Arrhythmogenic right ventricular cardiomyopathy in a dog

An 8-month-old Labrador retriever bitch was evaluated for sudden-onset, progressive abdominal distension. Physical examination revealed an exaggerated inspiratory effort, severe ascites, bilateral jugular vein distension, and hypokinetic femoral arterial pulses. Thoracic auscultation detected tachycardia with muffled heart sounds, without audible cardiac murmurs. Thoracic radiographs identified severe right ventricular enlargement and pleural effusion. The electrocardiogram was consistent with incomplete right bundle branch block or right ventricular enlargement. Echocardiography demonstrated severe right ventricular and atrial dilation, secondary tricuspid regurgitation, and thinning and hypocontractility of the right ventricular myocardium. Left heart chamber sizes were slightly decreased, with normal left ventricular contractility. A diagnosis of arrhythmogenic right ventricular cardiomyopathy was reached, based on the characteristic clinical, electrocardiographic, radiographic and echocardiographic findings, and the exclusion of other causes of isolated right ventricular failure. Treatment effected good control of clinical signs, until acutely decompensated congestive right heart failure led to euthanasia after 4 months. Arrhythmogenic right ventricular cardiomyopathy is a well-described clinical entity in humans, and has previously been documented in 3 male dogs. The condition is characterised by progressive fibro-adipose replacement of right ventricular myocardium, while the left ventricle usually remains unaffected. It should be considered a differential diagnosis in any young dog presented with isolated right heart failure, syncope, or unexplained ventricular tachyarrhythmias. This article reports the 1st case of arrhythmogenic right ventricular cardiomyopathy in a female dog, and highlights its echocardiographic features.     

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.     

Echocardiographic and clinical signs of canine dilated cardiomyopathy

The clinical signs, electrocardiograms and echocardiograms of 12 dogs with dilated cardiomyopathy of large breeds and congestive heart failure were reviewed. There was a high prevalence of males (11 dogs) and of the Doberman breed (7 dogs). Seven dogs had atrial fibrillation. The echocardiograms revealed significant increases in left ventricular and left atrial dimensions. The shortening fraction (%ΔD), aortic root excursion and left ventricular wall excursion were all significantly decreased, documenting a decrease in contractile function of the left ventricle that, together with the cardiac enlargement characterize this disease. The advantages of obtaining these functional parameters non-invasively are emphasized.     

Echocardiographic evaluation of diastolic parameters in dogs with dilated cardiomyopathy

Echocardiography is a valuable tool for the evaluation of systolic and diastolic cardiac function. A high correlation between measurements of diastolic mitral inflow parameters analyzed with Doppler echocardiography and invasive methods makes the former valuable. The aim of this study was to ascertain if significant differences occur in diastolic myocardial parameters between dogs with no heart disease and dogs with subclinical or clinical dilated cardiomyopathy. Furthermore the aim of the study was to determine whether heart failure in dilated cardiomypathy is a result of systolic dysfunction alone or both systolic and diastolic dysfunction. Eleven parameters were analyzed: E wave, E-AT, E-DT, E time, A wave, A-AT, A-DT, A time, E+A time, E/A ratio, and IVRT. The study confirmed the value of noninvasive echocardiographic assessment of diastolic function in dogs with dilated cardiomyopathy. Significant differences were found in E wave, E-AT, E time, E/A ratio and IVRT between healthy dogs and dogs with dilated cardiomyopathy. All are characterized by a significant decrease compared to healthy dogs after taking into account age and body weight except for the E/A ratio, which significantly increased in value. There were no significant changes in any of the Doppler parameters for diastolic evaluation in subclinical cases of DCM. Advanced heart failure in dilated cardiomyopathy entails systolic and diastolic dysfunction.     

Congestive heart failure caused by intracardiac tumours in two dogs

Congestive heart failure is a common presentation in small animal practice. Cardiac tumours are an unusual cause of congestive heart failure and, when they occur, usually cause clinical signs associated with pericardial effusion and cardiac tamponade. This case report outlines the clinical and histological findings in two dogs presented with clinical signs of congestive heart failure caused by obstruction of blood flow by intracavitary cardiac tumours. Case 1 showed signs of left-sided heart failure caused by osteosarcoma within the left atrial lumen, and case 2 presented with clinical signs of right-sided heart failure due to haemangiosarcoma occupying the right atrial and ventricular lumens. This case report provides further evidence for the inclusion of intracardiac neoplasia in the differential diagnosis for dogs with clinical signs of congestive heart failure.     

Canine hypertrophic cardiomyopathy.

Necropsy findings in 10 dogs with naturally occurring cardiac disease closely resembled hypertrophic cardiomyopathy in human beings and cats. Each dog had marked cardiac hypertrophy, and 8 dogs had disproportionate thickening of the ventricular septum with respect to the left ventricular free wall (compared with dogs with normal hearts or with cardiac hypertrophy due to acquired or congenital heart disease). Ratios of septum to free wall thickness in the 10 dogs ranged from 1.1 to 1.5, and 6 had ratios greater than or equal to 1.3. Marked cardiac muscle cell disorganization in the ventricular septum, characteristic of human patients with hypertrophic cardiomyopathy, was found in only 2 of the 10 dogs. Death occurred while the dogs were under anesthesia during the course of operative procedures (5 dogs) or unexpectedly in animals without previous manifestations of cardiac disease (3 dogs). Four dogs had clinical signs of congestive heart failure, including 2 with marked cardiac decompensation. Two of these 4 dogs with heart failure and 1 dog that died during unrelated surgery, but without prior signs of heart disease, had electrocardiographic evidence of complete heart block.     

Hypothyroidism and myocardial failure in two Great Danes

Two Great Danes were evaluated for signs of congestive heart failure. Dilated cardiomyopathy was diagnosed in each dog. Both dogs were diagnosed concurrently with primary hypothyroidism. Following appropriate supplementation with levothyroxine, both dogs showed significant improvement in myocardial contractility, as demonstrated by increased fractional shortening and reductions in left atrial size, and left ventricular end-systolic and diastolic diameters. These observations suggest that hypothyroidism may lead to myocardial failure in Great Danes that is partially or fully reversible following thyroid hormone replacement therapy, and that hypothyroidism should be considered in all Great Danes presenting with systolic failure.     

Usefulness of dobutamine stress tests for detection of cardiac abnormalities in dogs with experimentally induced early left ventricular dysfunction

OBJECTIVE: To determine whether dobutamine stress tests (DST) can be used to detect cardiac dysfunction in dogs with early left ventricular dysfunction (ELVD) induced by rapid right ventricular pacing (RRVP). ANIMALS: 7 adult male Beagles. PROCEDURE: A pacemaker was surgically implanted in each dog at the level of the right ventricular apex. Electrocardiography, Doppler sphygmomanometry, and Doppler echocardiography were performed before and during a DST prior to activation of the pacemaker and every 3 to 4 days during the period of RRVP. Dobutamine stress tests were performed by infusing dobutamine at incremental dosages ranging from 12.5 to 42.5 microg/kg of body weight/min. RESULTS: Clinical signs of congestive heart failure were not observed during the pacing period. However, all dogs developed ELVD associated with significant changes in values for most Doppler echocardiographic variables obtained prior to DST Adverse cardiac effects were not detected during DST. Most Doppler echocardiographic indices of cardiac function were significantly altered in response to dobutamine infusion during the pacing period, compared with prepacing values. However, a dobutamine-induced 2-fold increase in cardiac output was maintained. CONCLUSIONS AND CLINICAL RELEVANCE: Dobutamine stress tests can be safely performed in dogs with experimentally induced ELVD. Dobutamine stress tests may be a sensitive, noninvasive diagnostic method, complementary to standard clinical examinations, for detection of early cardiac dysfunction in dogs asymptomatic for dilated cardiomyopathy.     

Pulsus alternans in English cocker spaniels with dilated cardiomyopathy

OBJECTIVES: To report the clinical findings associated with pulsus alternans in English cocker spaniels with dilated cardiomyopathy and to review the phenomenon of mechanical alternans, usually found in patients with severe left ventricular systolic dysfunction. METHODS: The case records of 10 English cocker spaniels with dilated cardiomyopathy and pulsus alternans were reviewed. All dogs had been referred in moderate to severe congestive heart failure. Pulsus alternans was clinically recognised by palpation of a regular alternation of femoral pulse amplitude and confirmed by echocardiography in all cases. Pulsus alternans was an intermittent finding in all 10 dogs. RESULTS: Phonocardiographic recordings were obtained in three dogs to document variation in the intensity of the heart sounds, with one case exhibiting absence of the second heart sound in alternate beats. M-mode echocardiography performed in all dogs showed alternation of the pattern of mitral valve diastolic motion. Doppler echocardiography showed marked alternation in stroke volume in the aortic outflow in all cases. It also showed alternation in mitral regurgitation and in the velocity of early ventricular filling. CLINICAL SIGNIFICANCE: Pulsus alternans may be more prevalent in English cocker spaniels than in other breeds, and because of its intermittent nature, its incidence may be higher than that previously reported. It has diagnostic relevance as it usually indicates severe myocardial depression. Echocardiography allows non-invasive detection of mechanical alternans and provides further insights into its pathophysiology and clinical significance.     

Ischaemic heart disease in the dog: a review of 65 cases

Sixty-five dogs are reviewed with histopathologically confirmed intramural arteriosclerosis. Clinical data (clinical signs, electrocardiographic findings and ultrasound parameters) on these animals were collected from nine small animal clinics in Sweden: 16 dogs had died suddenly, with few or no previous clinical signs; 13 dogs died or were euthanased during or shortly after general anaesthesia or sedation; 30 dogs developed acute (14) or chronic (16) congestive heart failure; and six dogs died or were euthanased for causes unrelated to cardiac disease. Electrocardiography of 23 of the dogs revealed several types of arrhythmias, with atrial fibrillation and sinus tachycardia being most commonly detected. Ultrasonographic examinations of 24 dogs found a relatively high number (19) with decreased indices of contractility. Dogs that had died suddenly and in relation to general anaesthesia or sedation had a higher incidence (25 of 29) of purely arteriosclerotic changes in the myocardial vessels, whereas just over half the dogs with congestive heart failure (16 of 30) had other concomitant heart lesions (in most cases endocardiosis). The incidence of myocardial infarcts was high (51 of 65 cases). It is postulated that arteriosclerosis in the dog may be an important reason for sudden death and death during general anaesthesia. Coronary arterial disease should also be a consideration in the clinical evaluation of dilated cardiomyopathy and may contribute to the decreased myocardial contractility when it is present in dogs with mitral regurgitation.     

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.     

Arrhythmogenic right ventricular cardiomyopathy in dogs

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

Diagnosis and treatment of congestive heart failure secondary to dilated cardiomyopathy in a hedgehog

A one‐year‐old African pygmy hedgehog (Atelerix albiventris) was evaluated for severe respiratory distress. Physical examination findings included marked dyspnoea, cyanosis and tachypnoea. Radiographic findings included an enlarged heart and pulmonary oedema, and dilated cardiomyopathy was confirmed via echocardiogram. The patient was treated for congestive heart failure because of dilated cardiomyopathy with furosemide, enalapril, pimobendan and l‐carnitine. Within 24 hours of treatment, the pulmonary oedema and cyanosis had resolved. Following discharge, clinical improvement was noted by the owner and echocardiogram confirmed improved fractional shortening. Cardiomyopathy has been reported at post‐mortem examination in hedgehogs, but there are no reports of ante‐mortem diagnosis and treatment. Performing baseline cardiac assessment in hedgehogs is recommended, and treatment with l‐carnitine and pimobendan may improve outcome, as carnitine deficiency is a possible cause of cardiomyopathy in hedgehogs. Successful emergency treatment of congestive heart failure in the hedgehog of this report may be effective for other hedgehogs presented with similar clinical signs .     

Effect of medical therapy on survival of patients with dilated cardiomyopathy.

Few studies have been conducted that focus on survival as the end point of medical therapy of CHF. No vigorous studies have been conducted in dogs. It is generally accepted that diuretic therapy is an essential component of the therapy of CHF in cardiomyopathic dogs. Significant symptomatic improvement is afforded by diuretics, and acute death may be prevented. In this context diuretics can be said to improve survival. However, diuretics do not alter the natural progression of cardiomyopathy and in this context do not favorably influence long-term survival. Digitalis glycosides have been shown in humans to improve various parameters of CHF in a subset of patients with either atrial fibrillation or third heart sounds. In dogs, these gallop heart rhythms due to third heart sounds are usually associated with myocardial failure due to dilated cardiomyopathy. In spite of symptomatic improvement, no study has demonstrated an unequivocal favorable effect of digoxin on survival of patients with dilated cardiomyopathy. Likewise, there is no convincing evidence of an adverse effect on survival. Newer, powerful inotropes, such as milrinone, often demonstrate impressive short-term improvements in left ventricular function, clinical signs, and exercise tolerance in patients with CHF. However, their long-term benefits are much less impressive, they are arrhythmogenic, and they have not been shown to prolong survival. In fact, long-term milrinone therapy in humans has had an unfavorable influence on mortality. Vasodilators offer the potential advantage of increasing left ventricular performance without an associated increase in myocardial oxygen demand and cardiac rhythm disturbances. The only vigorous survival study that unequivocally demonstrated improved survival of patients with advanced CHF due to myocardial failure, including dilated cardiomyopathy, was the Consensus Trial. Survival of patients receiving enalapril was significantly better than those receiving placebo. In fact, the trial was stopped prematurely by the ethical review committee when it became obvious that the results favored the enalapril group. Although the use of beta-adrenergic blocking drugs in cardiomyopathic patients with CHF is controversial and associated with a risk of short-term deterioration of left ventricular function, their use in human medicine is gaining acceptance. Although hemodynamic and clinical evidence of improvement has been demonstrated along with withdrawal-associated deterioration, the only study purporting a beneficial effect on survival used retrospective controls.(ABSTRACT TRUNCATED AT 400 WORDS)     

Dilated cardiomyopathy in Presa canario dogs: ECG findings

Forty-seven Presa canario dogs were diagnosed with congestive heart failure due to dilated cardiomyopathy (DCM). Supraventricular or ventricular tachydysrhythmias were found in 29 dogs. Atrial fibrillation was the most common dysrhythmia. Ventricular dysrhythmias were observed infrequently and had a very important prognostic value in Presa canario dogs with DCM. Abnormalities of cardiac conduction were diagnosed in 16 (34%) dogs and changes in wave morphology were found in 29 (62%) dogs. Normal sinus rhythm was recorded in only 12 (26%) Presa canario dogs with DCM.     

A retrospective study of heart disease in doberman pinscher dogs

The prevalence of gross and/or histological cardiac lesions was found to be much greater in Doberman pinscher dogs (16/26 or 62%) than in non-Doberman dogs (124/417 or 30%). At least some of the affected Dobermans were unrelated. Middle aged (mean age 4.7 yr) Dobermans of both sexes (11 M:5F) were affected. Four of the Dobermans with heart lesions had congestive cardiomyopathy; three of these four had congestive heart failure and the other one died suddenly. Prominent gross lesions were ventricular dilation and atrioventricular valvular endocardiosis. Histological lesions noted were prominent myocardial fibrosis, myofiber degeneration with fatty replacement, myofiber vacuolation and arterial intimal cushion formation. A spectrum of myocardial disease exists in Dobermans and clinically overt congestive cardiomyopathy represents one end of this spectrum.     

Lack of efficacy of low-dose spironolactone as adjunct treatment to conventional congestive heart failure treatment in dogs

Aldosterone plays an important role in the pathophysiology of heart failure. Aldosterone receptor blockade has been shown to reduce morbidity and mortality in human patients with advanced congestive left ventricular heart failure. This study was designed to assess the efficacy and tolerance of long-term low-dose spironolactone when added to conventional heart failure treatment in dogs with advanced heart failure. Eighteen client-owned dogs with advanced congestive heart failure due to either degenerative valve disease (n=11) or dilated cardiomyopathy (n=7) were included in this prospective, placebo-controlled, double-blinded, randomized clinical study. After initial stabilization including furosemide, angiotensin-converting enzyme inhibitors, pimobendan and digoxin, spironolactone at a median dose of 0.52 mg/kg (range 0.49-0.8 mg/kg) once daily (n=9) or placebo (n=9) was added to the treatment, and the dogs were reassessed 3 and 6 months later. Clinical scoring, echocardiography, electrocardiogram, systolic blood pressure measurement, thoracic radiography, sodium, potassium, urea, creatinine, alanine aminotransferase, aldosterone and aminoterminal atrial natriuretic propeptide were assessed at baseline, 3 and 6 months. Survival times were not significantly different between the two treatment groups. Spironolactone was well tolerated when combined with conventional heart failure treatment.     

Anesthetic concerns for patients with cardiomyopathy.

Hypertrophic cardiomyopathy usually affects cats. The overall cardiac dysfunction associated with hypertrophic cardiomyopathy relates to a decrease in diastolic function. Anesthetic regimens that minimize increases in heart rate and stress-related catecholamine release are desirable. Patients with dilative cardiomyopathy can present asymptomatic or in congestive heart failure. The overall myocardial defect is a depression of systolic function. An anesthetic regimen that minimizes myocardial depression is essential.