PO-04-058 AN UNUSUAL CASE OF ATRIAL SENSING BY A DEFIBRILLATOR LEAD CAUSING ASYSTOLE

Abstract

Integrated bipolar transvenous defibrillator leads (IL) offer advantages over dedicated bipolar defibrillator leads (BL): IL have a simplified construction and are less prone to anodal stimulation. A potential problem for the IL is oversensing due to a large sensing area. We present a case of an IL with intermittent asystole treated by exchange of the IL for a BL. N/A N/A A 51-year-old female with hypertrophic cardiomyopathy received a Boston Scientific (BS) dual chamber ICD in 2011 with a IL (BS 0185) for VT and intermittent heart block. In May 2022, she underwent an uncomplicated generator change. Six months later she presented with presyncopal events. Hospital telemetry showed DDD pacing with intermittent lack of ventricular output and no escape rhythm. There was no evidence of lead dislodgement and manipulation of the pocket did not reproduce an event. Device interrogation showed normal and stable lead thresholds and impedances. She was now pacemaker dependent. Spontaneous asystole was captured by the intracardiac electrogram (IEGM) demonstrating atrial far-field sensing with inhibition of RV pacing. Decreasing the RV sensitivity did not resolve the issue. We urgently turned on “Electrocautery Protection Mode” (DOO 60 and V Tachy Mode-OFF) restoring 100% dual chamber pacing and capture. We suspected that atrial far field sensing was due to the IL design. The size and position of the sensing anode can allow for far-field atrial sensing and inhibition of RV output. Intraoperative manipulation and testing of the generator and leads showed normal parameters. The patient underwent extraction of the IL, and a BL (Medtronic 6935m) was implanted. A BL was selected due to its distal, and closely spaced, pace/sense electrode design. The device was reprogrammed to her prior settings with no further episodes or symptoms occurring. This case shows an unusual problem with the IL design. Capturing this event by IEGM was diagnostic. Reducing the IL sensitivity is not optimal, making the patient vulnerable to undersensing of ventricular fibrillation. Discussion with BS Technical Services confirms that this phenomenon is rarely seen and more likely to occur in patients with a small RV. We suspect that changes in body habitus, a small RV cavity, and progression of heart block exposed the problem years after implant. Exchange of a IL with a BL provided a lasting solution.