Reliability of resting heart rate measurements in atrial fibrillation

Background: Heart rate (HR) control in atrial fibrillation (AF) is commonly guided by resting HR measurements, usually with 12-lead ECG or in-office pulse palpation. Objectives: We aimed to assess the reliability of resting HR measurements in AF patients with long-term ambulatory ECG and activity monitoring. Methods: We included patients who had recorded a full-disclosure ambulatory ECG with a mobile cardiac telemetry device equipped with an accelerometer (PocketECG, MEDICALgorithmics, Poland), with at least 95% AF. Resting HR samples (≤20 per individual/day) were collected as 10-s daytime (8 am to 8 pm) measurements after ≥10 min of rest. These samples were compared to each individual's mean daytime resting HR. Results: In 832 patients (median age 77 (interquartile range (IQR) 69–83) years, 42% women) with a median registration duration of 13 days (IQR 7–22), the population mean daytime resting HR was 85 (±15) beats per minute (bpm). A single resting HR differed from the mean daytime resting HR by a mean of ±10.4% (IQR 3.6–14.4%). When the mean daytime resting HR was ≥110 bpm, 29% of resting HR samples were < 110 bpm, and when the mean daytime resting HR was 80–109 bpm,11% of samples were ≥ 110 bpm. Resting HR measurement variability decreased to 5.3% (IQR 1.9–7.5%) when four resting HR samples were averaged. Conclusion: In patients with AF, a single resting HR measurement often differs substantially from the mean daytime resting HR. When a precise measurement is clinically relevant, repeated resting HR sampling or ambulatory monitoring can address this measurement imprecision.