Surgical Correction of Subvalvular Aortic Stenosis Using Cardiopulmonary Bypass in a Dog

High-pressure balloon dilation in a dog with supravalvular aortic stenosis

A 6-month-old female intact Goldendoodle was presented for diagnostic work up of a grade IV/VI left basilar systolic heart murmur. An echocardiogram was performed and revealed a ridge of tissue distal to the aortic valve leaflets at the sinotubular junction causing an instantaneous pressure gradient of 62 mmHg across the supravalvular aortic stenosis and moderate concentric hypertrophy of the left ventricle. Intervention with a high-pressure balloon dilation catheter was pursued and significantly decreased the pressure gradient to 34 mmHg. No complications were encountered. The patient returned in 5 months for re-evaluation and static long-term reduction in the pressure gradient was noted.

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.

Anesthetic management of an off-pump open-heart surgery in a dog

OBSERVATIONS

A 9 year-old, 40 kg, female spayed Bouvier des Flandres was anesthetized for surgical removal of an intra-cardiac mass. Pre-anesthetic work-up included thoracic radiographs, which revealed moderate pleural effusion, and cardiac ultrasound, which identified a mass attached to the wall of the right ventricular outflow tract (RVOT). The mass caused dynamic obstruction of the RVOT during systole. The dog was pre-medicated with intravenous (IV) hydromorphone (0.05 mg kg(-1)). Following pre-oxygenation, anesthesia was induced with ketamine (3.75 mg kg(-1), IV) and diazepam (0.18 mg kg(-1), IV). Anesthesia was maintained with isoflurane in oxygen, an intravenous constant rate infusion (CRI) of fentanyl (10-30 microg kg(-1) hour(-1)) and a CRI of lidocaine (50-200 microg kg(-1) minute(-1)). A right lateral thoracotomy was performed. The heart was stopped transiently with a cold cardioplegic solution for 7.83 minutes to allow the removal of the mass through an open-heart procedure. No cardiopulmonary bypass was used. The heart was successfully restarted after cardiopulmonary resuscitation with internal cardiac massage and internal defibrillation. The dog recovered uneventfully from anesthesia without any apparent neurological sequelae. Post-operative analgesia consisted of intercostal nerve blocks with bupivacaine, CRIs of fentanyl (2-5 microg kg(-1) hour(-1)) and lidocaine (40 microg kg(-1) minute(-1)) and with oral meloxicam (0.1 mg kg(-1)). Five days following surgery, the dog was discharged from the hospital. Histopathology and immunohistochemistry of the mass identified an ectopic thyroid carcinoma.

CONCLUSIONS

This case showed the feasibility of whole body hypothermia and using a cold cardioplegic solution to induce cardiac arrest for a short open-heart procedure.

Short-Term Performance of Mitral Valve Replacement with Porcine Bioprosthetic Valves in Dogs

Porcine bioprosthetic valves cross-linked with glutaraldehyde and polyepoxy compound were newly developed for mitral valve replacement (MVR) in dogs. Five beagle dogs were performed a left thoracotomy and underwent MVR using the porcine bioprosthetic valves during cardiopulmonary bypass (CPB). A vein catheter inserted into right atrium and a vent catheter inserted into the right ventricle to drain. The hemodynamic conditions of CPB were excellent during surgery. The left atrial pressure was measured before and after MVR; there was no significant difference and it was normal. Thrombosis and the prosthetic valve regurgitation were not observed one week after MVR. Pressure half time (PHT) prolonged significantly (P<0.05) from 31.40 +/- 4.0 msec presurgery to 99.20 +/- 19.4 msec at seven days after MVR, although it indicated the normal range as the bioprosthetic valve. The symptom of the prosthetic valve failure was not observed. This study indicated that the MVR using porcine bioprosthetic valves under CPB might have been effective in dogs as a short-term evaluation.

An Experimental Study of Apico-Aortic Valved Conduit (AAVC) for Surgical Treatment of Aortic Stenosis in Dogs

A new valved conduit was developed using a canine aortic valve. The bioprosthetic valve was fixed with glutaraldehyde and epoxy compound (Denacol-EX313/810). A vascular graft composed of ultra-fine polyester fiber (10 mm in diameter, 200 mm in length) was used. Four dogs underwent apico-aortic valved conduit (AAVC) implantation and aortic banding (bypass group, BG), while another 4 dogs underwent aortic banding without AAVC implantation (control group, CG). Cardiac catheterization and angiocardiography were performed for assessment of hemodynamics 2 weeks and 6 months after surgery. Left ventricular systolic pressure, left ventricular end-diastolic pressure and the left ventricular-aortic pressure gradient differed significantly (P<0.01) between the BG and CG dogs. Left ventricular angiocardiography showed patency of the valved conduit in all the BG dogs. Echocardiography was performed before and 2, 4 and 6 months after surgery, and showed that while pressure overload caused concentric myocardial hypertrophy in the CG dogs, the left ventricle dilated eccentrically in the BG dogs. Furthermore, relief of left ventricular pressure overload by AAVC was maintained.