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 Transvenous electrical cardioversion (TVEC) is 1 of the main treatment options for atrial fibrillation (AF) in horses. Large‐scale studies on factors affecting success and prognosis have primarily been performed in Standardbred populations. Hypothesis/Objectives To determine factors affecting cardioversion success, cardioversion difficulty and recurrence in a predominant Warmblood study sample. Animals TVEC records of 199 horses. Methods Retrospective study of TVEC procedures of horses admitted for AF without severe echocardiographic abnormalities. Horse and procedural factors for success and cumulative amount of energy (≤ 600 J vs > 600 J) were determined using multivariable logistic regression. A survival analysis was performed to determine risk factors for recurrence. Results Two hundred and thirty‐one TVEC procedures were included, with a 94.4% success rate and 31.9% recurrence rate (51/160). Mitral regurgitation (OR 0.151, 95% CI 0.032‐0.715, P = .02) and AF cycle length (OR 1.05, 95% CI 1.01‐1.09, P = .02) were independent determinants for success. Catheter type (OR 0.154, 95% CI 0.074‐0.322, P < .001), previous AF episode (OR 3.10, 95% CI 1.20‐8.01, P = .02), tricuspid regurgitation (OR 2.54, 95% CI 1.25‐5.13, P = .01), and body weight (OR 1.009, 95% CI 1.003‐1.015, P = .004) were significantly correlated with cumulative amount of energy delivered. Significant risk factors for recurrence after a first AF episode were sex (stallion; HR 3.05, 95% CI 1.34‐6.95, P = .008), mitral regurgitation (HR 1.91, 95% CI 1.08‐3.38, P = .03), and AF duration (HR 1.001, 95% CI 1.0001‐1.0026, P = .04). Conclusions and Clinical Importance Both horse and procedural factors should be considered when assessing treatment options and prognosis in horses with AF.

Background: Echocardiographic reference intervals for Friesian horses are poorly described. Objectives: To obtain reference intervals for echocardiographic measurements in Friesians and compare these with Warmbloods. Animals: One hundred healthy adult Friesians and 100 healthy adult Warmblood horses. Methods: Cross-sectional study. Two-dimensional and M-mode echocardiographic images were obtained. Echocardiographic measurements, including size, area, and volumetric measurements of left atrium, left and right ventricle, aorta, and pulmonary artery, were performed. Measurements were compared between the 2 breeds using an independent samples t test with Bonferroni correction for multiple comparisons. Results: Reference ranges for standard echocardiographic measurements in Friesians were obtained. Several left ventricular measurements were significantly smaller in Friesians compared to Warmbloods, such as the left ventricular end-diastolic volume using the 4-chamber modified Simpsons' method (99.85% confidence interval for the difference [CI] = −245 to −63). Also the right ventricular end-diastolic and peaksystolic internal diameter were smaller in Friesians (99.85% CI = −1.33 to −0.6 and 99.85% CI = −1.54 to −0.76, respectively). Fractional shortening (99.85% CI = 0.61-6) and ejection fraction (99.85% CI = 0.21-4.6) were significantly larger. No structural effects of systemic hypertension, such as concentric hypertrophy, were detected. Conclusions and Clinical Importance: Our study provides reference intervals for echocardiographic measurements in Friesians useful in a clinical setting. In general, the left ventricular dimensions in Friesians were significantly smaller compared to Warmbloods, emphasizing the need for breed-specific reference intervals. Abbreviations: 4C, 4-chamber view; 4C-AL (in subscript), based on the 4-chamber area-length method; 4C-MOD (in subscript), based on the 4-chamber modified Simpson'

Rate‐adaptive single chamber pacemakers with accelerometer, closed loop stimulation (CLS), and remote monitoring functionality (Eluna 8 SR‐T, Biotronik, SE & Co, Germany) were implanted in 3 miniature donkeys with third‐degree atrioventricular block and syncope. After recovery, different pacemaker programming modes were tested at rest, during stress without physical exercise and during physical exercise. Pacing rates were compared to actual atrial rates and showed that CLS functionality allowed physiological heart rate adaptation. A transmitter installed in the stable provided wireless connection of the pacemaker to the internet. Home monitoring was activated which performed daily wireless transmission of pacemaker functional measurements to an online server allowing diagnosis of pathological arrhythmias and pacemaker malfunction from a distance. Closed loop stimulation and remote monitoring functionality resulted in nearly physiological rate adaptation and allowed remote “from‐the‐stable” patient follow‐up.

No abstract