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KEY FEATURES

ESSENTIALS OF DIAGNOSIS

  • With no other congenital heart abnormalities, it is usually asymptomatic

  • Low-pitched systolic ejection murmur is heard at the left sternal border radiating to the neck

  • Two-dimensional echocardiography defines the anatomy of the obstruction

  • Doppler echocardiography estimates the pressure gradient

GENERAL CONSIDERATIONS

  • Subvalvular aortic stenosis accounts for 10–20% of fixed left ventricular outflow lesions in children

  • Is more common in males

  • Associated congenital heart lesions are common, such as:

    • – Ventricular septal defect

    • – Patent ductus arteriosus

    • – Other components of Shone’s syndrome: coarctation of the aorta, bicuspid aortic valve, supramitral valve ring, cor triatriatum, parachute mitral valve, hypoplastic aortic arch, and hypoplastic left ventricle

  • Subvalvular stenosis is progressive even after surgical correction

  • The pathology ranges from a thin discrete membrane, to a fibromuscular ring, to a tunnel-like narrowing of the left ventricular outflow tract

  • Most stenoses are membranes or ridges 5–15 mm below the aortic valve

  • The membrane can attach to the anterior leaflet of the mitral valve and cause mitral regurgitation

  • Aortic valve thickening and associated aortic regurgitation are common and may persist after membrane removal

CLINICAL PRESENTATION

SYMPTOMS AND SIGNS

  • Most patients are asymptomatic or have symptoms related to associated congenital heart disease

  • When present, symptoms are similar to those of valvular aortic stenosis:

    • – Dyspnea

    • – Chest pain

    • – Syncope

    • – Palpitation

PHYSICAL EXAM FINDINGS

  • A left ventricular lift and precordial thrill may be present

  • Auscultation:

    • – A fourth heart sound may be present

    • – There is a low-pitched systolic ejection murmur best heard in the left third or fourth parasternal space

    • – An early diastolic high-pitched murmur of aortic regurgitation is common

  • A holosystolic murmur at the apex of mitral regurgitation may be present

DIFFERENTIAL DIAGNOSIS

  • Valvular aortic stenosis

  • Supravalvular aortic stenosis

  • Hypertrophic cardiomyopathy

DIAGNOSTIC EVALUATION

ELECTROCARDIOGRAPHY

  • Left ventricular hypertrophy is common

IMAGING STUDIES

  • M-mode echocardiography shows coarse fluttering of the aortic valve and early systolic closure

  • Two-dimensional echo defines the anatomy of the subvalvular obstruction

  • If surgery is contemplated, transesophageal echo better defines the lesion for planning surgery

  • Doppler echocardiography is used:

    • – To estimate the pressure gradient across the lesion

    • – If there is a ventricular septal defect or more than 1 obstructive lesion (eg, aortic valve stenosis or a tunnel-like left ventricle outflow tract), the estimated pressure gradient may not be reliable

    • – For assessing other lesions

DIAGNOSTIC PROCEDURES

  • Cardiac catheterization is best for distinguishing the hemodynamic contributions of multiple lesions

  • Cardiac MRI may be useful to determine the extent of abnormalities, especially of the proximal aorta

TREATMENT

CARDIOLOGY REFERRAL
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