A case series of three patients with unilateral disconnected pulmonary artery supplied by an ipsilateral patent ductus arteriosus: neonatal ductal stenting as palliation to preserve pulmonary arterial patency.

BACKGROUND: Disconnected branch pulmonary arteries with a systemic arterial origin of the disconnected vessel is a rare, but well-described entity. Most will have ductal tissue connecting the pulmonary artery to the aorta. CASE
SUMMARY: We describe in this paper the haemodynamic result in three neonates presenting with ductal origin of a single branch pulmonary artery in the context of trans-catheter stenting procedures to maintain or re-recruit vessel patency. All were faced with potential or actual ductal closure and proceeded to trans-catheter stenting to re-cannalate the duct-dependent pulmonary artery. Two patients with otherwise normal anatomy struggled post-procedure with pulmonary hypertension and right ventricular dilatation. Both required surgical re-anastomosis of the disconnected pulmonary artery during the same admission-one 26 days post-stenting following failure to wean from high-flow respiratory support and the second 8 days post-stenting following failed extubation. In contrast, a patient with tetralogy of Fallot born at 2.5 kg underwent sequential stenting of the right ventricular outflow tract and then the left-sided ductus. He had a good post-procedural course and thrived for several months before complete repair. DISCUSSION: We describe the clinical courses and discuss the resultant haemodynamics, highlighting the importance of flow to each lung, the resulting haemodynamic implications and the compounding effects of additional lesions.

A branch pulmonary artery found to be arising from the aortic arch has a significant probability of being duct-dependent.

Stenting of an aberrant pulmonary artery with systemic arterial origin with an otherwise normal heart may lead to significant early- and medium-term haemodynamic instability.

Presence of an atrial septal defect can significantly complicate the haemodynamics.

Introduction

A unilateral disconnected pulmonary artery supplied by an ipsilateral patent ductus arteriosus is rare. Understanding the incidence is difficult due to varying terminology (hemitruncus, unilateral anomalous origin of a pulmonary artery,, or ductal origin of a pulmonary artery,). Additionally, some with an absent branch pulmonary artery may have undergone disconnection of a ductal origin of the pulmonary artery following duct closure. Association with a number of other lesions further complicates estimates of incidence., Surgical re-anastomosis is well-established.,,

Trans-catheter stent implantation to maintain ductal patency was performed first in 1992,, and developments in stent technology as well as evolution of the technique have contributed to improved outcomes.

Within the heterogeneous group presenting for duct stenting is a small subset with duct-dependency of a single lung. Here we compare three such cases to illustrate the challenging haemodynamic situation that may result. In the first two, the right pulmonary artery (RPA) arose from a right ductus originating at the base of the innominate artery in the context of bilateral patent arterial ducts, initially managed with trans-catheter stenting of the occluded right ductus. This resulted in marked instability requiring early surgical reconnection of the disconnected pulmonary artery. We contrast the clinical course with another patient with tetralogy of Fallot (TOF) and a disconnected left pulmonary artery (LPA), in whom stenting of the right ventricular outflow tract (RVOT) and left arterial duct were performed sequentially, resulting in an excellent haemodynamic state for several months.

Case presentations

Case 1

A term, 3.1 kg male infant with 22q11 microdeletion syndrome presented in on Day 2 of life with dyspnoea. Examination yielded a soft murmur and moderate increase in work of breathing. Echocardiography demonstrated an RPA arising from the base of the innominate artery of a left-sided aortic arch (). A left-sided arterial duct arose from the aortic isthmus to the LPA, shunting bi-directionally. The intra-cardiac anatomy was normal with the LPA connected to the main pulmonary artery (MPA). A computed tomography (CT) scan performed on Day 6 of life showed the RPA had disconnected (Supplementary material online, ), indicating the connecting vessel was a ductus. The left ductus had closed.

Cardiac catheterization demonstrated the previous ductal origin from an ampulla at the origin of the innominate artery (). The right duct was crossed easily and two 3.5 × 9 mm Medtronic Integrity bare-metal stents (Medtronic Plc, Minnesota, USA) placed with a good angiographic result ().

Although extubated immediately, urgent reintubation was required due to torrential acute ipsilateral pulmonary oedema, with white-out of the right lung on chest X-ray (Supplementary material online, ). He was successfully extubated 48 h later, but over the coming weeks struggled with dyspnoea and poor weight gain. Echocardiography demonstrated both right ventricular dilatation and evidence of systemic pressure in the right ventricle (and thus the LPA, ) with a bidirectional, but predominant left-to-right inter-atrial shunt.

Following failure to wean from high-flow respiratory support, he proceeded to surgical re-implantation of the RPA to the pulmonary trunk 26 days after his stent procedure. The stent was excised and the RPA reconstructed with a porcine pericardial patch, leaving a good surgical and haemodynamic result. His pulmonary hypertensive changes and right ventricular volume load resolved, and he was discharged home.

Five months post-repair, the reconnected RPA was stented with a 6 mm × 16 mm Cook Formula stent, re-dilated 1 year later. No further re-intervention has been required to date at follow-up of 3.5 years.

Case 2

Case two was a 2.7 kg term infant presenting with dyspnoea on Day 2 of life. An echocardiogram demonstrated an RPA originating from the base of the innominate artery of a left-sided aortic arch. Clinical examination demonstrated mild increase in work of breathing and a soft murmur. There was a moderate-sized atrial septal defect (ASD) shunting left to right, and a ductus from the usual site connected to the LPA. The LPA arose normally from the MPA off a normal right ventricle. Diuretics were started, but over the subsequent weeks, he struggled with poor weight gain and ongoing dyspnoea.

At early follow-up, no flow was seen in the RPA on echocardiography and a prostaglandin infusion commenced. Cardiac CT confirmed the vessel had disconnected (Supplementary material online, ). The left ductus had also closed. Given the combination of relatively low weight and significant distance to the MPA, a decision was made for him to proceed to trans-catheter stenting of his occluded right-sided duct.

Angiography demonstrated a small ampulla at the origin of the innominate artery but no flow into the RPA (). The right-sided ductus was crossed () and stented with 3.5 × 12 mm and 3 × 8 mm Medtronic Integrity bare-metal coronary stents ().

Images from case 2. (A) An angiogram from the innominate artery demonstrating the right-sided ductal ampulla. An angiogram in the right pulmonary artery is shown in (B). Trans-catheter stenting successfully recanalizes the right pulmonary artery (C). An echocardiographic still from the parasternal short axis demonstrates the dilated and both pressure- and volume-loaded right ventricle following stenting of the right pulmonary artery (D).

Although initially extubated, within hours he deteriorated with a marked fall in his mixed venous saturations and severe right-sided chest X-ray changes (Supplementary material online, ) requiring reintubation and a milrinone infusion.

Over the coming days, he experienced significant haemodynamic instability. Echocardiography demonstrated dilatation of the right ventricle with evidence of high right ventricular (and thus LPA) pressures (). There was generous flow down the stent into the right lung with diastolic flow reversal in the arch. Flow across the ASD was significant with a large left-to-right shunt.

Although the chest X-ray changes resolved (Supplementary material online, ), he failed to extubate, and with a deteriorating clinical state, surgical anastomosis of the aberrant RPA to the MPA with fenestrated ASD closure was performed 8 days after his catheter intervention using an autologous pericardial patch to augment the vessel. Pre-discharge echocardiography demonstrated a normally sized right ventricle with normal pulmonary artery pressures.

One year post-intervention, no further interventions have been required.

Case 3

A male infant was born at term with a birthweight of 2.5 kg following an antenatal diagnosis of TOF. His baseline saturations were in initially in the 80s with a soft murmur and normal work of breathing. The LPA arose from the base of a left innominate artery off a right-sided aortic arch. Although initially well, he developed hypercyanotic spells over the first few days. Prostaglandin infusions and propranolol were commenced. The LPA remained patent, but there was marked flow acceleration across a narrow RVOT, so he was put forward for RVOT stenting to secure antegrade flow to the RPA.

He proceeded to the catheterization laboratory at 11 days of age. The RVOT was crossed and stented with a single 4.5 × 15 mm Medtronic Integrity bare-metal stent from a right internal jugular approach ().

Figure 3

Images from case 3. (A) and (B) are taken from the right ventricular outflow tract stenting procedure, with the initial angiogram demonstrating severe stenosis of the right ventricular outflow tract in (A) and the final result with relief of stenosis post-stenting in (B). (C) An angiographic frame from the ductal stenting procedure with severe stenosis of the ductus feeding the left pulmonary artery, relieved following stenting with good anterograde flow in (D).

A prostaglandin infusion was continued to maintain ductal patency into the LPA. He returned to the catheterization laboratory on Day 20 of life. The ductus supplying the LPA was severely stenosed and stented with a 3 × 12 mm Medtronic Driver and a 3 × 8 mm Abbott Multi-link (Abbott Laboratories, IL, USA) bare-metal stents (). He made excellent clinical progress and was discharged home 6 days later.

Complete surgical repair with VSD closure, removal of the right ventricular and ductal stents, reconnection of the LPA, and placement of a pulmonary trans-annular patch was performed at 6 months of age and at 6.5 kg.

He is well and at 1 year post-complete repair no further intervention has been required.

Discussion

Stenting of the arterial duct to both lungs is a regularly performed and well-understood procedure., Stenting to a single lung, however, is rarer and as such less well understood.,,

Our first two cases are examples of ductal origin of a branch pulmonary artery with confirmed bilateral arterial ducts in otherwise normal hearts, where one pulmonary artery arises normally from the right ventricle but the other solely supplied by a ductus. Diagnosis was made in the early postnatal period and supply lost to the aberrantly supplied lung following ductal closure. They were initially managed with stenting of the occluded ductus to re-establish flow and allow growth prior to definitive repair. Both suffered an adverse haemodynamic response necessitating semi-urgent surgical repair during the same admission.

In our patents, we observed two phases to the haemodynamic response following re-recruitment of the disconnected lung. There is an immediate response consisting of unilateral chest X-ray changes with pulmonary oedema in the stented lung, and a later phase with high right ventricular pressures and ventricular dilatation.

We propose that the early phase of unilateral pulmonary oedema results primarily from acute reperfusion injury to the stented lung, exacerbated by an associated increase in left ventricular end-diastolic pressure (LVEDP) from the acute increase in preload. With institution of mechanical ventilation and diuretic therapy, this reverses over a period of days.

Following recovery from this early phase and with resolution of the unilateral chest X-ray changes, both our patients continued to struggle, with evidence of high right ventricular pressures and marked right ventricular dilatation on echocardiography (). We suggest this results from a high pulmonary blood flow state to both lungs, leading to both pre- and post-capillary pulmonary hypertension, exacerbated by an atrial shunt.

Figure 1

Images from case 1. (A) An echocardiographic still frame showing the right pulmonary artery arising from the base of the innominate artery. The aortic angiogram is shown in (B), with the residual ductal ampulla well-demonstrated. The final result post-stenting is shown in (C), with good filling of the right pulmonary artery. The apical four-chamber view in (D) shows the dilated volume and pressure-loaded right ventricle following stenting.

In this anatomy, the normally connected lung receives a twice-normal blood volume, as all the systemic venous return is pumped from the right ventricle into this single lung (). In the stented lung, pulmonary flow is dictated by stent diameter and length. Without appreciation that the stented vessel supplies only one lung, excess flow results. In our patients, this may well be compounded by a relatively proximal source of blood flow from the aorta.

Figure 4

Diagrams demonstrating our proposed models of the physiology following stenting of a single ductal origin of a branch pulmonary artery and the compounding effects of an atrial communication. Digits represent the volume of a ‘cardiac output’ by convention. (A) The normal circulation with a systemic to pulmonary flow ratio (Qp:Qs) of 1:1. (B) The physiology of unilateral pulmonary artery from the aorta in the absence of an atrial communication, assuming flow of one cardiac output to the aberrant lung. The total Qp:Qs is 2:1. (C) The physiology with an additional atrial communication. Note the normally connected lung (LPA) sees four times the normal blood flow (total Qp:Qs is 3:1). LA, left atrium; LPA, left pulmonary artery; LV, left ventricle; RA, right atrium; RPA, right pulmonary artery; RV, right ventricle.

Therefore, we propose that a high-flow (and thus high preload) state exists to both lungs, and with a 3.5 mm stent in an otherwise normal heart, the minimum Qp:Qs is 2:1 (). With high pulmonary blood flow, pulmonary venous return is also increased, leading to both increased preload and LVEDP, driving post-capillary pulmonary hypertension.

Any additional left-to-right shunt (such as an ASD) has to be accommodated by the single normally connected lung. Given this lung sees twice-normal blood flow (as the only outlet from the right ventricle), this doubles the effect of any left-to-right shunt (). An ASD therefore increase pre- and post-capillary pressures to the normally connected lung and post-capillary pressure to the stented lung ().

Theoretically, therefore there results high pre-and post-capillary pressures to both lungs following stenting. Although the relative effects to each lung may well be discrepant, the resulting haemodynamic state is extremely challenging. Our patients were also neonates, and usual postnatal adaptation of the pulmonary vasculature is unlikely to have completed, compounding the induced pulmonary hypertension. Also, diastolic runoff to the stented lung can also affect both coronary and systemic blood flow, potentially generating a low cardiac output state.

There are three options from this point for the first two patients. Surgical re-anastomosis of the stented lung would immediately correct the physiology. Surgical reconnection of an aberrant pulmonary artery was first described with an interposition graft, followed soon afterwards by a primary anastomosis. A number of techniques have been subsequently described.,,

Another option would be to close the atrial communication, although this would only partly correct the deleterious physiology. Interventionally, this has been performed in this context at 6 months of age but did not significantly alter clinical course. Surgical closure would likely be challenging due to venous return from the stented lung on bypass in the context of a relatively small, pulmonary hypertensive patient.

The third option is to limit pulmonary blood flow. Banding or clipping the stent to reduce flow is likely to improve the haemodynamics, albeit potentially again unpredictably, and increased risk of stent occlusion.

In contrast to patients one and two, our 3rd patient with TOF made excellent progress following stenting of the ductus. Pulmonary flow in the context of TOF is fundamentally different, as the starting Qp:Qs is <1:1, whereas the starting point in the first two patients with otherwise normal anatomy is Qp:Qs is 1:1 prior to stenting and augmented from there.

In patients with isolated ductal origin of a single pulmonary artery, haemodynamic instability and hypertension in the stented lung occur in a significant proportion of patients. One multicentre report has described 10 patients developing pulmonary hypertension, proposing a number of mechanisms of failure. The experience from both our studies highlights the multifactorial haemodynamic problems in this setting.

In conclusion, the physiology following trans-catheter intervention for a single, isolated disconnected pulmonary artery is extremely challenging and can lead to marked haemodynamic instability. At diagnosis, the possibility of bilateral ducts and possible loss of flow to one lung must be considered, and at intervention, care must be taken to limit stent size and the haemodynamic effects of an ASD considered.

Lead author biography

Following paediatric cardiology training in London, Southampton, and Leeds, Dr Andrew B. Ho works as a consultant paediatric cardiologist at Southampton General Hospital in the UK. His special interest is in congenital cardiac intervention in both children and adults.

Supplementary material

Supplementary material is available at European Heart Journal - Case Reports online.

Slide sets: A fully edited slide set detailing this case and suitable for local presentation is available online as Supplementary data.

Consent: The authors confirm that written consent for submission and publication of this case report including images and associated text has been obtained from the patients' next-of-kin in line with COPE guidance.

Conflict of interest: None declared.

Funding: None declared.

Click here for additional data file.

Case 1
Day 2	Diagnosis of right aberrant pulmonary arising from innominate artery
Day 5	Computed tomography scan demonstrating disconnection of right pulmonary artery (RPA). Prostaglandin infusion started
Day 9	Stenting of occluded ductus supplying RPA
One month	Surgical re-anastomosis of RPA to main pulmonary artery
Case 2
Day 2	Diagnosis of right aberrant pulmonary arising from innominate artery
5 weeks	Right pulmonary artery found to have disconnected
6 weeks	Stenting of occluded ductus supplying RPA
7 weeks	Surgical re-anastomosis of RPA to main pulmonary artery
Case 3
11 days	Right ventricular outflow stenting
20 days	Stenting of ductus supplying left pulmonary artery (LPA)
6 months	Repair of tetralogy of Fallot with stent removal and reconnection of LPA to main pulmonary artery