Sudden cardiac arrest (SCA), also called sudden cardiac death, occurs when the heart develops an abnormal rhythm (arrhythmia; e.g., ventricular fibrillation, tachycardia) that causes it to stop beating suddenly.
Sudden cardiac death is not the same as a heart attack. Heart attack is characterized by an interruption in blood flow to the heart, causing the death of heart tissue. Although a heart attack can result in cardiac arrest, this condition does not necessarily cause the heart to stop beating, as is the case in SCA.
In as many as 95 percent of cases, patients who experience SCA die, usually within minutes. According to the American Heart Association (AHA), more than 300,000 people die from sudden cardiac arrest each year in the United States.
Sudden cardiac death can occur in patients who are unaware that they have an underlying medical condition. The most common cause for SCA is heart disease, also called coronary heart disease (CHD), cardiovascular disease, or coronary artery disease.
Other causes for sudden cardiac arrest include genetic (inherited) heart conditions and severe physical stress (e.g., extreme blood loss, intense exercise). SCA is the leading cause for death in young athletes. In many of these cases, adrenaline, which is a hormone released during physical activity, triggers cardiac arrest in a seemingly healthy person who may or may not have an undiagnosed heart condition. Certain medications and illegal drug use can increase the risk for sudden cardiac arrest.
Cardiac arrest can cause permanent brain damage and death in as few as 4 to 6 minutes. SCA requires immediate treatment with a device that delivers an electrical shock to the heart to restore a normal heartbeat (called a defibrillator).
If a person loses consciousness and may be experiencing cardiac arrest, call 911 immediately and begin cardiopulmonary resuscitation (CPR) until medical personnel arrive or a defibrillator can be used. Automated external defibrillators (AEDs) are easy to use and are available in some public places (e.g., airports, shopping malls, large office buildings).
Patients who survive SCA are at increased risk for future cardiac arrest. Treatment for these patients requires correcting the underlying condition; for example, by improving blood flow to the heart and preventing abnormal heart rhythms. Treatment may include medications (e.g., anti-arrhythmic drugs), surgery (e.g., cardiac catheterization, balloon angioplasty, coronary bypass, heart transplant), and/or implantable medical devices (e.g., defibrillator, pacemaker).