Overview of Pacemakers and ICDs

To correct abnormal heart rhythms (arrhythmias) and help your heart beat more efficiently, your doctor may recommend a device implant. The most common device implants are pacemakers and implantable cardioverter defibrillators (ICDs). These devices are usually implanted in the cath lab but may also be implanted during surgery.

Pacemakers: Pacemakers are usually used to correct heart rhythms that are too slow or are out of synch. A pacemaker typically has two parts: a pulse generator, and one or more leads. The pulse generator includes a battery and circuits that create electrical pulses. The leads are wires that send the electrical pulses to your heart.

Implantable Cardioverter Defibrillators (ICDs): ICDs are used to prevent or treat fast or chaotic arrhythmias called ventricular tachycardia (v-tach) or ventricular fibrillation (v-fib). Here's how they work:

  • If your heart begins to beat abnormally fast, the ICD first alters the pacemaker's speed to bring the heart back to a normal rhythm. This is called antitachycardia pacing, and you won't feel anything while it happens. If this doesn't work, the ICD sends a low-energy electrical impulse (shock) to your heart at the same time as your regular heartbeat. This is called cardioversion, and you may feel this.
  • If your heart is beating dangerously fast or chaotically, the ICD sends a high-energy shock to your heart muscle to restore a normal rhythm. This is called defibrillation. You will probably feel quite a jolt when this happens.
Pacemakers and ICDS are placed in a small pocket under the skin below the collarbone. Leads are threaded through a vein in the upper chest and guided to the heart with the help of x-ray monitors.

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