Third degree atrioventricular block and sudden death secondary to acute myocarditis in a dog

Third degree atrioventricular (AV) block in dogs is thought to be most frequently characterized by non-specific fibrotic changes in the AV node. However, it may occur secondary to an undiagnosed inflammatory process. We report a case of third degree AV block in a dog, secondary to acute lymphocytic-plasmacytic myocarditis that resulted in sudden death. This dog had cardiac troponin I levels of 44.65 ng/mL (normal <0.11 ng/mL). The serum cardiac troponin I level was five times higher than any other AV block patient measured in our laboratory, and was also substantially higher than in dogs with chronic valve disease or dilated cardiomyopathy. The severe myocardial necrosis observed at necropsy correlated with the degree of cardiac troponin I elevation. This report suggests that measurement of cardiac troponin I may be an indicated test before pacemaker implantation in dogs with third degree AV block.     

Complete heart block associated with lupus in a dog

A 5-year-old Poodle-cross was initially presented for exercise intolerance and difficulty in chewing and yawning. Some months later it acutely developed lethargy referable to complete heart block. Further investigations before and after permanent pacemaker implantation demonstrated Coombs-positive immune-mediated haemolytic anaemia, presumptive masticatory myositis and hypoadrenocorticism, suggesting the possibility of multisystem auto-immune disease. A diagnosis of systemic lupus erythematosus (SLE) was made based on these findings and a positive anti-nuclear antibody titre. It was thought that immune-mediated destruction of cardiac conduction tissues was responsible for the development of atrioventricular conduction block. Glucocorticoid deficiency was corrected using cortisone replacement therapy. SLE was controlled successfully for 10 months using azathioprine monotherapy until signs, subsequently shown to be due to subacute bacterial endocarditis, resulted in the death of the patient. Lupus should be considered as a potential underlying aetiology in dogs that develop heart block.     

Focal myasthenia gravis in a dog.

A 10-month-old American cocker spaniel was evaluated for megaesophagus, aspiration pneumonia, but no appendicular muscle weakness. During hospitalization, weakness of the facial muscles developed, this resolved with anticholinesterase administration. Serum antibodies against acetylcholine receptors were documented, confirming the diagnosis of focal myasthenia gravis. Diagnosis, management, and medical treatment are discussed.     

Focal cystic hypertrophic gastropathy in a dog

A 6-year-old female dog had a 3-day history of postprandial vomiting of undigested food. Plain and contrast radiography revealed a large mass on the greater curvature of the stomach. On exploratory gastrotomy, the mass was found to consist of hypertrophic rugae resembling cerebral gyri and sulci. The histopathologic findings were similar to those for hypertrophic gastropathy in man and the dog.     

Intracranial metastases from an ovarian dysgerminoma in a 2-year-old dog.

A 2-year-old, intact female rottweiler was presented for signs of lethargy. A mass was ultrasonographically observed, cranial and lateral to the left kidney. Exploratory laparotomy revealed a mass in the left ovary that was diagnosed histopathologically as an ovarian dysgerminoma. Two weeks after surgery, the dog was readmitted with signs of peripheral vestibular disease that progressed to central vestibular disease. Magnetic resonance imaging of the brain revealed the presence of a mass in the caudal fossa. The histopathological diagnosis of the mass was metastases from the ovarian dysgerminoma.     

Complete atrioventricular block secondary to cardiac lymphoma in a dog

Third degree atrioventricular (AV) block was observed in a patient with a roughly spherical mass measuring approximately 1 × 1 × 1 cm, visible in the basilar portion of the interventricular septum on 2-dimensional transthoracic echocardiographic examination. The patient had a brief history of lethargy and episodic collapse, and the owner elected to euthanize the dog after the mass lesion was discovered. Necropsy revealed multiple masses within the interventricular septum, ventricular free walls and atrial myocardium. The final diagnosis was large cell (T-cell) lymphosarcoma.     

Suspected disseminated histiocytic sarcoma in a 3-year-old Perro de Presa Canario dog

A 3-year-old intact male Perro de Presa Canario dog was presented with acutely inflamed and edematous right hind limb, scrotum, prepuce, and an enlarged left carpus. Two weeks later the dog returned with weight loss, draining tracts in the right hind limb, dermal nodules, a palpable abdominal mass, and uveitis in the left eye. The dog succumbed to his illness 2 days later and a widely disseminated round cell tumor compatible with histiocytic sarcoma was diagnosed following postmortem examination.     

Recurrent supraventricular arrhythmias in a dog with atrial myocarditis and gastritis

This report describes a dog with recurrent atrial fibrillation and atrial flutter associated with chronic gastritis. Although no underlying structural heart disease was apparent antemortem or on gross post-mortem examination, chronic atrial myocarditis was seen on histopathological examination. Atrial myocarditis is a recognised cause of atrial fibrillation in human beings with presumed lone fibrillation, and an association between supraventricular tachyarrhythmias and infectious agents has been made.     

Atrial myocarditis as a cause of sinus arrest in a dog

A 10-year-old male cairn terrier cross was presented with a history of myxomatous mitral valve disease diagnosed six months previously and with a four-week history of intermittent collapse. On 24 hour electrocardiograph (Holter) analysis, periods of no discernable electrical cardiac activity, which coincided with three collapsing episodes, were identified. Unfortunately, on re-presentation for removal of the Holter monitor, the dog collapsed and died. A post-mortem examination was conducted, and histology of the right and left atrium showed evidence of myocarditis. This is the first reported case, to our knowledge, of collapse because of electrical asystole in a dog with atrial myocarditis.     

Large granular lymphocytic leukemia in a mixed breed dog

A mixed breed dog was diagnosed with large granular lymphocytic leukemia. Immunophenotypic analysis indicated the lymphocytes were CD3+, CD8+ T cells expressing the alpha beta T cell receptor and a leukointegrin, alpha d. Chemotherapy and splenectomy resulted in an initial reduction in the lymphocyte count.     

Sinoatrial arrest associated with primary atrial myocarditis in a dog

The clinical findings in a dog with sinoatrial arrest, atrioventricular block and multifocal idioventricular escape beats are described. The clinical findings were associated with a primary myocarditis involving the sinoatrial node, the left and right atrium and atrioventricular node. The differentiation between sinoatrial arrest, sinoatrial block and sinoventricular conduction is discussed.     

Dilatation of the right atrium in a dog with polymyositis and myocarditis

A nine-year-old, female, neutered golden retriever was referred for investigation of weakness. Immune-mediated polymyositis with mixed mononuclear cell inflammation and fibrosis was diagnosed in muscle biopsy specimens from several sites. A soft tissue opacity was noted radiographically cranial to the cardiac silhouette. The dog failed to respond to treatment with prednisolone and was euthanased. At post-mortem examination, the structure observed radiographically was showed to be an enlarged right atrium. Histopathological examination of samples collected at post-mortem confirmed polymyositis. Additionally, mononuclear cell infiltrations and fibrosis were observed in areas of endocardium and/or myocardium in the walls of all four cardiac chambers. Myocarditis has not been reported previously in canine polymyositis but is well recognised in people. Enlargement of the right atrium has also been reported in association with polymyositis and myocarditis in people.     

Acute respiratory distress syndrome in a 10-year-old dog

A 10-year-old shih tzu was presented with lethargy, anorexia, coughing, and dyspnea of 2 days' duration. Despite treatment with parenteral fluids, corticosteroids, antibiotics, and diuretics, the dog died. Acute respiratory distress syndrome was diagnosed histologically.     

Insulin-secreting beta cell neoplasia in a 10-year-old dog

A 10-year-old collie-cross presented with intermittent episodes of pelvic limb weakness and collapse. Hypoglycemia, secondary to an insulin-secreting beta cell tumor, was suspected on the basis of clinical signs and serum biochemistry. Conservative dietary therapy consisted of multiple small meals, limited exercise, and avoidance of foods containing simple sugars.