Continuous heart rate monitoring by Holter and validation of heartrate spot-checks to measure circadian variation in heart rate in dogs with atrial fibrillation

Disrupted circadian variation (CV) increases cardiovascular risk inpeople. Atrial fibrillation (AF) is a negative prognostic indicator indogs. This study determined whether CV in heart rate(HR) occurs in pet dogs with AF, and is identifiable by HR spot-checks.Using 24-hour Holter studies from 21 AF dogs, mean and median HRswere calculated from every hour, every 4, 6 and 8 hours, and the first30 and 60 seconds of every 4th,6thand 8thhour. Values were com-pared (correlation, Bland Altman analysis) with the mesor and ampli-tude from cosinor analysis.Only mean hourly HR varied sinusoidally in 14/21 dogs (mesor133.8±29.6bpm, amplitude 15.8±6.2bpm). Mean HR had higherlevels of agreement with the mesor (r=1, p<0.0001, bias-0.12, SD0.7).Four-hourly median HR had greater agreement with the mesor(r=0.77, p=0.001, bias-1.59, SD18.8), but 30 and 60-second meanHR was superior (30s, r=0.92, p<0.0001, bias5.4, SD11.9; 60s,r=0.95, p<0.0001, bias3.3, SD9.3).Six-hourly median HR had greater agreement with the mesor (r=0.67,p=0.009, bias-2.67, SD22.1), including for 30-second intervals(r=0.96, p<0.0001, bias4.9, SD8.4). At 60-second intervals, mean HRwas superior (r=0.98, p<0.0001, bias-1.5, SD6.3).Eight-hourly mean HR had greater agreement with the mesor (r=0.57,p=0.035, bias-29.5, SD65), including for 30 and 60-second intervals(30s, r=0.86, p<0.0001, bias2.41, SD16.7; 60s, r=0.87, p<0.0001,bias1.94, SD15.7).CV in HR occurs in pet dogs despite AF but is not identified by spot-checks, which accurately estimate 24-hourly HR. Continuous HRmonitoring could help determine if lost CV in HR is a therapeutic tar-get in canine AF.DisclosuresThis abstract is a part of a research project with the title ' Use of heartrate spot-check protocol to assess 24-hour average heart rate incanine patients with atrial fibrillation'. The ECVIM-CA and PurinaInstitute Resident Research Awards have awarded us with€8000 tofund this project.