Patent ductus arteriosus stenting as therapeutic bridge in a patient with type A3 truncus arteriosus variant with multiple comorbidities

Abstract

Type A3 truncus arteriosus describes pulmonary atresia with non-confluent mediastinal pulmonary arteries in which one pulmonary artery arises from a patent ductus arteriosus and the contralateral pulmonary artery from the aorta resulting in ductal dependent pulmonary blood flow. We describe a premature neonate with caudal regression syndrome and type A3 truncus arteriosus who was palliated with a ductal stent allowing completion of a prolonged neonatal ICU hospitalisation for multiple comorbidities.

Truncus arteriosus is a form of CHD classified by the presence of a common aorticopulmonary trunk. There are two anatomic classification systems, Van Praagh and Collett and Edwards, that categorise variations of pulmonary artery architecture. Accurate anatomic delineation is paramount for management, as in our patient that will be discussed. Our patient represents a unique variation of pulmonary artery branching most consistent with Van Praagh type A3, with single pulmonary artery atresia and presence of a patent ductus arteriosus or collateral supply to the ipsilateral lung. ¹ Typically, truncus arteriosus is surgically repaired by unifocalisation of the branch pulmonary arteries and placement of a right ventricle to pulmonary artery conduit, as well as closure of the ventricular septal defect. The complexity and inherent risk in this multi-step repair is an important consideration when evaluating patients with other comorbidities. Staged repair may be more feasible in medically complex patients. We utilised multimodality imaging techniques including echocardiography, computed tomography angiography (CTA), and cardiac catheterisation to determine the cardiac anatomy and then proceeded with palliative ductal stent placement to provide hemodynamic stability and allow for management of other comorbidities.

Case

Our patient was born at 35 weeks and 5 days gestation via scheduled caesarean section due to maternal history of multiple prior caesarean sections and fetus at high risk for critical airway. Pregnancy was complicated by maternal type II diabetes mellitus requiring insulin, polyhydramnios, and multiple fetal congenital anomalies including severe micrognathia, sacral agenesis, bilateral absent lower extremity bones, single umbilical artery, and suspected cardiac anomaly. A technically difficult fetal echocardiogram performed at 21 weeks gestation raised concern for a ventricular septal defect (VSD).

The patient underwent planned intranasal intubation via ex-utero intrapartum treatment procedure due to severe micrognathia. Birth weight was 1881 g, and APGARs were 2, 5, and 6 at 1, 5, and 10 minutes, respectively. Following resuscitation and ventilator optimization, the patient’s oxygen saturations were 80–85% on minimal supplemental oxygen.

The initial postnatal echocardiogram demonstrated a conotruncal VSD with over-riding aorta and absent pulmonary outflow tract. A left pulmonary artery was demonstrated arising from the underside of the aortic arch and no right pulmonary artery or patent ductus arteriosus was visualised. Given the uncertainty regarding pulmonary artery anatomy, prostaglandin E1 infusion was initiated. CTA was initially deferred to avoid iatrogenic kidney injury in the setting of a hypoplastic left kidney with cortical cysts and hydronephrosis. A subsequent echocardiogram on prostaglandin E1 demonstrated a now present right pulmonary artery that appeared to arise from a right-sided patent ductus arteriosus originating from the aorta.

At 1 week, a CTA confirmed that the left pulmonary artery arose from the underside of the aortic arch (Fig. 1b) and the right pulmonary artery from a right patent ductus arteriosus originating from the aorta at the base of the right innominate artery (Fig. 1a). The anatomy was most consistent with Van Praagh type A3 truncus arteriosus, with ductal-dependent pulmonary blood flow physiology. The exact location of the patent ductus arteriosus to right pulmonary artery transition was not clearly visible on the CTA in the setting of prostaglandin E1 infusion.

The patient was discussed in our weekly multidisciplinary case conference to develop a management plan. The consensus was to proceed with cardiac catheterisation and ductal stent placement to establish stable pulmonary blood flow, avoid potential morbidity associated with neonatal cardiac surgery, and allow the opportunity to address her additional serious comorbidities.

Cardiac catheterisation was performed at 4 weeks of age, at which point the patient weighed 2.8 kg. Prostaglandin E1 was discontinued 6 hours prior to the procedure to allow ductal constriction for stability of stent placement. Vascular access was achieved via the left axillary artery with a 4 Fr sheath. An initial angiogram via the axillary artery sheath in the ascending aorta demonstrated the left pulmonary artery arising from the underside of the transverse aortic arch. The left pulmonary artery, proximal to the origin of the left upper lobe branch, measured 3.5 mm in diameter. A subsequent angiogram performed through a 4Fr non-taped angled glide catheter in the patent ductus arteriosus demonstrated the discrete stenosis at the transition from patent ductus arteriosus to right pulmonary artery, proximal to the origin of the right upper lobe branch (Fig. 1c). The proximal end of the patent ductus arteriosus measured 3.4 mm while the right pulmonary artery just distal to the patent ductus arteriosus to right pulmonary artery transition measured 3.1 mm. The patent ductus arteriosus and right pulmonary artery were then stented to 3.5 mm diameter with two telescoped Medtronic Onyx Frontier Drug Eluting Stents. Post-stent angiography demonstrated complete ductal coverage and unobstructed flow to all segments of the right lung (Fig. 1d). A transthoracic echocardiogram was performed that demonstrated appropriate stent flow and absence of obstruction to flow in the aorta and innominate artery. The procedure was complicated by left axillary artery thrombus, which resolved following heparin infusion.

Serial echocardiograms were performed and demonstrated continued patency of the patent ductus arteriosus to right pulmonary artery. The patient received dual anti-platelet therapy to maintain stent patency. She was also initiated on once daily lasix for management of pulmonary oedema following stent placement. The patient subsequently completed a 4-month hospital course including tracheostomy surgery with home ventilator transition, gastrostomy tube placement, opioid dependence wean, seizure management in the setting of known cerebral atrophy and diffusely prominent subarachnoid spaces, pyloromyotomy for pyloric stenosis, investigation of congenital cyst of left kidney, and multiple sepsis evaluations.

The patient maintained oxygen saturations in the mid 80% range and demonstrated adequate growth prior to discharge. She was discharged home with outpatient follow-up and at 5 months of age is being considered for right ventricle to pulmonary artery conduit placement with unifocalisation of her discontinuous mediastinal branch pulmonary arteries.

Discussion

In a review of the original characterisation of truncus arteriosus, the Van Praagh discussed the lack of “true” truncus arteriosus in how it is defined by its embryologic origin of failure of septation of the conotruncus. They propose the similarity of truncus arteriosus with Tetralogy of Fallot with pulmonary atresia and ventricular septal defect in having the absence of distal pulmonary infundibulum. ¹ Our patient’s unique anatomy encompassed the rare but observed variations that make classifying these lesions difficult. Ultimately, CTA demonstrated the atypical origins of her pulmonary arteries, suggesting Van Praagh type A3 qualities given the ductal-dependent right pulmonary artery consistent with the clinical development of severe cyanosis responsive to prostaglandin E1 infusion with reopening of a distal right pulmonary artery visible by echocardiography. Thus, multimodality imaging characterised the rare cardiac lesion and provided a three-dimensional roadmap for catheter-based ductal stent placement. This therapeutic pathway was preferred due to the patient’s multiple comorbidities. Thus, our patient highlights how a commonly used catheter-based bridge to surgical correction or palliation of CHD can be especially helpful in complex patients requiring other neonatal procedures.

Other similar cases have been reported following a staged repair with ductal stent placement. Kawasaki ² and Ganta ³ both describe cases of rare Van Praagh type A3 truncus variations which utilised this palliative step to somatic and pulmonary artery growth to improve the outcomes of later surgical intervention. However, for our patient, the stent placement to preserve ductal dependent right pulmonary artery flow served as an extended palliative step while addressing serious non-cardiac comorbidities which has improved the likelihood of successful cardiac surgical repair.

While our patient had mild heart failure symptoms following patent ductus arteriosus/right pulmonary artery stent placement, it has been easily managed medically with low dose diuretic therapy. She has had adequate somatic growth velocity, and her persistent respiratory support requirements are attributable to her structural airway abnormalities. We recognise that her current cardiac palliation confers the risk of development of pulmonary arterial hypertension; however, the risks associated with a complex cardiac surgery in the setting of serious comorbidities may be equally deleterious. She will continue to receive a multidisciplinary approach to her care, and the nature and timing of subsequent cardiac interventions will be determined based on her overall clinical condition.

Figure 1. ( a ) 3D reconstruction of CTA demonstrating the PDA arising from the aortic arch at base of right innominate artery and supplying the RPA. ( b ) LPA arises from the underside of the aortic arch with mild proximal narrowing. ( c ) Fluoroscopic angiography of the right sided ductus arteriosus after discontinuation of PGE1 infusion. Access achieved via left axillary artery due to caudal regression syndrome with absent lower extremities. ( d ) Status post placement of two 3.5 mm diameter telescoped Medtronic Onyx Frontier Drug Eluting stents to cover the ductus arteriosus with complete ductal coverage and unobstructed flow to right lung.