Abstract
Subaortic stenosis (SAS) is a rare entity in adults with unclear etiology and variable presentation. SAS may be presented with symptoms mimicking Hypertrophic Cardiomyopathy (HCM). Often a combination of imaging modalities is needed to distinguish SAS from HCM with obstruction.
A 53 years old man, smoker, was referred to our medical center suffering from shortness of breath on exertion. He first presented at another facility with a 2 month history of shortness of breath and chest discomfort during brisk physical activity and the possible diagnosis of HCM was made. On physical examination, a 3/6 systolic murmur was audible along the left sternal border, that became louder with standing and the Valsalva maneuver. The patient had non distended jugular veins, clear lung fields and no ankle edema. The results of laboratory exams did not reveal any pathological sign.
The transthoracic echocardiogram revealed significant left ventricular hypertrophy (Interventricular septum 21 mm, Posterior wall 16 mm) with normal left ventricular systolic performance (ejection fraction >70%). The aortic valve was tricuspid and calcified whereas mitral valve was morphologically normal, with systolic anterior motion and mild posterolaterally directed regurgitation. Two systolic gradients, one dynamic, late peaking of 85mmHg and another fixed of 70mmHg were detected in left ventricular outflow track (LVOT).
Transesophageal echocardiography was performed for the better evaluation of aortic valve and showed a three level obstruction caused by the systolic motion of the mitral valve towards the hypertrophic septum at LVOT, the presence of a membranous subaortic membrane and the calcified aortic valve respectively. The aortic valve was calcified with a moderate stenosis (0.8cm2 / m2) from 3D planimetry. A Cardiac Magnetic Resonance exam was ordered and confirmed the significance of hypertrophy and the presence of circumferential subaortic membrane. No late enhancement after the administration of Gadolinium was observed. Coronary angiography was performed and demonstrated normal coronary arteries.
We hypothesized that the presence of subaortic membrane led to marked myocardial wall thickness and to the destruction of the aortic valve due to turbulent flow in the LVOT. The patient was referred for surgical management
Extended septal myectomy combined with complete resection of orbital subaortic membrane were performed. he calcified aortic valve was replaced by bioprosthetic valve No 23mm.
The patient tolerated the procedure well with significant symptomatic improvement. TTE performed 1 month postoperatively showed no remarkable LVOT gradient. The results of histopathology and genes investigations are pending.
Subaortic membrane is a rare cause of symptoms that can mimic hypertrophic cardiomyopathy. A combination of imaging modalities is needed to distinguish subaortic stenosis from aortic valve stenosis and hypertrophic obstructive cardiomyopathy.
Abstract P1321 Figure. Three levels obstruction
Discrete subaortic stenosis in adults: increased prevalence and slow rate of progression of the obstruction and aortic regurgitation