Effect of induced chronic atrial fibrillation on exercise performance in Standardbred trotters

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Background: Atrial fibrillation (AF) is the most common arrhythmia affecting performance in horses. However, no previous studies have quantified the performance reduction in horses suffering from AF. Objectives: To quantify the effect of AF on maximum velocity (Vmax), maximum heart rate (HRmax), heart rate recovery (T100), hematologic parameters and development of abnormal QRS complexes. Animals: Nine Standardbred trotters. Methods: Two-arm controlled trial. Six horses had AF induced by means of a pacemaker and 3 served as sham-operated controls. All horses were subjected to an exercise test to fatigue before (SET1) and after (SET2) 2 months of AF or sham. The Vmax and HRmax were assessed using a linear mixed normal model. Abnormal QRS complexes were counted manually on surface ECGs. Results: Atrial fibrillation resulted in a 1.56 m/sec decrease in Vmax (P <.0001). In the AF group, HRmax ± SD increased from 226 ± 11 bpm at SET1 to 311 ± 27 bpm at SET 2. The AF group had higher HRmax at SET2 compared with controls (P <.0001), whereas no difference between the control and AF groups was observed at SET1 (P =.96). Several episodes of wide complex tachycardia were observed during exercise in 3 of the AF horses during SET2. Conclusions and Clinical Importance: Atrial fibrillation resulted in a significant reduction in performance, an increase in HR and development of abnormal QRS complexes during exercise, which may be a risk factor for collapse or sudden cardiac death.

Original languageEnglish
JournalJournal of Veterinary Internal Medicine
Issue number4
Pages (from-to)1410-1419
Number of pages10
Publication statusPublished - 2018

    Research areas

  • arrhythmia, atrial fibrillation, cardiology, exercise, heart rate, horse, performance

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ID: 203674497