Challenges of cardiopulmonary bypass-a review of the veterinary literature.

Cardiopulmonary bypass (CPB) has been used in veterinary medicine in experimental surgery and to address congenital and acquired diseases. We review the veterinary literature and expose common challenges of CPB in dogs and cats. Specifically, we describe the most specific elements of this technique in veterinary patients. The variety in animal size has made it difficult to standardize cannulation techniques, oxygenators, and priming volumes and solutions. The fact that one of the most common cardiovascular disorders, mitral valve disease, occurs predominantly in small dogs has limited the use of bypass in these patients because of the need for small, low prime oxygenators and pumps that have been unavailable until recently. Coagulation, hemostasis, and blood product availability have also represented important factors in the way CPB has developed over the years. The cost and the challenges in operating the bypass machine have represented substantial limitations in its broader use.

Caudal vena cava kinking in dogs with ascites.

A 9-year-old dog with spontaneous ascites was found to have hepatic vein distension and a tortuous vena cava on abdominal ultrasound. In right lateral recumbency, the caudal vena cava crossed the diaphragm and became kinked before entering into the right atrium. Following this observation, we performed an experimental study in a normal dog to determine whether kinking of the caudal vena cava could be the result and not the cause of ascites. Ascites was induced using warm saline injected through a needle inserted into the abdominal cavity. Venograms were collected from different body positions, under four conditions: before and after a total of one, two and 3 liters of saline had been injected. Caudal vena cava kinking was observed in the experimental dog after 2 liters of fluid had been injected. Vena cava obstruction may cause ascites, but we found that sometimes caudal vena cava kinking can be the result and not the cause of the peritoneal effusion.

Congenital coronary-pulmonary arterial shunt in a German shepherd dog: diagnosis and surgical correction.

BACKGROUND: A 10 week-old intact female German shepherd dog was examined because of a heart murmur. METHODS: An echocardiogram revealed an extracardiac left-to-right shunt. An angiogram identified shunting between the aorta and the pulmonary artery in an unusual location. RESULTS: Thoracotomy was performed to better identify and correct the lesion; a tubular shunt between the left coronary artery and the pulmonary artery was found and ligated in a closed-heart procedure. The murmur resolved immediately upon ligation and the dog's heart size normalized over a period of several months after surgery. CONCLUSION: In the dog, surgical correction of a coronary artery-pulmonary artery shunt can be performed without complications and can be associated with reversal of cardiac remodeling.

Septicemia in a young dog following treatment of patent ductus arteriosus via coil occlusion.

CASE DESCRIPTION-A 12-week-old female English Springer Spaniel was evaluated for lethargy, vomiting, and pyrexia 1 week after treatment of patent ductus arteriosus (PDA) via coil occlusion. CLINICAL FINDINGS-Test results were consistent with septicemia, and the assumption was made that the PDA occlusion coils were infected. Radiography revealed partial migration of the coil mass into the pulmonary artery and signs of congestive heart failure. TREATMENT AND OUTCOME-After successful treatment of the septicemia and heart failure, surgical removal of the coils and resection of the PDA were undertaken. Although the coil that embolized to the pulmonary vasculature was left in place, the dog's clinical signs resolved. CLINICAL RELEVANCE-This case highlights the fact that as PDA coil occlusion devices become more widely used in dogs, practitioners must be prepared to treat implant infections aggressively, with both medical and surgical interventions if necessary.

Use of a jugular vein graft in a modified Blalock-Taussig procedure in dogs.

OBJECTIVE: To determine whether autologous jugular veins provide functional grafts with high 30-day patency rates in an experimental model of systemic-to-pulmonary shunting performed with a modified Blalock-Taussig procedure. ANIMALS: 15 healthy Beagles. PROCEDURE: A segment of the left jugular vein was implanted between the left subclavian and pulmonary arteries. Echocardiograms were obtained prior to surgery, at day 4 to 7, and at day 30 after surgery. Selective angiograms were performed immediately after surgery and on day 30. Oximetric shunt calculations were made via terminal angiography prior to euthanasia. Gross and histologic evaluations of the grafts were conducted. RESULTS: Grafts were patent in 12 of 15 dogs 30 days after surgery as assessed via auscultation, color Doppler ultrasonography, angiography, and histologic examination. Echocardiographic analysis revealed compensatory eccentric left ventricular hypertrophy. Mean pulmonary-to-systemic flow ratio was 1.5:1. Histologic evidence of endothelialization of the anastomotic sites and vein graft arterialization was detectable at 30 days. CONCLUSIONS AND CLINICAL RELEVANCE: Autologous jugular vein grafts were effectively used to create a systemic-to-pulmonary shunt by use of a modified Blalock-Taussig procedure. High patency, ready accessibility, low cost, and theoretical adaptative remodeling during patient growth make autologous jugular vein grafts a valuable alternative to synthetic materials.

Atrioventricular nodal ablation and His-bundle pacing: an acute canine model for proarrhythmic risk assesment.

INTRODUCTION: QT interval prolongation following drug exposure is considered a marker for increased risk of drug-induced arrhythmias. QT interval measurements are common components of the safety pharmacology assessment of new therapeutic compounds but are potentially confounded by concurrent changes in heart rate that also alter QT intervals. We describe an anesthetized canine model of AV dissociation with His-bundle pacing that overcomes the confounding effects of a change in heart rate. METHODS AND RESULTS: Transvenous radiofrequency ablation of the AV node was performed in isoflurane-anesthetized dogs and followed by open chest implantation of bipolar pacing electrodes in the vicinity of the His bundle. Pace rates were adjusted from 50 to 190 in steps of 20 beats/min, holding each step for 30 seconds. At each paced rate, QT intervals were measured manually to the nearest 1 ms to construct paced QT interval-heart rate (QT-HR) relationships. Paired QT-HR relationships using identical ascending ramps of pace rates were compared to paired QT-HR relationships with an ascending and descending pace ramp to evaluate short-term reproducibility and hysteresis effects. For proof of concept, an additional QT-HR relationship was constructed in three dogs after intravenous administration of a compound known to alter QT intervals: one dog received terfenadine (0.48 mg/kg bolus followed by 0.017 mg/kg/min infusion), one dog received quinidine (20 mg/kg), and the third dog received sotalol (1 and 3 mg/kg). Substantial inter-dog variation was found for QT-HR, although short-term reproducibility was high within one dog (average absolute difference for paired ascending ramps < 5 ms). QT intervals measured during descending paced ramps were generally lower than the value for the corresponding paced rate on an ascending ramp. This hysteretic effect was small, averaging < 7 ms over the entire ramp. All test compounds prolonged QT intervals and shifted the QT-HR relationship upward. Maximal QT prolongation was 30 ms for terfenadine, 50 ms for quinidine, and 59 ms for sotalol. CONCLUSION: AV nodal ablation and His-bundle pacing provide a sensitive animal model to identify acute effects of test compounds on indices of myocardial repolarization such as the QT interval. The model is devoid of confounding effects of changing heart rates while enabling identification of effects of drugs over a wide range of controlled rates.