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Bicuspid Aortic Valve

Contributors: Wanda C. Miller-Hance, MD and Pablo Motta, MD; Texas Children’s Hospital and Baylor College of Medicine, Houston, TX Overview

The bicuspid aortic valve (BAV) is the most common congenital cardiac malformation with a prevalence between 1 to 2% of the general population. A known male predominance is recognized as well as a familial occurrence. This is the most common lesion that affects the aortic valve (AV). The anomaly can present as an incidental finding on echocardiography, in fact, many children with BAV disease are completely asymptomatic. Potential problems, affecting nearly a third of patients, include aortic valve stenosis, aortic regurgitation, infective endocarditis, and aortic root dilation/aneurysm formation/aortic dissection/rupture. A BAV can develop progressive sclerosis and calcification resulting in stenosis later in life. Aortic dilation can also develop over time, even in the absence of valvar stenosis. This has led to consideration of BAV disease as a genetic vasculopathy.

Several distinct anatomic types of BAV are identified; the most common form is characterized by fusion of the valvar leaflets along a commissure or underdevelopment in one of the commissures (raphe) resulting in a ‘functionally’ bileaflet valvar structure (bicommisural aortic valve) with unequal-sized leaflets. Less frequently in this lesion, only two well-developed, equal-sized leaflets are present (‘true’ bileaflet or bicuspic valve).

A BAV can be found in isolation, however, it is frequently seen within the context of other congenital cardiovascular malformations (i.e., ventricular septal defect, aortic coarctation, interrupted aortic arch, Shone’s complex or related variants).

Transesophageal Echocardiography (TEE)

The AV anatomy is best displayed by TEE at the level of the mid-esophagus in the following views:

Additional TEE views required for the quantitative evaluation of aortic stenosis and to facilitate the examination of aortic regurgitation include:

These two views are helpful in assessing the severity of aortic stenosis as they allow for alignment of the interrogating Doppler beam with the aortic outflow tract. Spectral Doppler (pulsed and continuous wave) can then be readily applied assisted by color flow. Using the modified Bernoulli Equation the peak systolic gradient across the AV can be calculated as follows (Figure 1):

AV Peak Gradient = 4 x (Peak Velocity across AV)2

The mean gradient is obtained by tracing the area in the spectral Doppler display corresponding to aortic flow over time (Figure 2). This provides a better correlation with cardiac catheterization-derived aortic gradients than estimated Doppler peak gradients. The TG LAX and DTG LAX views are also helpful in the evaluation of aortic valve regurgitation allowing the extent of the jet to be examined as it courses into the ventricle during diastole (Video 5).