Cardiac arrest occurs when the heart suddenly stops pumping effectively. During cardiac arrest, the blood immediately stops circulating. Consciousness is lost within a few seconds, and unless blood circulation is restored within five to 10 minutes, death occurs. Cardiac arrest that leads to death is often called sudden death (or sudden cardiac death).
In the United States, about 300,000 people die each year from cardiac arrest.
Causes of Cardiac Arrest
Cardiac arrest is most commonly caused by the sudden onset of ventricular fibrillation (the most lethal of heart arrhythmias). Other cardiac arrhythmias can also produce cardiac arrest, including ventricular tachycardia and severe bradycardia.Because a cardiac arrest resulting from a cardiac arrhythmia usually occur very suddenly and unexpectedly, it is often referred to as "sudden cardiac arrest." Cardiac arrest can also result from other medical conditions, including:
- Severe loss of blood volume, as in massive bleeding
- Severely reduced blood oxygen levels (which can occur with severe lung conditions or airway obstruction)
- Hypothermia (very low body temperature)
- Severe metabolic problems (including very low or very high blood glucose levels)
- Various toxins and drugs (including cocaine and antiarrhythmic drugs)
- Cardiac tamponade (severe fluid accumulation around the heart)
- Pneumothorax (collapsed lung)
- Severe cardiac "pump failure" (in which the heart muscle simply "tires out" and ceases to function, a condition seen in people who have severe, end-stage heart failure)
Almost all cardiac arrests that occur in people who seem to be in their normal state of health until the moment of their collapse are due to ventricular fibrillation or other cardiac arrhythmias.
Treating Cardiac Arrest
Cardiac arrest is always a medical emergency.A sudden cardiac arrest - cardiac arrest caused by arrhythmias - is potentially survivable, if bystanders are nearby and they are able to act quickly enough. If you witness a possible cardiac arrest, here is what you need to do:
1. Call 911, then begin cardiopulmonary resuscitation (CPR). (If another individual is nearby, have them call 911 while you begin CPR.)
2. While while you are performing CPR, send somebody else to try to find an automatic external defibrillator (AED).
3. If your assistant returns with an AED and the paramedics still have not arrived, attach the AED and follows the instructions on the AED screen.
4. If the victim remains unconscious, continue performing CPR until the paramedics arrive.
A person's chances of surviving a cardiac arrest depend largely on whether bystanders are available who are able and willing to act. This is why it is so important for everyone to learn at least the basics of CPR - especially people who have friends or family with heart disease.
Sources:
Zheng ZJ, Croft JB, Giles WH, Mensah GA. Sudden cardiac death in the United States, 1989 to 1998. Circulation 2001; 104:2158.
Travers AH, Rea TD, et al. "Part 4: CPR overview: 2010 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care." Circulation. 2010;122(suppl 3):S676 –S684.
