Sudden cardiac arrest (SCA) is a condition in which the heart suddenly and unexpectedly stops beating. If this happens, blood stops flowing to the brain and other vital organs. SCA usually causes death if it’s not treated within minutes.
The heart has an electrical system that controls the rate and rhythm of the heartbeat. Problems with the heart’s electrical system can cause irregular heartbeats called arrhythmias.
There are many types of arrhythmias. During an arrhythmia, the heart can beat too fast, too slow, or with an irregular rhythm. Some arrhythmias can cause the heart to stop pumping blood to the body—these arrhythmias cause SCA.
SCA is not the same as a heart attack. A heart attack occurs if blood flow to part of the heart muscle is blocked. During a heart attack, the heart usually doesn’t suddenly stop beating. SCA, however, may happen after or during recovery from a heart attack.
People who have heart disease are at higher risk for SCA. However, SCA can happen in people who appear healthy and have no known heart disease or other risk factors for SCA.
Other risk factors include:
- Advancing age
- Male gender
- Personal history of arrhythmias
- Personal or family history of SCA or inherited disorders that make you prone to arrhythmias
- Drug or alcohol abuse
- Heart attack
- Heart failure
Usually, the first sign of SCA is loss of consciousness (fainting). At the same time, no heartbeat (or pulse) can be felt. Some people may have a racing heartbeat or feel dizzy or light-headed just before they faint. Within an hour before SCA, some people have chest pain, shortness of breath, nausea (feeling sick to the stomach), or vomiting.
Your doctor will perform a physical examination, ask about your symptoms and discuss your medical history. He will suggest one or more diagnostic tests. These include:
- Electrocardiogram (ECG). An electrocardiogram records electrical signals as they travel through your heart. It is the most common test used to diagnose arrhythmias. An ECG can reveal disturbances in heart rhythm or detect abnormal electrical patterns, such as a prolonged QT interval, that increase your risk of sudden death.
- Blood tests check the level of substances in the blood, such as potassium and thyroid hormone. Abnormal levels of these substances can increase your chances of having an arrhythmia.
- Chest x ray allows your doctor to check the size and shape of your heart and its blood vessels. It may also indicate whether you have heart failure.
- Echocardiogram uses sound waves to produce images of your heart. It provides information about the size and shape of your heart and how well your heart chambers and valves are working. The test also can identify 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.
- Stress test. Some heart problems are easier to diagnose when your heart is working hard and beating fast. During stress testing, you exercise to make your heart work hard and beat fast while heart tests are done. If you can’t exercise, you may be given medicine to make your heart work hard and beat fast. The heart tests done during stress testing may include nuclear heart scanning, echo, and positron emission tomography (PET) scanning of the heart.
- Coronary angiography uses dye and special x rays to show the inside of your coronary arteries. To get the dye into your coronary arteries, your doctor will use a procedure called cardiac catheterization. A thin, flexible tube called a catheter is put into a blood vessel in your arm, groin (upper thigh), or neck. The tube is threaded into your coronary arteries, and the dye is released into your bloodstream. Special x rays are taken while the dye is flowing through your coronary arteries. The dye lets your doctor study the flow of blood through your heart and blood vessels. This helps your doctor find blockages that can cause a heart attack.
- Ejection fraction testing can show how well your heart is able to pump blood— one of the most important predictors of your risk of sudden cardiac arrest.
Sudden cardiac arrest requires emergency treatment, such as immediate cardiopulmonary resuscitation (CPR) and defibrillation (delivery of an electrical shock through the chest wall to the heart, which restores normal heart rhythm).
After the patient recovers from the SCA, the doctor may prescribe medications, devices or surgery.