Defibrillators are also used to transform tachyarrhythmias of an atrial or ventricular origin into sinus rhythm, by selecting the synchronised cardioversion mode. Reasons for emergency cardioversion include:
• persistent atrial fibrillation/flutter;
• poor response or undesirable side-effects from drug therapy;
• patient has become haemodynamically unstable due to a tachyarrhythmia;
• sustained supraventricular tachycardias which produce signs of cardiovascular distress (Trohman & Parillo 2000).
The aim of electrical cardioversion is to depolarise the myocardium, interrupt the tachyarrhythmia and so enable the sinoatrial node to regain control with a sinus rhythm. While the techniques and safety procedures for delivering the shock are similar in most respects, there are four major differences between defibrillation and cardioversion:
• synchronisation mode;
• selection of energy levels;
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