P-wave Evidence As a Method for Improving Algorithm to Detect Atrial Fibrillation in Insertable Cardiac Monitors

Background: Frequent premature atrial contractions and sick sinus syndrome are primary causes of inappropriate atrial fibrillation (AF) detection in insertable cardiac monitors (ICMs).

Objective: The study aimed to validate an algorithm designed to reduce inappropriate AF detection on the basis of the identification of a single P wave during the cardiac cycle.

Methods: The original detection algorithm looks for evidence of AF based on differences in the pattern of R-R intervals over a 2-minute period. The improved algorithm reduces evidence for AF detection if P waves are detected. The algorithm was validated by using Holter data, which collected 2 leads of surface electrocardiogram and continuously uplinked ICM electrocardiogram over a 46-hour period. ICM detections were compared with Holter annotations to compute episode and duration detection performance.

Results: Valid Holter recordings (8442 hours) were analyzed from 206 patients. True AF was observed in 76 patients, yielding 482 true AF episodes ≥2 minutes in duration and 1191 hours of AF. The algorithm correctly identified 97.8% of the total AF duration and 99.3% of the total sinus or non-AF rhythm duration. The algorithm detected 85% (90% per-patient average) of all AF episodes ≥2 minutes in duration, and 55% (78% per-patient average) of the detected episodes had AF. AF was found in 95% of the detected episodes >1 hour. The improved algorithm reduced inappropriate episodes and duration by 46% and 55%, respectively, while also reducing appropriate episodes and duration by 2% and 0.1%, respectively.

Conclusion: An improvement in the ICM algorithm for AF detection incorporating P-wave information substantially reduced inappropriately detected episodes and duration, with minimal reduction in sensitivity for detecting AF.