A case of juvenile form of dilated cardiomyopathy in a 6-month-old Shiba Inu dog

A 6-month-old Shiba Inu dog was brought to the Veterinary Medical Teaching Hospital because of a cough, exercise intolerance, and pulmonary edema. The dog had a Levine 2/6 systolic murmur. Transthoracic echocardiography revealed left atrial and ventricular dilatation (left atrium to aortic ratio: 2.8), mitral and tricuspid valve regurgitation, and severe left ventricular myocardial hypokinesia (fractional shortening was 11.8%). Bubble contrast echocardiography did not reveal a congenital shunt; therefore, the dog was clinically diagnosed with early onset dilated cardiomyopathy. From the first visit, the dog was treated with pimobendan, taurine, torasemide, and isosorbide dinitrate. After 435 days, echocardiography revealed that systolic function had not improved. On Day 465, atrial fibrillation was confirmed via electrocardiogram, and treatment with diltiazem hydrochloride was initiated. The dog continued to appear clinically stable thereafter, until it died suddenly 1087 days after the initial visit. A postmortem histopathological examination identified severe enlargement of the left atrial and ventricular chambers as well as attenuated wavy fibers in the ventricular myocardium, which confirmed dilated cardiomyopathy in a juvenile. This is the first report of a juvenile form of dilated cardiomyopathy in a Shiba Inu dog. This case report provides evidence that the extended prognosis of this dog differed from that in previously reported cases of dilated cardiomyopathy in young dogs.Key clinical message:This is the first reported case of a juvenile form of dilated cardiomyopathy in a Shiba Inu dog. This report provides evidence that the prognosis of this dog differed from that in previously reported cases of dilated cardiomyopathy in young dogs.     

Anthracycline-induced cardiomyopathy in a dog treated with epirubicin

An 8-year-old American cocker spaniel dog was diagnosed with dilated cardiomyopathy. Four years earlier, the dog had been diagnosed with multicentric lymphoma and had received 4 cycles of multi-agent chemotherapy, including doxorubicin and epirubicin. The total cumulative dose of epirubicin was 168 mg/m². Dilated cardiomyopathy was considered a consequence of epirubicin toxicity.     

Ventricular systolic dysfunction in dogs diagnosed with hypoadrenocorticism

In human patients with hypoadrenocorticism, a secondary dilated cardiomyopathy is noted that has been reported to resolve with replacement steroid therapy. A similar secondary dilated cardiomyopathy in dogs with hypoadrenocorticism has not been previously described. We present three dogs concurrently diagnosed with hypoadrenocorticism and ventricular dilation with systolic dysfunction. Two dogs were presented with clinical signs consistent with biventricular congestive heart failure and a third dog was presented with signs of acute hypoadrenocorticism without congestive heart failure. All dogs recovered to normal cardiac size and function with therapy. Hypoadrenocorticism should be considered as a differential diagnosis in dogs that present with ventricular dilation and systolic dysfunction if there are other indicators in the clinical and laboratory testing. Additionally, a thorough cardiac evaluation should be recommended for dogs that are found to have a heart murmur at the time of diagnosis of hypoadrenocorticism.     

Congestive cardiomyopathy in a dog associated with pregnancy

A two-year-old, six-week postpartum female dog was presented with acute congestive heart failure for treatment. The patient collapsed and suddenly died. Postmortem examination revealed an enlarged, dilated heart with thin ventricular walls. Histologically, scattered multifocal areas of myocardial degeneration and necrosis with fibrosis were seen in the myocardium. This case of acute cardiomyopathy in a female dog six weeks postpartum is similar to the well-described, postpartum cardiomyopathy in man. The etiology of this case was not ascertained.     

Radiofrequency Catheter Ablation of Atrioventricular Accessory Pathways in 3 Dogs with Subsequent Resolution of Tachycardia-Induced Cardiomyopathy

Incessant supraventricular tachyarrhythmias are known to result in myocardial dysfunction indistinguishable from idiopathic dilated cardiomyopathy by current testing methods. This tachycardia-induced cardiomyopathy (TICM), however, is uniquely reversible with adequate rhythm control. Two dogs were presented to The Ohio State University for incessant supraventricular tachycardia (SVT) and echocardiographic signs of dilated cardiomyopathy, later proven to be TICM. A 3rd dog presented for frequent paroxysms of SVT and syncope had echocardiographic signs of mild myocardial systolic dysfunction. All 3 dogs had inadequate rhythm control with multiple antiarrhythmic agents, and 1 dog suffered from recurrent left-sided congestive heart failure. Generalized cardiomegaly was found in 1 dog and left-sided dilatation without concurrent right-sided enlargement in 1 dog. Mild-to-severe left ventricular systolic dysfunction was confirmed echocardiographically in all dogs. A total of 4 atrioventricular accessory pathways (APs) were found during invasive electrophysiologic studies in these 3 dogs. All APs were successfully ablated with radiofrequency energy delivered through a thermistor-tipped catheter. Elimination of AP conduction, and thus orthodromic atrioventricular reciprocating tachycardia, resulted in resolution of all clinical and echocardiographic evidence of TICM in these dogs. This result confirms that the cardiomyopathy was, in fact, reversible TICM. All cardiovascular medications were discontinued, and no complications occurred during a 15-25-month follow-up period.     

Treatment of severe chronic digoxin toxicosis in a dog with cardiac disease, using ovine digoxin-specific immunoglobulin G Fab fragments

Severe digoxin toxicosis in a 13-year-old mixed-breed dog with dilated cardiomyopathy was successfully treated with i.v. administration of ovine digoxin-specific IgG Fab fragments. Management of this dog following treatment with Fab fragments was complicated by hypomagnesemia and loss of the positive inotropic effect of digoxin.     

Surgical correction of subvalvular aortic stenosis using cardiopulmonary bypass in a dog

A three-month-old male Golden Retriever had symptoms including exercise intolerance, dyspnea and syncope and was diagnosed with subvalvular aortic stenosis. Cardiac catheterization revealed a left ventricular-aortic systolic pressure gradient of 90 mm Hg. Surgical correction of the condition was achieved using cardiopulmonary bypass. The subvalvular fibrous lesion was resected through an aortotomy. The stenosis was dilated from 8.5 mm to 12.0 mm in diameter. Postoperatively the dog was asymptomatic. Seven months after surgery, the pressure gradient decreased to 44 mm Hg. However, after another three months, the dog died suddenly without any premonitory signs. Postmortem examination revealed that pathologic changes caused by increased left ventricular pressure overload were not severe.     

Tachycardia-induced cardiomyopathy in a young Boxer dog with supraventricular tachycardia due to an accessory pathway

A 1-year-old male Boxer dog presented with sustained supraventricular tachycardia and tachycardia-induced cardiomyopathy. Conversion to sinus rhythm was achieved initially with intravenous lignocaine and subsequently with oral procainamide. Oral procainamide treatment was relatively successful in maintaining normal sinus rhythm with no side effects apart from a reversible change in coat colour. Electrophysiological studies demonstrated the presence of an accessory pathway connecting the right atrium to the right ventricle and confirmed the diagnosis of orthodromic atrioventricular reciprocating tachycardia. Radiofrequency catheter ablation of the accessory pathway led to permanent resolution of the supraventricular tachycardia and for 9.5 years the dog has had no further signs of cardiac disease. The successful treatment of this condition highlights the importance of differentiating tachycardia-induced cardiomyopathy from dilated cardiomyopathy.     

Use of western immunoblot for evaluation of myocardial dystrophin, alpha-sarcoglycan, and beta-dystroglycan in dogs with idiopathic dilated cardiomyopathy

OBJECTIVE: To evaluate the potential importance of dystrophin, alpha-sarcoglycan (adhalin), and beta-dystroglycan, by use of western blot analysis, in several breeds of dogs with dilated cardiomyopathy. SAMPLE POPULATION: Myocardial samples obtained from 12 dogs were evaluated, including tissues from 7 dogs affected with dilated cardiomyopathy, 4 control dogs with no identifiable heart disease (positive control), and 1 dog affected with Duchenne muscular dystrophy (negative control for dystrophin). Of the affected dogs, 4 breeds were represented (Doberman Pinscher, Dalmatian, Bullmastiff, and Irish Wolfhound). PROCEDURE: Western blot analysis was used for evaluation of myocardial samples obtained from dogs with and without dilated cardiomyopathy for the presence of dystrophin and 2 of its associated glycoproteins, alpha-sarcoglycan and beta-dystroglycan. RESULTS: Detectable differences were not identified between dogs with and without myocardial disease in any of the proteins evaluated. CONCLUSIONS AND CLINICAL RELEVANCE: Abnormalities in dystrophin, alpha-sarcoglycan, and beta-dystroglycan proteins were not associated with the development of dilated cardiomyopathy in the dogs evaluated in this study. In humans, the development of molecular biological techniques has allowed for the identification of specific causes of dilated cardiomyopathy that were once considered to be idiopathic. The use of similar techniques in veterinary medicine may aid in the identification of the cause of idiopathic dilated cardiomyopathy in dogs, and may offer new avenues for therapeutic intervention.     

A possible predisposition to dilated cardiomyopathy in Huntaway dogs

AIM: To compare the prevalence of dilated cardiomyopathy (DCM) in New Zealand Huntaway dogs with the prevalence of DCM in other breeds of dog. METHODS: The necropsy database at Massey University was used to identify cases of DCM diagnosed between January 1999 and March 2006. Dogs were considered to have DCM if echocardiographic, gross necropsy, or histological findings were consistent with this diagnosis. The prevalence in Huntaways was then compared with the prevalence observed in all breeds of dog, as well as the prevalence observed in large breeds of dog. RESULTS: Twelve dogs were identified with DCM. One was diagnosed using echocardiography, while the other 11 were diagnosed by gross necropsy examination. The gross diagnosis of DCM was confirmed histologically in 6/11 dogs. The prevalence of DCM in Huntaways was significantly higher than the prevalence seen in all breeds of dog (p=0.008), and the prevalence in large breeds of dog (p=0.025). All four Huntaways diagnosed with DCM were male, and had an average age of 4 years. Three dogs presented with symptoms attributable to impaired heart function while one presented with symptoms of chronic renal failure. The duration of clinical symptoms prior to presentation ranged between 1 day and 3 weeks. CONCLUSIONS: The results of this study suggest that Huntaways may be predisposed to the development of DCM. Although the increased prevalence in this breed was significant, only small numbers of affected Huntaways were identified, and additional cases are required to confirm these preliminary findings. CLINICAL RELEVANCE: Huntaways are the most common working dog in New Zealand. The premature loss of a working dog is expected to have a significant economic impact on farmers. Further investigation of DCM in Huntaways may allow measures to reduce the prevalence in this breed.     

Boxer dog cardiomyopathy: an update.

Boxer dog cardiomyopathy is an inheritable form of myocardial disease characterized most commonly by ventricular tachycardias, syncope, and, sometimes, systolic dysfunction and heart failure. Careful evaluation of boxer dog cardiomyopathy by several investigators has demonstrated that the disease may be best classified as arrhythmogenic right ventricular cardiomyopathy. Affected dogs have a variable prognosis; although some succumb to sudden cardiac death, many can remain asymptomatic or be successfully managed on antiarrhythmics for years.     

A possible predisposition to dilated cardiomyopathy in Huntaway dogs

AIM: To compare the prevalence of dilated cardiomyopathy (DCM) in New Zealand Huntaway dogs with the prevalence of DCM in other breeds of dog.

METHODS: The necropsy database at Massey University was used to identify cases of DCM diagnosed between January 1999 and March 2006. Dogs were considered to have DCM if echocardiographic, gross necropsy, or histological findings were consistent with this diagnosis. The prevalence in Huntaways was then compared with the prevalence observed in all breeds of dog, as well as the prevalence observed in large breeds of dog.

RESULTS: Twelve dogs were identified with DCM. One was diagnosed using echocardiography, while the other 11 were diagnosed by gross necropsy examination. The gross diagnosis of DCM was confirmed histologically in 6/11 dogs. The prevalence of DCM in Huntaways was significantly higher than the prevalence seen in all breeds of dog (p=0.008), and the prevalence in large breeds of dog (p=0.025). All four Huntaways diagnosed with DCM were male, and had an average age of 4 years. Three dogs presented with symptoms attributable to impaired heart function while one presented with symptoms of chronic renal failure. The duration of clinical symptoms prior to presentation ranged between 1 day and 3 weeks.

CONCLUSIONS: The results of this study suggest that Huntaways may be predisposed to the development of DCM. Although the increased prevalence in this breed was significant, only small numbers of affected Huntaways were identified, and additional cases are required to confirm these preliminary findings.

CLINICAL RELEVANCE: Huntaways are the most common working dog in New Zealand. The premature loss of a working dog is expected to have a significant economic impact on farmers. Further investigation of DCM in Huntaways may allow measures to reduce the prevalence in this breed.     

Association between results of ambulatory electrocardiography and development of cardiomyopathy during long-term follow-up of Doberman pinschers

OBJECTIVE: To characterize ambulatory electrocardiographic results of overtly healthy Doberman Pinschers and determine associations between those results and development of dilated cardiomyopathy. DESIGN: Cohort study. ANIMALS: 114 (58 male, 56 female) overtly healthy Doberman Pinschers without echocardiographic evidence of cardiac disease on initial examination. PROCEDURE: Echocardiograms and 24-hour ambulatory electrocardiograms (Holter recordings) were obtained initially and at variable intervals. The status (live vs dead) of all dogs was known at least 2 years and as long as 10 years after initial examination (mean [+/- SD] follow-up time, 4.33 +/- 1.84 years). Associations between development of dilated cardiomyopathy and number of ventricular premature contractions (VPC), age, and sex were determined. RESULTS: 55 dogs (48%) did not have VPC on initial Holter recordings, and only 8 dogs had > 50 VPC/24 hours. The likelihood that a dog would have VPC was associated with increasing age and being male. At least 1 VPC/24 hours, and in particular, > 50 VPC/24 hours or > or = 1 couplet or triplet of VPC/24 hours, were predictive of subsequent development of dilated cardiomyopathy. Fifty-four dogs (47%) developed dilated cardiomyopathy; 12 were still alive at the end of the study, and 42 had died. Twenty-five of these 42 dogs died after the onset of congestive heart failure (CHF), 15 died suddenly before the onset of overt CHF, and 2 died of noncardiac causes. More males developed dilated cardiomyopathy than females, and dogs that died suddenly were approximately 1 year younger than those that developed CHF. CONCLUSIONS AND CLINICAL RELEVANCE: Results of high-quality Holter recordings may be used to identify overtly healthy Doberman Pinschers that are at a high risk for dilated cardiomyopathy.     

Bartonella-associated inflammatory cardiomyopathy in a dog

A 6-year-old, male, mongrel dog was presented for acute onset of dyspnea and cough. At admission, the dog was cachectic and severely depressed. The electrocardiogram showed a sinus rhythm conducted with left bundle truncular branch block and interrupted by frequent multiform ventricular ectopic beats organized in allorhythmias. Thoracic radiographs revealed a marked cardiomegaly with perihilar edema, whereas transthoracic echocardiography revealed a dilated cardiomyopathy with segmental dyskinesis. Furosemide, enalapril, pimobendan, and mexiletine were prescribed, and a Holter was scheduled after resolution of congestive heart failure. Three days later, the dog died suddenly during sleep. Histopathology revealed diffuse myocyte hypertrophy with multifocal hemorrhages, alternating to areas of severe replacement fibrosis and lymphoplasmocytic infiltrates. Immunohystochemistry stains were strongly positive for T-lymphocyte infiltration (CD3) and weakly positive for B-lymphocytes (CD79). Polymerase chain reaction was positive for Bartonella spp. Based on these results, a post-mortem diagnosis of bacterial inflammatory cardiomyopathy was made.     

Lymphocyte beta -adrenoceptor downregulation in great danes with occult dilated cardiomyopathy (DCM) and with DCM and heart failure.

The importance of the adrenergic nervous system in supporting the failing heart has long been known. The adrenergic drive on cardiac structure and function has however some adverse effects, which include myocardial beta-adrenoceptor (beta-AR) downregulation and decreased beta-adrenergic responsiveness to cathecolamines. In dog lymphocytes, beta(1)-AR and beta(2)-AR populations are almost equally represented (with a slight prevalence of beta(2)) and a significant correlation between cardiac and lymphocytic adrenoceptors has been found. The aim of the present study was to investigate possible differences between the concentration of lymphocytic beta-AR in healthy dogs, dogs with dilated cardiomyopathy (DCM) and dogs with occult DCM. Three groups of great danes were considered: a control group (n =10), dogs with DCM (n =9) and dogs with occult DCM (n =4). Lymphocytic beta-AR populations were determined in all dogs. A substantial and significant decrease (P<0.05) in total-AR, beta(1)-AR and beta(2)-AR concentrations in the lymphocytes of dogs with symptomatic DCM and occult DCM compared to the control group was found. Although the mean value of the lymphocyte beta(1)-AR number in the asymptomatic group was double compared to the DCM group, this difference was not statistically significant. We conclude that in dogs beta-AR downregulation occurs early in the course of dilated cardiomyopathy. This finding may suggest the value of early use of a beta-blocker in the therapeutic regimen. Moreover, the continuous monitoring of lymphocytic beta-AR may represent a useful tool for the development of a more effective individual therapy.     

Isolation of methicillin-resistant Staphylococcus lugdunensis in a dog with endocarditis

A 4-year-old male castrated Borzoi dog presented on referral for evaluation of pleural effusion, ventricular arrhythmias, and suspected dilated cardiomyopathy. Echocardiogram identified several masses along the chordae tendineae, as well as a long the annulus of the mitral valve. A blood culture was positive for methicillin resistant Staphylococcus lugdunensis. The dog was also positive for Bartonella DNA on PCR testing. Aggressive antibiotic therapy was instituted. However, the dog continued to have recurrent pleural effusion and progressive azotemia. The dog was euthanized 39 days after diagnosis. Necropsy confirmed the presence of intracardiac abscesses, thrombosis and endocarditis. S. lugdunensis is a recently identified rare cause of endocarditis in humans characterized by intracardiac abscess formation, highly destructive valvular lesions preferentially affecting the mitral valve and a high mortality rate. This is the first reported case of S. lugdunensis isolation in a dog with endocarditis.     

Transvenous electrical cardioversion of atrial fibrillation in two dogs

Atrial fibrillation is characterized by uncoordinated electrical activation of the atria that leads to the loss of atrial mechanical function and atrial fibrosis as a substrate promoting maintenance of rhythm abnormality. Transvenous electrical cardioversion has not been previously reported in the dog. The authors demonstrate the use of this technique for successful cardioversion of atrial fibrillation in two dogs with dilated cardiomyopathy.     

Syncope secondary to transient atrioventricular block in a German shepherd dog with dilated cardiomyopathy and atrial fibrillation

This case report describes transient atrioventricular block as the etiology for syncopal events in a 6-year-old male German shepherd dog with atrial fibrillation and dilated cardiomyopathy. The arrhythmia diagnosis was obtained via Holter monitoring. Medical treatment with a sustained-release preparation of theophylline, as an additive to the standard congestive heart failure treatment (benazepril, furosemide and pimobendan) may have contributed to temporary remission of the syncopal events. However, the congestive heart failure progressed and the dog was euthanized. Veterinarians should be aware of the possibility of transient atrioventricular block causing syncope in dogs with DCM and AF and should be careful in empirically lowering the ventricular response rate if these dogs present with syncopal episodes.     

Cardioversion of supraventricular tachycardia using lidocaine in five dogs

Sustained supraventricular tachycardia (SVT) may lead to life-threatening complications such as tachycardia-induced myocardial failure. We report the use of intravenous lidocaine in 5 dogs with SVT. Two dogs had evidence of an accessory conduction pathway, 2 were suspected of having an accessory pathway, and the mechanism of SVT was unknown in the remaining dog, which subsequently developed dilated cardiomyopathy 2 years later. In all cases there was rapid conversion to normal sinus rhythm, which was then maintained with oral mexilitene (4 dogs) or mexilitene combined with propranolol (1 dog).     

Idiopathic dilated cardiomyopathy: Advances in aetiology, pathogenesis and management

In most cases of dilated cardiomyopathy in the dog (and in man) the aetiology is unknown; these cases are designated idiopathic. Recent advances, particularly in the field of molecular biology, are providing a better understanding of the natural history of the disease and are shedding light on possible primary causes of dilated cardiomyopathy as well as some of the factors which may be responsible for the progressive nature of the disease process. Armed with this information, more specific therapeutic regimes can be developed with the aim of stopping or reversing myocardial damage. The use of skeletal muscle to assist the failing myocardium may offer a practical means of improving a patient's cardiovascular status, particularly in cases where conventional medical therapy is failing to control the progression of the clinical signs.