Sub-Aortic Membrane: What Is Beyond Simple Membrane Resection Early and Mid-Term Results

Abstract

Background: Sub-aortic membrane (SAM) is a shelf-like fibrous structure beneath the aortic valve that is a common cause of left ventricular outflow tract obstruction (LVOTO). If untreated, it can lead to progressive aortic regurgitation (AR) and hemodynamic compromise. When indicated, surgical resection is the standard treatment, but recurrence rates and postoperative outcomes vary depending on surgical technique and patient characteristics.
Objective: To evaluate the early and mid-term outcomes of surgical resection for SAM, focusing on its impact on left ventricular outflow tract (LVOT) gradients, AR severity, and functional status.
Methods: This retrospective study included 16 patients with isolated SAM or SAM associated with mild to moderate AR, operated on at Beni Suef University Hospital between 2015 and 2021. Indications for surgery were a peak LVOT Doppler gradient ≥30 mmHg or more than mild AR. Surgical resection involved complete removal of the membrane, including its fibrous extensions, septal myomectomy with release of both fibrous trigons if needed. Patients were assessed intraoperatively, early postoperatively (within one month), and at mid-term follow-up (6 months to 4 years). Key outcomes included LVOT gradient reduction, AR progression, and functional status using The New York Heart Association (NYHA) classification.
Results: The mean preoperative LVOT gradient was 42.4 ± 9.9 mmHg, significantly reduced to 8.1 ± 4.5 mmHg intraoperatively and stabilized at 10.3 ± 5.2 mmHg at mid-term follow-up (p < 0.001). Moderate AR decreased from 25% preoperatively to 6.2% at mid-term (p < 0.001). NYHA Grade III cases improved from 31.3% preoperatively to 6.2% at mid-term follow-up (p = 0.014). One patient experienced postoperative AR progression due to cusp perforation, and another had persistent moderate AR due to dense fibrous adhesion. No recurrence of SAM was observed during follow-up.
Conclusions: A more extensive surgical approach to SAM resection can lead to prolonged relief of LVOTO, stabilizing or improving AR, and enhancing functional outcomes in early and mid-term follow-ups. These results highlight the importance of extensive and comprehensive surgical approach to reduce rate of recurrence and improve outcome. Long-term studies are needed to confirm the durability of these outcomes.