• Note the relative orientation of the semilunar valves (Fig. 8-4). Typically, the AV is anterior and rightward of the pulmV, but can range from directly anterior to rightward and side by side.

• Note morphology of the semilunar valves. The intercoronary commissure of the AV should align with a commissure of the pulmV. If the commissures are not aligned, coronary transfer may be more difficult.

• Note any evidence of VSD. If one VSD is present, be sure to examine the remainder of the muscular septum for additional defects.

• Evaluate coronary artery anatomy: origins from the sinuses and proximal courses must be clearly visualized.

• Many variants are known, although the two most common patterns are present in about 80% of cases.

• Complex coronary artery patterns may substantially increase the risk of the arterial switch operation (ASO). Rarely, a complex coronary artery pattern precludes ASO.

• There are two major conventions for nomenclature, the Leiden convention (Fig. 8-5 and Table 8-1) and the descriptive approach advocated by cardiologists at Children’s Hospital Boston (Fig. 8-6).

• Typically, the coronary arteries arise from the two sinuses of the AV that are adjacent to or “face” the sinuses of the pulmV (see Fig. 8-4).

• In the most common pattern (1L, Cx; 2R) or “usual,” the left coronary artery (LCA) arises from the leftward facing sinus and gives rise to the anterior descending artery and circumflex artery (Cx) (Fig. 8-7). The right coronary artery (RCA) arises from the rightward facing sinus.

• In the second most common pattern (1L; 2R, Cx) or “circumflex from RCA,” the leftward facing sinus gives rise solely to the anterior descending, whereas the RCA, arising from rightward facing sinus, also gives rise to the Cx. The circumflex passes posterior to the pulmonary root to reach the left atrioventricular groove; this segment can often be visualized from the subcostal or apical four-chamber (4C) views (Fig. 8-8).

• Visualization of the coronary arteries is facilitated by decreasing the dynamic range and careful adjustment of focal zone and zoom features.

• Be alert for any evidence of intramural coronary artery (passing between the two GVs), which is rare, but can significantly complicate an ASO (Fig. 8-9). A “double border” appearance of the posterior aortic root is noted when a coronary artery passes between the aortic and pulmonary roots.

• Suprasternal notch views

• The usual assessment of arch sidedness and branching is performed. A right aortic arch is uncommon in d-TGA.

• Coarctation is rare unless evidence of right ventricular outflow tract (RVOT) (subaortic) obstruction (RVOTO) is present.

• A PDA is best seen in d-TGA in the sagittal view of the arch due to the parallel orientation of the GVs (Fig. 8-10). The PDA should be assessed for size, direction of shunting, and gradient.

• Short axis suprasternal notch views can sometimes be used to supplement coronary artery imaging, if the patient is positioned with a shoulder roll and significant neck extension.

• Transesophageal echocardiography (TEE)

• Given typically excellent transthoracic windows in neonates, TEE is essentially never used for initial diagnosis of d-TGA. TTE is superior for visualization of the GVs and PDA, which are key in this diagnosis.

• Depending on institutional practice, a preoperative TEE may be performed in the operating room. See Chapter 4, Intraoperative Transesophageal Echocardiography, for discussion.

• Three-dimensional (3D) imaging generally adds little information to the study, unless a complex muscular VSD is present, in which case 3D imaging can be used to evaluate its size and location.

Figure 8-2 A, This subcostal frontal image shows the branching pulmonary artery (PA) arising from the left ventricle (LV). The color Doppler panel shows flow into the PA (red), consistent with a patent ductus arteriosus (PDA). The left PA is not seen in this view. B, This subcostal sagittal view shows the entire course of the aorta (Ao), arising anteriorly from the right ventricle (RV). The PA parallels the aorta posteriorly. The ductus is patent with color Doppler seen from the aorta to the PA.

Figure 8-3 Parasternal long axis view demonstrating the parallel great vessels characteristic of d-TGA. There is fibrous continuity between the mitral valve and pulmonary valve.

Figure 8-4 Parasternal short axis (SAX) view showing the orientation of semilunar valves. In this case, the aortic valve (AV) is anterior and rightward, which is typical. The origins of the right and left coronary arteries are seen from the two sinuses “facing” the pulmV, although the origin of the circumflex coronary artery (Cx) is not demonstrated here.

Figure 8-5 A, Schematic diagram explaining the Leiden convention for numbering the sinuses of the AV to describe coronary artery anatomy. From the perspective of standing in the noncoronary sinus, looking from the AV toward the PA, the sinus on the right-hand side is 1 and that on the left-hand side is 2. Note that this convention is easily applied by the surgeon standing on the right-hand side of the patient. B, Schematic with numbering in echo view. The convention of diagnostic image display is such that cranial is behind the screen, and thus it can become confusing trying to envision oneself standing in the noncoronary sinus. It is easier to remember that sinus 1 is the more leftward and/or anterior facing sinus (depending on the relative orientation of the great vessels) and sinus 2 is the more rightward and posterior sinus. This figure shows the numbering of the sinuses from the parasternal short axis view of the two semilunar valves. RCA, right coronary artery; Cx, circumflex coronary artery; AD, anterior descending artery.

TABLE 8-1 ABBREVIATION CONVENTION USED IN THE LEIDEN CONVENTION FOR DESCRIBING CORONARY ARTERY ANATOMY

Symbols used are as follows:

1 = sinus 1

2 = sinus 2

R = right coronary artery

L = left anterior descending coronary artery; also designated by some authors AD, as it may not arise from the left.

Cx = circumflex coronary artery

Comma = major branches originate from a common vessel

Semicolon = major branches originate separately

Supplemental terms may be used to describe epicardial course and unusual origins.

The series of assigned symbols for any given anatomy are enclosed in parentheses. For example: “normal” or “usual” coronary arteries for d-TGA are designated (1L, Cx; 2R), meaning the left anterior descending and circumflex originate from a common vessel from sinus 1, whereas the right coronary artery arises separately from sinus 2.

Figure 8-6 The eight most common coronary artery patterns in d-TGA are shown as seen from the parasternal short axis echocardiographic view. The frequency of occurrence is shown in the corner of each panel. The Leiden convention symbols and the eponym assigned by the Boston convention are shown in each panel.

(Adapted from Figure 24.5 in Mertens LL, Vogt MO, Marek J, Cohen MS. Transposition of the great arteries. In: Lai WW, Mertens LL, Cohen MS, Geva T, eds. Echocardiography in Pediatric and Congenital Heart Disease, Hoboken, NJ: Wiley-Blackwell; 2009.)

Figure 8-7 The left main coronary artery and its bifurcation into the anterior descending artery and Cx are shown in this modified parasternal short axis view. Often some off-axis angulation is needed to demonstrate the course and bifurcation of the coronary arteries.

Figure 8-8 As demonstrated in Figure 8-6, when the Cx arises from the RCA (1L; 2R, Cx, or Cx from right coronary artery [RCA]), it reaches the left atrioventricular groove by a retropulmonary course. This may be difficult to see from the parasternal short axis view, but is usually readily evident from the subcostal frontal (shown here) or apical view.