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Types of Implantable Defibrillators

A defibrillator is a device that uses electrical energy to control the beating of a heart. When a heart beat is irregular or stops, defibrillation can be used to start it properly beating again. Most people are familiar with the external defibrillator pads that are used on a person's chest. However, there are also types of defibrillators that can be surgically implanted into patients in order to help support the health of their hearts.

  1. Single Chamber ICD

    • ICD is the abbreviation that refers to this entire class of device known as implantable cardioveter defibrillators. An ICD is a defibrillating device that is implanted into the chest of a patient. The device then monitors the heartbeat of the patient. When they detect a rate that is higher than that which they were programmed to tolerate, they deliver electronic pulses to try and stop tachycardia. If that fails, the device performs defibrillation. The first generation of these devices performed only this function. More complex internal defibrillators were later developed. Later devices incorporated a combination pacemaker/ICD function. A single chamber contains a lead that is inserted in the right ventricle. This is the area of the heart which it will provide electrical stimulus to if a problem is detected.

    Dual Chamber ICD

    • The dual chamber ICD functions much the same way as the single chamber ICD does except that leads are placed in both of the chambers on the right side of the heart. With attachments to both the atrium and the ventricle, the device can stimulate both chambers as needed. The device gives energy to the atrium first, then the ventricle, preserving the normal sequence of a heartbeat.

    Bi-Ventricular ICD

    • A Bi-Ventricular ICD will also include pacemaker functionality. Instead of having two leads that are implanted in the two chambers on one side of the heart, this model of ICD implants a lead into both the right and the left ventricle. Cardiac resynchronization therapy is then administered by the device, in a method that is called bi-ventricular pacing. This is a therapy that is used when the heart gets out of sync. This does not mean that the heart is having trouble pumping, but rather that it is having trouble doing it in each chamber at the correct time.

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