Subvalvular Aortic Stenosis: Current Insights into an Often Overlooked Cause of Left Ventricular Outflow Tract (LVOT) Obstruction

Figures

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  Figure 1. Anatomical spectrum of subvalvular aortic stenosis (SAS). (A) Schematic anatomical overview of the left ventricular outflow tract (LVOT) demonstrating the typical location of subvalvular obstruction immediately beneath the aortic valve. The illustration highlights the anatomical relationship between the subaortic lesion, aortic valve, interventricular septum, LVOT, and left ventricle. (B) Representative morphological variants of SAS. From left to right: discrete subaortic membrane, fibromuscular ridge, tunnel-type subaortic stenosis, and circumferential/complex subvalvular obstruction. These anatomical patterns differ in lesion extent, degree of LVOT narrowing, and surgical complexity. (C) Typical echocardiographic appearance of SAS on transthoracic echocardiography, demonstrating the visualization of the subaortic membrane and associated turbulent systolic flow across the LVOT. (D) Examples of multimodality imaging used for anatomical characterization and preoperative assessment, including transesophageal echocardiography, cardiac magnetic resonance imaging, and three-dimensional computed tomography, illustrating the complementary role of advanced imaging techniques in defining…

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  Figure 2. Flow diagram of the literature identification and selection process.

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  Figure 3. Proposed mechanisms underlying the development and progression of subvalvular aortic stenosis. Schematic overview illustrating the interplay between anatomical predisposition, abnormal left ventricular outflow tract flow dynamics, endothelial injury, progressive fibromuscular remodeling, and increasing left ventricular outflow tract obstruction. The figure also summarizes the major factors influencing disease progression, the natural history of subvalvular aortic stenosis, and its principal hemodynamic and clinical consequences, including left ventricular hypertrophy, aortic regurgitation, and the risk of postoperative recurrence.

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  Figure 4. Multimodality imaging in subvalvular aortic stenosis. Representative examples of transthoracic echocardiography, transesophageal echocardiography, cardiac magnetic resonance imaging, and computed tomography illustrating their complementary roles in the diagnosis and anatomical characterization of subvalvular aortic stenosis. While echocardiography remains the first-line imaging modality for assessing lesion morphology and hemodynamic severity, cardiac magnetic resonance imaging and computed tomography provide additional anatomical detail and facilitate preoperative planning, particularly in complex cases.

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  Figure 5. Management strategy for subvalvular aortic stenosis. Proposed clinical pathway for the evaluation and management of patients with subvalvular aortic stenosis, including diagnosis, risk stratification, indications for surgical intervention, operative treatment, and long-term postoperative surveillance. Regular follow-up is essential because of the progressive nature of the disease and the potential for residual or recurrent left ventricular outflow tract obstruction.