Transvenous Electrical Cardioversion of Equine Atrial Fibrillation: Patient Factors and Clinical Results in 72 Treatment Episodes

Abstract

Background: Transvenous electrical cardioversion (TVEC) has been developed for treatment of atrial fibrillation (AF) in horses. The relationship among patient variables, treatment response, and outcome in a typical referral population has not been evaluated.Hypothesis: Patient variables such as age, sex, weight, and duration of arrhythmia affect prognosis for response to treatment and the energy level at which cardioversion occurs.Animals: TVEC was applied to 72 episodes of lone AF in 63 client-owned performance horses, with the majority (54) being Standardbred racehorses.Methods: Catheterization of the right atrium (RA) and pulmonary artery (PA) through the jugular vein was used for electrode placement before horses were placed under general anesthesia. Biphasic, truncated exponential shock waves were delivered at incremental energy levels until cardioversion was achieved or a maximum single-energy level of 300 J was reached (cumulative energy 50-1,960 J). A multivariate model was constructed to evaluate influence of patient factors on cardioversion energy.Results: Cardioversion was achieved in 71 of 72 episodes (62 of 63 horses) at a mean energy of 165.43 AE 8.75 J. Cardioversion energy was higher for females than for males, and for interaction terms, weight was negatively related to energy in females and positively related in males. Age was positively related to cardioversion energy in females. No relationship was identified between duration of arrhythmia before treatment and prognosis for response or cardioversion energy.Conclusions and Clinical Importance: TVEC is highly effective in the treatment of lone AF in horses. Although age and sex influence cardioversion energy level, duration of arrhythmia does not.

Antiarrhythmic and Electrophysiologic Effects of Flecainide on Acutely Induced Atrial Fibrillation in Healthy Horses

“…However, treatment frequently is terminated because of cardiac or noncardiac adverse effects or both 9, 10. Transvenous electrical cardioversion (TVEC) is effective in restoring SR in horses without underlying cardiac disease with reported success rates of approximately 90% 11, 12. However, this procedure requires specialized hospital facilities and equipment.…”

Troponin assays in the assessment of the equine myocardium

“…Although all currently available commercial troponin I assays were designed for human patients, there are numerous reports of their use in horses with cardiac disease. Published studies have found increases in troponin I levels above presumed reference levels in horses with piroplasmosis, atypical myopathy, ruptured aortic jet lesions, structural cardiac disease and neoplasia, as well as after transvenous electrical cardioversion [1,7,[59][60][61][62]. Serum levels of cTnI showed a statistically significant increase after i.v.…”

Effect of sotalol on heart rate, QT interval, and atrial fibrillation cycle length in horses with atrial fibrillation

“…To determine measurement repeatability, 13 horses underwent the same protocol without sotalol administration. The TVEC was performed according to procedures described previously . Shocks were administered under general anesthesia using stepwise increases of the delivered energy (150, 200, 250, 300, and 360 J) until cardioversion.…”

“…Even at lower levels of exercise intensity, horses in AF might exhibit extremely high heart rates (HRs), and collapse has been described . The success rate for both pharmacological cardioversion and TVEC is very high, but AF recurrence after treatment is common with an overall rate of recurrence up to 39% at 1 year after cardioversion . The pathophysiology of AF initiation and perpetuation in horses has not yet been completely elucidated.…”