Dual‐Chamber Pacemaker Implantation via the Cephalic Vein in Healthy Equids

BackgroundAtrial 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.ObjectivesTo quantify the effect of AF on maximum velocity (V max), maximum heart rate (HRmax), heart rate recovery (T 100), hematologic parameters and development of abnormal QRS complexes.AnimalsNine Standardbred trotters.MethodsTwo‐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 V max and HRmax were assessed using a linear mixed normal model. Abnormal QRS complexes were counted manually on surface ECGs.ResultsAtrial fibrillation resulted in a 1.56 m/sec decrease in V max (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 ImportanceAtrial 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.

Section: Methodsmentioning

confidence: 99%

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

Buhl

Carstensen

Hesselkilde

et al. 2018

“…All horses (both controls and AF group) had a dual‐chamber pacemaker implanted (Assurity MRI 2272, St. Jude Medical, St. Paul, MN) with 2 bipolar leads (Tendril STS Pacing Leads 100 cm, St. Jude Medical, St. Paul, MN) in the right atrium, by a modified technique described previously . In brief, the horses were restrained in a stock, sedated with 0.01 mg/kg BW detomidine (Domosedan, Orion Pharma Animal Health, Copenhagen, Denmark) and 0.01 mg/kg BW butorphanol (Torbugesic, Orion Pharma Animal Health, Copenhagen, Denmark) followed by a constant‐rate infusion of 180–360 mL/h of 1.0 mg/mL xylazine (Xysol, ScanVet Animal Health A/S, Fredensborg, Denmark).…”

Section: Methodsmentioning

confidence: 99%

Time‐dependent antiarrhythmic effects of flecainide on induced atrial fibrillation in horses

Carstensen

Hesselkilde

Fenner

et al. 2018

BackgroundPharmacological treatment of atrial fibrillation (AF) in horses can be challenging because of low efficacy and adverse effects. Flecainide has been tested with variable efficacy.ObjectiveTo test whether the efficacy of flecainide is dependent on AF duration.AnimalsNine Standardbred mares.MethodsFactorial study design. All horses were instrumented with a pacemaker and assigned to a control or an AF group. On day 0, all horses were in sinus rhythm and received 2 mg/kg flecainide IV. Atrial fibrillation subsequently was induced in the AF group by pacemaker stimulation. On days 3, 9, 27, and 55, flecainide was administered to all horses, regardless of heart rhythm.ResultsAll horses in AF cardioverted to sinus rhythm on days 3 and 9. On day 27, 5/6 horses cardioverted, whereas only 2/6 cardioverted on day 55. The time from the start of flecainide infusion to cardioversion (range, 3–185 min, log transformed) showed linear correlation with the cumulative duration of AF (r 2 = .80, P < .0001). Flecainide induced abnormal QRS complexes in 4/6 AF horses and 1/3 controls. A positive correlation was found between heart rate before flecainide infusion and number of abnormal QRS complexes (0.14, P < .05). One horse suffered from cardiac arrest and died after flecainide infusion.Conclusions and Clinical ImportanceFlecainide is effective for cardioversion of short‐term induced AF, but the effect decreases with AF duration. Controlling heart rate may minimize adverse effects caused by flecainide, but the drug should be used with great caution.

“…In an emergency situation, placement of a temporary pacing catheter into the right ventricular apex via the jugular vein can be performed in the standing horse. The temporary catheter then can be used to maintain adequate heart rate during sedation and implantation of a permanent rate‐adaptive pacemaker . Cost and potential complications of permanent pacemaker insertion and maintenance may dissuade horse owners from this option, especially with uncertain safety implications regarding future use as a riding horse.…”

Section: Discussionmentioning

confidence: 99%

Third‐Degree Atrioventricular Block and Collapse Associated with Eosinophilic Myocarditis in a Horse

Luethy

Slack

Kraus

et al. 2017

Third‐degree atrioventricular block (AVB) and primary inflammatory myocarditis are uncommon findings in horses. The horse of this report presented for collapse at rest and was found to have multiple cardiac arrhythmias, most notably 3rd‐degree AVB. The horse was subsequently diagnosed with eosinophilic myocarditis on necropsy, a rare form of myocarditis not previously reported in horses. Despite extensive testing, an etiologic agent could not be identified, illustrating the difficulty in identifying a specific cause of myocarditis in horses.