In utero pacing for fetal congenital heart block

Pacemaker Management and In-Hospital Outcomes in Neonatal Congenital Atrioventricular Block

BACKGROUND

Neonatal congenital atrioventricular block (nCAVB) is rare, causes bradycardia, confers high mortality, and frequently requires pacing. In-hospital outcomes and pacemaker management in nCAVB are limited.

OBJECTIVES

The purpose of this study was to analyze pacing and outcomes of nCAVB with and without congenital heart disease (CHD) using a multicenter database.

METHODS

A Pediatric Health Information System database review from January 1, 2004, to June 30, 2022. Patients <31 days of age with a nCAVB International Classification of Diseases-9th/10th Revision diagnosis code and no cardiac surgeries except pacemaker were included. Pacing and in-hospital mortality were analyzed using univariate and multivariable logistic statistics and competing risk and event-free survival models.

RESULTS

Of 1,146 patients with nCAVB, 659 (57.5%) were girls and 506 (44.2%) were premature. Among the 326 (28.4%) with CHD, 134 (41.1%) underwent pacemaker insertion as initial intervention and 56 (17.2%) had temporary pacing wires. In-hospital mortality occurred in 118 (36.2%), with increased adjusted odds with temporary pacing wires placed at 0 to 1 or 2 to 7 days of age relative to no wires, and with decreased odds among pacemakers placed at 2 to 7 or 8+ days of age relative to no pacemaker. Of 820 (71.6%) without CHD, 334 (40.7%) underwent pacemaker insertion as the initial intervention and 81 (9.9%) had temporary pacing wires. In-hospital mortality occurred in 69 (8.4%) with increased adjusted odds in prematurity and decreased odds among pacemaker placement at 2 to 7 days of age relative to no pacemaker.

CONCLUSIONS

Over 18.5 years, in-hospital mortality occurred in 36.2% of nCAVB patients with CHD and 8.4% with non-CHD. Associations with increased in-hospital mortality included CHD and prematurity and decreased with pacemaker placement. Prospective registries are needed to better characterize and standardize management of this rare but high-mortality disease.

Toward Eliminating Perinatal Comfort Care for Prenatally Diagnosed Severe Congenital Heart Defects: A Vision

Over the past 40 years, the medical and surgical management of congenital heart disease has advanced considerably. However, substantial room for improvement remains for certain lesions that have high rates of morbidity and mortality. Although most congenital cardiac conditions are well tolerated during fetal development, certain abnormalities progress in severity over the course of gestation and impair the development of other organs, such as the lungs or airways. It follows that intervention during gestation could potentially slow or reverse elements of disease progression and improve prognosis for certain congenital heart defects. In this review, we detail specific congenital cardiac lesions that may benefit from fetal intervention, some of which already have documented improved outcomes with fetal interventions, and the state-of-the-science in each of these areas. This review includes the most relevant studies from a PubMed database search from 1970 to the present using key words such as fetal cardiac, fetal intervention, fetal surgery, and EXIT procedure. Fetal intervention in congenital cardiac surgery is an exciting frontier that promises further improvement in congenital heart disease outcomes. When fetuses who can benefit from fetal intervention are identified and appropriately referred to centers of excellence in this area, patient care will improve.

Current perspective and scope of fetal therapy: part 1

Fetal therapy term has been described for any therapeutic intervention either invasive or noninvasive for the purpose of correcting or treating any fetal malformation or condition. Fetal therapy is a rapidly evolving specialty and has gained pace in last two decades and now fetal intervention is being tried in many malformations with rate of success varying with the type of different fetal conditions. The advances in imaging techniques have allowed fetal medicine persons to make earlier and accurate diagnosis of numerous fetal anomalies. Still many fetal anomalies are managed postnatally because the fetal outcomes have not changed significantly with the use of fetal therapy and this approach avoids unnecessary maternal risk secondary to inutero intervention. The short-term maternal risk associated with fetal surgery includes preterm labor, premature rupture of membranes, uterine wall bleeding, chorioamniotic separation, placental abruption, chorioamnionitis, and anesthesia risk. Whereas, maternal long-term complications include risk of infertility, uterine rupture, and need for cesarean section in future pregnancies. The decision for invasive fetal therapy should be taken after discussion with parents about the various aspects like postnatal fetal outcome without fetal intervention, possible outcome if the fetal intervention is done, available postnatal intervention for the fetal condition, and possible short-term and long-term maternal complications. The center where fetal intervention is done should have facility of multi-disciplinary team to manage both maternal and fetal complications. The major issues in the development of fetal surgery include selection of patient for intervention, crafting effective fetal surgical skills, requirement of regular fetal and uterine monitoring, effective tocolysis, and minimizing fetal and maternal fetal risks. This review will cover the surgical or invasive aspect of fetal therapy with available evidence and will highlight the progress made in the management of fetal malformations in last two decades.

Diagnosis and Management of Fetal Autoimmune Atrioventricular Block

Autoimmune congenital atrioventricular block (CAVB) has been extensively studied in recent decades. The American Heart Association published guidelines for monitoring pregnant women with anti-Ro/Sjögren’s syndrome antigen A (SSA) or anti-La/Sjögren’s syndrome antigen B (SSB) autoantibodies, which are considered to increase the risk of CAVB. Information about the natural history of the disease in utero has contributed to the detection of fetuses with CAVB in the treatable stage. Hydroxychloroquine (HCQ) may be used to prevent CAVB. The lack of large randomized control trials is a major drawback to fully confirm the benefits of fluorinated steroids such as dexamethasone. Although, when combined with a β-sympathomimetic agent, the outcome of administering a fluorinated steroid in complete CAVB is still controversial. Novel treatments targeting the immunological process might prevent the recurrence of CAVB in pregnant women with previously affected children.

Fetal arrhythmias: prenatal evaluation and intrauterine therapeutics

Introduction

Fetal arrhythmias are a common phenomenon with rather complicated etiologies. Debates remain regarding prenatal diagnosis and treatment of fetal arrhythmias.

Methods

The literature reporting on prenatal diagnosis and treatment of fetal arrhythmias published in the recent two decades were retrieved, collected and analyzed.

Results

Both fetal magnetocardiogram and electrocardiogram provide information of cardiac time intervals, including the QRS and QT durations. M-mode ultrasound detects the AV and VA intervals, fetal heart rate, and AV conduction. By using Doppler ultrasound, simultaneous recording of the atrial and ventricular waves can be obtained. Benign fetal arrhythmias, including premature contractions and sinus tachycardia, do not need any treatment before and after birth. Sustained fetal arrhythmias that predispose to the occurrence of hydrops fetalis, cardiac dysfunction or eventual fetal demise require active treatments. Intrauterine therapy of fetal tachyarrhythmias has been carried out by the transplacental route. If maternal transplacental treatment fails, intraumbilical, intraperitoneal, or direct fetal intramuscular injection of antiarrhythmic agents can be attempted.

Conclusions

The outcomes of intrauterine therapy of fetal tachyarrhythmias depend on the types or etiology of fetal arrhythmias and fetal conditions. Most are curable to a transplacental treatment by the first-line antiarrhythmic agents. Fetal cardiac pacings are effective methods to restore sinus rhythm in drug-resistant or hemodynamically compromised cases. Immediate postnatal pacemaker implantation is warranted in refractory cases.

Prenatal diagnosis and management of congenital complete heart block

Congenital complete heart block (CCHB) is a life-threatening medical condition in the unborn fetus with insufficiently validated prenatal interventions. Maternal administration of medications aimed at decreasing the immune response in the fetus and beta-agonists intended to increase fetal cardiac output have shown only marginal benefits. Anti-inflammatory therapies cannot reverse CCHB, but may decrease myocarditis and improve heart function. Advances in prenatal diagnosis and use of strict surveillance protocols for delivery timing have demonstrated small improvements in morbidity and mortality. Ambulatory surveillance programs and wearable fetal heart rate monitors may afford early identification of evolving fetal heart block allowing for emergent treatment. There is also preliminary data suggesting a roll for prevention of CCHB with hydroxychloroquine, but the efficacy and safety is still being studied. To date, intrauterine fetal pacing has not been successful due to the high-risk invasive placement techniques and potential problems with lead dislodgement. The development of a fully implantable micropacemaker via a minimally invasive approach has the potential to pace fetal patients with CCHB and thus delay delivery and allow fetal hydrops to resolve. The challenge remains to establish accepted prenatal interventions capable of successfully managing CCHB in utero until postnatal pacemaker placement is successfully achieved.

In utero intervention for severe congenital heart disease

The aim of foetal cardiac therapy is to treat an abnormality at the developmental stage so that the process of cardiac growth, which is complex and relies on the volume and direction of circulating blood as well as genetic determinants, can continue. In reality, most cardiac interventions are palliative; hence, major abnormalities are still present at birth. Nevertheless, tangible benefits following successful foetal intervention include improved haemodynamics and reduction in secondary damage leading to better postnatal outcomes. In cases of semilunar valve stenosis, or atresia, foetal valvuloplasty aims to achieve a biventricular, rather than univentricular, circulation. Opening and stenting a restrictive atrial foramen may preserve the pulmonary function in cases of hypoplastic left heart syndrome, thereby increasing the chances of successful postnatal surgery. More recent endeavours include percutaneous implantation of a miniaturised pacemaker to treat complete heart block and the promotion of left-sided heart growth by chronic maternal hyperoxygenation. The true clinical benefit of these interventions over natural history remains uncertain because of the paucity of appropriate randomised controlled trials (RCTs). Foetal cardiac therapy must now move from a pioneering approach to one that is supported by evidence, as has been done successfully for other foetal therapies.

Prenatal therapy for fetal cardiac disorders

Fetal cardiac abnormalities are some of the commonest congenital disorders seen in prenatal life. They can be anatomical or functional and can develop de novo or as a consequence of either maternal or fetal disease. Untreated, morbidity and mortality rates are high for hypoplastic left heart disorders and for some fetal tachy and bradyarrhythmias. Optimum management strategies are often not clear because of the lack of knowledge about the precise natural history of some of these conditions. Prenatal therapy ranges from invasive fetal cardiac intervention to maternal administration of drugs for transplacental transfer to the fetus. This comprehensive review covers many fetal cardiac disorders and various prenatal therapeutic options that are available.

Design and Testing of a Transcutaneous RF Recharging System for a Fetal Micropacemaker

We have developed a rechargeable fetal micropacemaker in order to treat severe fetal bradycardia with comorbid hydrops fetalis. The necessarily small form factor of the device, small patient population, and fetal anatomy put unique constraints on the design of the recharging system. To overcome these constraints, a custom high power field generator was built and the recharging process was controlled by utilizing pacing rate as a measure of battery state, a feature of the relaxation oscillator used to generate stimuli. The design and in vitro and in vivo verification of the recharging system is presented here, showing successful generation of recharging current in a fetal lamb model.

Minimally invasive implantable fetal micropacemaker: mechanical testing and technical refinements

This paper discusses the technical and safety requirements for cardiac pacing of a human fetus with heart failure and hydrops fetalis secondary to complete heart block. Engineering strategies to meet specific technical requirements were integrated into a systematic design and implementation consisting of a novel fetal micropacemaker, a percutaneous implantation system, and a sterile package that enables device storage and recharging maintenance in a clinical setting. We further analyzed observed problems on myocardial fixation and pacing lead fatigue previously reported in earlier preclinical trials. This paper describes the technical refinements of the implantable fetal micropacemaker to overcome these challenges. The mechanical performance has been extensively tested to verify the improvement of reliability and safety margins of the implantation system.

A novel method to estimate safety factor of capture by a fetal micropacemaker

We have developed a rechargeable fetal micropacemaker in order to treat severe fetal bradycardia with comorbid hydrops fetalis, a life-threatening condition in pre-term non-viable fetuses for which there are no effective treatment options. The small size and minimally invasive form factor of our design limit the volume available for circuitry and a power source. The device employs a fixed-rate and fixed-amplitude relaxation oscillator and a tiny, rechargeable lithium ion power cell. For both research and clinical applications, it is valuable to monitor the electrode-myocardium interface in order to determine that adequate pacemaker output is being provided. This is typically accomplished by observing the minimal stimulus strength that achieves threshold for pacing capture. The output of our simple micropacemaker cannot be programmatically altered to determine this minimal capture threshold, but a safety factor can be inferred by determining the refractory period for ventricular capture at a given stimulus strength. This is done by measuring the minimal timing between naturally occurring QRS complexes and pacing stimuli that successfully generate a premature ventricular contraction. The method was tested in a pilot study in four fetal sheep and the data demonstrate that a relative measure of threshold is obtainable. This method provides valuable real-time information about the electrode-tissue interface.

Fetal cardiac interventions: an update of therapeutic options

Objective

This article aims to present updated therapeutic options for fetal congenital heart diseases.

Methods

Data source for the present study was based on comprehensive literature retrieval on fetal cardiac interventions in terms of indications, technical approaches and clinical outcomes.

Results

About 5% of fetal congenital heart diseases are critical and timely intrauterine intervention may alleviate heart function. Candidates for fetal cardiac interventions are limited. These candidates may include 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 advocated option are prenatal aortic valvuloplasty, pulmonary valvuloplasty, creation of atrial communication and fetal cardiac pacing.

Conclusion

Fetal cardiac interventions are feasible at midgestation with gradually improved technical success and fetal/postnatal survival due mainly to a well-trained multidisciplinary team, sophisticated equipment and better postnatal care.

Fetal surgery: an overview

In utero fetal surgery interventions are currently considered in selected cases of congenital diaphragmatic hernia, cystic pulmonary abnormalities, amniotic band sequence, selected congenital heart abnormalities, myelomeningocele, sacrococcygeal teratoma, obstructive uropathy, and complications of twin pregnancy. Randomized controlled trials have demonstrated an advantage for open fetal surgery of myelomeningocele and for fetoscopic selective laser coagulation of placental vessels in twin-to-twin transfusion syndrome. The evidence for other fetal surgery interventions, such as tracheal occlusion in congenital diaphragmatic hernia, excision of lung lesions, fetal balloon cardiac valvuloplasty, and vesicoamniotic shunting for obstructive uropathy, is more limited. Conditions amenable to intrauterine surgical treatment are rare; the mother may consider termination of pregnancy as an option for many of them; treatment can be lifesaving but in itself carries risks to both the infant (preterm premature rupture of the membranes, preterm delivery) and the mother. This makes conducting prospective or randomized trials difficult and explains the relative lack of good-quality evidence in this field. Moreover, there is scanty information on long-term outcomes. It is recommended that fetal surgery procedures be performed in centers with extensive facilities and expertise. The aims of this review were to describe the main fetal surgery procedures and their evidence-based results and to provide generalist obstetricians with an overview of current indications for fetal surgery.

A percutaneously implantable fetal pacemaker

A miniaturized, self-contained pacemaker that could be implanted with a minimally invasive technique would dramatically improve the survival rate for fetuses that develop hydrops fetalis as a result of congenital heart block. We are currently validating a device that we developed to address this bradyarrhythmia. Preclinical studies in a fetal sheep model are underway to demonstrate that the device can be implanted via a minimally invasive approach, can mechanically withstand the harsh bodily environment, can induce effective contractions of the heart muscle with an adequate safety factor, and can successfully operate for the required device lifetime of three months using the previously-developed closed loop transcutaneous recharging system.

Percutaneously injectable fetal pacemaker: electronics, pacing thresholds, and power budget

We are developing a cardiac pacemaker that is designed to be implanted percutaneously into a fetus to treat complete heart block and consequent hydrops fetalis, which is otherwise fatal. One of the most significant considerations for this device is the technical challenges presented by the battery and charging system. The size of the device is limited to about 3 mm in diameter; batteries on this scale have very small charge capacities. The smaller capacity means that the device needs to be designed so that it uses as little current as possible and so that its battery can be recharged wirelessly. We determined the pacing thresholds for a simple relaxation oscillator that can be assembled from discrete, surface mount components and analyzed the power consumption of the device given different electrode configurations and stimulus parameters. An inductive recharging system will be required for some patients; it is feasible within the package constraints and under development.

Percutaneously injectable fetal pacemaker: electrodes, mechanical design and implantation

We are developing a self-contained cardiac pacemaker with a small, cylindrical shape (~3 × 20 mm) that permits it to be implanted percutaneously into a fetus to treat complete heart block and consequent hydrops fetalis, which is otherwise fatal. The device uses off-the-shelf components including a rechargeable lithium cell and a highly efficient relaxation oscillator encapsulated in epoxy and glass. A corkscrew electrode made from activated iridium can be screwed into the myocardium, followed by release of the pacemaker and a short, flexible lead entirely within the chest of the fetus to avoid dislodgement from fetal movement. The feasibility of implanting the device percutaneously under ultrasonic imaging guidance was demonstrated in acute adult rabbit experiments.

Design and testing of a percutaneously implantable fetal pacemaker

We are developing a cardiac pacemaker with a small, cylindrical shape that permits percutaneous implantation into a fetus to treat complete heart block and consequent hydrops fetalis, which can otherwise be fatal. The device uses off-the-shelf components including a rechargeable lithium cell and a highly efficient relaxation oscillator encapsulated in epoxy and glass. A corkscrew electrode made from activated iridium can be screwed into the myocardium, followed by release of the pacemaker and a short, flexible lead entirely within the chest of the fetus to avoid dislodgement from fetal movement. Acute tests in adult rabbits demonstrated the range of electrical parameters required for successful pacing and the feasibility of successfully implanting the device percutaneously under ultrasonic imaging guidance. The lithium cell can be recharged inductively as needed, as indicated by a small decline in the pulsing rate.

The benefits of transplacental treatment of isolated congenital complete heart block associated with maternal anti-Ro/SSA antibodies: a review

Isolated congenital complete atrio-ventricular block (CAVB) is associated with the transplacental passage of maternal autoantibodies directed to foetal Ro/SSA ribonucleoproteins. Their interactions most likely trigger the inflammation of the atrio-ventricular node and the myocardium in susceptible foetuses. The inflamed tissues may then heal with fibrosis that may cause heart block, endocardial fibroelastosis, and dilated cardiomyopathy. CAVB, the most common cardiac complication, typically develops between 18 and 24 gestational weeks. Untreated, the condition carries a significant mortality risk as the foetus needs to overcome the sudden drop in ventricular rate, the loss of normal atrial systolic contribution to ventricular filling, and perhaps concomitant myocardial inflammation and fibrosis. The rationale to treat a foetus at the stage of CAVB is primarily to mitigate myocardial inflammation and to augment foetal cardiac output. Maternal dexamethasone administration has been shown to improve incomplete foetal AV block, myocardial dysfunction, and cavity effusions. Beta-sympathomimetics may be useful to increase the foetal heart rate and myocardial contractility. Published data from our institution suggest an improved survival >90% if maternal high-dose dexamethasone was initiated at the time of CAVB detection and maintained during the pregnancy and if a beta-adrenergic drug was added at foetal heart rates below 55 beats/min. Despite the improvement in outcome, there is an ongoing debate about treatment-related risks. In this review, we will appraise the natural history of untreated CAVB, discuss currently available management options, and examine the results and risks of in-utero treatment of antibody-mediated CAVB.

Fetal cardiac arrhythmia detection and in utero therapy

The human fetal heart develops arrhythmias and conduction disturbances in response to ischemia, inflammation, electrolyte disturbances, altered load states, structural defects, inherited genetic conditions, and many other causes. Yet sinus rhythm is present without altered rate or rhythm in some of the most serious electrophysiological diseases, which makes detection of diseases of the fetal conduction system challenging in the absence of magnetocardiographic or electrocardiographic recording techniques. Life-threatening changes in QRS or QT intervals can be completely unrecognized if heart rate is the only feature to be altered. For many fetal arrhythmias, echocardiography alone can assess important clinical parameters for diagnosis. Appropriate treatment of the fetus requires awareness of arrhythmia characteristics, mechanisms, and potential associations. Criteria to define fetal bradycardia specific to gestational age are now available and may allow detection of ion channelopathies, which are associated with fetal and neonatal bradycardia. Ectopic beats, once thought to be entirely benign, are now recognized to have important pathologic associations. Fetal tachyarrhythmias can now be defined precisely for mechanism-specific therapy and for subsequent monitoring of response. This article reviews the current and future diagnostic techniques and pharmacologic treatments for fetal arrhythmia.

Development of a new lead for in utero fetal pacing

BACKGROUND

The results from preliminary studies on fetal pacing preclude an application to the human fetus. The purpose of this study was to evaluate the feasibility of acute fetal cardiac pacing following ultrasound-guided epicardial anchorage of a new pacing lead dedicated to the fetal heart.

METHODS

In 12 pregnant ewes, a needle was placed in contact with cardiac chambers under echo-guidance. Using the lumen of the needle, a 3-Fr pacing lead was advanced and fixed on the cardiac wall using a built-in screw. Pacing was attempted using an external pacing system.

RESULTS

Lead insertion was successful in all but one. In the first fetus, the needle was advanced too far into the right ventricle leading to pericardial bleeding. The fetal heart rate was overdriven in all at 220/ min. After assessment, pacing lead was unscrewed and retrieved without any complication. Pregnancy was electively interrupted in six animals. The other six fetuses were delivered vaginally after uneventful pregnancy and autopsy at day 3 did not show any significant injury.

CONCLUSIONS

Transcutaneous echo-guided fetal acute pacing is feasible using a specially designed lead. Additional refinement of both the equipments and the operative technique are needed before considering permanent pacing in the human fetus.

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.

Isolated congenital atrioventricular block diagnosed in utero: natural history and outcome

BACKGROUND

Isolated congenital atrioventricular block (CAVB) diagnosed in utero is associated with a high morbidity and mortality. Prognosis is especially poor when heart rate drops below 55 beats per minute (bpm) and when fetal hydrops develops. We describe the natural history and outcome of 24 infants with isolated CAVB diagnosed in utero, review the literature, and assess the risk factors that could predict outcome.

METHODS

This was a retrospective multicenter study of 24 patients with isolated CAVB diagnosed in utero.

RESULTS

CAVB was detected at a mean gestational age (GA) of 24.7 +/- 5.1 weeks. Ten fetuses initially presented with complete heart block. Low heart rate or incomplete heart block was the first documentation of bradyarrhythmia in the other 14 fetuses. In 11 of them, CAVB developed during pregnancy after a median time of 3 (range 1-16) weeks. Fetal hydrops developed in 10 of 24 (42%) fetuses at a mean GA of 27.6 +/- 5.1 weeks. Hydropic fetuses showed lower heart rates during pregnancy (47 +/- 10 bpm) than non-hydropic fetuses (57 +/- 10 bpm). There were three intrauterine deaths; all were hydropic and female. Nine viable females and 12 males were born at a mean GA of 37.1 +/- 6.1 weeks with an average birth weight of 3097 +/- 852 g. Fifteen CAVB patients required pacemaker (PM) intervention, 10 of them immediately after birth. Dilated cardiomyopathy (DCM) developed in three infants of whom two died of congestive heart failure, shortly after the diagnosis was made; one is still alive. Mortality before or after birth was 21%, and was associated with heart rates below 50 bpm and development of fetal hydrops. Poor outcome, defined as death, PM implantation, or development of DCM, occurred in 83% of cases and was associated with heart rates below 60 bpm during pregnancy.

CONCLUSIONS

Isolated CAVB diagnosed in utero is associated with high morbidity and mortality. Patients who develop fetal hydrops show lower heart rates during pregnancy than patients who do not. A fetal heart rate below 50 bpm and development of fetal hydrops is associated with increased mortality. Rates below 60 bpm are associated with PM requirement and/or DCM.

Fetal intervention for cardiac disease: the cutting edge of perinatal care

Fetal cardiac valvuloplasty has been proposed for progressive cardiac disease with a poor prognosis, such as critical aortic stenosis and pulmonary atresia with intact ventricular septum and balloon atrial septostomy for hypoplastic left heart syndrome, or simple transposition of the great arteries with closed or restrictive inter-atrial communication. It is anticipated that early rescue of ventricles or the pulmonary veins from an unfavourable environment may promote healthier ventricular and vascular growth and improve postnatal outcomes. While close collaboration between the fetal medicine specialist and perinatal cardiologist may optimize the chances of technical success, obstacles to progress include the relative rarity of suitable cases and late referral for therapy. In common with other interventions in fetal medicine, there is a learning curve, and it would benefit progress if the procedures were initially concentrated in just a few centres to enable them to develop skills and experience. Following careful evaluation, it may then be desirable to train further centres and roll out best practice models.

In-utero intervention for severe congenital heart disease

The concept of fetal therapy is well established for many disorders diagnosed before birth but practical issues regarding its introduction into clinical practice are more difficult. Cardiac malformations are common, with major lesions affecting about 3.5 per thousand pregnancies; however, only a small proportion of these is likely to benefit from an intrauterine intervention. In addition, there are no good animal models of human cardiac disease and our knowledge of the underlying mechanisms is at best sketchy. This combination of factors has resulted in slow progress in developing effective therapies for the intrauterine management of cardiac disease. Recent research and clinical developments have included percutaneous valvuloplasty for severe aortic and pulmonary stenosis, perforation of the closed or restrictive inter-atrial septum and pacing for complete heart block. Progress in these endeavours has been variable but - overall - shows promise for treatment of the human fetus.

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.

Cardiac arrhythmias in the human fetus

Fetal cardiac arrhythmias have been recognized with increasing frequency during the past several years. Most fetal arrythmias are intermittent extrasystoles, often presenting as irregular pauses of rhythm. These are significant only when they occur with appropriate timing to initiate sustained tachycardia, mediated by anatomic bypass pathways. The most common important fetal arrhythmias are: 1) supraventricular tachycardias, and 2) severe bradyarrhythmias, associated with complete heart block. Symptomatic fetal tachycardias are usually supraventricular in origin, and may be associated with the developmet of hydrops fetalis. These patients may respond to antiarrhythmic drug therapy, administered via maternal ingestion or via direct fetal injection. Such therapy should be offered with careful fetal and maternal monitoring, and must be based on a logical, sequential analysis of the electrical mechanism underlying the arrhythmia, and an appreciation of the pharmacology and pharmacokinetics of the maternal, placental fetal system. Bradycardia from complete heart block may either be associated with complex congential heart malformations involving the atrioventricular junction of the heart, or may present in fetuses with normal cardiac structure, in mothers with autoimmune conditions associated with high titres of anti-SS-A or anti-SS-B antibody, which cross the placenta to cause immune-related inflammatory damage to the fetal atroventricular node. This paper reviews experience with the analysis of fetal caridac rhythm, a detailed discussion of the pathophysiology of arrhythmias and their effect on the fetal circulatory system, and offers a logical framework for the construction of treatment algorithms for fetuses at risk for circulatory compromise from fetal arrhythmias.

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.

Interventional treatment for fetus and newborn infant with congenital heart disease

BACKGROUND

Catheter intervention has become popular not only in adult patients but in younger patients with congenital heart disease. The early neonatal catheter interventional treatment has also been attempted in conjunction with the development of prenatal diagnosis of the congenital heart disease.

METHOD

Recent articles concerning several severe structural cardiac diseases in newborns, such as critical aortic stenosis, complete transposition of the great arteries, premature constriction of the ductus arteriosus, and pulmonary stenosis or atresia with intact ventricular septum are introduced with consideration.

RESULTS

This study investigated our own experiences of early neonatal balloon valvuloplasty in a patient with critical aortic stenosis carried out immediately after the delivery following prenatal diagnosis. A case with prenatal diagnosis of premature constriction of ductus arteriosus which could prevent persistent pulmonary hypertension of the newborn by early delivery at 39 weeks and 1 day of gestation were reported.

CONCLUSION

Several cardiac interventional treatments performed in the present time during the perinatal period and some prospects in the near future are described in the discussion.

Successes and shortcomings of fetal echocardiography

While it is possible to perform balloon valvuloplasty of a critically stenosed pulmonary valve in the fetus safely, the majority of serious heart conditions remain undiagnosed until after birth. This article addresses the successes and shortcomings of fetal cardiology.

Fetoscopic direct fetal cardiac access in sheep : An important experimental milestone along the route to human fetal cardiac intervention

BACKGROUND

Fetal cardiac interventions by direct ultrasound-guided approaches or open fetal cardiac surgery have been fraught with technical difficulties, as well as with significant maternal and fetal morbidity in humans. Therefore, the purpose of our study in sheep was to assess the feasibility and potential of fetoscopic direct fetal cardiac access.

METHODS AND RESULTS

In 15 anesthetized pregnant ewes (88 to 109 days of gestation; term, 145 days), 3 to 4 trocars were percutaneously placed in the uterus. Using videofetoscopic equipment, we assessed the feasibility of achieving direct fetal cardiac access. Minimally invasive direct fetal cardiac access by operative fetoscopy was achieved in 10 of the 15 fetal sheep. In 7 fetuses, the approach was successfully tested for fetal cardiac pacing (n=5) or antegrade fetal cardiac catheterization (n=2). Access was not achieved in 5 fetuses because of bleeding complications (n=2) or because the fetoscopic setup could not be established (n=3). All but 2 fetal sheep were alive at the end of the procedure. Acute fetal demise resulted from maternal hypotension or kinking of the fetal inferior caval vein by sternal suspension. Six ewes continued gestation; 3 of these went to term, with a normal fetal outcome. Two ewes died from septicemia 3 and 7 days after the procedure, and 1 ewe aborted 1 month after the procedure.

CONCLUSIONS

Minimally invasive direct fetal cardiac access by operative fetoscopy is feasible in fetal sheep. The fetoscopic approach carries important potential for fetal cardiac pacing, antegrade fetal valvuloplasties, and resection of fetal intrapericardial teratomas in human fetuses.

Fetal treatment of congenital heart block ascribed to anti-SSA antibody: case reports with observation of cardiohemodynamics and review of the literature

PROBLEM

Maternal anti-SSA(B) antibody crosses the placenta and causes fetal myocarditis, congenital heart block (CHB), hydrops fetalis, and intrauterine fetal death. The aim of this study was to evaluate corticosteroids' efficacy as a treatment for CHB.

METHOD OF STUDY

One fetus with complete CHB and one fetus with incomplete CHB due to anti-SSA(B) antibody received maternal prednisolone (PSL) and dexamethasone (DEXA) treatments. Heart rate, cardiothoracic ratio (CTR), left ventricular fractional shortening (FS), and preload index (PLI) were longitudinally measured by serial fetal echocardiograms.

RESULTS

In the former case, after maternal PSL/DEXA administration, improvement of cardiohemodynamics, i.e., the reduction of PLI from 1.7 to 0.4, CTR from 70 to 52%, and FS from 63 to 54% were observed. In the latter case, second degree 2:1 block was converted to 3:2 block/sinus rhythm, resulting in the increase of the fetal heart rate from 65 to 116 beats per minute (bpm).

CONCLUSIONS

We disclosed for the first time the beneficial effects of corticosteroids in the fetal cardiohemodynamics and conduction system of affected fetuses with the presence of maternal anti-SSA(B) antibodies.

Hypocomplementemia correlates with intrauterine growth retardation in systemic lupus erythematosus

PROBLEM

The aim of this study was to elucidate fetomaternal risks in systemic lupus erythematosus (SLE)-complicated pregnancy.

METHOD OF STUDY

Pregnancy course, complications, and fetal outcome in 82 pregnancies of 55 patients with SLE were investigated.

RESULTS

These 82 pregnancies resulted in 14 fetal losses and 66 live births. Without clinical manifestation of SLE-flare, 4 of 8 patients who had low serum complement activity during the pregnancies delivered small-for-date neonates. The rate of the intrauterine growth retardation was significantly higher than that observed in pregnancies with normal complement activity. The frequency of premature deliveries (60%) in patients who received more than 15 mg/day of prednisolone was significantly high when compared with pregnancies maintained by 0-15 mg/day (13.1%).

CONCLUSIONS

These data demonstrate the preconceptional and perinatal management necessary in SLE and suggest that the pregnancy with hypocomplementemia, the disease activity, and/or a relatively high maintenance dose of corticosteroid should be carefully managed and monitored.

Management of fetal cardiac arrhythmias

While most fetal cardiac arrhythmias are benign in nature, some may be dangerous and require prenatal treatment. This article reviews the differential diagnoses of fetal tachycardias and bradycardias, as well as treatment and management approaches.

Developmental biology of the heart: is there a role for the physiologist?

Support for physiological research has generally declined, as interest in cellular and molecular investigation has assumed ascendancy. However, there are many important issues relating to cardiovascular development that require a systems approach to study of the circulation. Examples are mechanisms of circulatory response to hypoxia during fetal life; changes in myocardial growth in response to loading before and after birth, and resultant cardiac function; and prenatal and postnatal development of the great vessels with altered circulatory patterns in congenital heart lesions. These issues are of great concern in considerations for potential fetal cardiovascular surgery.

Transesophageal echocardiography in fetal sheep. A monitoring tool for open and fetoscopic cardiac procedures

BACKGROUND

Cardiac procedures in exteriorized fetuses or assisted by fetoscopy require monitoring capabilities not attended by conventional maternal transabdominal echocardiography.

METHODS

We, therefore, assessed the potential of fetal transesophageal echocardiography (TEE) utilizing an intravascular ultrasound catheter (IVUC) for fetal cardiac monitoring. We inserted a 10-F-10-MHz IVUC into the esophagus in 12 exteriorized fetal sheep and by a fetoscopic approach in 4 fetal sheep. Cardiac events were observed. Heart rate, cardiac rhythm, patency of the foramen ovale and ductus arteriosus, and the width of the branch pulmonary arteries could be assessed in all fetuses. Ventricular contractility could be assessed only in fetuses weighing less than 2.5 kg. Larger fetuses did not allow adequate imaging of the apical portion of the ventricles because of limited tissue penetration of the IVUC. Fetal TEE permitted placing small guide wires in the cardiac atria and left ventricle. Short-lived premature beats following intracardiac manipulations of these wires could be observed by fetal TEE in all cases.

RESULTS

At autopsy, no complications from IVUC insertion were observed in the exteriorized fetuses. Fetoscopic placement of the IVUC resulted in minor perioral skin erosion in two nonexteriorized fetuses.

CONCLUSIONS

In conclusion, fetal TEE can be achieved with minor fetal injury and may provide useful information during open and fetoscopic cardiac procedures. Further improvements in IVUC design will permit the application of this technique to monitor human fetal cardiac procedures.

Experimental fetal transesophageal and intracardiac echocardiography utilizing intravascular ultrasound technology

Fetal transesophageal and intracardiac echocardiography by utilizing ultrasound technology permits accurate definition of cardiac anatomy in fetal sheep. Because fetal transesophageal echocardiography is less invasive than intracardiac echocardiography, it has the potential to serve as a monitoring tool for currently developed open and fetoscopic fetal cardiac interventions.

Successful in utero therapy of fetal heart block

OBJECTIVE

Congenital complete heart block is associated with maternal autoantibodies to Ro and La proteins, which injure the fetal cardiac conduction system. We administered dexamethasone to the mothers of five fetuses with heart block caused by maternal antibodies.

STUDY DESIGN

We diagnosed five cases of fetal heart block at 20 to 23 weeks and treated all mothers with dexamethasone 4 mg orally each day for the remainder of the pregnancy. All patients were positive for anti-SS-A (anti-Ro) and/or anti-SS-B (anti-La) antibodies.

RESULTS

Four patients had complete heart block, and one had second-degree block. In two patients (one with complete heart block, one with second-degree heart block) the degree of block lessened with treatment. Hydrops in three complete heart block patients resolved after treatment. Maternal antibody levels did not change. Matched maternal and cord samples at delivery showed similar antibody levels.

CONCLUSIONS

Complete heart block can respond to transplacental glucocorticoid therapy with improved cardiac conduction. Because there may be a concurrent myocarditis, treatment in utero may also improve cardiac contractility, leading to the observed rapid resolution of hydrops. Treatment with steroids that cross the placenta should be considered for newly diagnosed cases of complete heart block with positive antibody screens.