fibrillation

the rapid non-synchronized contraction or TREMOR of MUSCLES in which individual bundles of fibres contract independently. It applies especially to HEART muscle and disrupts the normal beating so that the affected part is unable to pump BLOOD . Two types of fibrillation may occur, depending on which muscle is affected. Atrial fibrillation, often resulting from ATHEROSCLEROSIS or rheumatic heart disease, affects the muscles of the atria and is a common type of ARRHYTHMIA . The heartbeat and pulse are very irregular and cardiac output is maintained by the contraction of the ventricles alone. With ventricular fibrillation, the heart stops pumping blood, so this is, in effect, cardiac arrest. The patient requires immediate emergency resuscitation or death ensues within minutes.