Common arterial trunk with interruption of the aortic arch; a rare association of complex anomalies. Case report

Introduction

Common arterial trunk (truncus arteriosus communis – TAC) has been described as a rare conotruncal anomaly characterised by a single arterial trunk that leaves the heart through a single arterial valve, giving rise directly to the coronary arteries, aorta, and one or two pulmonary arteries [1]. Generally, this pathology occurs in the context of atrial disease, with concordant atrioventricular connections and ventricular septal defect, its variability depends on the branching pattern of the arteries, and it generally presents associated with microdeletion 22q11.2 [2].
Despite the common origin between the aorta and the pulmonary artery, a failure in the separation process causes the persistent common trunk with a single valve with 4 or more leaflets, which may be stenotic or insufficient [1] as a result of a dysfunction in neural crest cells with failure in their migration, generally associated with variants in the TBX1, CRKL, and ERK2 genes [2].
This heart disease was first described in 1789 by Wilson. In 1949 Collet and Edwards proposed the first classification (based on the origin of the pulmonary arteries), and in 1965 Van Praagh suggested an alternative classification taking into account the presence or not of ventricular septal defect and the interruption or not of the aortic arch [3].
Epidemiologically, TAC is found in approximately 1-4% of children with congenital heart disease, occurring in between 9 to 11 per 100,000 births [2]. Its aetiology is multifactorial; it can occur as an isolated defect or associated with the microdeletion of chromosome 22q11.2 where its prevalence is around 35 to 40%. A mortality rate of less than 10% has been reported in full-term newborns without interruption of the aortic arch who undergo surgical repair; however, this mortality can reach up to 30% in those with aortic arch obstruction and anomaly of the trunk valve, especially when accompanied by a birth weight less than 2500 g [3]; in those who are not treated it rises to 65% in the following 6 months and up to 75% one year after birth [4, 5]. Other studies report, in the Kaplan Meier curves, a decrease in survival of around 30% without intervention [6].
Prenatal diagnosis of congenital heart diseases has a wide variety of benefits, including the reduction of neonatal morbidity and mortality, promoting the opportunity for an elective, controlled birth in a specialised institution, with a timely cardiac surgery program [7, 8]. For patients with CT, the most important objective is the recognition of differential diagnoses, due to its difficult identification in prenatal life, acting as a confusion factor with other congenital heart diseases [9].

Case report

In a 21-year-old patient, G2A1P0, with no significant personal or family history, during the ultrasound evaluation at 22 weeks of gestational age, a 3.2 mm perimembranous interventricular septal defect was evident, with atrio-ventricular concordance and aorto-pulmonary altered relationship. A left outflow tract was evident, which reached the supra-aortic trunks, but its continuity towards the descending aorta was not visualised. In 3 vessels and trachea section, the aortic isthmus could not be visualised, suggestive of interruption of the aortic arch. An echocardiogram was performed at 27.6 weeks, in which the outflow tracts of the ventricles were not visualised independently, giving the appearance of a common arterial trunk, associated with interruption of the aortic arch, and it was considered type A4 in the VAN PRAAGH classification (Figure 1). Within the prenatal studies, a normal fetal neurosonography was found, and no genetic study was performed if it was not authorised by the patient.
The infant was born at 38 weeks, in a IV level institution, caesarean section for stationary delivery, female weighing 3746 g, Apgar 8-9-9, no palatal defects, and facial dysmorphism; echocardiogram that confirmed the diagnosis. She received prostaglandin E1 (Alprostadil) to ensure ductal patency and systemic flow. Complementary tests such as transfontanellar and abdominal ultrasound were performed with normal results. Angiotomography reported common arterial trunk (Collet and Edwards type II/Van Praagh type A2), bileaflet truncus valve, interruption of the aortic arch type B with stenosis of the ostium of the left subclavian artery, patent ductus arteriosus type C, and a 2 × 4 mm subarterial ventricular septal defect (Figure 2). Upon confirmation of the diagnosis, she underwent correction of the interruption of the aortic arch, atrial septectomy, and cerclage of the pulmonary arteries with the following surgical findings: common arterial trunk, where the ascending aorta leaves the pulmonary trunk and the pulmonary branches come out at a different level; interruption of the type B aortic arch is seen. Subsequently, she presented severe right ventricular dysfunction, moderate left ventricular dysfunction, and severe oxygenation disorder, which is why she was left on ECMO support, in addition to renal replacement therapy.
After multiple failed attempts to withdraw from ECMO, on the seventh day a new attempt was made, with a drop in pressure that did not improve with pharmacological support and desaturation. Due to multiple organ failure, it was decided to suspend ECMO therapy, and the patient died.

Discussion

Prenatal diagnosis of congenital heart diseases has multiple benefits, including a reduction in neonatal morbidity and mortality, by having the opportunity for an elective controlled birth in a specialised institution with an established cardiac surgery program [7]. In addition, it allows decisions to be made regarding the continuation of pregnancy, treatment options, and the evaluation of other fetal anomalies.
Multiple studies have demonstrated the difficulty in distinguishing different conotruncal alterations during fetal life, with a potential confusion factor between arterial trunk and pulmonary atresia with associated septal defect [9], the combination between the truncus arteriosus and the interruption of the aortic arch being an even more difficult alteration to find, reporting to date the largest series of cases of 50 patients by the society of congenital heart disease surgeons [10]. Hence the importance of serial echocardiographic evaluation being in expert hands.
Making the diagnosis requires a systematic review based on the identification of the cardiac orthogonal planes, the definition of the situs and the verification of the structures and their connections, allowing the risk profile of patients who require echocardiography [11]. Adding spatiotemporal correlation to the diagnostic method, plus tomographic ultrasound images, usually increases the diagnostic performance in the detection of major congenital heart diseases; However, Turan et al. reported in their study that the detection rate of common arterial trunk and interruption of the aortic arch continues to be a challenge due to its low incidence, but they were able to determine that once identified, no additional anomalies were found nor new diagnoses in subsequent follow-ups [11].
Once the diagnosis is made, this pathology has traditionally been classified (CT) according to the system proposed by Collet and Edwards as type I if it has a partially formed pulmonary aortic septum and, therefore, the trunk of the pulmonary artery is present. In type II, the left and right branches arise directly from the posterior surface of the common arterial trunk, adjacent to each other. In type III, both pulmonary branches arise on each side of the common arterial trunk and finally in type IV, the pulmonary branches do not arise from the common arterial trunk, but as aortopulmonary collaterals [2]. Subsequently, and due to the impact on mortality, Van Praagh considered the presence of ventricular septal defect and interruption of the aortic arch in his classification. Here the letter A or B is taken into account depending on whether there is interventricular communication or not and the number 1 if there is a pulmonary trunk, 2 if it does not exist but the branches arise directly from the common trunk regardless of their proximity, 3 if the origin of one of the branches are not from the common arterial trunk, but from an aortic collateral duct, and 4 when the aortic arch is interrupted and there is a large duct that feeds the descending aorta, as presented in our case [3].
Since 1986, a worse prognosis has been described in patients with interruption of the aortic arch [12], with mortality rates of 76% at birth without surgical intervention and 90% in the first year of life, having a life expectancy of 4 to 10 days, with a positive impact when early management with prostaglandins associated with surgical intervention is performed [12].
Early mortality has been described between 47 and 50% when this association occurs, in patients who underwent surgery in a single surgical procedure, considering that it is a procedure that involves repair of the aortic arch as the most important step, reconstruction of the outflow tract of the right/left ventricle, and truncal valve repair [10, 13].
In 2005 McCrindle et al. reported an average of 11 days to die if complete surgical procedures are not performed. Among the causes of death were heart failure, prematurity, low weight, and the need for dopamine infusion. For patients who underwent arch obstruction repair, a 16-year survival rate of 29% was found [13].
Naimo et al. in their survival study in 2020 found a mortality rate of 17% after surgical correction, with a mean age of death of 21 days, and heart failure without the possibility of withdrawing ECMO was found among the causes of death in 3 of the 4 patients, like the case reported herein, and a mortality of 11% in patients without interruption of the aortic arch. In the analysis of survival, it was found that it was 83% (95% CI: 61-93) at 20 years in patients with interrupted aortic arch, and 74% in patients without interruption of the aortic arch [14].
Cuomo et al. in 2022, reported surgical mortality in neonates with TAC of 14.1%, which rose to 29.8% when associated with a repair of the interruption of the aortic arch [6]. This is similar to the findings reported by Buckley et al. in 2023 when they reported an operative mortality rate of 20% when associated with interruption of the aortic arch, in addition to a greater survival for patients without association of interruption of the aortic arch (80% vs. 38%) (p = 0.044) [15].
Hames et al. in 2021 described the importance of ECMO as a rescue tool in patients with congenital heart disease that progresses to respiratory failure in the postoperative period, including patients who underwent arterial trunk repair; however, patients who require perioperative ECMO around of TAC repair suffer high mortality [16]. Within their study they reported the highest mortality rate in patients with more than 6 days on ECMO support, need for renal replacement therapy, complications such as bleeding, and association with interruption of the aortic arch [16].
Hook et al. in 2023 described as independent predictors of mortality in patients undergoing cardiac surgery for common arterial trunk, heart failure OR = 8.2 (95% CI: 3.67-18.31, p < 0.001), need for ECMO OR = 17.51 (95% CI: 10.56-29.02, p < 0.001), acute kidney injury OR 4.22 (95% CI: 2-64-6.74, p < 0.001), and cardiac catheterisation OR = 3.20 (95% CI: 1.99-5.17, p < 0.001) [17], complications that occurred in our case.
Abel et al. in 2021 reported chromosomal and extra-cardiac anomalies occurring in a significant proportion, with a prevalence of 38.2% and 58.8%, respectively. They described intrauterine fetal death at 21 weeks in 2.9% of fetuses with alobar holoprosencephaly and severe early intrauterine growth restriction in association with TAC. 2.9% died in the neonatal period and 11.8% in early childhood in association with microdeletion 22q11, thymus aplasia, cerebellar hypoplasia, microcephaly, and singular umbilical artery [1].
Finally, it is important to mention the relevance of genetic tests in pathologies that are linked to this type of alterations, because with them it is possible to provide advice during pregnancy to facilitate the process of adaptation to losses (when presented), interpretation of results, and finally decision making regarding treatment in genetic counselling [18].
On the other hand, it allows correct preconception counselling to be able to identify and prevent situations of high risk of heritability for future pregnancies and the implementation of timely interventions [19] – a procedure that could not be performed in the case of our patient.
It can be concluded that the common arterial trunk is a pathology with a high mortality rate attributed when it is associated with interruption of the aortic arch. It should be noted that its diagnosis continues to be a challenge despite advances in technology, and as shown in the present case, despite correct prenatal diagnosis, disparities can be found in echocardiographic, radiological, and surgical anatomical findings. This case shows the natural history of the disease when it is associated with independent mortality factors, despite different medical efforts in its treatment.

Disclosures

Ethical considerations: none.
This research received no external funding.
The authors declare no conflict of interest.

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