Montefiore Einstein Center for Heart and Vascular Care – Treatment/Procedures – Implantable Cardioverter Defibrillator – New York

Montefiore Medical Center was one of the first hospitals in the world to implant a cardioverter defibrillator, which, like the pacemaker, is a small device implanted beneath the skin near the collarbone to help maintain a normal heart rhythm.

An implantable cardioverter defibrillator (ICD) may be inserted if during an electrophysiology study the cardiologist was able to induce a ventricular arrhythmia, a sign of electrical malfunction in the heart. A variety of common cardiac conditions can lead to an electrical malfunction and the resulting need for an ICD. Some of these conditions are:

• Ventricular fibrillation – a life-threatening condition in which the ventricles contract in a rapid, chaotic rhythm and cannot pump blood to the body
• Ventricular tachycardia – a serious condition in which the ventricles cause a fast heartbeat
• Heart failure – a condition in which the heart is unable to pump blood effectively to meet the body's metabolic needs
• Predisposition – being at risk for sudden cardiac arrest due to family history or other known conditions

The device is programmed to manage heartbeat speed and has a number of life-saving functions that can be programmed by a physician based on the patient's needs for restoring a normal heart rhythm. The therapies include anti-tachycardia pacing (ATP), cardioversion (light shock), defibrillation (stronger shock) and backup pacing.

ATP impulses are the first line of defense and are delivered in order to correct and restore normal rhythm by overtaking a fast, irregular rhythm. Most people are unaware when this therapy is being delivered. Light shock impulses, by their very name, are light shocks to the heart that can be felt, but not as strongly as the defibrillation, which is the strongest therapy delivered by an ICD.

The ICD can also be programmed to function as a basic pacemaker as needed. Sometimes, after a shock is delivered, the heart may beat too slowly. The ICD has a "backup" pacemaker, which can stimulate the heart to beat faster until the normal heart rhythm returns. Additionally, an ICD can act as a pacemaker not only after a shock is delivered, but also any time the heart rate drops below a pre-programmed rate.

An ICD can also record and store information about your heart rhythm and therapies delivered by the ICD for your physician to review. As with a pacemaker, regular appointments are necessary in order for a physician to adjust the settings when needed, thus ensuring you maintain a healthy heart rhythm.