Open resection for subvalvular aortic stenosis in dogs

Abstract

Objective - To describe the surgical technique for open resection of congenital subvalvular aortic stenosis in dogs and to determine outcome of dogs undergoing the procedure. Design - Uncontrolled clinical trial. Animals - 17 dogs with congenital discrete subvalvular aortic stenosis. Procedure - Dogs were placed on cardiopulmonary bypass by catheterizing the femoral artery and both vena cavae. The aorta was cross clamped, and cold cardioplegia solution was administered. The aortic root then was opened with a curvilinear incision. A subvalvular discrete fibrous ring was resected in all dogs. Septal myectomy was performed simultaneously on 11 dogs. Results - 15 of 17 dogs survived the operation and were discharged from the hospital. Mean ± SD maximal instantaneous aortic systolic pressure gradient measured by means of Doppler echocardiography was significantly reduced from 119 ± 42 mm of Hg before surgery to 41 ± 10 mm of Hg 12 months after surgery. Despite substantial reduction in the systolic pressure gradient, 4 of 15 dogs died suddenly between 7 days and 30 months after surgery. Three of the 4 dogs that died suddenly had pressure gradients > 180 mm of Hg and ventricular tachycardia before surgery. Eleven dogs were still alive between 1 and 48 months after surgery. Clinical Implications - The procedure resulted in substantial reductions in systolic pressure gradients in dogs with severe congenital subvalvular aortic stenosis. However, some dogs with severe aortic stenosis died suddenly after surgery. Thus, this surgery should not be considered curative. Proof of a survival benefit in dogs undergoing this surgery will have to await longer term follow-up.