Bilateral lung transplantation for pediatric idiopathic pulmonary arterial hypertension: a multi-center experience

Lung Transplantation for Pulmonary Vascular Disease in Children: A United Network for Organ Sharing Analysis

Pulmonary vascular disease (PVD) represents an important clinical indication for lung transplant (LTx) in infants, children, and adolescents. There is limited information on LTx outcomes in these patients. We explored LTx volumes and post-LTx survival in children with PVD compared to other diagnoses. The UNOS Registry was queried from 1989 to 2020 to identify first-time pediatric LTx recipients (< 18 yo). PVD was categorized as idiopathic pulmonary arterial hypertension (IPAH) and non-idiopathic arterial hypertension (non-IPAH) and compared to all other patients as other diagnoses. Univariate and multivariate regression models were performed. 984 pediatric LTx patients (593 before 2010 and 391 during/after 2010) were identified, of which 145 (14.7%) had PVD. There has been no significant change in annual rate of all LTxs over comparative eras. However, there has been a decrease in rate of LTxs for PVD patients. Children with PVD had similar survival to other LTx groups in the early era (p = 0.2) and the latter era (p = 0.9). Univariate Cox models, showed that LTx in patients with PVD was associated with a significantly less risk of mortality for children aged 6-11 years compared to younger and older cohorts (HR = 0.4 [0.17-0.98]; p = 0.045), whereas multivariate analysis showed a trend toward higher mortality in 11-17-year-olds (HR = 1.54 [0.97-2.45]; p = 0.06). For PVD patients, oxygen supplementation and ventilator support at LTx were associated with worse post-transplant survival (p = 0.029 and p = 0.01). There has been a decrease in LTx volume for pediatric patients with PVD in the modern era. Post-LTx outcomes for children with PVD are similar to those of other diagnoses in both eras, with children aged 6-11 years having the best survival. Given these findings, LTx should be considered for this patient population.

Lung Transplantation for Pulmonary Vascular Disease in Children: A United Network for Organ Sharing Analysis

Background

Pulmonary vascular disease (PVD) represents an important clinical indication for lung transplant (LTx) in infants, children, and adolescents. There is limited information on LTx outcomes in these patients. We explored LTx volumes and post-LTx survival in children with PVD compared to other diagnoses.

Methods

The UNOS Registry was queried from 1989-2020 to identify first-time pediatric LTx recipients (<18 yo). PVD was categorized as idiopathic pulmonary arterial hypertension (IPAH) and non-idiopathic arterial hypertension (non-IPAH) and compared to all other patients as other diagnoses. Univariate and multivariate regression models were performed.

Results

984 pediatric LTx patients (593 before 2010 and 391 during/after 2010) were identified, of which 145 (14.7%) had PVD. There has been no significant change in annual rate of all LTxs over comparative eras. However, there has been a decrease in rate of LTxs for PVD patients. Children with PVD had similar survival to other LTx groups in the early era (p=0.2) and the latter era (p=0.9). Univariate Cox models, showed that LTx in patients with PVD was associated with a significantly less risk of mortality for children aged 6-11 years compared to younger and older cohorts (HR=0.4 [0.17-0.98];p=0.045), whereas multivariate analysis showed a trend towards higher mortality in 11-17-year-olds (HR=1.54 [0.97-2.45];p=0.06). For PVD patients, oxygen supplementation and ventilator support at LTx were associated with worse post-transplant survival (p=0.029 and p=0.01).

Conclusions

There has been a decrease in LTx volume for pediatric patients with PVD in the modern era. Post-LTx outcomes for children with PVD are similar to those of other diagnoses in both eras, with children aged 6-11 years having the best survival. Given these findings, LTx should be considered for this patient population.

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.

Lung transplantation for pediatric pulmonary arterial hypertension-quo vadis?

In children with pulmonary arterial hypertension, lung transplantation illustrates a feasible treatment option once pharmacological therapy is exhausted. Timing of listing for lung transplantation in children remains difficult since hemodynamic deterioration often occurs abruptly and the time on the waiting list is usually hard to predict. Clear contraindications for lung transplantation are recent history of malignancies as well as irreversible end-organ failure. Generally, patients with pulmonary arterial hypertension in the absence of structural cardiac defects can safely undergo bilateral lung transplantation, combined heart-lung transplantation remains a procedure with a higher perioperative risk and should only be performed in selected cases with irreversible structural defects. Donor selection in recent years shows donors with extended criteria as well as lobar transplantation with good outcome, having the positive effect of broadening of the donor pool. Bridging to lung transplantation with veno-arterial ECMO treatment is feasible and has a good outcome in experienced transplant centers. Surgical considerations should include the risk of hemodynamic decompensation upon anesthesia induction and the need for extracorporeal support pre-, intra- and postoperative. Lung transplantation should be performed on veno-arterial ECMO support with either peripheral (>20 kg) or central cannulation (<20 kg). The surgical transplantation procedure includes the bronchial anastomosis as well as anastomoses of the pulmonary artery and the left atrium. Postoperative prolonged veno-arterial ECMO treatment for the immediate postoperative period allows for left ventricular remodeling given the new hemodynamic circumstances with lower pulmonary vascular resistance. Standard triple immunosuppression in most lung transplant programs currently includes steroids, mycophenolate mofetil and tacrolimus. Survival after pediatric lung transplantation for IPAH is comparable to pediatric lung transplants for other underlying diseases with a 1-year survival of approx. 80% and a 5-year survival of 64-65%. Therefore, evolving techniques in the field of lung transplantation led to overall improved survival prospects in children with end-stage pulmonary vascular disease.

Lung transplantation as an intervention for pediatric pulmonary hypertension

Lung transplantation is a treatment option for selected children with end-stage lung disease and pulmonary vascular disorders. Overall, pulmonary hypertension (PH) is the second most frequent indication for infants and children requiring lung transplants. In pediatric PH patients, timing for listing remains a difficult decision due to patient heterogeneity and varying allocation policies across different countries. Furthermore, perioperative management can be challenging, making interdisciplinary collaboration among surgical, anesthesiology, critical care, and lung transplant teams essential. Because pediatric PH patients typically have preserved cardiac index and exercise tolerance even with advanced disease, they should be referred early even if they do not meet the criteria for listing of primarily adults by International Society for Heart and Lung Transplantation (ISHLT) published in 2015: New York Heart Association (NYHA) functional class III or IV without improvement, cardiac index < 2 L/min/m² , mean right atrial pressure of >15 mmHg. Bridging strategies with extracorporeal support should be determined at the time of listing in anticipation of possible clinical deterioration. Bilateral lung transplantation using cardiopulmonary bypass to provide hemodynamic stability is nowadays the standard surgical approach in pediatric centers. The immediate post-transplant period is characterized by dramatic changes in the right ventricle (RV) and and left ventricle (LV) anatomy and physiology, which can be life-threatening. Induction, immunosuppression, prophylaxis, and surveillance are not different from patients without PH. Overall, outcomes in pediatric lung and heart-lung transplant patients for PH are not different from those children undergoing transplantation for other indications. In fact, long-term survival is superior in children with idiopathic PH compared to other diseases, providing most recipients with improved quality of life.

A case series of transcatheter Potts Shunt creation in a pediatric population affected with refractory pulmonary artery hypertension: focus on the role of ECMO

PURPOSE

Patients with suprasystemic idiopathic pulmonary hypertension (S-PAH) have a poor prognosis. Therapeutic options are limited. Reverse Potts shunt creation modifies physiology transforming patients with PAH into Eisenmenger physiology with a better outcome. Percutaneous transcatheter stent secured aortopulmonary connection (transcatheter Potts Shunt, TPS) is a feasible very high-risk procedural option in such patients. We report our experience with patients undergoing TPS at our institution requiring extracorporeal membrane oxygenation (ECMO) support.

METHODS

A prospective observational study of patients with drug-refractory PAH, worsening NYHA class, and right ventricular failure undergoing TPS. Two patients required rescue ECMO for cardiac arrest during the procedure. Subsequently, "standby ECMO" was available in all the following cases and elective support was provided in patients with extremely poor conditions.

RESULTS

Ten pediatric patients, underwent TPS at our institution. Two patients were rescued by ECMO after cardiac arrest during the shunt creation. This occurred as a result of the acute loading of the left ventricle (LV) after retrograde aortic arch filling through the Potts shunt. Following this, another two patients underwent elective ECMO after the uneventful induction of anesthesia. They all died postoperatively despite a successful TPS procedure. The causes of death were not related to the use of ECMO, but the complication of severe PAH. Six patients with successful TPS did not require ECMO and survived.

CONCLUSIONS

TPS is a pioneering procedure offering the opportunity to treat high-risk idiopathic drug-refractory PAH patients. Acute LV failure is a complication of TPS in patients with S-PAH. Elective ECMO, an option to avoid circulatory arrest and acute profound hypoxia secondary to exclusive right-to left shunt systemic perfusion by Potts shunt and LV dysfunction with resulting pulmonary edema, may be used at the early stage of the learning curve, but it does not influence the prognosis of these patients which remains poor.

Current and advancing treatments for pulmonary arterial hypertension in childhood

Pulmonary arterial hypertension (PAH) is a severe and progressive intrinsic disease of the precapillary lung vasculature. Since the introduction of PAH-targeted drugs, survival of PAH patients seems to have improved. Randomized controlled trials have led to evidence-based guidelines to direct treatment in adults. However, since disease characteristics differ between adults and children, it is hazardous to simply extrapolate these guidelines to children. Moreover, pediatric data on treatment strategies and how to assess treatment response remain virtually absent. Optimal treatment strategies are highly needed to guide therapy and improve survival in children with PAH. This review provides an overview of currently available treatments for PAH and the limited efficacy and safety data in children (with the exclusion of perinatal pulmonary vascular diseases, as persistent pulmonary hypertension of the newborn). We also discuss potential treatment goals and how the available data can be translated into treatment strategies in pediatric PAH.

Current challenges in pediatric pulmonary hypertension

Pulmonary arterial hypertension (PAH) in the pediatric population is associated with a variety of underlying diseases and causes, significantly morbidity and mortality. In the majority of patients, PAH in children is idiopathic or associated with congenital heart disease (CHD), with pulmonary hypertension (PH) associated with connective tissue disease, a rare cause in children. Classification of pediatric PH has generally followed the WHO classification, but recognition of the importance of fetal origins of PH and developmental abnormalities have led to the formation of a new pediatric-specific classification. Incidence data from the Netherlands has revealed an annual incidence and point prevalence of 0.7 and 4.4 for idiopathic PAH and 2.2 and 15.6 for associated pulmonary arterial hypertension-CHD cases per million children. Although the treatment with new selective pulmonary vasodilators offers hemodynamic and functional improvement in pediatric populations, the treatments in children largely depend on results from evidence-based adult studies and experience of clinicians treating children. A recent randomized clinical trial of sildenafil and its long-term extension has led to disparate recommendations in the United States and Europe.

Idiopathic and Heritable Pulmonary Hypertension in Children: New Insights into Causes, Evaluation, and Treatment

Over the past decade, major progress has occurred in the care of children and adults with pulmonary arterial hypertension (PAH). Recent insights into molecular mechanisms implicated in the development of pulmonary vascular disease have led to revised clinical classification and diagnostic strategies.1 Data from multicenter pulmonary hypertension registries have provided increased understanding of the clinical course and natural history of many subtypes of disease.2–4 Additionally, the development of multiple therapies targeting important pathways of disease and the translation of those treatments to pediatrics have led to improved life experience and survival for many children with PAH.5