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

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.

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

“…al., published in 2022 [ 27 ]. Despite the contradicting outcome from PICTURE sub-study, a recent study comparing RWAs between genders at longer follow-up of ~204 days depicted lower RWAs for female participants, thus supporting the significant differences observed between the genders in this study [ 28 ].…”

“…That said, we believe that to improve sensitivity of detection and reduce noise-to-signal ratio, optimising RWA detection at implant will be key in delineating true event rates for arrythmias. Although, similar studies assessing differences in RWAs at implantation for different postures/activities is lacking, recent evidence of similar observations whilst assessing efficacy of ICM showed variations in RWAs at implantation within patients and between genders [ 27 , 28 ].…”

Implantable Loop Recorder with Long Sensing Vector: Safety, Acceptability, and Sensing Performance in Pediatric Patients

“…First-generation devices were burdened with problems such as device dimensions, artifacts, and low diagnostic power. The BIOMONITOR III demonstrated high diagnostic accuracy and sensing performance with low noise burden in the adult population [ 1 – 4 ]. The implantation technique was found to be safe and fast with a low complication rate (e.g., wound infection, device displacement or protrusion, post-implant pain and/or discomfort).…”

“…Implantable loop recorders (ILRs) are subcutaneous devices used as diagnostic tools to detect heart rhythm disorders (brady or tachyarrhythmias) through long-term continuous heart rhythm monitoring. They are helpful in establishing a symptom-rhythm correlation in patients with recurrent and/ or unexplained syncope, palpitations, cryptogenic stroke, or to record recurrences in patients undergoing catheter ablation for atrial fibrillation [1][2][3][4]. The reduction in device size and the simplification of the insertion procedure have facilitated their use even in the pediatric population; benefits from ILR implantation have been demonstrated in patients with or without congenital heart disease (CHD) or primary cardiac electrical disorders [5][6][7][8][9].…”

“…The ILR with long sensing vector is a novel device with a wider electrode spacing thanks to the addition of a long flexible antenna to the rigid case. It has been designed to overcome some issues of previous generation devices, as undersensing or noise artifacts, achieving convincing results in terms of signal quality, sensing parameters (P wave visibility and R wave amplitude), arrhythmia detection performance, and acceptability in the adult population [1][2][3][4]. No data are available on their use in the pediatric population.…”