Fetoscopic and open transumbilical fetal cardiac catheterization in sheep. Potential approaches for human fetal cardiac intervention

Fetal cardiac intervention-Perspectives from a single center

Fetal cardiac intervention was first proposed in the early 1990s to impact cardiac development and survival of fetuses with fetal aortic stenosis and evolving hypoplastic left heart syndrome (HLHS). Although initial attempts of fetal aortic valvuloplasty were unsuccessful and carried a high rate of morbidity and mortality, our collaborative group at the Brigham and Women's Hospital and Boston Children's Hospital have reinvigorated the procedure using improvements in imaging, anesthesia, balloon catheters, and surgical techniques. Two decades of experience have now allowed us to document the safety of in utero intervention and to achieve a better understanding of the impact of midgestation intervention on developing HLHS. Research into underlying genetics, predictive biomarkers, and ways to incorporate stem cell technology will hopefully allow us to further refine the procedure to most benefit children with this historically lethal disease.

Probing the Electrophysiology of the Developing Heart

Many diseases that result in dysfunction and dysmorphology of the heart originate in the embryo. However, the embryonic heart presents a challenging subject for study: especially challenging is its electrophysiology. Electrophysiological maturation of the embryonic heart without disturbing its physiological function requires the creation and deployment of novel technologies along with the use of classical techniques on a range of animal models. Each tool has its strengths and limitations and has contributed to making key discoveries to expand our understanding of cardiac development. Further progress in understanding the mechanisms that regulate the normal and abnormal development of the electrophysiology of the heart requires integration of this functional information with the more extensively elucidated structural and molecular changes.

Fetal cardiac interventions: myths and facts

An early, primary, in utero cardiac abnormality may prevent normal heart development and cause irreversible secondary structural changes. The idea of foetal cardiac intervention stems from this understanding and focuses on antenatal intervention targeting the primary abnormality to allow normal flow and haemodynamics and thus normal heart development. Crucial aspects of foetal vascular access, varying foetal lie and structural complexity make it very hard to set procedural standards. The procedures are complex and are associated with significant maternal and foetal morbidity and mortality. The high risk-benefit ratio clearly explains the investigational nature of such therapies. With the development of minimally invasive techniques and continued animal experiments, foetal interventional therapy may see a low rate of morbidity and mortality, improving the prognosis of newborns with congenital heart disease previously considered incurable.

Prenatally engineered autologous amniotic fluid stem cell-based heart valves in the fetal circulation

Prenatal heart valve interventions aiming at the early and systematic correction of congenital cardiac malformations represent a promising treatment option in maternal-fetal care. However, definite fetal valve replacements require growing implants adaptive to fetal and postnatal development. The presented study investigates the fetal implantation of prenatally engineered living autologous cell-based heart valves. Autologous amniotic fluid cells (AFCs) were isolated from pregnant sheep between 122 and 128 days of gestation via transuterine sonographic sampling. Stented trileaflet heart valves were fabricated from biodegradable PGA-P4HB composite matrices (n = 9) and seeded with AFCs in vitro. Within the same intervention, tissue engineered heart valves (TEHVs) and unseeded controls were implanted orthotopically into the pulmonary position using an in-utero closed-heart hybrid approach. The transapical valve deployments were successful in all animals with acute survival of 77.8% of fetuses. TEHV in-vivo functionality was assessed using echocardiography as well as angiography. Fetuses were harvested up to 1 week after implantation representing a birth-relevant gestational age. TEHVs showed in vivo functionality with intact valvular integrity and absence of thrombus formation. The presented approach may serve as an experimental basis for future human prenatal cardiac interventions using fully biodegradable autologous cell-based living materials.

Hypoplastic left heart syndrome: current considerations and expectations

In the recent era, no congenital heart defect has undergone a more dramatic change in diagnostic approach, management, and outcomes than hypoplastic left heart syndrome (HLHS). During this time, survival to the age of 5 years (including Fontan) has ranged from 50% to 69%, but current expectations are that 70% of newborns born today with HLHS may reach adulthood. Although the 3-stage treatment approach to HLHS is now well founded, there is significant variation among centers. In this white paper, we present the current state of the art in our understanding and treatment of HLHS during the stages of care: 1) pre-Stage I: fetal and neonatal assessment and management; 2) Stage I: perioperative care, interstage monitoring, and management strategies; 3) Stage II: surgeries; 4) Stage III: Fontan surgery; and 5) long-term follow-up. Issues surrounding the genetics of HLHS, developmental outcomes, and quality of life are addressed in addition to the many other considerations for caring for this group of complex patients.

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.

Impact of intrauterine balloon aortic valvuloplasty on gestational outcome in a fetal goat model

OBJECTIVE

Intrauterine balloon aortic valvuloplasty (IUBAV) has been used to correct critical aortic valve stenosis. Evaluation of the intervention-related risk is necessary. The purpose of this study was to establish an experimental goat model for ultrasound-guided IUBAV intervention and investigate the immediate and long-term effects of IUBAV on the fetus, gestational outcome and mother's safety.

STUDY DESIGN

Fifteen pregnant goats with twin gestation in the 2nd and 3rd trimester were anesthetized to establish the surgical procedure. One fetus of the twins received IUBAV intervention, the other served as a control. The data were collected at three time points: immediately before and after IUBAV, and 24 h after birth. Critical organs including the heart, brain, lung and liver from the fetuses/newborns were collected after IUBAV or 24 h after birth.

RESULTS

IUBAV intervention immediately induced a significant decrease of pH and Ca(2+), as well as an increase of blood glucose and lactic acid levels (p < 0.05). IUBAV also caused an increase in stress hormones (epinephrine 1-fold, norepinephrine 4-fold, and cortisol 1-fold; p < 0.05). Following the operation, all of the mother goats recovered, but in 60% (6/10) preterm delivery occurred. Neither pathological changes in fetal critical organs nor a significant difference in metabolism or growth parameters were detected between IUBAV and control kids.

CONCLUSIONS

Ultrasound-guided IUBAV intervention induced a strong but transient stress response in the operated fetus, which did not result in irreversible histological changes in the fetus or the mother, but may disrupt the continuation of normal gestation in the long term. Preterm delivery is the major risk in this goat IUBAV model.

Engineering of Biologically Active Living Heart Valve Leaflets Using Human Umbilical Cord–Derived Progenitor Cells

This study demonstrates the engineering of biologically active heart valve leaflets using prenatally available human umbilical cord-derived progenitor cells as the only cell source. Wharton's Jelly-derived cells and umbilical cord blood-derived endothelial progenitor cells were subsequently seeded on biodegradable scaffolds and cultured in a biomimetic system under biochemical or mechanical stimulation or both. Depending on the stimulation, leaflets showed mature layered tissue formation with functional endothelia and extracellular matrix production comparable with that of native tissues. This demonstrates the feasibility of heart valve leaflet fabrication from prenatal umbilical cord-derived progenitor cells as a further step in overcoming the lack of living autologous replacements with growth and regeneration potential for the repair of congenital malformation.

Factors affecting technical success of fetal aortic valve dilation

OBJECTIVE

We have reported previously that valve dilation enhances growth of cardiac structures and may prevent hypoplastic left heart syndrome (HLHS) in fetuses with critical aortic stenosis. We aimed to investigate maternal/fetal factors which may affect the technical success of fetal valvuloplasty, and to describe perinatal complications of the procedure.

METHODS

This was a descriptive series of 22 fetuses diagnosed with critical aortic stenosis developing into HLHS which underwent intervention by valvuloplasty. Initially this was attempted using a percutaneous approach; reassessment after our first five attempts, only one of which was successful, led to the introduction of the option of laparotomy. Technical success was defined as balloon inflation across the aortic annulus and a broader jet through the aortic valve as assessed by Doppler. Data collected included body mass index, demographic variables, ultrasound findings and postprocedure interventions.

RESULTS

Technical success increased significantly if maternal laparotomy was an option (83.3% vs. 20.0%, P = 0.017). Laparotomy was performed in 66.6% (12/18) of cases. There was a learning curve that showed an increase in success rate and decrease in need for laparotomy over the 3-year study period. Neither the need for laparotomy nor the chances of technical success were predictable by gestational age, body mass index or placental location. Tocolysis was limited to perioperative prophylaxis; one woman experienced wound infection and fluid overload. Postoperatively, three fetuses died and two delivered prematurely, 2 and 7 weeks after intervention.

CONCLUSION

Fetal aortic valvuloplasty can be performed with technical success, with low fetal loss rate and few maternal complications. While the need for laparotomy cannot be predicted, having it available as an option improves the technical success rate.

Analysis of the stepwise clinical introduction of experimental percutaneous fetoscopic surgical techniques for upcoming minimally invasive fetal cardiac interventions

BACKGROUND

This study assessed the feasibility and safety of surgical techniques developed in sheep for fetoscopic fetal cardiac interventions during three selected less complex procedures for noncardiac fetal conditions in humans. On the basis of this assessment, the implications for the clinical introduction of minimally invasive fetoscopic fetal cardiac interventions in the near future are discussed.

METHODS

The authors performed 16 percutaneous fetoscopic procedures in 13 human fetuses at between 19 + 2 and 34 + 6 weeks of gestation, then analyzed various parameters of surgical relevance for minimally invasive fetoscopic fetal cardiac interventions. Each of the three noncardiac malformations posed typical surgical challenges that will be critical for the technical success of minimally invasive fetoscopic cardiac interventions.

RESULTS

Overall technical success was achieved in 14 of the 16 procedures. Percutaneous fetoscopic surgery did not result in any untoward effects and was well tolerated by all but two pregnant women: one with bleeding complication and one with mild postoperative pulmonary edema. No fetal complications or injuries from the various percutaneous fetoscopic surgical approaches were observed.

CONCLUSIONS

The author's experience with surgical techniques introduced for percutaneous fetoscopic fetal cardiac intervention in selected noncardiac fetal lesions has led them to believe the time has come for the clinical introduction of fetoscopic fetal cardiac interventions. After an adequate learning curve supervised by committees of human research, the overall outcome and quality of postnatal life for the unborn patients ultimately will determine whether fetoscopic or other fetal cardiac interventions will be better therapeutic alternatives to currently available postnatal procedures.

Fetal interventions for cardiac defects

This article focuses on the current status of in utero catheter interventions for congenital heart disease. The discussion of fetal interventions for cardiac defects briefly reviews the evolution of approaches to congenital heart disease and issues surrounding the prenatal detection of cardiac defects, the rationale for fetal intervention, and optional candidates for the procedures. Finally, the technical aspects and procedural considerations are reviewed.

Amniotic air insufflation during minimally invasive fetoscopic fetal cardiac interventions is safe for the fetal brain in sheep

BACKGROUND

Amniotic air insufflation during experimental fetoscopic fetal cardiac interventions greatly improves the visualization of intra-amniotic contents. The purpose of this study was to assess any histologically discernible effects from this approach on the fetal brain after short-term studies and long-term survival in sheep.

METHODS

Thirty pregnant ewes between 80 and 110 days of gestation underwent amniotic air insufflation during various fetoscopic fetal cardiac interventions. After 18 short-term and 12 long-term studies, the brains of the operated fetuses and-if available-their unoperated siblings were examined for hemorrhage, embolism, infarctions, inflammatory changes, and abnormal cortical maturation.

RESULTS

Amniotic air insufflation during minimally invasive fetoscopic fetal cardiac interventions did not result in any histologically discernible damage to the brain in short-term and long-term studies in any but 2 sibling sheep. In the 2 affected siblings, a small area of chronic cortical frontal lobe infarction was observed after long-term survival.

CONCLUSIONS

Amniotic air insufflation during minimally invasive percutaneous fetoscopic fetal cardiac interventions is safe for the fetal brain and does not compromise maternal hemodynamics in sheep. These findings encourage further investigation of the role this technique might play during fetoscopic fetal cardiac interventions in humans.

Fetoscopic surgery: where are we today?

PURPOSE OF REVIEW

Since the early 1990s, advances in endoscopic equipment and the commercial availability of micro-catheters, mini-balloons, tiny laser fibers and other ingenious tools have set the trend toward the development of minimally invasive fetoscopic surgical techniques for the treatment of some congenital malformations that progress in severity over the course of gestation and may destroy entire organ systems of the unborn. The purpose of this review is to provide a state-of-the-art overview of these new procedures for the anesthesiologist.

RECENT FINDINGS

Procedures like diagnostic fetoscopies, laser coagulation of inter-twin placental vascular connections in twin-twin transfusion syndrome, fetal tracheal balloon occlusion in diaphragmatic hernia, laser perforation of posterior urethral valves, vocal cord division in congenital high-airway obstruction syndrome and most recently even coverage of spina bifida aperta can be performed entirely percutaneously using minimally invasive fetoscopic techniques. Careful selection of anesthetic methods and intensive maternal monitoring by the anesthesiology team are paramount to the success of these procedures, particularly in hemodynamically unstable fetuses or procedures that employ gas insufflation of the amniotic cavity.

SUMMARY

An increasing spectrum of congenital malformations can be treated by fetoscopic surgery. Compared to open fetal surgery, fetoscopic surgery results in significantly less maternal trauma. Like the open procedures, the efficacy of the fetoscopic procedures to improve fetal outcome over postnatal treatment strategies will have to be assessed in further studies under close supervision of committees for human research.

New fetal cardiac imaging techniques

Rapid advances in graphics computing and micro-engineering have offered new techniques for prenatal cardiac imaging. Some of them can be non-invasively applied to both clinical and laboratory settings, including dynamic three-dimensional echocardiography, myocardial Doppler imaging, harmonic ultrasound imaging, and B-flow sonography. With clinical constraints, a few others have been mainly used in laboratories, such as endoscopic ultrasound, magnetic resonance imaging and biomicroscopy. Appropriate use and co-use of these new tools will not only provide unique information for better clinical assessment of fetal cardiac disease but also offer new ways to improved understanding of cardiovascular development and pathogenesis.

Balloon valvuloplasty for congenital heart disease in the fetus

Fetal cardiac interventions are relatively new and promising therapeutic options for modifying CHD in utero. Techniques for safe access to the fetus must be improved and patient selection criteria must be developed. Most important is early detection and referral of all patients who have CHD, enabling improved outcomes for infants. Finally, it should be stressed that performing successful fetal cardiac interventions requires multidisciplinary collaboration between perinatologists, cardiologists, fetal surgeons, and anesthesiologists. Each discipline has specific skills for providing safe access to the fetus, performing the procedure, and providing perioperative care.

Intra-amniotic multimodal fetal echocardiography in sheep: a novel imaging approach during fetoscopic interventions and for assessment of high-risk pregnancies in which conventional imaging methods fail

During fetoscopic interventions, intraesophageal placement of intravascular ultrasound (US) catheters for fetal hemodynamic monitoring may result in esophageal injury in very small fetuses. Moreover, conventional fetal imaging by the transvaginal or transabdominal routes may be impossible in some high-risk pregnancies. The purpose of our study in sheep was to assess the potential of a phased-array intravascular US catheter for intra-amniotic fetal echocardiography. The catheter was percutaneously inserted into the amniotic cavity in seven pregnant ewes at between 78 to 98 days of gestation and permitted high-quality 2-D imaging of the fetal heart and multimodal Doppler assessment of fetal cardiovascular flows. Fetoscopic examination of intra-amniotic contents after intra-amniotic imaging was finished did not display any injury to intra-amniotic contents. The intra-amniotic imaging approach may provide an effective alternative in humans for monitoring during fetoscopic interventions, and to assess fetal anatomy and hemodynamics in high-risk pregnancies when sufficient images cannot be obtained by conventional routes.

Fetal cardiology

A systematic approach to examination of the fetal heart will enhance the detection of structural cardiac abnormalities and will enable an accurate diagnosis of congenital heart disease to be made. Once an abnormality has been detected appropriate counselling must be provided and adequate support given to the parents. Associated extracardiac abnormalities should be sought for, and plans for the remainder of pregnancy, delivery and postnatal management should be made using a team approach. In cases resulting in termination of pregnancy, permission for autopsy should be sought to confirm the ultrasound diagnosis. Although in-utero therapy is available for some forms of fetal arrhythmia and a few limited cases of structural heart disease, this should be conducted in tertiary centres.

Pediatric cardiac intensive care: current state of the art and beyond the millennium

Pediatric cardiac intensive care has emerged as a distinct clinical entity to meet the unique needs of pediatric patients with congenital and acquired heart disease. This new subspecialty demands expertise and experience in the pediatric subspecialties of cardiology, intensive care, cardiac surgery, cardiac anesthesia, neonatology, and others. Ten recent developments will have an impact on pediatric cardiac intensive care for the coming decades: 1) emergence of new patient populations; 2) new clinical methodologies in the treatment of pulmonary hypertension; 3) innovations in techniques of respiratory support; 4) expanding research of single ventricle physiology; 5) advances in the treatment of heart failure; 6) improved noninvasive imaging; 7) new directions in interventional cardiac catheterization; 8) new techniques in pediatric cardiac surgery; 9) use of computer technology and intensive care monitoring; and 10) appreciation for global economics of intensive care. Finally, a multidisciplinary approach with a team esprit de corps remains vital to a successful pediatric cardiac intensive care program.

World experience of percutaneous ultrasound-guided balloon valvuloplasty in human fetuses with severe aortic valve obstruction

Prenatal alleviation of severe fetal aortic valve obstructions by percutaneous ultrasound-guided balloon valvuloplasty has been performed to improve the fate of affected fetuses. The purpose of this study was to analyze the current world experience of these procedures in human fetuses. Data from 12 human fetuses were available for analysis. The mean gestational age at intervention was 29.2 weeks (range 27 to 33). The mean time period between initial presentation and intervention was 3.3 weeks (range 3 days to 9 weeks). Technically successful balloon valvuloplasties were achieved in 7 fetuses, none of whom had an atretic valve. Only 1 of these fetuses remains alive today. Of the 5 remaining technical failures, 1 patient with severe aortic stenosis underwent successful postnatal intervention and remains alive. Six patients who survived prenatal intervention died from cardiac dysfunction or at surgery in the first days or weeks after delivery. Four fetuses died early within 24 hours after the procedure, 1 from a bleeding complication, 2 from persistent bradycardias, and 1 at valvotomy after emergency delivery. Thus, the early clinical experience of percutaneous ultrasound-guided fetal balloon valvuloplasty in human fetuses with severe aortic valve obstruction has been poor due to selection of severe cases, technical problems during the procedure, and high postnatal operative mortality in fetuses who survived gestation. Improved patient selection and technical modifications in interventional methods may hold promise to improve outcome in future cases.

Fetal transesophageal echocardiography utilizing a 10-F, 10-MHz intravascular ultrasound catheter--comparison with conventional maternal transabdominal fetal echocardiography in sheep

The purpose of our study in fetal sheep was to assess the measurement agreement between fetal transesophageal echocardiography (FTEE) and conventional maternal transabdominal echocardiography (CMTFE) by the Bland-Altman method. We performed our study in 11 fetal sheep between 95-103 days of gestation (term = 145 days). FTEE was performed by imaging the fetal heart in horizontal planes utilizing a 10-F, 10-MHz intravascular ultrasound catheter. CMTFE was carried out using a 5.0-MHz phased-array transducer replicating the FTEE imaging planes. We found close agreement between FTEE and CMTFE measurements of great vessel and cardiac valvar dimensions. Conversely, the variability between both techniques for measuring ventricular dimensions was inadequate. We conclude that FTEE permits measurement of great vessel and cardiac valve dimensions with high agreement with CMTFE measurements. This finding strengthens the applicability of FTEE as a monitoring tool during experimental open or fetoscopic fetal cardiac interventions.

Prenatal diagnosis of right ventricular outflow tract obstruction with intact ventricular septum, and detection of ventriculocoronary connections

OBJECTIVES

To determine the accuracy of prenatal diagnosis of pulmonary atresia and intact ventricular septum (PAIVS), and pulmonary stenosis, including prenatal detection of ventriculocoronary connections, to evaluate heart size during the prenatal period, and to evaluate the outcome.

DESIGN AND PATIENTS

Medical records of 20 cases with prenatally diagnosed PAIVS and pulmonary stenosis were reviewed retrospectively. Prenatal and postnatal echocardiography were also reviewed and dimensions of the ventricles and vessels were measured retrespectively.

RESULTS

Of 20 prenatal diagnoses (15 PAIVS and five pulmonary stenosis), 16 were confirmed as correct. One critical pulmonary stenosis case had been diagnosed as PAIVS prenatally; three had no confirmation. Eight pregnancies were terminated, three had no active treatment, and nine were treated; all survived. Of 13 assessed with ventriculocoronary connections prenatally, seven were diagnosed correctly (four with, three without ventriculocoronary connections), but one was falsely positive; five had no confirmation. The more prominent hypoplasia of the main pulmonary artery and the tricuspid valve annulus, and the sigmoid shape of the ductus arteriosus, seemed to be associated with the presence of ventriculocoronary connections.

CONCLUSIONS

Current prenatal echocardiography can accurately diagnose right ventricular outflow tract obstruction and ventriculocoronary connections. Prenatal detection of this constellation of abnormalities aids in family counselling and decisions on postnatal management.

Evaluation and management of pulmonary atresia with intact ventricular septum

Pulmonary atresia with intact ventricular septum (PA/IVS) is a spectrum of diseases with varying severity of right ventricle hypoplasia and potential for biventricular, univentricular, or hybrid repairs. Pessimistic outcome measures for PA/IVS may give way to optimism with the refinement of early diagnosis and early intervention to encourage right ventricle flow and optimize growth. To this end, PA/IVS has become a focus of innovative interventions (e.g., fetal surgery) and new catheter-based and surgical techniques.