Severe congenital heart disease has a poor prognosis. Although surgical intervention is required in these cases, open heart surgery has not commonly been applied. Recently, cardiopulmonary bypass has been performed successfully in small-breed dogs and cats. This has led to an increasing success rate for open-heart surgery in the treatment of mitral regurgitation and congenital heart disease. We have reported several successful open heart procedures under cardiopulmonary bypass in small-breed dogs and cats: e.g., surgical techniques for reducing severe pulmonic stenosis, including open and closed patch grafting, pulmonary commissurotomy, and valvotomy; closure of a septal defect; and repair of mitral and tricuspid valves.

Cardiopulmonary Bypass

Right thoracotomy was performed in the 4th intercostal space after intercostal nerve block with bupivacaine hydrochloride. To place a catheter for cardioplegic infusion, the aortic root was elevated, and a 6-0 polyvinylidene fluoride suture purse-string suture placed. The cranial and caudal vena cavae were isolated and encircled with umbilical tape. Purse-string sutures were placed cranial and caudal to the right atrium with 6-0 PVDF sutures. The azygous vein was isolated and occluded with a 3-0 nylon suture. Subsequently, 400 U/kg IV heparin sodium was administered. After 3 minutes, ACT was measured and confirmed to be 4 300 seconds. A 10-Fr CPB cannula was inserted for the arterial line of the CPB. For the venous return line, 14-Fr CPB cannulae were inserted in the cranial and caudal vena cavae, respectively. CPB was achieved using a heart-lung machine with an extracorporeal circuit, a 0.6 m² oxygenator, and a heat exchanger. The CPB circuit was filled with 20% D-mannitol (5 mL/kg), 7% sodium bicarbonate (2 mL/kg), heparin sodium (500 U), and acetate Ringer's solution. A 5-Fr catheter inserted into the aortic root through a preplaced purse-string suture was used to administer cardioplegic solution. After air was removed from the CPB circuit, partial CPB was initiated, and the patient's body temperature was lowered to 28°C. Blood flow was set at 80–120 mL/kg/min by the CPB pump. At this time, the anesthetic was switched from isoflurane inhalation to IV ketamine and propofol. The cranial and caudal vena cavae were then occluded to initiate total CPB. The aorta was occluded using an arterial clamp, and cardioplegic solution was immediately and rapidly infused into the coronary artery to produce diastolic cardio-arrest. The cardioplegic solution was administered at 10 mL/kg every 20 minutes.

Pulmonic Stenosis

Small dogs and cats with severe pulmonic stenosis can be appropriate candidates for surgical correction under cardiopulmonary bypass. We have performed valvotomy with or without biomembrane patch grafting in cases of severe pulmonic stenosis. The subjects comprised dogs and a cat, weight 2.1–4.8 kg, that were diagnosed with severe pulmonic stenosis and right ventricular hypertrophy, with an average preoperative pressure gradient of > 80 mm Hg on echocardiography. The pressure overload caused by the severe pulmonic stenosis was reduced by valvotomy: i.e., open pulmonary valve commissurotomy, with or without biomembrane patch grafting, under cardiopulmonary bypass. The reduced pressure gradient was maintained at about 50 mm Hg at final follow up. Thus, open valvotomy, pulmonary valve commissurotomy, and biomembrane patch grafting were effective in reducing the obstruction in severe pulmonic stenosis in dogs and cat.

References

1.  Fujiwara M, Harada K, Mizuno T, Nishida M, Mizukoshi T, Mizuno M, Uechi M. Surgical treatment of severe pulmonic stenosis under cardiopulmonary bypass in small dogs. J Small Anim Pract. 2012;53(2):89–94.

2.  Uechi M, Harada K, Mizukoshi T, Mizuno T, Mizuno M, Ebisawa T, Ohta Y. Surgical closure of an atrial septal defect using cardiopulmonary bypass in a cat. Vet Surg. 2011;40(4):413–417.

3.  Yamano S, Uechi M, Tanaka K, Hori Y, Ebisawa T, Harada K, Mizukoshi T. Surgical repair of a complete endocardial cushion defect in a dog. Vet Surg. 2011;40(4):408–412.