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Complete infrahisian atrioventricular block after endocavitary shock delivered by an automatic implantable cardiac
D Babuty1, J C Charniot, J P Fauchier
1Cardiology and Electrophysiology Service, Trousseau Hospital, Tours, France.
Insights
Transient infrahisian atrioventricular block can occur after defibrillator shocks in patients with left bundle branch block. Permanent block may develop, suggesting His conduction system ablation as a likely cause.
Area of Science:
- Cardiology
- Electrophysiology
- Medical Devices
Background:
- Left bundle branch block (LBBB) can predispose patients to conduction abnormalities.
- Automatic implantable cardiac defibrillators (AICDs) are used to treat life-threatening ventricular arrhythmias.
Observation:
- A patient with LBBB and a borderline H-V interval experienced transient complete infrahisian atrioventricular block after AICD cardioversion.
- The block recurred and became permanent after subsequent AICD shocks.
Findings:
- Repetitive endocavitary shocks from an AICD may lead to ablation of the His conduction system.
- Other potential mechanisms include His-Purkinje system fatigue or vagally mediated block.
Implications:
- AICD implantation in patients with LBBB may warrant consideration for backup pacing.
- Understanding the mechanisms of AICD-induced block is crucial for patient management and device selection.
Abstract:
Transient reproducible complete infrahisian atrioventricular block occurred after endocavitary cardioversion of ventricular tachycardia and ventricular fibrillation by an automatic implantable cardiac defibrillator in a patient with left bundle branch block and baseline borderline H-V interval. Six months later, a permanent complete atrioventricular block occurred after repetitive endocavitary shocks. Several hypothetical mechanisms may explain this infrahisian atrioventricular block a "fatigue" phenomenon of the His-Purkinje system, vagally mediated atrioventricular block, and/or ablation of the His conduction system. The last seems to be the most probable, which would justify implantation of an automatic implantable cardiac defibrillator with backup pacing in all patients, especially in the presence of bundle branch block.