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coun·ter·shock -.shäk n a therapeutic shock of electricity applied to a heart for the purpose of altering a disturbed rhythm (as in chronic atrial fibrillation) <delivering a life-saving \countershock within seconds of an arrhythmic episode (John Maurice)>
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coun·ter·shock (kounґtər-shok″) a high-intensity direct current shock delivered to the heart to interrupt ventricular fibrillation and restore synchronous electrical activity.Medical dictionary. 2011.