Revisiting where to apply preimplant mapping to improve P‐wave sensing of insertable cardiac monitors

BACKGROUND: Insertable cardiac monitors (ICMs) are used for long‐term cardiac rhythm monitoring. They have proven useful in diagnosing arrhythmias. They are conventionally inserted at the 4th intercostal space without preimplant mapping. METHOD: We develop a new method, VisP, that finds an optimal insertion position by applying the lightweight preimplant mapping to nine candidate positions beyond the conventional ones. We retrospectively analyze consecutive 60 patients who underwent ICM insertion (Reveal LINQ™) between April 2019 and March 2021 and compare the two groups with and without VisP. RESULTS: After 9 patients were excluded because of ectopic atrial rhythms or atrial fibrillation, 51 patients were analyzed. Thirty‐one patients underwent the conventional insertion (non‐mapping), whereas 20 patients underwent VisP. VisP achieved large P‐wave amplitudes while retaining the R‐wave amplitude for all patients; in contrast, P waves were not detected for 11 patients out of the 31 patients in the non‐mapping group (35%). On average, the P‐wave amplitude was 0.065 mV for VisP, compared to 0.029 mV for the non‐mapping group (p‐value< .001). The average R‐wave amplitude was 0.69 mV for VisP and 0.71 mV for non‐mapping (p‐value = .88), indicating the R‐wave difference is insignificant between the two groups. VisP selected the 4th, 3rd, and 2nd intercostal spaces for 7, 11, and 2 patients, respectively, meaning that 13 out of the 20 cases (65%) fell out of the conventional insertion location of the 4th intercostal space. CONCLUSIONS: VisP improves the diagnostic ability of ICMs by finding an optimal position that yields reliable sensing of P waves while keeping high R‐wave sensing.