B-PO03-067 PACEMAKER EXIT-BLOCK AFTER RADIOABLATION FOR VT CAUSING INAPPROPRIATE ICD SHOCKS AND BRADYCARDIC ARREST

Abstract

Stereotactic body radiation therapy (SBRT) is an emerging tool for the treatment of VT where catheter ablation has failed or is technically not feasible. Knowledge of the acute and chronic electrophysiologic sequelae, including changes in functioning of device therapy, is an evolving area. We report the first known case of inappropriate ICD shocks and severe bradycardia due to exit-block in a pacemaker dependent patient as a late-onset phenomenon following successful SBRT for VT. NA NA A 54-year-old female with a history of scar-related VT despite amiodarone therapy and chemical sympathectomy underwent successful SBRT for VT seven months prior. She was pacemaker dependent (CRT-D) with stable thresholds post-SBRT. She presented to hospital with multiple episodes of conscious ICD shocks due to R-wave double counting and misclassification as VF from interventricular conduction delay or RV loss of capture (LOC). At testing, LV and RV pacing thresholds were measured to be stable however. She later experienced severe bradycardic episodes due to intermittent LV and RV LOC that was stabilised by programming her CRT to maximum output. Definitive treatment was with insertion of a new transcutaneous RV lead and removal of LV lead. This is the first known case of delayed-onset exit-block occurring following SBRT for VT with sequelae of inappropriate ICD shocks and profound bradycardia due to dynamic conduction delay, variable pacing threshold and interplay with CRT programming. It is important that the electrophysiology team is aware of these issues.