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Determinants of Late Survival and Reoperation in Patients Undergoing Repair of Subaortic Stenosis
Ishan K Shah, Joseph A. Dearani, Richard C. Daly, *Sameh M. Said, John M. Stulak, Crystal R. Bonnichsen, Hartzell V. Schaff
Mayo Clinic, Rochester, MN

Objective: There is a paucity of data regarding long-term survival and risk of reoperation for membranous subaortic stenosis (SAS). We examined the late outcomes of membranectomy, with versus without concomitant ventricular septal myectomy (SM) on late survival and need for reoperation.
Methods: We identified 141 patients (mean age 32.3 22.3 years; 61% female; 43% children) undergoing surgery for fixed SAS from June 1971 to June 2014. The majority were asymptomatic (94%) and 6% had symptomatic heart failure. Aortic valve regurgitation (AR) was present preoperatively in 71 patients (mild=35%, moderate=12%, severe=3%).
Results: Transaortic exposure was utilized in all patients. Isolated membranectomy was performed in 21% (n=30) and the remainder underwent membranectomy and concomitant left ventricular SM (n=111). The aortic valve was replaced in 13 and repaired in 1. Operative mortality was 0.7% (n=1). Median follow-up was 9.1 years (maximum 40 years; 95% CI 5.3-10.7). One, 10 and 20-year survival was 99%, 93% and 82% respectively (figure 1). Older age at initial repair (HR=1.04[1.01, 1.07], p=0.001) was the only significant predictor of late mortality. There was no significant difference in late survival when patients were stratified by gender, type of procedure or presence of preoperative AR. Postoperative permanent pacemaker was required in 4.2% (n=6/141), and one (1/141) required repair of iatrogenic ventricular septal defect; all these patients were older than 50 years of age and required concomitant SM. Reoperation for recurrent SAS was necessary in 15 patients at a median of 6.9 years (0.66-26.65) after repair; of which 60%(n=9/15) had previous SM. Additionally, 6/15 patients required concomitant aortic valve replacement (AVR) for severe AR. Overall freedom from late reoperation was 3% at 5 and 17% at 10 years. There were no significant risk factors for late reoperation for SAS (figure 2), but the presence of severe AR at the time of initial SAS surgery was a risk factor for reoperation for AVR (p<0.001).
Conclusion: Resection of membranous subaortic stenosis can be performed with low early mortality and excellent late survival. When left ventricular outflow obstruction is caused by a membrane and severe septal hypertrophy, concomitant myectomy is safe, with minimal additional morbidity and similar late outcome compared to patients which need only membrane resection.


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