Aortic Stenosis in Children
Aortic stenosis in adults is quite different than the type aortic stenosis found in neonates. Aortic stenosis in adults begins as an inflammatory process that occurs in the endothelial tissue of the valve that attracts fatty deposits to be laid down upon the valve and is encapsulated by cholesterol deposits, a process that takes years or decades to develop. The reason for this original inflammation is not well known, but is often related to rheumatic or scarlet fever and other factors such as diet and high blood pressure.
A normal aortic valve is trifoliate (tricuspid or trileaflet) without any fusion of the leaflets. For the echocardiographer looking down at the aortic valve in the short axis view, the non-coronary cusp will be in the 7 o’clock position, the right coronary artery will be in the 11 o’clock position and the left coronary artery will be in the 3 o’clock position. Regardless of valve morphology, there will almost always be three coronary sinuses and, with the exception of anomalous coronary arteries, the right coronary artery will emerge from the right coronary sinus and the left coronary artery will emerge from the left coronary sinus.
A raphe is the fusion of two leaflets resulting in an observable “slit” like appearance at the point of apposition. A bicuspid aortic valve is congenital and presents with fusion of or a raphe of the right and left coronary leaflets (80% of cases) or a fusion or raphe of the right and non-coronary leaflets (20% of cases). A true bicuspid aortic valve, or an aortic valve with only two leaflets is very rare, but it can happen. Further calcification of a bicuspid valve typically begins in the late twenties or early thirties and can progress to severe aortic stenosis. Echocardiograms every year or two for these patients is advised.
A unifoliate or unicommissural (one leaflet that partially opens) is usually associated with critical aortic stenosis in neonates. In these cases, there are two raphes; the right coronary cusp and the left coronary cusps are fused, as well as the fusion of the right coronary cusp and the non-coronary cusps. This leaves space between the left coronary cusp and the non-coronary cusp as the only outlet for blood flow. Furthermore, the cusps are abnormally attached to the aortic annulus, which causes varying degrees of aortic regurgitation.
It is not necessary to measure the aortic valve area in children, but it is important to document the peak and mean pressure gradient across the aortic valve.
16-30 mm/hg is considered mild
30-50 mm/hg is moderate
>50 mm/hg is considered severe
When using the continuity equation to measure aortic valve area in adults, the critical variable is the proper measurement of the left ventricular outflow tract (LVOT) diameter. Measure the diameter just below the aortic valve at the level of the aortic valve annulus in the parasternal long axis view. In addition, measure the maximum and mean velocity of the LVOT flow by placing the sample volume below the aortic valve, just as the LVOT flow begins to increase. Measure the peak and mean gradient across the valve in three different locations. In children, just measure the peak and mean gradient across the valve in one of the apical views, or possibly in the suprasternal view.
Be sure to differentiate between valvular stenosis and sub-valvular stenosis or supra-valvular stenosis. Sub-valvular stenosis is the occurrence of an obstructive, fibrous ridge of tissue that encircles the LVOT just below the aortic valve, and may co-exist with a ventricular septal defect. Further differentiate this type of lesion with asymmetric septal hypertrophy (ASH), which may also cause obstruction of the LVOT, particularly in hypertrophic cardiomyopathy. These lesions can be surgically excised.
Supra-valvular stenosis is a grossly abnormal and thickened aortic root with scarring, just superior to the aortic valve and may or may not involve inflammation of the coronary sinuses and the coronary artery orifices. When the coronary arteries are involved, this can lead to ischemia. This defect is related to Williams’s syndrome and is part of a systemic syndrome, which frequently involves inflammation the origin of the carotid, renal and iliac arteries.
Critical aortic stenosis is typically treated with balloon dilatation of the LVOT or the aortic valve and outcomes are variable. Serial echocardiograms every three months are advised.
Ken Heiden