countershock

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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.

count·er·shock

(kown'ter-shok),
An electric shock applied to the heart to terminate a disturbance of its rhythm.

countershock

/coun·ter·shock/ (koun´ter-shok″) a high intensity direct current shock delivered to the heart to interrupt ventricular fibrillation and restore synchronous electrical activity.

countershock

Etymology: L, contra + Fr, choc
a high-intensity, short-duration electric shock applied to an area of the heart, resulting in total cardiac depolarization. See also cardioversion, defibrillation.

count·er·shock

(kown'tĕr-shok)
An electric shock applied to the heart to terminate a disturbance of its rhythm.

countershock