Lung transplantation as an intervention for pediatric pulmonary hypertension

Pediatric Lung Transplantation for Pulmonary Vascular Diseases: Recent Advances and Challenges

Pediatric lung transplantation for pulmonary vascular diseases has seen notable advancements and trends. Medical therapies, surgical options, and bridging techniques like extracorporeal membrane oxygenation and different forms of transplants have expanded treatment possibilities. Current challenges include ensuring patient adherence to post-transplant therapies, addressing complications like primary graft dysfunction and rejection, and conducting further research in less common conditions like pulmonary veno-occlusive disease and pulmonary vein stenosis. In this review article, the authors will explore the advancements, emerging trends, and persistent challenges in pediatric lung transplantation for pulmonary vascular diseases.

Lung transplantation in children

Lung transplantation is a well-established treatment for children facing advanced lung disease and pulmonary vascular disorders. However, organ shortage remains highest in children. For fitting the small chest of children, transplantation of downsized adult lungs, lobes, or even segments were successfully established. The worldwide median survival after pediatric lung transplantation is currently 5.7 years, while under consideration of age, underlying disease, and peri- and posttransplant center experience, median survival of more than 10 years is reported. Timing of referral for transplantation, ischemia-reperfusion injury, primary graft dysfunction, and acute and chronic rejection after transplantation remain the main challenges.

Bilateral lung transplantation for pediatric pulmonary arterial hypertension: perioperative management and one-year follow-up

Background

Bilateral lung transplantation (LuTx) remains the only established treatment for children with end-stage pulmonary arterial hypertension (PAH). Although PAH is the second most common indication for LuTx, little is known about optimal perioperative management and midterm clinical outcomes.

Methods

Prospective observational study on consecutive children with PAH who underwent LuTx with scheduled postoperative VA-ECMO support at Hannover Medical School from December 2013 to June 2020.

Results

Twelve patients with PAH underwent LuTx (mean age 11.9 years; age range 1.9-17.8). Underlying diagnoses included idiopathic (n = 4) or heritable PAH (n = 4), PAH associated with congenital heart disease (n = 2), pulmonary veno-occlusive disease (n = 1), and pulmonary capillary hemangiomatosis (n = 1). The mean waiting time was 58.5 days (range 1-220d). Three patients were bridged to LuTx on VA-ECMO. Intraoperative VA-ECMO/cardiopulmonary bypass was applied and VA-ECMO was continued postoperatively in all patients (mean ECMO-duration 185 h; range 73-363 h; early extubation). The median postoperative ventilation time was 28 h (range 17-145 h). Echocardiographic conventional and strain analysis showed that 12 months after LuTx, all patients had normal biventricular systolic function. All PAH patients are alive 2 years after LuTx (median follow-up 53 months, range 26-104 months).

Conclusion

LuTx in children with end-stage PAH resulted in excellent midterm outcomes (100% survival 2 years post-LuTx). Postoperative VA-ECMO facilitates early extubation with rapid gain of allograft function and sustained biventricular reverse-remodeling and systolic function after RV pressure unloading and LV volume loading.

Monitoring practices of chronic lung allograft dysfunction in pediatric lung transplantation

INTRODUCTION

Chronic lung allograft dysfunction (CLAD) continues to negatively impact the survival of pediatric lung transplant (LTx) recipients. Current consensus guidelines are adult-focused. We sought to examine CLAD detection and monitoring practices at pediatric LTx programs.

METHODS

We conducted a survey among the International Pediatric Lung Transplant Collaborative. Questions consisted of practitioner's experience, LTx program demographics, and querying tests used for CLAD surveillance and detection. Investigations queried included: chest x-ray (CXR), chest computed tomography (CT), lung magnetic resonance imaging (MRI), ventilation/perfusion scanning, conventional pulmonary function testing (PFT), multiple breath washout (MBW), infant/preschool PFT, bronchoalveolar lavage, transbronchial biopsies (TBBx), or other tissue sampling techniques. Preferences for certain modalities over others were questioned based on a five-point Likert scale.

RESULTS

Twenty-four of 25 programs responded. Chest CT and CXR are used generally for both CLAD surveillance and detection. No programs use lung MRI clinically, it may have some utility in the future. While all centers use conventional PFT, MBW, and infant/preschool PFT are used in one-fifth and one-third of centers, respectively. While the majority of programs use TBBx, only 41.7% would obtain a diagnosis based on tissue histopathology over noninvasive techniques if CLAD is suspected. Utilization of biomarkers is still limited.

CONCLUSIONS

Our results indicate continued use of conventional PFT along with chest CT and less so CXR for CLAD detection and monitoring in the large majority of centers. Infant/preschool PFT and novel methods such as MBW are used in a few centers only. Respondents agreed there is a timely need for pediatric consensus guidelines on CLAD detection and monitoring.

The changing landscape of pediatric lung transplantation

There has been a shift over decades in the diagnostic indications for lung transplantation in children; in particular, there has been a reduction in the proportion of pediatric cystic fibrosis (CF) patients undergoing lung transplantation early in life, and more transplants occurring in other diagnostic groups. Here, we examine trends in pediatric lung transplantation with regards to indication by analyzing data from the United Network of Organ Sharing, the International Society for Heart and Lung Transplantation Thoracic Transplant Registry, and other sources. Over the past two years, there has been a precipitous decline in both the number of transplants due to CF and the proportion of CF cases relative to the total number of transplants, likely not solely due to the COVID-19 pandemic. In 2020, primary pulmonary arterial hypertension for the first time surpassed CF as main indication for pediatric lung transplantation in the United States, a finding that is also reflected in international data. We discuss the effect of novel CFTR modulator therapies as a major factor leading to this shifting landscape. Based on our trending, pulmonary hypertension-related diagnoses and pediatric interstitial lung diseases are rising indications, for which we suggest adjustments of consensus guidelines around candidate selection criteria. This article is protected by copyright. All rights reserved.

Full recovery of right ventricular systolic function in children undergoing bilateral lung transplantation for severe PAH

BACKGROUND

We investigated whether RV function recovers in children with pulmonary arterial hypertension (PAH) and RV failure undergoing lung transplantation (LuTx).

METHODS

Prospective observational study of 15 consecutive children, 1.9 to 17.6 years old, with PAH undergoing bilateral LuTx. We performed advanced echocardiography (Echo) and cardiac magnetic resonance imaging (MRI), followed by conventional and strain analysis, pre- and ∼6 weeks post-LuTx.

RESULTS

After LuTx, RV/LV end-systolic diameter ratio (Echo), RV volumes and systolic RV function (RVEF 63 vs 30 %; p < 0.05) by MRI completely normalized, even in children with severe RV failure (RVEF < 40%). The echocardiographic end-systolic LV eccentricity index nearly normalized post-LuTx (1.0 vs 2.0, p < 0.0001) while RV hypertrophy regressed more slowly and was still evident. We found especially the end-systolic RV/LV ratios by Echo (diameter: 0.6 vs 2.6) or MRI (volumes: 0.8 vs 3.4) excellent diagnostic tools (p < 0.05): Together with RVEF by MRI, these ratios were superior to tricuspid annular plane systolic excursion (TAPSE; p = 0.4551) in assessing global systolic RV dysfunction. Moreover, children with severe PAH had reduced RV 2D longitudinal strain (Echo, MRI; p = 0.0450) and decreased RV 2D radial and circumferential strain (MRI; p = 0.0026 and p = 0.0036 respectively), all of which greatly improved following LuTx.

CONCLUSION

We demonstrate full recovery of RV systolic function in children within two months after LuTx for severe PAH, independently of the patients' age, weight, and hemodynamic compromise preceding the LuTx. Even in end-stage pediatric PAH with poor RV function and low cardiac output, LuTx should be preferred over heart-lung transplantation.