Paroxysmal atrial fibrillation in racehorses

The paper describes five cases of atrial fibrillation detected after racing. In four of them, the arrhythmia disappeared spontaneously within 24 h and they were regarded as paroxysmal in type. In the fifth case, which won its race, the arrhythmia persisted for at least 45 h after racing. It was therefore regarded as an example of persistent atrial fibrillation. It was then treated with quinidine sulphate which restored sinus rhythm. It would seem that paroxysmal atrial fibrillation may be a cause of sudden decrease in racing performance.     

Lone atrial fibrillation in a dog

An intact male Pointer aged 9 year was found to have atrial fibrillation (AF). Thoracic radiography and echocardiography as well as routine blood work revealed no cardiac disease. Thus, the dog was diagnosed as lone AF. The arrhythmia disappeared 6 hr after the initiation of the supportive therapy, and relapse was not observed.     

Spontaneous resolution of hypothermia-induced atrial fibrillation in a dog

Objective: To report a case of spontaneous resolution of atrial fibrillation secondary to hypothermia in a dog without detectable heart disease. Case summary: An 8‐year‐old female spayed mixed breed dog presented with a history of prolonged exposure to below freezing environmental temperatures. The dog presented hypothermic (<32°C or <90°F) and minimally responsive to stimuli. The heart rate was 80 beats per minute (bpm) and irregular. Atrial fibrillation was diagnosed. The dog had pale mucous membranes, absent femoral pulses, and no obtainable blood pressure via indirect Doppler technique. Resuscitation fluids were administered and active external warming was instituted. Peripheral edema was observed during the rewarming phase and the irregular heart rate was noted to increase. The atrial fibrillation spontaneously resolved with no specific anti‐arrhythmic therapy. No underlying myocardial disease was found. The recovery of this dog was complete with a subsequent repeat of the echocardiogram and electrocardiogram (ECG) 8‐months later found to be within normal limits.     

Cardioversion of atrial fibrillation in a dog with structural heart disease using an esophageal-right atrial lead configuration

Atrial fibrillation is a common arrhythmia in dogs with structural cardiac disease and can result in significant clinical signs. Several methods of electrical cardioversion of atrial fibrillation have been described. Biphasic transthoracic cardioversion of atrial fibrillation in dogs with naturally occurring heart disease has been described in veterinary medicine and has been shown to be highly successful. In humans and research animals intracardiac and transesophageal cardioversion of atrial fibrillation has been described as an alternative to transthoracic cardioversion. While transesophageal cardioversion is very successful in humans and research animals, this technique has not been previously described in a clinical patient with naturally occurring heart disease in veterinary medicine. This report describes the use of transesophageal cardioversion in a dog with atrial fibrillation and structural cardiac disease. Cardioversion was unsuccessful using two electrodes positioned within the esophagus. Cardioversion of atrial fibrillation to normal sinus rhythm was successfully achieved and maintained using one electrode positioned within the esophagus and one electrode positioned within the right atrium using a synchronized monophasic shock of 50 J.     

Conversion of atrial fibrillation after levothyroxine in a dog with hypothyroidism and arterial thromboembolism

A six‐year‐old female spayed mixed‐breed dog was referred following a 3‐week history of lameness and progressive neurological deficits in both hindlimbs, and a 1‐week history of a cardiac arrhythmia. The dog was diagnosed with hypothyroidism, atrial fibrillation, myocardial dysfunction and arterial thromboembolism. Cardioversion occurred after 2 weeks of levothyroxine supplementation, with improved systolic function over time. To the authors’ knowledge, this is the first case reported in the veterinary or human literature documenting hypothyroidism with persistent atrial fibrillation being converted to sinus rhythm with levothyroxine as sole therapy.     

Ventricular rate control using a novel vagus nerve stimulating system in a dog with chronic atrial fibrillation

A 4-year-old, intact male Dogue de Bordeaux dog with congenital valvular pulmonic stenosis, tricuspid valve dysplasia, and chronic atrial fibrillation underwent ultrasound-guided balloon valvuloplasty in addition to pharmacological treatment. Owner compliance to prescribed pharmacotherapy proved very poor, and concerns developed regarding the ability to successfully control heart rate and symptoms using drug therapy alone. These concerns were addressed by the implantation of a novel vagal stimulation system that was programmed to prevent a ventricular rate of >145 bpm. Consequently, post-operative ventricular response rate decreased from up to 250 to 140 bpm. Successful ventricular rate control was maintained for 291 days post-operatively, following which euthanasia was elected by the owner due to persistent right-sided congestive heart failure. To the authors' knowledge, this is the first report of successful continuous rate control using a vagal stimulating system in a closed-chest, client-owned dog with chronic atrial fibrillation secondary to spontaneously occurring organic heart disease.     

Syncope secondary to transient atrioventricular block in a German shepherd dog with dilated cardiomyopathy and atrial fibrillation

This case report describes transient atrioventricular block as the etiology for syncopal events in a 6-year-old male German shepherd dog with atrial fibrillation and dilated cardiomyopathy. The arrhythmia diagnosis was obtained via Holter monitoring. Medical treatment with a sustained-release preparation of theophylline, as an additive to the standard congestive heart failure treatment (benazepril, furosemide and pimobendan) may have contributed to temporary remission of the syncopal events. However, the congestive heart failure progressed and the dog was euthanized. Veterinarians should be aware of the possibility of transient atrioventricular block causing syncope in dogs with DCM and AF and should be careful in empirically lowering the ventricular response rate if these dogs present with syncopal episodes.     

Ladder diagrams for atrial flutter and atrial fibrillation

Ladder diagrams are valuable teaching and interpretive tools in both human and veterinary electrocardiography. The purpose of this paper is to demonstrate how ladder diagrams can be used to help understand the possible mechanisms underlying atrial flutter and atrial fibrillation.     

Severe abdominal dog bite wounds in a pregnant cat

Bite wounds are one of the most common reasons for admission of cats to veterinary clinics. Appropriate wound management seems to be more important in the successful outcome of bite wound injuries than antibiotic therapy alone. This report describes a heavily pregnant cat that suffered severe abdominal bite wounds necessitating treatment with extensive surgery. A necrotic herniated kidney, abdominal wall hernias, internal peritoneal ruptures and fracture of the thirteenth rib, gravid cornu rupture, an extrauterine dead foetus and its free kidney were all observed at laparotomy. At surgery the extrauterine dead foetus was removed, and two live foetuses were retrieved by en bloc ovariohysterectomy. A right nephrectomy and partial costectomy were also performed. Two weeks postoperatively, the cat had fully recovered without a problem. Bite wounds encountered in cats, though severe and invasive, can be tolerated and extensive surgical management can result in successful outcomes even under suboptimal conditions.     

Clinically silent atrial dissociation in a dog

A Labrador retriever, presented for a routine yearly wellness exam, shows on ECG a normal sinus rhythm with first degree atrioventricular blockade and atrial dissociation (AD). A detailed cardiologic examination was performed including thoracic radiography, echocardiography and blood pressure measurement, all of which were considered normal. The dog described in this current report was re-examined several times over the subsequent 2 years and no clinical signs of heart failure, heart disease or other diseases were recognized, the AD appears to have been benign.     

Presumptive vagally-mediated atrial flutter in a dog

An asymptomatic nine-year-old Dobermann Pinscher underwent a screening for dilated cardiomyopathy. Echocardiography revealed left ventricular eccentric hypertrophy and systolic dysfunction; the rest of the echocardiographic parameters were within normal limits. Holter monitoring demonstrated sinus rhythm as the dominant cardiac rhythm during the first hours of the recording. Then, during a period of physiologically enhanced vagal tone (sleep), spontaneous development of atrial flutter (AFL) associated with variable ventricular response was documented. Alternation between AFL and paroxysmal atrial fibrillation was also observed. Subsequently, during a period of physiological increase of sympathetic tone (physical activity/excitement), spontaneous conversion of AFL to sinus rhythm occurred. In light of these findings, a presumptive diagnosis of vagal AFL was made. The images here described allow us to study the onset, behavior and termination of this intriguing electrocardiographic entity.     

Right atrial chromaffin paraganglioma in a dog

Cardiac neoplasia is relatively uncommon in canine patients, with the most common neoplasms including right atrial hemangiosarcoma and paragangliomas occurring at the heart base (i.e. chemodectomas or aortic body tumors). Intracardiac paragangliomas are rare neoplasms in humans and have seldom been documented in the veterinary literature. This report describes the clinical course and histopathological findings in an adult canine patient with an intracardiac chromaffin paraganglioma (non-adrenal pheochromocytoma) of the right atrium.     

CT diagnosis of occipital condyle fracture in a dog presented for severe cervical hyperesthesia

A 9-month-old male entire Doberman Pinscher presented with acute onset of severe cervical hyperesthesia after a fall. Neurological examination revealed a normal gait with low head carriage and severe cervical hyperesthesia. A CT scan of the cervical vertebral column revealed the presence of a comminuted fracture at the dorsomedial aspect of the right occipital condyle and sclerosis of the underlying bone. Medical management was initiated consisting of an external bandage, strict rest, and pain medication. Due to the lack of clinical improvement, the dog was euthanized 2 months after diagnosis. Histopathology of the lesion was compatible with a healing fracture.     

Idiopathic atrial fibrillation in a champion Standardised racehorse

Atrial fibrillation is described in a champion pacer which earlier had been named Australian Harness Horse of the Year as a 3-year-old in 1986-87. Prior to conversion atrial fibrillation had been present for at least 6 weeks, during which the horse had not raced. Successful treatment was achieved with two 10g doses of quinidine sulphate per oesophageal tube, after slow digitalisation with intravenous digoxin over 4d. Four hours after commencement of quinidine therapy the arrhythmia had regressed to atrial flutter and converted to sinus rhythm 10 min later. Considering his age, standard of racing and high reputation the horse's overall performance as a 5-year-old after conversion from atrial fibrillation appeared comparable to his previous performance as a 4-year-old before the disorder occurred. In one of the wins since his return to sinus rhythm, the horse recorded his fastest winning speed and created a new track record at the major Melbourne racetrack. The absence of abnormalities of atrial and atrio-ventricular conduction after the cessation of the arrhythmia, together with the horse's return to successful racing, indicate that this was case of atrial fibrillation occurring as a functional disorder without persistent atrial pathology.