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Shock the Heart Back into a Regular Rhythm

The vast majority of people whose heart stops beating unexpectedly have ventricular fibrillation. The definitive treatment for this is defibrillation using electricity to shock the heart back into a regular rhythm. Unless treatment occurs within four to six minutes, there is a high risk of death or permanent brain damage.

Tests to Determine Cause of Heart Stoppage

If the patient survives, tests will be done to determine the cause of the heart stoppage, so that preventative measures can be taken in the future. These tests may include:


Electrocardiogram (EKG or ECG)

This is a painless, noninvasive test in which patches with electrodes are attached to your skin to measure electrical impulses produced by your heart.

These impulses are recorded as waves displayed on a monitor or printed out on graph paper. It shows how fast your heart is beating and its rhythm (steady or irregular). It also records the timing of the electrical signals as they pass through each part of the heart.


This test uses sound waves to create a moving picture of your heart.

  • Provides information about the size and shape of your heart and how well your heart chambers and valves are functioning.
  • Identifies areas of poor blood flow to the heart, areas of heart muscle that aren't contracting normally, and previous injury to the heart muscle caused by poor blood flow.

The test is noninvasive and is performed by placing a probe on your chest wall. It is the same technique used in sonograms in pregnant women.

Cardiac Catheterization

A tube-like instrument inserted into the heart through a vein or artery (usually in the arm or leg) to detect problems with the heart and its blood supply.

Electrophysiology (EP) Study

Helps Pinpoint the Arrhythmia Location

Tests to help pinpoint the location, the type of arrhythmia, and how the arrhythmia responds to treatment.

  • During an EP study, you are sedated and small catheters are guided to your heart.
  • Your heart's rhythm is recorded as small amounts of electricity are delivered through the catheter.

Implantable Cardioverter Defibrillator (ICD)

Initiates Electrical Signal When Irregular Rhythm Detected

Survivors of sudden cardiac arrest are often candidates for implantable cardiac defibrillators (ICDs). Similar to a pacemaker, ICDs are devices that monitor the heart constantly, but only initiate an electrical signal when it detects a prespecified rhythmic abnormality that is dangerous.

ICDs can function as pacemakers for slow heart rates, but may also deliver high-energy electrical therapy for certain fast heart rates, called defibrillation shocks.

Surgically implanted like a pacemaker, an ICD is a miniature (but internal) version of the shock paddles used by paramedics and emergency room doctors.

Contact Information

Cardiovascular Medicine
Division of the CardioVascular Institute
Beth Israel Deaconess Medical Center
330 Brookline Avenue
Boston, MA 02215