Who Needs an Implantable Cardioverter Defibrillator?

You may need an implantable cardioverter defibrillator (ICD) if you're at risk for certain life-threatening ventricular arrhythmias, such as ventricles that beat too fast or that quiver. For example, you may be considered at high risk for a ventricular arrhythmia if you:

• Have had a ventricular arrhythmia before
• Have had a heart attack that has damaged the electrical system in your ventricles

An ICD is often recommended for people who have survived sudden cardiac arrest.

Your doctor may recommend an ICD if he or she sees signs of a ventricular arrhythmia (or heart damage that would make one likely) on the following tests.

Electrocardiogram

This simple and painless test detects and records the electrical activity of the heart. An EKG (electrocardiogram) shows how fast the heart is beating and the heart's rhythm (steady or irregular). It also records the strength and timing of electrical signals as they pass through each part of the heart.

Holter Monitor

A Holter monitor, also called an ambulatory EKG, records the electrical signals of your heart for a full 24- or 48-hour period. You wear small patches called electrodes on your chest that are connected by wires to a small, portable recorder. The recorder can be clipped to a belt, kept in a pocket, or hung around your neck.

During the 24 or 48 hours, you do your usual daily activities and keep a notebook, writing down any symptoms you have and the time they occur. You then return both the recorder and the notebook to your doctor to read the results. Your doctor can see how your heart was beating at the time you had symptoms.

The purpose of a Holter monitor is to record heart signals during typical daily activities and while sleeping, and to find heart problems that may occur for only a few minutes out of the day. Also, the Holter monitor can pick up irregular heartbeats that don't cause symptoms, but are important to treat.

Echocardiogram

This test uses sound waves to create a moving picture of your heart. An echocardiogram provides information about the size and shape of your heart and how well your heart chambers and valves are working. The test also can identify areas of poor blood flow to the heart, areas of heart muscle that aren't contracting normally, and injury to the heart muscle caused by poor blood flow.

Electrophysiology Study

For an electrophysiology study, your doctor threads a catheter (a small, flexible tube) from a blood vessel in your arm or leg up to your heart. Through the catheter, your doctor gives you certain medicines and electrically stimulates your heart to see how your heart's electrical system responds. The electrical stimulation helps to find where the heart 's electrical system is damaged.

Stress Test

Some heart problems are easier to diagnose when your heart is working harder and beating faster than when it's at rest. During stress testing, you exercise (or are given medicine if you are unable to exercise) to make your heart work harder and beat faster while heart tests, such as an EKG or echocardiogram, are performed.