Membranous subaortic stenosis is a CHD with high recurrence-rate despite surgical treatment. This study investigated the outcome of operated patients and possible predictors for recurrence.

Retrospective review of all patients (n = 38) ≤ 18 years of age operated for membranous subaortic stenosis between 1994–2019 at Sahlgrenska University Hospital. The primary outcomes were recurrence, reintervention, and mortality. Predictors of recurrence and reintervention were secondary outcomes.

Median age (range) at diagnosis, initial intervention, and last follow-up were 2.3 (0.003–17.2), 5.3 (0.03–17.5) and 17.5 (3.6–20.4) years, respectively. Median follow-up time was 9.9 (0.01–19.5) years. 61% were males, and 53% had other associated CHD. 19 patients (56%) developed recurrence and 7 (21%) underwent reintervention. One patient died peri-operatively. Age <5 years at first intervention increased the likelihood of reintervention. Postoperative peak/mean gradients were higher in patients with disease recurrence.

The median echocardiographic peak-/mean gradients at initial diagnosis, pre-, postoperative, and at last follow-up were 61/36, 83/50, 16/8, and 19/17 mmHg respectively (p < 0.0001 pre/post). Pre-/postoperative peak gradients were linearly correlated, decreasing by 80% pre-/postoperatively (p < 0.01). Presence of symptoms and the preoperative peak gradient were positively associated (p < 0.001) with a peak gradient threshold value of > 90 mmHg. The distance between the subaortic stenosis membrane and the aortic valve was inversely correlated to the preoperative peak-gradient (p < 0.01).

Reintervention following surgical intervention of membranous subaortic stenosis is common. A positive correlation exists between high pre- and postoperative peak-gradient. A low postoperative peak gradient may be important in avoiding recurrence.