Influence of open surgical correction on intermediate-term outcome in dogs with subvalvular aortic stenosis: 44 cases (1991-1998)

Abstract

Objective - To compare outcome and intermediate-term survival for dogs undergoing open surgical correction of subvalvular aortic stenosis (SAS) with those for dogs with SAS that did not undergo surgery. Design - Retrospective study. Animals - 44 dogs with congenital SAS. Procedure - Maximum instantaneous systolic pressure gradients were determined by use of Doppler echocardiography. Cardiopulmonary bypass and open surgical correction of SAS (membranectomy with or without septal myectomy) was performed in 22 dogs, whereas 22 dogs did not undergo surgical correction. Cumulative survival was compared between surgical and nonsurgical groups, using Kaplan-Meier nonparametric analysis and a Mantel-Cox log-rank test Results - Initial systolic pressure gradients were not significantly different for dogs undergoing surgery (128 ± 55 mm Hg), compared with those that did not undergo surgery (117 ± 57 mm Hg). Systolic pressure gradients were significantly decreased after surgery in dogs that underwent surgery (54 ± 27 mm Hg). Cumulative survival was not significantly different between dogs in the surgical and nonsurgical groups. Censoring surgery-related mortality in the analysis still did not reveal a significant difference in cumulative survival between the surgical and nonsurgical groups. Conclusions and Clinical Relevance - Despite reductions in the systolic pressure gradient and possible associated improvement in exercise tolerance, a palliative benefit on survival was not documented in dogs undergoing surgery for SAS.