Abnormalities of the left ventricular outflow tract (LVOT) can occur at the subvalvular, valvular and supravalvular level and are some of the most common defects. They occur in about 5% of all children that have congenital heat defects and are also highly associated with other left sided lesions such as ASD’s, AV Canal (endocardial cushion defect), VSD’s and coarctation of the aorta. It is important also to evaluate the LVOT, aortic valve and aorta in children who have Down Syndrome (Trisomy 21).
The normal aortic valve is tricuspid (trileaflet), has sinus of valsalva apparatus that open the two coronary artery systems (right and left coronary arteries), and one leaflet that does not open to any coronary artery. These leaflets are named the right coronary, left coronary and non coronary leaflets.
An abnormal aortic valve may be unileaflet, bileaflet, or trileaflet with one fused leaflet otherwise known as raphe. It is important for the echocardiographer to evaluate the aortic valve appropriately and allow the reading physician to properly diagnose the particular aortic valve abnormality. This is best done in the parasternal short axis view, which also allows one to properly image the origins of the coronary arteries.
Bicuspid aortic valves may be mildly, moderately or severely stenotic, and may not be noticed until well into adulthood. A truly bicuspid valve is rare, whereas “bicuspid” valves usually demonstrate a trileaflet pattern with one fused leaflet (or raphe). A trileaflet valve with calcification is considered “aortic stenosis”.
For the echocardiographer, first determine whether this is a subvalvular, valvular or supravalvular lesion. If it is valvular, then determine whether it is unileaflet, bileaflet or trileaflet. Visualize the raphe (if present). Evaluate the coronary artery origins and make sure they are not anomalous (see previous post for “anomalous coronary arteries”). Use Doppler to evaluate the gradient across the valve, and use the continuity equation to determine the severity of the stenosis.
Mild: 16 mmHg to 30 mmHg
Moderate: 30 mmHg to 50 mmHg
Severe: >50 mmHg
Do not forget to evaluate other left sided defects; Remember the adage “where there is one left sided defect, look for others”. Look for AV canal, ASD’s, VSD’s, coarctation of the aorta, subvalvular and supravalvular defects and any discordant atrioventrular defects.
Ken Heiden RDCS