Cardiac arrest occurs when the heart stops contracting effectively. Normally, heart muscle contracts in a predictable, rhythmic manner. This rhythmic contraction is called heartbeat. It pumps blood throughout the body. When rhythmic contraction of the heart falters, cardiac output declines. Cardiac output is the rate at which the heart pumps blood. When heartbeat ceases, cardiac output is reduced to zero. The person is said to be in cardiac arrest. Cardiac arrest interrupts the flow of blood to the brain , causing unconsciousness within seconds. Death occurs if heartbeat is not restored within minutes.
A person may suffer cardiac arrest as a result of serious injury, heart attack , drowning, drug overdose, or other causes. For example, a viral infection of the heart may harm heart muscle enough to cause cardiac arrest.
Cardiac arrest may follow ventricular fibrillation (VF). Ventricular fibrillation occurs when nerve impulses that regulate heartbeat fire (activate) in a disorganized manner. The heart fibrillates (quivers) uncontrollably, unable to pump blood. More commonly, the progressive blockage of the heart arteries over many years interferes with blood flow to the heart muscle. This condition may result in VF and cardiac arrest. In rare cases, VF does not occur. Instead, heartbeat progressively slows until it ceases altogether.
Cardiac arrest is a medical emergency. Cardiopulmonary resuscitation (CPR) must begin within minutes. CPR is an emergency first-aid procedure. CPR may maintain sufficient cardiac output to keep the person alive until help arrives. If VF occurs, a defibrillator must be used. A defibrillator is a medical device used to deliver a brief electrical shock to the heart, restoring normal heart rhythm.
