A missense variant in the titin gene in Doberman pinscher dogs with familial dilated cardiomyopathy and sudden cardiac death.

The dog provides a large animal model of familial dilated cardiomyopathy for the study of important aspects of this common familial cardiovascular disease. We have previously demonstrated a form of canine dilated cardiomyopathy in the Doberman pinscher breed that is inherited as an autosomal dominant trait and is associated with a splice site variant in the pyruvate dehydrogenase kinase 4 (PDK4) gene, however, genetic heterogeneity exists in this species as well and not all affected dogs have the PDK4 variant. Whole genome sequencing of a family of Doberman pinchers with dilated cardiomyopathy and sudden cardiac death without the PDK4 variant was performed. A pathologic missense variant in the titin gene located in an immunoglobulin-like domain in the I-band spanning region of the molecule was identified and was highly associated with the disease (p < 0.0001). We demonstrate here the identification of a variant in the titin gene highly associated with the disease in this spontaneous canine model of dilated cardiomyopathy. This large animal model of familial dilated cardiomyopathy shares many similarities with the human disease including mode of inheritance, clinical presentation, genetic heterogeneity and a pathologic variant in the titin gene. The dog is an excellent model to improve our understanding of the genotypic phenotypic relationships, penetrance, expression and the pathophysiology of variants in the titin gene.

Sequence and expression analysis of cardiac ryanodine receptor 2 in broilers that died from sudden death syndrome.

Sudden death syndrome (SDS) is a stress-related disease in broilers with no diagnostic clinical or necropsy findings. SDS is associated with ventricular tachycardia (VT) and ventricular fibrillation (VF); however, its pathogenesis is not precisely described at the molecular level. Dysfunction of ryanodine receptor 2 (RYR2), that controls rapid release of Ca2+ from the sarcoplasmic reticulum (SR) into the cytosol during muscle contraction, has been associated with VT and sudden cardiac death (SCD) in human patients with structurally normal heart, but there is no report describing abnormalities in RYR2 in diseased broilers. In order to advance our knowledge on the molecular mechanisms predisposing broilers to fatal arrhythmia, the present study was conducted to determine the occurrence of possible mutations and changes in the expression level of the chicken RYR2 gene (chRYR2) in broilers that died from SDS. An increase in mRNA expression level and nine novel point mutations in chRYR2 were found in relation to SDS. In conclusion, susceptibility to lethal cardiac arrhythmia in SDS may be associated with specific changes in intracellular Ca2+ cycling components such as RYR2 due to mutation and dysregulation. Finding the probable association of SDS with gene defects can be applied to select for chickens with lower susceptibility to SDS and decrease the poultry industry losses due to SDS mortality. RESEARCH HIGHLIGHTS Investigation of the occurrence of possible mutations and changes in the expression level of chicken RYR2 gene (chRYR2) in broilers that died from SDS. Increase in the mRNA expression level of chRYR2 in relation to SDS. Nine novel point mutations in chRYR2 of broilers that died from SDS. Possible connection between susceptibility to lethal cardiac arrhythmia in SDS and changes in intracellular Ca2+ cycling machinery, such as RYR2, due to mutation and dysregulation.

Cardiac Pathology and Genomics of Sudden Death in Racehorses From New York and Maryland Racetracks.

Postmortem evaluation of racehorses has focused primarily on musculoskeletal injuries; however, horses also die suddenly on the track (sudden death [SD]). Although cardiac conditions are frequently suspected as a cause of death, SD racehorses are often autopsy negative; however, previous studies have been limited due to inconsistent or insufficient cardiac sampling and lack of controls. SD in New York (NY) and Maryland (MD) racehorses was evaluated in an observational case vs control study comparing clinical information, postmortem evaluation including cardiac dissection, and cardiac conduction system histopathology. In the study period, there were 40 cases of SD. In NY, SD occurred in 12% (37/316) of submissions, and 36 (11%) cases of SD were exercise associated (EASD); 3 EASD cases occurred in MD. In NY/MD EASD cases with histologic examination of the heart, 11 of 36 (31%) had significant lesions, including mesenteric artery rupture (1), axial trauma (2), systemic inflammation (2), pulmonary hemorrhage (1), and cardiac disease (5). Mild myocardial fibrosis, mild inflammation, coronary arteriosclerosis, and variation in cardiac nodal connective tissue were present in both SD cases and controls and thus were not considered to be causes of SD. While not excluding a genetic basis for SD, analysis of the genotypes (GGP Equine 70 K Array) of cases and controls did not reveal significant differences in allele frequencies at any locus. Most SD racehorses were autopsy negative; further research using standardized protocols and controls is needed to understand the underlying causes of SD, which is crucial to protecting the viability of racing.

Histopathological studies of the heart in three lines of broiler chickens.

The aim of this study was to analyse the morphological lesion pattern of the heart of broiler chickens (Cobb 500, Hubbard F15 and Ross 308) during fattening with no clinical signs of disease and to determine the most susceptible period for the occurrence of morphological lesions. The most frequently diagnosed lesions in each genetic line were degeneration of the fibres with vacuolation, congestion of cardiac muscle, oedema and vacuolisation of the Purkinje cells. The highest numbers of morphological lesions were observed on d 38, 31 and 10 of life. The lesions were most numerous in the septum, followed by the left and right ventricles. Ischaemic cardiomyocytes were also most numerous on d 38 of life and in the left ventricle. Overload of cardiac muscle, prolonged hypoxia and increasing body weight on d 38 are the likely reasons for the largest number of lesions and ischaemic fibres, which may lead to heart failure.

Polymorphism identification and cardiac gene expression analysis of the calsequestrin 2 gene in broiler chickens with sudden death syndrome.

Sudden death syndrome (SDS) in broilers is a cardiac disease associated with ventricular tachycardia (VT) and ventricular fibrillation (VF); however, its pathogenesis at the molecular level is not precisely determined. Downregulation and mutations of calsequestrin 2 (CASQ2), a major intracellular Ca(2+) buffer, have been associated with VT and sudden cardiac death (SCD) in humans but in chickens there is no report describing CASQ2 abnormalities in cardiac diseases. In order to better understand the molecular mechanisms predisposing the myocardium to fatal arrhythmia in broilers, the mRNA expression level of chicken CASQ2 gene (chCASQ2) in the left ventricle of dead broilers with SDS was determined and compared to healthy broilers using quantitative real-time PCR (qPCR). To determine the probable mutations in chCASQ2, PCR and direct sequencing were also done. Results showed a reduction in chCASQ2 expression in broilers dead by SDS. Three novel mutations (K289R, P308S, D310H) which are absent in healthy broilers were observed in chCASQ2. It is concluded that susceptibility to fatal cardiac arrhythmia in SDS may be associated with changes in intracellular Ca(2+) balance due to mutation and downregulation of chCASQ2.

Fatal arrhythmogenic right ventricular cardiomyopathy in 2 related subadult chimpanzees (Pan troglodytes).

Cardiovascular disease is increasingly recognized as an important cause of morbidity and mortality in captive chimpanzees (Pan troglodytes). This report records 2 cases of sudden cardiac death in closely related subadult captive chimpanzees with marked replacement fibrosis and adipocyte infiltration of the myocardium, which resemble specific atypical forms of the familial human disease arrhythmogenic right ventricular cardiomyopathy. Changes were consistent with left-dominant and biventricular subtypes, which are both phenotypic variants found within human families with familial arrhythmogenic right ventricular cardiomyopathy. Previously reported fibrosing cardiomyopathies in chimpanzees were characterized by nonspecific interstitial fibrosis, in contrast to the replacement fibrofatty infiltration with predilection for the outer myocardium seen in these 2 cases. To the authors' knowledge, this case report is the first to describe cardiomyopathy resembling arrhythmogenic right ventricular cardiomyopathy in nonhuman primates and the first to describe left-dominant arrhythmogenic cardiomyopathy-type lesions in an animal.

An ABCC9 Missense Variant Is Associated with Sudden Cardiac Death and Dilated Cardiomyopathy in Juvenile Dogs.

Sudden cardiac death in the young (SCDY) is a devastating event that often has an underlying genetic basis. Manchester Terrier dogs offer a naturally occurring model of SCDY, with sudden death of puppies as the manifestation of an inherited dilated cardiomyopathy (DCM). We performed a genome-wide association study for SCDY/DCM in Manchester Terrier dogs and identified a susceptibility locus harboring the cardiac ATP-sensitive potassium channel gene ABCC9. Sanger sequencing revealed an ABCC9 p.R1186Q variant present in a homozygous state in all SCDY/DCM-affected dogs (n = 26). None of the controls genotyped (n = 398) were homozygous for the variant, but 69 were heterozygous carriers, consistent with autosomal recessive inheritance with complete penetrance (p = 4 × 10-42 for the association of homozygosity for ABCC9 p.R1186Q with SCDY/DCM). This variant exists at low frequency in human populations (rs776973456) with clinical significance previously deemed uncertain. The results of this study further the evidence that ABCC9 is a susceptibility gene for SCDY/DCM and highlight the potential application of dog models to predict the clinical significance of human variants.

Long-term outcome and troponin I concentrations in Great Danes screened for dilated cardiomyopathy: an observational retrospective epidemiological study.

INTRODUCTION: Dilated cardiomyopathy (DCM) is common in Great Danes (GDs) but screening for this condition can be challenging. We hypothesised that cardiac troponin-I (cTnI) concentration is elevated in GDs with DCM and/or ventricular arrhythmias (VAs), and is associated with reduced survival time in GDs. ANIMALS: One hundred and twenty-four client-owned GDs assigned echocardiographically as normal (n = 53), equivocal (n = 37), preclinical DCM (n = 21), or clinical DCM (n = 13). MATERIALS AND METHODS: A retrospective epidemiological study. Echocardiographic diagnosis, VAs, and contemporaneous cTnI concentrations were recorded. Diagnostic accuracy and cTnI cut-offs were determined with receiver operating characteristic analyses. Effects of the cTnI concentration and disease status on survival and cause of death were explored. RESULTS: Median cTnI was greater in clinical DCM (0.6 ng/mL [25th-75th percentiles: 0.41-1.71 ng/mL]) and GDs with VAs (0.5 ng/mL [0.27-0.80 ng/mL], P<0.001). Elevated cTnI detected these dogs with good accuracy (area under the curve: 0.78-0.85; cut-offs 0.199-0.34 ng/mL). Thirty-eight GDs (30.6%) suffered a cardiac death (CD); GDs suffering CD (0.25 ng/mL [0.21-0.53 ng/mL]) and specifically sudden cardiac death (SCD) (0.51 ng/mL [0.23-0.72 ng/mL]) had higher cTnI than GDs dying of other causes (0.20 ng/mL [0.14-0.35 ng/mL]; P<0.001). Elevated cTnI (>0.199 ng/mL) was associated with shorter long-term survival (1.25 years) and increased risk of SCD. Great Danes with VAs had shorter survival times (0.97 years). CONCLUSIONS: A cardiac troponin-I concentration is a useful adjunctive screening tool. Elevated cTnI is a negative prognostic indicator.

Sudden death in a dog after doxorubicin chemotherapy.

A case is reported of fatal cardiomyopathy in an 8-year-old female German Shepherd after standard chemotherapy with doxorubicin for splenic hemangiosarcoma. The main gross lesion was a moderate bilateral cardiac ventricular dilation with diffusely pale myocardium. Histological analysis revealed severe multifocal vacuolar degeneration of cardiomyocytes, myocytolysis, myofibril loss, myocardial fibrosis, and edema. Myocardial fiber vacuolization and myocytolysis were highly suggestive of doxorubicin cardiotoxicity.

Survival and echocardiographic data in dogs with congestive heart failure caused by mitral valve disease and treated by multiple drugs: a retrospective study of 21 cases.

This retrospective study reports the survival time [onset of congestive heart failure (CHF) to death from any cause] of 21 dogs with mitral regurgitation (MR) and CHF treated with a combination of furosemide, angiotensin-converting enzyme inhibitor (ACEI, benazepril, or enalapril), pimobendan, spironolactone, and amlodipine. Baseline echocardiographic data: end-systolic and end-diastolic volume indices (ESVI and EDVI), left atrium to aorta ratio (LA/Ao), and regurgitant fraction (RF) are reported. Median survival time (MST) was 430 d. Initial dosage of furosemide (P = 0.0081) and LA/Ao (P = 0.042) were negatively associated with survival. Baseline echocardiographic indices (mean ± standard deviation) were 40.24 ± 16.76 for ESVI, 161.48 ± 44.49 mL/m(2) for EDVI, 2.11 ± 0.75 for LA/Ao, and 64.71 ± 16.85% for RF. Combining furosemide, ACEI, pimobendan, spironolactone, and amlodipine may result in long survival times in dogs with MR and CHF. Severity of MR at onset of CHF is at least moderate.

Heart rhythm characterization during sudden cardiac death in dogs.

INTRODUCTION/OBJECTIVES: Inherited or acquired arrhythmic disorders and cardiac disease have been associated with sudden cardiac death (SCD) in dogs. The electrical mechanism related to death in most of these cases is unknown. This retrospective study aimed to describe arrhythmic events in dogs that experienced SCD during Holter monitoring. ANIMALS, MATERIALS AND METHODS: Nineteen client-owned dogs that experienced SCD during Holter examination were included. Clinical records from a Holter service database were reviewed, and both the rhythm preceding death and the dominant rhythm causing SCD were analysed. Clinical data, Holter diaries and echocardiographic diagnosis were also evaluated. RESULTS: Structural heart disease was identified in 12/19 dogs (dilated cardiomyopathy in five dogs, arrhythmogenic right ventricular cardiomyopathy in four dogs, myxomatous mitral valve disease in two dogs, and suspected myocarditis in one dog), five of which had concurrent congestive heart failure. Sudden cardiac death was related to ventricular premature complexes or monomorphic ventricular tachycardia degenerating into ventricular fibrillation in 42% of dogs, polymorphic ventricular tachycardia, or torsade de pointes-like inducing ventricular fibrillation in 21%, and asystole or presumptive agonal pulseless electrical activity triggered by malignant bradyarrhythmias in 37%. CONCLUSIONS: The most common rhythm associated with SCD in our population of dogs was ventricular tachycardia leading to ventricular fibrillation, although bradyarrhythmia-related SCD, possibly related to inappropriate vagal reflexes, was also a notable cause.

Exercise-Associated Sudden Death in Finnish Standardbred and Coldblooded Trotters - A Case Series With Pedigree Analysis.

Exercise-associated sudden deaths (EASDs) are deaths occurring unexpectedly during or immediately after exercise. Sudden cardiac death (SCD) is one cause of EASD. Cardiac arrhythmias caused by genetic variants have been linked to SCD in humans. We hypothesize that genetic variants may be associated with SCD in animals, including horses. Genetic variants are transmitted to offspring and their frequency might increase within a family. Therefore, the frequency of such variants might increase with the inbreeding factor. Higher inbreeding could have a negative impact on racing performance. Pedigree data and career earnings from racehorses diagnosed with SCD between 2002 and 2017 were compared using non-parametric tests with 1) control horses that died due to catastrophic musculoskeletal injuries and 2) horses that raced during the same period without reported problems. Diagnosis of SCD was based on necropsy reports, including macroscopic and microscopic examinations. Death was registered in the study period for 61 horses. Eleven of these horses were excluded due to missing autopsy reports. In 25 cases, the diagnosis remained unknown and death was possibly caused by cardiac arrhythmia, in two cases cardiac disease was identified, in seven cases a rupture of a major vessel had occurred. In addition, 16 horses died or were euthanized due to severe musculoskeletal injuries. No significant differences in inbreeding coefficients or in career earnings were found between the groups or between horses with EASD compared with other horses racing during the same period. The study provides no evidence for increased inbreeding factor in Finnish racehorses with SCD.

Prevalence of sudden cardiac death in dogs with atrial fibrillation.

BACKGROUND: Atrial fibrillation (AF) is associated with increased risk of sudden cardiac death (SCD) in humans, independent of secondary risk factors such as thrombogenic disorders. In dogs, SCD is described in a number of heart diseases, but an association between AF and SCD is unreported. HYPOTHESIS: (a) A higher proportion of dogs with AF will experience SCD, and (b) SCD will be associated with complex ventricular arrhythmias. ANIMALS: One-hundred forty-two dogs with AF, and 127 dogs without AF. METHODS: Retrospective, multicenter, case-control study. Dogs included in the AF group were compared to a control group of dogs in sinus rhythm, matched for echocardiographic diagnosis. Descriptive statistics were used to identify proportions of each group suffering SCD, compared using chi-squared testing. Risk factors for SCD in dogs with AF were evaluated at the univariable and multivariable level using binary logistic regression. Significance was P < .05. RESULTS: A significantly higher proportion of dogs with AF suffered SCD than dogs in the control group (14.8% vs 5.5%; P = .01). Younger age at diagnosis, larger left atrial size, and a history of syncope all were independent predictors of SCD in dogs with AF (χ2 , 16.3; P = .04). CONCLUSIONS AND CLINICAL IMPORTANCE: Atrial fibrillation was associated with a higher prevalence of SCD in dogs. A history of syncope may be a useful predictor of SCD risk.

Sudden cardiac death: A comparative review of humans, dogs and cats.

Sudden death is one of the most common causes of death in humans in Western countries. Approximately 85% of these cases are of cardiac origin. In dogs and cats, sudden cardiac death (SCD) also commonly occurs, but fewer pathophysiological and prevalence data are available. Both structural, primarily 'electrical' and ischemic heart diseases are known to cause SCD, many of which share similar underlying arrhythmogenic mechanisms between humans and companion animals. As for underlying genetics, numerous mutations on multiple loci have been related to SCD in humans, but only a few mutations associated with dilated cardiomyopathy and SCD have been identified in dogs, e.g. in the phospholamban and titin genes. Information published from human medicine can therefore inform future veterinary studies, but also dogs and cats could act as spontaneous models of SCD in humans. Further research in both fields is therefore warranted to better understand the pathophysiology, genetics, and prevention of SCD.

Sudden death in a dog with aortic coarctation.

A previously healthy, one-year-old, intact female Vizsla dog collapsed and experienced cardiopulmonary arrest after a stressful event. Postmortem examination identified juxtaductal aortic coarctation (AoCo) with complex morphology. Located in the isthmus aorta adjacent to the ligamentum arteriosum, the AoCo comprised a shelf-like structure caused by invagination of the aortic wall into the lumen. Just distally, a second region of aortic occlusion resulted from an obstructing aortic membrane that restricted blood flow into the descending aorta through a small, eccentric ostium. Plausibly, the AoCo contributed to high afterload which led to reduction of coronary blood flow, myocardial hypoxia, and sudden death during physical stress. Although AoCo is a well-recognized congenital defect in humans, it has been reported only rarely in animals. The present case details the gross and histologic features of a complex, juxtaductal AoCo in a dog who died suddenly after stress. These morphologic findings may be informative when contemplating diagnosis of this anomaly.

Adipositas Cordis in Two Cats with Sudden Death.

Adipositas cordis (AC) is a rare cardiomyopathy characterized by fatty infiltration of the myocardium without signs of tissue destruction or inflammation. Its diagnosis is challenging and requires histopathological examination. This study describes such cardiomyopathy in two cats that died suddenly. In both cases, anatomopathological examination showed gross lesions indicative of acute heart failure, associated with an increase in subepicardial fat, particularly in the right ventricle. Microscopically, there was an increased amount of subepicardial and intramyocardial adipose tissue in the right ventricular free wall, without signs of cellular degeneration, inflammatory infiltration, necrosis or fibrosis, confirmed by histochemical staining. AC is a rare cardiac pathology, but it should be taken into consideration in feline medicine when a sudden death occurs.

Ventricular arrhythmia and sudden cardiac death in young Leonbergers.

INTRODUCTION: To describe unexpected sudden cardiac death (SCD) in young Leonbergers (<3 years) and to review the circumstances before death and necropsy findings; to prospectively evaluate the presence of possible arrhythmias in young Leonbergers; and to examine pedigrees for determining potential modes of inheritance. ANIMALS: Postmortem evaluations included 21 Leonbergers. Clinical evaluation consisted of 46 apparently healthy Leonbergers with and without a close family history of SCD. MATERIALS AND METHODS: Necropsy reports were reviewed retrospectively. Prospective clinical evaluation included physical examination, 5-min electrocardiogram, 24-h Holter, echocardiography, and laboratory tests. Pedigree data were examined for mode of inheritance. RESULTS: Based on necropsy reports, SCD occurred at a median age of 12 months (range, 2.0-32.0 months) without any previous clinical signs and usually in rest. No evidence of structural cardiac disease was found; arrhythmia-related death was suspected. Clinical evaluation and 24-h Holter showed ventricular arrhythmia (VA) in 14 apparently healthy Leonbergers (median age, 18 months; range, 12-42 months). Severity of VA varied from infrequent couplets/triplets to frequent complexity (couplets, triplets, nonsustained ventricular tachycardias,VTs) characterized by polymorphology. During follow-up, two dogs with polymorphic VT died. Although breed specificity and high prevalence indicate a heritable disease, based on available pedigree data, the mode of inheritance could not be determined. CONCLUSIONS: Sudden cardiac death in young Leonbergers is associated with malignant VA characterized by complexity and polymorphic nature. Diagnosis is based on 24-h Holter monitoring. Pedigree analysis suggests that the arrhythmia is familial.

Hypertrophic cardiomyopathy in two captive Bennett's wallabies (Macropus rufogriseus rufogriseus).

Hypertrophic cardiomyopathy (HCM) was diagnosed during postmortem examination of 2 captive adult Bennett's wallabies (Macropus rufogriseus rufogriseus). The wallabies were members of a mob (herd) of 3 wallabies, and 2 died spontaneously without clinical signs of heart failure being detected. Gross lesions in both cases included marked concentric hypertrophy of the left ventricle, pulmonary edema, and multifocal hemorrhage and subcutaneous edema of the hind limbs. Histologic lesions of the heart were limited to mild cardiac myofiber disarray and marked cardiac myofiber hypertrophy. A specific etiology for the HCM was not determined in either animal. The cardiac changes are similar to the left ventricular hypertrophy previously described in kangaroos.

Adverse outcome of using tilmicosin in a lamb with multiple ventricular septal defects.

A 15-day-old, 6.08 kg, lamb was injected subcutaneously with tilmicosin 15 mg/kg body weight. Approximately 15 min later, the lamb died. During necropsy, the heart was found to have multiple ventricular septal defects. Death was attributed to sudden heart failure due to the cardiac effects of tilmicosin in a heart having congenital defects.