Sudden Cardiac Death
Sudden cardiac death (SCD) is an unexpected death due to heart problems, which occurs within one hour from the start of any cardiac-related symptoms. SCD is sometimes called cardiac arrest.
When the heart suddenly stops beating effectively and breathing ceases, a person is said to have experienced sudden cardiac death.
SCD is not the same as actual death. In actual death, the brain also dies. The important difference is that sudden cardiac death is potentially reversible. If it is reversed quickly enough, the brain will not die.
Sudden cardiac death is also not the same as a heart attack. A heart attack (myocardial infarction) is the result of a blockage in an artery which feeds the heart, so the heart becomes starved for oxygen. The part that has been starved is damaged beyond repair, but the heart can still beat effectively.
Causes and symptoms
Sudden cardiac death is usually caused by ventricular fibrillation (the lower chamber of the heart quivers instead of pumping in an organized rhythm). Ventricular fibrillation almost never returns to normal by itself, so the condition requires immediate intervention. Ventricular tachycardia can also lead to sudden cardiac death. The risk for SCD is higher for anyone with heart disease.
When the heart stops beating effectively and the brain is being deprived of oxygenated blood, a medical emergency exists.
Diagnosis of sudden cardiac death is made when there is a sudden loss of consciousness, breathing stops, and there is no effective heart beat.
When sudden cardiac death occurs, the first priority is to establish the flow of oxygenated blood to the brain. The next priority is to restore normal rhythm to the heart. Forcing air into the mouth will get oxygen into the lungs. Compressing the chest simulates a pumping heart and will get some blood flow to the lungs, brain, and coronary arteries. This method is called cardiopulmonary resuscitation (CPR). When trained help arrives, they will attempt to establish a normal heart beat by using a device called a defibrillator.
If sudden cardiac death occurs outside the hospital setting, cardiopulmonary resuscitation (CPR) must begin within four to six minutes and advanced life support measures must begin within eight minutes, to avoid brain death. CPR requires no special medical skills and training is available for the ordinary person nationwide.
Sudden cardiac death is reversible in most people if treatment is begun quickly. However, of the people who are resuscitated, 40% will have another SCD within two years if they do not receive appropriate treatment for the underlying cause of the episode.
In order to prevent sudden cardiac death, underlying heart conditions must be addressed. Medications and implantable cardioverter-defibrillators may be used.
McGood, Michael D., ed. Mayo Clinic Heart Book: The Ultimate Guide to Heart Health. New York: William Morrow and Co., Inc., 1993.
Society for the Advancement of Education. "Sudden Cardiac Death (SCD)." USA Today, Feb. 1997, 11.
American Heart Association. 7320 Greenville Ave. Dallas, TX 75231. (214) 373-6300. <http://www.americanheart.org>.
Dorothy Elinor Stonely
Defibrillator—A device which delivers a controlled electric shock to the heart to return it to normal beating rhythm.
Ventricular fibrillation—The lower chamber of the heart quivers instead of pumping in an organized way.
Ventricular tachycardia—A rapid heartbeat, usually over 100 beats per minute.