Oculocardiac reflex in a dog caused by a choroidal melanoma with orbital extension

A 7 yr old mixed-breed dog was presented with a choroidal melanoma of the left eye that had penetrated the sclera, producing an orbital mass. Bradycardia was detected on auscultation. The bradycardia resolved after exenteration of the orbit and was therefore presumed to be associated with the oculocardiac reflex.     

Surgical correction of severe strabismus and enophthalmos secondary to zygomatic arch fracture in a dog

A grossly displaced segmental zygomatic arch fracture with marked ventro-lateral deviation of the left globe was diagnosed in a 3-month-old male German Shepherd dog following a bite injury. The fracture was approached via a modified lateral orbitotomy and a fragment of the lacrimal bone removed. The rostral portion of the fracture was stabilized with a 5-hole 2.0 dynamic compression plate bone plate. The surgical correction achieved sufficient skeletal fixation for proper anatomical reduction of the globe and excellent cosmetic and functional outcomes.     

Ventricular rate control using a novel vagus nerve stimulating system in a dog with chronic atrial fibrillation

A 4-year-old, intact male Dogue de Bordeaux dog with congenital valvular pulmonic stenosis, tricuspid valve dysplasia, and chronic atrial fibrillation underwent ultrasound-guided balloon valvuloplasty in addition to pharmacological treatment. Owner compliance to prescribed pharmacotherapy proved very poor, and concerns developed regarding the ability to successfully control heart rate and symptoms using drug therapy alone. These concerns were addressed by the implantation of a novel vagal stimulation system that was programmed to prevent a ventricular rate of >145 bpm. Consequently, post-operative ventricular response rate decreased from up to 250 to 140 bpm. Successful ventricular rate control was maintained for 291 days post-operatively, following which euthanasia was elected by the owner due to persistent right-sided congestive heart failure. To the authors' knowledge, this is the first report of successful continuous rate control using a vagal stimulating system in a closed-chest, client-owned dog with chronic atrial fibrillation secondary to spontaneously occurring organic heart disease.     

The influence of age on patellar reflex response in the dog

The patellar tendon reflex is a clinical parameter commonly used to assess neurological status. Factors such as quadriceps muscle fiber composition, femur length, and patient age have been reported to influence total and fractionated reflex times in human beings. The purpose of this blinded, cross-sectional study was to examine the effect of age on the patellar reflex in the dog. Eighty-six dogs without evidence of neurological impairment or orthopedic disease of the stifle (eg, patellar luxation or cranial cruciate ligament rupture) were assigned to 1 of 2 groups on the basis of age: group 1, <10 years old (n = 72); or group 2, > or =10 years old (n = 14). Patellar reflexes were elicited in both pelvic limbs by a reflex hammer while the dog was in lateral recumbency. The reflex was scored as present or absent by a blinded individual. Two dogs in group I had reflexes absent in both limbs, 3 dogs in group 2 had reflexes absent in both limbs, and 1 dog in group 2 lacked a response in 1 limb. The proportion of dogs with absent patellar reflexes in group 2 (4 of 14, 95% CI, 8-58%) was significantly higher than the proportion of dogs with absent patellar reflexes in group 1 (2 of 72, 95% CI, 0-10%) (P < .006). Furthermore, dogs lacking at least 1 patellar reflex were older than those having both reflexes present (P = .04). Weight was not related to the presence of both reflexes (P = .49). These findings suggest that neurologically normal dogs may have an age-dependent decline in patellar reflex magnitude or a prolongation of total reflex time (TRT).     

Spontaneous closure of a traumatic acquired Gerbode defect in a dog

A one-year-old female English Springer Spaniel with no previous history of cardiac disease presented to the Queen's Veterinary School Hospital following a blunt traumatic incident with an acquired, direct Gerbode defect and associated third-degree atrioventricular block. Two months after the initial incident, follow-up echocardiography showed a nearly closed Gerbode defect with just trivial residual flow. A 24-h Holter monitor indicated second-degree atrioventricular block with occasional junctional tachycardia. A reassessment 22 months later confirmed spontaneous closure of the previously acquired traumatic Gerbode defect, with 2:1 second-degree atrioventricular block. The dog remained clinically asymptomatic, and free of treatment. To our knowledge, this is the first reported case of spontaneous closure of a previously acquired traumatic Gerbode defect in a dog.     

Mastitis caused by Mycobacterium kansasii infection in a dog

A 2‐year, 7‐month‐old female Chihuahua was admitted for a mammary mass measuring one cm in diameter. The dog had a history of demodicosis for 4 months and showed signs of pseudopregnancy at the time of the visit. Cytologic examination of an aspirate of the mass revealed a large number of macrophages containing nonstaining bacterial rods, which were acid‐fast in a Ziehl–Neelsen stain, suggesting mycobacterial infection. Histologic examination of the mass revealed a pyogranulomatous mastitis characterized by an infiltration with macrophages containing acid‐fast bacteria. Mycobacterium kansasii was subsequently cultured and identified by PCR. Surgical excision of the mass resulted in the growth of other dermal masses, but antimycobacterial treatment with rifampin and clarithromycin resolved these masses within 1 month. Three months after discontinuation of the treatment, similar organisms were found in aspirates of the enlarged bilateral inguinal lymph nodes by cytologic examination. Despite antimycobacterial treatment for another 4 months, there was no improvement and demodicosis also recurred. The dog eventually died of lymphoma 5 months after the relapse of mycobacterial infection. Although M kansasii is considered an important pathogen for pulmonary and cutaneous disease in people, there is only one report in a dog with an infection in a pleural effusion. As both adult‐onset demodicosis in dogs as well as mycobacterial infection in people have been associated with T‐lymphocyte deficiency, the M kansasii infection in this dog may have been associated with a condition of immune compromise.     

Caudal vena cava obstruction caused by redundant pacemaker lead in a dog

Inferior vena cava obstruction, a rare but serious complication of transvenous pacemaker lead placement in humans, has not been reported in dogs. We describe this complication in a dog that developed ascites 8 months after pacemaker implantation. Radiography disclosed a loop of redundant lead within the caudal vena cava (CVC), and angiography demonstrated obstruction to blood flow. Withdrawal of the loop from the CVC did not restore blood flow. Persistent obstruction was suspected secondary to fibrosis resulting from vascular damage caused by the loop of lead. Angioplasty of the CVC obstruction restored blood flow and resolved the dog's clinical signs.     

Surgical management of an aberrant left subclavian artery originating from a left patent ductus arteriosus in a dog with a right aortic arch and abnormal branching

An increase in the availability of advanced imaging modalities has led to improved recognition of cardiovascular anomalies. Computed tomography angiography (CTA) provides a non-invasive means of acquiring 3D images with a relatively short acquisition time thereby providing essential information in regards to patient anatomy and procedure planning. The dog in this report had a right aortic arch and abnormal branching with an aberrant left subclavian artery originating from the ampulla of a left patent ductus arteriosus (PDA) that was detected with CTA. The PDA was creating a volume overload to the left side of the heart as well as contributing to the vascular ring and compression of the esophagus. Therefore, ligation and transection instead of a minimally invasive catheter-based procedure was required. This aortic arch anomaly and surgical management have not been previously reported in dogs.     

May-Hegglin anomaly in a dog

An 8-year-old female spayed Pug dog was presented for evaluation of cutaneous lesions occurring secondary to immunosuppressive treatment of presumed immune-mediated thrombocytopenia. Abnormal hematologic findings included persistent thrombocytopenia, macrothrombocytes, and variably shaped, often fusiform, blue cytoplasmic inclusions in neutrophils. May-Hegglin anomaly (MHA) was suspected based on the morphologic appearance of platelets and neutrophils. Examination of cells by transmission electron microscopy revealed normal platelet ultrastructure; neutrophil inclusions had features similar to those reported for inclusions in human MHA. Neutrophil function was within normal limits based on flow cytometric analysis. Thrombelastography indicated a prolonged clotting time (r), and PlateletMapping showed a lack of response to 2 μM ADP compared with a moderate response in the control dog. Immunocytochemical staining of blood smears using 2 commercially available antibodies against MYH9 protein (nonmuscle myosin heavy chain II) yielded negative results. However, genomic DNA sequencing analysis of the dog's MYH9 gene identified a single point mutation, resulting in substitution of lysine for glutamine at the 1841 amino acid position; this mutation is identical to one identified in people with MHA. To our knowledge, this is the first report of an MYH9 mutation in the dog. MHA-associated macrothrombocytopenia may be mistaken for immune-mediated thrombocytopenia.     

Intracardiac echocardiography: use during transcatheter device closure of a patent ductus arteriosus in a dog

Intracardiac echocardiography (ICE) is used in humans for percutaneous interventional procedures, such as transcatheter device closures. Intracardiac echocardiography provides high-resolution imaging of cardiac structures with two-dimensional, M-mode, Doppler, and also three-dimensional modalities. The present report describes application of ICE during transcatheter occlusion of patent ductus arteriosus using a canine ductal occluder in a dog for which transesophageal echocardiography could not provide an optimal acoustic window.     

Partial anomalous pulmonary venous connection in a dog

A 2-year-old male intact Belgian Malinois was presented for exercise intolerance. A grade III/VI left basilar systolic murmur was detected. Echocardiography revealed moderate right atrial and ventricular dilation and increased pulmonic outflow velocity. Thoracic radiographs showed right heart enlargement and a dilated caudal vena cava. In addition, on the left lateral projection, an enlarged aberrant right cranial pulmonary lobar vein was suspected to be diverging ventrally from the course of the right cranial lobar bronchus and inserting more ventrally than normal in the region of the right atrium. A left-to-right pulmonary vascular shunt was suspected, and the patient underwent further diagnostics under general anesthesia. An agitated saline study was positive, suggestive of a concurrent right to left shunt. A right heart catheterization was performed. Angiography was inconclusive. Oximetry testing revealed an increase in oxygen saturation within the right atrium at the level of the caudal cava supportive of a left-to-right shunt in this region. Computed tomography angiography revealed a large single pulmonary vein that anomalously entered into the caudolateral aspect of the right atrium (left-to-right shunt) and was suspicious for a small arteriovenous malformation between the right caudal pulmonary artery and the right pulmonary vein returning to the left atrium (right to left shunt). The patient was diagnosed with a partial anomalous pulmonary venous connection and a possible arteriovenous malformation.     

Computed tomography angiography of coarctation of the aorta in a dog

Coarctation of the aorta has been described previously as either a post-mortem or angiographic finding in three dogs with clinical signs related to the aortic coarctation. A 10-year-old dog was presented for evaluation of suspected laryngeal paralysis. On physical examination, femoral pulses were absent bilaterally, with an indirect systolic blood pressure difference of 60 mmHg between the ipsilateral thoracic and pelvic limbs. Coarctation of the aorta was detected on a thoracic computed tomographic angiography study. The coarctation was pre-ductal in position, with extensive dilation of the descending thoracic aorta. Characteristic rib changes that are seen in humans with coarctation were not apparent in this dog. 3D reconstructions of the thorax provided high vascular definition with exact localization of the aortic narrowing.     

Extramedullary laryngeal plasmacytoma in a dog

Abstract

CASE HISTORY:?An 8-year-old, female, spayed Border Collie presented with a 3-week history of coughing, choking and haemoptysis.

CLINICAL FINDINGS:?Inspiratory stridor was evident on clinical examination. Cervical radiographs revealed a round soft-tissue mass on the dorsal aspect of the epiglottis. A laryngeal mass was evident on examination under anaesthesia, and an incisional biopsy was obtained. Histopathology revealed a dense proliferation of neoplastic round cells morphologically consistent with plasma cell origin. Immunohistochemisty results were negative for CD3 (T cell marker) and positive for CD79a (B cell marker), resulting in a diagnosis of extramedullary plasmacytoma. The patient was treated with melphalan and prednisolone; clinical signs resolved within 1 week and the mass was no longer evident on laryngoscopy after 1 month of treatment. After 6 months of chemotherapy, the laryngeal mass recurred and euthanasia was requested. There was no evidence of systemic spread on post-mortem examination.

DIAGNOSIS:?Solitary extramedullary plasmacytoma of the canine larynx.

CLINICAL RELEVANCE:?Respiratory extramedullary plasmacytomas are extremely rare with only one laryngeal and two tracheal cases previously reported. This is the first published report of a laryngeal plasmacytoma that recurred despite combination chemotherapy with melphalan and prednisolone.     

Conversion of atrial dissociation with lidocaine in a dog

A 3-year-old healthy dog was presented for abdominal surgery following ingestion of razor blades. An electrocardiogram revealed a regular sinus bradycardia with normal P waves at a heart rate of 45 bpm. In addition, low-amplitude positive deflections (p′ waves) were visualized at a regular interval and rapid rate of 250 bpm, dissociated from the normal sinus P waves. A tentative diagnosis of atrial dissociation was proposed. Administration of lidocaine abolished the p′ waves. This case describes atrial dissociation observed following premedication that was successfully terminated using lidocaine in a healthy dog.     

Presumptive vagally-mediated atrial flutter in a dog

An asymptomatic nine-year-old Dobermann Pinscher underwent a screening for dilated cardiomyopathy. Echocardiography revealed left ventricular eccentric hypertrophy and systolic dysfunction; the rest of the echocardiographic parameters were within normal limits. Holter monitoring demonstrated sinus rhythm as the dominant cardiac rhythm during the first hours of the recording. Then, during a period of physiologically enhanced vagal tone (sleep), spontaneous development of atrial flutter (AFL) associated with variable ventricular response was documented. Alternation between AFL and paroxysmal atrial fibrillation was also observed. Subsequently, during a period of physiological increase of sympathetic tone (physical activity/excitement), spontaneous conversion of AFL to sinus rhythm occurred. In light of these findings, a presumptive diagnosis of vagal AFL was made. The images here described allow us to study the onset, behavior and termination of this intriguing electrocardiographic entity.     

Clinically silent atrial dissociation in a dog

A Labrador retriever, presented for a routine yearly wellness exam, shows on ECG a normal sinus rhythm with first degree atrioventricular blockade and atrial dissociation (AD). A detailed cardiologic examination was performed including thoracic radiography, echocardiography and blood pressure measurement, all of which were considered normal. The dog described in this current report was re-examined several times over the subsequent 2 years and no clinical signs of heart failure, heart disease or other diseases were recognized, the AD appears to have been benign.     

Permanent junctional reciprocating tachycardia in a dog

A 5-year-old male English Bulldog was presented with a 1-year history of paroxysmal supraventricular tachycardia (SVT) partially responsive to amiodarone. At admission the surface ECG showed sustained runs of a narrow QRS complex tachycardia, with a ventricular cycle length (R–R interval) of 260 ms, alternating with periods of sinus rhythm. Endocardial mapping identified the electrogenic mechanism of the SVT as a circus movement tachycardia with retrograde and decremental conduction along a concealed postero-septal atrioventricular pathway (AP) and anterograde conduction along the atrioventricular node. These characteristics were indicative of a permanent junctional reciprocating tachycardia (PJRT). Radiofrequency catheter ablation of the AP successfully terminated the PJRT, with no recurrence of tachycardia on Holter monitoring at 12 months follow-up.