Changes in R-wave amplitude at implantation are associated with gender and orientation of insertable cardiac monitor: observations from the confirm Rx™ body posture and physical activity study

Abstract

Background: Insertable cardiac monitors (ICMs) are small subcutaneously implanted devices that detect changes in R-wave amplitudes (RWAs), effective in arrhythmia-monitoring. Although ICMs have proven to be immensely successful, electrical artefacts are frequent and can lead to misdiagnosis. Thus, there is a growing need to sustain and increase efficacy in detection rates by gaining insight into various patient-specific factors such as body postures and activities.

Methods: RWAs were measured in 15 separate postures, including supine, lying on the right-side (RS) or left-side (LS) and sitting, and two separate ICM orientations, immediately after implantation of Confirm Rx™ ICM in 99 patients.

Results: The patients (53 females and 46 males, mean ages 66.62 ± 14.7 and 66.40 ± 12.25 years, respectively) had attenuated RWAs in RS, LS and sitting by ~ 26.4%, ~ 27.8% and ~ 21.2% respectively, compared to supine. Gender-based analysis indicated RWAs in RS (0.32 mV (0.09-1.03 mV), p < 0.0001) and LS (0.37 mV (0.11-1.03 mV), p = 0.004) to be significantly attenuated compared to supine (0.52 mV (0.20-1.03 mV) for female participants. Similar attenuation was not evident for male participants. Further, parasternally oriented ICMs (n = 44), attenuated RWAs in RS (0.37 mV(0.09-1.03 mV), p = 0.05) and LS (0.34 mV (0.11-1.03 mV), p = 0.02) compared to supine (0.48 mV (0.09-1.03 mV). Similar differences were not observed in participants with ICMs in the 45°-relative-to-sternum (n = 46) orientation. When assessing the combined effect of gender and ICM orientation, female participants demonstrated plausible attenuation in RWAs for RS and LS postures compared to supine, an effect not observed in male participants.

Conclusion: This is the first known study depicting the effects on RWA due to body postures and activities immediately post-implantation with an overt impact by gender and orientation of ICM. Future work assessing the cause of gender-based differences in RWAs may be critical.

Trial registration: Clinical Trials, NCT03803969. Registered 15 January 2019 - Retrospectively registered, https://clinicaltrials.gov/NCT03803969.

Keywords: Arrhythmia; Gender; Insertable cardiac monitor; Posture; R-wave amplitudes; Syncope.

Fig. 1

Flowchart depicts Confirm Rx ™ Insertable Cardiac Monitor (ICM) study plan. Details on eligibility criteria provided in methods. ICM-Insertable Cardiac Monitor

Fig. 2

R-wave amplitudes detected across all postural activities immediately following implant. Participant RWAs were assessed across 15 separate postures immediately following insertion of Confirm Rx™ ICM. On comparison to the Supine posture, lying on Right Side or Left side and Sitting were found to be significantly different in RWAs. Values for RWAs have been depicted as median and values range from minimum to maximum (n = 99). Significance was determined by Kruskal–Wallis test with p-value of < 0.05 considered significant. *** p-value of <0.001, *p-value of <0.05. Stand- Standing, Iso-Push- Isometric Push, Iso-Pull- Isometric Pull, Bal-Ballottement, CT- Chest Thumping, DP-Tip/Mid/Base- Device Pressure/Pressure on ICM at the tip, middle or lower part, AF- Arm Flaps, LHS- Left Arm Handshakes

Fig. 3

R-wave amplitude showed significant association to lying on right side-and left side compared to supine posture in female participants. RWAs were plotted as Female (n = 53) vs Male (n = 46) participants. Values for R-waves have been depicted as median and values range from minimum to maximum. Significance was determined by Kruskal–Wallis test with p-value as <0.05 considered significant. **** P-value is <0.0001, *** p-value is <0.001. Stand- Standing, Iso-Push- Isometric Push, Iso-Pull- Isometric Pull, Bal-Ballottement, CT- Chest Thumping, DP-Tip/Mid/Base- Device Pressure/Pressure on ICM at the tip, middle or lower part, AF- Arm Flaps, LHS- Left Arm Handshakes

Fig. 4

Position of ICM implant affected R-wave amplitude detected for female participants immediately following implant. RWAs for the two anatomical positions A. 45°relative to sternum (n = 46) and B. parallel to sternum (n = 44), selected for implanting Confirm Rx™ ICM. Parasternal positioning of ICM depicted differences in RS and LS postures compared to supine. Effect of gender was observed for RS and, RS and LS postures compared to Supine was observed for C. 45°relative to sternum (female n = 23 vs male n = 23) and D. parallel to sternum (female n = 26 vs male n = 18), respectively. Values for RWAs have been depicted as median and values range as minimum to maximum. Significance was determined by Kruskal–Wallis test or Mixed-effects Analysis with p-value as < 0.05 considered significant. *P-value is <0.05. RS = lying on Right Side, LS = lying on Left Side, Stand- Standing, Iso-Push- Isometric Push, Iso-Pull- Isometric Pull, Bal-Ballottement, CT- Chest Thumping, DP-Tip/Mid/Base- Device Pressure/Pressure on ICM at the tip, middle or lower part, AF- Arm Flaps, LHS- Left Arm Handshakes