Use of signal-averaged electrocardiography in the evaluation of arrhythmogenic right ventricular cardiomyopathy in Boxers

Short-term effects of Whole-Body Vibration on clinical, cardiac, and ambulatory electrocardiographic (Holter) parameters of healthy younger and older adult male non-athletic crossbreed dogs

ABSTRACT This study investigated the effects of WBV in clinical, cardiac, and ambulatory electrocardiographic (Holter) parameters of healthy young and aged male non-athletic dogs. Fourteen dogs were divided into two groups of seven animals: Group I (GI) - young dogs (12.0 and 84.0 months old); Group II (GII) - aged dogs (above 84.0 months old). Dogs were submitted to a single session of WBV (frequencies of 30 and 50 Hz), for 15-min. Variations were identified in the thickness of the interventricular septum and thickness of the left ventricle-free wall values: GI < GII at 5-min before the session. The diameter of the left atrium values showed a difference: GI < GII at 5-min before and 1-min after the session; and a decrease in GII between 5-min before and 1 min after the WBV. Several ambulatory electrocardiography (Holter) parameters demonstrated significant differences between both groups and time-points. A single session of WBV at frequencies of 30 and 50 Hz during 15-min by using a vibrating platform that delivered a vortex wave circulation did not induce significant changes in clinical, cardiac, and ambulatory electrocardiographic (Holter) parameters in healthy young and aged dogs.

Arrhythmogenic right ventricular cardiomyopathy in dogs

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is an inherited myocardial disease seen in dogs, cats, and humans. A common entity in Boxers and the related English bulldog, the disease is characterized by fatty or fibrofatty replacement of the myocardium, ventricular arrhythmias, and the potential for syncope or sudden death. In some individuals, concomitant left ventricular involvement results in systolic dysfunction and a progression to congestive heart failure. The clinical and pathological characteristics of ARVC share many similarities in dogs and humans, and Boxers serve as an important spontaneous model of the disease. Although multiple mechanisms have been implicated in the pathogenesis of ARVC, the disease is ultimately considered to be a disorder of the desmosome. Multiple causal genetic mutations have been identified in people, and over 50% of affected humans have an identifiable mutation in desmosomal proteins. To date, only a single genetic mutation has been associated with ARVC in Boxer dogs. Other as-yet-undiscovered genetic mutations and epigenetic modifiers of the disease are likely. Treatment of ARVC in dogs is focused on controlling ventricular arrhythmias and associated clinical signs. This article will review the pathophysiology, clinical diagnosis, treatment, and prognosis of ARVC in the dog.

Time-domain signal-averaged electrocardiogram in healthy German Shepherd and Boxer dogs

Signal-averaged electrocardiogram (SAECG) identifies ventricular late potentials (LP), low-amplitude electrical signals that are markers of slow cardiac conduction in fibrous myocardium, consisting in a predictive factor for sudden death in dogs at risk of sustained ventricular tachycardia. The aim of this study was to establish reference values of SAECG for German Shepherd and Boxer dogs. SAECG was performed in 19 German Shepherd and 28 Boxer client-owned dogs, and parameters analyzed were QRSd (duration of filtered QRS), LAS<40μV (duration of low-amplitude signals in terminal portion of filtered QRS) and RMS40 (root square of mean voltage over the last 40 milliseconds of filtered QRS), with two different filters (25-250 Hz and 40-250 Hz). Statistical analyses was achieved by T Student test (p<0.05) to identify differences between the two groups and between the values obtained with the two filters. No statistical difference was found in SAECG variables between the two breeds with the two different filters (p>0.05). Achieving normal values of SAECG in German Shepherd and Boxer dogs is important to further research late potentials in animals of these breeds with hereditary ventricular tachycardia or arrhythmogenic cardiomyopathy and identification of individuals at high risk of cardiac-related sudden death.

Arrhythmogenic right ventricular cardiomyopathy

Arrhythmogenic right ventricular cardiomyopathy (ARVC) originally emerged as a pathologic diagnosis based on distinctive autopsy findings in cases of premature sudden death. Subsequently these characteristic pathologic features were associated with ventricular tachycardia of right ventricular origin and syncope. ARVC is a rare condition and our understanding of the disorder has been confounded by multiple small, highly selected series. Driven by both family studies and improved non-invasive imaging tools the clinical diagnosis of ARVC has broadened, in some instances extending far beyond the original limits of the syndrome. In recent years false-positive diagnoses have increased, thus stimulating investigators to move toward more rigorous clinical criteria. Despite the efforts of a Task Force to establish a baseline for subsequent empiric testing, these criteria have often inadvertently been used as a definitive diagnostic tool in the absence of prospective data. Recent genetic studies have revealed substantial etiologic heterogeneity, and ARVC is emerging as a syndrome consisting of multiple discrete disease entities, in part explaining the tremendous variation in clinical features and natural history seen in prior reports.

Differential expression of the cardiac ryanodine receptor in normal and arrhythmogenic right ventricular cardiomyopathy canine hearts

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a form of cardiomyopathy characterized by ventricular tachyarrhythmias and a fibrofatty infiltrate that is believed to preferentially affect the right ventricle. Mutations in the cardiac ryanodine receptor (RyR2) gene have been identified in some human families with a unique form of ARVC, ARVC2. Although the RyR2 has significant importance in excitation-contraction coupling across the ventricles, mutations in the gene encoding for it appear to have the greatest impact on the right ventricle in ARVC2. Using a canine model (boxer), the RyR2 protein and message RNA in the right ventricle, left ventricle and interventricular septum from normal dogs and dogs with ARVC were investigated by immunoblotting and real time PCR. The cardiac RyR2 message and protein expression were differentially expressed across the cardiac walls in the normal heart, with the lowest concentration expressed in the right ventricle (P < 0.05). The message and protein expression of the RyR2 were reduced in all chambers in the canine model of ARVC. We propose that the increased susceptibility of the right ventricle to ARVC may be associated with the lower baseline protein concentration of RyR2 in the normal right ventricle compared to the left ventricle and interventricular septum and that all three areas are equally affected in this canine model of ARVC. Using this naturally occurring model of canine ARVC, we may have provided new insights into the pathogenesis of this cardiomyopathy.