# Daily Heart Rate Variability in Dogs With Atrial Fibrillation

## TL;DR

This study finds that daily heart rate variability in dogs with atrial fibrillation on medication is low, suggesting one 24-hour recording is enough for rate control assessment.

## Contribution

The study provides new evidence on the consistency of heart rate in dogs with AF over consecutive days.

## Key findings

- Only 8% of dogs showed clinically significant heart rate variation between two 24-hour Holter recordings.
- Daily variability in ventricular arrhythmias was notable, with 28% of dogs showing a grading difference of ≥2.
- A single 24-hour Holter recording is likely sufficient for assessing rate control in dogs with AF.

## Abstract

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.

Dogs with AF, Holter‐derived mean heart rate (meanHRHolter) over 24 h is not significantly different from a subsequent, consecutive 24‐h period.

Twenty‐five dogs with AF.

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.

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.

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.