**6.4 Cardiac catheterization**

Rather than a modality for diagnosis, cardiac catheterization (Figure 4) is typically reserved for the post-surgical patient who would benefit from an intervention such as LV to pulmonary artery (PA) conduit dilation or stent placement. For patients undergoing surgical palliation for single-ventricle ccTGA anatomy, catheterization is performed to assess pressure, function, and valve regurgitation prior to surgery. Most interesting, however, is the adult patient who presents with ischemic heart disease and is discovered on cardiac catheterization to have ccTGA after abnormal catheter passes or inversion of coronary arteries on angiography (Jennings et al., 1984).

Congenitally Corrected Transposition of the Great Arteries 169

Cardiac MRI is now used in many types of CHD to further define anatomy and to quantify ventricular function and volume (Figure 5). For initial diagnosis, cMRI may be helpful in patients with restricted TTE windows, to define visceroatrial situs, and to delineate complex associated defects. In patients with interruption of the inferior vena cavae, systemic return from the lower body can be difficult to delineate by echocardiography, but is well defined by cMRI. Because echocardiographic evaluation of RV function in ccTGA patients is limited by geometric assumptions, cMRI has become the gold standard for RV function and volume assessment. TV morphology as well as degree of regurgitation can also be determined through cMRI. Prior to performing anatomic surgical repair in a ccTGA patient beyond infancy, cMRI may be useful in evaluation of LV mass, volume, and ejection fraction. Furthermore, if there are concerns about degree of LV dysfunction, perfusion studies with delayed enhancement MRI may be performed to directly investigate scarring of the LV myocardium prior to committing this ventricle to systemic workload. Cardiac MRI may therefore be a useful modality for evaluation of ccTGA patients not only as an adjunct to TTE for initial diagnosis, but also for assessment prior to surgical repair and serial follow-up of the systemic RV. If the presence of MRI-incompatible pacemaker or prosthetic valve precludes assessment by MRI, computed tomography (CT) scans can depict anatomy but

cannot yield functional data as does MRI (Schmidt et al., 2000; Teo & Hia, 2011).

Fig. 5. Oblique cut T2-weighted MRI image of 4-chamber cardiac view of ccTGA patient with levocardia. The RA empties into a right-sided, smooth-walled, morphologic LV. A star (\*) labels the entrance of a right pulmonary vein into the left atrium, which empties into a trabeculated, left-sided, morphologic RV. RA, right atrium; LV, left ventricle; LA, left

atrium; RV, right ventricle.

**6.5 Cardiac Magnetic Resonance Imaging (cMRI)** 

Fig. 4. Cardiac catheterization of ccTGA infant with dextrocardia, pulmonary stenosis, and VSD (same infant as in Fig. 3). (A.) Anterior-posterior projection. A catheter is positioned in the right-sided morphologic left ventricle (LV). Contrast fill the LV, pulmonary trunk, and pulmonary arteries. Contrast flows right to left across the VSD (arrow) and fills the aorta. (B.) Lateral projection. Contrast from the LV flows through the LV outflow tract, across the pulmonary valve, and fills the pulmonary arteries. The aorta fills by right to left shunting through the VSD. Note the aorta is anterior to the pulmonary artery. (C.) Anterior-posterior projection. A catheter is positioned retrograde into the left-sided morphologic right ventricle (RV). Contrast fills the trabeculated RV and the leftward aorta. (D.) Lateral projection. Contrast fills the large RV, ascending, and descending aorta. LV, left ventricle; RV right ventricle; Ao, Aorta; aAo, ascending aorta; dAo, descending aorta; MPA, Main pulmonary artery; PA, Pulmonary artery.

Fig. 4. Cardiac catheterization of ccTGA infant with dextrocardia, pulmonary stenosis, and VSD (same infant as in Fig. 3). (A.) Anterior-posterior projection. A catheter is positioned in the right-sided morphologic left ventricle (LV). Contrast fill the LV, pulmonary trunk, and pulmonary arteries. Contrast flows right to left across the VSD (arrow) and fills the aorta. (B.) Lateral projection. Contrast from the LV flows through the LV outflow tract, across the pulmonary valve, and fills the pulmonary arteries. The aorta fills by right to left shunting through the VSD. Note the aorta is anterior to the pulmonary artery. (C.) Anterior-posterior projection. A catheter is positioned retrograde into the left-sided morphologic right ventricle (RV). Contrast fills the trabeculated RV and the leftward aorta. (D.) Lateral projection. Contrast fills the large RV, ascending, and descending aorta. LV, left ventricle; RV right ventricle; Ao, Aorta; aAo, ascending aorta; dAo, descending aorta; MPA, Main pulmonary

artery; PA, Pulmonary artery.

#### **6.5 Cardiac Magnetic Resonance Imaging (cMRI)**

Cardiac MRI is now used in many types of CHD to further define anatomy and to quantify ventricular function and volume (Figure 5). For initial diagnosis, cMRI may be helpful in patients with restricted TTE windows, to define visceroatrial situs, and to delineate complex associated defects. In patients with interruption of the inferior vena cavae, systemic return from the lower body can be difficult to delineate by echocardiography, but is well defined by cMRI. Because echocardiographic evaluation of RV function in ccTGA patients is limited by geometric assumptions, cMRI has become the gold standard for RV function and volume assessment. TV morphology as well as degree of regurgitation can also be determined through cMRI. Prior to performing anatomic surgical repair in a ccTGA patient beyond infancy, cMRI may be useful in evaluation of LV mass, volume, and ejection fraction. Furthermore, if there are concerns about degree of LV dysfunction, perfusion studies with delayed enhancement MRI may be performed to directly investigate scarring of the LV myocardium prior to committing this ventricle to systemic workload. Cardiac MRI may therefore be a useful modality for evaluation of ccTGA patients not only as an adjunct to TTE for initial diagnosis, but also for assessment prior to surgical repair and serial follow-up of the systemic RV. If the presence of MRI-incompatible pacemaker or prosthetic valve precludes assessment by MRI, computed tomography (CT) scans can depict anatomy but cannot yield functional data as does MRI (Schmidt et al., 2000; Teo & Hia, 2011).

Fig. 5. Oblique cut T2-weighted MRI image of 4-chamber cardiac view of ccTGA patient with levocardia. The RA empties into a right-sided, smooth-walled, morphologic LV. A star (\*) labels the entrance of a right pulmonary vein into the left atrium, which empties into a trabeculated, left-sided, morphologic RV. RA, right atrium; LV, left ventricle; LA, left atrium; RV, right ventricle.

Congenitally Corrected Transposition of the Great Arteries 171

radiographs, and had moderate to severe or severe systemic AV valve regurgitation. The ejection fraction of the systemic ventricle between the operated and unoperated groups was not statistically significant (Beauchesne et al., 2002). As discussed previously and depicted in Figure 2, nearly 2/3 of unrepaired ccTGA patients with associated defects will have developed CHF by the age of 45 years. Even asymptomatic adults with ccTGA have been shown by echocardiography to have RV dysfunction through the use of tissue Doppler quantification techniques (Bos et al. 2006). Thus the natural evolution of ccTGA for the majority of patients is eventual RV dysfunction and TV regurgitation. It is postulated that progression to failure in a systemic RV is unavoidable because the RV and TV are not anatomically suited to withstand the systemic pressure for which the LV and MV are intended. One mechanism thought to contribute to progressive RV decompensation is worsening TR from annular dilation and/or displacement of the septal leaflet of the TV as

Table 1. ccTGA {S,L,L} Surgical Repair and Palliation. VSD, ventricular septal defect; PS, pulmonary stenosis; PA, pulmonary artery; PV, pulmonary valve; RV, right ventricle; TR,

Depending on the age of presentation and extent of associated lesions, surgical repair may include one or more of several approaches (Table 1). In patients with a VSD and no LVOTO, "classic" or "physiologic" repair may include VSD closure only. Specific techniques must be employed in ccTGA patients to avoid damage to the conduction system during VSD closure. Because the AV conduction bundle descends along the anterior rim of the VSD and travels along the septal side of the right-sided morphologic LV, it is recommended to suture the VSD patch along the morphological right ventricular aspect of the septum. The surgical approach should be via right atriotomy and right-sided mitral valve. Ideally the VSD patch will lie partially on the morphologic LV septal aspect (to avoid damage to the TV superiorly) and partially on the morphologic RV aspect of the septum inferiorly (to avoid damage to the main conduction bundle) (Jonas, 2004). Physiologic repair may also include relief of

the RV remodels to accommodate systemic afterload.

tricuspid regurgitation; BDG, Bidirectional Glenn
