Congenitally Corrected Transpositon of the Great Arteries (CCTGA)
Ventricular inversion with L-TGA is also termed congenitally corrected transposition (CCTGA) because "two wrongs make a right" for the circulation in the setting of abnormal atrio-ventricular AND ventriculo-arterial connections - ie systemic venous return does appropriately go to the pulmonary arteries, but is via the subpulmonary LEFT ventricle instead of the right ventricle. Conversely, the pulmonary venous return is circulated to the aorta, but via the subaortic RIGHT ventricle (instead of left). This lesion is commonly accompanied by pulmonary valvar and/or subvalvar stenosis, ventricular septal defects and Ebsteinoid tricuspid valve abnormality.
ccTGA has a prevalence of 0.03 per 1000 live births and accounts for less than 1% of congenital heart disease.
Additional Findings
- Ventricular septal defect (70%)
- Pulmonary stenosis (40%)
- Tricuspid valve abnormalities (33%)
- Dextrocardia/mesocardia (17%)
- Ventricular hypoplasia (17%)
- Complete heart block (13%)
- Aortic arch abnormalities (10%)
- Re-entry tachycardia (7%)
Fetal Imaging
Establish Fetal Position
- This is a critically important assessment that must be performed prior to assessing cardiac anatomy
- Establishes what are right and left sided structures
- Establishes whether child levocardic, mesocardic or dextrocardic
AV Valves
Assess tricuspid valve morphology
- Evaluate for apical displacement of left sided AV valve and presence of septophilic attachments
- Evaluate right sided AV valve and presence of septophobic attachments
- Known association with Ebsteinoid tricuspid valve
Ventricles
- Assess the ventricular morphology
- Right ventricle is on the left side with features of a right ventricle
- Trabeculated appearance
- Associated with more apically displaced AV valve (tricuspid valve)
- Presence of moderator band
- Septophilic AV valve attachments
- Left ventricle is on the right side with features of a right ventricle
- Smooth walled
- More basally located AV valve (mitral valve)
- Septophobic AV valve attachments
Outflow Tracts
- Assess of the outflow tracts will reveal the pulmonary artery arising from the right-sided left ventricle and the aorta arising from the left-sided right ventricle
- Great arteries will appear to be in parallel with the aorta arising anteriorly and leftward to the pulmonary artery
- Pulmonary Valve
- Assess for pulmonary valve stenosis (given known association of PS)
- Assess pulmonary valve morphology (2D, color, spectral Doppler)
Aortic Arch
- Assess aortic arch size, flow (2D, color spectral Doppler) and arch sidedness
Fetal Rhythm
- Assess fetal heart rhythm (rate and type of rhythm) given risk for heart block (M-mode through atria and ventricles, M-mode in SVC/Aorta, inflow/outflow spectral Doppler)
- Should heart block be present assess for fetal Hydrops
Fetal Surveillance
- Follow up fetal imaging during pregnancy (usually every 4-6 weeks, but sometimes less frequently if normal rhythm, no PS or VSD)
- Close assessment of fetal rhythm (given risk of fetal heart block pre and postnatally), the growth of the aortic arch, evolution of TR, evaluate for pulmonary stenosis and assessment for VSDs and to evaluate ventricular function.
Fetal Councilling
- Genetics: Chromosomal abnormalites and extracardiac anomalies are rare. Referral to genetic councilling is reasonable.
- Surgical: Patients with VSDs +/- pulmonary stenosis or severe TR can be considered for a double switch operation. The atrial switch portion re-routes the pulmonary venous return to the LV and the systemic venous return to the RV, and the arterial switch transfers the aorta to arise from the LV and the pulmonary from the RV. For this surgery to be successful, the LV must be trained to handle the systemic workload either by sufficient PS or by placement of a pulmonary artery band with gradual tightening over time. In circumstances of these significant associated lesion, if performed before the age of 10 years, the double switch seems to be an effective option for physiologic repair. Problems with double switches can be multitudinous, however, including baffle obstruction, deformation/insufficiency of the aortic valve, LV dysfunction, and arrhythmias. Fetuses with isolated ventricular inversion/L-TGA with normal tricuspid valve, no PS and intact ventricular septum, there is not strong data currently to support that a PAB placement with subsequent double switch operation would provide a better quality or length of life. Theoretically, there is a significant advantage in having a systemic LV than RV, which can develop dysfunction over time. However, there are some patients with ccTGA are diagnosed incidentally, much later in life, even adulthood, without symptoms.
- Morbidity and Mortality: Poor long term prognostic factors include: Ebsteinoid tricuspid valve, degree of TR, systemic RV dysfunction and complete heart block.
Postnatal Considerations:
- Postnatally if the anatomy remains stable (no evidence of coarctation, pulmonary stenosis, VSD or significant tricuspid regurgitation), there is likely be no strong need or impetus for cardiac surgery in the neonatal period
- Patients with VSDs +/- pulmonary stenosis or severe TR can be considered for a double switch operation
- Patients who develop complete heart block prenatally or postnatally may require a pacemaker
- Isolated ccTGA (no PS, no VSD, no tricuspid valve or rhythm abnormalities) in general has an uneventful postnatal period and requires no immediate treatment
- Postnatally patient should be monitored closely in NICU or CVICU with postnatal echocardiogram, ECG and Holter monitor
References:
Paladini D, Volpe P, Marasini M, Russo MG, Vassallo M, Gentile M, Calabrò R. Diagnosis, characterization and outcome of congenitally corrected transposition of the great arteries in the fetus: a multicenter series of 30 cases. Ultrasound Obstet Gynecol. 2006 Mar;27(3):281-5.
Abuhamad A, Chaoui R. A Practical Guide to Fetal Echocardiography Normal and Abnormal Hearts. 2nd Edition. 2010.