How Is Sudden Cardiac Arrest Diagnosed?

Sudden cardiac arrest (SCA) happens without warning. It requires immediate emergency treatment. Doctors rarely can  diagnose SCA with medical tests as it's  happening.

Instead, SCA often is diagnosed after it happens. Doctors do this  by ruling out other causes of a person's sudden collapse.

Specialists Involved

If you're  at high risk for SCA, you may  see a cardiologist. This is a doctor  who specializes in heart diseases and conditions. Your cardiologist will work with you to  decide whether you need treatment to prevent SCA. 

Some cardiologists specialize in problems with the heart's electrical system.  These specialists are called cardiac electrophysiologists. 

Diagnostic Tests and Procedures

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

EKG (Electrocardiogram)

An EKG is a simple, painless  test that records the heart's electrical activity. This test is  used to detect and locate the source of several  heart problems.

An EKG 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. 

An EKG  may show whether you've  had a heart attack.

Echocardiography

Echocardiography (EK-o-kar-de-OG-ra-fee) is a painless  test that uses sound waves to create pictures  of your heart. It provides your doctor with  information about the size and shape of your heart and how well your heart's chambers and valves are working. 

The test also can find areas of heart muscle that aren't  contracting normally due  to poor blood flow or injury from a previous heart attack. 

There are several different types of echocardiography, including stress echocardiography. This type  is done both before and after a cardiac stress test. During this test, you exercise or take medicine (given  by your doctor) to make your heart work hard and beat fast. 

Stress echocardiography shows whether  you have decreased blood flow to your heart (a sign of coronary  artery disease).

MUGA Test or Cardiac Magnetic Resonance Imaging 

A MUGA test shows how well your heart is pumping blood. For this test, a small amount of radioactive substance is injected into a vein and travels to your heart. The substance releases energy, which special cameras outside of your body detect. The cameras use the energy to create pictures of different parts of your heart. 

Cardiac  magnetic resonance imaging (MRI) is a safe procedure that uses radio waves and magnets to create detailed pictures of your heart. The test creates images of your  heart as it is beating, producing both still and moving pictures of your heart and major blood vessels. 

Doctors use cardiac MRI to get images of  the beating heart and  to look at the structure and function of the heart. 

Cardiac Catheterization

Cardiac catheterization is a procedure used to diagnose and treat certain heart conditions. A long,  thin, flexible tube called a catheter is put into a blood vessel  in your arm,  groin (upper thigh), or neck and threaded  to your  heart. Through the catheter, your  doctor can do diagnostic tests and treatments on your heart. 

Sometimes a special dye is put into  the catheter to make  the inside of your heart  and blood vessels show up on x rays. The dye can show whether plaque has narrowed or blocked any of your coronary arteries. 

Electrophysiology Study

For an electrophysiology  study, doctors use cardiac catheterization to record how your heart's electrical system responds to certain medicines and electrical stimulation. This  helps your doctor  find where the heart's electrical system is damaged.

Blood Tests 

You may have blood tests to check the levels of potassium, magnesium, and other chemicals in your blood that play an important role in your heart's electrical signaling.