Adult Presentation of Subaortic Stenosis with Subaortic Membrane Treated with Surgical Removal

Abstract

Subaortic stenosis (SAS) is a rare heart disease in adults with an unclear etiology and variable clinical presentation. In some cases, SAS appears as hypertrophic cardiomyopathy with obstruction due to the accompanying systolic anterior motion of the mitral valve. A 46-year-old male with dizziness for several months presented in the outpatient department. Two-dimensional transthoracic echocardiography demonstrated a slightly hypertrophic left ventricle with normal systolic function without wall-motion abnormalities. Just below the aortic valve, a linear structure protruding from the septum side and the left-ventricular outflow tract (LVOT) side of the mitral valve was confirmed, which was causing a significant pressure gradient (mean and maximum of 91 mmHg and 138 mmHg, respectively). A diagnosis of SAS with subaortic membrane was made, and surgical myomectomy and subaortic membrane removal surgery were performed. Postoperative transthoracic echocardiography did not show flow acceleration through the LVOT, nor a significant pressure gradient across the aortic valve. This case report highlights the clinical significance of SAS with subaortic membrane, which can be confused with aortic stenosis of other etiology.

Imaging of left ventricular outflow tract obstruction in hypertrophic cardiomyopathy

“…However, HCM is not the only obstructive subvalvular pathology. A subaortic membrane is an often late-diagnosed congenital abnormality, which obstructs flow in the LVOT [26]. The Doppler profile of obstruction from a subaortic membrane will typically be mid-early peaking, differentiating it from the late peaking of HCM; however, HCM is also capable of producing early-peaking obstructive waveforms [27].…”

Subvalvular Aortic Stenosis: Learning From Human and Canine Clinical Research

“…American College of Cardiology/American Heart Association (ACC/AHA) guidelines dictate that surgical intervention is appropriate and indicated for patients with a peak instantaneous echocardiographic gradient greater than 50 mm Hg, a mean gradient greater than 30 mm Hg, or a catheter measurement of the resting peak-to-peak gradient greater than 50 mm Hg [ 3 , 67 ]. Surgery is further indicated for patients with significant obstruction and for those with a lower pressure gradient secondary to left ventricular systolic dysfunction due to myocardial remodeling [ 33 ].…”

“…There is a high recurrence rate after initial surgical relief (estimated to be 6-30% for human patients), despite removal of the anomalous fibrous tissue, suggesting that the underlying pathological process is unaltered [ 33 , 35 ]. The re-operation rate is also high (23.5%, with 14.7% of patients requiring re-operation due to recurrence, 5.9% due to severe AI, and 2.9% due to an iatrogenic ventricular septal defect (VSD) creation) [ 34 , 66 ].…”

“…The re-operation rate is also high (23.5%, with 14.7% of patients requiring re-operation due to recurrence, 5.9% due to severe AI, and 2.9% due to an iatrogenic ventricular septal defect (VSD) creation) [ 34 , 66 ]. Furthermore, the risk of recurrence is greater for human patients who are younger at the time of diagnosis and/or surgical intervention, those who have a smaller aortic annulus, those with an obstruction in close proximity to the aortic valve itself, and those with a higher preoperative peak LVOT pressure gradient [ 33 , 66 ]. Nevertheless, the majority of the time, survival post-surgery is excellent and not significantly different than people with no diagnosis of SAS [ 81 ].…”

Undiagnosed sub-valvular aortic stenosis with an associated Ventricular Septal Defect (VSD) presenting late in a multi-parous woman

“…Sub-valvular aortic stenosis (SAS), otherwise known as subaortic stenosis, is a rare disorder that causes left ventricular outflow tract obstruction [ 1 ]. It is the second most common type of aortic stenosis, after valvular aortic stenosis with a prevalence of 6.5% of all adult congenital heart diseases [ 2 ].…”