Successful high-resolution three-dimensional electroanatomical mapping and radiofrequency catheter ablation of a posteroseptal accessory pathway in a dog using CARTO 3.

A one-year-and-seven-month-old, 28 kg, male castrated crossbreed dog was presented for supraventricular tachycardia causing recurrent episodes of anorexia and lethargy. Sotalol (2.2 mg/kg q12 h) reduced the frequency of symptomatic episodes but did not provide full relief. Three-dimensional electroanatomical mapping was performed at the Ghent University Small Animal Teaching hospital using the CARTO 3. Right atrial activation mapping identified the earliest atrial activation right posteroseptal, near the tricuspid annulus. Fast retrograde ventriculoatrial conduction during tachycardia and extrastimulus testing confirmed the presence of a concealed right posteroseptal accessory pathway. Six radiofrequency catheter ablation applications were delivered, and tachycardia remained uninducible. The dog recovered well from the procedure. Sotalol was stopped three weeks later, and no more clinical signs were noted by the owner. Repeated 24-hour electrocardiography monitoring on day one and at one, three, and 12 months after the procedure showed no recurrence of tachycardia.

Evaluation of the use of a heparin dose-response test in dogs to determine the optimal heparin dose during intravascular procedures and assessment of the in vitro heparin response in healthy dogs.

BACKGROUND: No guidelines for administering and monitoring anticoagulants intraprocedurally are currently available in dogs, despite the prevalence of procedures necessitating systemic anticoagulation with heparin. OBJECTIVES: To evaluate an activated clotting time (ACT)-based heparin dose-response (HDR) test to predict the individual required heparin dose in dogs during intravascular procedures, and to investigate both the in vitro heparin - ACT and in vitro heparin - factor anti-Xa activity (anti-Xa) relationships in dogs. METHODS: Blood was collected from eight healthy beagles undergoing a cardiac procedure and utilised to establish baseline ACT and for in vitro evaluation. Subsequently, 100 IU/kg heparin was administered intravenously (IV) and ACT was remeasured (HDR test). The required heparin dose for an ACT target response ≥300 s was calculated for each individual and ACT was remeasured after administration of this dose. For in vitro testing, a serial heparin blood dilution (0-0.5-1-2-4 international unit (IU)/mL) was prepared and ACT and anti-Xa were determined using whole blood and frozen plasma, respectively. RESULTS: The HDR test overestimated the required heparin dose in 3/7 dogs. In vitro, ACT and anti-Xa increased significantly with increasing blood heparin concentration. Heparin - ACT was nonlinear in 4/8 dogs at heparin concentrations >2 IU/mL, whereas heparin - anti-Xa remained linear throughout the tested range. CONCLUSIONS: The HDR test poorly estimated the required heparin dose in dogs. This is most likely attributed to a nonlinear heparin - ACT relationship, as observed in vitro. Anti-Xa is a promising alternative for ACT; however, unavailability as a point-of-care test and lack of in vivo target values restrict its current use.

Pulmonary arteriovenous malformation and a concurrent patent ductus arteriosus in a Doberman.

A 7-week-old male Doberman presented with tachypnea, dyspnea and a VI/VI, left cranial, continuous heart murmur. Thoracic radiographs revealed severe left-sided cardiomegaly, presence of a rounded soft tissue opacity in the caudodorsal aspect of the thoracic cavity and signs of left-sided congestive heart failure. Clinical signs of heart failure were medically controlled. Echocardiography and computed tomography demonstrated a left-to-right shunting patent ductus arteriosus (PDA) in combination with a right-to-left shunting pulmonary arteriovenous malformation (PAVM) between the right main pulmonary artery and the right caudal pulmonary vein. Arterial blood gasses revealed mild hypoxemia. Transcatheter occlusion of the PDA using an Amplatz Canine Duct Occluder was performed. Four months post-operatively, echocardiography showed normal cardiac size and function with complete PDA closure. Thoracic radiographs revealed absence of the rounded opacity and resolution of cardiomegaly and vascular congestion. The PAVM was no longer visualized on repeated computed tomography and the arterial blood gasses were within normal limits. A PAVM connecting a pulmonary artery to a pulmonary vein has only rarely been reported in dogs. This report describes the presence of a congenital PAVM in combination with a PDA in a dog, which has not been previously reported in veterinary medicine.

Surgical correction of an infundibular pulmonic stenosis and ventricular septal defect in a Shetland Sheepdog.

A four-month-old male Shetland Sheepdog presented with exercise intolerance. Physical examination revealed an IV/VI left cranial systolic heart murmur. Echocardiography showed a severe infundibular pulmonic stenosis and a concomitant restrictive ventricular septal defect. As clinical signs of congestive right-sided heart failure worsened and were refractory to medical treatment, surgical correction was advised. Via sternotomy, with cardiopulmonary bypass and cardioplegic cardiac arrest, ventricular septal defect closure and resection of the stenotic infundibular band were performed through right ventriculotomy, followed by patch enlargement. Postoperative recovery was uneventful and echocardiography showed complete resolution of the stenosis and successful closure of the ventricular septal defect. Follow-up echocardiography revealed restenosis after seven weeks and recurrence of right-sided heart failure three months postoperatively. Stenting of the restenosis was attempted via a hybrid procedure with sternotomy and direct transventricular approach. The dog developed fatal ventricular fibrillation during stent deployment. This is the first dog in which surgical right ventricular patch enlargement under cardiopulmonary bypass is reported for the treatment of a primary infundibular pulmonic stenosis.

Three-dimensional electroanatomical mapping for guidance of pulmonary vein isolation as treatment for persistent atrial fibrillation in a dog.

A two-year and four-month, male German Shepherd was referred for exercise intolerance and panting. Irregular heart auscultation (250 beats per minute (bpm)) and pulse deficits were noted on physical exam. Electrocardiogram (ECG) showed irregular, narrow-QRS tachycardia without P waves compatible with coarse atrial fibrillation (AF). A 24-h ECG showed sustained AF (mean ventricular response rate 92 bpm). Echocardiography showed no structural abnormalities. Given the young age and presence of AF-related symptoms, rhythm control was preferred. Transthoracic electrical cardioversion was successfully performed six weeks later but AF recurred within 24-h. Sotalol was started but discontinued due to poor tolerance and AF persisted. Seven months after AF diagnosis, radiofrequency catheter ablation (RFCA) aiming for pulmonary vein isolation was performed under general anaesthesia. After transseptal puncture, three-dimensional electroanatomical mapping of the left atrium was performed. Point-by-point pulmonary vein isolation was achieved by RFCA. Seventy-eight RFCA lesions were placed in the left atrium encircling the three pulmonary vein ostia followed by electrical cardioversion. No complications occurred and the dog was discharged with amiodarone. In the immediate post-operative phase, there was recurrence of persistent AF requiring electrical cardioversion. Furthermore, at one month after the ablation, the dog experienced a single and transient paroxysm of AF. Since then, stable sinus rhythm (SR) was retained on daily ECG monitoring at home and confirmed by 24-h ECG three months post-operatively. Amiodarone was stopped subsequently. At the time of writing (one year post-operative), the dog remains in SR with normal exercise tolerance.

Feasibility and safety of three-dimensional electroanatomical cardiac mapping, mapping-guided biopsy and transseptal puncture in dogs.

Three-dimensional electroanatomical mapping (3D EAM) has expanded radiofrequency catheter ablation applications in humans to almost all complex arrhythmias and has drastically reduced fluoroscopy use, yet its potential in dogs is poorly investigated. The objectives of the current study were to assess the feasibility and safety of 3D EAM of all four heart chambers, 3D EAM-guided biopsies and transseptal puncture in dogs. Eight healthy purpose-bred Beagle dogs. Electroanatomical mapping was performed under general anaesthesia during sinus rhythm using a 22-electrode mapping catheter. Left heart catheterisation was achieved by either retrograde transaortic access (n = 4) or transseptal puncture (n = 4). Successful 3D EAM of the right atrium and ventricle was achieved in all dogs at a median time of 33 (13-40) min and 17 (3-52) min, respectively. Left atrial and ventricular 3D EAM was successful in six and seven dogs, at a median time of 17 (4-27) min and 8 min (4-19 min), respectively. Complications requiring intervention occurred in one dog only and were a transient third degree atrioventricular block and pericardial effusion following transseptal puncture, which was treated by pericardiocentesis. All dogs recovered uneventfully. Fluoroscopy time was limited to a median of 7 min (0-45 min) and almost exclusively associated with transseptal puncture. Three-dimensional EAM of all cardiac chambers, including mapping-guided biopsy and transseptal puncture is feasible in small dogs. Complications are similar to those reported in human patients. This suggests a potential added value of 3D EAM to conventional electrophysiology in dogs with arrhythmias.