**6.1 Chest radiograph**

The CXR in ccTGA patients with mesocardia or levocardia typically demonstrates a straightened upper-left cardiac border from the leftward-positioned ascending aorta. Dextrocardia usually occurs with normal situs and, as stated previously, occurs in 20% of ccTGA patients (Figure 3). The presence of abdominal situs solitus and dextrocardia should raise suspicion of ccTGA. In the patient without any associated defects, an atypical cardiac position in an otherwise normal CXR may be the only indication of ccTGA.

Fig. 3. CXR of infant with dextrocardia, abdominal situs solitus, and ccTGA. Note the position of the cardiac apex pointed to the right. The left heart border demonstrates the prominent leftsided ascending aorta. The thymic shadow is seen over the right mediastinum.

However marked cardiomegaly, left atrial enlargement, and an increase in pulmonary vasculature may be present in patients with a large VSD and significant left to right shunt. A CXR with impressive cardiomegaly and left atrial enlargement may also be indicative of an Ebstein-like malformation of the TV. The presence of pulmonary stenosis or atresia will demonstrate darkened lung fields from attenuated pulmonary blood flow. Overall, the degree of cardiomegaly and amount of visible pulmonary vascularity is dependent on the

presence and direction of shunting, as well as the severity of LVOTO (Carey & Ruttenberg, 1964).

#### **6.2 Electrocardiogram**

166 Congenital Heart Disease – Selected Aspects

Interestingly, if there are no additional associated defects ccTGA may go unnoticed until adolescence or adulthood. Case reports have even cited incidental findings and late diagnoses of ccTGA in adults in the fifth to eighth decades of life (Chang et al., 2009; Jennings et al., 1984; Orchard et al., 2010; Scardi et al., 1999). A cohort of patients with ccTGA over 18 years of age who presented to an adult CHD clinic over a 15 year period is described by Beauchesne et al (2002). Sixty-six percent of these patients were over 18 years of age when diagnosed, and 17% of the cohort was over 60 years old at the time of diagnosis. Common reasons for referral in such patients range from abnormal ECGs and cardiomegaly on chest radiographs to complete

The CXR in ccTGA patients with mesocardia or levocardia typically demonstrates a straightened upper-left cardiac border from the leftward-positioned ascending aorta. Dextrocardia usually occurs with normal situs and, as stated previously, occurs in 20% of ccTGA patients (Figure 3). The presence of abdominal situs solitus and dextrocardia should raise suspicion of ccTGA. In the patient without any associated defects, an atypical cardiac position in an otherwise normal CXR may be the only indication of ccTGA.

Fig. 3. CXR of infant with dextrocardia, abdominal situs solitus, and ccTGA. Note the position of the cardiac apex pointed to the right. The left heart border demonstrates the prominent left-

However marked cardiomegaly, left atrial enlargement, and an increase in pulmonary vasculature may be present in patients with a large VSD and significant left to right shunt. A CXR with impressive cardiomegaly and left atrial enlargement may also be indicative of an Ebstein-like malformation of the TV. The presence of pulmonary stenosis or atresia will demonstrate darkened lung fields from attenuated pulmonary blood flow. Overall, the degree of cardiomegaly and amount of visible pulmonary vascularity is dependent on the

sided ascending aorta. The thymic shadow is seen over the right mediastinum.

**5.3 Late presentation and diagnosis** 

heart block and murmurs (Presberito et al., 1995).

**6. Evaluation** 

**6.1 Chest radiograph** 

The ECG in patients with ccTGA is most significant for a superior QRS axis and atypical septal activation. As discussed previously, the conduction system in ccTGA consists of inverted AV bundles. Therefore the septum is activated from right to left, demonstrating presence of septal Q waves in the right precordial leads (QR pattern in leads V4R and V1) and absence of Q waves in the left precordial leads (rS pattern in lead V6). In fact, undiagnosed ccTGA patients with such a pattern on ECG have been diagnosed with remote inferior infarcts (Jennings et al., 1984; Warnes, 2006). Preexcitation may be observed in those patients with ccTGA and Wolff-Parkinson-White. Finally, varying degrees of AV block may be present, as well as patterns of right or left-sided chamber enlargement.

### **6.3 Echocardiography**

Transthoracic echocardiography (TTE) as an imaging modality is relatively inexpensive, widely available, and noninvasive. As with many types of CHD, TTE is the first line and most useful modality in the diagnosis of ccTGA. The anatomical designation (most commonly {S,L,L} as discussed previously), is first assigned by demonstrating atrial position, ventricular looping, and arterial looping. Morphology of the RV is seen on TTE by the presence of coarse trabeculations and a moderator band, whereas the LV has a smoothwalled endocardium and a funnel-shaped appearance. The level of the TV is inferior to the MV, which may also give a clue to ventricular inversion. In evaluation of the outflow tracts, the aorta in ccTGA is usually anterior and to the left of the PA. Once the diagnosis of ccTGA is made through demonstration of discordance between atria and ventricles as well as ventricles and great arteries, several anatomic objectives should be defined in the TTE evaluation. Semilunar and AV valve morphology as well as presence and severity of regurgitation warrant full description. Coronary origins should be identified and their proximal courses described. The degree of LVOTO is important as well as any additional defects present, as these will impact whether and what type of surgical repair is necessary (Oechslin, 2009). Transesophageal echocardiography (TEE) has been shown to have greater accuracy over TTE in correctly defining atrial situs and chordal AV valve attachments in adult patients with ccTGA (Caso et al., 1998). TEE is also more useful for investigation of intracardiac vegetations in cases of suspected endocarditis and in evaluation of thrombus in the atrial appendages, which may be applicable to the ccTGA patient with sustained atrial arrhythmias.
