Presumed primary cardiac mast cell tumor, pericardial effusion, and arrhythmia in a dog.

A 13-year-old female spayed border collie cross presented for pericardial effusion, arrhythmia, and a suspected cardiac mass. Echocardiogram revealed severe thickening and hypokinesis of the interventricular septum with a heterogenous, cavitated myocardium, concerning for neoplasia. Electrocardiogram revealed predominantly accelerated idioventricular rhythm with frequent periods of nonsustained ventricular tachycardia. Occasional prolonged PR intervals terminating in an aberrantly conducted QRS complex were present. These beats were postulated to represent either first-degree atrioventricular block with aberrant QRS conduction or atrioventricular dissociation. Cytology of the pericardial effusion revealed atypical, suspected neoplastic, mast cells. The patient was euthanized, and postmortem examination confirmed full-thickness infiltration of the interventricular septum by a mast cell tumor, with metastasis to the tracheobronchial lymph node and spleen. Given the anatomic location of the mass, the observed atrioventricular nodal conduction delay may represent neoplastic infiltration of the atrioventricular node. Neoplastic infiltration of the ventricle was suspected to cause the accelerated idioventricular rhythm and ventricular tachycardia. To the authors' knowledge, this is the first reported case of a primary cardiac mast cell tumor causing arrhythmia and pericardial effusion in a dog.

The anatomical basis of third-degree atrioventricular block in dogs with atrioventricular valve endocardiosis.

The cardiac conduction system was examined histologically in 13 canine cases of atrioventricular (AV) valve endocardiosis with third-degree AV block. In all cases, gross examination revealed marked thickening and distortion of the base of the central fibrous body (CFB) and varying degrees of endocardial thickening of the upper portion of the ventricular septum (VS) as well as marked thickening of the mitral and tricuspid valve leaflets due to myxomatous degeneration. Microscopically, the thickened and distorted CFB had encased or trapped, either partly or totally, the underlying penetrating and branching portions of the AV bundle. The myxomatous and/or fibrofatty tissue, which had proliferated at the base of the extensive CFB, protruded into or encroached on the AV bundle, causing severe (51-75%) to very severe (76% or more) reduction of the conduction fibres. The upper portions of the left and right bundle branches were involved in the endocardial thickening due to degenerative and fibrotic changes at the uppermost VS; however, both bundle branches were much less severely affected than the AV bundle, the degree of reduction of the conduction fibres ranging from mild (25% or less) to moderate (26-50%). These observations suggest that the sites most vulnerable to lesions in the AV conduction system are the penetrating and branching portions of the AV bundle, which would represent the anatomical basis for third-degree AV block in canine cases of AV valve endocardiosis.

Third-degree atrioventricular block secondary to infiltrative cardiac hemangiosarcoma in a dog.

A nine-year-old male, castrated Pembroke Welsh Corgi presented with a two-month history of lethargy, hyporexia, and occasional vomiting. There was also a two-week history of exercise intolerance; no syncopal episodes were reported. Auscultation revealed bradycardia with an irregular rhythm and otherwise normal heart and lung sounds. Third-degree atrioventricular block was diagnosed. Two-dimensional transthoracic echocardiography revealed a soft tissue structure arising from the atrioventricular junction and interatrial septum. There was scant abdominal effusion. Pacemaker implantation was offered, but the owner elected humane euthanasia due to the unknown prognosis. Necropsy was consistent with cardiac hemangiosarcoma infiltrating the interatrial and interventricular septum.

Epicardial pacemaker implantation and outcome in eight pet ferrets (Mustela putorius furo).

INTRODUCTION/OBJECTIVES: Minimal information exists regarding epicardial pacemaker (EP) implantation in pet ferrets (Mustela putorius furo). The objectives were to describe the indications, surgical technique, and outcome of EP implantation in ferrets for the treatment of advanced atrioventricular block (AVB). ANIMALS, MATERIALS, AND METHODS: Eight client-owned ferrets presenting to five veterinary referral centers. Signalment, physical exam findings, diagnostic tests, anesthesia protocols, surgical implantation techniques, postoperative treatment plans, and EP interrogations were reviewed. Intra- and postoperative, minor and major, and EP-related complications were established. Descriptive statistics were performed to report complication rates. Survival analyses were performed. RESULTS: All ferrets had advanced AVB: 3/8 had high-grade second-degree and 5/8 had third-degree. The primary clinical signs were collapse and weakness. Seven EP were implanted via a transdiaphragmatic approach and one via a left intercostal thoracotomy. Intraoperative complications occurred in 2/8 ferrets, both major. One ferret with severe comorbidities died during general anesthesia. Postoperative pacemaker-related complications were minor: inappropriate sinus beat sensing in 2/8 and occasional muscle fasciculations in 1/8. Two ferrets were alive at the time of manuscript submission, at 10 and 21 months postoperatively. The overall median survival time was 24 months. CONCLUSIONS: Implantation of EP was performed successfully in most ferrets for treatment of advanced AVB and was well tolerated. Ferrets with advanced AVB may experience resolution of clinical signs associated with their cardiac disease following EP implantation. Additional studies are warranted to investigate the effects of epicardial pacing on survival times in this species.

HYPERTENSIVE HEART DISEASE AND ENCEPHALOPATHY IN A CENTRAL BEARDED DRAGON (POGONA VITTICEPS) WITH SEVERE ATHEROSCLEROSIS AND FIRST-DEGREE ATRIOVENTRICULAR BLOCK.

A 0.5 kg, 5-yr-old male bearded dragon (Pogona vitticeps) presented with a 2-mo history of lethargy, anorexia, and impaired locomotion. Upon physical examination, bradyarrhythmia (heart rate: 20 beats/min) and balance disorders were noted. Electrocardiography revealed a first-degree atrioventricular block (P-R interval: 360 ms). On echocardiography, all cardiac chambers were slightly above normal ranges. Complete blood count, blood biochemistry, and T4 were unremarkable except for mildly elevated aspartate aminotransferase. Adenovirus testing was negative by polymerase chain reaction. Following euthanasia, necropsy revealed marked thickening of the arterial trunks and histopathology confirmed multifocal atherosclerosis of efferent heart vessels, arteriosclerosis of cerebral arterioles, and multifocal spongiosis of brain tissue, more pronounced in the optic chiasma. Owing to its severity, atherosclerosis may have contributed to chronic arterial hypertension with damages to the heart, brain vessels, and brain tissue-optic chiasma.

Electrocardiographic, echocardiographic, and left atrial strain imaging features of a dog with atrial flutter and third-degree atrioventricular block.

A 14-year-old American Staffordshire terrier was presented for episodes of exercise-induced syncope. At admission, atrial flutter coupled to third-degree atrioventricular block was diagnosed electrocardiographically. On the second day of hospitalization, surface electrocardiogram revealed spontaneous conversion to sinus rhythm with persistence of atrioventricular block. Complete transthoracic echocardiograms were performed after each electrocardiographic examination. The combined use of conventional echocardiography with tissue Doppler imaging-based modalities allowed to investigate the atrial electromechanical correlation and function during typical atrial flutter and after its resolution.

Simultaneous pheochromocytoma and third-degree atrioventricular block in 2 dogs.

OBJECTIVE: To describe the occurrence of pheochromocytoma with third-degree atrioventricular (AV) block in 2 dogs. CASE SERIES SUMMARY: Two dogs were referred for echocardiograms and further diagnostic and therapeutic treatment for third-degree AV block. Abdominal ultrasound of 1 dog revealed an adrenal mass, while that of the other dog revealed bilateral adrenal masses. While undergoing treatment, 1 dog experienced cardiac arrest and could not be revived with cardiopulmonary resuscitation, and the other dog was humanely euthanized. Histological findings of the masses were consistent with pheochromocytomas. NEW OR UNIQUE INFORMATION PROVIDED: To the authors' knowledge, this is the first report with histologic evidence of pheochromocytoma and clinical presentation of third-degree AV block in dogs. In human literature, simultaneous presentation of both disease states is rare and has been infrequently reported.

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.

Cardiac leiomyoma associated with advanced atrioventricular block in a young dog.

A 1 year old intact female Labrador retriever dog presented for evaluation of syncope caused by severe bradycardia. Advanced atrioventricular block was diagnosed. A mass infiltrating the interventricular septum and the tricuspid annulus was identified with echocardiography. Histopathological evaluation of the mass was consistent with cardiac leiomyoma, and immunohistochemical staining for smooth muscle actin confirmed the diagnosis. To the authors' knowledge, this is the first report of cardiac leiomyoma in the canine species.

Use of transcutaneous external pacing during transvenous pacemaker implantation in dogs.

The aim of this retrospective study was to evaluate the utility of transcutaneous external pacing (TEP) during transvenous pacemaker implantation in dogs. Eighty-two pacemakers were implanted in 77 dogs because of third-degree atrioventricular block (AVB) (58 cases; 70.7 per cent), sinus node dysfunction (SND) (nine cases; 11.0 per cent), high-grade second-degree AVB (six cases; 7.3 per cent), persistent atrial standstill (PAS) (four cases; 4.9 per cent), post-radiofrequency catheter ablation of the bundle of His (four cases; 4.9 per cent) and vasovagal syncope with atrial fibrillation (one case; 1.2 per cent). TEP was initiated during general anaesthesia after the onset of asystole or profound bradycardia, and stopped when permanent pacing was started. The use of TEP was necessary in 27 cases: 19 cases of third-degree AVB, five of SND, two of PAS and one of vasovagal syncope. External pacing was successful in all but two dogs.

Pre- and post-operative cardiac evaluation of dogs undergoing lobectomy and pneumonectomy.

This study aimed to assess the influence of lobectomy and pneumonectomy on cardiac rhythm and on the dimensions and function of the right-side of the heart. Twelve dogs undergoing lobectomy and eight dogs undergoing pneumonectomy were evaluated preoperatively and one month postoperatively with electrocardiography and Doppler echocardiography at rest. Pulmonary artery systolic pressure (PASP) was estimated by the tricuspid regurgitation jet (TRJ) via the pulse wave Doppler velocity method. Systemic inflammatory response syndrome criteria (SIRS) were also evaluated based on the clinical and hematological findings in response to lobectomy and pneumonectomy. Following lobectomy and pneumonectomy, we predominantly detected atrial fibrillation and varying degrees of atrioventricular block (AVB). Dogs that died within seven days of the lobectomy (n = 2) or pneumonectomy (n = 1) had complete AVB. Preoperative right atrial, right ventricular, and pulmonary artery dimensions increased gradually during the 30 days (p < 0.05) following pneumonectomy, but did not undergo significant changes during that same period after lobectomy. Mean PASP was 56.0 +/- 4.5 mmHg in dogs having significant TRJ after pneumonectomy. Pneumonectomy, but not lobectomy, could lead to increases (p < 0.01) in the SIRS score within the first day post-surgery. In brief, it is important to conduct pre- and postoperative cardiac evaluation of dogs undergoing lung resections because cardiac problems are a common postoperative complication after such surgeries. In particular, complete AVB should be considered a lifethreatening complication after pneumonectomy and lobectomy. In addition, pneumonectomy appears to increase the likelihood of pulmonary hypertension development in dogs.

Gerbode type defect and third degree atrioventricular block in association with bacterial endocarditis in a dog.

Gerbode type defects are rare left ventricular outflow tract-right atrial communications in people that may be congenital or acquired; they have been reported only once previously in dogs. Acquired forms in humans have been reported secondary to bacterial endocarditis, trauma, and valve replacement surgery, among other causes. We report a case of left ventricular outflow tract to right atrium and right ventricle communications (Gerbode type defect) in association with aortic and tricuspid valve bacterial endocarditis in a geriatric dog. The dog also developed third degree atrioventricular block and had underlying subaortic stenosis. The authors hypothesize that the Gerbode type defect in this case was acquired secondary to invasion and destruction of the membranous interventricular septum due to bacterial endocarditis.

Third degree atrioventricular block and accelerated idioventricular rhythm associated with a heart base chemodectoma in a syncopal Rottweiler.

A 7-year-old male intact Rottweiler was presented with a 1-week history of lethargy, anorexia, vomiting and multiple syncopal events. The results of the clinical examination and electrocardiography were consistent with a third degree atrioventricular block and an intermittent accelerated idioventricular rhythm. Haematology, serum biochemistry, serology for Borrelia burgdorferi, blood culture, total T4, thoracic radiography and echocardiography did not reveal the cause of the arrhythmia. Response to medical treatment with isoproterenol was poor. Pacemaker placement was declined by the owners and the dog was euthanized at their request. Histopathological examination of the heart revealed a chemodectoma at the base of the heart. There was no neoplastic infiltration of the conduction tissue. Potential mechanisms explaining the association of the arrhythmias and the tumour, such as vagal stimulation and neuroendocrine factors are discussed.

Tricuspid valve stenosis caused by fibrous adhesions to an endocardial pacemaker lead in a dog.

Acquired tricuspid valve stenosis (TVS) is a rare complication of endocardial lead placement in humans that has not been described in the veterinary literature. We describe a 6.5-year-old Border terrier that was presented with right-sided congestive heart failure 5.5 years after placement of a transvenous pacemaker. Severe TVS was confirmed by cardiac ultrasonography and appeared to be secondary to excessive endocardial pacemaker lead within the right atrium. Repositioning of the lead proved impossible and subsequent postmortem examination demonstrated fusion of the tricuspid valve (TV) leaflets around the endocardial lead with associated narrowing of the tricuspid valve orifice. In addition, the loop of the endocardial lead was anchored by thick fibrous tissue to the right atrial wall. This case report suggests that if sufficient endocardial lead is left inside the heart, in dogs undergoing transvenous pacemaker therapy, the redundant lead can become adherent to the tricuspid valve apparatus and cause valvular stenosis.