How Is Sudden Cardiac Arrest Diagnosed?

Sudden cardiac arrest (SCA) happens without warning and requires immediate treatment. Rarely is there a chance to diagnose it with medical tests as it is happening. Instead, SCA is often diagnosed after it happens, by ruling out other causes of the patient's sudden collapse.

Specialists Involved

People who may be at high risk for SCA can see a cardiologist (heart specialist) who can decide whether they need preventive treatments. Some cardiologists specialize in recognizing and treating problems with the electrical system of the heart. These specialists are called electrophysiologists (e-LEK-tro-FIH-ze-ah-low-jists).

Diagnostic Tests and Procedures

Doctors use several tests to help detect the factors that put people at risk for SCA. These tests include:

• EKG (electrocardiogram). This is a simple test that records the electrical activity of the heart from the body's surface. It's used to detect and locate the source of arrhythmias and other heart problems. It may show whether you have had a heart attack.
• Echocardiogram. This test uses sound waves to create a moving picture of your heart. Echocardiogram provides information about the size and shape of your heart and how well your heart chambers and valves are functioning. The test also can identify areas of poor blood flow to the heart, areas of heart muscle that are not contracting normally, and previous injury to the heart muscle caused by poor blood flow.
• There are several different types of echocardiograms, including a stress echocardiogram. During this test, an echocardiogram is done both before and after your heart is stressed either by having you exercise or by injecting a medicine into your bloodstream that makes your heart beat faster and work harder. A stress echocardiogram is usually done to find out if you have decreased blood flow to your heart (coronary artery disease).
• MUGA test or magnetic resonance imaging (MRI) heart scans. These scans can detect whether the heart has a reduced ability to pump blood.
• Cardiac catheterization. In this procedure, a thin, flexible tube (called a catheter) is passed through an artery in the groin (upper thigh) or arm to reach the coronary arteries in the heart. Your doctor can use the catheter to determine pressure and blood flow in the heart's chambers, collect blood samples from the heart, and examine the coronary arteries by x ray.
• Electrophysiology study. For this study, doctors also use cardiac catheterization to see how the heart's electrical system responds to certain medicines and electrical stimulation. The electrical stimulation helps to find where the heart's electrical system is damaged.