Clinical introduction A 56-year-old lady with a background of hypertension was admitted to our institution with acute pulmonary oedema. She reported gradual and increasingly severe dyspnoea on exertion over the preceding 12 months and, prior to presentation, her exercise tolerance was restricted to one flight of stairs. On transthoracic echocardiography during the index admission, left ventricular size and systolic function were normal, and peak and mean transaortic gradients were 67 mm Hg and 33 mm Hg, respectively, with a peak velocity of 3.9 m/s. No aortic incompetence or other significant valvular abnormality was noted. A transoesophageal echocardiogram was performed. Figure 1 depicts the mid-oesophageal parasternal long-axis view. What is the explanation behind the significant transaortic gradient?
Question What is the explanation behind the significant transaortic gradient?
Ventricular septal defect
Supravalvular aortic stenosis
Aortic valvular stenosis
Hypertrophic obstructive cardiomyopathy
- aortic stenosis
- hypertrophic cardiomyopathy
- valvular heart disease
- valve disease surgery
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Transoesophageal echocardiogram demonstrated normal left ventricular size and systolic function (figure 2, online supplementary video 1). Close inspection of the aortic valve apparatus revealed a subaortic membrane causing significant restriction to blood flow across it (mean transmembrane gradient: 35 mm Hg). The aortic valve leaflets were mobile and did not display significant calcification, making the diagnosis of valvular stenosis unlikely. The absence of systolic anterior motion of the mitral valve apparatus and interventricular septum thickening ruled out hypertrophic cardiomyopathy. No supravalvular structure could appreciated, and the interventricular septum appeared intact. At surgery, the subaortic membrane was visualised as a membranous structure about 10 mm ventricular to the aortic valve and resected (online supplementary figure 1, online supplementary video 2). Histopathologically, thickened endocardium with expansion due to myxoid stromal material was seen (online supplementary figure 2). She made an uneventful recovery.
Congenital aortic stenosis (AS) is a rare condition, with an incidence of around 6 in 10 000 live births.1Among children with congenital AS, subvalvular AS accounts for 10% to 14% of cases.1-2 Subvalvular AS is associated with aortic regurgitation in greater than 50% of cases.1-5 Concomitant cardiac malformations occur in 50% to 65% of patients.1-5 Although patients with subvalvular aortic stenosis often have rapidly progressive obstruction in infancy and early childhood, the condition may occasionally remain stable for years and present in adulthood only.4-5 Presenting symptoms include dyspnoea, chest discomfort, syncope, acute decompensated heart failure and infective endocarditis.1-5 Treatment is surgical. Since subaortic membrane is an uncommon diagnosis in the adult, it is frequently mistaken for valvular stenosis. Our case highlights the importance of considering rarer mimicking diagnoses when assessing common conditions.
Contributors RS: provided direct care of the patient, established the diagnosis of subaortic membrane and referred the patient for surgical intervention. Prepared the manuscript and the imaging. AI: assisted with the collection of the surgical and histopathological images. PJ: provided overall guidance to the project. Performed the open heart procedure on the patient.
Funding This research received no specific grant from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests None declared.
Patient consent Obtained.
Provenance and peer review Not commissioned; externally peer reviewed.