Devices help hearts keep the pace.

• Position: Circulatory System - Brief article

As more people live longer with heart disease, the use of pacemakers and other heart-helping devices has grown, relate physicians at the Mayo Clinic, Rochester, Minn.

For instance, a heart rate that is slower than normal, a condition called bradycardia, is the most common reason for pacemaker implantation. Pacemakers also are used to treat heart rates that alternate between too fast and too slow, as well as rapid, irregular heartbeats. The device is implanted surgically, usually near the collarbone. Two wires, called pacing leads, connect it to the heart When the heart rate slows, speeds up, or becomes irregular, the pacemaker fires electrical pulses. The stimulation helps the heart beat at a proper rate or pace.

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Another device, an implantable cardioverter defibrillator (ICD), is designed to shock--or defibrillate--the heart, which is the only way to stop certain life-threatening rhythm problems and restore normal rhythm. Defibrillation can...