forever. For the fortunate, help comes in the form of an emergency medical response. An external electrical shock is administered to the chest (or an internal shock from an implanted defibrillator), the body convulses in response, the heart pulses, the beat catches, the normal rhythm of the heart finally returns.

The EP Test: Diagnosis - and Therapy

When the electrophysiology team administers an EP test, a tiny catheter is guided through a blood vessel into the heart. Using this "listening" device, heart rhythms (or arrhythmias) are electronically recorded. Within this sterile, controlled setting - where corrections can be made within a matter of seconds -the team tries to recreate the abnormal rhythm.

"This may sound dangerous, but it's much safer than having the attack occur out on the street. Once we pinpoint the problem, we can recommend treatment," says Dr. Daubert.

With some patients, that may mean the implantation of a pacemaker; for others, ablation - using radio-frequency energy conducted through a catheter - may be required to "burn out" an extra electrical pathway or malfunctioning tissue. In patients with Wolff-Parkinson-White syndrome, for example, there's a break in the heart's normal insulation that enables the electrical impulse to escape into an accessory pathway. The result of this abnormality is fast heart rhythms, which may cause the patient to faint or go into cardiac arrest.

While EP may correct some arrhythmias, others will respond best to surgical interventions that destroy or resect the areas causing the electrical snags, says Dr. Daubert. In either case, the accuracy of the detailed computerized maps of the heart made during EP studies will be invaluable to the surgeon.

The New EP Labs

More and more, physicians throughout upstate New York are requesting EP tests - the number has increased exponentially from 15 in 1988 to 700 in 1998. As a result of the demand, the Medical Center now has three full-time electrophysiology faculty (Dr. Daubert, Toshio Akiyama, M.D., David Huang, M.D., and Dr. Spencer Rosero, M.D.), and an active fellowship program.

A state-of-the-art EP laboratory, adjacent to the cardiac catheterization laboratories on the ground floor of Strong Memorial, contains all the equipment needed to analyze, record, and store electrical signals from the heart. That includes sophisticated x-ray and fluoroscopic equipment that enable the EP team to monitor the actual motion of catheters (often more than one) as they negotiate turns through the chambers of the heart.

The EP lab is a busy place. The EP team is doing 700 electrophysiology studies, including 240 ablations each year. In addition, large numbers of pacemakers and implantable defibrillators are being implanted in the lab each year as the indications for defibrillation devices continue to increase. Dr. Daubert and his team use the newest and latest technologies including 3 dimensional mapping, loop recorders, and ultrasound catheters to improve the efficacy and safety of the procedures. Dr. Huang's addition to the faculty has brought a new dimension to the EP program because of his interest in atrial arrhythmias and atrial defibrillators. "Because of our large patient and procedural volumes and our record of expertise in the area, we are one of the first centers sought out by industry when a new device is ready for clinical use," says Dr. Daubert.

Consultative Care

Beside their laboratory expertise, the physicians provide consultative services (inpatient and outpatient) along with arrhythmia outreach programs to the smaller, rural communities around Rochester. "Our goal is to provide state of the art arrhythmia care to patients regardless of their location, says Dr. Akiyama, "our outreach programs and the use of trans-telephonic pacemaker and arrhythmia monitoring makes this possible for patients regardless of where they live."

"Our electrophysiology team uses a dynamic technology to produce dramatic results for a whole array of patients with various kinds of arrhythmias," says Bradford C. Berk, M.D., PhD., Chief of Cardiology. " The success of our electrophysiology and cardiac catheterization programs has been so great that we are currently constructing another laboratory to handle the increased demand for these services."