Drug treatment of fetal tachycardias

Pharmacological Management of Cardiac Arrhythmias in the Fetal and Neonatal Periods: A Scientific Statement From the American Heart Association: Endorsed by the Pediatric & Congenital Electrophysiology Society (PACES)

Disorders of the cardiac rhythm may occur in both the fetus and neonate. Because of the immature myocardium, the hemodynamic consequences of either bradyarrhythmias or tachyarrhythmias may be far more significant than in mature physiological states. Treatment options are limited in the fetus and neonate because of limited vascular access, patient size, and the significant risk/benefit ratio of any intervention. In addition, exposure of the fetus or neonate to either persistent arrhythmias or antiarrhythmic medications may have yet-to-be-determined long-term developmental consequences. This scientific statement discusses the mechanism of arrhythmias, pharmacological treatment options, and distinct aspects of pharmacokinetics for the fetus and neonate. From the available current data, subjects of apparent consistency/consensus are presented, as well as future directions for research in terms of aspects of care for which evidence has not been established.

2023 HRS expert consensus statement on the management of arrhythmias during pregnancy

This international multidisciplinary expert consensus statement is intended to provide comprehensive guidance that can be referenced at the point of care to cardiac electrophysiologists, cardiologists, and other health care professionals, on the management of cardiac arrhythmias in pregnant patients and in fetuses. This document covers general concepts related to arrhythmias, including both brady- and tachyarrhythmias, in both the patient and the fetus during pregnancy. Recommendations are provided for optimal approaches to diagnosis and evaluation of arrhythmias; selection of invasive and noninvasive options for treatment of arrhythmias; and disease- and patient-specific considerations when risk stratifying, diagnosing, and treating arrhythmias in pregnant patients and fetuses. Gaps in knowledge and new directions for future research are also identified.

Fetal Arrhythmia Diagnosis and Pharmacologic Management

One of the most successful achievements of fetal intervention is the pharmacologic management of fetal arrhythmias. This management usually takes place during the second or third trimester. While most arrhythmias in the fetus are benign, both tachy‐ and bradyarrhythmias can lead to fetal hydrops or cardiac dysfunction and require treatment under certain conditions. This review will highlight precise diagnosis by fetal echocardiography and magnetocardiography, the 2 primary means of diagnosing fetuses with arrhythmia. Additionally, transient or hidden arrhythmias such as bundle branch block, QT prolongation, and torsades de pointes, which can lead to cardiomyopathy and sudden unexplained death in the fetus, may also need pharmacologic treatment. The review will address the types of drug therapies; current knowledge of drug usage, efficacy, and precautions; and the transition to neonatal treatments when indicated. Finally, we will highlight new assessments, including the role of the nurse in the care of fetal arrhythmias. The prognosis for the human fetus with arrhythmias continues to improve as we expand our ability to provide intensive care unit–like monitoring, to better understand drug treatments, to optimize subsequent pregnancy monitoring, to effectively predict timing for delivery, and to follow up these conditions into the neonatal period and into childhood. Coordinated initiatives that facilitate clinical fetal research are needed to address gaps in knowledge and to facilitate fetal drug and device development.

Efficacy and Safety of Various First-Line Therapeutic Strategies for Fetal Tachycardias: A Network Meta-Analysis and Systematic Review

Background: Fetal arrhythmias are common cardiac abnormalities associated with high mortality due to ventricular dysfunction and heart failure, particularly when accompanied by hydrops. Although several types of common fetal tachycardias have been relatively identified medications, such as digoxin, flecainide, and sotalol, there is no first-line drug treatment protocol established for the treatment of various types of fetal tachycardias.

Methods: We conducted a network meta-analysis using a Bayesian hierarchical framework to obtain a model for integrating both direct and indirect evidence. All tachycardia types (Total group), supraventricular tachycardia (SVT subgroup), atrial flutter (AF subgroup), hydrops subgroup, and non-hydrops subgroup fetuses were analyzed, and five first-line regimens were ranked according to treatment outcomes: digoxin monotherapy (D), flecainide monotherapy (F), sotalol monotherapy (S), digoxin plus flecainide combination therapy (DF), and digoxin plus sotalol combination therapy (DS). Effectiveness and safety were determined according to the cardioversion rate and intrauterine death rate.

Results: The pooled data indicated that DF combination therapy was always superior to D monotherapy, regardless of the tachycardia type or the presence of hydrops: Total, 2.44 (95% CrI: 1.59, 3.52); SVT, 2.77 (95% CrI: 1.59, 4.07); AF, 67.85 (95% CrI: 14.25, 168.68); hydrops, 6.03 (95% CrI: 2.54, 10.68); and non-hydrops, 5.06 (95% CrI: 1.87, 9.88). DF and F had a similar effect on control of fetal tachycardias. No significant differences were observed when comparing S, DS with D therapies across the subgroup analyses for the SVT, hydrops, and non-hydrops groups. No significant differences in mortality risks were among the various treatment regimens for the total group. And no significant differences were found in rates of intrauterine death rates at the same cardioversion amount.

Conclusion The flecainide monotherapy and combination of digoxin and flecainide should be considered the most superior therapeutic strategies for fetal tachycardia.

Systematic Review Registration: (https://www.crd.york.ac.uk/PROSPERO/display_record.php?RecordID=288997), identifier (288997).

Fetal Intervention for Refractory Supraventricular Tachycardia Complicated by Hydrops Fetalis

Introduction. Few reports have shown promising treatments for refractory fetal tachycardia. Data are limited regarding optimal treatment, route of treatment, and medication dosages. Over 90% of cases of fetal tachycardia can be attributed to supraventricular tachycardia (SVT). The first-line treatment of fetal SVT is transplacental digoxin. Case Presentation. We present the management of a patient with fetal tachyarrhythmia diagnosed at 24 weeks and offer a unique approach for treatment. Fetal intramuscular injection of 72.3 mcg of digoxin allowed for resolution of SVT and sustained normal sinus rhythm. Further assessment in the third trimester showed persistent hydrops in the setting of mirror (Ballantyne's) syndrome resulting in delivery. Discussion/Conclusion. Our observations suggest that a one-time injection of digoxin allows for complete resolution of SVT. Utilizing an invasive approach for management of SVT that is resistant to traditional treatment modalities appears to both be therapeutic and decrease maternal adverse effects associated with more toxic effects of other transplacental medications.

Multiple antiarrhythmic transplacental treatments for fetal supraventricular tachyarrhythmia: A protocol for systematic review and meta analysis

BACKGROUND

Fetal supraventricular tachyarrhythmia is a common reason for referral to fetal cardiology. Multiple antiarrhythmic transplacental medications can be used to treat these diseases. Debates remain regarding the standardized therapy.

METHODS

PubMed, EMBASE, Cochrane Library, Web of Science, Google Scholar, and ClinicalTrials.gov will be searched from inception to September 2020. A handsearching for gray literature, including unpublished conference articles, will be performed. The randomized control trials, case-control, and cohort studies will be accepted, no matter what the languages they were reported. We will first focus on the effectiveness of the therapy on fetal cardiac rhythm and/or heart rate. Then we will do further analysis of preterm delivery, fetal hydrops, intrauterine fetal demise, and maternal side effects. The Cochrane Risk of Bias Tool and the Newcastle-Ottawa scale will be used to assess the risk of bias of the randomized controlled trials, case-control, and cohort studies, respectively. Two independent reviewers will carry out literature identification, data collection, and study quality assessment. Discrepancies will be resolved by a third reviewer. Statistical analysis will be conducted using the STATA 13.0 software.

RESULT

The results will provide helpful information about the effect of multiple antiarrhythmic transplacental therapies in pregnancies with supraventricular tachycardia or atrial flutter, and demonstrate which therapy is more effective.

CONCLUSION

The conclusion drawn from this systematic review will benefit the patients with fetal supraventricular tachyarrhythmia.

Rare Case of Fetal Permanent Junctional Reciprocating Tachycardia Refractory to Prenatal Antiarrhythmic Therapy

Permanent junctional reciprocating tachycardia (PJRT) is a rare form of atrioventricular reentrant tachycardia that is commonly resistant to most antiarrhythmic medication therapy and over an extended duration can result in tachycardia-induced cardiomyopathy. The prenatal presentation of PJRT is typically similar to that of other types of fetal supraventricular tachycardia (SVT), making it difficult to distinguish from other forms of SVT in utero by fetal echocardiography. Surface electrocardiography after delivery is typically required to make a definitive diagnosis of PJRT. We report a case of fetal SVT at 19 weeks’ gestation refractory to maternal transplacental treatment with digoxin, amiodarone, flecainide, sotalol, metoprolol, intraumbilical amiodarone, and fetal intramuscular digoxin over the course of 12 weeks. Repeat cesarean delivery was performed at 30 2/7 weeks’ gestation for tachycardia-induced cardiomyopathy with hydrops fetalis. Postnatal electrocardiogram and continuous rhythm monitoring confirmed the diagnosis of PJRT. Combined neonatal treatment with amiodarone, digoxin, and propranolol was successful in reestablishment of sinus rhythm, with radiofrequency ablation planned if medical therapy eventually fails or once early childhood is reached. To our knowledge, this is the first described case of fetal PJRT refractory to multiple standard in utero antiarrhythmic modalities and highlights the importance of inclusion in the differential diagnosis.

Rapid Quantitation of Flecainide in Human Plasma for Therapeutic Drug Monitoring Using Liquid Chromatography and Time-of-Flight Mass Spectrometry

BACKGROUND

Measurement of flecainide is useful to optimize dosage and minimize risks of toxicity. Furthermore, there is a need for urgent sample analysis when flecainide is used in transplacental therapy for fetal tachycardia. To this end, we have developed and validated a rapid assay for the measurement of flecainide in human plasma or serum, using a small sample volume (50 µL).

METHODS

After a simple deproteination with zinc sulfate and methanol, prepared samples were injected onto a short (30 mm) analytical column and eluted using a rapid gradient elution. Detection was performed using time-of-flight mass spectrometry. Flecainide was quantified using flecainide-D4 as internal standard, with both compounds extracted from the total ion chromatogram using a ±5 ppm extraction window based on the theoretical m/z values for the protonated ions.

RESULTS

The assay was linear over a putative therapeutic range (100-1500 mcg/L). Between- and within-assay imprecision and accuracy were <4.6% and 94.8%-110.0%, respectively. Matrix effects were minimal and were compensated for by flecainide-D4. There were no effects due to hemolysis or lipemia, and no carryover was apparent. Total analysis time was just 1.2 minutes (72 seconds).

CONCLUSIONS

We have developed and validated a rapid method for the analysis of flecainide. The method is particularly suited for flecainide therapeutic drug monitoring, when analyzing samples from mothers receiving flecainide for the treatment of fetal tachycardia.

Contributions of Drug Transporters to Blood-Placental Barrier

The placenta is the only organ linking two different individuals, mother and fetus, termed as blood-placental barrier. The functions of the blood-placental barrier are to regulate material transfer between the maternal and fetal circulation. The main functional units are the chorionic villi within which fetal blood is separated by only three or four cell layers (placental membrane) from maternal blood in the surrounding intervillous space. A series of drug transporters such as P-glycoprotein (P-GP), breast cancer resistance protein (BCRP), multidrug resistance-associated proteins (MRP1, MRP2, MRP3, MRP4, and MRP5), organic anion-transporting polypeptides (OATP4A1, OATP1A2, OATP1B3, and OATP3A1), organic anion transporter 4 (OAT4), organic cation transporter 3 (OCT3), organic cation/carnitine transporters (OCTN1 and OCTN2), multidrug and toxin extrusion 1 (MATE1), and equilibrative nucleoside transporters (ENT1 and ENT2) have been demonstrated on the apical membrane of syncytiotrophoblast, some of which also expressed on the basolateral membrane of syncytiotrophoblast or fetal capillary endothelium. These transporters are involved in transport of most drugs in the placenta, in turn, affecting drug distribution in fetus. Moreover, expressions of these transporters in the placenta often vary along with the gestational ages and are also affected by pathophysiological factor. This chapter will mainly illustrate function and expression of these transporters in placentas, their contribution to drug distribution in fetus, and their clinical significance.

Maternal monitoring and safety considerations during antiarrhythmic treatment for fetal supraventricular tachycardia

Fetal tachycardia is a rare complication during pregnancy. After exclusion of maternal and fetal conditions that can result in a secondary fetal tachycardia, supraventricular tachycardia is the most common cause of a primary sustained fetal tachyarrhythmia. In cases of sustained fetal supraventricular tachycardia, maternal administration of digoxin, flecainide, sotalol, and more rarely amiodarone, is considered. As these medications have the potential to cause significant adverse effects, we sought to examine maternal safety during transplacental treatment of fetal supraventricular tachycardia. In this narrative review we summarize the literature addressing pharmacologic properties, monitoring, and adverse reactions associated with medications most commonly prescribed for transplacental therapy of fetal supraventricular tachycardia. We also describe maternal monitoring practices and adverse events currently reported in the literature. In light of our findings, we provide clinicians with a suggested maternal monitoring protocol aimed at optimizing safety.

Pharmacological Therapy of Tachyarrhythmias During Pregnancy

Tachyarrhythmias are the most frequently observed cardiac complications during pregnancy. The majority of these maternal and foetal arrhythmias are supraventricular tachyarrhythmias; ventricular tachyarrhythmias are rare. The use of anti-arrhythmic drugs (AADs) during pregnancy is challenging due to potential foetal teratogenic effects. Maintaining stable and effective therapeutic maternal drug levels is difficult due to haemodynamic and metabolic alterations. Pharmacological treatment of tachyarrhythmias is indicated in case of maternal haemodynamic instability or hydrops fetalis. Evidenc e regarding the efficacy and safety of AAD therapy during pregnancy is scarce and the choice of AAD should be based on individual risk assessments for both mother and foetus. This review outlines the current knowledge on the development of tachyarrhythmias during pregnancy, the indications for and considerations of pharmacological treatment and its potential side-effects.

Drug resistant fetal arrhythmia in obstetric cholestasis

Obstetric cholestasis (OC) is a pregnancy specific liver disease characterized by increased levels of bile acid (BA) and pruritus. Raised maternal BA levels could be associated with intrauterine death, fetal distress, and preterm labor and also alter the rate and rhythm of cardiomyocyte contraction and may cause fetal arrhythmic events. We report a case of drug resistant fetal supraventricular tachycardia and concomitant OC. Conclusion. If there are maternal OC and concomitant fetal arrhythmia, possibility of the resistance to antiarrhythmic treatment should be kept in mind.

Successful medical treatment of fetal supraventricular tachycardia that cause hydrops fetalis

Supraventricular tachycardia (SVT) is the most frequent fetal tachyarrhythmia. Diagnosis is established with M-mode ultrasound and/or Doppler investigation. Untreated cases may develop fetal heart failure and hydrops. Even these cases should not be left untreated - maternal administration of anti-arrhythmic drugs should be undertaken. In this manuscript, we describe a successful treatment with maternal administration of sotalol and digoxin in a fetus that developed hydrops because of SVT.

Fetal supraventricular tachycardia, treating the baby by targeting the mother

Fetal supraventricular tachycardia (SVT) is the most common form of fetal tachycardia. If started early in pregnancy, it can cause non-immune fetal hydrops. Echocardiography is the preferred method for the diagnosis with simultaneous pulsed Doppler recording from the superior vena cava and ascending aorta. Transplacental therapy with digoxin is the most common way of treatment. We present a case of fetal SVT detected at 26 weeks of pregnancy. Digoxin therapy restored the rhythm initially, but later paroxysms of fetal SVT persisted necessitating the addition of second antiarrhythmic medication which was discussed with the parents. The couple chose to proceed for premature delivery at 32 weeks.

The pediatric cardiology pharmacopeia: 2013 update

The use of medications plays a pivotal role in the management of children with heart diseases. Most children with increased pulmonary blood flow require chronic use of anticongestive heart failure medications until more definitive interventional or surgical procedures are performed. The use of such medications, particularly inotropic agents and diuretics, is even more amplified during the postoperative period. Currently, children are undergoing surgical intervention at an ever younger age with excellent results aided by advanced anesthetic and postoperative care. The most significant of these advanced measures includes invasive and noninvasive monitoring as well as a wide array of pharmacologic agents. This review update provides a medication guide for medical practitioners involved in care of children with heart diseases.

Effectiveness of sotalol as first-line therapy for fetal supraventricular tachyarrhythmias

Fetal supraventricular tachycardia (SVT) and atrial flutter (AF) can be associated with significant morbidity and mortality. Digoxin is often used as first-line therapy but can be ineffective and is poorly transferred to the fetus in the presence of fetal hydrops. As an alternative to digoxin monotherapy, we have been using sotalol at presentation in fetuses with SVT or AF with, or at risk of, developing hydrops to attempt to achieve more rapid control of the arrhythmia. The present study was a retrospective review of the clinical, echocardiographic, and electrocardiographic data from all pregnancies with fetal tachycardia diagnosed and managed at a single center from 2004 to 2008. Of 29 affected pregnancies, 21 (16 SVT and 5 AF) were treated with sotalol at presentation, with or without concurrent administration of digoxin. Of the 21, 11 (6 SVT and 5 AF) had resolution of the tachycardia within 5 days (median 1). Six others showed some response (less frequent tachycardia, rate slowing, resolution of hydrops) without complete conversion. In 1 fetus with a slow response, the mother chose pregnancy termination. The 5 survivors with a slow response were all difficult to treat postnatally, including 1 requiring radiofrequency ablation as a neonate. One fetus developed blocked atrial extrasystoles after 1 dose of sotalol and was prematurely delivered for fetal bradycardia. Three grossly hydropic fetuses with SVT showed no response and died within 1 to 3 days of treatment. In conclusion, transplacental sotalol, alone or combined with digoxin, is effective for the treatment of fetal SVT and AF, with an 85% complete or partial response rate in our series.

Transplacental digoxin therapy for fetal tachyarrhythmia with multiple evaluation systems

BACKGROUND

Sustained fetal tachyarrhythmia may result in congestive heart failure, hydrops fetalis, and fetal/neonatal death, which requires timely and appropriate therapy.

AIM

To determine the value of transplacental digoxin therapy for fetal tachyarrhythmia with multiple evaluations.

METHODS

Four cases of fetal tachyarrhythmia were diagnosed with fetal echocardiography and treated with transplacental digoxin therapy with an initial dosage of 0.25 mg qd. Fetal echocardiography and measurement of maternal serum digoxin concentrations were performed every 5-7 days. Echocardiographic information was further used for the calculation of three evaluation systems including, Tei index, cardiovascular profile score (CVPS), and umbilical artery resistance index (UARI). The dosage of digoxin was adjusted according to the serum concentration, as well as results from three evaluation systems.

RESULTS

During the course of digoxin treatment, our patients show an increase of CVPS and decrease of Tei index and UARI, suggesting the recovery of heart function. Sinus rhythm was restored in 3-10 days in three cases and 42 days in one case. At the time of delivery, the placental transportation efficiency (neonate/mother ratio of serum digoxin concentration) was 76.45-84.31%. Following delivery, the general conditions of neonates were favorable. During the 4- to 14-month follow-up, reoccurrence of arrhythmia, neurological deficit, and retarded growth and development were not observed.

CONCLUSIONS

Transplacental digoxin therapy with combined evaluation of Tei index, CVPS, and UARI systems is useful for treating fetal atrial flutter (AF) and supraventricular tachycardia (SVT).

Perinatal management and long-term cardiac outcome in fetal arrhythmia

BACKGROUND

cardiac arrhythmias are commonly observed in the fetus, however, may have major consequences for fetal development and post natal life.

AIMS

to evaluate the perinatal management and cardiac outcome of fetuses with tachy- or bradyarrhythmia.

STUDY DESIGN

perinatal management, outcome and long-term cardiac follow-up were evaluated retrospectively in consecutive fetuses with cardiac arrhythmias.

RESULTS

forty-four fetuses were diagnosed: supraventricular tachycardia (SVT, n=28), atrial flutter (AF, n=7) and atrioventricular block (AVB, n=9). The overall incidence of cardiac anomalies was 18% mainly in the AVB group; hydrops was present in 34%. Direct or transplacental fetal anti-arrhythmic medication was given in 76%. Mortality was 6% in SVT/AF and 78% in the AVB group, respectively. AF resolved in all patients. In the SVT group, Wolff-Parkinson-White (WPW) syndrome was present in 21%, diagnosed at birth or later in life. After the age of one year about 90% of patients in the SVT group remained asymptomatic and free of drugs (median follow-up 76months).

CONCLUSIONS

mortality rate is low in patients with fetal SVT and AF but high in patients with AVB. Related morbidity includes WPW-syndrome and congenital cardiac anomalies. Electrocardiographic screening is recommended in all fetal SVT cases before adolescence since WPW-syndrome may occur later in life.

Intervention development: assessing critical parameters from the intervention recipient's perspective

Before effective nursing interventions can be translated into practice, they must undergo critical examination. Although randomized controlled trials provide evidence of effectiveness, other intervention parameters require evaluation before effectiveness trials are initiated. This article describes methods for evaluating six parameters of nursing interventions (necessity, acceptability, feasibility, fidelity, safety, and effectiveness) and emphasizes the importance of assessing them from the intervention recipient's perspective.

Expression and function of p-glycoprotein in normal tissues: effect on pharmacokinetics

ATP-binding cassette (ABC) drug efflux transporters limit intracellular concentration of their substrates by pumping them out of cell through an active, energy dependent mechanism. Several of these proteins have been originally associated with the phenomenon of multidrug resistance; however, later on, they have also been shown to control body disposition of their substrates. P-glycoprotein (Pgp) is the first detected and the best characterized of ABC drug efflux transporters. Apart from tumor cells, its constitutive expression has been reported in a variety of other tissues, such as the intestine, brain, liver, placenta, kidney, and others. Being located on the apical site of the plasma membrane, Pgp can remove a variety of structurally unrelated compounds, including clinically relevant drugs, their metabolites, and conjugates from cells. Driven by energy from ATP, it affects many pharmacokinetic events such as intestinal absorption, brain penetration, transplacental passage, and hepatobiliary excretion of drugs and their metabolites. It is widely believed that Pgp, together with other ABC drug efflux transporters, plays a crucial role in the host detoxication and protection against xenobiotic substances. On the other hand, the presence of these transporters in normal tissues may prevent pharmacotherapeutic agents from reaching their site of action, thus limiting their therapeutic potential. This chapter focuses on P-glycoprotein, its expression, localization, and function in nontumor tissues and the pharmacological consequences hereof.

Diagnosis, clinical features, management, and post-natal follow-up of fetal tachycardias

OBJECTIVE

To evaluate the diagnosis, clinical features, management and post-natal follow-up in consecutive fetuses identified with tachycardia.

METHODS

We reviewed consecutive fetuses with tachycardia identified in a single tertiary institution between January, 2001, and December, 2008. We considered several options for management, including no treatment but close surveillance, trans-placental antiarrhythmic therapy in fetuses presenting prior to 36 weeks of gestation, and delivery and treatment as a neonate for fetuses presenting after 36 weeks of gestation. Data was gathered by a review of prenatal and postnatal documentation.

RESULTS

Among 29 fetuses with tachycardia, 21 had supraventricular tachycardia with 1 to 1 conduction, 4 had atrial flutter, 3 had atrial tachycardia, while the remaining fetus had ventricular tachycardia. Of the group, 8 fetuses (27.6%) were hydropic. Transplacental administration of antiarrhythmic drugs was used in just over half the fetuses, delivery and treatment as a neonate in one-quarter, and no intervention but close surveillance in one-sixth of the case. Twenty-six of 29 fetuses (89.7%) were born alive. Only patients with fetal hydrops suffered mortality, with 37.5% of this group dying, this being statistically significant, with the value of p equal to 0.03, when compared to non-hydropic fetuses. Only 3 patients (11.5%) were receiving antiarrhythmic prophylaxis beyond the first year of life.

CONCLUSION

A significant proportion of fetal tachycardias recognized before 36 weeks of gestation can be treated successfully by transplacental administration of antiarrhythmic drugs. Fetuses presenting after 36 weeks of gestation can be effectively managed postnatally. The long-term prognosis for fetuses diagnosed with tachycardia is excellent, with the abnormal rhythm resolving spontaneously during the first year of life in most of them.

Fetal dilated cardiomyopathy caused by persistent junctional reciprocating tachycardia

Ultrasound examination of a fetus at 32 weeks' gestation revealed dilated cardiomyopathy and a heart rate of 170 beats per minute. Prenatally, this mild tachycardia was not primarily suspected to be the cause of the myocardial changes. Postnatal electrocardiography revealed a persistent junctional reciprocating tachycardia (PJRT) and the diagnosis of tachycardia-induced cardiomyopathy (TICM) became apparent. After conversion to a sinus rhythm under digoxin and amiodarone, the cardiac changes regressed. PJRT is a rare form of supraventricular tachycardia. The prenatal findings in the condition have previously been described retrospectively, but it can only be diagnosed postnatally by its characteristic electrocardiographic properties. This case indicates that TICM can occur at lower heart rates than previously assumed. Even severe prenatal cardiomyopathy may be reversible once sinus rhythm has been restored.

Effect of prenatal antiarrhythmic treatment on cardiac function in a twin pregnancy

We present a case of supraventricular tachycardia affecting one fetus in a twin pregnancy. Before and after treatment with flecainide and cardioversion, we examined conduction times and heart rate variability (HRV) in both twins on the basis of magnetocardiography. Cardiac conduction times increased in both fetuses but HRV showed opposing effects with a number of HRV measures. This case demonstrates that magnetocardiography not only enables identification of fetal arrhythmia, but also permits the investigation of the effects of antiarrhythmic treatment on the conductive system as well as on interaction with the autonomic nervous system.

Drug management of fetal tachyarrhythmias: are we ready for a systematic and evidence-based approach?

Fetal tachyarrhythmias are a life-threatening condition complicating a small proportion of normal pregnancies. Despite major advances in the (intrauterine) pharmacologic treatment of these arrhythmias over the last years major uncertainties remain. Among these are controversies in the choice of agents in relation to arrhythmia type, and timing and duration of treatment. Currently, no evidence-based approach to the management of fetal tachyarrhythmias is available. An international registry is proposed as an important step toward obtaining the necessary data to develop evidence-based management strategies.

Prenatal Diagnosis of Atrial Flutter

Fetal tachyarrhythmias are infrequently encountered in utero. They are divided into subgroups including: atrial flutter/fibrillation, supraventricular tachycardia (SVT), sinus tachycardia, and atrial extrasystoles. Tachyarrhythmias can lead to fetal hydrops, congestive heart failure, and possibly fetal demise. Atrial flutter in a fetus is defined by an atrial rate of 300 to 600 beats per minute (bpm), with or without a 1:1 conduction rate to the ventricles. Atrioventricular reentrant tachycardia (AVRT) is the most common cause of supraventricular tachycardia and should be considered in cases of atrial tachycardia. Recognition of cardiac dysrhythmias is essential in early intervention. Cardiac antiarrthymic agents are frequently used with success to convert fetal dysrhythmias to a normal sinus rhythm. Digoxin is typically first-line therapy, and in more advanced or severe cases, additional drugs are often used.

Fetal atrial flutter: a case report and experience of sotalol treatment

OBJECTIVE

Fetal tachyarrhythmia may cause fetal hydrops and lead to fetal morbidity and mortality. Supraventricular tachycardia and atrial flutter have been the most diagnosed. We present a case of fetal atrial flutter diagnosed during the second trimester treated with digoxin and sotalol and delivered at term.

CASE REPORT

A 30-year-old primigravid woman was diagnosed with fetal atrial flutter at the gestational age of 25 weeks with atrial rates of 480-520 bpm and ventricular rates of 200-250 bpm. Initially, she was treated with digoxin then with a combination of digoxin and sotalol. The fetal heart beat slowed after sotalol treatment but did not return to sinus rhythm. The fetus was delivered vaginally. Neonatal echocardiography showed a small apical ventricular septal defect and small patent ductus arteriosus. Electrocardiography also revealed atrial flutter with occasional atrial fibrillation.

CONCLUSION

The efficacy of antiarrhythmic drug therapy for fetal atrial flutter has not been well established. In our case, we used sotalol combined with digoxin and the fetal heart beat slowed after therapy. Sotalol may be considered the drug of choice for fetal atrial flutter. If the fetal atrial flutter is resistant to these therapies, a combination of other congenital cardiac diseases or organic abnormalities should be considered.

P-glycoprotein in the placenta: Expression, localization, regulation and function

Detailed understanding of the mechanisms employed in transfer of drugs across the placenta is essential for optimization of pharmacotherapy during pregnancy. Disclosure of drug efflux transporters as an "active component" of the placental barrier has brought new important insights into the field of transplacental pharmacokinetics. P-glycoprotein (P-gp, MDR1) is the first discovered and so far the best characterized of drug efflux transporters, whose role in the regulation of drug disposition to the fetus has been extensively studied. Expression of P-gp in the placental trophoblast layer was confirmed at the mRNA and protein levels in all phases of pregnancy, and several in vitro and in vivo studies demonstrated functional activity of the transporter in materno-fetal drug transport. P-gp is able to actively pump drugs and other xenobiotics from trophoblast cells back to the maternal circulation, providing thus protection to the fetus. This review summarizes the current knowledge on the expression, localization and function of P-gp in the placenta. In addition, we include the latest data concerning transcriptional regulation of placental P-gp expression and polymorphisms of the MDR1 gene. Clinical significance of placental P-gp and its future perspectives for pharmacotherapy during pregnancy are also discussed.

Amiodarone in Treatment of Fetal Supraventricular Tachycardia

We report a case of nonimmune hydrops fetalis detected at 32 weeks of gestation. Fetal heart rate was 300 beats per minute. Ultrasound and fetal Doppler echocardiography showed it to be due to supraventricular tachycardia (SVT). Following failed maternal therapy with digoxin alone, amiodarone with digoxin was used. Conversion to sinus rhythm and resolution of hydrops followed this treatment. Since there is no ideal treatment protocol for these cases at present, we reviewed reports of transplacental treatment of SVT.

Transplacental pharmacokinetics of flecainide in the gravid baboon and fetus

The objective of this study was to characterize the transfer of flecainide across the placenta and determine the fetal: maternal ratio of flecainide in the gravid baboon. Flecainide acetate has been especially successful for the treatment of fetal supraventricular tachycardia associated with hydrops fetalis. However, the degree of transplacental transmission remains unknown. In this study, all animals were placed under general anesthesia. Flecainide 2.5 mg/kg was administered intravenously. Percutaneous umbilical blood sampling was performed simultaneously with maternal sampling. Flecainide levels were measured using high-performance liquid chromatography with ultraviolet detection. A total of six gravid baboons were studied at an average gestational age of 132 days. The mean maternal volume of distribution at steady state was 5.1 +/- 1.8 L/kg. The mean combined elimination constant (k(el)) was 0.79 +/- 0.19 hr(-1) [95% confidence interval (CI), 0.64-0.93]. There was a linear relationship between maternal and fetal concentrations, with a ratio of fetal-to-maternal serum levels of 0.49 +/- 0.05 (95% CI, 0.39-0.59). At steady state, fetal flecainide levels are approximately 50% of maternal flecainide levels. Flecainide is rapidly distributed in the mother and fetus following a single intravenous dose with a maternal volume of distribution similar to that reported in normal healthy human adults. Since fetal levels correlate closely with maternal levels, we propose that it is possible to estimate fetal levels by monitoring maternal levels.

Successful Management of Supraventricular Tachycardia in a Fetus Using Fetal Magnetocardiography

We report a fetus at 33 weeks of gestation with supraventricular tachycardia, which was successfully managed by transplacental administration of an antiarrhythmic agent. Fetal magnetocardiography (fMCG) revealed supraventricular tachycardia of the long RP' tachycardia type. Transplacental administration of sotalol, instead of digoxin, was selected as the first-line drug, and it successfully converted supraventricular tachycardia to sinus rhythm. The diagnosis of the type of supraventricular tachycardia was confirmed by electrocardiography after birth. Sotalol was also effective after birth to maintain sinus rhythm. This case demonstrates that fMCG is potentially useful for prenatal differentiation of the type of supraventricular tachycardia and for prenatal treatment of fetal tachyarrhythmias.

Management of fetal tachyarrhythmias

Fetal tachyarrhythmias are an important cause of fetal morbidity and mortality. The majority of fetal tachyarrhythmias are due to atrioventricular reentrant type of supraventricular tachycardia and atrial flutter. Fetal echocardiography remains the main tool of diagnosing and discerning the mechanism of tachyarrhythmia. The goals of therapy for fetal arrhythmias are to restore sinus rhythm, resolve heart failure, and postpone delivery before term. Although there is no anonymity in the approach to the drug treatment of fetal tachycardia, digoxin is the most commonly employed first-line antiarrhythmic drug for supraventricular tachycardia. In digoxin nonresponders, flecainide ( digoxin) controls tachyarrhythmia with high conversion rate. A combination of digoxin and sotalol has proved effective therapy for atrial flutter, but the proarrhythmic side effect of sotalol on the fetus has been a concern. Amiodarone has emerged as a second-line treatment after digoxin failure in nonhydropic fetuses and the most effective treatment for drug-refractory fetal tachycardia accompanied by hydrops. Both the fetus and mother should be closely monitored for the response and adverse effect of the treatment. The antiarrhythmic treatment for supraventricular tachycardia should be continued after birth and during infancy due to the high incidence of postnatal recurrence.

Treatment of fetal tachycardia with sotalol: transplacental pharmacokinetics and pharmacodynamics

OBJECTIVES

The aim of this study was to investigate the pharmacokinetics and pharmacodynamics of sotalol in the treatment of fetal tachycardia.

BACKGROUND

Maternally administered, intrauterine therapy of fetal tachycardia is dependent on the transplacental passage of the antiarrhythmic agent.

METHODS

In a prospective study of patients treated for fetal tachycardia with sotalol, concentrations of sotalol were determined in maternal and umbilical blood and in amniotic fluid, and the relationship between these concentrations and the occurrence of conversion to sinus rhythm was investigated.

RESULTS

Eighteen fetal patients were studied, nine with atrial flutter and nine with supraventricular tachycardia. Fourteen were treated with sotalol; 13 converted to sinus rhythm, of whom 2 relapsed. There was one intrauterine death. Four patients were treated with sotalol and digoxin, of whom two were treated successfully. Mean birth weight was 3,266 g. The daily maternal sotalol dose was linearly related to the maternal plasma concentration. The mean fetal/maternal sotalol plasma concentration was 1.1 (range 0.67 to 2.87, SD 0.63), and the mean amniotic fluid/fetal blood ratio of sotalol was 3.2 (range 1.28 to 5.8, SD 1.4). The effectiveness of sotalol therapy could not be extrapolated from maternal blood levels.

CONCLUSIONS

Sotalol is a potent antiarrhythmic agent in the treatment of fetal tachycardia. The placental transfer is excellent. Sotalol accumulates in amniotic fluid but not in the fetus itself. Therefore it seems that renal excretion in the fetus is efficient and greater than the oral absorption by fetal swallowing. The maternal blood level is not a reliable predictor of the chances of success of therapy. Sotalol is not associated with fetal growth restriction.

Persistent junctional reciprocating tachycardia in the fetus

BACKGROUND

Persistent junctional reciprocating tachycardia (PJRT) tends to be a persistent arrhythmia and requires aggressive therapeutic management. Diagnosis and management of this infrequently occurring tachycardia in the fetus at an early stage is of importance for the prevention of congestive heart failure (CHF).

METHODS

A retrospective study of four fetuses with supraventricular tachycardia (SVT) of the PJRT type was performed.

RESULTS

All had sustained SVT (mean of 228 beats/min) at a mean gestational age of 34 + 5 weeks, with CHF present in two. Three fetuses had prenatal characteristics of PJRT on M-mode echocardiography with a ventriculoatrial (VA)/atrioventricular ratio of > 1 on M-mode echocardiography suggesting a slow conducting accessory pathway. All four fetuses had postnatal confirmation of the diagnosis. Transplacental treatment with flecainide was effective in one patient; sotalol as a single drug or in combination with digoxin was partially effective in the remaining three. Two developed sinus rhythm, with short intermittent periods of tachycardia and decreasing signs of CHF; one case showed a minimal decrease in heart rate. Oral propranolol therapy converted two patients postnatally; in the remaining two patients radiofrequency ablation was performed at the age of 5 months and 6 years.

CONCLUSIONS

The characteristics of our prenatal PJRT cases included a sustained heart rate not exceeding 240 beats/min with a long VA interval, the presence of CHF and therapy resistance. Transplacental treatment should be initiated, possibly with a combination of sotalol and digoxin in non-hydropic cases, or flecainide, especially in case of fetal hydrops. Pharmacological therapy is to be preferred postnatally, but radiofrequency ablation seems to be indicated in therapy-resistant cases with CHF, even in the first months of life.