Harvard Heart Letter

Keeping the heart in the right rhythm

Implantable cardiac pacemakers help millions of people live longer and feel better.

Over the past several decades, permanent cardiac pacemakers have become a lifesaving staple of cardiovascular care. These tiny electronic devices consist of a miniature computer that is inserted under the skin of the chest. The unit sends impulses through wires (called leads) that stimulate the heart muscle to beat at regular intervals.

"There are many indications for getting a pacemaker, but nearly all involve correcting a slow heart rhythm or helping the heart to beat more efficiently," says Dr. Peter Zimetbaum, associate professor of medicine at Harvard Medical School. "In some situations, a pacemaker is needed in order to prevent death. In other cases, the device is used to improve overall heart function, which in turn also improves quality of life."

Faulty signals

Normally, the electrical signal that starts the heartbeat comes from the heart's sinus node, the natural pacemaker located in the upper portion of the right atrium. From the sinus node, the heartbeat signal travels to the atrioventricular (AV) node, located between the atria. The signal then proceeds to the ventricles, where it triggers a contraction and produces a heartbeat.

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