Late Presentation of a Congenitally Corrected Transposition of Great Arteries and Hemodynamically Balanced Ventricles Associated with a Large Ventricular Septal Defect and Severe Pulmonary Stenosis: A Case Report and a Multi-Imaging Approach

Background

ccTGA is a rare congenital heart disease that represents less than 1% of all congenital heart diseases [1,2]. This malformation is characterized by atrioventricular (AV) discordance and ventriculo-arterial (VA) discordance (Figure 1). Various other terms anatomically describe this malformation: L-transposition, double discordance, and ventricular inversion.

The term “congenitally corrected” is used to differentiate this condition from complete transposition (dextro-TGA) in which there is VA discordance but AV concordance. Eighty percent of ccTGA patients have associated anomalies, mostly VSD, PS, and both [3,4]. Others include Ebstein’s anomaly, tricuspid regurgitation, and, less commonly, mitral regurgitation [5–21]; less than 1% have no associated lesions [6]. Isolated ccTGA is considered physiologically corrected as passage of oxygenated and deoxygenated blood to the lungs and systemic circulation remains normal. However, the systemic morphologically RV is in contact with the systemic circulation, resulting in mechanical difficulty that could appear with aging [7].

Case Report

A 40-year-old male, farmer, refugee, not known to have any medical illnesses, presented with NYHA class II dyspnea. Cardiac auscultation found a pan-systolic murmur, lungs were clear to auscultation, and oxygen saturation 94% on room air. Lab workup include hemoglobin 19.6 g, hematocrit 53%, platelets 219 g/l, WBC 6.6 g/l, normal electrolytes, NT-proBNP 35 pg/ml, normal renal function, and normal liver function. CXR showed clear lung fields, cardiomegaly, and dextrocardia (Figure 2). ECG revealed a QRS reversal pattern with dominant R wave but no Q wave in V6 and a first-degree AV block (Figure 3). TTE found atrioventricular and ventriculo-arterial discordances, lower displacement of the tricuspid valve indicative of Ebstein’s anomaly, and severe pulmonary stenosis with the pulmonary artery (PA) displaced to the right side of the aorta (Figure 4). TEE showed a pulmonary stenosis with malposition of the PA at the right side of the ascending aorta (Figure 5). Cardiac MRI showed a preserved bi-ventricular function and large VSD (≈ 3 cm), RV hypertrophy, and dilation at indexed RV volume of 129.4 ml/m2, increased RV trabeculations, PA dilation at 46 mm, no late gadolinium enhancement, and nonsignificant mitral regurgitation (Figures 6, 7). A CT scan showed dextrocardia with double discordance (Figure 8). A right heart catheter showed pulmonary protection with right atrial pressure 7 mmHg, pulmonary capillary wedge pressure (PCWP) 9 mmHg, left ventricular pressure (LVP) 130/12 mmHg, pulmonary artery pressure (PAP) 25/15 (8) mmHg, PA partial pressure of oxygen (pO2) 46.2 mmHg, and superior vena cava (SVC) pO2 34.7 mmHg. Stress testing showed low functional capacity, with maximal oxygen uptake at 13.3 ml/min/kg.

Surgical correction was not indicated in the presence of a hemodynamic balance, absence of significant tricuspid regurgitation, stable symptomatology, and pulmonary protection, despite the large VSD.

Discussion

The clinical presentation of ccTGA depends on the presence or absence of associated cardiac anomalies. In the pediatric population, developing cyanosis and heart failure is related to the severity of associated malformations like a significant VSD or pulmonary stenosis, which might need surgical correction. In the absence of associated defects, which is uncommon, the RV can maintain its function as the systemic pump at a “normal” level into adult life, but it tends to deteriorate gradually after the second decade of life [8].

RV dysfunction is common in middle-aged adults with ccTGA [9], and individuals without associated cardiac defects may survive over 50 years [10,11]. However, survival of unoperated patients until the fourth decade in the presence of large VSD is exceptional. Several multicentric studies found an increasing occurrence of heart failure with age. In the fourth decade of life, half of ccTGA patients with associated lesions and one-third of those without associated lesions present with dysfunction of the systemic RV [12,13].

Large VSDs are usually associated with pulmonary hypertension (PHT). However, we found pulmonary protection in our case due to pulmonary valve stenosis. The increased pressure in LV helps maintain TV leaflets coaptation by compressing the RV [14] and the same applies for pulmonary artery banding. This reduces the risk of developing severe tricuspid regurgitation (TR), which is strongly associated with RV dysfunction and CHF in ccTGA patients [3].Whereas it is extremely difficult to determine whether TR plays a major or a minor role [3], tricuspid valve repair is one of the surgical approaches that showed better survival for those with significant tricuspid regurgitation [15].

From an electrophysiological point of view, patients with ccTGA usually have a second AV node positioned anteriorly, which gives rise to an elongated AV bundle [16]. As a result, those patients are prone to have varying degrees of conduction abnormalities and re-entry tachycardia that manifest at any age from fetal life to late adulthood [17]. Diagnosis of ccTGA leading to complete heart block is well known [18]. The right bundle adheres to the RV and the left bundle adheres to the LV. Septal activation occurs in the opposite direction, from right to left [19]. Therefore, the ECG shows a mirror image pattern in the precordial leads, leading to a reversal of the normal QRS morphology, with Q waves in V1 and a dominant R wave but no Q wave in V6. In our patient, this mirror image pattern was partially evident with dominant R wave but no Q wave in V6 and absence of Q waves in V1, probably related to the RV hypertrophy. P waves and QRS axis vary depending on the atrial arrangement and location of the AV node and proximal conducting bundles [20]. Another anatomical finding in our case was the associated dextrocardia, which is not a common association [21].

Conclusions

Patients with ccTGA can live for years without diagnosis. The prognosis depends largely on the ability of the RV to adapt to the systemic circulation. Surgical correction is achieved mainly by reverting the ventricles, and its indication relies on a multimodality imaging approach and exhaustive hemodynamic assessment. The presence of pulmonary stenosis can provide a physiological protection that avoids unnecessary surgical correction.