Prevalence of dilated cardiomyopathy in Doberman Pinschers in various age groups

Metabolome Profiling in the Plasma of Dogs with Idiopathic Dilated Cardiomyopathy: A Multiplatform Mass-Spectrometry-Based Approach

Dilated cardiomyopathy is one of the important diseases in dogs and humans. The second most common cause of heart failure in dogs is idiopathic dilated cardiomyopathy (iDCM), which results in heart failure or sudden cardiac death due to arrhythmia. This study aimed to determine changes in the plasma metabolome of dogs with iDCM compared to healthy dogs. For that purpose, a multiplatform mass-spectrometry-based approach was used. In this study, we included two groups of dogs: 12 dogs with iDCM and 8 healthy dogs. A total of 272 metabolites were detected in the plasma samples of dogs by combining three approaches but four MS-based platforms (GC-MS, LC-MS (untargeted), LC-MS (targeted), and FIA-MS (targeted) methods). Our findings demonstrated changes in the canine plasma metabolome involved in the development of iDCM, including the different concentrations of amino acids, biogenic amines, acylcarnitines, triglycerides and diglycerides, sphingomyelins, and organic acids. The results of this study will enable the detection and monitoring of pathophysiological mechanisms involved in the development of iDCM in the future.

Identification of novel genetic risk factors of dilated cardiomyopathy: from canine to human

BACKGROUND

Dilated cardiomyopathy (DCM) is a life-threatening heart disease and a common cause of heart failure due to systolic dysfunction and subsequent left or biventricular dilatation. A significant number of cases have a genetic etiology; however, as a complex disease, the exact genetic risk factors are largely unknown, and many patients remain without a molecular diagnosis.

METHODS

We performed GWAS followed by whole-genome, transcriptome, and immunohistochemical analyses in a spontaneously occurring canine model of DCM. Canine gene discovery was followed up in three human DCM cohorts.

RESULTS

Our results revealed two independent additive loci associated with the typical DCM phenotype comprising left ventricular systolic dysfunction and dilatation. We highlight two novel candidate genes, RNF207 and PRKAA2, known for their involvement in cardiac action potentials, energy homeostasis, and morphology. We further illustrate the distinct genetic etiologies underlying the typical DCM phenotype and ventricular premature contractions. Finally, we followed up on the canine discoveries in human DCM patients and discovered candidate variants in our two novel genes.

CONCLUSIONS

Collectively, our study yields insight into the molecular pathophysiology of DCM and provides a large animal model for preclinical studies.

Predominant myosin superrelaxed state in canine myocardium with naturally occurring dilated cardiomyopathy

Dilated cardiomyopathy (DCM) is a naturally occurring heart failure condition in humans and dogs, notably characterized by a reduced contractility and ejection fraction. As the identification of its underlying cellular and molecular mechanisms remain incomplete, the aim of the present study was to assess whether the molecular motor myosin and its known relaxed conformational states are altered in DCM. For that, we dissected and skinned thin cardiac strips from left ventricle obtained from six DCM Doberman Pinschers and six nonfailing (NF) controls. We then used a combination of Mant-ATP chase experiments and X-ray diffraction to assess both energetic and structural changes of myosin. Using the Mant-ATP chase protocol, we observed that in DCM dogs, the amount of myosin molecules in the ATP-conserving conformational state, also known as superrelaxed (SRX), is significantly increased when compared with NF dogs. This alteration can be rescued by applying EMD-57033, a small molecule activating myosin. Conversely, with X-ray diffraction, we found that in DCM dogs, there is a higher proportion of myosin heads in the vicinity of actin when compared with NF dogs (1,0 to 1,1 intensity ratio). Hence, we observed an uncoupling between energetic (Mant-ATP chase) and structural (X-ray diffraction) data. Taken together, these results may indicate that in the heart of Doberman Pinschers with DCM, myosin molecules are potentially stuck in a nonsequestered but ATP-conserving SRX state, that can be counterbalanced by EMD-57033 demonstrating the potential for a myosin-centered pharmacological treatment of DCM.NEW & NOTEWORTHY The key finding of the present study is that, in left ventricles of dogs with a naturally occurring dilated cardiomyopathy, relaxed myosin molecules favor a nonsequestered superrelaxed state potentially impairing sarcomeric contractility. This alteration is rescuable by applying a small molecule activating myosin known as EMD-57033.

Sedative effects and changes in cardiac rhythm with intravenous premedication of medetomidine, butorphanol and ketamine in dogs

OBJECTIVE

To determine the sedative effects and characteristics of cardiac rhythm with intravenous (IV) premedication of medetomidine, butorphanol and ketamine in dogs.

STUDY DESIGN

Prospective, blinded, randomized clinical trial.

ANIMALS

A total of 116 client-owned healthy dogs undergoing elective surgery.

METHODS

Dogs were randomly allocated one of four groups: group M, medetomidine 5 μg kg^-1; group B, butorphanol 0.2 mg kg^-1; group MB, medetomidine 5 μg kg^-1 and butorphanol 0.2 mg kg^-1; or group MBK, medetomidine 5 μg kg^-1, butorphanol 0.2 mg kg^-1 and ketamine 1 mg kg^-1 IV. Sedation was assessed using a numerical descriptive scale. Heart rate (HR) and rhythm were monitored; propofol dose (mg kg^-1 IV) to allow orotracheal intubation was documented. Data were analysed using anova, accounting for multiple testing with the Tukey honest significant difference test.

RESULTS

Sedation scores varied significantly between all groups at all time points, except between groups MB and MBK at four time points. HR decreased in all groups: most in groups M and MB, least in group B. HR was initially higher in group MBK than in groups M and MB. Arrhythmias occurred in all groups: group B showed second-degree atrioventricular blocks occasionally, all other groups showed additionally ventricular escape complexes and bundle branch blocks. Dose of propofol required for orotracheal intubation was significantly higher in group B (5.0 ± 2.0 mg kg^-1) than in group M (2.6 ± 0.6 mg kg^-1). Although no difference could be demonstrated between groups MB (1.4 ± 0.6 mg kg^-1) and MBK (0.9 ± 0.8 mg kg^-1), both groups required significantly less propofol than group M.

CONCLUSION AND CLINICAL RELEVANCE

Medetomidine-based premedication protocols led to various bradyarrhythmias. Addition of subanaesthetic doses of ketamine to medetomidine-based protocols resulted in higher HRs, fewer bradyarrhythmias and fewer animals that required propofol for intubation without causing side effects in healthy dogs.

Prevalence of Echocardiographic Evidence of Trace Mitral and Aortic Valve Regurgitation in 50 Clinically Healthy, Young Adult Labrador Retrievers without Heart Murmur

Simple Summary

Screening for various disorders lowers the chance for spreading hereditary diseases by selecting individuals for breeding that do not have that specific disorder. Screening examinations, which are typically performed in clinically healthy animals, can pick up diseases in an early stage, when clinical signs are absent. On the other hand, screenings might also reveal anomalies of questionable relevance. In the present study, healthy young Labrador retrievers were screened with cardiac ultrasound for congenital heart defects. In half of the dogs, a small leakage of a cardiac valve was found, which finding is often a sign of a heart disease. However, in this breed and age group, this leaky valve is most likely innocent and represents a variation of normal.

Abstract

Background—Though physiologic regurgitation of the right-sided cardiac valves is well recognized in dogs and other mammals, the prevalence of trace insufficiency of the mitral and aortic valves in clinically healthy, young adult dogs is unknown. Methods—In this observational cross-sectional study, 50 clinically healthy, young adult Labrador retrievers without an audible heart murmur were enrolled. All dogs were bred and owned by a single organization. Cardiac screening was requested for all dogs that were intended for breeding. These dogs underwent a cardiac auscultation and transthoracic echocardiography by a veterinary cardiology specialist. If mitral or aortic valve regurgitation was noticed, the jet size was subjectively assessed on color Doppler echocardiography. Pedigree analysis was performed to reveal a possible hereditary background of mitral valve regurgitation. Results—The prevalence of trivial mitral valve regurgitation was 52% with no significant predisposition to gender (p = 0.86) or haircoat color (p = 0.68). The prevalence of aortic valve regurgitation was 4%. Pedigree analysis for mitral valve regurgitation showed familial clustering, suggesting a hereditary background of the trait. Conclusions—The prevalence of silent trace mitral valve regurgitation in young adult Labrador retrievers was high. Because the regurgitant jet was trivial in all dogs, it is probably physiologic.

Genetic Basis of Dilated Cardiomyopathy in Dogs and Its Potential as a Bidirectional Model

Simple Summary

Heart disease is a leading cause of death for both humans and dogs. Inherited heart diseases, including dilated cardiomyopathy (DCM), account for a proportion of these cases. Human and canine patients with DCM suffer from an enlarged heart that can no longer pump efficiently, resulting in heart failure. This causes symptoms or clinical signs like difficulty breathing, irregular heartbeat, and eventually death. The symptoms or clinical signs of this disease vary in age of onset at the beginning of symptoms, sex predisposition, and overall disease progression. Despite the many similarities in DCM in both species, only a few candidate genes so far have been linked to this disease in dogs versus tens of genes identified in human DCM. Additionally, the use of induced pluripotent stem cells, or engineered stem cells, has been widely used in the study of human genetic heart disease but has not yet been fully adapted to study heart disease in dogs. This review describes the current knowledge on the genetics and subtypes of naturally occurring DCM in dogs, and how advances in research might benefit the dog but also the human patient. Additionally, a novel method using canine engineered stem cells to uncover unknown contributions of mistakes in DNA to the progression of DCM will be introduced along with its applications for human DCM disease modeling and treatment.

Abstract

Cardiac disease is a leading cause of death for both humans and dogs. Genetic cardiomyopathies, including dilated cardiomyopathy (DCM), account for a proportion of these cases in both species. Patients may suffer from ventricular enlargement and systolic dysfunction resulting in congestive heart failure and ventricular arrhythmias with high risk for sudden cardiac death. Although canine DCM has similar disease progression and subtypes as in humans, only a few candidate genes have been found to be associated with DCM while the genetic background of human DCM has been more thoroughly studied. Additionally, experimental disease models using induced pluripotent stem cells have been widely adopted in the study of human genetic cardiomyopathy but have not yet been fully adapted for the in-depth study of canine genetic cardiomyopathies. The clinical presentation of DCM is extremely heterogeneous for both species with differences occurring based on sex predisposition, age of onset, and the rate of disease progression. Both genetic predisposition and environmental factors play a role in disease development which are identical in dogs and humans in contrast to other experimental animals. Interestingly, different dog breeds have been shown to develop distinct DCM phenotypes, and this presents a unique opportunity for modeling as there are multiple breed-specific models for DCM with less genetic variance than human DCM. A better understanding of DCM in dogs has the potential for improved selection for breeding and could lead to better overall care and treatment for human and canine DCM patients. At the same time, progress in research made for human DCM can have a positive impact on the care given to dogs affected by DCM. Therefore, this review will analyze the feasibility of canines as a naturally occurring bidirectional disease model for DCM in both species. The histopathology of the myocardium in canine DCM will be evaluated in three different breeds compared to control tissue, and the known genetics that contributes to both canine and human DCM will be summarized. Lastly, the prospect of canine iPSCs as a novel method to uncover the contributions of genetic variants to the pathogenesis of canine DCM will be introduced along with the applications for disease modeling and treatment.

Animal Models to Study Cardiac Arrhythmias

Cardiac arrhythmias are a significant cause of morbidity and mortality worldwide, accounting for 10% to 15% of all deaths. Although most arrhythmias are due to acquired heart disease, inherited channelopathies and cardiomyopathies disproportionately affect children and young adults. Arrhythmogenesis is complex, involving anatomic structure, ion channels and regulatory proteins, and the interplay between cells in the conduction system, cardiomyocytes, fibroblasts, and the immune system. Animal models of arrhythmia are powerful tools for studying not only molecular and cellular mechanism of arrhythmogenesis but also more complex mechanisms at the whole heart level, and for testing therapeutic interventions. This review summarizes basic and clinical arrhythmia mechanisms followed by an in-depth review of published animal models of genetic and acquired arrhythmia disorders.

Association between dilated cardiomyopathy and hypothyroidism in dogs

It is a known fact that thyroid hormones have an influence on the heart function. Opinions on hypothyroidism and its effect on dilated cardiomyopathy (DCM) development are controversial and often contradictory. This prospective study examined the potential association between hypothyroidism and DCM in dogs. A total of 35 dogs with DCM were included in the study. Preclinical DCM was diagnosed in 18 patients, and clinical DCM was diagnosed in 17 patients, four of which were also diagnosed with hypothyroidism. There was a positive correlation between the thyroid-stimulating hormone and body weight, left atrium size and the serum NT-proBNP concentration in patients with preclinical DCM. Euthyroid dogs with DCM had higher total thyroxine values and more ventricular premature complexes than hypothyroid dogs. Although our study did not confirm a direct relationship between hypothyroidism and DCM as a possible cause, other correlations were detected that had not yet been described in veterinary medicine.

Bacterial Cellulose and ECM Hydrogels: An Innovative Approach for Cardiovascular Regenerative Medicine

Cardiovascular diseases are considered the leading cause of death in the world, accounting for approximately 85% of sudden death cases. In dogs and cats, sudden cardiac death occurs commonly, despite the scarcity of available pathophysiological and prevalence data. Conventional treatments are not able to treat injured myocardium. Despite advances in cardiac therapy in recent decades, transplantation remains the gold standard treatment for most heart diseases in humans. In veterinary medicine, therapy seeks to control clinical signs, delay the evolution of the disease and provide a better quality of life, although transplantation is the ideal treatment. Both human and veterinary medicine face major challenges regarding the transplantation process, although each area presents different realities. In this context, it is necessary to search for alternative methods that overcome the recovery deficiency of injured myocardial tissue. Application of biomaterials is one of the most innovative treatments for heart regeneration, involving the use of hydrogels from decellularized extracellular matrix, and their association with nanomaterials, such as alginate, chitosan, hyaluronic acid and gelatin. A promising material is bacterial cellulose hydrogel, due to its nanostructure and morphology being similar to collagen. Cellulose provides support and immobilization of cells, which can result in better cell adhesion, growth and proliferation, making it a safe and innovative material for cardiovascular repair.

Usefulness of cardiac biomarker screening to detect dilated cardiomyopathy in UK Dobermanns

OBJECTIVES

To assess the efficacy of two cardiac biomarker assays (N-terminal pro-BNP and his sensitivity Troponin I (Beckman Coulter Access)) in detecting Dobermann dilated cardiomyopathy.

MATERIALS AND METHODS

Dobermanns undergoing cardiac biomarker testing were screened by echocardiography and Holter monitoring, then assigned to a group: normal, equivocal, arrhythmia form of dilated cardiomyopathy, echocardiographic form of dilated cardiomyopathy or both. Some were reassessed to identify final status. Initial cardiac biomarker results were compared to final status. Receiver operating characteristic curves were used to identify area under the curve and corresponding sensitivity (Se), specificity (Sp) for different cut-offs (CO) for each cardiac biomarker.

RESULTS

A total of 118 Dobermanns with cardiac biomarker data had echocardiography/Holter assessment. Repeat assessment was carried out in 47 Dobermanns after 394.5 ±151.0 days. Seventeen dogs changed group between initial and final status. The final status of 59 was normal, nine were equivocal and 50 had dilated cardiomyopathy (prevalence 42.4%). Of the dilated cardiomyopathy group, 25 had dilated cardiomyopathy-both, 13 dilated cardiomyopathy-echocardiography and 12 dilated cardiomyopathy-Holter. Receiver operating characteristic area under the curve=0.807 for N-terminal proBNP (Se 0.69 and Sp 0.81) and 0.873 for high-sensitivity cardiac Troponin I (Se 0.77 and Sp 0.86). When both Se and Sp were optimised for all forms of dilated cardiomyopathy, N-terminal proBNP cut-off was 626 pmol/L (Se and Sp 0.79) and high-sensitivity cardiac Troponin I cut-off was 0.056 ng/mL (Se and Sp 0.84). Receiver operating characteristic area under the curve was higher for dilated cardiomyopathy-echocardiography (NT-proBNP 0.883; high-sensitivity cardiac Troponin I 0.907) than dilated cardiomyopathy-Holter.

CLINICAL SIGNIFICANCE

Cardiac biomarker screening may be useful to select Dobermanns which would benefit from further assessment by echocardiography and Holter.

Screening for dilated cardiomyopathy in dogs

BACKGROUND

Dilated cardiomyopathy (DCM) is the most common cardiac disease in large breed dogs. The disease can start with arrhythmias or with systolic dysfunction of the myocardium.

OBJECTIVE

To describe screening methods for DCM in various breeds and provide a new, modified staging system.

RECOMMENDATIONS

Screening for occult DCM should start at three years of age and use Holter monitoring in Boxers and Dobermans and might be useful also in other breeds. Single ventricular premature complexes (VPCs) can be detected in many healthy dogs, but healthy animals typically have <50 VPCs in 24 h and demonstrate minimal complexity most often occurring only as single ectopic beats. In general, >100 VPCs in 24 h was recommended as the cut-off value for establishing a diagnosis of DCM. However, there are breed-specific recommendations related to Holter recording diagnosis of DCM in Dobermans and Boxers. Yearly screening over the life of a dog is recommended, as a one-time screening is not sufficient to rule out the future development of DCM. Several echocardiographic methods such as M-mode derived measurements, the measurement of the left ventricular (LV) volume by Simpson's method of discs (SMOD), and E-point to septal separation (EPSS) are recommended for screening purposes. The value of additional tests such as cardiac biomarkers (troponin I and N-terminal pro-B-type natriuretic peptide) as well as a 5-min resting electrocardiogram (ECG) or newer echocardiographic methods such as strain measurements is discussed.

CONCLUSION

This review suggests some guidelines for screening for DCM in various breeds.

Clinical findings associated with N-terminal pro-B-type natriuretic peptide measurement in dogs and cats attending first opinion veterinary practices

BACKGROUND

Clinical findings associated with N-terminal pro-B-type natriuretic peptide (NT-proBNP) measurement in dogs and cats in primary practice, and their relevance to published measurement indications, have not been described.

METHODS

Using electronic health record data collected by the Small Animal Veterinary Surveillance Network, appointments in which NT-proBNP was measured were identified using keyword-based text filtering. For these appointments, clinical findings were manually identified from each patient's clinical narrative (CN) and their frequencies described.

RESULTS

CNs of 3510 appointments (357 dogs and 257 cats) from 99practices were evaluated. The most frequently recorded clinical findings in dogs were: heart murmur (n = 147, 41.2% (95% confidence interval (CI) = 36.1%-46.3%), coughing (n = 83, 23.2% (95% CI = 18.8%-27.6%)) and panting (n = 58, 16.2% (95% CI = 12.4%-20.0%)) and in cats: heart murmur (n = 143, 55.6% (95% CI = 49.5%-61.7%)), suspected thromboembolism (n = 88, 34.2% (95% CI = 28.4%-40.0%)) and weight loss (n = 53, 20.6% (95% CI = 15.7%-25.5%)). Dyspnoea and tachypnoea were infrequently reported in dogs (n = 29, 8.1% (95% CI = 5.3%-10.9%) and n = 21, 5.9% (95% CI = 3.5%-8.3%), respectively) and cats (n = 26, 10.1% (95% CI = 6.4%-13.8%) and n = 36, 14.0% (95% CI = 9.8%-18.2%), respectively).

CONCLUSION

Clinical findings referable to cardiac disease were recorded contemporaneously with NT-proBNP measurement and suggested both published and other indications (coughing (in dogs and cats), and serial measurements and thromboembolism (in cats)) for testing.

Investigation of diets associated with dilated cardiomyopathy in dogs using foodomics analysis

Dilated cardiomyopathy (DCM) is a disease of the heart muscle that affects both humans and dogs. Certain canine diets have been associated with DCM, but the diet-disease link is unexplained, and novel methods are needed to elucidate mechanisms. We conducted metabolomic profiling of 9 diets associated with canine DCM, containing ≥ 3 pulses, potatoes, or sweet potatoes as main ingredients, and in the top 16 dog diet brands most frequently associated with canine DCM cases reported to the FDA (3P/FDA diets), and 9 non-3P/FDA diets. We identified 88 named biochemical compounds that were higher in 3P/FDA diets and 23 named compounds that were lower in 3P/FDA diets. Amino acids, amino acid-derived compounds, and xenobiotics/plant compounds were the largest categories of biochemicals that were higher in 3P/FDA diets. Random forest analyses identified the top 30 compounds that distinguished the two diet groups with 100% predictive accuracy. Four diet ingredients distinguished the two diet groups (peas, lentils, chicken/turkey, and rice). Of these ingredients, peas showed the greatest association with higher concentrations of compounds in 3P/FDA diets. Moreover, the current foodomics analyses highlight relationships between diet and DCM in dogs that can identify possible etiologies for understanding diet-disease relationships in dogs and humans.

Prospective clinical trial evaluating spironolactone in Doberman pinschers with congestive heart failure due to dilated cardiomyopathy

INTRODUCTION/OBJECTIVES

Whether the aldosterone antagonist spironolactone has beneficial survival effects in dogs with dilated cardiomyopathy (DCM) is not known. The primary objective of the study was to evaluate the effect of spironolactone, when added to conventional therapy, on survival time in Doberman pinschers with congestive heart failure (CHF) due to DCM.

ANIMALS

Sixty-seven client-owned Doberman pinschers with CHF due to DCM.

MATERIALS AND METHODS

The trial design was prospective, randomized, blinded, and placebo controlled. Dogs were randomized to receive 50-75 mg of spironolactone twice daily (n = 34) or a placebo (n = 33), in addition to standard CHF therapy. Follow-up visits were targeted every 1-6 weeks until endpoint. Quality-of-life questionnaire and physical examination were performed at every visit, while renal biochemistry, ECG, echocardiography, and thoracic radiography were reassessed as needed. The primary endpoint was time to cardiac death, defined as death or euthanasia from CHF or sudden death.

RESULTS

Median time to primary endpoint in the spironolactone group (183 days) was not statistically significantly different than that for the placebo group (124 days) (p = 0.254). The development of atrial fibrillation (AF) was significantly less frequent in the spironolactone group (n = 7) than the placebo group (n = 15, p = 0.037).

CONCLUSIONS

While median time to cardiac death in the spironolactone group was not statistically significantly different than that in the placebo group, adding spironolactone to conventional therapy resulted in reduced occurrence of AF.

Comparison of three two-dimensional echocardiographic methods of assessing left ventricular size in Doberman Pinschers

INTRODUCTION

Compare three methods of obtaining linear left ventricular dimensions within the same Doberman Pinscher (DP).

ANIMALS

One hundred and thirty-nine client-owned DP.

MATERIALS AND METHODS

Linear left ventricular dimensions were measured using two-dimensional short-axis (Sx-2D), motion-mode short-axis (Sx-MM), and motion-mode long-axis (Lx-MM) methods, then left ventricular volumes were obtained using monoplane Simpson's method of discs (SMOD). A Friedman test with Dunn's multiple comparisons was used to compare differences between methods. Bias and correlation were evaluated via Bland-Altman and Spearman's correlation. Sensitivity and specificity for diagnosing occult dilated cardiomyopathy (DCM) compared to SMOD were determined. Coefficients of variation (CVs) were calculated for intra- and inter-observer measurement variability.

RESULTS

There were significant differences between all linear dimensions in diastole and systole. Short-axis 2D measurements had significant bias compared with Sx-MM (diastole +1.19 mm, systole +1.65 mm) and Lx-MM (diastole +4.36 mm, systole +3.87 mm) as did Sx-MM compared with Lx-MM (diastole +3.17 mm, systole +2.22 mm). All linear dimensions had a moderate positive correlation with SMOD. The sensitivity and specificity of linear measurements to detect DCM were: Sx-2D (sensitivity 72.0%, specificity 88.5%), Sx-MM (sensitivity 52.0%, specificity 92.0%), and Lx-MM (sensitivity 37.5%, specificity 99.1%). All methods had acceptably low CV for intra- and inter-observer measurement variability.

CONCLUSIONS

Results of this study suggest that linear measurements are repeatable and correlate with reference standard; however, there is a significant bias between measurements, and they should not be used interchangeably.

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.

A review of the underlying genetics and emerging therapies for canine cardiomyopathies

Cardiomyopathies such as dilated cardiomyopathy and arrhythmogenic right ventricular cardiomyopathy are common in large breed dogs and carry an overall poor prognosis. Research shows that these diseases have strong breed predilections, and selective breeding has historically been recommended to reduce the disease prevalence in affected breeds. Treatment of these diseases is typically palliative and aimed at slowing disease progression and managing clinical signs of heart failure as they develop. The discovery of specific genetic mutations underlying cardiomyopathies, such as the striatin mutation in Boxer arrhythmogenic right ventricular cardiomyopathy and the pyruvate dehydrogenase kinase 4 and titin mutations in Doberman Pinschers, has strengthened our ability to screen and selectively breed individuals in an attempt to produce unaffected offspring. The discovery of these disease-linked mutations has also opened avenues for the development of gene therapies, including gene transfer and genome-editing approaches. This review article discusses the known genetics of cardiomyopathies in dogs, reviews existing gene therapy strategies and the status of their development in canines, and discusses ongoing challenges in the clinical translation of these technologies for treating heart disease. While challenges remain in using these emerging technologies, the exponential growth of the gene therapy field holds great promise for future clinical applications.

Echocardiographic reference intervals in healthy UK deerhounds and prevalence of preclinical dilated cardiomyopathy: a prospective, longitudinal study

BACKGROUND

Sighthounds have high echocardiographic (ECHO) left ventricular volumes. Establishing robust breed-specific ECHO reference intervals (RI) for screening is important. End-diastolic volume index (EDVI), end-systolic volume index (ESVI) and ejection fraction (EF) reference ranges derived by Simpson's method of discs are not available for deerhounds. The influence of sex or body weight (BW) on left ventricular diameter during diastole (LVDd) and systole (LVDs) has never been reported.

OBJECTIVES

Prospectively determine ECHO RI and assess prevalence of dilated cardiomyopathy (DCM) in healthy UK deerhounds.

ANIMALS

Ninety-nine deerhounds.

METHODS

Deerhounds scored on ECHO and ECG variables then classified as normal (NORM), equivocal (EQUIV) or affected (AFF) with DCM. Fifty-nine NORM deerhounds used to determine ECHO RI.

RESULTS

Prevalence of DCM was 21.6%. There were significant differences in BW (p<0.001), LVDd (p<0.001) and LVDs (p<0.05) between female and male deerhounds. Cut-off values for EDVI (≥140.2 mL/m²: 79% sensitivity/97% specificity), ESVI (≥71.9 mL/m²: 94.7% sensitivity/94.2% specificity) and EF (≤42.1%: 84.2% sensitivity/92.8% specificity) were proposed to help diagnose DCM. The most reliable ECHO variables to identify AFF dogs were LVDs indexed to BW by allometric scaling and ESVI; one of the least reliable was sphericity index. Ventricular arrhythmias (VA) were identified in 13.6% of the population, with the highest prevalence in AFF deerhounds (42%).

CONCLUSIONS

Preclinical DCM in deerhounds is common and VA may be associated with DCM. Healthy deerhounds have higher LVDd, LVDs and EDVI compared with other breeds. This study provides ECHO RIs for deerhounds; sex or BW RIs should be used when screening.

Assessment of PDK4 and TTN gene variants in 48 Doberman Pinschers with dilated cardiomyopathy

OBJECTIVE

To evaluate the frequency of variants in the pyruvate kinase dehydrogenase 4 (PDK4) and titin (TTN) genes in a group of Doberman Pinschers with dilated cardiomyopathy (DCM) and to determine whether there were unique clinical attributes to each variant.

ANIMALS

48 Doberman Pinschers with DCM.

PROCEDURES

Doberman Pinschers with recently diagnosed DCM were identified, and genomic DNA from each was genotyped with a PCR assay for detection of PDK4 and TTN genetic variants. Dogs were grouped on the basis of whether they had the TTN variant alone, PDK4 variant alone, both variants, or neither variant. Descriptive statistics were compiled for dog age, body weight, and left ventricular dimensions and fractional shortening and for the presence of ventricular and supraventricular arrhythmias and heart failure. Results were compared across groups.

RESULTS

Of the 48 dogs, 28 had the TTN variant alone, 10 had both variants, 6 had neither variant, and 4 had the PDK4 variant alone. The mean age was younger for dogs with the PDK4 variant alone, compared with other dogs. However, the number of dogs with the PDK4 variant alone was very small, and there was an overlap in age across groups. No other meaningful differences were detected across groups, and independent genotype-phenotype relationships were not identified.

CONCLUSIONS AND CLINICAL RELEVANCE

Although findings indicated that the TTN variant was most common, 6 dogs had neither variant, and this fact supported the concept of ≥ 1 other genetic contributor to DCM in Doberman Pinschers. Future studies are warranted to evaluate genotype-phenotype relationships in Doberman Pinschers with DCM.

Species-Spanning Echocardiography: Cardiovascular Insights from Across the Animal Kingdom

PURPOSE OF REVIEW

The objective of this review is to present comparative echocardiography as a source of insights for human cardiovascular medicine.

RECENT FINDINGS

We present echocardiographic examples of high impact human cardiovascular pathologies, including valvular, vascular, conduction, and myocardial disorders, in a wide range of species in varying environments. Unique features associated with comparative echocardiographic assessments are linked to human cardiology, including natural animal models of resistance and vulnerability. The cardiovascular vulnerabilities and strengths of other species can be a source of invaluable insights for human healthcare professionals. Echocardiography is playing a key role in bridging human and veterinary cardiology. Consequently, species-spanning echocardiography can deliver novel insights for human medicine.

The role of atrial fibrillation as a prognostic factor in doberman pinschers with dilated cardiomyopathy and congestive heart failure

Atrial fibrillation (AF) in congestive heart failure (CHF) is associated with a high risk of mortality and shorter survival times in human and veterinary medicine. A retrospective review of medical records was performed to evaluate the impact of AF on survival times in Doberman Pinschers with dilated cardiomyopathy (DCM). Time of first onset of CHF and its role as a prognostic factor were also determined, as were predictors of AF development. Forty-eight client-owned purebred Doberman Pinschers with DCM and CHF were included; 23 dogs presented with AF and 25 dogs did not develop AF until immediately before cardiac-related death. Dogs with AF survived for significantly shorter times than those without AF (P = 0.043). For dogs with AF, mean and median survival times were 88.2 days and 22 days, respectively (range, 42.1-134.4 days); mean and median survival times for dogs without AF were 150.7 days and 98 days, respectively (range, 98.5-203 days). AF increased the risk of cardiac-related death (hazard ratio [HR], 2.371; 95% confidence intervals [CI], 1.14-4.95; P = 0.021). Biventricular and right atrial dilation was only present in dogs with AF and right atrial enlargement was the only significant predictor of AF after multivariate analysis (P < 0.001). Dogs with AF had significantly higher mean heart rates than dogs without AF (201 beats per min [bpm] vs. 132 bpm; P < 0.001). In conclusion, AF in Doberman Pinschers with DCM and CHF increased the risk of cardiac-related death and reduced survival time.

Large Animal Models in Regenerative Medicine and Tissue Engineering: To Do or Not to Do

Rapid developments in Regenerative Medicine and Tissue Engineering has witnessed an increasing drive toward clinical translation of breakthrough technologies. However, the progression of promising preclinical data to achieve successful clinical market authorisation remains a bottleneck. One hurdle for progress to the clinic is the transition from small animal research to advanced preclinical studies in large animals to test safety and efficacy of products. Notwithstanding this, to draw meaningful and reliable conclusions from animal experiments it is critical that the species and disease model of choice is relevant to answer the research question as well as the clinical problem. Selecting the most appropriate animal model requires in-depth knowledge of specific species and breeds to ascertain the adequacy of the model and outcome measures that closely mirror the clinical situation. Traditional reductionist approaches in animal experiments, which often do not sufficiently reflect the studied disease, are still the norm and can result in a disconnect in outcomes observed between animal studies and clinical trials. To address these concerns a reconsideration in approach will be required. This should include a stepwise approach using in vitro and ex vivo experiments as well as in silico modeling to minimize the need for in vivo studies for screening and early development studies, followed by large animal models which more closely resemble human disease. Naturally occurring, or spontaneous diseases in large animals remain a largely untapped resource, and given the similarities in pathophysiology to humans they not only allow for studying new treatment strategies but also disease etiology and prevention. Naturally occurring disease models, particularly for longer lived large animal species, allow for studying disorders at an age when the disease is most prevalent. As these diseases are usually also a concern in the chosen veterinary species they would be beneficiaries of newly developed therapies. Improved awareness of the progress in animal models is mutually beneficial for animals, researchers, human and veterinary patients. In this overview we describe advantages and disadvantages of various animal models including domesticated and companion animals used in regenerative medicine and tissue engineering to provide an informed choice of disease-relevant animal models.

Discovery of os cordis in the cardiac skeleton of chimpanzees (Pan troglodytes)

Cardiovascular diseases, especially idiopathic myocardial fibrosis, is one of the most significant causes of morbidity and mortality in captive great apes. This study compared the structure and morphology of 16 hearts from chimpanzees (Pan troglodytes) which were either healthy or affected by myocardial fibrosis using X-ray microtomography. In four hearts, a single, hyperdense structure was detected within the right fibrous trigone of the cardiac skeleton. High resolution scans and histopathology revealed trabecular bones in two cases, hyaline cartilage in another case and a focus of mineralised fibro-cartilaginous metaplasia with endochondral ossification in the last case. Four other animals presented with multiple foci of ectopic calcification within the walls of the great vessels. All hearts affected by marked myocardial fibrosis presented with bone or cartilage formation, and increased collagen levels in tissues adjacent to the bone/cartilage, while unaffected hearts did not present with os cordis or cartilago cordis. The presence of an os cordis has been described in some ruminants, camelids, and otters, but never in great apes. This novel research indicates that an os cordis and cartilago cordis is present in some chimpanzees, particularly those affected by myocardial fibrosis, and could influence the risk of cardiac arrhythmias and sudden death.

The prevalence of atrial premature complexes in healthy Doberman Pinschers and their role in the diagnosis of occult dilated cardiomyopathy

The importance of atrial premature complexes (APCs) as a possible marker of occult dilated cardiomyopathy (DCM) in Doberman Pinschers (DP) is unknown. The aim of this study was to identify APC in healthy DP and to investigate their role as early markers of occult DCM. Holter-ECG results from 561 examinations of 153 DP at different time points were retrospectively evaluated, with special emphasis on APCs. Holter results from 110 healthy control DPs were compared to the last normal Holter and echocardiographic examinations in 43 DP that subsequently developed DCM within 15 months (DCM group), and to the first examination in the DCM group that contained ventricular premature complexes (VPC). There were no significant differences in the number of APCs or the coupling interval between the control group and the last normal examination in the DCM group (P > 0.05). The number of APCs increased slightly at the first abnormal examination in the DCM group. Healthy male DP had more APCs than females (P = 0.009) and older dogs had APCs more frequently than younger dogs (P < 0.001). About 85% of healthy DP with at least one APC/24 h had <20 APCs/24 h. Extracardiac diseases, especially gastrointestinal diseases influenced the occurrence of APCs (P = 0.037 and P = 0.006, respectively). APCs were present without obvious cardiac disease and were not a marker for the development of DCM, as they were not identified until after VPCs were present.

Review of canine dilated cardiomyopathy in the wake of diet-associated concerns

Dilated cardiomyopathy (DCM) has been in the literature and news because of the recent opinion-based journal articles and public releases by regulatory agencies. DCM is commonly associated with a genetic predisposition in certain dog breeds and can also occur secondary to other diseases and nutritional deficiencies. Recent communications in veterinary journals have discussed a potential relationship between grain-free and/or novel protein diets to DCM, citing a subjective increase in DCM in dog breeds that are not known to have a genetic predisposition for the disease. This literature review describes clinical presentations of DCM, common sequelae, treatment and preventative measures, histopathologic features, and a discussion of the varied etiological origins of the disease. In addition, current literature limitations are addressed, in order to ascertain multiple variables leading to the development of DCM. Future studies are needed to evaluate one variable at a time and to minimize confounding variables and speculation. Furthermore, to prevent sampling bias with the current FDA reports, the veterinary community should be asked to provide information for all cases of DCM in dogs. This should include cases during the same time period, regardless of the practitioner's proposed etiology, due to no definitive association between diets with specific characteristics, such as, but not limited to, grain-free diets and those containing legumes, novel protein diets, and those produced by small manufacturers to DCM in dogs. In summary, in order to determine if certain ingredients, categories of diets, or manufacturing processes are related to an increased risk of DCM, further studies investigating these variables are necessary.

Retrospective Study of Intercalated Disk Defects Associated with Dilated Cardiomyopathy, Atrial Thrombosis, and Heart Failure in BALB/c Mice Deficient in IL4 Receptor α

An increased incidence of dilated cardiomyopathy and atrial thrombosis was noted in a breeding colony of BALB/c mice deficient in IL4 receptor α. The condition affected mice of both sexes and of various ages, and extensive testing (microbiology, serology, histopathology) failed to ascertain the cause. Transmission electron microscopy of heart samples showed structural defects in the myocardial intercalated disks, characterized by unorganized and heavily convoluted arrangement with lower density and less prominent desmosomes and adherens junctions, widening of the intercellular space, myofibrillar lysis adjacent to intercalated disks, occasional sarcomere lysis with marked myofiber degeneration, vacuolation, accumulation of cell debris, and myelin figures. The intercalated disk contains cell adhesion molecules that form cell junctions, allowing contraction coupling of cardiomyocytes and the electrical and mechanical connection between cardiac fibers. Thus, defects at this level result in poor myocardial contraction, intracardiac blood stagnation, and consequently cardiac dilation with clinical signs of heart failure. The background strain or, potentially, the Cre-loxP-mediated recombination system used to create these mice may have contributed to the elevated incidence of cardiomyopathy and atrial thrombosis in this colony. Due to the backcrossing breeding scheme used, we cannot discount the emergence and colonywide dissemination of a spontaneous mutation that affects the intercalated disk. This report underscores the importance of carefully monitoring genetically modified mice colonies for unexpected phenotypes that may result from spontaneous or unintended mutations or enhanced strain background pathology.

The aptamer BC 007 for treatment of dilated cardiomyopathy: evaluation in Doberman Pinschers of efficacy and outcomes

Aims

Aptamer BC 007, a 15‐mer single‐strand DNA oligonucleotide (5'‐GGTTGGTGTGGTTGG‐3'), was developed to neutralize functional autoantibodies that bind to the extracellular domains of G protein‐coupled receptors (GPCR‐AAB), leading to the modulation of receptor‐mediated signalling cascades that induce pathophysiological states. Among the GPCR‐AAB, there are those directed against the β1‐adrenergic receptor (β1‐AAB) that are highly present in patients with dilated cardiomyopathy (DCM) and are increasingly accepted as disease drivers.

Using Doberman Pinschers (DP) with DCM, which possess similarities with human DCM among these β1‐AAB positivity for that the disease‐driving role in DP DCM was demonstrated, the safety of BC 007, efficacy for neutralizing β1‐AAB, and the DP's outcome were investigated.

Methods and results

Fourteen client‐owned β1‐AAB‐positive DP with electrocardiographically and echocardiographically indicated DCM were treated with BC 007. For controlling, two groups were created: 14 β1‐AAB‐positive DP with DCM not treated with BC 007 (Control 1) and 14 DP with DCM closely matched to the BC 007‐treated DP (Control 2), retrospectively selected from the institutional database of DP. After treatment, DP were monitored both echocardiographically, and for β1‐AAB, and survival curves were calculated. Based on clinical and laboratory examination, no adverse effects associated with BC 007 treatment were observed during the study. Forty‐eight hours after treatment, the DP's blood was free of β1‐AAB, which led to a reduction or stabilization of left ventricular end‐systolic volume (ESVI) during β1‐AAB free time in 10 of the treated DP. In one DP, where β1‐AAB returned after 3 months and ESVI worsened again, a second BC 007 treatment after 9 months again cleared the blood from β1‐AAB and improved the ESVI. Compared with the controls, DP treated with BC 007 showed a significantly longer survival time [572 days, interquartile range (IQR) 442–840 days] vs. Control group 1 (266 days, IQR 97–438 days; logrank: P = 0.009) and Control group 2 (229 days, IQR 174–319 days; logrank: P = 0.012).

Conclusions

Treatment with BC 007 for β1‐AAB neutralization was safe, resulted in a long‐lasting reduction of β1‐AAB combined with improved cardiac function and prolonged the survival of DP with DCM. Using a natural large animal model of DCM considered superior to small animal models of immunization‐induced cardiomyopathy, combined with a study design comparable with clinical trials, we believe that our results provide the basis for optimism that treatment with BC 007 might also be effective in human patients with DCM.

Canine Dilated Cardiomyopathy: Diffuse Remodeling, Focal Lesions, and the Involvement of Macrophages and New Vessel Formation

Dilated cardiomyopathy (DCM) is among the most common cardiac diseases in dogs. Its pathogenesis is not fully understood, but myocardial remodeling and inflammation are suspected to be involved. The present study aimed to characterize the pathological processes in canine DCM, investigating morphological changes in association with the expression of relevant cytokines and remodeling markers. The myocardium of 17 dogs with DCM and 6 dogs without cardiac diseases was histologically evaluated, and selected cases were further examined by immunohistochemistry, morphometry, and reverse transcription quantitative PCR. In DCM, the myocardium exhibited subtle but statistically significant diffuse quantitative changes. These comprised increased interstitial collagen deposition and macrophage numbers, as well as an overall reduced proportion of contractile tissue. This was accompanied by a significant increase in myocardial transcription of intracellular adhesion molecule (ICAM) 1, inflammatory cytokines, and remodeling enzymes. Laser microdissection showed that cardiomyocytes transcribed most relevant markers including ICAM-1, tumor necrosis factor α, transforming growth factor β (TGF-β), matrix metalloproteinase 2 (MMP-2), tissue inhibitor of MMP (TIMP) 1 and TIMP-2. In addition, there were multifocal cell-rich lesions characterized by fibrosis, neovascularization, macrophage infiltration, and cardiomyocyte degeneration. In these, macrophages were often found to express ICAM-1, TGF-β, and vascular endothelial growth factor; the former two were also expressed by cardiomyocytes. These results characterize the diffuse myocardial remodeling processes that occur in DCM. The observed multifocal cell-rich lesions might result from reduced tissue perfusion. Macrophages and cardiomyocytes seem to actively contribute to the remodeling processes, which ultimately lead to cardiac dilation and dysfunction. The precise role of the involved cells and the factors initiating the remodeling process still needs to be identified.

Comparison of single- versus seven-day Holter analysis for the identification of dilated cardiomyopathy predictive criteria in apparently healthy Doberman Pinscher dogs

INTRODUCTION

The primary objective of this study was to test whether seven-day Holter recording improves the sensitivity of detecting dilated cardiomyopathy (DCM) predictive criteria (DCM_p) compared with 24-h Holter recording in asymptomatic Doberman Pinscher (DP) dogs.

ANIMALS

Twenty-eight asymptomatic DP dogs with normal echocardiographic examinations.

METHODS

Dogs with normal echocardiographic examinations underwent seven-day Holter monitoring. The presence of ≥50 ventricular premature complexes and or ≥ one couplet/one triplet/one episode of ventricular tachycardia per 24-h period was considered positive for DCM_p.

RESULTS

Five dogs were positive on the first day, and an additional six dogs tested positive from day two to seven of the Holter recording. The number of dogs positive for DCM_p detected by four days was significantly different (p = 0.031) compared with the first-day Holter recording.

CONCLUSIONS

Seven-day Holter recording detected significantly more dogs with DCM_p compared with the first-day Holter recording. Follow-up studies are warranted to evaluate the long-term accuracy of multiple-day Holter analysis in predicting the development of DCM in DP dogs.

Diagnostic methods for the canine idiopathic dilated cardiomyopathy: A narrative evidence-based rapid review

Idiopathic dilated cardiomyopathy (DCM) is an important etiology of mortality and morbidity in dogs and its diagnosis relies on systolic dysfunction, chambers dilation, electrical instability and congestion. During the last decades veterinary cardiologists have been joining efforts to obtain diagnostic resources to correctly identify canine DCM in the preclinical stage. Unfortunately, most diagnostic resources have been used with the support of research with weak evidence, without high quality methodologies such as systematic reviews or meta-analysis. Therefore, the support of evidence-based medicine is tailored by empiricism and diagnostic criteria lose'out the ability to properly classify dogs suffering DCM. The presentation of the evidence in medicine is established by multiple sources and the most reliable source has been the presentation of evidence-based medicine from systematic reviews and meta-analysis. Rapid reviews can be interpreted as a pragmatic approach to systematic reviews and although a rapid review follows most of the critical steps of a systematic review to provide timely evidence, some components of a systematic review process are either simplified or omitted. The objective of this narrative evidence-based rapid review is twofold. First: To recognize and to stratify the level of evidence offered by rigorous selected papers about the diagnosis of DCM. Second: To classify the degree of clinical recommendation of the diagnostic resources available.

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.

Doberman pinschers present autoimmunity associated with functional autoantibodies: A model to study the autoimmune background of human dilated cardiomyopathy

Background

Autoimmunity associated with autoantibodies against the β1-adrenergic receptor (β1-AAB) is increasingly accepted as the driver of human dilated cardiomyopathy (DCM). Unfortunately, there is a lack of animal models to extend the knowledge about β1-AAB autoimmunity in DCM and to develop appropriate treatment strategies.

Objectives

To introduce an animal model, we investigated the β1-AAB associated autoimmunity in Doberman Pinscher (DP) with dilated cardiomyopathy, which has similarities to human DCM.

Materials and methods

Eighty-seven DP with cardiomyopathy in terms of pathological ECG and echocardiography (DoCM) and 31 dogs (at enrollment) without DoCM (controls) were analyzed for serum activity of β1-AAB with a bioassay that records the chronotropic response of spontaneously beating cultured neonatal rat cardiomyocytes to the DP’s IgG. To locate the receptor binding site of β1-AAB and the autoantibody’s sensitivity to inhibition, competing experiments with related blockers were performed with the bioassay. In controls that developed DoCM during follow-up, β1-AAB were analyzed during progress.

Results

Fifty-nine (67.8%) DoCM dogs and 19 (61.3%) controls were β1-AAB positive. Of the controls that developed DoCM, 8 were β1-AAB positive (p = 0.044 vs. dogs remaining in the control group); their β1-AAB activity increased with the cardiomyopathy progress (p<0.02). To supplement DoCM group with the 9 animals which developed cardiomyopathy in the follow up, a more pronounced β1-AAB positivity became visible in the DoCM group (p = 0.066).

Total and cardiac mortality were higher in β1-AAB positive DP (p = 0.002; p = 0037). The dogs’ β1-AAB recognized a specific epitope on the second extracellular receptor and were sensitive to inhibition by drugs already successfully tested to inhibit the corresponding human autoantibody.

Conclusions

Doberman Pinschers presented β1-AAB associated autoimmunity, similar as in the pathogenesis of human DCM. Consequently, DP could compensate the lack of animal models for the investigation of β1-AAB autoimmunity in human DCM.

Evaluation of a high-sensitivity cardiac troponin I assay compared to a first-generation cardiac troponin I assay in Doberman Pinschers with and without dilated cardiomyopathy

BACKGROUND

Echocardiography and 24-hour ECG are the gold standard tests to diagnose dilated cardiomyopathy (DCM) in Doberman Pinschers (DP), but myocardial damage might be detected earlier using a high-sensitivity cardiac troponin I (hs-cTnI) assay.

OBJECTIVE

To evaluate and compare an hs-cTnI assay (Advia Centaur TnI-Ultra assay) with a conventional cTnI assay in DP with different stages of DCM and in healthy DP.

ANIMALS

Three hundred forty-five examinations from 162 DP with and 179 DP without DCM.

METHODS

Prospective longitudinal study. Dogs were allocated into 6 groups based on echocardiographic and 24-hour ECG criteria: (1) healthy group (179 dogs), (2) last-normal group (29 dogs), which included dogs that were considered to be healthy at the time of their examination but were assigned to the last-normal group retrospectively when DCM was diagnosed at their next examination within 1.5 years, (3) only arrhythmias (45 dogs, 119 examinations), (4) only echocardiographic changes (24 dogs, 61 examinations), (5) echocardiographic changes with ventricular premature complexes (41 dogs, 100 examinations), and (6) decompensated (23 dogs, 36 examinations). Hs-cTnI and conventional cTnI concentration measurements were performed and compared.

RESULTS

A cutoff value of hs-cTnI concentration >0.113 ng/mL had a sensitivity of 81.2% and a specificity of 73.2% to identify the presence of DCM. The conventional cTnI assay showed a similar test performance, but the hs-cTnI assay identified more dogs (21/29 dogs, 72%) in the last-normal group compared to the conventional cTnI test (18/29 dogs, 62%).

CONCLUSIONS AND CLINICAL IMPORTANCE

The hs-cTnI is an additional test with good potential to identify early DCM.

Inherited cardiomyopathies in veterinary medicine

Comparative and translation medicine is of particular value within the field of inherited cardiomyopathies. Despite massive advances in understanding the functional role of mutations in human cardiomyopathies, these advances have frequently failed to translate into medical discoveries that alter patient care. One potential explanation for this failure lies in the lack of suitable translational models that adequately recapitulate human cardiovascular physiology and disease expression. The vast genetic heterogeneity that complicates human cardiomyopathy research is potentially alleviated through the study of naturally occurring large animal models of disease, where incredibly homogenous populations, like those seen in a single breed of dog or cat, may exist (Kol et al., Sci Transl Med 7:308-321, 2015; Ueda and Stern, Yale J Biol Med 90:433-448, 2017). Veterinary medicine is in a unique position to provide research resources and information that may be readily applied to human disease (Kol et al., Sci Transl Med 7:308-321, 2015). Many inherited cardiomyopathies of humans are phenotypically and genotypically similar in veterinary species and ongoing research holds promise for aiding veterinary and human patients alike (Basso et al., Circulation 109:1180-1185, 2004; Fox et al., Cardiovasc Pathol 23:28-34, 2014; Fox et al., Circulation 102:1863-1870, 2000; Kittleson et al., J Vet Cardiol 17 Suppl 1:S53-73, 2015; Ueda and Stern, Yale J Biol Med 90:433-448, 2017). This article presents the current knowledge of inherited cardiomyopathies in dogs, cats, and non-human primates, with a goal of identifying areas of translational research and future directions.

Cardiosphere-derived cells suppress allogeneic lymphocytes by production of PGE2 acting via the EP4 receptor

Cardiosphere-derived cells (CDCs) are a cardiac progenitor cell population, which have been shown to possess cardiac regenerative properties and can improve heart function in a variety of cardiac diseases. Studies in large animal models have predominantly focussed on using autologous cells for safety, however allogeneic cell banks would allow for a practical, cost-effective and efficient use in a clinical setting. The aim of this work was to determine the immunomodulatory status of these cells using CDCs and lymphocytes from 5 dogs. CDCs expressed MHC I but not MHC II molecules and in mixed lymphocyte reactions demonstrated a lack of lymphocyte proliferation in response to MHC-mismatched CDCs. Furthermore, MHC-mismatched CDCs suppressed lymphocyte proliferation and activation in response to Concanavalin A. Transwell experiments demonstrated that this was predominantly due to direct cell-cell contact in addition to soluble mediators whereby CDCs produced high levels of PGE₂ under inflammatory conditions. This led to down-regulation of CD25 expression on lymphocytes via the EP4 receptor. Blocking prostaglandin synthesis restored both, proliferation and activation (measured via CD25 expression) of stimulated lymphocytes. We demonstrated for the first time in a large animal model that CDCs inhibit proliferation in allo-reactive lymphocytes and have potent immunosuppressive activity mediated via PGE₂.

Phenotypic description of cardiac findings in a population of Dogue de Bordeaux with an emphasis on atrial fibrillation

The aim of this study was to describe the clinical phenotype of Dogue de Bordeaux (DdB) referred for cardiac investigation, with particular reference to the prevalence of atrial fibrillation and associated features. Review of canine medical records of two United Kingdom veterinary referral hospitals identified 64 DdB with available echocardiographic and electrocardiographic (ECG)/Holter data. Atrial fibrillation was documented in 25 (39%) dogs and supraventricular tachycardia was recorded in five (7.8%) dogs. In a subset of 34 dogs, excluding congenital heart disease (n=17), presence of a cardiac mass (n=7) and non-cardiac neoplasia (n=6), 19 (56%) dogs had atrial fibrillation, with a median heart rate of 200 beats per min (bpm) on presentation. Atrial fibrillation was inconsistently associated with cardiac chamber remodelling, but was frequently associated with systolic dysfunction (13/19, 68.4%) and right sided atrial or ventricular dilatation (14/19, 73.7%) in dogs with atrial fibrillation in this subset. No dogs in this subset had right sided atrial or ventricular dilatation in the absence of supraventricular arrhythmia or systolic dysfunction. The absence of structural heart disease in some dogs with supraventricular arrhythmias suggests that an underlying primary arrhythmic process might be responsible for initiating remodelling, although a primary cardiomyopathy cannot be ruled out.

An update on canine cardiomyopathies - is it all in the genes?

Dilated cardiomyopathy is the second most common cardiac disease in dogs and causes considerable morbidity and mortality. Primary dilated cardiomyopathy is suspected to be familial, and genetic loci have been associated with the disease in a number of breeds. Because it is an adult-onset disease, usually with late onset, testing breeding dogs and bitches before breeding for a genetic mutation that could lead to dilated cardiomyopathy would be helpful to prevent disease. There is growing evidence that the genetic basis may be multigenic rather than monogenic in the majority of studied breeds. This review article describes the known genetic aspects of canine dilated cardiomyopathy and the implications of genetic tests on heart testing and the future of veterinary cardiology.

Predictors of Sudden Cardiac Death in Doberman Pinschers with Dilated Cardiomyopathy

Background

Doberman Pinschers with dilated cardiomyopathy (DCM) are at high risk of sudden cardiac death (SCD). Risk factors for SCD are poorly defined.

Aim

To assess cardiac biomarkers, Holter‐ECG, echocardiographic variables and canine characteristics in a group of Doberman Pinschers with DCM dying of SCD and in a DCM control group to identify factors predicting SCD.

Methods/Animals

A longitudinal prospective study was performed in 95 Doberman Pinschers with DCM. Forty‐one dogs died within 3 months after the last cardiac examination (SCD‐group) and were compared to 54 Doberman Pinschers with DCM surviving 1 year after inclusion. Holter‐ECG, echocardiography, measurement of N‐terminal prohormone of brain‐natriuretic peptide (NT‐proBNP), and cardiac Troponin I (cTnI) concentrations were recorded for all dogs.

Results

Volume overload of the left ventricle (left ventricular end‐diastolic volume (LVEDV/BSA) > 91.3 mL/m²) was the single best variable to predict SCD. The probability of SCD increases 8.5‐fold (CI_0.95 = 0.8–35.3) for every 50 mL/m²‐unit increment in LVEDV/BSA. Ejection fraction (EF), left ventricular end‐systolic volume (LVESV/BSA) and NT‐proBNP were highly correlated with LVEDV/BSA (r = −0.63, 0.96, 0.86, respectively). Generated conditional inference trees (CTREEs) revealed that the presence of ventricular tachycardia (VT), increased concentration of cTnI, and the fastest rate (FR) of ventricular premature complexes (VPC) ≥260 beats per minute (bpm) are additional important variables to predict SCD.

Conclusion

Conditional inference trees provided in this study might be useful for risk assessment of SCD in Doberman Pinschers with DCM.

PDK4 Deficiency Induces Intrinsic Apoptosis in Response to Starvation in Fibroblasts from Doberman Pinschers with Dilated Cardiomyopathy

The Doberman pinscher (DP) canine breed displays a high incidence of idiopathic, nonischemic dilated cardiomyopathy (DCM) with increased mortality. A common mutation in DPs is a splice site deletion in the pyruvate dehydrogenase kinase 4 (PDK4) gene that shows a positive correlation with DCM development. PDK4, a vital mitochondrial protein, controls the switch between glycolysis and oxidative phosphorylation based upon nutrient availability. It is likely, although unproven, that DPs with the PDK4 mutation are unable to switch to oxidative phosphorylation during periods of low nutrient availability, and thus are highly susceptible to mitochondrial-mediated apoptosis. This study investigated cell viability, mitochondrial stress, and activation of the intrinsic (mitochondrial mediated) apoptotic pathway in dermal fibroblasts from DPs that were healthy (PDK4^wt/wt), heterozygous (PDK4^wt/del), and homozygous (PDK4^del/del) for the PDK4 mutation under conditions of high (unstarved) and low (starved) nutrient availability in vitro. As hypothesized, PDK4^wt/del and PDK4^del/del cells showed evidence of mitochondrial stress and activation of the intrinsic apoptotic pathway following starvation, while the PDK4^wt/wt cells remained healthy and viable under these conditions. Adeno-associated virus (AAV) PDK4-mediated gene replacement experiments confirmed cause-effect relationships between PDK4 deficiency and apoptosis activation. The restoration of function observed following administration of AAV-PDK4 provides strong support for the translation of this gene therapy approach into the clinical realm for PDK4-affected Dobermans.

European Society of Veterinary Cardiology screening guidelines for dilated cardiomyopathy in Doberman Pinschers

BACKGROUND

Dilated cardiomyopathy (DCM) is the most common cardiac disease in large breed dogs and is inherited in Doberman Pinschers with a high prevalence (58%).

OBJECTIVE

The European Society for Veterinary Cardiology convened a task force to formulate screening guidelines for DCM in Dobermans.

RECOMMENDATIONS

Screening for occult DCM in Dobermans should start at three years of age and use both Holter monitoring and echocardiography. Yearly screening over the life of the dog is recommended, as a one-time screening is not sufficient to rule out future development of DCM. The preferred echocardiographic method is the measurement of the left ventricular volume by Simpson's method of discs (SMOD). Less than 50 single ventricular premature complexes (VPCs) in 24 h are considered to be normal in Dobermans, although detection of any number of VPCs is cause for concern. Greater than 300 VPCs in 24 h or two subsequent recordings within a year showing between 50 and 300 VPCs in 24 h is considered diagnostic of occult DCM in Dobermans regardless of the concurrent echocardiographic findings. The guidelines also provide recommendations concerning ancillary tests, that are not included in the standard screening protocol, but which may have some utility when recommended tests are not available or financially untenable on an annual basis. These tests include assay of cardiac biomarkers (Troponin I and N-Terminal pro-B-type Natriuretic Peptide) as well as a 5-min resting electrocardiogram (ECG).

CONCLUSION

The current guidelines should help to establish an early diagnosis of DCM in Dobermans.

Heart rate turbulence after ventricular premature beats in healthy Doberman pinschers and those with dilated cardiomyopathy

OBJECTIVES

To describe the measurement of heart rate turbulence (HRT) after ventricular premature beats and compare HRT in healthy Doberman pinschers and those with dilated cardiomyopathy (DCM), with and without congestive heart failure (CHF).

ANIMALS

Sixty-five client-owned Dobermans: 20 healthy (NORMAL), 31 with preclinical DCM and 14 with DCM and CHF (DCM + CHF).

METHODS

A retrospective study of data retrieved from clinical records and ambulatory ECG (Holter) archives, including data collected previously for a large-scale prospective study of Dobermans with preclinical DCM. Holter data were reanalysed quantitatively, including conventional time-domain heart rate variability and the HRT parameters turbulence onset and turbulence slope.

RESULTS

Heart rate turbulence could be measured in 58/65 dogs. Six Holter recordings had inadequate ventricular premature contractions (VPCs) and one exhibited VPCs too similar to sinus morphology. Heart rate turbulence parameter, turbulence onset, was significantly reduced in DCM dogs, whereas conventional heart rate variability measures were not. Heart rate variability and HRT markers were reduced in DCM + CHF dogs as expected.

CONCLUSIONS

Heart rate turbulence can be measured from the majority of good quality standard canine 24-hour Holter recordings with >5 VPCs. Turbulence onset is significantly reduced in Dobermans with preclinical DCM which indicates vagal withdrawal early in the course of disease. Heart rate turbulence is a powerful prognostic indicator in human cardiac disease which can be measured from standard 24-hour ambulatory ECG (Holter) recordings using appropriate computer software. Further studies are warranted to assess whether HRT may be of prognostic value in dogs with preclinical DCM and in other canine cardiac disease.

Feline Hypertrophic Cardiomyopathy: A Spontaneous Large Animal Model of Human HCM

Hypertrophic cardiomyopathy (HCM) is a common disease in pet cats, affecting 10-15% of the pet cat population. The similarity to human HCM, the rapid progression of disease, and the defined and readily determined endpoints of feline HCM make it an excellent natural model that is genotypically and phenotypically similar to human HCM. The Maine Coon and Ragdoll cats are particularly valuable models of HCM because of myosin binding protein-C mutations and even higher disease incidence compared to the overall feline population. The cat overcomes many of the limitations of rodent HCM models, and can provide enhanced translation of information from in vitro and induced small animal models to human clinical trials. Physicians and veterinarians working together in a collaborative and interdisciplinary approach can accelerate the discovery of more effective treatments for this and other cardiovascular diseases affecting human and veterinary patients.

Cryopreservation of canine cardiosphere-derived cells: Implications for clinical application

The clinical application of cardiosphere-derived cells (CDCs) to treat cardiac disease has gained increasing interest over the past decade. Recent clinical trials confirm their regenerative capabilities, although much remains to be elucidated about their basic biology. To develop this new treatment modality, in a cost effective and standardized workflow, necessitates the creation of cryopreserved cell lines to facilitate access for cardiac patients requiring urgent therapy. Cryopreservation may however lead to alterations in cell behavior and potency. The aim of this study was to investigate the effect of cryopreservation on canine CDCs. CDCs and mesenchymal stem cells (MSCs) isolated from five dogs were characterized. CDCs demonstrated a population doubling time that was unchanged by cryopreservation (fresh vs. cryopreserved; 57.13 ± 5.27 h vs. 48.94 ± 9.55 h, P = 0.71). This was slower than for MSCs (30.46 h, P < 0.05). The ability to form clones, self-renew, and commit to multiple lineages was unaffected by cryopreservation. Cryopreserved CDCs formed larger cardiospheres compared to fresh cells (P < 0.0001). Fresh CDCs showed a high proportion of CD105⁺ (89.0% ± 4.98) and CD44⁺ (99.68% ± 0.13) cells with varying proportions of CD90⁺ (23.36% ± 9.78), CD34⁺ (7.18% ± 4.03) and c-Kit⁺ (13.17% ± 8.67) cells. CD45⁺ (0.015% ± 0.005) and CD29⁺ (2.92% ± 2.46) populations were negligible. Increasing passage number of fresh CDCs correlated with an increase in the proportion of CD34⁺ and a decrease in CD90⁺ cells (P = 0.003 and 0.03, respectively). Cryopreserved CDCs displayed increased CD34⁺ (P < 0.001) and decreased CD90⁺ cells (P = 0.042) when compared to fresh cells. Overall, our study shows that cryopreservation of canine CDCs is feasible without altering their stem characteristics, thereby facilitating their utilization for clinical trials. © 2017 International Society for Advancement of Cytometry.

Multiple Genetic Associations with Irish Wolfhound Dilated Cardiomyopathy

Cardiac disease is a leading cause of morbidity and mortality in dogs and humans, with dilated cardiomyopathy being a large contributor to this. The Irish Wolfhound (IWH) is one of the most commonly affected breeds and one of the few breeds with genetic loci associated with the disease. Mutations in more than 50 genes are associated with human dilated cardiomyopathy (DCM), yet very few are also associated with canine DCM. Furthermore, none of the identified canine loci explain many cases of the disease and previous work has indicated that genotypes at multiple loci may act together to influence disease development. In this study, loci previously associated with DCM in IWH were tested for associations in a new cohort both individually and in combination. We have identified loci significantly associated with the disease individually, but no genotypes individually or in pairs conferred a significantly greater risk of developing DCM than the population risk. However combining three loci together did result in the identification of a genotype which conferred a greater risk of disease than the overall population risk. This study suggests multiple rather than individual genetic factors, cooperating to influence DCM risk in IWH.

Evaluation of artificial selection in Standard Poodles using whole-genome sequencing

Identifying regions of artificial selection within dog breeds may provide insights into genetic variation that underlies breed-specific traits or diseases-particularly if these traits or disease predispositions are fixed within a breed. In this study, we searched for runs of homozygosity (ROH) and calculated the d _i statistic (which is based upon F _ST) to identify regions of artificial selection in Standard Poodles using high-coverage, whole-genome sequencing data of 15 Standard Poodles and 49 dogs across seven other breeds. We identified consensus ROH regions ≥1 Mb in length and common to at least ten Standard Poodles covering 0.6 % of the genome, and d _i regions that most distinguish Standard Poodles from other breeds covering 3.7 % of the genome. Within these regions, we identified enriched gene pathways related to olfaction, digestion, and taste, as well as pathways related to adrenal hormone biosynthesis, T cell function, and protein ubiquitination that could contribute to the pathogenesis of some Poodle-prevalent autoimmune diseases. We also validated variants related to hair coat and skull morphology that have previously been identified as being under selective pressure in Poodles, and flagged additional polymorphisms in genes such as ITGA2B, CBX4, and TNXB that may represent strong candidates for other common Poodle disorders.

The dog aging project: translational geroscience in companion animals

Studies of the basic biology of aging have identified several genetic and pharmacological interventions that appear to modulate the rate of aging in laboratory model organisms, but a barrier to further progress has been the challenge of moving beyond these laboratory discoveries to impact health and quality of life for people. The domestic dog, Canis familiaris, offers a unique opportunity for surmounting this barrier in the near future. In particular, companion dogs share our environment and play an important role in improving the quality of life for millions of people. Here, we present a rationale for increasing the role of companion dogs as an animal model for both basic and clinical geroscience and describe complementary approaches and ongoing projects aimed at achieving this goal.