10 - Atrioventricular conduction abnormalities

Abstract

Atrioventricular (AV) block can be defined as a delay or interruption in the transmission of an impulse from the atria to the ventricles caused by an anatomical or functional impairment in the conduction system. The conduction disturbance can be transient or permanent. Symptoms in patients with AV conduction abnormalities are generally caused by bradycardia and loss of AV synchrony. Because the prognosis and, in some cases, the treatment of AV block differ depending on whether the block is within the AV node or is infranodal, determining the site of block is important. In most cases, this can be achieved noninvasively. Once symptoms and AV block are cor- related with ECG findings, further documentation by invasive studies is not required unless additional information is needed. Identifying transient or reversible causes for AV conduction disturbances is the first step in management. Once all reversible causes are excluded or treated, correlation of symptoms with ECG evidence of AV block is an essential part of the diagnostic strategy. Pacing is the mainstay of treatment for symptomatic AV block. In general, DDD pacing is the preferred pacing system in the majority of patients with AV block. Also, regardless of the pacing system used, cardiac resynchronization therapy should be considered in patients with AV block and left ventricular systolic dysfunction who are expected to require a high percentage of ventricular pacing. Direct His bundle pacing or para-Hisian pacing can enable physiological pacing in patients without distal conduction disease by recruiting the native His-Purkinje system, thus avoiding electrical dyssynchrony.