Surgical treatment of discrete and tunnel subaortic stenosis. Late survival and risk of reoperation.

BACKGROUND: Although membranectomy, with or without septal myotomy or myectomy, has been the accepted method for treatment of fixed subaortic stenosis, controversies remain regarding operative methods and uncertainties regarding recurrence of subaortic obstruction and development of aortic insufficiency after repair.

METHODS AND RESULTS: To determine late survival and risk of reoperation, we reviewed 169 patients who, between 1957 and 1992, had repair of discrete (n = 108) and tunnel (n = 61) subaortic stenosis. One hundred fifty-four patients had their primary operation for subaortic stenosis at the Mayo Clinic, and 15 patients had their primary operation elsewhere. Among patients having initial repair at our institution, membranectomy was performed in 52 patients (33.8%), membranectomy plus myotomy in 24 patients (15.6%), membranectomy plus myectomy in 71 patients (46.1%), myectomy plus a Konno-Rastan procedure in 5 patients (3.2%), and myectomy plus a modified Konno-Rastan procedure in 2 patients (1.3%). For all patients, early mortality was 4.7% (2.7% since 1961), and during follow-up extending to 29 years, there have been 16 late deaths. Twenty-six patients underwent a second or third operation for recurrent left ventricular outflow obstruction, including 11 of the 154 who had their primary operation at the Mayo Clinic (7.1%). Among the 21 patients who had a discrete lesion at initial repair and required reoperation, 19 (92%) were noted to have tunnel obstruction at reoperation. At late follow-up, the left ventricular outflow tract gradient was higher in patients with tunnel versus discrete obstruction (33 +/- 5 versus 24 +/- 17 mm Hg, P < .04), and 10-year survival was poorer (79% versus 91%, P < .02). Ten-year survival was worse in patients with tunnel lesions and associated cardiac anomalies versus those with isolated tunnel subaortic stenosis (64% versus 92%, P < .005). Some degree of aortic valve insufficiency was seen at late follow-up in 26% of patients, but in most cases this was mild. For patients with discrete subaortic stenosis, risk of late aortic insufficiency was 38.6% after isolated membranectomy, 27.8% after membranectomy and myotomy, and only 7.3% after membranectomy and myectomy (P < .004). Progression of aortic insufficiency requiring aortic valve replacement occurred in only 6 patients.

CONCLUSIONS: Our results support the use of myectomy in conjunction with membranectomy for discrete subaortic stenosis. For restenosis and tunnel obstruction, more complete relief of subaortic stenosis by extended resection or a modified or classical Konno-Rastan procedure may improve late survival and reduce the incidence of recurrent subaortic stenosis and late aortic valve insufficiency.