Who is at risk for Sudden Cardiac Arrest (SCA)?

Cardiac arrest can happen to people who seem active and healthy, even if they have never been diagnosed with a heart problem. Unfortunately, in most cases, victims of SCA do have heart problems — they just aren’t aware of them.

The two leading contributors to cardiac arrest are:

• Coronary artery disease – 80 percent of victims of SCA have signs of coronary artery disease (narrowing of the arteries that supply blood to the heart).
• Previous heart attack – 75 percent of SCA victims show signs of a previous heart attack.

Other conditions or symptoms that may indicate increased risk for cardiac arrest include:

• Abnormal heart rate or rhythm
• Tachycardia – a rapid heart rate that comes and goes, even at rest
• Syncope – fainting without a known cause
• Low ejection fraction – with each heartbeat, the heart pumps out less than 40 percent of the blood that has collected within the left ventricle (a healthy ejection fraction is 55 percent or more).

Tests That Predict Risk

There are a number of tests that can be performed to determine if someone is in a group that is at high risk for cardiac arrest. These include:

Echocardiogram (Echo) – a painless ultrasound test in which sound waves are used to create a moving picture of the heart. The test can measure the pumping ability of the heart and identify other problems that may increase a person’s risk for SCD, including valve problems, enlarged heart chambers, and blood clots in the heart.

Electrocardiogram (EKG or ECG) – A painless test in which electrodes are attached to the patient’s chest to record the heart’s electrical activity. Certain arrhythmias or other changes in the heart’s electrical patterns could point to an increased risk of SCD.

Holter monitor – A Walkman-sized recorder that patients attach to their chest for one to two days, recording a longer sampling of their heart rhythm than on a standard electrocardiogram. After the recorder is removed, the tape is analyzed for signs of arrhythmia.

Event recorder – a pager-sized device that also records the electrical activity of the heart over a longer period of time. Unlike a holter monitor, it does not operate continuously. Instead, patients turn on the device whenever they feel their heart beating too quickly or chaotically.

Electrophysiology study (EPS) – This test is performed at a hospital or clinic. A local anesthetic is used to numb areas in the groin or neck and thin flexible wires called catheters are snaked up to the heart to record its electrical signals. During the study, the electrophysiologist (heart rhythm specialist) studies the speed and flow of electrical signals through the heart, identifies rhythm problems and pinpoints areas in the heart that may be the sources of abnormal electrical signals that trigger arrhythmias. The electrophysiologist can also determine if a patient has had a prior heart attack or evidence of prior heart damage. All of this information can help determine whether the patient is in a group at higher risk for SCD.