Daily Heart Rate Variability in Dogs With Atrial Fibrillation

ABSTRACT Background Daily variability of heart rate in 24‐h Holter recordings in dogs with atrial fibrillation (AF) receiving antiarrhythmic drugs (AAD) is unknown and could influence medical decisions. Hypothesis/Objectives Dogs with AF, Holter‐derived mean heart rate (meanHRHolter) over 24 h is not significantly different from a subsequent, consecutive 24‐h period. Animals Twenty‐five dogs with AF. Methods Prospective, descriptive, multicenter study. MeanHRHolter rate and ventricular arrhythmias (VAs) were prospectively analyzed after starting AAD. Clinically relevant difference (defined as ≥ 10 bpm in the meanHRHolter), success of rate control (defined as meanHRHolter ≤ 125 bpm). A Bland–Altman analysis and intra‐class correlation coefficient (ICC) were calculated to compare two consecutive 24‐h Holter recordings. VAs percentage difference [(maximum daily value‐minimum daily value)/maximum daily value × 100] and grading variability between recordings were also investigated. Results Small BIAS with ICC 0.98 (95% confidence interval [CI] 0.95–0.99) on meanHRHolter with no statistical difference between two consecutive 24‐h Holter recordings (95% CI [−2.84–2.92], degree of freedom 24, p = 0.98). Only 2/25 dogs (8%; 95% CI [2%–25%]) had clinically significant variation, while 1/25 (4%; 95% CI [0%–20%]) dogs showed different classifications in the success of rate control between the consecutive recordings. The VAs percentage difference was 52%, with 7/25 (28%; 95% CI [14%–47%]) dogs showing a VAs grading difference of ≥ 2. Conclusion and Clinical Importance The daily heart rate variability in dogs with AF receiving AAD is low, suggesting that a single 24‐h Holter recording is adequate to assess rate control. Daily variability might be an important consideration when assessing VAs in dogs with concomitant AF.