Anaesthesia in first degree atrioventricular block.

A patient with an intracardiac conduction defect characterised by first degree atrioventricular block due to slowed transmission through the atrioventricular node with increased refractoriness of the node, is described. Asymptomatic first degree block, rarely progressing to transient Wenckebach (type 1 second degree) block had been present for a period of 32 years until general anaesthesia was required, when profound bradycardia attributable to complete atrioventricular block developed abruptly. Subsequent investigations located delayed intracardiac conduction through the atrioventricular node, and indicated excess vagal activity rather than structural disease as the cause. The significance of first degree heart block is discussed in relation to other forms of atrioventricular conduction defect and the current recommendations for temporary pacing for elective general anaesthesia.