485 Effects of Posture and Physical Activity on R-Wave Amplitude in the ConfirmRx Cardiac Monitor

Abstract

Insertable cardiac monitors are invaluable in the management of cardiac arrhythmias and, the algorithms used for optimal arrhythmia detection require consistent R-wave sensing. To determine variations in R-wave amplitudes with changing posture and physical activities. Patients implanted with a ConfirmRxTM device had R-wave amplitudes measured in different postures and physical activities at insertion and 30-days post-procedure. Seventy-nine patients with a mean age of (65.4±1.5 years) were included in the study. R wave amplitude was significantly higher in the baseline supine position (0.60±0.03 mV) compared to lying on the right-side (0.45±0.03 mV; p=0.002; 25% reduction), left-side (0.47±0.03 mV; p=0.007; 22% reduction) and sitting postures (0.48±0.03 mV; p=0.009; 20% reduction). More importantly, this decrease in R wave amplitudes was no longer significant at 30-days post-implant emphasizing that inflammation and pocket milieu play an important role in determining R wave amplitudes. Further analysis demonstrated that subjects with smaller median R wave amplitude variations of ≤0.10 mV at implant also had lesser variations at 30-days compared to the group with higher variations. There was no correlation between BMI and changes seen in R-wave amplitudes in different postures and activities This study demonstrates that posture and physical activity does not have significant effects on R wave amplitudes in the ConfirmRxTM cardiac monitor at 30 days post implant.View Large Image Figure ViewerDownload Hi-res image Download (PPT)