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Department of Surgery Referrals Patient Clinician Researcher

Procedures & Innovations Pacemakers & Defibrillators

Implantable Cardioverter-Defibrillators: Pacemakers & Defibrillators

An implantable cardioverter-defibrillator (ICD) is used to detect and suppress the presence of heart arrhythmias (irregular heartbeats). ICDs can convert the arrhythmia back to a normal rhythm by delivering an electrical shock to the heart.

Candidates for ICDs are people at risk for sudden death from arrhythmias, including those with:

  • A history of cardiac arrest
  • Tachycardia (the heart beats too quickly) or bradycardia (the heart beats too slowly)
  • Cardiomyopathy (diseased heart muscle)
  • Reduced pumping function of the heart

Headed by Hasan Garan, MD, Henry M. Spotnitz, MD, and Michael Argenziano, MD, Columbia University Medical Center physicians implant two major types of ICDs: pacemakers and implantable defibrillators.

What is a Pacemaker?

A pacemaker is a small, battery-operated device that helps the heart beat in a regular rhythm. It is the treatment of choice for patients with bradycardia (slow heartbeat), but is less commonly used for tachycardia (fast heartbeat). Pacemakers can be permanent (internal) or temporary (external). A pacemaker sends electrical impulses to the heart when needed to aid in the proper pumping of blood.

Pacemakers are composed of two parts: the generator and the leads. The generator stores the battery and regulatory information for the heartbeat. In an internal pacemaker, the generator is typically located beneath the collar bone. The leads are wires that extend from the generator through a large vein to the heart, delivering electrical impulses that tell the heart when to beat.

Some benefits of pacemakers include minor surgery, short hospital stay, and improved quality of life. Risks include complications during surgery such as bleeding, infection, or abnormal heart rhythms, and the interference of environmental devices, such as powerful magnets or proximal cell phones.

What is an Implantable Defibrillator?

An implantable cardiac defibrillator is a device about the size of a pager that monitors your heart rate. It is positioned below the collarbone. It is typically used to detect tachycardia and deliver a strong electrical shock to restore the heartbeat to normal. However, many defibrillators can also function as pacemakers, delivering a weaker shock to correct bradycardia as well.

A defibrillator consists of:

  • A pulse generator with batteries and a capacitor that sends a powerful shock to the heart
  • An electronic logic circuit to tell the device when to discharge
  • Lead electrodes placed in the heart to sense cardiac rhythm and deliver the shock to the heart muscle

Some benefits of implantable defibrillators include longer life, improved quality of life, and increased peace of mind. Risks include the surgical implantation itself, the potentially unnecessary shocks delivered by the device, and possible followup surgeries for generator replacement.

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