Not unlike a pacemaker, an implantable cardioverter defibrillator (or ICD) recognizes and monitors heart rhythms and is utilized for patients who have been diagnosed with abnormal heartbeats, which can lead to ventricular fibrillation (an awkward tightening of the heart's ventricles) and sudden cardiac arrest.

An ICD is a small (around 2 inches), battery-powered pulse generator that is generally placed under the skin near the collar bone. The device connects to the heart's right chambers by electrode wires that pass along blood vessels. In addition to its primary functions, an ICD records data about heart rhythms which can be utilized by physicians in determining treatment.

The main purpose of an ICD is to send a shock to a heart to correct a slow or fast rhythm back to normal.

While an ICD and a pacemaker are both small mechanisms implanted in the skin that utilize electrical pulses to adjust abnormal heart activity, their primary difference is a pacemaker is often a temporary correction to a slow-beating heart, while an ICD often provides permanent protection against cardiac aberrations. ICDs are also used for patients with a history of cardiac arrest or when drug therapy for dangerous heart rhythms is ineffective.

In order for the heart to function properly, its electrical system must send impulses to cause contraction, which pumps blood and oxygen through the body. If the body's electrical system is faulty, it can lead to an irregular heartbeat, which requires adjustment.

An ICD procedure can take from two to five hours. A patient is sedated and relaxed, but is not put to sleep. During most surgeries, a small incision is made near the collar bone (usually the left) and the electrode wires are guided to the heart through a vein. The pulse generator box is then placed in the upper chest and is connected to the wires.

Once the device is tested and specifications are programmed, patients are returned to their rooms for several hours of quiet rest. While some patients stay in the hospital for as long as three days, many are discharged in one day. For several weeks after their surgery, patients are advised not to raise their arm above their head on the same side as the ICD, so as not to disturb the positioning of the electrode wires.

When the wound heals, most patients are able to resume their regular routines, although lifting objects weighing more than 10 pounds is not advised until the sixth week after surgery. Regular exercise is recommended, increasing the activity as weeks pass. Regular doctor appointments are also advised. It's not uncommon for patients to feel occasional shocks, but that is a sign that the device may need fine-tuning.

Although microwaves, refrigerators, radios and computers have no effect on the ability of an ICD to do its job, patients are advised to request being hand-searched by airport security officers, as the metal component of the device can set off alarms. It is also recommended that cell phones be kept at least 6 inches from the placement of the device. Depending on the number of shocks it gives, an ICD battery can last up to six years and is easily replaced.