Sudden cardiac arrest (SCA) is a sudden, abrupt loss of heart function. Most sudden cardiac arrest episodes are caused by the rapid and chaotic activity of the heart known as ventricular tachycardia (VT) or ventricular fibrillation (VF). These are diseases of the heart’s electrical conduction system that should not be confused with a heart attack (myocardial infarction), which is caused by a blocked blood vessel leading to loss of blood supply to a portion of the heart muscle. However some people may experience SCA during a heart attack.
Sudden cardiac arrest is a major health problem. According to the American Heart Association, SCA affects approximately 450,000 people each year in the United States. SCA kills more Americans than lung cancer, breast cancer, and AIDS combined. SCA victims range from young children to the elderly and the average response time to an emergency call is six to 12 minutes.
The major risk factor for SCA is coronary heart disease. Most people who have SCA have some degree of coronary heart disease; however, many people may not know that they have coronary heart disease until SCA occurs. Usually their coronary heart disease is “silent”—that is, it has no signs or symptoms. Because of this, doctors and nurses have not detected it.
Many people who have SCA also have silent, or undiagnosed, heart attacks before sudden cardiac arrest happens. These people have no clear signs of heart attack, and they don’t even realize that they’ve had one. Other risk factors for SCA include a personal history of arrhythmias, a personal or family history of SCA or inherited disorders that make the individual prone to arrhythmias, drug or alcohol abuse, heart attack, or heart failure.
If you've already had SCA, you're at high risk of having it again. Research shows that an implantable cardioverter defibrillator (ICD)reduces the chances of dying from a second SCA. An ICD is surgically placed under the skin in your chest or abdomen. The device has wires with electrodes on the ends that connect to your heart's chambers. The ICD monitors your heartbeat.
If the ICD detects a dangerous heart rhythm, it gives an electric shock to restore the heart's normal rhythm. Your doctor may give you medicine to limit irregular heartbeats that can trigger the ICD.
An ICD isn't the same as a pacemaker. The devices are similar, but they have some differences. Pacemakers give off low-energy electrical pulses. They're often used to treat less dangerous heart rhythms, such as those that occur in the upper chambers of the heart. Most new ICDs work as both pacemakers and ICDs.
Cardiac arrest is reversible in most victims if it’s treated within minutes, but the only effective treatment is the delivery of an electrical shock. With the development of hospital coronary care units in the 1960s, it was found that electrical devices that shocked the heart could turn an abnormally rapid rhythm into a normal one.