Uncoordinated contraction of the muscle fibres of the heart's ventricles (see arrhythmia). Causes include heart attack, electric shock, anoxia, abnormally high potassium or low calcium in the blood, and digitalis or epinephrine poisoning (see drug poisoning). Death soon follows if circulation is not restored with electric shocks (defibrillation) or drugs supplemented by chest compressions (as in cardiopulmonary resuscitation). Seealso atrial fibrillation.
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Irregular rhythm (arrhythmia) of contraction of the atria (upper heart chambers). The most common major arrhythmia, it may result as a consequence of increased fibrous tissue in the aging heart, of heart disease, or in association with severe infection. If it continues, it can permit formation of blood clots, which can block blood flow to essential organs. Emergency treatment consists of drugs such as beta-blockers or digitalis, which slow the heart's action, and anticoagulants. In addition, atrial fibrillation can be interrupted by administering electric shocks (defibrillation). Seealso ventricular fibrillation.
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Fibrillation may sometimes be used after heart surgery to stop the heart from beating while any minor leaks are stitched up.