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Mountain Climbing and Marathons With Heart Trouble

March 2, 2000 (Atlanta) -- Pacemakers and defibrillators already allow some people with serious heart disease to climb mountains and run marathons. Experts say such implanted devices will become even more advanced in the next decade, becoming smaller and more responsive -- perhaps even sounding alarms to warn of dangerous heart rhythms.

Both kinds of devices can help patients manage irregularities in the electrical circuitry of the heart known as arrhythmias. "Arrhythmias are common and can either be too slow or too fast," says Paul Walter, MD, director of pacemaker and arrhythmia services at the Emory Clinic and professor of cardiology at Emory University School of Medicine in Atlanta.

Abnormal heart rhythms often go unnoticed, but can cause dizziness, fainting, or palpitations, which are sensations of the heart beating forcefully or irregularly in the chest. "Pacemakers are prescribed for slow and irregular heartbeats," Walter says. "They're designed to sense interruptions in rhythm and deliver precisely timed electrical impulses for a more normal heartbeat."

Walter says pacemaker technology is continually evolving. "Pacemakers of the future will be more responsive to muscle activity and have more memory," he says. "They might also include alarm systems to warn patients of dangerous rhythms, which could be extremely important in the prevention of strokes."

Manufacturers say these and other enhancements are likely within the next 10 years.

"Responsiveness to muscle activity and breathing will continue to improve with every generation of the device," says Dan Schaber, vice president of bradyarrhythmia therapy at Medtronic Inc. Enhancements in the devices' memory, he says, mean they will eventually be able to provide physicians with patients' yearly average heart rates, to aid medical decision-making.

Wally Strauss, MD, 73, a retired internist, tells WebMD that a progressively low heartbeat would have ended his life were it not for the pacemaker he received in 1994. "I was terribly fatigued when my heart rate dropped to the thirties," he says "But my pacemaker allows me to be hyperactive. In fact, I'm training to climb Mt. Kosciusko in Australia this spring."

Heart rhythms that are too fast can also be managed with implanted devices, experts say. Implantable defibrillators give a small electric shock to the heart when the heart rhythm becomes dangerously fast or irregular.

"Fast rhythms can sometimes cause an abrupt loss of heart function or sudden cardiac arrest," says Gary Lubben, vice president of ventricular tachyarrhythmia therapy at Medtronic. "And because survivors are at risk for future episodes, an implanted defibrillator is like having an emergency room in the chest."

Lubben tells WebMD that the latest models are the size of a pager and can be implanted without opening the chest cavity. The new generation of defibrillators can also carry out some of the regulating functions of a pacemaker.