Harvard Heart Letter

Who needs an implantable cardioverter-defibrillator?

ICDs save lives, but sometimes medications and other options make more sense.

The heart's ability to beat steadily for a lifetime is a testament to tough muscle and an amazing electrical system. Sometimes, though, the heart veers into an abnormal rhythm. Two potentially deadly ones are ventricular tachycardia and ventricular fibrillation. One effective way to abort these rhythms and restore a normal one is with an electrical shock.

Once limited to the cart-carried generators and plate-sized paddles you see on television medical dramas ("Clear!"), so-called shock boxes are now compact enough to fit into a small pocket of muscle under the collarbone. Today's implantable cardioverter-defibrillators (ICDs) can constantly monitor the heart and nudge it, or jolt it if necessary, back into a healthy rhythm.

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