OPEN RESECTION FOR SUBVALVULAR AORTIC-STENOSIS IN DOGS

Objective-To describe the surgical technique for open resection of con genital subvalvular aortic stenosis in dogs and to determine outcome o f dogs under going 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, a nd cold cardioplegia solution was administered. The aortic root then w as opened with a curvilinear incision. A subvalvular discrete fibrous ring was resected in all dogs. Septal myectomy was performed simultane ously on 11 dogs. Results-15 of 17 dogs survived the operation and wer e discharged from the hospital. Mean +/- SD maximal instantaneous aort ic systolic pressure gradient measured by means of Doppler echocardiog raphy was significantly reduced from 119 +/- 42 mm of Hg before surger y to 41 +/- 10 mm of Hg 12 months after surgery. Despite substantial r eduction 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 greater than or equal to 180 mm o f Hg and ventricular tachycardia before surgery. Eleven dogs were stil l alive between 1 and 48 months after surgery. Clinical Implications-T he procedure resulted in substantial reductions in systolic pressure g radients in dogs with severe congenital subvalvular aortic stenosis. H owever, some dogs with severe aortic stenosis died suddenly after surg ery. Thus, this surgery should not be considered curative. Proof of a survival benefit in dogs undergoing this surgery will have to await lo nger term follow-up.