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.     

Transient high-grade second-degree atrioventricular block secondary to transvenous atrial septal defect occlusion in a dog

A 1.2-year-old male-intact Standard Poodle underwent transvenous placement of an Amplazter™ atrial septal occluder for correction of a large secundum atrial septal defect. Thirty-six hours post-operatively, the dog developed high-grade Mobitz type II second-degree atrioventricular block, which resolved with time and corticosteroid administration by 12 days after the procedure. This case report outlines the observation, treatment, and resolution of high-grade Mobitz type II second-degree atrioventricular block, a known complication of atrial septal occluder placement in humans, not previously reported in veterinary literature.     

Trifoliate left atrioventricular valve with and without intact septal structures in four dogs: echocardiographic findings and surgical repair

Trifoliate left atrioventricular (AV) valve with common atrioventricular junction is considered part of the spectrum of atrioventricular septal defect. This valve morphology is typically associated with defects in the AV septum resulting in communication at the atrial or ventricular level, but has also been described as an isolated defect in the setting of a common AV junction without AV septal defect. Trifoliate left AV valve exhibits a line of apposition between the bridging leaflets that is directed toward the inlet interventricular septum, distinguishing it from isolated mitral valve cleft in which the orientation of the bridging leaflets are toward the left ventricular outflow tract. The echocardiographic findings of four dogs with trifoliate left AV valve are described; two with intact septal structures and two with large ostium primum defects. Three dogs underwent open surgical repair using different approaches depending on the presence or absence of a septal defect. One of these underwent concurrent surgical repair for right AV valve dysplasia. One dog with intact septal structures underwent interventional closure of a concurrent patent ductus arteriosus. Current terminology associated with trileaflet left AV valve malformations is reviewed.     

Presumed congenital Gerbode defect in an American Domestic Shorthair cat

A five-month-old, intact female Domestic Shorthair cat presented to the Kansas State Veterinary Health Center for evaluation of a murmur and exercise intolerance. Physical exam revealed a grade V/VI right, parasternal, holosystolic murmur. On echocardiogram, there was an abnormality in the membranous interventricular septum and tricuspid valve, allowing blood to shunt from the left ventricle to the right atrium. This lesion is consistent with an infravalvular Gerbode defect. The Gerbode defect is a rare, left ventricle-to-right atrial shunt that can be congenital or acquired, and in cats, has only been reported once. At the time of submission, the patient is alive and is maintaining a good quality of life.     

Low-energy ablation of anteroseptal accessory pathways in two dogs

In humans, accessory pathways (APs) in an anteroseptal and midseptal position are often challenging to ablate because of their close proximity with the conduction pathways of the atrioventricular junction. The use of low-energy ablation techniques can be useful to reduce the risk of permanently damaging the atrioventricular node and the His bundle. This report describes the use of low-energy radiofrequency catheter ablation to successfully and permanently ablate anteroseptal APs in two dogs with orthodromic atrioventricular reciprocating tachycardia. In the first dog, a transient first degree atrioventricular block persisted for 30 s after radiofrequency energy delivery. In the second dog, transient paroxysmal atrioventricular conduction block was observed during the procedure but resolved within 3 days. First degree atrioventricular block was again identified 2 months later. In conclusion, anteroseptal APs can be effectively treated by low-energy radiofrequency catheter ablation with minimal and transient damage to the atrioventricular junction.     

Double-outlet right atrium in a 9 year-old cat

Double-outlet right atrium (DORA) is a type of atrioventricular septal defect that is described as an extreme leftward deviation of the lower portion of the interatrial septum, resulting in insertion into the atrial wall left and posterior to the mitral orifice. This rare anomaly, which has been reported in humans and only just recently in cats, was identified by transthoracic echocardiography in a 9 year-old cat that was presented for further evaluation of a tachyarrhythmia and cardiomegaly. This case report describes the diagnostic findings in this cat and summarizes the anatomy, classification and clinical consequences of this rare congenital heart defect.     

Third degree atrioventricular block following non-penetrating chest trauma in a dog

A two-year-old mixed breed dog was referred to the University of Florida Veterinary Medical Teaching Hospital for the management of post traumatic ventricular arrhythmias. Electrocardiography revealed third degree atrioventricular (AV) block. An echocardiogram demonstrated an echogenic, pedunculated mass arising from the caudoventral aspect of the atrial septum. The mass was believed to represent a haematoma or a thrombus associated with trauma to this region of the atrial septum. The patient was managed conservatively; third degree AV block was still pre- sent five days after trauma. The owner of the dog refused specific therapy of the arrhythmia. The patient was discharged and, unfortunately, lost to follow-up. Third degree AV block has not previously been reported following accidental, blunt thoracic trauma in the dog.     

Oculocardiac reflex induced by zygomatic arch fracture in a crossbreed dog

A 3-year-old crossbreed male dog was presented with a history of blunt facial trauma. Skull radiographs showed right zygomatic arch fracture. An electrocardiogram revealed bradycardia, first-degree atrioventricular block and QT prolongation. Standard biochemical profile including electrolytes was normal. Atropine response test (0.04 mg/kg intravenously) restored normal sinus rhythm at a rate of 140 bpm with normal QT and PR intervals. This observation is consistent with oculocardiac reflex secondary to zygomatic arch fracture.     

Permanent Transvenous Pacemaker Implantation in Forty Dogs

Permanent transvenous cardiac pacemakers were implanted in 40 dogs. Electrocardiographic diagnoses included persistent atrial standstill (3 dogs), sick sinus syndrome (8 dogs), and high-grade second-degree or third-degree atrioventricular (AV) block (29 dogs). Thirteen dogs were alive and well 4 to 42 months after pacemaker implantation (mean, 16.9 months). The mean and median survival times of the 26 dogs that died or were euthanatized during the study were 17.9 months and 13 months, respectively. Most of these dogs succumbed to problems unrelated to the arrhythmia and pacemaker implant. One dog was lost to follow-up. Complications associated with permanent transvenous pacemaker implantation included lead dislodgement, infection, hematoma formation, skeletal muscle stimulation, ventricular arrhythmia, migration of the pulse generator, and skin erosion. Lead dislodgement was the most common complication, occurring in 7 of 9 dogs paced using untined electrode leads and in 6 of 30 dogs paced using tined leads. Lead dislodgement did not occur in the only dog paced using an actively fixed endocardial lead. It was concluded that permanent transvenous cardiac pacing is a feasible, less traumatic alternative to epimyocardial pacing in dogs, but that successful use of this technique requires careful implantation technique and anticipation of the potential complications.     

First Description of Partial Atrioventricular Septal Defect in a Rabbit

Congenital heart diseases have rarely been described in rabbits. The purpose of the present case report is to describe the clinical, radiographic, echocardiographic, and pathological features of a partial atrioventricular septal defect in a pet rabbit. A 3-month-old, 380-g male vaccinated pet rabbit was presented for decreased activity, increased respiratory rate and effort, anorexia, and decreased fecal output of 2 days duration. Total body radiographic images revealed severe cardiomegaly associated with enlarged caudal pulmonary vessels and increased interstitial to alveolar lung pattern. Echocardiographic imaging showed evidence of distended heart chambers, abnormal flow through the atria, and mitral valve regurgitation. The rabbit was treated with furosemide and an angiotensin-converting enzyme inhibitor but rapidly deteriorated and died. Necropsy confirmed the dilation of both ventricles and the presence of a partial atrioventricular septal defect associated with an ostium primum atrial septal defect just over the tricuspid valve and the mitral valve.     

Suspected sequential left atrial ruptures in a dog with myxomatous mitral valve disease

An 11-year-old mixed breed dog was presented with exercise intolerance and syncope. At admission, transthoracic echocardiography revealed myxomatous mitral valve disease (MMVD) associated with severe left atrial (LA) enlargement and moderate anechoic pericardial effusion with a hyperechoic density suggestive of a thrombus. Rupture of the LA free wall secondary to MMVD was suspected, and medical therapy with furosemide and pimobendan was initiated. After one month, recheck echocardiography showed mild anechoic pericardial effusion and an acquired atrial septal defect with a left-to-right intracardiac shunting flow. In light of the dog's history, the latter finding was suspected to be secondary to a further rupture of the LA wall due to MMVD, this time affecting the interatrial septum. The images described here allow us to suspect that sequential LA wall ruptures developed over time in the same subject affected by MMVD, a clinical presentation not previously described in veterinary medicine.     

Transvenous pacemaker placement in a dog with atrioventricular block and persistent left cranial vena cava

The case reported herein describes the placement of a permanent transvenous pacemaker in an older dog with a previously undiagnosed persistent left cranial vena cava (PLCVC) and recent onset symptomatic third-degree atrioventricular (AV) block. On presentation the dog was found to have atrial flutter and third-degree AV block and echocardiography demonstrated evidence of chronic valvular disease and pulmonary arterial hypertension. The persistent left cranial vena cava was discovered via angiography when difficulties were encountered with pacemaker placement. Successful right ventricular pacing necessitated passage of the lead through the coronary sinus. The attendant complications in pacemaker placement in the presence of a PLCVC are well-described in man but, to the authors' knowledge, have not been described in companion animals.     

Clinical and electrocardiographic presentations of transient trifascicular block in three cats

This report describes transient trifascicular block in three cats presented with lethargy and inappetence, and elevated cardiac troponin I concentrations.The electrocardiogram (ECG) of cat 1 showed a sinus rhythm with pronounced first-degree atrioventricular (AV) block, right bundle branch block, and left anterior fascicular block. The ECG of cat 2 showed truncular left bundle branch block alternating with left anterior fascicular block coupled with prolonged PR intervals, second-degree heart block, and paroxysmal third-degree AV block. The ECG of cat 3 showed first-degree AV block with concomitant right bundle branch block. The diagnosis of trifascicular block was made when paroxysmal third-degree AV block was documented.All cats recovered with medical management within weeks. Each cat resumed a sinus rhythm. Elevated cardiac troponin I concentrations suggested myocarditis that improved.     

Malignant pheochromocytoma presenting as a bradyarrhythmia in a dog

Objective: To describe a case of atrioventricular block and syncope secondary to systemic hypertension in a dog with malignant pheochromocytoma. Case Summary: A 13‐year‐old spayed female mixed‐breed dog presented following an acute onset of collapse. The dog was hypertensive and had paradoxical high‐grade second‐degree atrioventricular block with concurrent syncope. Initial emergent therapy included a nitroprusside infusion for the systemic hypertension and vagolytic therapy for the bradyarrhythmia. A left adrenal mass was seen on abdominal ultrasound and was further characterized by MRI. Following medical stabilization with phenoxybenzamine and propantheline, a left adrenalectomy was performed. Histological diagnosis was consistent with a malignant pheochromocytoma. Following tumor removal there has been no further hypertension, atrioventricular block or syncope. Unique information provided: This is the first documented case of a malignant pheochromocytoma presenting as syncope secondary to hypertension induced atrioventricular block.     

Transcatheter Atrial Septal Defect Closure with the AMPLATZER® Atrial Septal Occluder in 13 Dogs: Short- and Mid-Term Outcome

Background: Transcatheter atrial septal defect (ASD) closure in the dog was first reported in 2005.
Objectives: Describe the technique and both short- and mid-term outcome of transcatheter ASD closure with the Amplatzer^® atrial septal occluder (ASO).
Animals: Thirteen client-owned dogs with ASD.
Methods: Records of the initial 13 dogs in which transcatheter ASD closure was attempted at Texas A&M University were reviewed.
Results: All dogs had hemodynamically relevant septum secundum ASD. Two dogs had concurrent congenital abnormalities. ASOs were deployed in 13 dogs and released in 12. Eleven were released by a right jugular approach and 1 by a transatrial approach through a right lateral thoracotomy. Transthoracic echocardiographic estimates of ASD size were 14.0 ± 5.4 mm (mean ± 1 standard deviation) with a range of 7–22 mm. Accidental right atrial release occurred in 1 dog and embolization after release occurred in 2 dogs. Transcatheter ASD closure was successful in 10 dogs. Transthoracic color Doppler echocardiography the day after ASD closure indicated complete occlusion in 5 dogs, trivial to mild residual shunting in 4 dogs, and moderate residual shunting in 1 dog. Follow-up echocardiograms (mean of 12.4 ± 7.4 months postprocedure) were available for 9 dogs. There was no residual ASD shunting in 6 dogs. In 3 of the 5 dogs with postoperative residual shunting it was judged to be decreased and hemodynamically unimportant relative to the dogs' postoperative evaluations. The mean length of event-free survival in the 10 dogs that underwent successful transcatheter ASD closure was 22.2 ± 10.2 months.     

Surgical Treatment of a Canine Intranasal Meningoencephalocele

Objective— To report the clinical signs, diagnosis, and surgical treatment of an intranasal meningoencephalocele in a dog.
Study Design— Case report.
Animal— Female Border collie, 5 months old.
Methods— A right intranasal meningoencephalocele was identified by computed tomography and magnetic resonance imaging.
Results— The lesion was approached by a modified transfrontal craniotomy. Surgical closure of the defect at the level of the cribriform plate and removal of extruded brain tissue resulted in regression of lacrimation and coincided with absence of seizuring. Treatment with phenobarbital was gradually reduced and stopped at 7 months after surgery. At 28 months the dog remained free of seizures.
Conclusion— Meningoencephalocele, although rare, can cause seizures in dogs and can be treated surgically.
Clinical Relevance— A transfrontal craniotomy with excision of the meningoencephalocele and closure of the defect can be an effective treatment for an intranasal meningoencephalocele in dogs.     

A novel internal abdominal oblique muscle flap to close a major abdominal wall defect

This report describes a novel technique for abdominal wall reconstruction using an internal abdominal oblique muscle flap in an Australian kelpie. En bloc resection of a chondrosarcoma and biopsy scar centred on the 13th rib was performed to include full thickness thoracic wall (12th rib, extending caudally) and lateral abdominal wall (including the vascular pedicle of the external abdominal oblique muscle). The diaphragm was advanced to close the thorax. A flap using the caudal internal abdominal oblique muscle with the base dorsally was elevated and rotated 90° to fill the dorsal defect. The ventral defect was closed using the composite ventral abdominal muscles. The skin was closed primarily. The dog developed a self-resolving seroma. Twelve months postoperatively, the dog was able to engage in agility competitions. A viable muscle flap using the internal abdominal oblique muscle provides a useful alternative to previously described techniques for autogenous closure of a large abdominal wall wound.     

Clinical remission of idiopathic hypereosinophilic syndrome in a Rottweiler

Idiopathic hypereosinophilic syndrome (HES) is a rare syndrome for which Rottweilers appear to over-represent the canine cases. A 6-month-old female entire Rottweiler presented with seizures following a traumatic incident. The dog was identified as having a marked, sustained eosinophilia and investigations did not identify an underlying cause. Concurrently, the dog had chronic eosinophilic hepatitis with impaired liver function and mesenteric eosinophilic lymphadenitis. The dog went on to have spontaneous resolution of HES and normal liver function was subsequently documented. To date, the dog is still alive, more than 4 years after initial presentation. The diagnosis of idiopathic HES in Rottweilers may not carry a poor prognosis and the condition may spontaneously resolve, even in cases with documented organ damage.     

Successful use of an acceleration rate response pacemaker with a transvenous steroid-eluting screw-in lead for third-degree atrioventricular block in a labrador retriever

Permanent pacemakers are commonly used in veterinary practice and can have a dramatic effect on the treatment of heart block. A Labrador Retriever dog suffering from exercise intolerance secondary to third degree atrioventricular block was treated with a new pacemaker system. A steroid-eluting screw-in type lead that has the advantage of being more fixed to the myocardial wall without increasing the pacing threshold was used. The heart rate was regulated with an acceleration sensing pacemaker generator that included several automatic modulation systems. Nineteen months after implantation, the dog has a normal level of activity. The present case suggests that this pacemaker design may offer important advantages for canine patients.