Cardiovascular Digital Health Journal (Apr 2022)

R-wave amplitude changes with posture and physical activity over time in an insertable cardiac monitor

  • Matthew Swale, MBBS,
  • Sinny Delacroix, MD, PhD,
  • Glenn Young, MBBS,
  • Vincent Paul, MBBS,
  • Luke McSpadden, PhD,
  • Kyungmoo Ryu, PhD,
  • David Di Fiore, MBBS,
  • Maria Santos, MBBS,
  • Isabel Tan, MBBS,
  • Andre Conradie, MBChB, MMed,
  • MyNgan Duong, PhD,
  • Nisha Schwarz, PhD,
  • Stephen Worthley, MBBS, PhD,
  • Stephen Pavia, MBBS

Journal volume & issue
Vol. 3, no. 2
pp. 80 – 88

Abstract

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Background: Insertable cardiac monitors (ICMs) are accepted tools in cardiac arrhythmia management. Consistent R-wave amplitude (RWA) is essential for optimal detection. Objectives: Assess RWAs with posture/activities at insertion and at 30 days. Methods: Participants (n = 90) with Confirm Rx™ ICM had RWAs measured in different postures (supine, right-side [RS], left-side [LS], sitting, and standing) and defined physical activities (including isometric push [IPUSH] and pull) at 2 time points. ICMs were inserted in 45° to sternum and parasternal orientations. Results: There were significant reductions at insertion with RS, LS, sitting, or standing vs supine (reference position) (all P < .05). At 30 days, significant changes only occurred with LS and sitting (P < .05). Sex had an effect on RWAs, with females having significant variability at insertion (supine vs RS, LS, sitting, standing, and IPUSH; all P < .05). Males showed large RWA interpatient variabilities but minimal differences between positions vs supine. At 30 days, RS, LS, and sitting positions remained significant for females (P < .05), while in males RWAs were higher than at insertion for most postures and activities. The orientation 45° to sternum had consistently higher RWAs vs parasternal orientation at both time points (P < .0001). In females, ICM orientation had no significant effect on RWAs; however, in males the 45° to sternum produced higher RWAs. ICM movement from the insertion site showed no correlation with RWA changes. Conclusion: The mean RWAs were higher at 30 days with less interparticipant and interpostural variability; males had higher RWAs compared to females; 45° to sternum orientation had higher RWAs; and ICM migration from the insertion site did not affect RWAs.

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