Subaortic Membrane With a Patent Ductus Arteriosus in an Adult Patient: A Challenging Diagnostic Dilemma

Subaortic membrane (SAM) is a subtype of left ventricular outflow obstruction, rarely seen in adults. In some cases, SAM may be associated with other congenital defects. The association of patent ductus arteriosus (PDA) and SAM is the rarest, especially in adult patients. The management of these patients is delicate in terms of diagnosis, timing, and the appropriate surgical technique. A 34-year-old patient with a known aortic heart murmur presented with exertional syncope. She was referred to our hospital for aortic valve replacement due to symptomatic aortic stenosis. Transthoracic and transesophageal echocardiography demonstrated a SAM with significant stenosis (mean gradient 48 mmHg) associated with a PDA, mild to moderate aortic regurgitation (AR), and an ascending aortic aneurysm. The heart team decided to proceed with membrane resection, aortic valve replacement, and ascending aortic graft. This case highlights the challenge of managing adult congenital heart disease, particularly regarding diagnosis and optimal timing for surgical intervention. The subaortic membrane is a structural anomaly that can be either congenital or acquired. The primary indication for surgery is the symptomatic form or its association with severe AR. We believe that prophylactic surgery should be considered in isolated cases of mixed anomalies.