Subaortic stenosis (SAS) is a rare entity in adults with an unclear aetiology and variable clinical presentations and outcomes. SAS typically tends to occur in the first decade of life either as an isolated lesion or in association with other congenital heart diseases. The clinical presentation of SAS can closely mimic hypertrophic cardiomyopathy (HCM) with obstructive physiology.

We present two cases of SAS in adults that were initially presumed to be HCM. The patients were in their late forties and were referred to HCM clinic for further evaluation. Careful review of the transthoracic echocardiogram was indicative for the presence of possible subaortic membrane. These patients underwent subsequent imaging studies that completed the diagnosis for SAS and thereafter had successful surgical resection of the subaortic membrane.

Subaortic stenosis remains a rare and clinically challenging diagnosis in the adult population. Often a combination of imaging modalities is needed to distinguish SAS from HCM with obstruction. It is critical to make the appropriate diagnosis as the treatment options are vastly different from the SAS and HCM with obstruction as well as the implications of a diagnosis of HCM with regards to risk of sudden death and family screening.