Correlation between the electrocardiogram amplitude detected by an implantable cardiac monitor and the implantation depth

Abstract

Introduction: Implantable cardiac monitors (ICMs) primarily use R-R intervals in subcutaneous electrocardiograms (ECGs) to detect arrhythmias. Therefore, reliable detection of R-wave amplitude by an ICM is vital. Since ICMs detect subcutaneous ECGs, the impact of the implantation depth should be assessed.

Methods and results: This study investigated the influence of ICM depth on R-wave (ICM-R) amplitude on an ECG generated by an ICM (JOT Dx; Abbott). Overall, 58 patients who underwent ICM implantation at Kamagaya General Hospital from May 2022 to April 2023 were retrospectively reviewed. The depth-position was measured using ultrasound imaging after implantation. The depth of the ICM did not show any correlation with ICM-R amplitude (r = -.0141, p = .294). However, the distance between the ICM and the heart surface showed a significant correlation with ICM-R amplitude (r = -.581, p < .001). Body weight (r = -.0283, p = .033) and body mass index (r = -.0342, p = .009) were associated with ICM-R amplitude. S wave in the V₁ -lead was also associated with ICM-R amplitude (r = .481, p < .001). After multivariate analysis, the distance between the ICM and heart surface and the S wave in V₁ were independent determinants for the ICM-R amplitude.

Conclusion: The ICM-R amplitude may be higher with the ICM implanted deeper.

Keywords: ICM; ILR; amplitude; depth; implantable cardiac monitor; implantable loop recorder.