Abstract 18926: Pre-Implant Surface EKG Screening Predicts the Arrhythmia Detection Vector Utilized by an Entirely Subcutaneous Implantable Defibrillator System

Abstract

Objectives: The subcutaneous ICD system (S-ICD) uses 3 electrodes under the skin to detect ventricular arrhythmias. Pre-implant surface EKG is performed to screen for sensing suitability prior to implant. We studied whether screening vectors pre-implant predict the final S-ICD detection vector selected post-implant. Methods: Pre- and post-implant sensing data from 51 patients who received the S-ICD at 2 centers were analyzed. The surface EKG data was collected using a Zoom™ programmer (Boston Scientific) in a configuration simulating the S-ICD sensing vectors (Figure). Surface EKG vectors deemed acceptable at screening were compared to the device-selected arrhythmia detection vector both at implant and during postural testing at hospital discharge. Results: On average, 1.8 +/- 0.6 pre-implant surface screening vectors were deemed acceptable. The detection vector selected 1) at implant and 2) at discharge matched an acceptable pre-implant vector in 80% and 78% of patients, respectively. The vector selected at discharge matched the implant vector in 56% of patients with 1 acceptable screening vector, versus 86% of patients with >1 acceptable screening vector (P=0.03). Vector at discharge was more likely to match a screening vector when the surface proxy for the “primary” sensing vector was deemed acceptable, as compared with the “alternate” sensing vector (P=0.01). Conclusions: The majority of patients had more than one acceptable sensing vector via pre-implant screening EKG. Acceptable sensing vectors determined pre-implant predict the detection vector ultimately selected after implant. In the majority of patients, postural changes at pre-discharge testing do not alter the optimal detection vector.