Percutaneous ultrasound-guided stenting of the atrial septum in fetal sheep

Fetal Hypoplastic Left Heart Syndrome with Intact Atrial Septum: From Successful in utero Stenting to Subtotal Stent Occlusion - A Case Report

INTRODUCTION

Fetuses with hypoplastic left heart syndrome (HLHS) and intact atrial septum (IAS) have an overall poor prognosis and a high risk of neonatal death due to severe secondary lung damage. Intrauterine stenting of the atrial septum was introduced in these patients to enable survival.

CASE PRESENTATION

We present a case of a HLHS fetus with IAS and signs of incipient nutmeg lung, in whom at 30 weeks gestation an atrial stent was successfully placed but continuously developed subtotal stent-obstruction over the next weeks.

CONCLUSION

Continuous obstruction of placed atrial septum stents until delivery is possible and requires close monitoring of successfully treated fetuses.

Hypoplastic Left Heart Syndrome: Is There a Role for Fetal Therapy?

During fetal life some cardiac defects may lead to diminished left heart growth and to the evolution of a form of hypoplastic left heart syndrome (HLHS). In fetuses with an established HLHS, severe restriction or premature closure of the atrial septum leads to left atrial hypertension and remodeling of the pulmonary vasculature, severely worsening an already poor prognosis. Fetal therapy, including invasive fetal cardiac interventions and non-invasive maternal hyperoxygenation, have been introduced to prevent a possible progression of left heart hypoplasia, improve postnatal outcome, or secure fetal survival. The aim of this review is to cover patient selection and possible hemodynamic effects of fetal cardiac procedures and maternal hyperoxygenation in fetuses with an evolving or established hypoplastic left heart syndrome.

Mending a broken heart: In vitro, in vivo and in silico models of congenital heart disease

Birth defects contribute to ∼0.3% of global infant mortality in the first month of life, and congenital heart disease (CHD) is the most common birth defect among newborns worldwide. Despite the significant impact on human health, most treatments available for this heterogenous group of disorders are palliative at best. For this reason, the complex process of cardiogenesis, governed by multiple interlinked and dose-dependent pathways, is well investigated. Tissue, animal and, more recently, computerized models of the developing heart have facilitated important discoveries that are helping us to understand the genetic, epigenetic and mechanobiological contributors to CHD aetiology. In this Review, we discuss the strengths and limitations of different models of normal and abnormal cardiogenesis, ranging from single-cell systems and 3D cardiac organoids, to small and large animals and organ-level computational models. These investigative tools have revealed a diversity of pathogenic mechanisms that contribute to CHD, including genetic pathways, epigenetic regulators and shear wall stresses, paving the way for new strategies for screening and non-surgical treatment of CHD. As we discuss in this Review, one of the most-valuable advances in recent years has been the creation of highly personalized platforms with which to study individual diseases in clinically relevant settings.

An Overview of Contemporary Outcomes in Fetal Cardiac Intervention: A Case for High-Volume Superspecialization?

Fetal cardiac interventions (FCI) offer the opportunity to rescue a fetus at risk of intrauterine death, or more ambitiously to alter disease progression. Most of these fetuses require multiple additional postnatal procedures, and it is difficult to disentangle the effect of the fetal procedure from that of the postnatal management sequence. The true clinical impact of FCI may only be discernible in large-volume institutions that can commit to a standardized postnatal approach and have sufficient case volume to overcome their FCI learning curve.

Fetal Cardiac Intervention in Critical Aortic Stenosis with Severe Mitral Regurgitation, Severe Left Atrial Enlargement, and Restrictive Foramen Ovale

OBJECTIVE

To assess the intrauterine course and outcome of fetal cardiac intervention (FCI) in fetuses with critical aortic stenosis (CAS), severe mitral regurgitation (MR), severe left atrial dilatation (LAD), and restrictive foramen ovale (RFO) or intact atrial septum.

METHODS

All fetuses with a prenatal diagnosis of CAS, severe MR, severe LAD, and RFO were retrospectively collected in one tertiary center for fetal medicine over a period of 10 years. Video recordings, pre- and postnatal charts were reviewed for cardiac and extracardiac anomalies, intrauterine course, and postnatal outcome.

RESULTS

Nineteen fetuses with CAS, severe MR, severe LAD, and RFO were diagnosed in the study period. In 5 cases, FCI was not considered as the parents either opted for expectative management or for termination. In the remaining 14 fetuses, 21 FCI were performed: 14 balloon valvuloplasties, 2 atrioseptostomies, and 5 fetal atrial stent insertions. Seven of 14 fetuses (50%) had fetal hydrops, 5 of 14 fetuses (36%) presented with intact atrial septum. Procedure-related death occurred in 5 fetuses after aortic valvuloplasty or concomitant atrioseptostomy but in none after fetal atrial stenting. Due to progressive hydrops, two terminations of pregnancy were performed. Among the 7 live births, 3 died in the neonatal period. The remaining 4 received single ventricle palliation, 2 following fetal aortic valvuloplasty and 2 after fetal atrial stent insertion.

CONCLUSIONS

CAS with severe MR, severe LAD, and RFO has a high overall mortality even in cases undergoing intrauterine intervention. Parameters that accurately predict the intrauterine and postnatal outcome have yet to be defined.

Fetal cardiac interventions: clinical and experimental research

Fetal cardiac interventions for congenital heart diseases may alleviate heart dysfunction, prevent them evolving into hypoplastic left heart syndrome, achieve biventricular outcome and improve fetal survival. Candidates for clinical fetal cardiac interventions are now restricted to cases of critical aortic valve stenosis with evolving hypoplastic left heart syndrome, pulmonary atresia with an intact ventricular septum and evolving hypoplastic right heart syndrome, and hypoplastic left heart syndrome with an intact or highly restrictive atrial septum as well as fetal heart block. The therapeutic options are advocated as prenatal aortic valvuloplasty, pulmonary valvuloplasty, creation of interatrial communication and fetal cardiac pacing. Experimental research on fetal cardiac intervention involves technical modifications of catheter-based cardiac clinical interventions and open fetal cardiac bypass that cannot be applied in human fetuses for the time being. Clinical fetal cardiac interventions are plausible for midgestation fetuses with the above-mentioned congenital heart defects. The technical success, biventricular outcome and fetal survival are continuously being improved in the conditions of the sophisticated multidisciplinary team, equipment, techniques and postnatal care. Experimental research is laying the foundations and may open new fields for catheter-based clinical techniques. In the present article, the clinical therapeutic options and experimental fetal cardiac interventions are described.

Fetal cardiac interventions

The present article aims to highlight fetal cardiac interventions (FCIs) in terms of indications, strategies, and fetal prognoses. FCIs of the early years were predominantly pharmacological therapies for fetal arrhythmia or heart block. A transplacental transmission of therapeutic agents has now become the main route of pharmacological FCIs. There have been various FCI strategies, which can be categorized into three types: pharmacological, open FCIs, and closed FCIs. Rather than as a routine management for materno-fetal cardiac disorders, however, FCIs are only applied in those fetal cardiac disorders that are at an increased risk of mortality and morbidity and warrant an interventional therapy. Pharmacological FCIs have been well applied in fetal arrhythmias but require further investigations for novel therapeutic agents. The development of open FCI in humans is an issue for the long run. Closed FCIs may largely rely on advanced imaging techniques. Hybrid FCIs might be the future goal in the treatment of fetal heart diseases.

Percutaneous Fetal Cardiac Catheterization Technique for Stenting the Foramen Ovale in a Midgestation Lamb Model

Background—

Intact or highly restricted intra-atrial septum can be reliably diagnosed in the human fetus as early as 22 to 24 weeks of gestation. Fetal interventions targeting the atrial septum have used a direct approach through the atrial wall. Here, we report stenting of the foramen ovale with a large, open-cell stent via percutaneous access through the fetal hepatic vein in a sheep model.

Methods and Results—

In 5 fetal sheep of 109 to 111 days of gestation (term, 147 days), the fetal hepatic vein was punctured percutaneously under ultrasound guidance and a 13.3-cm 14-gauge intravenous catheter was inserted. After catheterization of the inferior vena cava, right atrium, foramen ovale, and left atrium with a guidewire and 1.8F to 2.6F tapered catheter, a self-expandable, 8×12-mm flexible open-cell stent was positioned in an unrestricted foramen ovale. Flow and fetal well-being were documented for 45 minutes after the procedure. Access to the left atrium was achieved in all 5 animals and all survived. In 4 animals, the stent was successfully positioned in the foramen ovale. One fetus was born at term and euthanized on day 3: postmortem examination confirmed the patency of the stent. The other 3 fetuses were well after being monitored by ultrasound for 45 minutes. In 1 animal, the stent dislodged immediately after release obstructing the mitral valve. This fetus developed ascites and was euthanized after 4 days.

Conclusions—

It is feasible to safely advance a large diameter, self-expandable, open-cell design stent into the fetal atrial septum via a percutaneous access route through the fetal hepatic vein.

Foetal therapy: what works? Closed interatrial septum

Hypoplastic left-heart syndrome and critical aortic stenosis with severely restricted or intact foramen ovale are associated with high neonatal mortality and poor long-term outcome. Despite accurate foetal diagnosis and successful postnatal catheter-based and surgical intervention, the 1-month survival rate is about 33%. Changes in pulmonary vascular architecture resulting in pulmonary hypertension result in important long-term morbidity. Prenatal relief of left atrial and pulmonary hypertension may promote normal pulmonary vascular and parenchymal development and improve short- and long-term outcomes. Foetal atrial balloon septostomy, laser perforation, and stenting of the foetal interatrial septum are the current options for foetal therapy. This paper provides an overview of foetal diagnosis, selection of patients for foetal intervention, and interventional techniques, and also reviews the current status of foetal and postnatal outcomes after intrauterine intervention.

Fetal trans-apical stent delivery into the pulmonary artery: prospects for prenatal heart-valve implantation

OBJECTIVE

The purpose of this study was to assess the technical feasibility of a fetal trans-apical stent delivery into the pulmonary artery using a novel hybrid-intervention technique as a possible route for prenatal minimally invasive heart-valve-implantation approaches.

METHODS

Pregnant Pre-Alp sheep between 122 and 128 days' gestation (n = 3) underwent a midline laparotomy. The fetus was left in utero or partially externalized and its chest was opened via a left-sided minithoracotomy. The fetal heart was cannulated and a guide wire was introduced through the ductus arteriosus into the aorta. A 14-French delivery system was then mounted onto the guide wire and advanced to the landing zone in the pulmonary artery, where the stent was deployed. The position of the stent was confirmed using echocardiography, angiography as well as computed tomography.

RESULTS

The trans-apical implantation was successful in all animals. However, at necropsy in one animal, the stent was found to partly occlude one of the pulmonary valvular leaflets. Bleeding at the antero-apical incision occurred in all animals but could be managed without fetal demise. No fetal cardiopulmonary bypass was performed. In all animals, contrast angiography displayed normal perfusion of the pulmonary vasculature as well as the ductus arteriosus.

CONCLUSIONS

Our study demonstrates the principal technical feasibility of a prenatal stent delivery into the pulmonary artery using a novel trans-apical hybrid-intervention technique. This approach demonstrates the first step towards possible future minimally invasive prenatal heart-valve-implantation procedures.

Benign outcome of pulmonary hypertension in neonates with a restrictive patent foramen ovale versus result for neonates with an unrestrictive patent foramen ovale

Premature closure or restriction of foramen ovale (FO) is a rare but known entity. FO diameter <2 mm and Doppler velocity >120 cm/s, diameter <3 mm with Doppler velocity measured gradient >5 mmHg have all being used by various authors to describe this entity. Some neonates with restrictive FO have been noted to have severe pulmonary hypertension with no clinical signs or symptoms and with spontaneous resolution without any intervention. Seven consecutive neonates were indentified in the database between 01/01/2003 and 06/30/2010 with diagnosis of restrictive PFO (diameter <2 mm) with structurally normal heart and their initial and follow-up echocardiogram as well as hospital medical records were reviewed. As a control, seven neonates with diagnosis of pulmonary hypertension and respiratory distress syndrome or meconium aspiration syndrome were randomly selected. Eighty-six percent of the patients in the control group were symptomatic and required treatment as compared to 14% in the restrictive FO group (p = 0.03). Further, the fall in the peak instantaneous pulmonary artery pressure on follow-up echocardiogram was greater in the restrictive FO group compared with the non-restrictive group (p = 0.03). Patients with pulmonary hypertension and a restrictive FO with no other associated congenital heart disease and/or lung pathology behave differently when compared to neonates with non-restrictive FO and pulmonary hypertension with associated lung disease. They seldom manifest symptoms requiring intervention and tend to show a faster drop in their pulmonary artery pressure toward the normal.

The role of fetal echocardiography in fetal intervention: a symbiotic relationship

In this review, the authors explore the role of noninvasive and invasive fetal interventions in fetal cardiovascular disease guided by observations at fetal echocardiography. They first review fetal cardiac lesions that may be ameliorated by fetal intervention and then review noncardiac fetal pathologic findings for which fetal echocardiography can provide important insight into the pathophysiology and aid in patient selection for and timing of intervention and postintervention surveillance.