Clinical significance and management of atrioventricular block
associated with bradycardic/antiarrhythmic drug therapy: Drug-induced or
drug-revealed?
Abstract
The development of advanced atrioventricular block (AVB) in patients on
bradycardic and/or antiarrhythmic therapy (drug-related AVB) represents
a clinical challenge, raising the question of whether the AVB is
directly caused by these agents (drug-induced AVB) or if the offending
drugs exacerbate an underlying conduction system disease. Traditionally,
β-blockers, non-dihydropyridine calcium channel blockers, class Ic/III
antiarrhythmics, and digoxin have been considered reversible causes of
advanced AVB. However, recent evidence shows a weak cause-and-effect
relationship between these drugs and AVB in the elderly, along with high
recurrence rates of AVB despite initial resolution after drug
discontinuation. This may also apply to patients on high doses of these
medications, drug combinations, or with additional reversible factors
such as hyperkalemia. Despite these considerations, the European
Guidelines do not suggest permanent pacing for AVB due to transient
causes that are correctable, including bradycardic/antiarrhythmic drug
therapy. On the other hand, the American Guidelines recommend permanent
pacing for selected patients with symptomatic second- or third-degree
AVB on stable, necessary antiarrhythmic or β-blocker treatment, without
waiting for drug washout or reversibility. Notably, an accumulating body
of evidence indicates that true drug-induced AVB is rare, while
recurrence rates are high. Therefore, early permanent pacing should be
recommended, especially for frail elderly patients. Moreover, in
patients with drug-related AVB and atrial tachyarrhythmias, adopting an
early permanent pacing approach seems prudent when bradycardic and/or
antiarrhythmic treatment is necessary. Finally, delays in permanent
pacing are not justified when temporary pacing is needed, given the
increased associated risks in such cases.