For hearts that need a little help

Devices: Pacemakers can regulate the rhythm for those with slow or irregular heartbeats.

March 05, 2000|By Carolyn Poirot | Carolyn Poirot,Fort Worth Star-Telegram

Eleven-year-old Sarah Burkett had no clue that her heartbeat was dangerously slow -- less than 40 beats per minute -- when she went to her pediatrician last fall for the routine physical required to play sixth-grade basketball.

Doctors say her heart most likely always lagged behind (normal rate is 70-80) -- until now.

She received a pacemaker at Cook Children's Medical Center in Fort Worth, Texas, last month, and immediately her heart rate rose to normal. She was eager to get back to school and back to the sports she loves -- basketball and volleyball especially -- as quickly as possible.

A pacemaker regulates heartbeats that are either too slow or irregular by stimulating the heart muscle with precisely timed discharges of electricity.

The electrical impulses are produced by a lithium-battery-powered pulse generator connected to flexible wire leads that transmit the impulses into the heart.

Sarah's pacemaker won't limit her. In fact, she should have more energy and stamina, says Dr. Paul Gillette, the pediatric cardiologist who implanted her pacemaker on a Tuesday and discharged her that Thursday.

Once a medical novelty, pacemakers today regulate the heartbeats of 500,000 Americans: bouncing babies, active children, professional baseball players, middle-aged joggers and a lot of senior citizens.

Another 200,000 Americans have implantable cardioverter-defibrillators, which also function as pacemakers. (The defibrillator constantly monitors the heart and shocks it back into normal rhythm when it starts to race out of control or quiver uselessly.)

With the aging of the baby boomers, the number of people relying on pacemakers to keep up a healthy heart rate is expected to increase dramatically. Some pacemakers correct abnormal rhythms present at birth, like Sarah's, but the majority are implanted in older people whose heart muscles are damaged by a heart attack, coronary artery disease, infection, surgery, medications, a virus, diabetes or other diseases.

Gillette, medical director of pediatric cardiology at Cook Children's Medical Center, has implanted pacemakers in babies on the day they were born. Dr. Wade McBride, the electrophysiologist who implanted a pacemaker in Gillette's chest two years ago, has placed implants in patients as old as 100.

"The majority of patients today are a decade older than when I went through training," says McBride, who specializes in cardiac-rhythm disorders. "Now most are in their 70s. They are healthier later in life, and they don't require a pacemaker as soon."

When young children require pacemakers it is usually because their hearts were scarred before birth, often because the mother has lupus or a disease like it that produces antibodies that damage the heart's tissue, or because of open-heart surgery to correct life-threatening congenital defects.

The heartbeat irregularity that necessitated Gillette's pacemaker is related to a family history of heart block and to bypass surgery five years ago.

Pacemakers were developed in the late 1950s. Some produce electrical impulses continuously, and others are designed to trigger impulses whenever the heart rate drops too low.

The original pacemaker was a bulky, external device with wires extending from the chest to a thing that looked like a battery charger that you rolled around, Gillette says.

Over the years the implantable pacemaker has been improved with long-life batteries, and the size and weight have been greatly reduced.

"The biggest change in the last three to five years has been in pacemaker diagnostics -- what all the pacemaker can tell us about what's happening to the heart, if there are any rapid rhythms," McBride says. "In the past we didn't get much information. Now the pacemaker can record information ... and print it out so we can see exactly what's happening. It also helps us monitor the leads so we can see if there is any malfunction or damage to them."

The other big change is in sensors that help the pacemaker respond to what's happening -- in terms of activity and respiration. The pacemaker's computer integrates the two and responds to either or both.

Today's pacemakers are the world's smallest programmable computers, built on a microchip roughly four-tenths of 1 square inch.

"With battery, they are about the size of two 50-cent pieces strapped together," Gillette says. "The defibrillators are much larger -- a little bigger than a deck of cards."

Pacemakers cost about $7,000, defibrillators with pacemakers about $27,000.

Implanting a pacemaker in an adult is often an outpatient procedure, requiring less than 24 hours in the hospital or clinic. In most cases, children are given general anesthesia and spend a couple of days in the hospital.

Open-chest surgery is not required. The only incision involved is a tiny slit under the shoulder bone, where the battery and circuitry are placed. They appear as a small bulge just under the skin and often cannot be seen at all in adults.

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