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Pediatric Subvalvar Aortic Stenosis Workup

  • Author: Douglas J Schneider, MD; Chief Editor: Howard S Weber, MD, FSCAI  more...
Updated: Sep 19, 2015

Approach Considerations

No specific laboratory blood tests are required in the workup of SAS. Echocardiography is the principal diagnostic study.

Go to Imaging in Aortic Stenosis for more complete information on this topic.



In subvalvar aortic stenosis (SAS), echocardiography enables evaluation of the following:

  • Definition and location of the stenosis
  • Extent of involvement of the left ventricular outflow tract (LVOT)
  • Early aortic valve closure from its involvement and its associated lesion
  • Aortic regurgitation
  • Mitral regurgitation
  • LV hypertrophy
  • Poststenotic aortic dilatation
  • Diagnostic features of associated congenital heart defects
  • LV systolic performance
  • Filling characteristics

Echocardiography helps in defining and localizing SAS (see the image below). It reveals the extent of LVOT involvement, the degree of LV hypertrophy, the indices of LV performance, and the parameters of diastolic function of the LV. Secondary effects, such as the degree of aortic valve insufficiency, mitral valve regurgitation, or poststenotic dilatation of the aorta, may be assessed. Finally, associated congenital heart defects and their influence on the hemodynamic effects of SAS may be evaluated.

Echocardiogram of membranous subaortic stenosis. A Echocardiogram of membranous subaortic stenosis. AO = aortic; LA = left atrium; LVOT = left ventricular outflow tract.

Two-dimensional echocardiography with color Doppler imaging is the current modality of choice to establish the diagnosis of SAS. This noninvasive method allows for serial evaluation of the progression of the obstruction, the development of aortic valve insufficiency, and the results of surgical intervention.

M-mode echocardiography provides indirect evidence of SAS by revealing early closure (from the Venturi effect of the jet formed by the SAS) and the coarse flutter of the aortic valve leaflets.

Two-dimensional echocardiography, and now 3-dimensional (3D) echocardiography, reveals and defines the position of lesions, the extent of involvement of the LVOT (in tunnellike SAS), and the associated defects.[18] Apical views reveal the relationship of the SAS to surrounding structures (eg, mitral valve), and parasternal and subcostal long-axis views reveal the proximity of SAS to the aortic valve (see the image below).

Three-dimensional echocardiography can produce images of SAS with depictions of the morphology and extent remarkably similar to those observed during surgical visualization.

Multiplanar transesophageal echocardiography (TEE) provides superior definitions of the lesion, making it an ideal tool for intraoperative evaluation of the lesion to guide surgical resection and to evaluate the immediate results at the time of surgery.[19] TEE is also useful for diagnostic purposes in patients with a poor acoustic window in whom transthoracic imaging results are not definitive.

A peak instantaneous and a mean pressure gradient across the LVOT estimated during continuous wave Doppler interrogation provide measures of the severity of LVOT obstruction.

When used as a guide to cardiac intervention, Doppler interrogation does not permit the clinician to accurately estimate the pressure gradient in the presence of multiple obstructive LVOT lesions in series, a large ventricular septal defect (VSD), or a tunnel-like obstruction.

Color Doppler evaluation reveals the presence and severity of aortic and mitral regurgitation.


Cardiac Catheterization

Cardiac catheterization is not routinely indicated in isolated subvalvar aortic stenosis (SAS) but can be utilized for preoperative hemodynamic evaluation when associated with other congenital heart defects.

If multiple levels of left ventricular outflow tract obstruction are present, careful pullback pressure measurements performed with an end-hole or high-fidelity manometer-tipped catheter from the left ventricle to the aorta may allow delineation of the pressure gradient and the exact site of obstruction.



In subvalvar aortic stenosis (SAS), even if it is mild, electrocardiography (ECG) reveals a variable degree of left ventricular hypertrophy in 50-80% of patients. ECG findings are occasionally normal in patients with severe SAS. A prominent Q wave in the left precordial leads may be present from septal hypertrophy. Strain pattern is visible on the ECG in approximately 25% of patients and indicates severe obstruction.



Cineangiography is usually not necessary to define the anatomy of subvalvar aortic stenosis (SAS), but it may be helpful if catheterization is being performed to evaluate other associated cardiac defects. A left ventriculogram obtained in a angulated orientation (70º left anterior oblique/20º cranial angulation) delineates the  left ventricular outflow tract (LVOT) and the anatomy of the SAS. The degree of mitral valve regurgitation and anatomy of any ventricular septal defects, if present, are also well demonstrated.


Histologic Findings

Histologic findings in subvalvar aortic stenosis (SAS) are the same in lesions of the fibromuscular ridge or collar and in tunnellike lesions. A composite of different tissue cells, which varies from patient to patient, is present.

Abundant amounts of irregularly oriented and dense collagen fibers and thin, short elastic fibers are visible. Also visible are sparsely scattered fibroblasts with elongated nuclei and smooth muscle cells. Vascularity is generally absent.

Contributor Information and Disclosures

Douglas J Schneider, MD Associate Professor of Pediatrics, Clinical Tract, Division of Pediatric Cardiology, Department of Pediatrics, University of Kentucky College of Medicine; Director, Pediatric Cardiac Catheterization Laboratory, Kentucky Children’s Hospital

Disclosure: Nothing to disclose.


Gautam K Singh, MD, , MRCP Professor of Pediatrics, Division of Cardiology, Director of Noninvasive Imaging Research, Co-Director of Echocardiography Laboratory, Washington University in St Louis School of Medicine; Attending Faculty, Department of Pediatrics, Division of Cardiology, St Louis Children's Hospital

Gautam K Singh, MD, , MRCP is a member of the following medical societies: American College of Cardiology, American Heart Association, American Society of Echocardiography, Royal College of Physicians

Disclosure: Nothing to disclose.

Specialty Editor Board

Mary L Windle, PharmD Adjunct Associate Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Nothing to disclose.

John W Moore, MD, MPH Professor of Clinical Pediatrics, Section of Pediatic Cardiology, Department of Pediatrics, University of California San Diego School of Medicine; Director of Cardiology, Rady Children's Hospital

John W Moore, MD, MPH is a member of the following medical societies: American Academy of Pediatrics, American College of Cardiology, Society for Cardiovascular Angiography and Interventions

Disclosure: Nothing to disclose.

Chief Editor

Howard S Weber, MD, FSCAI Professor of Pediatrics, Section of Pediatric Cardiology, Pennsylvania State University College of Medicine; Director of Interventional Pediatric Cardiology, Penn State Hershey Children's Hospital

Howard S Weber, MD, FSCAI is a member of the following medical societies: American Academy of Pediatrics, American College of Cardiology, Society for Cardiovascular Angiography and Interventions

Disclosure: Received income in an amount equal to or greater than $250 from: St. Jude Medical.

Additional Contributors

Paul M Seib, MD Associate Professor of Pediatrics, University of Arkansas for Medical Sciences; Medical Director, Cardiac Catheterization Laboratory, Co-Medical Director, Cardiovascular Intensive Care Unit, Arkansas Children's Hospital

Paul M Seib, MD is a member of the following medical societies: American Academy of Pediatrics, American College of Cardiology, American Heart Association, Arkansas Medical Society, International Society for Heart and Lung Transplantation, Society for Cardiovascular Angiography and Interventions

Disclosure: Nothing to disclose.

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Echocardiogram of membranous subaortic stenosis. AO = aortic; LA = left atrium; LVOT = left ventricular outflow tract.
Tunnel-type of subaortic stenosis (subvalvular aortic stenosis [SAS]). MV = mitral valve.
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