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Objectives: To describe the electrocardiographic characteristics of ventricular tachycardia arising from the right ventricular outflow tract and the particular association between this arrhythmia and the presence of localised right ventricular outflow tract enlargement in English bulldogs., Methods: Five English bulldogs were referred with a history of syncope or cardiogenic shock. In all dogs, 12-lead surface ECG, thoracic radiograph and echocardiography were collected. In all but one dog 24-hours Holter monitoring and signal-averaged ECGs was examined and in one dog electrophysiological study and radiofrequency catheter ablation of the VT substrate was performed., Results: Documented arrhythmias included a single sustained monomorphic wide QRS tachycardia in four dogs, and an alternans of two different monomorphic forms in one dog. Mean QRS duration during tachy-cardia was 91·6 ±9·83 milliseconds. QRS complexes manifested a left bundle branch block morphology and an inferior axis (81 ±13·73°). R wave notching was present in the caudal (inferior) leads in three tachy-cardias. Lead I was negative in 3 of 6, positive in 1 of 6 and isodiphasic in 2 of 6. Lead aVL was negative in 5 of 6 and positive in 1 of 6. Signal-averaged electrocardiograms revealed late potentials in three dogs. Echocardiography showed a localised right ventricular outflow tract enlargement in all dogs. Cardiac map-ping established two sites of origin of ventricular tachycardia within the right ventricular outflow tract in one dog: caudal free-wall and cranial-septal., Clinical Significance: The presence of a localised right ventricular outflow tract enlargement and ventricular tachycardia with left bundle branch block morphology could suggest segmental arrhythmogenic right ven-tricular cardiomyopathy in the English bulldog., (© 2011 British Small Animal Veterinary Association.)

Objectives: To retrospectively assess the long-term outcome for dogs that were presented with collapse, syncope or exercise intolerance for which an underlying cause is not identified., Methods: The clinical records of animals presenting to two practices were assessed. Dogs which presented for collapse, syncope or exercise intolerance at least 6 months previously and did not receive a definitive diagnosis despite investigation were included. Follow-up of these cases was carried out by conducting telephone interviews with the owners., Results: One hundred and fifty-three cases were successfully followed up. Clinical signs had resolved in 64 cases (42%), 35 dogs (23%) were continuing to exhibit clinical signs, although 22 of these had improved without medical intervention. In 17 cases (11%), a diagnosis had subsequently been made or treatment was being administered and 37 dogs (24%) had died. Of the deaths, 18 (12%) were considered to be related to the original presentation. The overall prevalence of death and deterioration related to the problems investigated was 16·2% of cases. Death in boxers was significantly more common than in other breeds (36%)., Clinical Significance: Death and deterioration are uncommon outcomes for dogs other than boxers presenting with collapse, syncope and exercise intolerance for which a definitive diagnosis cannot be made., (© 2010 British Small Animal Veterinary Association.)

Objective: The purpose of this study was to investigate whether implantable loop recorders could be used in the diagnosis of unexplained collapse in dogs., Methods: The medical records of six dogs presented to the University of Liverpool Small Animal Teaching Hospital between May 2003 and October 2006 for further evaluation of intermittent syncopal episodes, collapse or episodic weakness, were reviewed. All these dogs underwent standard investigations and had implantable loop recorders placed., Results: A provisional diagnosis of supraventricular tachycardia was made in one dog, and diagnoses of exclusion of arrhythmogenic right ventricular cardiomyopathy and idiopathic epilepsy was made in two dogs. One dog suffered no further syncopal episodes, a diagnosis was not reached in another dog and the final dog was lost to follow-up., Clinical Significance: The implantable loop recorder can be used successfully for the diagnosis of unexplained collapse in dogs.

The Reveal is an implantable loop recorder. It is increasingly being used in humans for the diagnosis of unexplained syncope where it is believed that cardiac arrhythmias may play a role, and may have great potential for investigating syncope in veterinary patients. The purpose of this report is to describe the first use of the device in the diagnosis of unexplained syncope in a cat.

A four-and-a-half-year-old neutered male shorthair cat was presented with a three-week history of episodic fainting. Twenty-four hour electrocardiographic (Holter) recording revealed frequent prolonged episodes of complete atrioventricular (AV) block with ventricular standstill. The fainting episodes coincided with the longest periods of ventricular inactivity. A permanent transjugular pacemaker was placed to prevent further life-threatening episodes of syncope. Three months after discharge, the patient was re-presented with sudden onset dyspnoea associated with chylothorax and electrocardiography showed a third degree (complete) AV block. The pacemaker was reprogrammed in view of the third degree AV block and the chylous effusion was successfully treated by repeated thoracocentesis and long-term diuresis. However, the patient's general condition deteriorated progressively and the cat was euthanased five and a half months after implantation of the pacemaker.