Chapter30 Aorta

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Section V: Cardiac Radiology

aneurysm formation are also associated with a bicuspid aortic valve. Due to the increased risk of rupture compared to the general population, guidelines recommend the repair of these aneurysms when they measure between 4.5 and 5 cm diame- ter versus 5.5 cm in the general population. Another common association with a bicuspid aortic valve is aortic coarctation, which is discussed below. Unicuspid aortic valve has a reported incidence of 0.02%. Unicuspid aortic valve is defined by a single opening/commissure (i.e., unicommissural) usually in the left poste- rior position and has similar associations as bicuspid aortic valve (Fig. 30.4). Quadricuspid aortic valve has a clover-leaf morphology, is extremely rare, and more typically associ- ated with early-onset regurgitation as opposed to stenosis (Fig. 30.5). Ascending Aorta The ascending aorta extends from the sinotubular junction to the origin of the right brachiocephalic artery (Fig. 30.1). The normal ascending aorta arises posterior and to the right of the main pulmonary artery (Fig. 30.6). CT or MR evaluation of the aortic root and ascending aorta should use ECG gating to minimize cardiac motion artifact. It is important to reduce cardiac motion for multi- ple reasons including improved visualization of the valve/ root anatomy, accurate measurement of the aorta in assess- ment for aneurysm, and to prevent false-positive diagnosis of aortic dissection. Gating technique (prospective vs. retrospec- tive) will also vary depending on the indication of the study. For instance, evaluation of valvular function or dysfunction requires retrospective gating, while basic anatomic evaluation can be performed with prospective gating.

Left Common Carotid

Left Subclavian

Branchio - cephalic

Ascending Aorta

Sinuses of Valsalva

Aortic Root

Descending Aorta

Figure 30.1.  3D Volume-Rendered Reformat of the Thoracic Aorta. Aortic root extends from the aortic valve annulus ( dashed line ) to the sinotubular junction ( solid line ) to the origin of the brachiocephalic artery. Normal three-vessel branching pattern of the aortic arch.

In 93% of cases, there is visible fusion between two leaflets or cusps. The fusion point between them is termed a raphe and appears as a dysmorphic, partially formed commissure below the valve plane. Of bicuspid valves with a raphe, fusion between the right and left coronary cusps is most common (70%) (Fig. 30.3), followed by fusion of the right and non- coronary cusps (28%), and fusion of the left and noncoronary cusps (1.4%). Early development of aortic stenosis is a common com- plication in patients with a bicuspid aortic valve secondary to myxoid degeneration. This occurs in patients from 30 to 50 years, in contrast to senile aortic valve degeneration which occurs in patients 80 to 90 years old. Aortopathy and

Aortic Arch Anatomy and Variants

The aortic arch is a transverse segment from which the great vessels arise. The normal aortic arch is left sided and courses

Aorta

RA

R

L N

RA

LV

RV

LA

A

B

Figure 30.2.  Coronal view through the aortic root ( A ), left coronary artery ostium indicated by black arrow . Orthogonal cross section through the sinuses of Valsalva ( black line ) produces a transverse view of the right ( R ), left ( L ), and noncoronary ( N ) cusps ( B ). Note that the normal non- coronary cusp is directed toward the interatrial septum between the left atrium ( LA ) and right atrium ( RA ). RV, right ventricle; LV, left ventricle.