Hybridizing the hybrid: a “serendipitous bridge” to heart transplantation in a child with hypoplastic left heart syndrome

Abstract

We report a unique experience with stage 1 palliation of hypoplastic left heart syndrome (HLHS) using the hybrid approach. The tortuous anatomy of the ductus arteriosus precluded stenting. Persistent ductal patency and ability to support the systemic circulation adequately after prolonged prostaglandin E1 (PGE1) infusion and its subsequent discontinuation presented us with a novel approach to hybrid palliation of hypoplastic left heart syndrome. Our experience offers a tempting approach, but it should not be considered a standard alternative management option to stage I hybrid palliation based on a single case report.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12055-020-01088-8.

Introduction

Ductal stenting with bilateral pulmonary artery banding with possible atrial septal stenting comprises the hybrid approach to stage I palliation. It is advocated by various institutions in high-risk subgroups of neonates with hypoplastic left heart syndrome (HLHS) [1, 2].

Avoidance of cardiopulmonary bypass and myocardial ischemia in these sick babies and the potential significant operative mortality associated with the Norwood operation are the underlying rationales for this approach. The benefits of the hybrid procedure are accentuated in pre-term, low birth weight children and in those with severe ventricular dysfunction, severe atrioventricular valve regurgitation, and extracardiac comorbidities. The hybrid strategy provides an alternative palliative approach for these patients prior to stage II palliation or heart transplantation. We present our experience and approach with the hybrid procedure.

Case report

A 3.5-week-old full-term male neonate presented with HLHS. He had symptoms of lethargy, poor feeding, cyanosis, and congestive heart failure. His initial echocardiogram demonstrated severe mitral and aortic stenosis with a hypoplastic left ventricle, severe right ventricular dysfunction, and severe tricuspid valve regurgitation (Fig. 1).

Fig. 1.

Preoperative echocardiogram showing severe tricuspid valve regurgitation

He was resuscitated and stabilized with mechanical ventilation, inotropes, and prolonged prostaglandin E1 (PGE1). Given his delayed presentation, significant right ventricular dysfunction, and severe tricuspid regurgitation, stage I hybrid palliation was felt to be the optimal initial intervention.

He underwent bilateral pulmonary artery banding using 3.5-mm Gore-Tex grafts and atrial septal stenting. His ductus arteriosus was tortuous and aneurysmal; hence, an appropriate stent could not be deployed (Video 1). PGE1 infusion was continued at 0.01 μg/kg/min. He was subsequently extubated and made an uneventful recovery. His comorbid conditions directed his future care plan, and he was listed for cardiac transplantation [3]. Our decision was based on the experience of poor outcomes following Norwood reconstruction in subsets of children with severe atrioventricular valve regurgitation coupled with suboptimal right ventricular function [4]. Our team consensus was that the optimal strategy for this child was heart transplantation. A long-term intravenous line was placed, and the baby was discharged home on intravenous PGE1 with nurse practitioner-led parental teaching and weekly rigorous outpatient surveillance.

Serial imaging demonstrated progressive improvement of ventricular function, a widely patent ductus arteriosus (PDA), which was bi-directional, and laminar flow across the atrial stent, but there was persistent severe tricuspid regurgitation. There was good flow in the descending aorta and retrograde flow in the ascending aorta. Pulmonary artery (PA) band gradients were unchanged at 65 mmHg. Tricuspid regurgitation was persistently severe and surrogate of right ventricular function like transannular plane systolic excursion of tricuspid valve (TAPSE) was 8 mm and fractional shortening (FS) of the systemic ventricle was 20%, clearly indicating suboptimal function. Clinically, the child thrived and maintained oxygen saturations between 80 and 85%. He did not receive any additional interstage interventions.

At 6 months of age, a decision was made for a trial discontinuation of the PGE1. The child’s ductus arteriosus remained widely patent as documented by serial echocardiograms and a chest computed tomography (CT) scan (Fig. 2).

Fig. 2.

Large tortuous PDA (arrow mark) which could not be stented. Hypoplastic aortic arch (asterisk mark) seen. Atrial stent seen in situ

At 19 months of age, a suitable donor heart was identified, and the child underwent orthotopic heart transplantation. He required 48 h of extracorporeal membrane oxygenation (ECMO) support post-operatively for primary graft but recovered well thereafter. He was discharged home on post-operative day 10. His 6-week post-transplant echocardiogram showed normal ventricular function. Cardiac catheterization demonstrated normal hemodynamics and he continues to thrive.

Discussion

Ductal wall tone in utero is a complex interplay between the constricting effects of oxygen and the dilating effects of endogenous prostaglandins. As term approaches, the ductus becomes less responsive to PGE1 and more responsive to oxygen, setting the stage for functional closure after birth in term babies. Anatomically, ductal closure is mediated by subendothelial edema and infolding of endothelium with fragmentation of internal elastic lamina and sealing of the lumen by endothelial cell apposition and smooth muscle cell proliferation and apoptosis [5]. Ducts destined to remain patent, especially in term babies, do not demonstrate any of these anatomical changes with the endothelial cells being tightly adhered to internal elastic lamina [5].

The hybrid approach is an established alternative for stage 1 palliation for children with HLHS. We describe a unique experience. The persistent patency of an unstented ductus arteriosus after cessation of PGE1 was serendipitous. It gives rise to the speculation whether, after a certain period of time, the histologic nature of the ductus makes spontaneous closure unlikely [6]. In this case, the histology of the native duct revealed extensive myxoid degeneration.

Conclusion

Our case report highlights a unique hybrid approach for stage I palliation. Ductal stenting was avoided after prolonged intravenous PGE1 therapy and its subsequent discontinuation. The PDA remained patent and supported the systemic circulation adequately. The patient was successfully bridged to heart transplantation.

• The clinical conduct and course of the patient in this unusual and unintended approach was a unique experience for us (Video 2).

• Though it cannot be suggested as a viable alternative option to conventional stage I hybrid palliation, the potential for long-term ductal patency without PGE1 can be considered in very select circumstances.

Funding

None.

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.

Informed consent

Consent was taken from the parents of the patient to publish this case report.

Human and animal rights involvement

Not applicable.

Ethics committee approval

Not applicable.