Supravalvular aortic stenosis mimicking hypertrophic obstructive cardiomyopathy: a case report

Hypertrophic cardiomyopathy (HCM) is a relatively common genetic disorder often associated with left ventricular outflow tract (LVOT) obstruction. However, the presence of certain structural abnormalities such as supravalvular aortic stenosis (SVAS) can contribute to elevated LVOT gradients and thereby mimic obstructive HCM. This case highlights the importance of multimodality imaging in accurately determining the aetiology of LVOT obstruction, which is critical to guiding appropriate management.

A 27-year-old male with progressive dyspnoea, fatigue, and recent syncope was initially diagnosed with obstructive HCM based on transthoracic echocardiography (TTE) findings of severe left ventricular hypertrophy and a mid-cavitary gradient exceeding 100 mmHg with Valsalva. Genetic testing for HCM was negative. Cardiac magnetic resonance (CMR) imaging confirmed concentric hypertrophy with asymmetric septal involvement and also suggested atypical flow acceleration. Prior to planned septal myectomy, transoesophageal echocardiography (TEE) revealed a supravalvular aortic membrane with a resting gradient of 55 mmHg. Given this finding, the surgical plan was modified, and the patient underwent excision of the fibrotic ring and aortic reconstruction. Postoperatively, the supravalvular gradient resolved and the patient reported symptomatic relief.

When evaluating LVOT obstruction, the limitations of TTE in assessing supravalvular structures can lead to diagnostic error. Patients with suspected HCM who are being evaluated for surgical management should also undergo TEE and CMR to assess the supravalvular aorta for potential SVAS contributing to an elevated LVOT gradient. Incorporating multimodality imaging in these patients enhances diagnostic accuracy, accurately directs surgical planning, and reduces the risk of proceeding with unnecessary intervention.