Asystole, sometimes called flatline, is the total absence of a heart rhythm or electrical activity in the heart. It can happen quite quickly if someone has a heart attack, and it sometimes follows bradycardia or tachycardia.
In asystole, the heart is not likely to respond to defibrillation because it is already depolarized. Some emergency physicians, however, advocate the trial of defibrillation in case the rhythm is actually fine ventricular fibrillation, or a rhythm that is shockable but too small to be seen on the monitor.
When asystole is confirmed by a physician, there are still treatments that may be effective, but asystole is often the last stage of heart disease. The only possible ways to restart an asystolic heart are the administration of epinephrine, also known as adrenaline, or of atropine to block vagal tone that may be preventing the heart from beating, and finally pacing of the heart, or applying a small electric shock to the heart at a regular rate in hopes of causing it to beat.
While the heart has stopped beating, cardiopulmonary resuscitation (CPR) can be used to maintain blood and oxygen flow to vital areas of the body while treatments are applied.
Wikipedia, The Free Encyclopedia