fibrillation

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fibrillation

 [fi″brĭ-la´shun]
1. a small, local, involuntary, muscular contraction, due to spontaneous activation of single muscle cells or muscle fibers.
2. the quality of being made up of fibrils.
3. the initial degenerative changes in osteoarthritis, marked by softening of the articular cartilage and development of vertical clefts between groups of cartilage cells.
Fibrillation on an electrocardiographic tracing. From Fenstermacher and Hudson, 1995.
atrial fibrillation a reentrant cardiac arrhythmia marked by rapid randomized contractions of the atrial myocardium, causing a totally irregular rapid atrial rate. It is recognizable on an electrocardiogram by the absence of P waves and an irregular ventricular response. It may be controlled by drug therapy or cardioversion.
ventricular fibrillation a cardiac arrhythmia marked by fibrillary contractions of the ventricular muscle due to rapid repetitive excitation of myocardial fibers with ineffectual ventricular contraction; on the surface electrocardiogram it is characterized by lack of identifiable QRS complexes. This is a frequent cause of cardiac arrest. An apparatus called a defibrillator is used to alleviate it by delivering an electric shock to the heart muscle; this depolarizes the myocardium and ends the irregular contractions so that the heart can resume normal, regular contractions.

fi·bril·la·tion

(fī-bri-lā'shŭn, fib-rĭ-),
1. The condition of being fibrillated.
2. The formation of fibrils.
3. Exceedingly rapid contractions or twitching of muscular fibrils, but not of the muscle as a whole.
4. Vermicular twitching, usually slow, of individual muscular fibers; commonly occurs in atria or ventricles of the heart as well as in recently denervated skeletal muscle fibers.

fibrillation

(fĭb′rə-lā′shən, fī′brə-)
n.
1. The forming of fibers.
2.
a. Fine, rapid twitching of individual muscle fibers with little or no movement of the muscle as a whole.
b. Rapid uncoordinated twitching movements that replace the normal rhythmic contraction of the heart and may cause a lack of circulation and pulse.

fibrillation

Cardiology Unsynchronized random and continuously changing electrical activity in the myocardium, causing inefficient pumping of blood. See Atrial fibrillation, Ventricular fibrillation.

fi·bril·la·tion

(fib'ri-lā'shŭn, fī'bri-)
1. The condition of being fibrillated.
2. The formation of fibrils.
3. Exceedingly rapid contractions or twitching of muscular fibrils, but not of the muscle as a whole.
4. Vermicular twitching, usually slow, of individual muscular fibers; commonly occurs in atria or ventricles of the heart as well as in recently denervated skeletal muscle fibers.

fibrillation

Uncontrolled, rapid and irregular contraction of muscle, especially heart muscle. Fibrillation most commonly affects the upper chambers of the heart (atrial fibrillation) causing an irregular pulse. Fibrillation of the main pumping chambers (ventricular fibrillation) prevents pumping and is rapidly fatal unless normal beating can be restored by electrical defibrillation.

fibrillation

or

ventricular fibrillation

very rapid, irregular contractions of the ventricular muscle of the HEART that cause blood circulation to stop immediately. Under suitable circumstances, ventricular fibrillation can be stopped by passing an electric current through the heart, using a cardiac defibrillator.

Fibrillation

Rapid, uncoordinated contractions of the upper or the lower chambers of the heart.

fi·bril·la·tion

(fib'ri-lā'shŭn)
1. The condition of being fibrillated.
2. The formation of fibrils.
3. Exceedingly rapid contractions or twitching of muscular fibrils.