Anaesthesia and cardiac electrophysiology.

Cardiac dysrhythmias occur in 60% or more of anaesthetized patients. While most are not immediately life-threatening, they are serious when 1) accompanied by atrioventricular (A-V) dyssynchrony and impaired myocardial performance, 2) a favourable myocardial oxygen balance is jeopardized, or 3) there is likelihood of progression to life-threatening dysrhythmias. Partial A-V dyssynchrony occurs with non-sinus origin supraventricular and A-V junctional rhythms, and complete A-V dyssynchrony with ventricular rhythms and advanced heart-block. Any tachydysrhythmia may increase the myocardial oxygen demand, and possibly reduce oxygen supply as well. Certain supraventricular tachydysrhythmias and most sustained ventricular rhythm disturbances are likely to predispose to life-threatening dysrhythmias. Thus, any cardiac rhythm disturbance should be of concern to the anaesthetist since it is a departure from normal and a sign of an untoward drug effect or altered physiological state. The purpose of this article is to summarize our current understanding of cardiac electrophysiological mechanisms, particularly how these apply to dysrhythmias that occur during anaesthesia, and to review the actions of, and indications for, antidysrhythmic drugs. A better understanding of electrophysiological mechanisms by anaesthetists should lead to improved patient management; hence, a reduced likelihood that dysrhythmias will occur that require specific drug or electrical management.