Echocardiographic Approach to Congenitally Corrected Transposition
Maitri Chaudhuri1, Munesh Tomar2 1 Department of Pediatric Cardiology, Manipal Hospital, Bengaluru, Karnataka, India 2 Department of Pediatrics, LLRM Medical College, Meerut, Uttar Pradesh, India
Date of Submission
Date of Acceptance
Date of Web Publication
Correspondence Address: Dr. Maitri Chaudhuri Department of Pediatric Cardiology, Manipal Hopsital, #98, HAL Airport Road, Bengaluru - 560 017, Karnataka India
Source of Support: None, Conflict of Interest: None
The hallmark of corrected transposition is discordance at atrio-ventricular and ventriculo-arterial level and that is defined as “double discordance”. This can occur as an isolated anomaly but more commonly has associated defects; most common being ventricular septal defect followed by tricuspid valve abnormalities. Other associated defects are pulmonary stenosis, systemic and pulmonary venous anomalies, univentricular physiology, ventricular dysfunction (morphological right ventricle facing systemic circulation) and association of conduction abnormalities. Echocardiography plays a pivotal role in defining the anatomy and planning the management. In this article we are discussing about role of echocardiography in evaluation of corrected transposition, diagnosing the lesion, role in immediate post-operative period and on follow up.
How to cite this article: Chaudhuri M, Tomar M. Echocardiographic Approach to Congenitally Corrected Transposition. J Indian Acad Echocardiogr Cardiovasc Imaging 2020;4:312-24
How to cite this URL: Chaudhuri M, Tomar M. Echocardiographic Approach to Congenitally Corrected Transposition. J Indian Acad Echocardiogr Cardiovasc Imaging [serial online] 2020 [cited 2021 Apr 13];4:312-24. Available from: https://www.jiaecho.org/text.asp?2020/4/3/312/303941
Circa 1875: Baron Von Rokitansky described a congenital cardiac anomaly demonstrating the most unexpected combination of different cardiac segments. It was named as congenitally corrected transposition of great arteries (CCTGA) with a prevalence of reportedly 1/13,000 live births or roughly only 0.05% of clinically diagnosed congenital heart disease.,, It is the prototype model to analyze the segmental approach in congenital echocardiography.
The hallmark of this interesting malady is “double discordance” or a combination of atrioventricular and ventriculoarterial (VA) discordances in the presence of situs solitus or situs inversus. These discordances or “inappropriate connections” should not be labeled as CCTGA in the presence of isomerism or univentricular atrioventricular connection.
Here, the right atrium (RA) is connected to morphological left ventricle (LV), which, in turn, gets discordantly connected to pulmonary artery (PA). The left atrium (LA) is similarly connected to morphological right ventricle (RV) and latter to aorta (Ao). Although anatomically discordant, the double discordances physiologically nullify each other and the circulatory pattern is similar to normal heart. Hence, it was named as “corrected TGA.”
This is to highlight the difference from complete TGA, which involves discordance at only one level, namely, the VA junction. Here, deoxygenated blood streams to Ao and oxygenated blood to lungs. It is a critical neonatal cyanotic heart disease, making survival impossible without adequate mixing at atrial, ventricular, or ductal levels.
The following schematic diagrams depict a normal heart [Figure 1]a, complete transposition [Figure 1]b, and corrected complete transposition [Figure 1]c in sequence for better understanding.
Figure 1: (a) A schematic diagram representing the normal blood flow pattern. Deoxygenated blood via superior and IVC flows to the RA and then received by subpulmonic RV. The same is pumped to both the lungs for oxygenation. The pure oxygenated blood reaches the left heart; LA and LV in sequence and circulates to the whole body via Ao. This relationship between atria > ventricles > great arteries is called AV and VA concordance or normal connections. (b) A schematic diagram representing the blood flow pattern in complete TGA. Deoxygenated blood via superior and IVC flows to the RA and then received by subpulmonic RV. However, this deoxygenated blood now flows to systemic circulation as Ao is connected to RV. Oxygenated blood from the lungs reaches left heart; LA and LV in sequence and returns back to the pulmonary circulation. This abnormal connection between ventricles and great arteries is called VA discordance, a classical example of critical neonatal cyanotic heart disease. (c) The third schematic diagram in this series shows the unique association of AV and VA discordances where deoxygenated blood reaches RA but is then received by subpulmonic LV. This is the first discordance: Namely AV discordance. As PA is again discordantly connected to LV, ultimately deoxygenated blood gets purified in lungs. Similarly, oxygenated blood to LA is received by subaortic/systemic RV and is then pumped to the whole body by Ao. This “wrong connection” between ventricles and aorta is the second discordance: VA discordance. Thus, AV + VA discordance = Double discordance/CCTGA. Left panel shows CCTGA with normal atrial arrangement or situs solitus, right panel shows the same with mirror image atrial arrangement/situs inversus. RA: Right atrium, RV: Right ventricle, LA: Left atrium, LV: Left ventricle, Ao: Aorta, TGA: Transposition of great arteries, VA: Ventriculoarterial, AV: Atrioventricular, PA: Pulmonary artery, CCTGA: Congenitally corrected transposition of great arteries, IVC: Inferior vena cava
L (levo)-transposition or L-TGA is not synonymous with CCTGA. As shown in [Figure 1]c, CCTGA with situs inversus will have right-sided Ao.
Second, “L” also stands for “L-looping” of the prior straight embryonic heart tube. The reader has to ascertain whether the echocardiographer is referring to spatial arrangement of great arteries at their origin or L-looping of ventricles. We, thereby, suggest using more specific terminologies such as atrioventricular (AV) discordance and VA discordance.
Physiology and Hemodynamics
Physiologically speaking, CCTGA is “nature's own remedy” or “congenital correction”) to double discordance and consequently the patient should be asymptomatic. Isolated CCTGA represents a circulation in series without mixing. In reality, this is the exception rather than the norm. In 90% of these hearts, there are associated major malformations.,,,,, Of these, the three most common lesions are ventricular septal defect (VSD), pulmonary stenosis (PS), and morphological tricuspid regurgitation (TR). [Figure 2] shows a statistical representation of the same.
Figure 2: A quick recap of associated lesions in CCTGA via pie chart. The most common lesion is VSD (represented in blue) which is followed in descending order by pulmonary stenosis (color coding red), clinically significant morphological tricuspid valve anomalies (colored gray, autopsy prevalence is much higher than clinical prevalence) and conduction blocks (color code yellow). CCTGA: Congenitally corrected transposition of great arteries, VSD: Ventricular septal defect
In CCTGA, the pulmonary valve is wedged between the interatrial septum (IAS) and mitral valve, thus deviating the IAS from the interventricular septum (IVS). With atrial situs solitus, there is a unique situation of “dual AV node.” Complete heart block (CHB) is a consequent sequel [Figure 3]. In utero or neonatal heart block is rare. Risk of CHB at birth is 5%–10% and with an annual increment at 2% every year. The all age group incidence of CHB is 30% and all types of AV block is 75%. Detection of bradycardia and syncope of cardiac failure will be presenting features with the development of heart block.,
Figure 3: ECG showing complete AV block with junctional escape rhythm with a rate of 35/min. Sinus rate was 54/min. Q waves in the inferior and right chest leads and absence of q waves in V5–6 are the features of typical CCTGA. ECG: Electrocardiogram, CCTGA: Congenitally corrected transposition of great arteries, AV: Atrioventricular
Echocardiography is a specific, diagnostic, noninvasive, nonradiating, repetitive, widely available modality utilized as one of the first-line investigations in every patient with suspected CCTGA.,,,
Step-By-Step Echo in Diagnosing Congenitally Corrected Transposition of Great Arteries
We, hereby, request the clinician to remember the morphology described before and demonstrate the same during doing an echo [Table 2] and [Table 3]. A continuous electrocardiogram recording during echo will also help assess cardiac rate and rhythm simultaneously.
Table 2: Role of echo in corrected transposition of great arteries
As in any pediatric echo, we begin by assessing the situs. This is best assessed in subcostal view in infants and young children. For adults, if the operator encounters poor transthoracic window, he/she can utilize clinical examination and chest X-ray when in doubt.
Abdominal situs solitus: Stomach bubble on the left of spine, liver on its right, Ao on the left, and inferior vena cava (IVC) coursing through liver on the right
Atrial situs is diagnosed by IVC draining into RA and more specifically by morphology of atrial appendages [Figure 6]a and [Figure 6]b. Right atrial appendage is short, fat, and broad based, best seen in the subcostal sagittal view, while left atrial appendage is long, narrow, and finger shaped, best seen in the apical four-chamber and parasternal short axis.
Figure 4: A comparison of chest X-ray of CCTGA with situs solitus and situs inversus (a) CCTGA with levocardia; (b): CCTGA with dextrocardia. The arrow in frontal chest X-ray in left panel depicts a convexity of left upper cardiac border which is formed by “L or Levo positioned” ascending aorta taking origin from left sided morphological RV. These are more obvious in older children and adults. Kindly note L-posed aorta is not unique to CCTGA alone. CCTGA: Congenitally corrected transposition of great arteries, RV: Right ventricle
Figure 5: (a) Subcostal coronal echocardiographic view demonstrating the classical appearance of situs solitus. First identify the spine in midline and then focus on the two vascular structures on its two sides. IVC is on the right of the sine, collapsible, moves with respiration and shows phasic venous waveform in Doppler. Aorta (Ao) is on the left side, pulsatile and Doppler shows typical arterial waveform. In addition to this, demonstrating liver on the right and stomach bubble on the left confirms the abdominal situs solitus. (b) Situs inversus is diagnosed on echo by just the reverse orientation of vascular structures (IVC and Aorta to the spine) and similarly reverse location of stomach bubble and liver. IVC: Inferior vena cava
Figure 6: (a and b) TEE of a 24-year-old female with CCTGA. TEE beautifully elucidated the difference between right and left atrial appendages. Appendage is the signature and most reliable landmark identifying atrium. Please note the text for differentiating between right and left atrial appendages. TEE: Transesophageal echocardiography, CCTGA: Congenitally corrected transposition of great arteries, RA: Right atrium, RAA: Right atrial appendage, LA: Left atrium, LAA: Left atrial appendage, Ao:Aorta
The correct identification of atria is mandatory to establish our diagnosis of “AV discordance.”
Step 2: Apex of the heart
Continue in the subcostal view: Cardiac apex pointing toward the left is called levocardia, apex pointing toward the right is dextrocardia, and midline apex is mesocardia [Figure 7]a,[Figure 7]b,[Figure 7]c and [Video 2]. Abnormal position of heart in thorax should always raise the suspicion of CCTGA as 25% of CCTGA hearts have either dextro or mesocardia. In mesocardia, majority of the cardia is beneath the sternum. Hence, precordial echo windows have limited penetration. Subcostal and suprasternal views in infants and transesophageal echo in adults will give additional information.
Figure 7: Two-dimensional echocardiography from subcostal coronal view showing different cardiac positions (a) Dextrocardia (b) Mesocardia (c) Levocardia
After establishing atrial anatomy, now, we have to demonstrate that the “atria is connected to the wrong ventricle.” Morphological RA is connected by mitral valve to morphological LV and vice versa on the left side [Figure 8]. To identify this, let us recap the basic identification of valves and ventricles:
Figure 8: Apical four-chamber echocardiogram demonstrating atrioventricular discordance. Kindly note the abnormally lower offset of morphological TV as compared to morphological MV. Another very important echocardiographic clue is the malalignment between IAS and IVS. RA: Right atrium, LA: Left atrium, TV: Tricuspid valve, MV: Mitral valve, LV: Left ventricle, RV: Right ventricle, IAS: Interatrial septum, IVS: Interventricular septum
Malalignment between IAS and IVS is an echo pointer of AV discordance. We should actively search for CCTGA if this pointer is seen in echo frames. However, not all CCTGA will have this.
Usually, in these hearts, the ventricles are “side by side” with added superoinferior orientation ventricles due to malrotation around the long axis of the heart. Apical four-chamber imaging is more challenging when the ventricles are superoinferior. Here, both AV valves cannot be imaged in the same plane. In this setting, the transducer will need to be tilted inferiorly to see the right-sided mitral valve and superiorly to see the left-sided tricuspid valve. The septal hinge point relationship is more difficult to appreciate. The diagnosis of CCTGA in these patients relies on the other features which define ventricular morphology.
In extreme cases, “criss-cross” ventricles are also seen.
These echo features will be best seen in apical four-chamber view followed by subcostal imaging.
This is best understood from subcostal views. There are two clues:
Great arteries are parallel and not crossing each other
PA is arising from morphological LV and Ao from morphological RV.
The flow, nature of semilunar valves, presence, mechanism and severity of outflow tract obstruction, annular sizes, size of Ao, right ventricular outflow tract, pulmonary trunk, and its branches all have to be looked carefully [Figure 9] and [Figure 10].
Figure 9: Subcostal coronal view with anterior upward tilt of transducer demonstrating muscular VSD (arrow) and subvalvar pulmonary stenosis due to a jutting fibromuscular shelf (star). This if pointed out in preoperative echo or TEE can be surgically resected and aids in biventricular repair. Kindly note that great vessels are not crossing each other and are rather oriented parallelly arising from “wrong ventricles.” This proves the second discordance in CCTGA namely “ventriculoarterial discordance.” Ao: Aorta, PT: Pulmonary trunk, CCTGA: Congenitally corrected transposition of great arteries, VSD: Ventricular septal defect, TEE: Transesophageal echocardiography, RA: Right atrium, MV: Mitral valve, LV: Left ventricle
Figure 10: Subcostal coronal view with anterior upward tilt of transducer showing parallel Aorta and pulmonary trunk with aorta to left of main pulmonary artery. This 11-month child with CCTGA had no VSD. CCTGA: Congenitally corrected transposition of great arteries, VSD: Ventricular septal defect, RA: Right atrium, LV: Left ventricle, RV: Right ventricle, MPA: Main pulmonary artery
CCTGA is not a lesion which occurs with isolation. The three most common and most significantly associated lesions in CCTGA are VSD, PS, and morphological TR. In the following lines, we discuss each of these from echocardiographer's eye.
Ventricular septal defect
It is the most common lesion, noted in 60%–80% of cases. Patients with isolated large VSD present with features of CHF. Associated TR causes early presentation and increased severity of symptoms. The most common type of VSD is “perimembranous VSD” bordered by fibrous continuity between mitral–pulmonary and tricuspid valves. Hence, the defect is visualized in four-chamber view in the “inlet septum.” The absence of inlet septum masks the differential offsetting of AV valves. This is an important challenge to diagnose AV discordance by echo [Figure 9], [Figure 11] and [Figure 12]. Furthermore, overriding or straddling of AV valves needs to be looked into in these situations as they decide suitability of biventricular versus univentricular repair.
Figure 11: Apical four-chamber view demonstrating the perimembranous VSD in CCTGA opening into the inlet septum. This inlet dropout makes it difficult to differentiate the offsetting distinguishing mitral and tricuspid valves. Here, moderator band (white star in picture) is a landmark identifying the RV. CCTGA: Congenitally corrected transposition of great arteries, VSD: Ventricular septal defect, RV: Right ventricle, RA: Right atrium, MV: Mitral valve, LV: Left ventricle, LA: Left atrium, TV: Tricuspid valve
Figure 12: (a) CCTGA with subcostal view showing perimembranous VSD with fibrous continuity between morphological mitral and pulmonary valves. (b) The VSD with RV focused view demonstrating anterior and left aorta arising from morphological RV. The echocardiographer should notice that in this heart there is no straddling or overriding of AV valves. CCTGA: Congenitally corrected transposition of great arteries, VSD: Ventricular septal defect, RV: Right ventricle, AV: Atrioventricular, RA: Right atrium, LV: Left ventricle
Additional VSDs such as doubly committed (in Asian ethnicity), remote muscular VSD, and AV canal-type VSDs are rare but reported and should be excluded during preoperative echo
The location, size, number, pressure gradient, shunting pattern of VSD, and its relation to neighboring cardiac structures are to be recorded.
Morphological LV outflow tract obstruction seen in 30%–50%. This is more often seen in CCTGA with situs solitus than with situs inversus. The incidence of isolated PS is <20%, PS with VSD is around 80%, and PS with TR is ~ 33%. Patients with VSD and PS present as TOF physiology.
The echocardiographer should employ all views, especially subxiphoid, parasternal, and apical views to document the presence of LVOT obstruction, the mechanism behind it [Figure 13], [Figure 14]a and [Figure 14]b and [Table 4], severity by Doppler gradients, and the sizes of pulmonary annulus. This helps in surgical planning for double switch (atrial + arterial switch) or procedure (atrial switch operation + Rastelli combination). The immediate and long-term success depends on this vital preoperative data.
Figure 13: Different mechanisms of left ventricular outflow tract obstruction in CCTGA. (1) Pulmonary valvar stenosis, (2) Tissue Tags, (3) Fibrous Shelf. RA: Right atrium, RV: Right ventricle, LA: Left atrium, LV: Left ventricle, PA: Pulmonary artery, Ao: Aorta
Figure 14: Two simultaneous subcostal echocardiograms. (a) Simultaneous two-dimensional and color Doppler showing the domed pulmonary valve guarding the pulmonary orifice in VA discordance with CCTGA. A small subvalvar shelf is also present. LV: Left ventricle, RV: Right ventricle, PA: Pulmonary artery, curved arrow – valvar pulmonary stenosis, PS: Pulmonary stenosis represented by mosaic turbulent flow across PA. Kindly compare it with laminar flow in aorta. This surgical anatomy will be difficult for arterial switch operation. (b) Continuous wave Doppler across pulmonary outflow in CCTGA showing severe pulmonary stenosis with peak PG of 120 mm Hg. CCTGA: Congenitally corrected transposition of great arteries
Subcostal coronal view, apical four-chamber view, RV-focused view, and parasternal long axis (PLAX) are helpful in delineating the structure and function of tricuspid apparatus. The echo report should clearly document tricuspid annulus, length and width of tricuspid leaflets, and morphology of tricuspid valve apparatus. These can be Ebstein's anomaly [Figure 15], dysplastic leaflets [Figure 16]a and [Figure 16]b, and cleft tricuspid valve [Figure 17]. The subvalvar apparatus needs to be examined for the presence of straddling or overriding of TV. Transthoracic and if required transesophageal echo with three-dimensional reconstruction help the surgeon to formulate a customized individual case-based correction of TR.
Figure 15: This apical four-chamber echocardiogram of a 6-week-old boy with CHF in CCTGA showed severe TR due to Ebstenoid malformation of tricuspid valve. Kindly note the characteristic displacement of hinge point of TV and exaggerated off setting between mitral and tricuspid valve. Another interesting feature is sail like anterior leaflet and arterialized RV are unusual unlike classical Ebstein's anomaly. This infant needed tricuspid valve repair with annuloplasty ring for refractory CHF. CCTGA: Congenitally corrected transposition of great arteries, TR: Tricuspid regurgitation, CHF: Congestive heart failure
Figure 16: Simultaneous two-dimensional (a) and color Doppler echocardiogram (b) demonstrating severe regurgitation of morphological TV. Here the tricuspid valve was found dysplastic preoperatively. TV: Tricuspid valve, IVS: Inter ventricular septum, RV: Right ventricle, LA: Left atrium, TR: Tricuspid regurgitation
Figure 17: A comparison of PLAX echocardiograms in normal heart versus heart with CCTGA. (a) normal PLAX view showing left atrium connecting to LV via mitral valve with IVS partitioning LV from RV. The aorta originates from LV and pulmonary artery cannot be visualized simultaneously here as in normal great vessel relationship, the aorta and pulmonary artery cross each other. Hence, they are not visualized simultaneously in the same two dimensional frame. (b) PLAX view of CCTGA with transducer position in same orientation showing LA connected via tricuspid valve to right ventricle. The IVS is intact. The anteriorly placed LV is draining into pulmonary artery. Long-axis view of RV shows the origin of aorta. An abnormal PLAX view should always raise the suspicion of abnormal origin of great vessels. We acknowledge the imaging will be difficult in adult CCTGA especially with mesocardia/dextrocardia. PLAX: Parasternal long-axis views, CCTGA: Congenitally corrected transposition of great arteries, LV: Left ventricle, IVS: Interventricular septum, RV: Right ventricle, LA: Left atrium
Subaortic obstruction and coexistent coarctation, interruption, aortic atresia, and hypoplasia of LV are other anomalies. Atrial septal defect (ASD) may be found in 20% of patients with CTGA.
Step 6: Assessing systemic right ventricular performance
The challenges in assessing RV function by echo are as follows:
Cardiac sequence arrangement is complex
Cardia is often substernal due to mesocardia
Presence of significant TR is a confounding variable
Furthermore, unlike LV with its longitudinal and circumferential fibers, the RV is mainly supported by longitudinal fibers coursing from its apex to right AV junction.
Therefore, quantification of systemic RV function by traditional or advanced echo in CCTGA is different and difficult than systemic LV or even subpulmonic RV.
Assessment of Right Ventricle Function: Tips and Tricks
We suggest to employ the patient's previous echocardiograms as control
Serial longitudinal echocardiograms of the same individual demonstrating a trend of worsening tricuspid annular plane excursion (TAPSE), fractional area change (FAC), RV myocardial performance index (MPI), RV S' velocities in tissue Doppler, isovolumic acceleration time, and strain imaging should raise “red flags” in the mind of cardiologist
Qualitative estimation by eyeballing is often practiced by experienced echocardiographers.
Correlation with cardiac MRI and radionuclide ventriculography is always helpful in assessing systemic RV function in this situation.
Parasternal Long-Axis View in Congenitally Corrected Transposition of Great Arteries: A Cryptic Challenge in Congenitally Corrected Transposition of Great Arteries
Adult echocardiography often begins with PLAX view, demonstrating aortic root/LA ratio in M-Mode and assessment of RV/LV study by M-Mode Teichhol's method. This is exactly where the PLAX view will appear like a crossword puzzle to the sonographer.
We now compare two transthoracic PLAX views of normal heart (VA concordance) versus CCTGA (VA discordance) [Figure 17]a and [Figure 17]b. A deformed PLAX view in adult echocardiography should always raise a “red flag” to the cardiologist. Kindly restart segment by segment echo, utilize the help of subcostal view, and/or use TEE and other imaging modalities.
Parasternal short-axis views in congenitally corrected transposition of great arteries: “The all-weather friend”
As in other pediatric hearts, high PSAX provides quick and additional identification of ventriculoarterial relationship. The left and anteriorly placed Ao with posterior PA is seen in majority of CCTGA with situs solitus (90% of cases) [Figure 18]a and [Figure 18]b.
Figure 18: Parasternal short-axis view in CCTGA. (a) Left panel (a): Classical L posed Ao to the left and anterior; PA bifurcating into confluent branches right and posterior. Right panel (b) Computed tomography angiogram in same adult CCTGA patient demonstrating the anatomical details with more precision. (b) High PSAX at level of semilunar valve origin view of an infant with CCTGA showing almost antero-posterior semilunar valves with AoV slightly to left and anterior and pulmonary valve to right and posterior. Ao: Aorta, AoV: Aortic valve, SV: Superior vena cava, MP: Main pulmonary artery, RP: Right pulmonary artery, LP: Left pulmonary artery, AoA: Ascending aorta, CCTGA: Congenitally corrected transposition of great arteries, PSAX: Parasternal short-axis views, PV: Pulmonary valve, PSAX: Parasternal short axis
Conversely, dextro (right) and anteriorly placed Ao with posterior PA will be the hallmark in CCTGA with situs inversus [Figure 19]. Thus, the presence of D-TGA at PSAX view does not necessarily mean complete transposition. Occasionally, the great arteries may be side by side.
Figure 19: PSAX view in a CCTGA infant with situs inversus showing Ao to right and anterior and PA to left and posterior. Only segmental approach will guide the echocardiographer that this is not complete TGA. TGA: Transposition of great arteries, CCTGA: Congenitally corrected transposition of great arteries, Ao: Aorta, PA: Pulmonary artery, PSAX: Parasternal short-axis views
This view is also used for coronary artery anatomy, especially if planned for double switch surgery, 85% of CCTGA hearts will have inverted coronary arteries. A single coronary artery is also a common accompaniment. If in doubt, we recommend use of additional imaging modalities such as CT angiography or direct coronary angiograms [Figure 20].
Figure 20: Direct coronary angiograms in adult CCTGA demonstrating mirror image coronaries with role reversal. (a) Left coronary artery. (b) RCA bifurcating and arrow pointing to anterior interventricular artery. We recommend the use of multimodality imaging in delineating coronary anatomy especially if double switch operation is planned. CCTGA: Congenitally corrected transposition of great arteries, RCA: Right coronary artery, LCA: Left coronary artery
A detailed description of recent advances in the management of CCTGA is beyond the scope of this chapter. CCTGA with suboptimal anatomy is not suitable for biventricular repair. There is renewed interest in 1.5 ventricular repair and Fontan palliation over the last decade. We propose employing a quick algorithm by the echocardiographer for decision-making [Figure 21].
Figure 21: A quick echocardiographer's algorithm aiding decision making in CCTGA. CCTGA: Congenitally corrected transposition of great arteries
Why Do We Need To Correct Congenitally Corrected Transposition of Great Arteries?
Published studies show high association of heart block, TR progression, arrhythmias, CHF and increasing mortality during natural history and consequences of unoperated CCTGA as depicted in [Figure 22].[Table 5] summarizes the timings of intervention in patients with CCTGA.
Figure 22: Natural history of uncorrected corrected transposition. AV: Atrioventricular, TR: Tricuspid regurgitation, CHF: Congestive heart failure
Philosophy of surgical management of congenitally corrected transposition of great arteries
There are two definitive biventricular surgical corrections in CCTGA. They are respectively “physiological correction” and “anatomical repair.” Both focus on maintaining biventricular anatomy, in-series circulation, and septation of heart. [Table 6] compares surgical outcome in patients with CCTGA operated (anatomical vs. physiological correction).
Table 6: Comparison of survival rates: Physiological vs anatomical repair
The early surgical strategies focused on correcting only the associated malformations (ASD, VSD, and PDA), relief of LVOT obstruction, arch anomaly, pacemaker implantation etc.). Consequently, the morphological RV continued as subsystemic ventricle. Predictably, the poorly equipped RV failed in this role and systemic ventricular failure and worsening TR limited the quality and longevity of the individuals. The overall 10-year survival was only 60%.
Post-operative echocardiography should define presence and significance of residual shunt, reduction in quantum of TR [Figure 23], profilation of conduit, Doppler gradients, ventricular function, and pericardial collection should be clearly defined. Special emphasis is on quantification of RV function and detrimental effect of worsening TR.
Figure 23: Echocardiographic assessment of physiological repair of CCTGA. Here, the 9-month-old infant presented with medically refractory CHF due to TR. (a) Preoperative echo color Doppler in apical four-chamber view showing severe morphological TR. (b) RV focused view showing morphological TV repair with arrow pointing to TV annuloplasty ring. CCTGA: Congenitally corrected transposition of great arteries, TR: Tricuspid regurgitation, TV: Tricuspid valve, CHF: Congestive heart failure
This was first conceived by Ilbawi in 1987 and the mainstay is “re-recruiting the morphological LV as systemic ventricle and employing the mitral valve as systemic AV valve.” It is actually a constellation of complex surgeries aimed to maintain blood flow through normal sequence of anatomical structures performed simultaneously. This is typically called as “double switch operation/DSO” [Figure 24].,
Figure 24: A schematic diagram depicting the principle of double switch operation (atrial + arterial switch). *Indicates coronary button transfer. RA: Right atrium, RV: Right ventricle, LV: Left ventricle, LA: Left atrium, PA: Pulmonary artery
Anatomical repair includes a complex of surgery including atrial switch operation, arterial switch operation, and correction of associated defect if any.
Postoperative echo for double switch operation
Unobstructed flow through systemic and pulmonary venous baffles, exclusion of baffle leaks [Figure 25]a and [Figure 25]b, competency, and regurgitation of AV valves.
Figure 25: Postoperative echocardiogram with simultaneous two dimensional (a) and color Doppler (b) interrogating success of DSO focusing on the Senning's component. Mildly mosaic flow (star) was noted in PVB but peak/mean PG = 3/1 mm Hg (within physiological limits). LV: Left ventricle, RV: Right ventricle, PVB: Pulmonary venous baffle, SVB: Systemic venous baffle, AV: Aortic valve, DSO: Double switch operation
Unobstructed flow through neo-Ao and neo-PA, presence and severity of neo-AR, neo-PR, neo-aortic root dilatation, ventricular function (global and regional wall motion abnormalities), flow in reimplanted coronary arteries, presence and severity of main PA to branch PA anastomotic site obstruction [Figure 26]a and [Figure 26]b, pericardial collections, vegetation, and heart block.
Figure 26: Simultaneous two dimensional (a) and color Doppler (b) transthoracic echo assessing the competency of arterial switch. Please take Doppler gradients at each cardiac valves and also MPA-RPA and MPA-LPA anastomotic sites. The above echocardiogram shows translocation of pulmonary arteries and is called “Lecompte Procedure.” Current surgical concepts advocate Lecompte procedure only if great vessels are initially oriented in antero-posterior relationship. RPA: Right pulmonary artery, LPA: Left pulmonary artery, MPA: Main pulmonary artery
Anatomical repair with Senning + Rastelli combination
Apart from assessing atrial switch, special focus of echo on the development of conduit stenosis [Figure 27]a and [Figure 27]b, its progression, kinking, pulmonary valve leakage, susceptibility to staphylococcal and fungal infective endocarditis, thrombus formation inside RV to PA conduit, and assessment of intracardiac tunnel and residual VSD.
Figure 27: (a) Intraoperative photograph showing suturing of RV to PA homograft as part of Rastelli surgery in CCTGA with nonresectable PS. (b) Two-dimensional echo view of the homograft showing absence of kinking, thrombus, or vegetation. CCTGA: Congenitally corrected transposition of great arteries, PS: Pulmonary stenosis, RV: Right ventricle, PA: Pulmonary artery
Tissue Doppler curves of Tei Index, S' velocity, isovolumic acceleration time, and three-dimensional echo for volumes and EF
Assessment of LV dP/dT, “linear relationship”
Advanced echo for LV dysfunction: Mean EF and mean global and lateral wall strain [Figure 30]
Assessment of LV mass (g/m2), LV volume (EDV and ESV), mass/volume ratio (g/ml), and LV posterior wall thickness [Figure 31]a and [Figure 31]b
Echo and cardiac MR are combined to assess LV growth, straightening of LV long axis with associated concentric contractility and septal shift towards RV with documented reduction of RV and tricuspid valve annular diameter
Hraska et al. proposed creation of additional ASD (at least 1 cm in dimension) during PA banding to increase the LV preload.,
Figure 28: Parasternal short-axis view of ventricles post 14 months of PA band for retraining LV showing septal shift and gradual appearance of re-dominance of LV. LV: Left ventricle, PA: Pulmonary artery
Figure 30: Concentric LV contraction after extended LV training by PA band for CCTA. Three-dimensional echocardiographic evaluation of the volumes and contraction pattern of the trained LV As a result of the training, a concentric contraction of all LV segments was observed. Reprinted courtesy Hraska et al. EDV: End-diastolic volume, ESV: End-systolic volume, EF: Ejection fraction, SV: Stroke volume, LV: Left ventricle
Figure 31: Two-dimensional subcostal echo color Doppler views post 14 months of PA banding for LV retraining showing septal shift, growth of LV, measurement of LV area and volume, PA band gradient in a 3-year-old child. This can be used in resource-limited settings in pediatric cohort. PA: Pulmonary artery, LV: Left ventricle
The paradox of some CCTGA hearts is that they behave hemodynamically as univentricular physiology. The causes can be multiple and both anatomical and physiological. Therefore, the clinician often faces the dilemma of offering “Fontan Palliation” in potentially biventricular anatomy. These patients require staged surgery.,
Predicting Congenitally Corrected Transposition of Great Arteries Antepartum by Fetal ECHO
Fetal echocardiogram, between 16 and 20 weeks of gestation, is an important modality to diagnose CCTGA, counsel the family, discuss treatment options, and coordinating delivery at a higher cardiac center [Figure 32]a and [Figure 32]b.
Figure 32: Fetal echocardiograms at 16 weeks depicting CCTGA. (a) Four-chamber view showing double discordance and arrow pointing to large VSD. (b) Outflow views showing parallel great vessels from discordant ventricles. CCTGA: Congenitally corrected transposition of great arteries, VSD: Ventricular septal defect, RA: Right atrium, RV: Right ventricle, LV: Left ventricle, LA: Left atrium
CCTGA is a unique cardiac anomaly , although described more than a century ago, is difficult to diagnose unless strict protocol of segmental analysis is followed. Associated malformations and abnormal cardiac position are anticipated foes. Multimodality imaging starts with echocardiography to analyze and customize treatment for each individual CCTGA heart. Surgical protocols are evolving with time, each bringing its new questions and challenges. Fetal diagnosis has made it possible to alert the parents and medical team to prepare beforehand. The “forgotten ventricle,” i.e., RV, is the key determinant for survival, success of therapy, and quality of life. Advanced imaging technology is offering new insights to this cryptic malady and the final answer is not yet discovered. It offers scope of further research to every student of cardiology and echocardiography.
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