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. 2021 Jun 21;37(4):1061-1068.
doi: 10.1002/joa3.12585. eCollection 2021 Aug.

Factors affecting signal quality in implantable cardiac monitors with long sensing vector

Giovanni B Forleo  1 , Claudia Amellone  2 , Riccardo Sacchi  3 , Leonida Lombardi  1 , Maria Teresa Lucciola  2 , Valentina Scotti  3 , Maurizio Viecca  1 , Marco Schiavone  1 , Daniele Giacopelli  4   5 , Massimo Giammaria  2
Affiliations

Factors affecting signal quality in implantable cardiac monitors with long sensing vector

Giovanni B Forleo et al. J Arrhythm. .

Abstract

Purpose: Electrical artefacts are frequent in implantable cardiac monitors (ICMs). We analyzed the subcutaneous electrogram (sECG) provided by an ICM with a long sensing vector and factors potentially affecting its quality.

Methods: Consecutive ICM recipients underwent a follow-up where demographics, body mass index (BMI), implant location, and surface ECG were collected. The sECG was then analyzed in terms of R-wave amplitude and P-wave visibility.

Results: A total of 84 patients (43% female, median age 68 [58-76] years) were enrolled at 3 sites. ICMs were positioned with intermediate inclination (n = 44, 52%), parallel (n = 35, 43%), or perpendicular (n = 5, 6%) to the sternum. The median R-wave amplitude was 1.10 (0.72-1.48) mV with P waves readily visible in 69.2% (95% confidence interval, CI: 57.8%-79.2%), partially visible in 23.1% [95% CI: 14.3%-34.0%], and never visible in 7.7% [95% CI: 2.9%-16.0%] of patients. Men had higher R-wave amplitudes compared to women (1.40 [0.96-1.80] mV vs 1.00 [0.60-1.20] mV, P = .001), while obese people tended to have lower values (0.80 [0.62-1.28] mV vs 1.10 [0.90-1.50] mV, P = .074). The P-wave visibility reached 86.2% [95% CI: 68.3%-96.1%] in patients with high-voltage P waves (≥0.2 mV) at surface ECG. The sECG quality was not affected by implant site.

Conclusion: In ordinary clinical practice, ICMs with long sensing vector provided median R-wave amplitude above 1 mV and reliable P-wave visibility of nearly 70%, regardless of the position of the device. Women and obese patients showed lower but still very good signal quality.

Keywords: P‐wave visibility; R‐wave amplitude; implantable cardiac monitor; implantable loop recorder; long sensing vector.

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Conflict of interest statement

Daniele Giacopelli is employee of BIOTRONIK Italia. All the other authors have no conflicts relevant to the contents of this study to disclose.

Figures

FIGURE 1
FIGURE 1
Implantation site of the device: the inclination was assessed using the midline of the sternum as reference and defined as perpendicular to sternum (0°≤ angle α ≤20°), with intermediate inclination (20°< angle α ≤60°), or parallel to sternum (60°< angle α ≤90°), while intercostal spaces were used to indicate its cranial/caudal location. Number of patients, median R‐wave amplitude (interquartile range), and proportion of patients with readily visible P waves (95% confidence interval) are reported in the text box for each device inclination
FIGURE 2
FIGURE 2
Example of Implantable cardiac monitor interrogation and sECG (blue signal) measurements: P‐wave visibility was assessed as “readily visible”, ie, visible in all beats (red arrows), while the peak‐to‐peak R‐wave amplitude was measured positioning the automatic dotted vertical lines on 3 different QRS complexes (2 pictured). The amplitude is reported in the red rectangle
FIGURE 3
FIGURE 3
Comparison between the average R‐wave amplitude manually measured on the displayed sECG in supine and standing position and the value automatically provided by the remote monitoring system. P >.05 for each paired comparison with Bonferroni correction
FIGURE 4
FIGURE 4
Subgroup analysis of the median R‐wave amplitude on ICM signal
FIGURE 5
FIGURE 5
P‐wave visibility on ICM signal with supine and standing position
FIGURE 6
FIGURE 6
Subgroup analysis of P‐wave visibility on ICM signal. Abbreviations: ECG: electrocardiogram; ICM: implantable cardiac monitor
See this image and copyright information in PMC

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