Impact of device length on electrogram sensing in miniaturized insertable cardiac monitors.

Background: Little data exists on electrogram sensing in current generation of miniaturized insertable cardiac monitors (ICMs).

Objective: To compare the sensing capability of ICM with different vector length: Medtronic Reveal LINQ (~40 mm) vs. Biotronik Biomonitor III (BM-III, ~70 mm).

Methods: De-identified remote monitoring transmissions from n = 40 patients with BM-III were compared with n = 80 gender and body mass index (BMI)-matched patients with Reveal LINQ. Digital measurement of P- and R-wave amplitude from calibrated ICM electrograms was undertaken by 3 investigators independently. Further, we evaluated the impact of BMI and gender on P-wave visibility.

Results: Patients in both groups were well matched for gender and BMI (53% male, mean BMI 26.7 kg/m2, both p = NS). Median P- and R-wave amplitude were 97% & 56% larger in the BM-III vs. LINQ [0.065 (IQR 0.039-0.10) vs. 0.033 (IQR 0.022-0.050) mV, p < .0001; & 0.78 (IQR 0.52-1.10) vs. 0.50 (IQR 0.41-0.89) mV, p = .012 respectively). The P/R-wave ratio was 36% greater with the BM-III (p < .001). The 25th percentile of P-wave amplitude for all 120 patients was .026 mV. Logistic regression analysis showed BM-III was more likely than LINQ to have P-wave amplitude ≥.026 mV (OR 7.47, 95%CI 1.965-29.42, p = .003), and increasing BMI was negatively associated with P-wave amplitude ≥.026 mV (OR 0.84, 95%CI 0.75-0.95, p = .004). However, gender was not significantly associated with P-wave amplitude ≥.026 mV (p = .37).

Conclusion: The longer ICM sensing vector of BM-III yielded larger overall P- and R- wave amplitude than LINQ. Both longer sensing vector and lower BMI were independently associated with greater P-wave visibility.