*5.1.1 Types of AS*

Obstruction of the left ventricular outflow tract may be seen at valvar (**Figure 1**), sub-valvar (subaortic membranous stenosis [**Figure 2**] and hypertrophic cardiomyopathy [**Figure 3**]), and supra-valvar (**Figure 4**) locations [15–17]. Examples are shown in **Figures 1**–**4**.

#### *5.1.2 Characterization of aortic valve morphology*

The normal aortic valve is tricuspid as shown in **Figure 5**. In congenital AS, most commonly, the aortic valve is bicuspid (**Figures 6** and **7**),

The aortic valve leaflets are thickened (**Figures 1A**, **B** and **7A, B**) and dome during systole (**Figures 1B** and **7C**) in most patients.

*Introductory Chapter: Aortic Valve Disease – Recent Advances DOI: http://dx.doi.org/10.5772/intechopen.112887*

#### **Figure 1.**

*Echocardiographic frames from precordial long axis view of the left ventricle (LV) demonstrating valvar AS. Note the thickened and domed aortic valve (AV). Ao, aorta; LA, left atrium; LV, left ventricle. Reproduced from reference [17].*

#### **Figure 2.**

*Echocardiogram in parasternal long axis (A) and apical five-chamber (B) projections demonstrating the subaortic membrane (SAM). The position of the aortic valve (AV) is shown. Continuous wave and color Doppler studies demonstrated elevated Doppler flow velocity across SAM but are not shown in these echo frames. LA, left atrium; LV, left ventricle. Reproduced from reference [18].*

#### *5.1.3 Quantification of the degree of obstruction*

The flow velocity magnitude across the aortic valve, measured by Doppler, is increased (**Figures 7E** and **8C**) which is used to calculate the systolic pressure gradient across the aortic valve by a modified Bernoulli equation:

$$\text{Peak instantaneous gradient} = 4\,\text{V}^2\tag{1}$$

Where V is the peak Doppler velocity across the aortic valve in meters/sec.

The Doppler velocity measurements are made in parasternal, suprasternal notch, and apical views. Most important, however, is to achieve a close alignment of the Doppler signal to the aortic flow. It should be understood that the Doppler peak

#### **Figure 3.**

*Echocardiograms in parasternal long (A) and short (B) axis projections illustrating severe thickening of the inter-ventricular septum (arrows), suggestive of hypertrophic cardiomyopathy. Continuous wave and color Doppler studies demonstrated elevated Doppler flow velocity across the left ventricular outflow tract at the level of thickened inter-ventricular septum. Ao, aorta; LA, left atrium; LV, left ventricle. Modified from reference [17].*

#### **Figure 4.**

*Echo-Doppler studies in parasternal long axis (A and B) and subcostal (C and D) projections illustrating supra-valvar AS. Note that the stenosis is above the aortic valve as shown with arrows. Color flow imaging shows turbulence in Doppler flow signal as pointed out with arrows (B and D). An increased Doppler flow velocity was recorded superior to the aortic valve but is not illustrated in the above echo frames. LA, left atrium; LV, left ventricle. Reproduced from reference [18].*

instantaneous gradient does not accurately reflect the true peak-to-peak systolic pressure gradient obtained in the cardiac catheterization laboratory because of the pressure recovery phenomenon [19]. Consequently, applicable corrections to account for pressure recovery should be made during the calculations of the pressure gradient. Turbulent flow is also demonstrated by color flow Doppler (**Figures 7D** and **8B**).

*Introductory Chapter: Aortic Valve Disease – Recent Advances DOI: http://dx.doi.org/10.5772/intechopen.112887*

#### **Figure 5.**

*Selected echo images in parasternal short axis view demonstrating normal tricuspid aortic valve in closed (A) and open (B) positions. LA, left atrium; RA, right atrium; RV, right ventricle.*

#### **Figure 6.**

*Selected echo images in parasternal short axis view demonstrating normal tricuspid aortic valve (A), bicuspid aortic valve with vertical (B) and horizontal (C) commissures. The arrows point to the respective aortic valve leaflets.*

The echo-Doppler studies in pediatric patients are sufficiently accurate such that there is generally no need for other imaging studies such as magnetic resonance imaging (MRI) and computed tomography (CT).

#### *5.1.4 Other echocardiographic features*

Annular hypoplasia and dysplasia of aortic valve leaflets have also been seen, mostly in neonates and young babies.

Left ventricular internal dimension (LVID) in diastole is usually normal for age. However, LVID may be increased in patients with long-standing and severe AS. Such left ventricular enlargements are more common in neonates with critical AS. Hypertrophy of the left ventricular musculature in a concentric manner is seen which is mostly proportionate to the severity of obstruction. The left ventricular shortening fraction may be increased, usually proportional to the degree of narrowing. However, in neonates with critical AS and patients with heart failure, it may be decreased. Poststenotic dilatation of the aorta (Ao) is observed in most patients; the degree of such dilatation is not related to the degree of aortic valve obstruction [16–18].

#### **Figure 7.**

*Echo images illustrating a thick (A) and bicuspid (B) aortic valve (BAV) with doming of the aortic valve (AV) (C) pointed out by arrows. Color flow Doppler demonstrates turbulent flow (TF) at the aortic valve (arrow) (D). The Doppler velocity across the AV is low (<2 m/s) (E), suggesting trivial AS with a bicuspid aortic valve. LA, left atrium; LV, left ventricle. Reproduced from reference [18].*

#### **Figure 8.**

*Echo-Doppler studies of a patient with severe AS illustrating an aortic valve (AV) which is thick and domed (A). Color flow imaging demonstrates turbulent flow with a narrow jet (NJ) at the AV (arrow) (B). The Doppler velocity via the AV is high (>6 m/s) (C), suggesting very severe AS; the calculated peak instantaneous gradient is 148 mmHg with a mean of 75 mmHg. The patient has a bicuspid AV which is not demonstrated in these echo frames. Ao, ascending aorta; LA, left atrium; LV, left ventricle. Reproduced from reference [18].*
