Multiple Genetic Associations with Irish Wolfhound Dilated Cardiomyopathy

Echocardiographic and electrocardiographic findings in Irish Wolfhounds eating high-pulse or low-pulse diets

BACKGROUND

Apparently healthy dogs of various breeds eating nontraditional, high-pulse diets can have larger left ventricular diameter, lower systolic function, and more ventricular premature complexes (VPCs) compared with dogs eating traditional, low-pulse diets. It is unknown whether Irish Wolfhounds eating high-pulse diets have similar cardiac abnormalities.

HYPOTHESIS/OBJECTIVES

To compare electrocardiographic and echocardiographic findings between Irish Wolfhounds eating high- or low-pulse diets.

ANIMALS

Ninety-seven Irish Wolfhounds.

METHODS

Retrospective study of Irish Wolfhounds that had echocardiography performed at dog shows between October 2018 and May 2021. Demographic information, echocardiographic measurements, cardiac rhythm (1-minute lead II rhythm strip), and main diet were recorded retrospectively. Diets were classified as high-pulse or low-pulse based on the presence and location of pulses (peas, lentils, chickpeas, or dry beans) on the ingredient list.

RESULTS

Thirty-five of 97 Irish Wolfhounds (36%) were eating high-pulse diets and 62 of 97 (64%) were eating low-pulse diets. There were no significant differences between diet groups in echocardiographic measurements. A significantly higher percentage of dogs in the high-pulse diet group (6/35 [17%]) had VPCs compared with those in the low-pulse diet group (1/62 [2%]; effect size = 0.15 [95% confidence interval: 0.004-0.31]; P = .005).

CONCLUSIONS AND CLINICAL IMPORTANCE

In this retrospective study of apparently healthy Irish Wolfhounds, high-pulse diets were associated with a higher prevalence of VPCs which could represent early cardiac abnormalities.

Cardiac Disease and Screening in Breeding Dogs

Acquired and congenital heart diseases are relatively common in dogs, particularly in certain breeds. Modes of inheritance and genetic causes have been established for several cardiac diseases within various breeds. Breed screening is used to try and reduce the prevalence of certain canine cardiac diseases. Although breed screening seems to help reduce the prevalence of canine heart disease, the outcomes of specific breeding programs are variable and depend on multiple factors.

Risk factors for atrial fibrillation in dogs with dilated cardiomyopathy

Introduction

Atrial fibrillation secondary to dilated cardiomyopathy (DCM) frequently affects large-breed dogs. The aim of the present study was to identify risk factors for the development of atrial fibrillation in dogs of different breeds with an echocardiographic diagnosis of DCM.

Methods

In this multicenter retrospective study, we searched the electronic databases of five cardiology referral centers for dogs with an echocardiographic diagnosis of DCM. A comparison of clinical and echocardiographic variables was performed between dogs developing atrial fibrillation and those not developing atrial fibrillation and the ability to distinguish between these two groups of dogs was evaluated by receiver operating characteristic curve analysis. Univariate and multivariable logistic regression analysis estimated the odds ratio (OR) with 95% confidence interval (CI) of developing atrial fibrillation.

Results

We included 89 client-owned dogs with occult and overt echocardiographic DCM. Of these, 39 dogs (43.8%) had atrial fibrillation, 29 dogs (32.6%) maintained a sinus rhythm, and 21 dogs (23.6%) showed other cardiac arrhythmias. Left atrial diameter had high accuracy (area under the curve = 0.816, 95% CI = 0.719-0.890) to predict the development of atrial fibrillation at the cut-off of >4.66 cm. After multivariable stepwise logistic regression analysis, only increased left atrial diameter (OR = 3.58, 95% CI = 1.87-6.87; p < 0.001) and presence of right atrial enlargement (OR = 4.02, 95% CI = 1.35-11.97; p = 0.013) were significant predictors of atrial fibrillation development.

Discussion

Atrial fibrillation is a common complication of DCM in the dog and is significantly associated with increased absolute left atrial diameter and right atrial enlargement.

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.

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.

Effect of diet change in healthy dogs with subclinical cardiac biomarker or echocardiographic abnormalities

Background

A recent study showed higher high‐sensitivity cardiac troponin I (hs‐cTnI) concentrations in healthy dogs eating grain‐free (GF) compared to those eating grain‐inclusive (GI) diets.

Hypothesis/Objectives

Healthy dogs with subclinical cardiac abnormalities eating GF diets at baseline will show improvements in cardiac biomarkers and echocardiographic variables after diet change, whereas healthy dogs eating GI diets at baseline will not improve.

Animals

Twenty healthy dogs with subclinical cardiac abnormalities (12 Golden Retrievers, 5 Doberman Pinschers, 3 Miniature Schnauzers).

Methods

This prospective study included dogs with increased hs‐cTnI or N‐terminal pro‐B‐type natriuretic peptide (NT‐proBNP) concentrations, or echocardiographic abnormalities. Mixed modeling was used to evaluate echocardiographic, hs‐cTnI, and NT‐proBNP differences between groups (GF or GI diet at baseline) over time (1 y after diet change).

Results

Ten GF and 10 GI dogs were evaluated. There were statistically significant time: group interactions for hs‐cTnI (P = .02) and normalized left ventricular internal systolic diameter (LVIDsN; P = .02), with GF dogs showing larger decreases in these variables than GI dogs. Median (range) hs‐cTnI (ng/mL) for GF dogs was 0.141 (0.012‐0.224) at baseline and 0.092 (0.044‐0.137) at 1 y, and for GI dogs was 0.051 (0.016‐0.195) at baseline and 0.060 (0.022‐0.280) at 1 y. Median LVIDsN for GF dogs was 1.01 (0.70‐1.30) at baseline and 0.87 (0.79‐1.24) at 1 y, and for GI dogs was 1.05 (0.84‐1.21) at baseline and 1.10 (0.85‐1.28) at 1 y.

Conclusions and Clinical Importance

Decreased hs‐cTnI and LVIDsN in GF dogs after diet change supports reversibility of these subclinical myocardial abnormalities.

Association of diet with clinical outcomes in dogs with dilated cardiomyopathy and congestive heart failure

INTRODUCTION

Dilated cardiomyopathy (DCM) in dogs has been associated with feeding of grain-free (GF), legume-rich diets. Some dogs with presumed diet-associated DCM have shown improved myocardial function and clinical outcomes following a change in diet and standard medical therapy.

HYPOTHESIS

Prior GF (pGF) diet influences reverse cardiac remodeling and clinical outcomes in dogs with DCM and congestive heart failure (CHF).

ANIMALS AND METHODS

A retrospective study was performed with 67 dogs with DCM and CHF for which diet history was known. Dogs were grouped by diet into pGF and grain-inclusive (GI) groups. Dogs in the pGF group were included if diet change was a component of therapy. Survival was analyzed using Kaplan-Meier curves and the Cox proportional-hazards model.

RESULTS

The median survival time was 344 days for pGF dogs vs. 253 days for GI dogs (P = 0.074). Statistically significant differences in median survival were identified when the analysis was limited to dogs surviving longer than one week (P = 0.033). Prior GF dogs had a significantly worse outcome the longer a GF diet was fed prior to diagnosis (P = 0.004) or if they were diagnosed at a younger age (P = 0.017). Prior GF dogs showed significantly greater improvement in normalized left ventricular internal diastolic diameter (P = 0.038) and E-point septal separation (P = 0.031) measurements and significant decreases in their furosemide (P = 0.009) and pimobendan (P < 0.005) dosages over time compared to GI dogs.

CONCLUSIONS

Prior GF dogs that survived at least one week after diagnosis of DCM, treatment of CHF, and diet change had better clinical outcomes and showed reverse ventricular remodeling compared to GI dogs.

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.

Effect of type of diet on blood and plasma taurine concentrations, cardiac biomarkers, and echocardiograms in 4 dog breeds

Background

Associations of diet with dilated cardiomyopathy are under investigation.

Objectives

That cardiac assessment would show abnormalities in healthy dogs eating grain‐free (GF) diets or diets with Food and Drug Administration (FDA)‐listed ingredients of concern (peas, lentils, or potatoes) as top 10 ingredients (FDA‐PLP), but not in dogs eating grain‐inclusive (GI) diets or diets without FDA‐listed ingredients of concern (PLP) in the top 10 ingredients (NoFDA‐PLP).

Animals

One hundred eighty‐eight healthy Doberman Pinschers, Golden Retrievers, Miniature Schnauzers, and Whippets.

Methods

This study was an observational cross‐sectional study. Echocardiograms, cardiac biomarkers, and blood and plasma taurine concentrations were compared between dogs eating GF (n = 26) and GI (n = 162) diets, and between FDA‐PLP (n = 39) and NoFDA‐PLP (n = 149) diets, controlling for age and breed. Demographic characteristics, murmurs, genetic status, and ventricular premature complexes (VPCs) during examination were compared between dogs eating different diet types.

Results

No differences in echocardiographic variables, N‐terminal pro‐B‐type natriuretic peptide or whole blood taurine were noted between dogs eating different diet types. Dogs eating GF diets had higher median high‐sensitivity cardiac troponin I (hs‐cTnI) (GF 0.076 ng/mL [Interquartile range (IQR), 0.028‐0.156] vs. GI 0.048 [IQR, 0.0026‐0.080]; P < .001) and higher median plasma taurine (GF 125 nmol/mL [IQR, 101‐148] vs GI 104 [IQR, 86‐123]; P = .02) than dogs eating GI diets. Dogs eating FDA‐PLP diets had higher median hs‐cTnI (0.059 ng/mL [IQR, 0.028‐0.122]) than dogs eating NoFDA‐PLP diets (0.048 [IQR, 0.025‐0.085]; P = .006). A greater proportion of dogs eating FDA‐PLP diets (10%) had VPCs than dogs eating NoFDA‐PLP diets (2%; P = .04).

Conclusions and Clinical Importance

Higher hs‐cTnI in healthy dogs eating GF and FDA‐PLP diets might indicate low‐level cardiomyocyte injury.

Retrospective study of dilated cardiomyopathy in dogs

Background

The United States Food and Drug Administration is investigating possible diet‐associated dilated cardiomyopathy (DCM) in dogs and cats.

Objectives

To retrospectively review DCM cases for signalment, diet information, echocardiographic changes, and survival.

Animals

Client‐owned dogs (n = 71).

Methods

Medical records of dogs diagnosed with DCM between January 1, 2014 and September 30, 2018 were reviewed. Dogs were grouped into “traditional” or “nontraditional” diet categories and whether or not diet was changed after diagnosis.

Results

For dogs eating nontraditional diets, those that had their diets changed had a larger percentage decrease in normalized systolic left ventricular internal dimension (P = .03) and left atrial:aorta ratio (P < .001) compared to those that did not have their diets changed. Survival time was significantly longer for dogs with DCM eating nontraditional diets that had their diets changed (median survival, 337 days; range, 9‐1307 days) compared to dogs eating nontraditional diets that did not have their diets changed (median survival, 215 days; range, 1‐852 days; P = .002).

Conclusions and Clinical Importance

Dogs with DCM eating nontraditional diets can experience improvement in cardiac function after diet change but additional research is needed to examine possible associations between diet and DCM.

Molecular Characterisation of Canine Osteosarcoma in High Risk Breeds

Dogs develop osteosarcoma (OSA) and the disease process closely resembles that of human OSA. OSA has a poor prognosis in both species and disease-free intervals and cure rates have not improved in recent years. Gene expression in canine OSAs was compared with non-tumor tissue utilising RNA sequencing, validated by qRT-PCR and immunohistochemistry (n = 16). Polymorphic polyglutamine (polyQ) tracts in the androgen receptor (AR/NR3C4) and nuclear receptor coactivator 3 (NCOA3) genes were investigated in control and OSA patients using polymerase chain reaction (PCR), Sanger sequencing and fragment analysis (n = 1019 Rottweilers, 379 Irish Wolfhounds). Our analysis identified 1281 significantly differentially expressed genes (>2 fold change, p < 0.05), specifically 839 lower and 442 elevated gene expression in osteosarcoma (n = 3) samples relative to non-malignant (n = 4) bone. Enriched pathways and gene ontologies were identified, which provide insight into the molecular pathways implicated in canine OSA. Expression of a subset of these genes (SLC2A1, DKK3, MMP3, POSTN, RBP4, ASPN) was validated by qRTPCR and immunohistochemistry (MMP3, DKK3, SLC2A1) respectively. While little variation was found in the NCOA3 polyQ tract, greater variation was present in both polyQ tracts in the AR, but no significant associations in length were made with OSA. The data provides novel insights into the molecular mechanisms of OSA in high risk breeds. This knowledge may inform development of new prevention strategies and treatments for OSA in dogs and supports utilising spontaneous OSA in dogs to improve understanding of the disease in people.

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.

Development of plasma and whole blood taurine reference ranges and identification of dietary features associated with taurine deficiency and dilated cardiomyopathy in golden retrievers: A prospective, observational study

INTRODUCTION

A surge in Food and Drug Administration (FDA) consumer complaints identified concerns that legume-rich, grain-free diets were associated with nutritionally-mediated dilated cardiomyopathy (DCM). Golden retrievers represent the most reported breed affected by this condition and previous studies documented the disease is responsive to dietary change and taurine supplementation. Although dietary findings across cases are compelling, prospective studies with control groups are lacking. The role of diet in developing taurine deficiency and echocardiographic changes consistent with DCM in healthy dogs is unknown.

OBJECTIVES

We hypothesized that golden retrievers eating non-traditional diets are at a higher risk of having taurine deficiency and nutritionally-mediated DCM compared with those eating traditional commercial diets. We aimed to compare taurine concentrations and echocardiographic indices of systolic function between golden retrievers in each diet group and elucidate associations between diet and these variables. Additionally, we aimed to generate breed-specific reference intervals for whole blood and plasma taurine concentrations.

ANIMALS

86 golden retrievers.

METHODS

Golden retrievers eating traditional or non-traditional diets were evaluated and diet history, taurine concentrations and echocardiographic data were collected. Dietary features, taurine concentrations and echocardiographic findings were compared between diet groups. Relative risks were calculated for the likelihood of echocardiographic abnormalities and taurine deficiency in each diet group. Breed-specific reference intervals were constructed for taurine concentrations in dogs from the traditional diet group.

RESULTS

Golden retrievers eating non-traditional diets had significantly lower taurine concentrations and more frequent systolic dysfunction. Breed specific reference intervals are higher than previously reported across breeds.

CONCLUSIONS

Non-traditional diets, which were typically grain-free and contained legumes in this study, were significantly associated with and have increased relative risk for the identification of taurine deficiency and echocardiographic abnormalities consistent with nutritionally-mediated DCM. These findings were identifiable in the absence of clinical signs and support the findings of multiple previous studies and the ongoing FDA investigation.

Echocardiographic and electrocardiographic evaluation of North American Irish Wolfhounds

Background

Cardiac disease is an important cause of morbidity and mortality in Irish Wolfhounds (IWs), but its prevalence and clinical characteristics in North American IWs are incompletely described.

Hypothesis/Objectives

That atrial fibrillation (AF) is a diagnostic marker of echocardiographic abnormalities, and that clinical characteristics predict development of IW cardiomyopathy (IWCM). To define the prevalence of arrhythmias and echocardiographic abnormalities in North American IWs.

Animals

Six hundred and forty‐five adult IWs presented for screening examinations intended to identify familial cardiac disease.

Methods

In this retrospective cohort study, reference intervals defined based on echocardiographic data from IW classified as normal, were used to define the prevalence of structural and functional abnormalities. A logistic model was developed to identify clinical findings that predict future development of IWCM.

Results

The prevalence of AF was 8.9% (95% confidence interval [CI], 6.6‐11.2) of which 55.5% had echocardiographic abnormalities. IWCM defined by left atrial enlargement, left ventricular dilatation, and systolic dysfunction had a prevalence of 1.8% (0.72‐2.8). Positive and negative likelihood ratios for AF in the identification of IWCM were, respectively, 10.8 (7.29‐16) and 0.2 (0.06‐0.69). Multivariable logistic regression identified AF (odds ratio [OR]; 10.6, 95% CI, 2.67‐42.3) and male sex (OR; 3.8, 95% CI, 1.02‐14) as predictors of future development of IWCM.

Conclusions and Clinical Importance

Atrial fibrillation is common in North American IW. It occurs in association with structural cardiac disease but also in its absence. Irish Wolfhounds cardiomyopathy is characterized by chamber enlargement but minimally decreased ejection phase indices of myocardial function. Atrial fibrillation is a risk factor for future development of IWCM.

Pedigree analysis of atrial fibrillation in Irish wolfhounds supports a high heritability with a dominant mode of inheritance

Background

Atrial fibrillation (AF) is the most common arrhythmia in dogs. The Irish Wolfhound breed has a high prevalence of AF making them an ideal breed to investigate possible genetic contributions to this disease. The aim of this study was to perform a heritability analysis in North American Irish Wolfhounds using phenotype data from cardiac screenings performed between 2000 and 2019 in order to determine how much of this disease can be attributed to genetics compared to environmental causes. The second aim was to determine the disease mode of inheritance to help inform prevention and breeding practices.

Results

There were 327 Irish Wolfhounds diagnosed with AF and 136 Irish Wolfhounds over 8 years of age without AF. The estimated mean (95% confidence interval) heritability of AF in Irish Wolfhounds was 0.69 (0.50–0.86). The pedigree was consistent with a dominant mode of inheritance.

Conclusion

Results of this study indicate a strong genetic contribution to AF in Irish Wolfhounds and suggest that future research to identify causative genetic mutations is warranted.

Irish wolfhounds with subclinical atrial fibrillation: progression of disease and causes of death

INTRODUCTION

To evaluate the frequency of dilated cardiomyopathy (DCM) and cardiac death (CD) in Irish wolfhounds (IW) with subclinical atrial fibrillation (AF) and to compare cardiac and all-cause mortality to those of a contemporaneous control group of apparently healthy IW with sinus rhythm.

ANIMALS

Fifty-two IW with AF, but without echocardiographic evidence of DCM or other cardiac disease, and an age- and gender-matched control cohort of 52 apparently healthy IW.

METHODS

Data from 1552 IW were retrospectively evaluated. Fifty-two dogs with subclinical AF were compared with 52 IW controls. Time from initial diagnosis to development of DCM was recorded, and survival data were analyzed using cumulative incidence functions.

RESULTS

26/52 AF dogs developed DCM. At study end, in the AF and control group each, 49/52 AF dogs had died, three remained alive. Death in the AF cohort was attributed to CD in 22/49 dogs (12 congestive heart failure [CHF], 10 sudden cardiac deaths [SCD]), while 27 dogs died from non-CD. In the control group, significantly fewer dogs developed DCM (11/52 dogs, p=0.004), even fewer died from CD (5/49; three CHF, two SCD; p=0.001). The odd ratios (95% confidence interval) for dogs with AF vs. controls to develop DCM was 3.7 (1.6-8.8) and to die from CD was 7.2 (2.4-21.2). Median all-cause survival for AF IWs (CD, 36.3 months; non-CD, 33.2 months) did not differ significantly from the control group (CD, 28.6 months, p=0.377; non-CD, 45.3 months, p=0.631).

CONCLUSION

IW with subclinical AF commonly develop DCM and die from cardiac death.

Dilated cardiomyopathy in 151 Irish Wolfhounds: Characteristic clinical findings, life expectancy and causes of death

Dilated cardiomyopathy (DCM) is an important cause of morbidity in Irish Wolfhounds (IW), a breed also predisposed to neoplastic and orthopedic diseases that shorten life expectancy. The objective of this study was to investigate survival and causes of death in IW with DCM and to characterise the clinical findings of DCM over time. Data from cardiovascular examinations performed in 1591 IW, including echocardiography and electrocardiography, were retrospectively evaluated. IW with DCM on medical therapy with long term longitudinal follow-up were included in this study (n=151; 95 males, 56 females). Based on their clinical status at initial diagnosis, IW were classified into one of three groups: preclinical DCM with sinus rhythm (PC-DCM-SR, n=35), preclinical DCM with atrial fibrillation (PC-DCM-AF, n=87), and congestive heart failure with DCM and AF (CHF-DCM-AF, n=29). Survival data were analyzed using cumulative incidence functions, Kaplan-Meier and Cox regression. CHF was predominantly characterized by chylous pleural and mild pericardial effusions. Causes of death were cardiac (CD) in 73/151 and non-cardiac (non-CD) in 62/151; 16 dogs remained alive at study end. The majority of deaths in both preclinical DCM groups were non-CD (PC-DCM-AF=51.9% non-CD, 48.1% CD; PC-DCM-SR, 65.5% non-CD, 34.5% CD). In the CHF-DCM-AF group most dogs (89.6%) experienced a CD. Median survival of the CHF-DCM-AF group (7.3 months) was significantly shorter than in the PC-DCM-AF group (21.9 months) or PC-DCM-SR group (29.1 months, P=0.001). CHF-DCM-AF in IW was associated with reduced life expectancy and CD, while most IW with preclinical DCM died from non-cardiac causes.

Echocardiographic phenotype of canine dilated cardiomyopathy differs based on diet type

INTRODUCTION

Canine dilated cardiomyopathy (DCM) can result from numerous etiologies including genetic mutations, infections, toxins, and nutritional imbalances. This study sought to characterize differences in echocardiographic findings between dogs with DCM fed grain-free (GF) diets and grain-based (GB) diets.

ANIMALS

Forty-eight dogs with DCM and known diet history.

METHODS

This was a retrospective analysis of dogs with DCM from January 1, 2015 to May 1, 2018 with a known diet history. Dogs were grouped by diet (GF and GB), and the GF group was further divided into dogs eating the most common grain-free diet (GF-1) and other grain-free diets (GF-o). Demographics, diet history, echocardiographic parameters, taurine concentrations, and vertebral heart scale were compared between GB, all GF, GF-1, and GF-o groups at diagnosis and recheck.

RESULTS

Dogs eating GF-1 weighed less than GB and GF-o dogs, but age and sex were not different between groups. Left ventricular size in diastole and systole was greater, and sphericity index was less for GF-1 compared with GB dogs. Diastolic left ventricular size was greater for all GF compared with that of GB dogs. Fractional shortening, left atrial size, and vertebral heart scale were not different between groups. Taurine deficiency was not identified in GF dogs, and presence of congestive heart failure was not different between groups. Seven dogs that were reevaluated after diet change (6 received taurine supplementation) had clinical and echocardiographic improvement.

CONCLUSIONS

Dietary-associated DCM occurs with some GF diets and can improve with nutritional management, including diet change. The role of taurine supplementation, even without deficiency, is uncertain.

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.

Echocardiographic indices of age- and gender-dependent cardiac remodeling over the adult lifespan in Irish Wolfhounds

INTRODUCTION

Characterizing age- and gender-dependent cardiac remodeling over the adult lifespan in Irish Wolfhounds (IWs) by echocardiography. In people, a life-long cardiac remodeling process has been demonstrated.

ANIMALS, MATERIALS, METHODS

Irish Wolfhounds (56 males, 90 females) with no indication of cardiac disease at final assessment (>7.0 years old). For each dog, four transthoracic echocardiographic studies were analyzed. Left ventricular (LV) systolic and diastolic internal dimensions (LVIDs, LVIDd), LV fractional shortening (FS) and ejection fraction (EF), LV free wall and interventricular septal thickness, right ventricular diastolic dimension, and left atrial (LA) and right atrial systolic diameters were compared at time points in the following age categories (years): 1.0-2.5; 3.0-4.0; 4.5-6.0; and 7.0-10.5 and related to age, body weight, and heart rate.

RESULTS

Over the adult life course, males had statistically significant increases in LV internal dimensions, atrial diameters, and decreases of FS and EF. From youngest to oldest age of examination means ± standard deviations were as follows: LVIDs, 32.7 ± 2.9 vs. 36.5 ± 2.9 mm; LVIDd, 49.6 ± 4.7 vs. 53.4 ± 3.8 mm; right atrial diameter, 36.8 ± 3.3 vs. 42.6 ± 3.3 mm; LA, 49.0 ± 3.6 vs. 55.0 ± 3.7 mm; and FS, 34.6 ± 3.7 vs. 31.0 ± 3.2. In females, LV internal dimensions did not change significantly, increases in right atrial (38.1 ± 3.7 mm to 40.0 ± 5.2 mm) and LA diameter (48.8 ± 3.6 to 52.4 ± 4.3 mm) were attenuated, as were decreases of FS (33.4 ± 3.7 to 31.5 ± 4.4, p = 0.02). LV wall thicknesses did not significantly change in both genders.

DISCUSSION AND CONCLUSIONS

Over the adult life course, echocardiography demonstrated increasing LV dimensions in male IWs only. In both genders, FS and EF decreased, and atrial diameters increased. Females showed an attenuated remodeling process.

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.

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 Species Comparison of Cardiac Troponin T and Dystrophin: Unravelling the DNA behind Dilated Cardiomyopathy

Animals have frequently been used as models for human disorders and mutations. Following advances in genetic testing and treatment options, and the decreasing cost of these technologies in the clinic, mutations in both companion and commercial animals are now being investigated. A recent review highlighted the genes associated with both human and non-human dilated cardiomyopathy. Cardiac troponin T and dystrophin were observed to be associated with both human and turkey (troponin T) and canine (dystrophin) dilated cardiomyopathies. This review gives an overview of the work carried out in cardiac troponin T and dystrophin to date in both human and animal dilated cardiomyopathy.

Genomic Insights into Cardiomyopathies: A Comparative Cross-Species Review

In the global human population, the leading cause of non-communicable death is cardiovascular disease. It is predicted that by 2030, deaths attributable to cardiovascular disease will have risen to over 20 million per year. This review compares the cardiomyopathies in both human and non-human animals and identifies the genetic associations for each disorder in each species/taxonomic group. Despite differences between species, advances in human medicine can be gained by utilising animal models of cardiac disease; likewise, gains can be made in animal medicine from human genomic insights. Advances could include undertaking regular clinical checks in individuals susceptible to cardiomyopathy, genetic testing prior to breeding, and careful administration of breeding programmes (in non-human animals), further development of treatment regimes, and drugs and diagnostic techniques.