Prenatal Delineation of Coronary Anatomy in Dextro-Transposition of Great Arteries.

BACKGROUND: Dextro-transposition of the great arteries (D-TGA) is the second-most common cyanotic congenital heart disease with variable coronary artery anatomy. The arterial switch procedure has revolutionized outcomes for this defect, with coronary anatomy being a key determinant of both short- and long-term outcomes following surgical repair. The assessment of coronary anatomy is usually undertaken in the postnatal period by transthoracic echocardiography, with assessment prenatally not being well studied. We sought to assess the feasibility of delineating the coronary arteries on fetal echocardiograms in a small cohort of patients followed prenatally.
METHODS: This was a retrospective review of fetuses with D-TGA from 2008 to 2018. Patients with prenatal diagnosis of D-TGA were reviewed for the assessment of coronary artery anatomy. Details of coronary artery anatomy diagnosed prenatally were compared with postnatal transthoracic echocardiograms and intraoperative findings.
RESULTS: Thirty-four fetuses with findings of D-TGA on prenatal echocardiograms were reviewed. 14/34 fetuses had attempted delineation of coronary artery anatomy, with average gestational age of 28 weeks (range 23-31 weeks) at the time of diagnosis. Two-dimensional and color Doppler imaging of the coronary arteries on both short and long axis images were performed, with complete delineation being possible in ~ 86% of fetuses. These findings were confirmed postnatally.
CONCLUSIONS: Fetuses with D-TGA can have variable coronary artery anatomy which drives postnatal outcomes. Our study describes a cohort of patients with D-TGA wherein coronary artery anatomy was assessed. We demonstrate that coronary artery evaluation is feasible prenatally with optimal imaging techniques, being more successful after 25 weeks' gestation. The potential knowledge of dangerous variants can help with referral to centers of excellence for appropriate postnatal management and facilitate prenatal care accordingly. Copyright:

INTRODUCTION

The prevalence of major congenital heart disease at birth is close to 1%.[123] Dextro-transposition of the great arteries (D-TGA) is the second-most common cyanotic congenital heart defect, accounting for 5% of all congenital heart defects.[4] D-TGA has a prevalence of 20–30 per 100,000 live births, with a 2:1 male predominance (particularly large for gestation, term males).[4] In D-TGA, the aorta arises from the right ventricle with the pulmonary artery arising from the left ventricle resulting in ventriculoarterial discordance and parallel circulations. Despite advances in fetal echocardiography, the prenatal diagnosis of D-TGA remains low in various series.[5] Arterial switch operation (ASO) has become the preferred technique for anatomic correction of D-TGA, offering the advantage of a systemic left ventricle over the Mustard/Senning (atrial switch) procedure which results in a systemic right ventricle. Delineation of coronary artery anatomy in D-TGA is essential prior to surgical planning for the arterial switch procedure since certain types of coronary anatomy necessitates a modification of the surgical transfer technique. We sought to review our preliminary experience with the prenatal definition of coronary artery anatomy in a cohort of fetuses with D-TGA confirmed on postnatal transthoracic echocardiogram and intraoperatively.

METHODS

A retrospective review of fetal echocardiograms with prenatal diagnosis of D-TGA at Akron Children's Hospital over a 10 year period from 2008 to 2018 was performed, with the study being approved by the Institutional Review Board. Studies were identified from review of fetal echocardiographic database and chart review. Fetuses with a prenatal diagnosis of D-TGA with echocardiographic images available for review and who had prenatal care and postnatal follow-up were included in the study. Demographic variables, including maternal age, and gestational age (GA) at diagnosis were recorded. Fetal echocardiographic parameters including presence/absence of ventricular septal defect (VSD) and GA at the delineation of coronary artery anatomy were recorded. Postnatal echocardiogram with regards to coronary artery anatomy, as well as surgical confirmation of coronary artery anatomy (at the time of ASO) was recorded.

Echocardiography methods

Fetal echocardiograms were performed using a Siemens S 3000 machine using the 8 MHz curved array transducer with harmonic imaging and Phillips EPIQ machine using the 9 MH curved array transducer. Both two-dimensional (2D) as well as Color Doppler Imaging were utilized for the assessment of cardiac anatomy, including coronary artery anatomy. Coronary artery anatomy was assessed on both short axis and long axis imaging. Color Doppler velocity scale was adjusted between 30 and 45 cm/s to image flow through the coronary arteries; the frame rates for the study ranged between 30 and 45 Hz. The echocardiographic images were individually reviewed to assess for the documentation and confirmation of the coronary artery patterns.

RESULTS

A total of 34 fetuses were diagnosed prenatally with D-TGA over the 10-year period of the study; 14/34 fetuses had attempted delineation of the coronary artery anatomy [Table 1]. The average age of mothers was 28 years (range 19–41 years). Average GA at diagnosis was 28 weeks (range 23–31 weeks). Seventy-nine percent of patients had delineation of coronary artery anatomy at or more than 25 weeks GA. Eighty-six percent of fetuses had intact ventricular septum and 14% had an associated VSD. Complete delineation of the coronary artery anatomy could be done prenatally in 79% (11/14 fetuses), with variant anatomy in 2 fetuses. Sixty-four percent (9/14) of fetuses had usual coronary anatomy for D-TGA [Figures 1 and 2]. The right coronary system could not be well delineated in 36% of the cohort (3/14). Fourteen percent (2/14) of the fetuses had a circumflex coronary artery arising from the right coronary artery [Figure 3]. A coronary artery arising from the right coronary cusp and traversing in the left atrioventricular (AV) groove was a potential marker for anomalous origin of the circumflex from the right coronary artery. Coronary anatomy as well as the cardiac anatomy diagnosed prenatally was confirmed postnatally on the transthoracic echocardiograms and intraoperatively during the arterial switch procedure. Of the 23 fetuses wherein delineation of coronary artery anatomy was not fully feasible prenatally, one baby had single coronary artery from right sinus, two had circumflex coronary arising from right coronary artery and the remaining 20 fetuses had usual coronary anatomy for D-TGA.

Table 1

Demographic characteristics

Number	Maternal age (years)	GA at diagnosis (weeks)	Cardiac diagnosis	Coronary pattern
1	22	26	D-TGA/IVS	LCA system seen
2	22	24	D-TGA/IVS	LCA system seen
3	19	30	D-TGA/IVS	Usual coronary pattern
4	34	28	D-TGA/IVS	Usual coronary pattern
5	20	32	D-TGA/VSD	Usual coronary pattern
6	29	23	D-TGA/IVS	LCA system seen
7	20	34	D-TGA/VSD	Usual coronary pattern
8	26	27	D-TGA/IVS	Usual coronary pattern
9	41	30	D-TGA/IVS	Circumflex from RCA
10	33	25	D-TGA/IVS	Circumflex from RCA
11	36	24	D-TGA/IVS	Usual coronary pattern
12	20	31	D-TGA/IVS	Usual coronary pattern
13	39	29	D-TGA/IVS	Usual coronary pattern
14	28	31	D-TGA/IVS	Usual coronary pattern

D-TGA=Dextro-transposition of the great arteries, IVS=Intact ventricular septum, VSD=Ventricular septal defect, LCA=Left coronary artery, RCA=Right coronary artery, GA=Gestational age

Figure 1

Color Doppler image showing usual coronary pattern: The left coronary artery arises from the left posterior facing sinus and bifurcates into the left anterior descending and left circumflex coronary arteries and right coronary artery arises from the right posterior facing sinus, coursing in the right atrioventricular groove

Figure 2

Color Doppler image showing usual coronary pattern: The aorta is the anterior vessel. The left coronary artery arises from the left posterior facing sinus and bifurcates into the left anterior descending and left circumflex coronary arteries and right coronary artery arises from the right posterior facing sinus, coursing in the right atrioventricular groove

Figure 3

Two-dimensional images: Anomalous origin of the circumflex coronary artery from the right facing sinus and coursing toward the left atrioventricular groove in short axis and four-chamber views

DISCUSSION

Anomalies of coronary arteries occur in both the origin and distribution, with further anomalies secondary to intramural course in D-TGA.[6] The identification of coronary artery anatomy is crucial in the preoperative assessment and surgical management of these patients. The presence of a single coronary artery, anomalous circumflex coronary artery, or intramural course may necessitate alteration of the surgical technique of the arterial switch procedure.[7] The presence of a VSD or side-by-side great vessels should alert the cardiologist to an increased likelihood of coronary anomalies. The most common coronary pattern in D-TGA is the usual pattern, in approximately 66% of patients, with the coronary arteries arising from their appropriate sinuses and branching normally, a pattern most often seen with the aorta anterior and to the right of the pulmonary artery.[8] The coronary arteries usually take the shortest course to reach their distribution, and because the aorta is anterior, the left main and circumflex coronary arteries pass anterior and leftward to the right ventricular outflow tract. This usual pattern of coronary arteries was found in the majority of our cohort as well (86%). The next most common variant is origin of the left circumflex coronary artery from the right coronary artery and coursing posterior to the pulmonary artery, which is seen in about 16% of patients, usually with side-by-side great vessels.[8] This was similar to our study wherein 14% of the fetuses had this finding. Less common variants include inverted coronaries, (right coronary artery arising from left anterior sinus and left coronary artery arising from right posterior sinus), single coronary artery, intramural and inter-arterial course which were not found in our study, given the small sample size and associated rarity.

ASO has become the procedure of choice for surgical repair of D-TGA.[9101112] Compared with atrial-level Mustard and Senning repairs, correction at the arterial level restores the left ventricle as the systemic pumping chamber with improved long-term outcomes.[131415] Accurate identification of coronary artery anatomy is extremely important for the success of the ASO, therefore much attention has been paid to the relationship between the coronary pattern and outcome.[6816] Advances in prenatal ultrasound screening have facilitated assessment of small structures such as the coronary arteries antenatally.[5] Although some cases of D-TGA are missed during the prenatal period, the newer AIUM guidelines to assess the outflow tracts on prenatal ultrasound will result in improved detection rates.

Despite the improved prenatal diagnosis, an accurate and more complete assessment of the cardiac anatomy is done after birth at which time the coronary artery anatomy is assessed as well. Our study demonstrates that careful attention to imaging techniques allows for the possibility of evaluating the coronary artery anatomy prenatally, ideally at or after 25 weeks' gestation when the fetus is bigger. However, we acknowledge that various factors such as fetal position, GA, and maternal body habitus as well as multiple gestation could influence the successful assessment of both the cardiac and coronary artery anatomy. In our study, we were able to assess coronary artery anatomy in 41% of patients, with improved chances of success after 25 weeks' gestation.

Prenatal coronary artery assessment has the potential for multiple benefits since ASO has increasingly been performed sooner after birth.[17181920] It aids in planning postnatal course and counseling parents about potential variations in surgical technique in the presence of abnormal anatomy. Patients can be referred to surgical centers of excellence for more complex variants to ensure successful outcomes as needed. A study by Kaji et al. reported three cases of prenatal identification confirmed by angiography at the time of balloon atrial septostomy postnatally.[21] Our study describes a fairly large cohort of patients with prenatally described coronary anatomy by both 2D and Color Doppler imaging. As per the previous paper, we found that the assessment of the semilunar valves in the short axis as well as in the long axis, after 25 weeks gestation, enables prenatal delineation, as the fetus is bigger allowing better visualization of cardiac anatomy. In addition, fetal echocardiography provides unique angles of interrogation through the collapsed lungs which is a potential advantage compared to the prominent lung artifact causing limited acoustic windows on postnatal imaging.

A coronary artery arising from the right sinus and coursing toward the left AV groove can raise suspicion for anomalous origin of the circumflex coronary artery. The two patients in our study who had anomalous origin of the circumflex coronary artery were confirmed with postnatal imaging and intraoperatively, with the surgeon appropriately modifying surgical technique for coronary transfer. The study by Pasquali et al.[22] combined the results of nine case series in a meta-analysis to estimate the effect of coronary anatomy on mortality after ASO, both overall and adjusted for time. They concluded that common coronary variants have undergone ASO without added mortality compared to those with the usual coronary pattern. However, those with intramural or single coronary arteries have significant added mortality that has persisted over time.

CONCLUSIONS

We report a large series of patients with D-TGA diagnosed prenatally in whom successful assessment of coronary artery anatomy was made possible with the help of gray-scale and color Doppler imaging. This has prognostic significance and allows for appropriate prenatal counseling and surgical planning. We anticipate that detection rates will only continually improve with newer advances in technology.

Ethical clearance

The study was conducted according to the guidelines of the Declaration of Helsinki. This was a retrospective study of variables collected during routine clinical practice and need for informed consent was waived.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.