Subvalvar aortic stenosis

Obstruction of the left ventricular outflow is most often caused by the presence of a fibromuscular shelf, fibrous membrane, posterior deviation of the infundibular septum, or in patients with hypertrophic cardiomyopathy, by the systolic anterior motion of the anterior mitral valve leaflet. Less frequent causes include cardiac tumors or abnormal accessory attachment of the mitral valve to the outlet septum.

The subvalvar area is best visualized from the parasternal long-axis view, from where the etiology of the obstruction can be determined. Surgical or interventional treatment is often very demanding, and in some cases, especially in the subaortic membrane, the lesions tend to recur despite successful initial therapy .

(A) Parasternal long-axis view showing a discrete circular subaortic membrane ( arrows ) and its close relationship to the anterior mitral valve leaflet and the outlet septum. (B) Color flow mapping demonstrating turbulent flow across the left ventricular outflow tract, starting at the level of the membrane. The flow turbulence is likely to cause long-term aortic valve damage, resulting in aortic regurgitation. AoV , aortic valve; LA , left atrium; LV , left ventricle.

(A) Apical five-chamber view in a child with subvalvar aortic stenosis. There is a fibromuscular ridge ( arrow ) arising from the outlet septum, protruding into the left ventricular outflow tract (LVOT). (B) Color flow mapping showing turbulent flow in the LVOT caused by the presence of the ridge. AoV , aortic valve; LA , left atrium; LV , left ventricle; RV , right ventricle.

Parasternal long-axis view in a patient with hypertrophic cardiomyopathy and subvalvar aortic stenosis due to systolic anterior motion of the anterior mitral valve leaflet. The distal portion of the anterior mitral valve leaflet is displaced against the hypertrophied interventricular septum due to the Venturi effect. This results in significant left ventricular outflow tract obstruction as demonstrated on color flow mapping. Ao , aorta; aMV , anterior mitral valve leaflet; LA , left atrium; LV , left ventricle; RV , right ventricle.

Parasternal long-axis view in an infant with interrupted aortic arch and malalignment ventricular septal defect. There is a posterior deviation of the infundibular septum ( arrow ) resulting in subvalvar aortic stenosis and reduced aortic flow. Ao , aorta; LA , left atrium; LV , left ventricle; RV , right ventricle.

Parasternal long-axis view demonstrating a giant rhabdomyoma arising from the interventricular septum. The lesion is partially protruding into the left ventricular outflow tract, causing its severe obstruction. In this case, there was minimal antegrade flow across the aortic valve, resulting in the aortic arch being filled retrogradely from the duct. Ao , aorta; CS , coronary sinus; LA , left atrium; LV , left ventricle.

Aortic valve disease

Aortic valve disease causes either regurgitation or stenosis, and in some cases both. In children, aortic stenosis leads to a wide range of manifestations. At the extreme end of the spectrum, it is associated with major underdevelopment of the left-sided cardiac structures as seen, for example, in hypoplastic left heart syndrome. In these patients, reduced antegrade flow across the aortic valve will result in the retrograde filling of the ascending aorta and the aortic arch from the duct and dependence of the circulation on ductal flow. Associated cardiac dysfunction is almost invariably present.

Characteristic echocardiographic features of valvar aortic stenosis include thickening of the cusps, restricted cusp motion, and commissural fusion, creating a “doming” appearance of the valve in systole. The number of cusps may be variable, ranging from unicommissural to quadricomissural valves. In older children, valvar aortic stenosis is most commonly observed in association with bicommissural (bicuspid) aortic valves. Severe aortic stenosis is defined by a mean transvalvar gradient >40 mmHg. However, the gradient is irrelevant in patients with duct dependent circulation, left ventricular dysfunction, or associated lesions such as coarctation of the aorta or ventricular septal defect with a left-to-right shunt.

Aortic regurgitation is usually acquired, in particular due to previous cardiac procedures, less often congenital. Therapy for aortic valve disease includes surgical or transcatheter treatment .

Examples of common morphological types of the aortic valve and the nomenclature. The term “commissure” refers to the point of contact between two adjacent valvar leaflets as they insert into the annulus. Uni-, bi-, and tricommissural valves are the most common. “ Raphe” is a remnant of a commissure between two underdeveloped adjacent leaflets. In contrast, the term “ fused commissure ” is used when fusion between two initially well-developed leaflets occurs. The fusion can be either complete or incomplete. LCC , left coronary cusp; NCC , noncoronary cusp; RCC , right coronary cusp.

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