Sudden Cardiac Arrest

Diagnosis

Mayo Clinic offers leading-edge diagnostic and imaging technology and genetic counseling, when appropriate, to assess each patient's risk factors for sudden cardiac arrest. If a patient has experienced sudden cardiac arrest and survived, doctors will investigate and identify the cause to treat the underlying disease or condition and prevent future episodes.

Proper diagnosis begins with a physician consultation that includes a review of the patient's medical history and family medical history, including risk factors for sudden cardiac arrest. Several screening and diagnostic tests may be used to determine if a patient is at risk for sudden cardiac arrest:

Genetic Testing

Genetic testing helps detect a patient's risk for sudden cardiac arrest based on genes and family history of heart conditions such as long QT syndrome and hypertrophic cardiomyopathy. Mayo Clinic heart specialists have expertise in interpreting genetic tests in context with other medical tests to recommend personalized treatment for each patient.

Imaging Tests

Mayo Clinic offers patients the most advanced heart imaging options available:

• Chest X-ray
• Echocardiogram — This test uses sound waves to produce an image of the heart. It can help determine if the heart is pumping normally and efficiently, and illustrate the condition of the heart valves and damaged areas of the heart.
• Computed tomography (CT) scan — A CT scan produces X-rays that are used to create a visual image of the heart.
• Positron emission tomography (PET) — A PET scan creates a three-dimensional image of the heart. Before the scan, a radioactive material (tracer) is injected into the body. During a PET scan, a camera detects radiation from the patient's body, and a computer constructs an image of areas of deterioration in the heart.
• Magnetic resonance imaging (MRI) — This test uses a magnetic field to generate a three-dimensional view of the heart and heart tissue, and shows if any areas of heart tissue have been damaged.
• Nuclear scan — A nuclear scan test is used to identify blood flow problems in the heart. A radioactive material is injected into the bloodstream. Cameras monitor the flow of the material through the heart and lungs.

Clinical Laboratory Tests

Ejection fraction testing

This test assesses one of the most important sudden cardiac arrest risk factors, the heart's pumping capacity during each heartbeat, known as ejection fraction. A normal ejection fraction is between 55 percent and 70 percent. An ejection fraction of 35 percent or less indicates a greater risk of sudden cardiac arrest.

Electrophysiology testing and mapping

Mayo Clinic is recognized nationally for its experience, research and clinical contributions to advancements in electrophysiology testing. Electrophysiology tests are used to analyze heart rhythms.

During this testing, flexible, thin tubes (catheters) with electrodes are moved through blood vessels in several parts of the heart. The electrodes map how electrical signals spread through the heart. The doctor also can use the electrodes to stimulate the heart to beat at rates that can trigger arrhythmias. This method allows the doctor to locate the arrhythmia and identify the heart malfunction causing the irregular heartbeat.

Coronary catheterization (angiogram)

An angiogram shows whether arteries (blood vessels) in the heart are narrowed or blocked. The number of blocked blood vessels is another key predictor of sudden cardiac arrest. First, a dye is injected into the arteries through a long, thin tube (catheter) that is threaded through an artery in the leg back to the heart's arteries. As the arteries fill with dye, areas of blockage become noticeable.

With the catheter in place, the doctor may perform an angioplasty to unclog blockages and insert a stent (metal coil) to hold open the arteries. During this procedure, the doctor inserts a tiny balloon at the blockage site to help widen the artery. For more than 50 years, Mayo Clinic has been a leader in developing new catheter-based diagnosis techniques and therapies for patients with heart problems.

Electrocardiogram (ECG)

Sensors (electrodes) are placed on the chest, arms and legs to detect the electrical rhythms and activity of the heart. An ECG measures the timing and duration of each electrical phase in a heartbeat to determine abnormal rhythms and impulses. Abnormal heart rhythms may indicate that the heart muscle has been damaged.