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A 14-year-old spayed female mixed-breed cat weighing 3.4 kg was admitted to the Tokyo University of Agriculture and Technology Animal Medical Center for syncope after vomiting. Echocardiography, electrocardiography, and thoracic radiography revealed no abnormalities. Holter electrocardiography showed a paroxysmal high-grade atrioventricular block coinciding with the vomiting. Based on these findings, the cat was diagnosed as having situational syncope with paroxysmal high-grade atrioventricular block triggered by vomiting, which improved with antiemetic treatment alone. The cat subsequently died of chronic kidney disease approximately 3 years and 4 months after the initial diagnosis. This is the first reported case of situational syncope triggered by vomiting in a cat.

A 10-year-old spayed female shih tzu dog was brought to the hospital because of recurring syncope that occurred simultaneously with a cough. Physical examination did not reveal an abnormal heart rhythm or abnormal heart sounds. Electrocardiography revealed sinus arrest of 4.7 s with intermittent escape beats during coughing. Additional examinations, including thoracic radiography, clinical pathology, and echocardiography, revealed no abnormalities of concern. Forty-eight-hour Holter monitoring captured 1 syncopal episode following severe coughing, during which the longest sinus arrest lasted 16 s with intermittent escape beats. This observation confirmed our strong suspicion that coughing was the cause of varying degrees of sinus arrest in this dog. Theophylline, codeine, and short-term prednisolone were prescribed to treat the dog's cough. The daily episodes of syncope ceased and coughing decreased. Subsequent 48-hour Holter monitoring revealed no abnormal pauses, and the owner did not report syncope. Theophylline and codeine were continued for 5 mo, during which time no syncope occurred. To our knowledge, this case provides the first clear evidence of a correlation between cough-induced sinus arrest and syncope in a veterinary patient, as confirmed by Holter monitoring and electrocardiography. Key clinical message: Cough-induced severe bradycardia and syncope were identified in a shih tzu dog. After the antitussive medication was adjusted, the signs resolved., (Copyright and/or publishing rights held by the Canadian Veterinary Medical Association.)

A 14-year-old intact male West Highland White Terrier weighing 6.9 kg was admitted to the Tokyo University of Agriculture and Technology Animal Medical Center with the complaint of syncope after showing signs of nausea during feeding. Sinus arrest induced by deglutition was confirmed using a Holter electrocardiography test. However, the clinical symptoms significantly improved after implantation of a permanent pacemaker. Seven months after implantation, the dog died from acute pancreatitis, a cause unrelated to the syncope. Immediately after its death, the heart, lungs, gastrointestinal tract, and other organs were dissected and examined histopathologically. The brain was also examined using magnetic resonance imaging. Examination results led to the diagnosis of swallowing-induced situational syncope.

Background: Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a myocardial disease with an increased risk for ventricular arrhythmias. The condition, which occurs in Boxer dogs, shares phenotypic features with the human disease arrhythmogenic cardiomyopathy (ACM) suggesting its potential as a natural animal model. However, there are currently no universally accepted clinical criteria to diagnose ARVC in Boxer dogs. We aimed to identify diagnostic criteria for ARVC in Boxer dogs defining a more uniform and consistent phenotype., Methods and Results: Clinical records from 264 Boxer dogs from a referral veterinary hospital were retrospectively analysed. ARVC was initially diagnosed according to the number of ventricular premature complexes (VPCs) in the 24-hour-Holter-ECG in the absence of another obvious cause. Dogs diagnosed this way had more VPCs, polymorphic VPCs, couplets, triplets, VTs and R-on-T-phenomenon and syncope, decreased right ventricular function and dilatation in comparison to a control group of all other Boxer dogs seen by the Cardiology Service over the same period. Presence of couplets and R-on-T-phenomenon on a 24h-ECG were identified as independent predictors of the diagnosis. A diagnosis based on ≥100 VPCs in 24 hours, presence of couplets and R-on-T phenomenon on a 24h-ECG was able to select Boxer dogs with a phenotype most similar to human ACM., Conclusion: We suggest the diagnosis of ARVC in Boxer dogs requires two out of the three following criteria: presence of ≥ 100 VPCs, presence of couplets or R-on-T-phenomenon on a 24 h-ECG. This results in a uniform phenotype similar to that described in human ACM and may result in the adoption of the term ACM for this analogous condition in Boxer dogs.

Background: Syncope is a transient loss of consciousness occasionally occurring in dogs with advanced myxomatous mitral valve disease (MMVD)., Objective: (1) To study ECG changes during syncopal episodes in dogs with advanced MMVD and (2) to compare the occurrence of arrhythmias and changes in heart rate variability (HRV) between dogs with advanced MMVD with and without a history of syncope., Animals: Forty-three privately owned dogs (<15 kg) with advanced MMVD: 21 with and 22 without a history of syncope., Methods: Prospective study with dogs recruited for an evaluation including history, physical examination, echocardiography, and arrhythmia and HRV analysis performed on 24-hour Holter recordings., Results: A syncopal episode was observed during Holter monitoring in 4 dogs: 3 dogs had sinus rhythm and 1 dog had sinus arrest followed by escape rhythm. An arrhythmia variable representing sinus arrhythmia was significantly lower in dogs with a history of syncope than in those without (P = .008). Eight of 26 HRV variables were significantly different between dogs with and without a history of syncope., Conclusions and Clinical Importance: Compared with dogs without a history of syncope, dogs with advanced MMVD and a history of syncope did not have a higher occurrence of arrhythmias, but had less sinus arrhythmia, and had changes in HRV variables representing decreased overall HRV, decreased parasympathetic, and increased sympathetic modulation of heart rate., (Copyright © 2014 by the American College of Veterinary Internal Medicine.)

The most common presenting clinical signs of lung-lobe torsion include dyspnea, tachypnea, lethargy, and anorexia. Tussive syncope secondary to lung-lobe torsion has not been documented. This article describes the presentation, diagnosis, management, and outcome of a pug with tussive syncope secondary to lung-lobe torsion.

Cardiovascular disease in general, and cardiac arrhythmias specifically, is common in great apes. However, the clinical significance of arrhythmias detected on short-duration electrocardiograms is often unclear. Here we describe the use of an implantable loop recorder to evaluate cardiac rhythms in 4 unanesthetized adult chimpanzees (Pan troglodytes), 1 with a history of possible syncope and 3 with the diagnosis of multiform ventricular ectopy (ventricular premature complexes) and cardiomyopathy. The clinical significance of ventricular ectopy was defined further by using the implantable loop recorder. Arrhythmia was ruled out as a cause of collapse in the chimpanzee that presented with possible syncope because the implantable loop recorder demonstrated normal sinus rhythm during a so-called syncopal event. This description is the first report of the use of an implantable loop recorder to diagnose cardiac arrhythmias in an unanesthetized great ape species.

Background: Episodic collapse in horses has equine welfare and human safety implications. There are, however, no published case series describing this syndrome., Objectives: To characterize the cause and outcomes for horses referred for investigation of episodic collapse., Animals: Twenty-five horses referred for investigation of single or multiple episodes of collapse., Methods: Retrospective study. Clinical records from the Dick Vet Equine Hospital, University of Edinburgh from November 1995 to July 2009 were searched using the following keywords: collapse, collapsing, fall, syncope. Collapse was defined as an incident in which the horse lost postural tone with or without progression to recumbency and with or without loss of consciousness. Long-term follow-up information was obtained by telephone conversation with the owner., Results: A final diagnosis was reached in 11 cases, namely cardiac arrhythmia (4), right-sided heart failure (1), hypoglycemia (2), generalized seizures (2), and sleep disorder (2). A presumptive diagnosis was reached in 8 cases, namely neurocardiogenic syncope (5), exercise-induced pulmonary hemorrhage (2), and generalized seizures (1). No diagnosis was reached in 6 cases despite comprehensive investigations. Three horses were euthanized at presentation. Treatment was attempted in 9 horses with 6 cases having successful outcome before discharge. Follow-up information was available for 14 of 19 horses discharged from the hospital. Only 1 of these horses was observed to collapse after discharge., Conclusions and Clinical Importance: Definitive diagnosis was more likely to be reached in cases with multiple episodes of collapse. Horses in which 1 episode of collapse occurred did not necessarily collapse again., (Copyright © 2010 by the American College of Veterinary Internal Medicine.)

Objective: To evaluate the diagnostic value of an implantable loop recorder (ILR) in dogs with unexplained syncope., Design: Prospective case series., Animals: 12 dogs with recurrent unexplained syncope., Procedures: An ILR was surgically inserted in a pocket created in the subcutaneous tissues of the left hemithorax of each dog. The ILRs were programmed for manual and automatic activation, and event analysis and programming were performed at 3-month intervals and after each syncopal episode., Results: The ILR was manually activated in 7 of 12 dogs at least once within 45 to 218 days (median, 120 days) after implantation. Four dogs had syncopal episodes associated with sinus tachycardia followed by sinus bradycardia and asystolic pauses. Two dogs had ventricular tachycardia, and 1 dog had sinus node dysfunction with prolonged sinus arrest that coincided with loss of consciousness and falling. Four dogs had no additional syncopal episodes after implantation of the ILR. In the remaining dog, the owner was unable to activate the ILR during the only syncopal episode observed for that dog after ILR implantation. In all 12 dogs, analysis of ECG traces after automatic activation of recording revealed normal cardiac rhythms., Conclusions and Clinical Relevance: Data gained after manual activation of an ILR provided valuable diagnostic and prognostic information in almost all dogs with unexplained syncopal episodes by confirming or disproving an association between syncope and arrhythmias. However, detection of disturbances in cardiac rhythm after automatic activation did not appear to improve the diagnostic value for an ILR implanted in dogs.

A 9-year-old male neutered Devon Rex cat was presented for continued investigations following a 7-year history of recurrent syncope. Previous diagnostic tests, including 24h (Holter) electrocardiographic monitoring, had failed to identify the aetiology of such episodes, and former empirical treatment with atenolol had not provided satisfactory control of the clinical signs. A conclusive diagnosis was eventually achieved using an implantable loop recorder (Reveal), which identified paroxysmal supraventricular tachycardia (SVT) associated with a syncopal episode. Treatment with oral sotalol was instituted and, 18 months after initiation of anti-arrhythmic therapy, no further syncopal episodes have been observed by the cat's owners.

Background: Syncope is a recognized problem in Boxers and often is the result of rapid ventricular tachycardia (VT). Affected dogs may have echocardiographic evidence of dilated cardiomyopathy, but frequently have normal echocardiograms. Although VT is probably the most common cause of syncope in Boxers, neurocardiogenic bradycardia can also occur., Objective: We describe 7 Boxers with comorbid VT and neurocardiogenic bradycardia, wherein the syncope was secondary to bradycardia rather than VT., Animals: Seven Boxers were selected from a larger population of Boxers with Holter-documented VT because these dogs had documented bradycardia at the time of syncope., Methods: Retrospective study., Results: Although all dogs had Holter-documented VT, the etiology of the syncopal episodes was consistent with neurocardiogenic bradycardia., Clinical Importance: Neurocardiogenic bradycardia or VT can occur as isolated problems in Boxers. In some Boxers, VT and potential or manifest neurocardiogenic bradycardia coexist. The administration of a beta-blocker or sotalol to such dogs can aggravate or precipitate neurocardiogenic bradycardia-related syncope.

Objective: To evaluate the effect of 4 antiarrhythmic treatment protocols on number of ventricular premature complexes (VPC), severity of arrhythmia, heart rate (HR), and number of syncopal episodes in Boxers with ventricular tachyarrhythmias., Design: Randomized controlled clinical trial., Animals: 49 Boxers., Procedure: Dogs with > 500 VPC/24 h via 24-hour ambulatory ECG (AECG) were treated with atenolol (n = 11), procainamide (11), sotalol (16), or mexiletine and atenolol (11) for 21 to 28 days. Results of pre- and posttreatment AECG were compared with regard to number of VPC/24 h; maximum, mean, and minimum HR; severity of arrhythmia; and occurrence of syncope., Results: Significant differences between pre- and posttreatment number of VPC, severity of arrhythmia, HR variables, or occurrence of syncope were not observed in dogs treated with atenolol or procainamide. Significant reductions in number of VPC, severity of arrythmia, and maximum and mean HR were observed in dogs treated with mexiletine-atenolol or sotalol; occurrence of syncope was not significantly different between these 2 treatment groups., Conclusions and Clinical Relevance: Treatment with sotalol or mexiletine-atenolol was well tolerated and efficacious. Treatment with procainamide or atenolol was not effective.

Objective: To determine the clinical usefulness of cardiac event recording in evaluating dogs and cats with unexplained syncope, episodic collapse, or intermittent weakness., Design: Retrospective study., Animals: 58 dogs and 2 cats., Procedure: Medical records and electrocardiographic rhythm strips obtained by cardiac event recordings were reviewed. Cardiac rhythm data from the event recordings were classified as diagnostic or nondiagnostic. Diagnostic yield was calculated by dividing the number of animals for which cardiac event recording was diagnostic by the total number of animals undergoing cardiac event recording., Results: For 51 animals, cardiac event recording was classified as diagnostic; therefore, overall diagnostic yield was 85%. Diagnostic yield was lower for animals without underlying structural heart disease (75.5%) than for animals with structural heart disease (95.6%). A specific arrhythmia was identified as the cause of clinical signs in 18 of the 51 (35%) animals for which cardiac event recording was diagnostic. Cardiac arrhythmia was definitively excluded as the cause of clinical signs in the remaining 33 (65%) animals in which cardiac event recording was diagnostic., Conclusions and Clinical Relevance: Results indicate that cardiac event recording had a high diagnostic yield in dogs and cats examined because of unexplained syncope, episodic collapse, or transient weakness and ataxia, regardless of whether animals did or did not have an underlying structural heart disease. Diagnostic yield of cardiac event recording was higher than that reported previously for Holter monitoring.

The objective of this study was to evaluate retrospectively the clinical utility of ambulatory (Holter) electrocardiographic monitoring in syncopal dogs and to compare the Holter recording with the clinic electrocardiogram (ECG) in these animals. Fifty Holter reports and 44 medical records from 44 dogs were evaluated. A syncopcal episode occurred during monitoring in 24% of the recordings. No obvious relationship was found between the frequency of syncope occurring before Holter recording and the likelihood of a dog having an episode during recording. Holter recordings were helpful in establishing a diagnosis 42% of the time, but no relationship was detected between the frequency of episodes occurring before Holter recording and the likelihood of a diagnostically useful Holter. An arrhythmia was ruled out as the cause of syncope in 12% of the recordings and was implicated as the cause of syncope in 30% of recordings. Of these, 20% were ventricular tachyarrhythmias and 10% were bradyarrhythmias including pacemaker failure. Ambulatory electrocardiographic recordings led to a therapeutic change in 38% of cases. A comparison of the Holter recordings and clinic ECGs documented the expected increased sensitivity for Holter detection of arrhythmias. The average clinic ECG heart rate consistently exceeded the average Holter heart rate with a mean difference between the average heart rates recorded by the two techniques of 31 bpm (range -8-87 bpm).

Paradoxical sinus bradycardia and cardiac asystole resulted in episodic weakness, syncope, or aborted sudden cardiac death during exertion in 8 cardiomyopathic Doberman Pinschers. Bradycardias persisted for 1 to 2 minutes in 5 of 8 dogs, and were often followed by sinus tachycardia. Syncope was prolonged on multiple occasions in 5 dogs, and was accompanied by white, then cyanotic mucous membranes, mydriasis, and apparent sudden death.