A case of aortopulmonary window mimicking common arterial trunk on fetal echocardiography

Introduction

Aortopulmonary window (APW) is a rare congenital cardiac anomaly characterised by abnormal communication between the aorta and the pulmonary trunk in the presence of separately formed semilunar valves. It accounts for approximately 0.1% of all types of congenital heart disease (CHD) and may occur as an isolated anomaly or, more often, concomitantly with other abnormalities such as atrial septal defect, ventricular septal defect, tetralogy of Fallot, and aortic arch anomalies [1-7].
Most patients demonstrate left-to-right shunt; it is also essential to determine the exact location and size of the communication between the main arteries. Most anomaly cases are diagnosed during infancy; however, a prenatal diagnosis was reported and when possible, it constitutes an important role for treatment planning and thus prevention of cardiac failure development [8].

Case report

A 31-year-old pregnant patient (multiparous) was referred to the tertiary centre in Krakow, Poland for a third opinion consultation due to a diagnosed fetal cardiac anomaly and for further postnatal management planning. No complications were observed during pregnancy. The first scan at another reference centre performed at 21 weeks of gestation revealed the common arterial trunk (CAT), suspected right atrial isomerism, an additional left toe, and a two-vessel umbilical cord. The amniotic fluid aCGH test did not detect any fetal genomic imbalance. The next fetal echocardiogram was performed at 23 weeks of gestation in another tertiary institution and revealed CAT type A1. In addition to the ventricular septal defect, the common arterial trunk was described and characterised by a short pulmonary trunk divided into 2 pulmonary branches. The patient decided to request a third opinion at 31 weeks of gestation. Two arterial valves and signs of tetralogy of Fallot (S, D, S) with a right-sided aortic arch and aortopulmonary window type I with wide interatrial communication were observed on this scan (Figures 1 and 2). The diameter of aortopulmonary window was 6.1 mm.
Considering the new findings, the patient received an adequate consultation from the team of perinatologists and cardiologists. The neonate was born at 38 weeks of gestation by caesarean section due to 2 prior caesarean procedures and premature rupture of membranes; its birth weight was 2825 g. The Apgar score after delivery was 7/9/9. As the newborn demonstrated clinical signs of tachypnoea and irregular breaths with intercostal retractions, CPAP non-invasive ventilation was initiated and continued for several hours. In addition to prenatally detected abnormalities, a left pelvic kidney was identified. Further bronchoscopy revealed laryngomalacia, mild retrognathism, and laryngeal hypoplasia. An X-ray exam was performed after birth and showed the cardiac silhouette shifted to the left as well as signs of increased pulmonary flow. The postnatal echocardiogram confirmed the prenatal diagnosis provided by the third opinion: situs solitus; atrio-ventricular (AV) and ventriculo-arterial (VA) alignments; a normal pulmonary venous connection; normal function of atrioventricular valves with a normal inflow pattern; a large atrial septal defect (ASD) of 8 mm with left-to-right shunt; a ventricular septal defect (VSD) of 9 mm with left-to-right shunting with the 16 mmHg gradient; a dextral position of the aorta; left ventricular outflow tract (LVOT) without stenosis; a slightly dysplastic, probably two-cuspid aortic valve with regurgitation grade I/II; an aortic valve (AV) ring 9.1 mm (Z-score 1.84); a right-sided aortic arch; a pulmonary valve ring 5.2 mm (Z-score –3.2) with a minor flow turbulence 1.9 m/s; and an aortopulmonary window of 11 mm (Figure 3).
In functional assessment the shortening fraction (FS) was 30.7%, and the ejection fraction (EF) measured 62.2%. During the preoperative period, enteral feeding was initiated due to poor weight gain. Moreover, signs of cardiovascular failure (tachypnoea, tachycardia) were observed, and treatment was administered (captopril, propranolol, diuretics). Three weeks after birth, the child was scheduled for surgery: complete repair and APW closure using an autologous pericardial patch, excision of trabeculae in the right ventricular outflow tract (RVOT), transannular reconstruction below the RVOT, reconstruction of the RVOT using autologous pericardial patch, and partial ASD closure (Figure 4).
Intraoperatively, the left coronary artery was found to originate high just below the lower edge of the window. The postoperative condition of the child was good. The patient was intubated and mechanically ventilated for 72 hours and stayed in the Intensive Care Unit for 6 days; the postoperative course was uneventful. The pre-discharge echocardiogram findings were as follows: good systolic function of both ventricles, right ventricular hypertrophy, bidirectional shunt through a minor ASD (left intentionally), no residual shunt regarding the ventricles, laminar flow through the atrioventricular valves with no significant regurgitation, laminar flow through the RVOT, minor flow turbulence at the origin of the pulmonary arteries from the pulmonary trunk, significant pulmonary valve regurgitation following transannular correction, laminar flow through the LVOT and AV maximum velocity of 1 m/s; mild aortic regurgitation, slightly dilated ascending aorta 14-15 mm (Z-score +4,5); no flow abnormalities; and absence of shunts. The child was discharged from the hospital weighing 3300 g with 97% saturation.

Discussion

Only isolated cases of APW in association with TOF have been described in the literature [8-14]. Just 40 cases of APW have been detected prenatally, and among them, the combination with TOF was described in only 2 articles (Table 1) [15-34].

Differential diagnosis

The vast majority of APW cases are associated with coarctation of the aorta, hypoplasia of the aortic arch, and sometimes its interruption. The reason for this combination is a significant left-right leak between the great vessels. These cases can be detected at the height of the three-vessel and trachea view. Subsequently, when searching for potential locations of the left-right leak after excluding subaortic VSD, the examiner may encounter APW. In our case, the situation was different. We detected anterior malalignment VSD with aortic dextroposition and hypoplasia of the conus arteriosus with secondary pulmonary stenosis, typical features of TOF. However, additional APW caught our attention. Of course, in cases of earlier pregnancy or more pronounced hypoplasia of the conus arteriosus, such an image may resemble CAT. However, the presence of ductus arteriosus in this situation in the absence of the aortic arch interruption should allow the exclusion of CAT. First of all, the common arterial trunk characterised by the presence of only one semilunar valve should be distinguished from APW because both aortic and pulmonary valves were observed here. The initial diagnosis of the presented case, made during the first and second evaluations, is associated with different management approaches regarding treatment and further prognosis. Moreover, the right-sided aortic arch that results in the shift of the descending aorta to the ipsilateral position with inferior caval vein may cause additional diagnostic difficulties because it may be misinterpreted as a sign of right atrial isomerism. In this case, a precise assessment of morphology of the atria, liver, spleen, and the other abdominal organs was performed, which is particularly important because the right-sided aortic arch and the common arterial trunk are observed in 32% and 10% of cases of right atrial isomerism, respectively [35].

Prognosis

A physical neonatal exam in cases like the one presented in our article frequently reveals systolic or continuous heart murmur, tachypnoea, and signs of cardiac failure. In addition, in the case of decreased coronary perfusion pressure, so-called coronary steal syndrome, may develop, which is more common, when accompanied by tachycardia. Larger shunts lead to pulmonary hypertension. Therefore, it is important to repair the defect during the first months of life so that irreversible damage of the pulmonary vessels can be avoided. It should be remembered that in the case of a combination of significant valvular or infundibular pulmonary stenosis with APW, the leak through the window significantly supports the pulmonary circulation, eliminating the effect of reducing the flow through the pulmonary valve from the right ventricle [36]. For patients with diagnosed APW, surgical closure of the defect or transcatheter placement of an implant is recommended [3, 7, 37].

Conclusions

Aortopulmonary window may remain undiagnosed until adulthood. A late diagnosis may result in congestive heart failure and irreversible damage to the pulmonary vessels. This is why early detection of APW, preferably in the prenatal period, remains the key issue in terms of this condition [33, 38].

Conflict of interest

The authors declare no conflict of interest.

REFERENCES