Potts Shunt to Be Preferred Above Atrial Septostomy in Pediatric Pulmonary Arterial Hypertension Patients: A Modeling Study

Thirty years of surgical management of pediatric pulmonary hypertension: Mid-term outcomes following reverse Potts shunt and transplantation

BACKGROUND

Reverse Potts shunt (RPS) and lung or heart-lung transplantation are life-extending surgical interventions for pediatric patients with severe pulmonary arterial hypertension (PAH). Robust criteria for identifying patients who will benefit from these procedures remain elusive. Based on 30 years of experience, we sought to refine the surgical indications.

METHODS

This single-center retrospective cohort study included 61 consecutive pediatric patients with PAH managed by RPS (2004-2020) or transplantation (1988-2020). Their mid-term outcomes were assessed.

RESULTS

Compared with the 20 patients managed by RPS, the 41 transplant waitlist patients, of whom 28 were transplanted, were older (14.9 vs 8.0 years, P = .0001), had worse right ventricular impairment (tricuspid annular plane systolic excursion, 12.5 mm vs 18.0 mm, P = .03), and were managed later in the evolution of the disease (6.0 vs 1.7 years, P = .002). After implementation of a high-priority allocation program in 2007, waitlist mortality decreased from 52.6% to 13.6% (P = .02) and 5-year survival increased from 57.1% to 74.7% after RPS and 55.6% to 77.2% after transplantation. At a median follow-up of 8.6 years after RPS and 5.9 years after transplantation, functional capacity had improved significantly, and PAH-specific drug requirements had diminished markedly in the RPS group. Two patients successfully underwent double-lung transplant 6 and 9 years after RPS.

CONCLUSIONS

In selected children with suprasystemic PAH, RPS is associated with functional capacity improvements and decreased pharmacotherapy needs over the midterm. RPS deserves consideration earlier in the course of pediatric PAH, with transplantation being performed in the event of refractory RV failure.

Computer simulation of surgical interventions for the treatment of refractory pulmonary hypertension

This paper describes computer models of three interventions used for treating refractory pulmonary hypertension (RPH). These procedures create either an atrial septal defect, a ventricular septal defect or, in the case of a Potts shunt, a patent ductus arteriosus. The aim in all three cases is to generate a right-to-left shunt, allowing for either pressure or volume unloading of the right side of the heart in the setting of right ventricular failure, while maintaining cardiac output. These shunts are created, however, at the expense of introducing de-oxygenated blood into the systemic circulation, thereby lowering the systemic arterial oxygen saturation. The models developed in this paper are based on compartmental descriptions of human hemodynamics and oxygen transport. An important parameter included in our models is the cross-sectional area of the surgically created defect. Numerical simulations are performed to compare different interventions and various shunt sizes and to assess their impact on hemodynamic variables and oxygen saturations. We also create a model for exercise and use it to study exercise tolerance in simulated pre-intervention and post-intervention RPH patients.

Interventionelle Behandlungsverfahren der pulmonalen Hypertension im Kindesalter

Die pulmonale Hypertension (PH) ist eine progressive Gefäßerkrankung und führt über eine Widerstands- und/oder Druckerhöhung im kleinen Kreislauf zu einem fortschreitenden Rechtsherzversagen. Auch wenn mithilfe aktueller medikamentöser Therapien eine deutliche Verbesserung der Lebensqualität und des Überlebens der Betroffenen erreicht werden konnte, bleibt die PH eine zumeist nichtheilbare Erkrankung, die im fortgeschrittenen Stadium eine Lungentransplantation notwendig macht. Interventionelle Verfahren, wie die Anlage eines interatrialen Shunts (z. B. durch atriale Septostomie oder den Atrial Flow Regulator) oder eines Reversed Potts Shunt, verbessern die RV-Funktion und die ventrikuläre Interaktion durch Schaffung einer prä- oder posttrikuspidalen „Eisenmenger-Physiologie“ und stellen eine Überbrückung oder sogar Alternative zur Lungentransplantation dar. Bei Patienten mit segmentaler PH oder chronisch thrombembolischer pulmonaler Hypertension (CTEPH) stellt die Ballonangioplastie eine bereits etablierte Intervention zur Verbesserung der pulmonalen Perfusion und damit rechtsventrikulären (RV-)Funktion dar. Dagegen ist die pulmonalarterielle Denervation ein neuartiges Verfahren, mit dem Ziel, die neurohumorale Dysregulation bei PH positiv zu beeinflussen. Der individuelle Einsatz solcher Interventionen, additiv zu den bereits etablierten medikamentösen Therapien, erweitert die Behandlungsmöglichkeiten und kann die Prognose betroffener Patienten noch weiter verbessern.

Multiscale modelling of Potts shunt as a potential palliative treatment for suprasystemic idiopathic pulmonary artery hypertension: a paediatric case study

Potts shunt (PS) was suggested as palliation for patients with suprasystemic pulmonary arterial hypertension (PAH) and right ventricular (RV) failure. PS, however, can result in poorly understood mortality. Here, a patient-specific geometrical multiscale model of PAH physiology and PS is developed for a paediatric PAH patient with stent-based PS. In the model, 7.6mm-diameter PS produces near-equalisation of the aortic and PA pressures and [Formula: see text] (oxygenated vs deoxygenated blood flow) ratio of 0.72 associated with a 16% decrease of left ventricular (LV) output and 18% increase of RV output. The flow from LV to aortic arch branches increases by 16%, while LV contribution to the lower body flow decreases by 29%. Total flow in the descending aorta (DAo) increases by 18% due to RV contribution through the PS with flow into the distal PA branches decreasing. PS induces 18% increase of RV work due to its larger stroke volume pumped against lower afterload. Nonetheless, larger RV work does not lead to increased RV end-diastolic volume. Three-dimensional flow assessment demonstrates the PS jet impinging with a high velocity and wall shear stress on the opposite DAo wall with the most of the shunt flow being diverted to the DAo. Increasing the PS diameter from 5mm up to 10mm results in a nearly linear increase in post-operative shunt flow and a nearly linear decrease in shunt pressure-drop. In conclusion, this model reasonably represents patient-specific haemodynamics pre- and post-creation of the PS, providing insights into physiology of this complex condition, and presents a predictive tool that could be useful for clinical decision-making regarding suitability for PS in PAH patients with drug-resistant suprasystemic PAH.

Cardiovascular fetal-to-neonatal transition: an in silico model

BACKGROUND

Previous models describing the fetal-to-neonatal transition often lack oxygen saturation levels, homeostatic control mechanisms, phasic hemodynamic signals, or describe the heart with a time-varying elastance model.

METHODS

We incorporated these elements in the adapted CircAdapt model with the one-fiber model for myocardial contraction, to simulate the hemodynamics of the healthy term human fetal circulation and its transition during the first 24 h after birth. The fetal-to-neonatal model was controlled by a time- and event-based script of changes occurring at birth, such as lung aeration and umbilical cord clamping. Model parameters were based on and validated with human and animal data.

RESULTS

The fetal circulation showed low pulmonary blood flow, right ventricular dominance, and inverted mitral and tricuspid flow velocity patterns, as well as high mean ductus venosus flow velocity. The neonatal circulation showed oxygen saturation levels to gradually increase to 98% in the first 15 min after birth as well as temporary left ventricular volume overload.

CONCLUSIONS

Hemodynamics of the term fetus and 24-h-old neonate, as well as the events occurring directly after birth and the transition during the first 24 h after birth, were realistically represented, allowing the model to be used for educational purposes and future research.

IMPACT

With the addition of oxygen saturation levels, homeostatic pressure-flow control mechanisms, and the one-fiber model for myocardial contraction, a new closed-loop cardiovascular model was constructed to give more insight into the healthy term human fetal circulation and its cardiovascular transition during the first 24 h after birth. Extensive validation confirmed that the hemodynamics of the term fetus and the fetal-to-neonatal transition were realistically represented with the model. This well-validated and versatile model can serve as an education as well as a research platform for in silico investigation of fetal-to-neonatal hemodynamic changes under a wide range of physiological and pathophysiological conditions.

Reversed Potts Shunt Outcome in Suprasystemic Pulmonary Arterial Hypertension: A Systematic Review and Meta-Analysis

BACKGROUND

Reversed Potts shunt has been a prospective approach to treat suprasystemic pulmonary hypertension, particularly when medication treatment fails to reduce right ventricular afterload.

OBJECTIVE

This meta-analysis aims to review the clinical, laboratory, and hemodynamic parameters after a reversed Potts shunt in suprasystemic pulmonary hypertension patients.

METHODS

Six electronic databases were searched from the date of inception to August 2021, where the obtained studies were evaluated according to the PRISMA statement. The effects of shunt creation were evaluated by comparing preprocedural to postprocedural or follow-up parameters, expressed as a mean difference of 99% confidence interval. Quality assessment was conducted using the STROBE statement.

RESULTS

Seven studies suited the inclusion criteria which were included in this article. A reduction in upper and lower limb oxygen saturation [Upper limb: St. Mean difference -0.55, 99% CI -1.25 to 0.15; P=0.04; I2=6%. Lower limb: St. Mean difference -4.45, 99% CI -7.37 to -1.52; P<0.00001; I2=65%]. Reversed Potts shunt was shown to improve WHO functional class, 6-minute walk distance, NTpro-BNP level, and hemodynamic parameters including tricuspid annular plane systolic excursion, interventricular septal curvature, and end-diastolic right ventricle/left ventricle ratio.

CONCLUSION

Reversed Potts shunt cannot be said to be relatively safe, although it allows improvement in the clinical and functional status in patients with suprasystemic PAH. Reversed Potts shunt procedure may be the last resort for drug-resistant pulmonary hypertension as it is considered a high-risk procedure performed on patients with extremely poor conditions.

Monitoring and evaluation of the surgical Potts shunt physiology using 4-dimensional flow magnetic resonance imaging

OBJECTIVE

The reversed Potts shunt is an increasingly applied mode of surgical palliation of severe pulmonary hypertension (PH). However, the long-term flow hemodynamic effect of the Potts shunt physiology and desirable long-term hemodynamic end points are not defined. The purpose of this descriptive study was to analyze a series of pediatric patients who underwent surgical Potts shunt as a part of end-stage PH palliation using 4-dimensional (4D)-flow magnetic resonance imaging (MRI) to (1) quantitate the flow through the anastomosis, (2) correlate the shunting pattern with phases of cardiac cycle and PH comorbidities, and (3) describe chronologic changes in shunting pattern.

METHODS

This was a 2-center study evaluating 4 patients seen in the Pulmonary Hypertension Clinic at Children's Hospital Colorado who were evaluated and selected to undergo surgical reverse Potts shunt at Washington University School of Medicine and were serially followed using comprehensive imaging including cardiac MRI and 4D-flow MRI.

RESULTS

After the procedure, each child underwent 2 4D-flow MRI evaluations. Pulmonary pressure offload was evident in all patients, as demonstrated by positive systolic right-to-left flow across the Potts shunt. All patients experienced some degree of the flow reversal, which occurs primarily in diastole. Interventricular dyssynchrony further contributed to flow reversal across the Potts shunt. Lastly, systemic and pulmonary blood mixing in the descending aorta results in secondary helical flow persisting throughout the diastole.

CONCLUSIONS

4D-flow MRI demonstrates that children who have undergone a Potts shunt for severe PH can experience shunt flow reversal. Cumulatively, this left-to-right pulmonary shunt adds to right ventricular volume overload. We speculate that a valved conduit may decrease the left to right shunting and improve overall cardiac output.

Heart failure therapy based on interventricular mechanics and cardio-vascular communications

The heart should not be divided in right and left, whether in health nor in disease. However, the morphological and functional differences between the right and left ventricle should be known and the impact of the ventricle's position considered. Further, the parameters beyond heart rate, contractility, pre- and afterload guaranteeing a sufficient systemic cardiac output have to be integrated in therapeutic measures; preferentially the influence of interventricular mechanics. Despite of recent developments of specific drug therapies, heart failure is associated with a high rate of morbidity and mortality in children. During the progression of heart failure, pulmonary vascular disease is the consequence or the reason for further failing. Clinical symptoms are associated with congestion and low cardiac output at rest or exercise. Improved understanding of the pathophysiological mechanisms particularly of ventricular failure has resulted in the development of innovative therapies that target atrial/ventricular/arterial interactions. Recent advances in interventional and surgical approaches provide promising new strategies to deal with right and left ventricular deterioration. These techniques may delay listing for heart and (heart-) lung transplantation or even make redundant in individual cases. The beneficial effects of these ventricular interaction strategies are mainly based on the mechanics of the interventricular septum and improvement of systolic and diastolic ventricular performance.

Interventional and Surgical Treatments for Pulmonary Arterial Hypertension

Despite significant advancements in pharmacological treatment, interventional and surgical options are still viable treatments for patients with pulmonary arterial hypertension (PAH), particularly idiopathic PAH. Herein, we review the interventional and surgical treatments for PAH. Atrial septostomy and the Potts shunt can be useful bridging tools for lung transplantation (Ltx), which remains the final surgical treatment among patients who are refractory to any other kind of therapy. Veno-arterial extracorporeal membrane oxygenation (V-A ECMO) remains the ultimate bridging therapy for patients with severe PAH. More importantly, VA-ECMO plays a crucial role during Ltx and provides necessary left ventricular conditioning during the initial postoperative period. Pulmonary denervation may potentially be a new way to ensure better transplant-free survival among patients with the aforementioned disease. However, high-quality randomized controlled trials are needed. As established, obtaining the Eisenmenger physiology among patients with severe pulmonary hypertension by creating artificial defects is associated with improved survival. However, right-to-left shunting may be harmful after Ltx. Closure of the artificially created defects may carry some risk associated with cardiac surgery, especially among patients with Potts shunts. In conclusion, PAH requires an interdisciplinary approach using pharmacological, interventional, and surgical modalities.

Advanced Surgical and Percutaneous Approaches to Pulmonary Vascular Disease

Despite progress in modern medical therapy, pulmonary hypertension remains an unremitting disease. Once severe or refractory to medical therapy, advanced percutaneous and surgical interventions can palliate right ventricular overload, bridge to transplantation, and overall extend a patient's course. These approaches include atrial septostomy, Potts shunt, and extracorporeal life support. Bilateral lung transplantation is the ultimate treatment for eligible patients, although the need for suitable lungs continues to outpace availability. Measures such as ex vivo lung perfusion are ongoing to expand donor lung availability, increase rates of transplant, and decrease waitlist mortality.

Pediatric Pulmonary Hypertension: Definitions, Mechanisms, Diagnosis, and Treatment

Pediatric pulmonary hypertension (PPH) is a multifactorial disease with diverse etiologies and presenting features. Pulmonary hypertension (PH), defined as elevated pulmonary artery pressure, is the presenting feature for several pulmonary vascular diseases. It is often a hidden component of other lung diseases, such as cystic fibrosis and bronchopulmonary dysplasia. Alterations in lung development and genetic conditions are an important contributor to pediatric pulmonary hypertensive disease, which is a distinct entity from adult PH. Many of the causes of pediatric PH have prenatal onset with altered lung development due to maternal and fetal conditions. Since lung growth is altered in several conditions that lead to PPH, therapy for PPH includes both pulmonary vasodilators and strategies to restore lung growth. These strategies include optimal alveolar recruitment, maintaining physiologic blood gas tension, nutritional support, and addressing contributing factors, such as airway disease and gastroesophageal reflux. The outcome for infants and children with PH is highly variable and largely dependent on the underlying cause. The best outcomes are for neonates with persistent pulmonary hypertension (PPHN) and reversible lung diseases, while some genetic conditions such as alveolar capillary dysplasia are lethal. © 2021 American Physiological Society. Compr Physiol 11:2135-2190, 2021.

Potts shunt as an effective palliation for patients with end stage pulmonary arterial hypertension

BACKGROUND

Potts shunt has been suggested as an effective palliative therapy for patients with pulmonary artery hypertension (PAH) not associated with congenital heart disease.

MATERIALS AND METHODS

This is a prospective single-center study performed to assess outcomes of Potts shunt in patients with PAH who are in functional class III or IV.

RESULTS

52 patients in functional class III/IV with pulmonary arterial hypertension without significant intra or extracardiac shunt on maximal medical therapy were evaluated and counseled for undergoing Potts shunt/patent ductus arteriosus (PDA) stenting. 16/52 patients (13 females) consented for the procedure; 14 patients underwent surgical creation of Potts, and 2 underwent transcatheter stenting of PDA, which physiologically acted like a Potts shunt. Standard medical therapy was continued in patients who did not consent for the procedure. 12/16 patients survived the procedure. Patients who did not survive the procedure were older, with severe right ventricular systolic dysfunction, and functional class IV. Patients who survived the procedure were followed up in the pulmonary hypertension clinic. The Median follow-up was 17 months (1-40 months). 11/13 patients discharged after the operation showed sustained clinical, echocardiographic, and biochemical improvement, which reduced need for pulmonary vasodilator therapy in 10/13 patients. There was one death in the follow-up period 16 months post-surgery due to lower respiratory tract infection.

CONCLUSION

Potts shunt is feasible in patients with PAH without significant intra or extracardiac shunts. It can be done safely with an acceptable success rate. Patient selection, preoperative stabilization, and meticulous postoperative management are essential. It should be performed at the earliest sign of clinical, echocardiographic, or laboratory deterioation for optimal outcomes. Long-term follow-up is required to see a sustained improvement in functional class and the need for a lung transplant in the future.

Successful Management of an Infant with Atypical Presentation of Alveolar Capillary Dysplasia with Misalignment of the Pulmonary Veins

A newborn infant patient presented with persistent pulmonary hypertension. For right ventricular decompression, the ductus arteriosus was kept open by prostaglandin E ₁ infusion and was stented at the age of 4 weeks during heart catheterization. The child was weaned from mechanical ventilation, since pulmonary functions were adequate. A small atrial septal defect was identified and closed in cardiac catheterization laboratory to decrease preductal hypoxemia. Diagnostic workup led to the diagnosis of alveolar capillary dysplasia with misalignment of the pulmonary veins. Suprasystemic pulmonary arterial hypertension with persisting nitric oxide dependency remained the leading symptoms. The child underwent bilateral lung transplantation at the age of 28 months. He is well at the age of 44 months.

Restrictive atrial communication in right and left heart failure

Heart failure (HF) is usually defined by the dominantly affected heart chamber; therefore, termed right or left HF (RHF or LHF). Pulmonologists understand RHF as a complex syndrome characterized by insufficient delivery of blood from the right ventricle associated with elevated systemic venous pressure at rest or exercise. Cardiologists specify LHF by its clinical functional class and the relation to a reduced (HFrEF), preserved (HFpEF) or mid-range ejection fraction (HFmrEF). Pediatric cardiologist, dealing also with patients with a failing single ventricle, define HF as a condition of insufficient systemic oxygen delivery (DO₂). Certainly, pediatricians do not think of the right and left heart, or even a single ventricle as an isolated, independently acting entity. Because of the importance of cardiac interactions, the creation of a restrictive atrial communication aims at a palliative approach with the goal to diminish the congestive consequences of a dysfunctional ventricle; further to serve as a pop-off valve in order to prevent syncope and cardiovascular collapse. This review covers the background, the particular indications, the techniques and preliminary results achieved following the creation of a restrictive atrial septum defect (rASD) in different pathophysiological settings. Based on the institutional experience, percutaneous trans-catheter perforation of the atrial septum, followed by gradual balloon dilatation can be performed at any age and location worldwide. Medical institutions in low resource countries can make use of such palliating procedures in the setting of right as well as LHF independent of their pharmacological facilities.