Implantable Cardioverter Defibrillator (ICD) | MedStar Health

Shocking the heart back into a normal rhythm

An implantable cardioverter defibrillator (ICD) is a device slightly smaller than a deck of cards that is implanted below your collarbone and monitors your heart’s rhythm. An ICD can be invaluable to protect you from sudden cardiac arrest. It works much like a defibrillator you see on TV, when a person is “shocked” with paddles, except it’s internal and automatic. When the device detects an abnormal rhythm, known as an arrhythmia , it delivers an electrical impulse, or a shock, to the heart to correct the rhythm.

Our electrophysiology program is the mid-Atlantic region’s leading referral program for patients with heart rhythm disorders. Our advanced lab lets us treat and manage even the most complex cases.

While similar, an implantable cardioverter defibrillator differs slightly from a pacemaker, another device used to control abnormal heart rhythms. A pacemaker can send electrical pulses to correct an abnormal rhythm (or “pace” the heart), but it can’t shock the heart to prevent sudden cardiac arrest as an ICD can.

If the lower chambers of your heart (known as the ventricles) do not pump at the same time and in sync with the upper chambers (known as the atria), your doctor may recommend biventricular pacing, also known as cardiac resynchronization therapy (CRT), in addition to getting an ICD. The biventricular pacemaker uses small electrical impulses to keep the right and left ventricles pumping together, while the ICD can deliver shocks as needed.

What to expect when getting an ICD?

You’ll receive local anesthesia to numb the surgical area, along with a sedative to help you relax. The device has two parts: a generator and wires, known as leads. Your doctor will make several small incisions and place the generator just under the skin below the collarbone. The leads are then inserted into a vein near the collarbone and guided to your heart, where they’re attached to the heart muscle.

The procedure takes a couple hours, and you’ll need to stay in the hospital for one or two days.

The implantable cardioverter defibrillator can be programmed to send different levels of pulses according to the severity of the problem, from low-energy pulses to a high-energy shock. Depending on the level, you may feel nothing, a painless fluttering in your chest, or an intense feeling as though you’re being hit or kicked in the chest.

ICDs also keep a record of the heart’s rhythm, which can be wirelessly transmitted to your doctor. The battery in your ICD can last up to seven years. Your doctor will monitor how the device is functioning and determine when it needs to be replaced.


Arrhythmogenic right ventricular cardiomyopathy (ARVC)

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a rare genetic abnormality of the heart muscle.

Brugada syndrome

Brugada syndrome is an inherited condition that causes an abnormal heart rhythm, known as arrhythmia.


Cardiomyopathy is a disease that weakens or changes the structure of your heart muscle, which makes it difficult for your heart to fill with and pump blood.

Catecholaminergic Polymorphic Ventricular Tachycardia (CPVT)

Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a genetic condition that mutates certain proteins, leading to an irregular or abnormal heart rhythm (arrhythmia) during physical activity or emotional stress.

Hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is a genetic condition that causes heart muscle tissue to become abnormally thick.

Ischemic cardiomyopathy

Ischemic cardiomyopathy is an enlargement and weakening of the heart’s left ventricle. This decreases the heart’s ability to pump blood throughout the body.

Long QT syndrome (LQTS)

Long QT syndrome is a disruption of your heart’s electrical activity that lengthens the recovery time between heartbeats.

Sarcoidosis (Cardiac)

Sarcoidosis causes lumps to form in your heart, lungs, or lymph nodes and can damage these organs.

Short QT syndrome (SQTS)

Short QT syndrome is a disruption of the heart’s electrical activity that causes the recharge time between heartbeats to become too short.

Sick sinus syndrome

Sick sinus syndrome is a malfunction of the heart’s sinus node, which controls heart rhythms. This causes the heart to beat too quickly or too slowly or leads to long pauses between heartbeats.

Sudden cardiac arrest

Sudden cardiac death is an unexpected death caused by sudden cardiac arrest, an electrical disturbance in the heart that stops it from beating and pumping blood to the rest of your body.


Tachycardia is a type of abnormal heart rhythm in which the heart beats much faster than it should while a person is at rest.

Tachycardia-bradycardia syndrome

Tachy-brady syndrome is a type of irregular heartbeat in which the heart fluctuates between beating too quickly and too slowly.

Ventricular fibrillation

Ventricular fibrillation is a type of heart rhythm disorder that prevents the heart from pumping blood. This is a life-threatening condition that requires immediate emergency care.

Ventricular tachycardia

Ventricular tachycardia is a type of heart rhythm disorder in which the heart’s lower chambers beat dangerously fast.


Angiogram (Angiography)

An angiogram is a special X-ray taken as a special dye is injected through a thin, flexible tube called a catheter to detect blockages or aneurysms in blood vessels.

Chest X-ray

Chest X-rays use a small dose of radiation to create pictures of the structures inside the chest, including the lungs, heart, and chest wall.

Computerized tomography (CT) scan

The cardiac computed tomography scan, or cardiac CT, uses X-rays to create three-dimensional images of your heart and blood vessels.


An echocardiogram uses high-frequency sound waves to create images of your heart.

Electrocardiogram (ECG)

An electrocardiogram, also known as an ECG, measures the heart’s electrical activity.

Event monitors

An event monitor is a small device that records the heart’s electrical activity. It’s similar to an electrocardiogram, but whereas an electrocardiogram takes place over a few minutes, an event monitor measures heart rhythms over a much longer time.

Holter monitors

A Holter monitor is a small device that records the heart’s electrical activity. It’s similar to an electrocardiogram, but whereas an electrocardiogram records over a few minutes, a Holter monitor records over the course of a day or two.

Stress tests

Stress tests are used to assess how your heart works during physical activity. There are several types of stress tests, including treadmill or bike stress tests, nuclear stress tests, stress echocardiograms, and chemically induced stress tests.

Our locations

Distance from Change locationEnter your location

MedStar Good Samaritan Hospital

5601 Loch Raven Blvd.
Baltimore, MD 21239

MedStar Southern Maryland Hospital Center

7503 Surratts Rd.
Clinton, MD 20735

MedStar Union Memorial Hospital

201 E. University Pkwy.
Baltimore, MD 21218

MedStar Franklin Square Medical Center

9000 Franklin Square Dr.
Baltimore, MD 21237

MedStar Montgomery Medical Center

18101 Prince Philip Dr.
Olney, MD 20832

MedStar Washington Hospital Center

110 Irving St. NW
Washington, DC 20010

MedStar Georgetown University Hospital

3800 Reservoir Rd. NW
Washington, DC, 20007

Additional information

Electrophysiology program

We are leaders in developing and using the latest procedures and technologies to treat heart rhythm disorders, and our cardiac electrophysiology laboratory is one of the most sophisticated in North America.

Learn More

Ask MedStar Heart & Vascular Institute

Have general questions for our heart and vascular program? Email us at If you have clinically-specific questions, please contact your physician’s office.