Subvalvular aortic stenosis

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Aortic Stenosis Microchapters


Patient Information


Historical Perspective




Differentiating Aortic Stenosis from other Diseases

Epidemiology and Demographics

Risk Factors

Natural History, Complications and Prognosis


History and Symptoms

Physical Examination

Cardiac Stress Test


Chest X Ray




Cardiac Catheterization

Aortic Valve Area

Aortic Valve Area Calculation


General Approach

Medical Therapy


Percutaneous Aortic Balloon Valvotomy (PABV) or Aortic Valvuloplasty

Transcatheter Aortic Valve Replacement (TAVR)

Critical Pathway
Patient Selection
Valve Types
TAVR Procedure
Post TAVR management
AHA/ACC Guideline Recommendations

Follow Up


Precautions and Prophylaxis

Cost-Effectiveness of Therapy

Future or Investigational Therapies

Case Studies

Case #1

Subvalvular aortic stenosis On the Web

Most recent articles

Most cited articles

Review articles

CME Programs

Powerpoint slides


American Roentgen Ray Society Images of Subvalvular aortic stenosis

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Echo & Ultrasound
CT Images

Ongoing Trials at Clinical

US National Guidelines Clearinghouse

NICE Guidance

FDA on Subvalvular aortic stenosis

CDC on Subvalvular aortic stenosis

Subvalvular aortic stenosis in the news

Blogs on Subvalvular aortic stenosis

Directions to Hospitals Treating Subvalvular aortic stenosis

Risk calculators and risk factors for Subvalvular aortic stenosis

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Usama Talib, BSc, MD [2]


Aortic insufficiency is more common in this form of aortic stenosis and occurs in 50 to 75% of patients. It can be classified as fixed or dynamic type depending on the dynamics of the obstruction.[1]

Epidemiology and Demographics

Aortic subvalvular stenosis is the second most common form of congenital left ventricular outflow tract obstruction and occurs in 8-30% of all forms of left ventricular outflow tract obstruction. The level of obstruction is located just beneath the aortic valve. HOCM (a.k.a. idiopathic hypertrophic subaortic stenosis or IHSS) is not present at birth and is not considered a congenital lesion.[2]


There are several varieties of congenital aortic subvalvular stenosis (or subaortic stenosis):[1][3]

  1. Membranous: A fixed localized membrane 0.5 to 2 cm below the level of the aortic valve and attached to the septum and the base of the anterior mitral leaflet.
  2. Fibromuscular:
    • More commonly there is a fibromuscular membrane or tunnel with a significant muscular component which can sometimes be hard to distinguish from IHSS. This is a more severe form and is often associated with a small aortic root.
    • Associated aortic insufficiency (AI) is often present due to the high speed jet of blood through the aortic cusps resulting in fibrosis and retraction.
  3. Congenital anomalies of the mitral valve:
    • Attachment to ventricular septum of accessory chordae from anterior mitral leaflet
    • Redundant AV valve tissue causing subaortic obstruction.
  4. Aneurysm of the membranous ventricular septum

Natural History

The symptoms are similar to that of valvular aortic stenosis but begin earlier in infancy or early adulthood.



The symptoms are similar to that of valvular aortic stenosis but begin earlier in infancy or early adulthood.


  • High doppler gradient and normal AV.
  • It may require a repeat TTE or TEE




The membrane can be resected as shown in the videos below:




2008 ACC/AHA Guidelines for the Management of Adults With Congenital Heart Disease (DO NOT EDIT)[4]

Surgical Intervention (DO NOT EDIT)[4]

Class I
"1. Surgical intervention is recommended for patients with SubAS and a peak instantaneous gradient of 50 mm Hg or a mean gradient of 30 mm Hg on echocardiography-Doppler.(Level of Evidence: C) "
"2. Surgical intervention is recommended for SubAS with less than a 50 mm Hg peak or less than a 30 mm Hg mean gradient and progressive AR and an LV dimension at end-systolic diameter of 50 mm or LV ejection fraction less than 55%.(Level of Evidence: C) "
Class III
"1. Surgical intervention is not recommended to prevent AR for patients with SubAS if the patient has trivial LVOT obstruction or trivial to mild AR.(Level of Evidence: C) "
Class IIb
"1. Surgical resection may be considered in patients with a mean gradient of 30 mm Hg, but careful follow-up is required to detect progression of stenosis or AR.(Level of Evidence: C) "
"2. Surgical resection may be considered for patients with less than a 50 mm Hg peak gradient or less than a 30 mm Hg mean gradient in the following situations:"
"a. When LV hypertrophy is present.(Level of Evidence: C) "
"b. When pregnancy is being planned.(Level of Evidence: C) "
"c. When the patient plans to engage in strenuous/competitive sports.(Level of Evidence: C) "

Key Issues to Evaluate and Follow-Up (DO NOT EDIT)[4]

Class I
"1. Lifelong cardiology follow-up, including evaluation by and/or consultation with a cardiologist with expertise in ACHD, is recommended for all patients with SubAS, repaired or not. (Level of Evidence: C)"
"2. The unoperated asymptomatic adult with stable LVOT obstruction due to SubAS and a mean gradient less than 30 mm Hg without LV hypertrophy or significant AR should be monitored at yearly intervals for increasing obstruction, the development or progression of AR, and the evaluation of systolic and diastolic LV function. (Level of Evidence: B)"
Class IIa
"1. Stress testing to determine exercise capability, symptoms, ECG changes or arrhythmias, or increase in LVOT gradient is reasonable in the presence of otherwise equivocal indications for intervention. (Level of Evidence: C)"


  1. 1.0 1.1 Mashari A, Mahmood F (2016). "Fixed versus dynamic left ventricular outflow tract obstruction: Res ipsa loquitur". J Thorac Cardiovasc Surg. 151 (3): 885–6. doi:10.1016/j.jtcvs.2015.11.009. PMID 26682620.
  2. Hyuga S, Okutomi T, Kato R, Hosokawa Y (2016). "Continuous spinal labor analgesia for two deliveries in a parturient with severe subvalvular aortic stenosis". J Anesth. 30 (6): 1067–1070. doi:10.1007/s00540-016-2238-6. PMID 27549335.
  3. Aslam S, Khairy P, Shohoudi A, Mercier LA, Dore A, Marcotte F; et al. (2016). "Shone Complex: An Under-recognized Congenital Heart Disease With Substantial Morbidity in Adulthood". Can J Cardiol. doi:10.1016/j.cjca.2016.09.005. PMID 27956040.
  4. 4.0 4.1 4.2 Warnes CA, Williams RG, Bashore TM, Child JS, Connolly HM, Dearani JA; et al. (2008). "ACC/AHA 2008 guidelines for the management of adults with congenital heart disease: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Writing Committee to Develop Guidelines on the Management of Adults With Congenital Heart Disease). Developed in Collaboration With the American Society of Echocardiography, Heart Rhythm Society, International Society for Adult Congenital Heart Disease, Society for Cardiovascular Angiography and Interventions, and Society of Thoracic Surgeons". J Am Coll Cardiol. 52 (23): e1–121. doi:10.1016/j.jacc.2008.10.001. PMID 19038677.

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