Resection of subvalvular aortic stenosis. Surgical and perioperative management in seven dogs.

Open heart surgery was performed during cardiopulmonary bypass (CPB) to surgically correct subvalvular aortic stenosis in seven dogs. After initiation of total CPB, cardiac arrest was induced by antegrade and retrograde administration of blood cardioplegia. The subvalvular fibrous stenosis was resected through a transverse aortotomy. Intraoperatively and postoperatively, dobutamine, nitroprusside, lidocaine, blood(-products), and crystalloid solutions were used to manage hypotension and optimize cardiac index. Aortic cross-clamp time varied from 73 to 166 minutes, and duration of CPB varied from 130 to 210 minutes. Iatrogenic incision into the mitral valve in two dogs was the most significant intraoperative complication. Postoperative complications included: hypoproteinemia (n = 7), premature ventricular depolarization (n = 6), increased systemic vascular resistance index (n = 5), increased O2 extraction (n = 3), pulmonary edema (n = 2), and decreased cardiac index (n = 1). All seven dogs were discharged alive and in stable condition. Six dogs are alive and in stable condition after a mean follow up of 15.8 months. This is the first detailed report of CPB in a series of clinical veterinary patients. Using the techniques described in this paper, open heart surgery of considerable duration can be performed successfully in dogs with significant myocardial hypertrophy and endomyocardial fibrosis secondary to subvalvular aortic stenosis.