Arrhythmias are very common in horses, but the origin is often unknown. 1,2 Identification of the underlying mechanisms of arrhythmias requires invasive electrophysiological studies. In human subjects and dogs, under fluoroscopic guidance, a standard 'four-wire' electrophysiological diagnostic exam uses four recording catheters at specific locations such as high (superior/dorsal) right atrium, His bundle, coronary sinus and right ventricular apex. 3,4 In horses, His bundle and coronary sinus recording have not been well described. Fluoroscopy and radiography can be performed but provide limited information about exact catheter location in relation to specific anatomical structures, due to the large dimensions of the thorax. 3D insight is also difficult in horses as CT and MRI of the heart cannot be performed due to the animals' size. Therefore, four-wire electrophysiological studies cannot
Summary
Background
The number of atrial premature depolarisations (APDs) is a known risk factor for atrial fibrillation (AF) recurrence in humans.
Objectives
To evaluate if the number of APDs over a 24‐h period 5 days post cardioversion predicts AF recurrence within 1 year in horses, taking the multifactorial nature of AF into account.
Study design
Retrospective case series.
Methods
Eighty horses met these inclusion criteria: first AF episode, no AF recurrence within 5 days post cardioversion, cardioversion by transvenous electrical cardioversion (TVEC), 24‐h ECG recording and echocardiographic examination 5 days post cardioversion, no antiarrhythmic treatment during the ECG recording and follow‐up of minimum 1 year. To compare the APD burden between the recurrence and non‐recurrence group a Mann–Whitney U test was used. A multivariable survival model was built to identify additional risk factors for AF recurrence.
Results
The patient population mainly consisted of Warmbloods (93%). Twenty‐six horses (33%) experienced AF recurrence within 1 year. The number of APDs (median [range]) was significantly higher (P = 0.01) in the recurrence group (15 [1–152]) compared with the non‐recurrence group (7 [0–304]). In the multivariable survival model, APDs ≥25/24 h (hazard ratio [HR] 2.9, 95% confidence interval [CI] 1.2–6.8, P = 0.02), mitral regurgitation (HR 8.6, 95% CI 2.6–28.9, P<0.001), left atrial active fractional area change ≤9.6% (HR 2.6, 95% CI 1.0–6.5, P = 0.04) and lower body weight (HR 0.99, 95% CI 0.98–0.99, P = 0.001) were significantly associated with AF recurrence.
Main limitations
This study did not evaluate early AF recurrence within 5 days. The results cannot necessarily be extrapolated to other treatment methods, as only horses converted by TVEC were included.
Conclusions
The APD burden 5 days post cardioversion could be a useful predictive value for AF recurrence within 1 year in horses. However, other factors such as mitral regurgitation and atrial contractile function must also be taken into account.
BACKGROUND: Atrial fibrillation (AF) is the most common pathological arrhythmia in horses. After successful treatment, recurrence is common. Heart rate monitors are easily applicable in horses and some devices offer basic heart rate variability (HRV) calculations. If HRV can be used to distinguish between AF and sinus rhythm (SR), this could become a monitoring tool for horses at risk for recurrence of AF. OBJECTIVES: The purpose of this study was to assess whether in horses AF (before cardioversion) and SR (after cardioversion) can be differentiated based upon HRV parameters. STUDY DESIGN: Cohort study with internal controls. METHODS: Six HRV parameters were determined in 20 horses, both in AF and in SR, at rest (2-and 5-min and 1-and 4-h recordings) and during exercise (walk and trot, 2-min recordings). Time-domain (standard deviation of the NN intervals, root mean squared successive differences in NN intervals and triangular index), frequency domain (low/high frequency ratio) and nonlinear parameters (standard deviation of the Poincaré plot [SD]1 and SD2) were used. Statistical analysis was done using paired Wilcoxon signed rank tests and receiver operating characteristic curves. RESULTS: HRV was higher during AF compared to SR. Results for the detection of AF were good (area under the receiver operating characteristic curve [AUC] 0.8-1) for most HRV parameters. Root mean squared successive differences in NN intervals and SD1 yielded the best results (AUC 0.9-1). Sensitivity and specificity were high for all parameters at all recordings, but highest during exercise. Although AUCs improved with longer recordings, short recordings were also good (AUC 0.8-1) for the detection of AF. In horses with frequent second degree atrioventricular block, HRV at rest is increased and recordings at walk or trot are recommended. MAIN LIMITATIONS: Animals served as their own controls and there was no long-term follow-up to identify AF recurrence. CONCLUSIONS: AF (before cardioversion) and SR (after cardioversion) could be distinguished with HRV. This technique has promise as a monitoring tool in horses at risk for AF development.
Accepted ArticleThis article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record. Please cite this article as doi: 10.1111/evj.12684 This article is protected by copyright. All rights reserved.
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