B-PO02-063 ELECTROGRAM R-WAVE AMPLITUDE FOR DIFFERENT SENSING VECTORS ACROSS DIFFERENT POSTURES FOR PATIENTS WITH AN EXTRAVASCULAR IMPLANTABLE CARDIOVERTER DEFIBRILLATOR

Abstract

The extravascular (EV) ICD lead is in the substernal space. The amplitude of the sensed R-wave is less than that of transvenous ICDs. Because the lead does not move with the heart, R-wave amplitude may vary with posture. To characterize postural and temporal R-wave amplitude variability from near-field (Ring1-Ring2) and far-field (Ring1-Can) sensing vectors using data from the EV ICD clinical, pilot study. We studied 17 patients with scheduled follow-up at pre-hospital discharge, 2, 6, and 12 weeks. Unfiltered sinus rhythm R waves for Ring1-Ring2 and Ring1-Can vectors were recorded with each patient in 7 postures: supine, lying on right and left sides, prone, sitting, bending over and standing. R-wave amplitude was measured across time, posture and vector. The mean and standard deviation across patients was calculated for each posture, follow-up time, and vector. The Figure plots R-wave amplitude. The averaged R-wave amplitude was 1.86±0.93mV for Ring1-Ring2, 2.22±1.33mV for Ring1-Can. It was marginally greater for Ring1-Can than Ring1-Ring2 (p=0.076). Neither changed significantly over time (p=0.33). Posture-related changes were significant for sitting versus standing on Ring1-Can (p=0.002) and for bending over versus lying on left for Ring1-Ring2 (p=0.031). In clinical follow-up of 354 patient-months, decreases in R-wave amplitude caused transient oversensing but no inappropriate therapies. For both EV ICD sensing vectors, R-wave amplitude is stable over the first 12 weeks. Despite minor postural changes, R-wave amplitude variability did not cause inappropriate therapy.