Fibrillation

Localized spontaneous, rapid contractions of individual muscle fibres. Unlike fasciculation (muscular quivering), fibrillation cannot be seen through the skin. In skeletal muscles, fibrillation is detected by an EMG. In heart muscle, it is detected by an ECG. Fibrillation usually occurs once a nerve supplying a muscle is destroyed, which causes the affected muscle to become weak and waste away. Fibrillation of the heart muscle is caused by disruption to the spread of nerve impulses through the muscle wall of a heart chamber (see atrial fibrillation; ventricular fibrillation).