Harvard Health Letter

Shocking news: Overdoing ICDs

They can shock a heart back into rhythm and save a life. But are too many of these heart devices being implanted?

Each month, about 10,000 Americans have implantable cardioverter-defibrillators (ICDs) put into their bodies. The main function of these devices is to sense fast or irregular heart rhythms that can be potentially fatal and then to shock the ventricles, the heart's two main pumping chambers, back into a regular, healthy heartbeat. The shock can be quite painful and may feel like a hard punch or kick in the chest. In essence, the ICD is an automated, in-the-body version of the defibrillator paddles used in cardiac emergencies.

Current models can sometimes avoid the need for a full-fledged shock by delivering short bursts of electrical pacing impulses that put the heartbeat back on track. They can also serve as pacemakers, speeding up the heart if it's beating too slowly.

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