Fetal supraventricular tachycardia treated with flecainide acetate

Perinatal arrhythmias: diagnosis and management

The final common pathway to death in all of us is an arrhythmia, yet we still know far too little about the contribution of conduction abnormalities and arrhythmias to the compromised states of the human fetus. At no other time in the human life cycle is the human being at more risk of unexplained and unexpected death than during the prenatal period. The risk of sudden death from 20-40 weeks gestation is 6-12 deaths/1000 fetuses/year. This is equal to, and in some ethnic groups HIGHER than, the risk of death in the adult population with known coronary artery disease over the same time frame (6-12 deaths/1000 patients/year). Because only a small percentage of the United States population is pregnant each year, because fetal demise is not often acknowledged through public displays such as funerals, and finally because fetal death is culturally accepted to a much greater extent than it should be, this critically important area of women's healthcare has not had the technological advances that have been seen in adult cardiac intensive care and other areas of medicine. Fetal cardiac deaths may be preventable and the diseases that lead to these deaths are often treatable, especially if the sophistication of our modern ICU's could somehow be translated to the prenatal monitoring arena. This review article will outline recent advances in evaluating fetal electrophysiology, helping the perinatologist to better understand the nuances of fetal arrhythmias.

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.

Cardiovascular pharmacotherapeutic considerations during pregnancy and lactation

Cardiovascular drugs are often used in pregnancy for the treatment of maternal and fetal conditions. Mothers could also require continued postpartum drug therapy. Most cardiovascular drugs taken by pregnant women can cross the placenta and therefore expose the developing embryo and fetus to their pharmacologic and teratogenic effects. These effects are influenced by the intrinsic pharmacokinetic properties of a given drug as well as by the complex physiological changes occurring during pregnancy. Many drugs are also transferred into human milk and therefore can potentially have adverse effects on the nursing infant. This 2-part article summarizes some of the available literature concerning the risks and benefits of using various cardiovascular drugs and drug classes during pregnancy and lactation. Included in the discussion are cardiac glycosides, antiarrhythmic drugs, drugs used to treat both acute and chronic hypertension, cholesterol-lowering agents, anticoagulants, thrombolytics, and antiplatelet drugs.

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.

Differential diagnosis and management of the fetus and newborn with an irregular or abnormal heart rate

This article separately discusses the differential diagnosis and management of irregular or abnormal heart rate in both the fetus and the newborn. Conditions covered include ectopic beats, tachyarrythmias,atrial flutter, bradyarrythmias, tachycardia, congenital atrioventricular block, long QT syndrome, and bradycardias,among others.

Amiodarone Therapy for Drug-Refractory Fetal Tachycardia

Background— Fetal tachycardia complicated by ventricular dysfunction and hydrops fetalis carries a significant risk of morbidity and mortality. Transplacental digoxin is effective therapy in a small percentage, but there is no consensus with regard to antiarrhythmic treatment if digoxin fails. This study evaluates the safety, efficacy, and outcome of amiodarone therapy for digoxin-refractory fetal tachycardia with heart failure.

Methods and Results— Fetuses with incessant tachycardia and either hydrops fetalis (n=24) or ventricular dysfunction (n=2) for whom digoxin monotherapy and secondary antiarrhythmic agents (n=13) were not effective were treated transplacentally with a loading dose of oral amiodarone for 2 to 7 days, followed by daily maintenance therapy for <1 to 15 weeks. Digoxin therapy was continued throughout gestation. Newborns were studied by transesophageal pacing or ECG monitoring to determine the mechanism of tachycardia. Three fetuses were delivered urgently in tachycardia during amiodarone loading, and 3 required additional antiarrhythmic agents for sustained cardioversion. Amiodarone or amiodarone combinations converted 14 of 15 (93%) with reentrant supraventricular tachycardia, 2 of 2 with ventricular or junctional ectopic tachycardia, and 3 of 9 (33%) with atrial flutter. Amiodarone-related adverse effects were transient in 5 infants and 8 mothers. Mean gestational age at delivery was 37 weeks, with 100% survival.

Conclusions— Orally administered amiodarone is safe and effective treatment for drug-refractory fetal tachycardia, specifically reentrant supraventricular tachycardia, junctional ectopic, or ventricular tachycardia, even when accompanied by hydrops fetalis or ventricular dysfunction.

Drug treatment of fetal tachycardias

The pharmacological treatment of fetal tachycardia (FT) has been described in various publications. We present a study reviewing the necessity for treatment of FT, the regimens of drugs used in the last two decades and their mode of administration. The absence of reliable predictors of fetal hydrops (FH) has led most centers to initiate treatment as soon as the diagnosis of FT has been established, although a small minority advocate nonintervention. As the primary form of pharmacological intervention, oral maternal transplacental therapy is generally preferred. Digoxin is the most common drug used to treat FT; however, effectiveness remains a point of discussion. After digoxin, sotalol seems to be the most promising agent, specifically in atrial flutter and nonhydropic supraventricular tachycardia (SVT). Flecainide is a very effective drug in the treatment of fetal SVT, although concerns about possible pro-arrhythmic effects have limited its use. Amiodarone has been described favorably, but is frequently excluded due to its poor tolerability. Verapamil is contraindicated as it may increase mortality. Conclusions on other less frequently used drugs cannot be drawn. In severely hydropic fetuses and/or therapy-resistant FT, direct fetal therapy is sometimes initiated. To minimize the number of invasive procedures, fetal intramuscular or intraperitoneal injections that provide a more sustained release are preferred. Based on these data we propose a drug protocol of sotalol 160 mg twice daily orally, increased to a maximum of 480 mg daily. Whenever sinus rhythm is not achieved, the addition of digoxin 0.25 mg three times daily is recommended, increased to a maximum of 0.5 mg three times daily. Only in SVT complicated by FH, either maternal digoxin 1 to 2mg IV in 24 hours, and subsequently 0.5 to 1 mg/day IV, or flecainide 200 to 400 mg/day orally is proposed. Initiating direct fetal therapy may follow failure of transplacental therapy.

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.

Alteration of human placental vascular tone by antiarrhythmic medications in vitro

INTRODUCTION

Antiarrhythmic medications are commonly used during pregnancy for treatment of maternal or fetal arrhythmias, but little is known about their effect on human placental vascular tone and, consequently, placental blood flow. The objective of this study was to evaluate the tone responses caused by antiarrhythmic medications in human placental vessels from normal term pregnancies in vitro.

METHODS AND RESULTS

Isolated human placental arteries and veins from uncomplicated term pregnancies incubated in Krebs'-bicarbonate under 5% oxygen/5% carbon dioxide/balance nitrogen (PO2 35 to 38 torr) were exposed to cumulative doses of quinidine, procainamide, lidocaine, flecainide, propranolol, amiodarone, verapamil, digoxin, and adenosine after submaximal contraction with 5-hydroxytryptamine. The study was conducted both in the presence and absence of endothelium. The addition of the tested medications caused a significant, dose-dependent relaxation of human placental arteries and veins except for adenosine, which induced a sustained, dose-dependent contraction of human placental vessels regardless of the presence or absence of tone. Removal of the endothelium did not alter these responses.

CONCLUSIONS

Based on these results, the medications tested should have no decremental effect on placental blood flow, with the possible exception of adenosine, which causes significant, dose-dependent contraction of human placental vessels in vitro. Should similar contraction be present in vivo, it may have an adverse effect on the fetus when administering adenosine to pregnant women at term or during labor.

The efficacy of flecainide versus digoxin in the management of fetal supraventricular tachycardia

Fetal supraventricular tachycardia (SVT) can be successfully treated transplacentally, but in cases where fetal hydrops develops there is considerable morbidity and mortality. The present study was carried out to establish whether the introduction of flecainide altered obstetric management and fetal outcome. A retrospective analysis took place of 51 singleton pregnancies which were referred to the division of prenatal diagnosis because of fetal tachycardia between 1982 and 1993. SVT was documented in 50 out of 51 fetuses, one of which displayed a combination of extensive rhabdomyomas and severe hydrops and died shortly after referral. In the other fetus ventricular tachycardia was diagnosed. Of the remaining 49 fetuses, 14 did not receive any prenatal treatment, but nine needed postnatal treatment. Transplacental treatment of SVT took place in 35 fetuses, of which 22 presented without hydrops and 13 with hydrops. These subsets differed significantly with respect to restoration of normal sinus rhythm (73% vs. 30%; p < 0.001) and mortality (0% vs. 46%; p < 0.001). Digoxin was effective in restoring sinus rhythm in 55 per cent of the non-hydropic fetuses but in only eight per cent of the hydropic fetuses. Flecainide was effective in restoring sinus rhythm in all non-hydropic fetuses where digoxin treatment failed, and in 43 per cent of hydropic fetuses. Administration of flecainide resulted in a significantly reduced mortality (p < 0.001) compared with digoxin treatment. No adverse effects were seen. Postnatal anti-arrhythmic treatment was necessary in 23 infants. Treatment could be withdrawn within one year in all cases but one.

Medical fetal therapy

Medical fetal therapy describes any therapy in which a pharmacological agent is administered to a woman or her fetus in order to avoid or alleviate fetal disease. Treatment of the fetus with blood products or injection of other agents can also be considered to be medical fetal therapy. This chapter reviewed the application of medical fetal therapy to the prevention of NTDs, treatment of endocrinological and metabolic disorders, such as CAH, thyroid disease and others, and the medical management of cardiac arrhythmias. Several haematological disorders and reviews of recent advances in genetic manipulation involving the use of stem-cell implantation were discussed. The field of medical fetal therapy has been extremely exciting and continues to evolve at a rapid pace. No doubt, future advances involving genetic manipulation or the use of molecular genetic techniques for diagnosis will continue to keep this field at the forefront of treatment and prevention of fetal disorders.

Management outcome and follow-up of fetal tachycardia

OBJECTIVES

The aim of this study was to evaluate fetal tachycardia and the efficacy of maternally administered antiarrhythmic agents and the effect of this therapy on delivery and postpartum management.

BACKGROUND

Sustained fetal tachycardia is a potentially life-threatening condition in which pharmacologic therapy is reported to be effective. There is ongoing discussion about optimal management.

METHODS

A group of 51 patients with M-mode echocardiographically documented fetal tachycardia was studied retrospectively.

RESULTS

Thirty-three fetuses had supraventricular tachycardia; 15 had atrial flutter; 1 had two episodes of both; and 2 had ventricular tachycardia. Fetal hydrops was seen in 22 patients. Thirty-four fetuses received maternal therapy with either digoxin or flecainide as the first administered drug (additional drugs were given in 12). Drug treatment was successful in establishing acceptable rhythm control in 82% (84% without, 80% with hydrops). In the latter group the median number of drugs and number of days to conversion were higher. Three patients with fetal hydrops died. In 50% of cases, tachycardia reappeared at delivery: 9 neonates presented with atrial flutter, 14 with supraventricular tachycardia and 1 with ventricular tachycardia. Seventy-eight percent of the group had pharmacologic therapy by 1 month of age and 14% by 3 years.

CONCLUSIONS

Fetal tachycardia can be treated adequately in the majority of patients, even in the presence of hydrops, and therefore emergency delivery might not be indicated. Digoxin and flecainide were drugs of first choice and produced no serious adverse effects in this series of patients. The majority of patients do not require prolonged therapy.

Flecainide distribution, transplacental passage, and accumulation in the amniotic fluid during the third trimester of pregnancy

OBJECTIVE

To study the disposition of flecainide acetate and its transplacental passage (both into the fetus and in the amniotic fluid) during the third trimester of pregnancy.

DATA SOURCES

Reference articles and books are identified in the text. A literature review is presented.

CASE SUMMARY

Flecainide distribution, transplacental passage, and accumulation into the amniotic fluid were studied in a patient at term presenting with a fetal supraventricular tachycardia diagnosed at 33 4/7 weeks of gestation. The fetal tachycardia was accompanied by cardiac failure with placental anasarca and hydramnios. Flecainide 100 mg po bid was prescribed initially; by the time of delivery, the dosage had been decreased to 50 mg bid. At delivery day (39 5/7 weeks), the pharmacokinetics of total flecainide were studied at plateau.

DATA SYNTHESIS

The concentrations of flecainide at birth in fetal and maternal blood and in amniotic fluid were 235.4, 241.2, and 6426.5 micrograms/L, respectively. Calculation of a fetomaternal blood accumulation ratio of 0.97 showed that, at this gestational age, flecainide penetrates the placental membrane easily without accumulation in fetal blood. In contrast, the concentration of flecainide in amniotic fluid was approximately 27-fold that measured in maternal peripheral blood. Our results suggest the following: (1) close to term, the metabolic clearance (fetal hepatic clearance) of flecainide offers a high yield and its excretion by the fetal kidney is efficient; (2) given that amniotic fluid is constantly swallowed, it seems that, in contrast to what is seen in adults (relative oral bioavailability > or = 95 percent), the oral bioavailability of flecainide is possibly low in the fetus at term or close to term; under such circumstances, the drug would accumulate passively within the gestational sac; and (3) an alternative explanation is that the concentration in the fetus is, in part, the result of both transplacental crossing of the drug and reabsorption orally from the amniotic fluid.

CONCLUSIONS

The regular therapeutic monitoring of flecainide is necessary and sufficient in the mother as the concentrations found appear to accurately reflect the degree of fetal accumulation. Because previous studies in infants and children have indicated few toxic adverse effects attributed to flecainide, it appears that the risk to a sucking infant of ingesting toxic amounts of flecainide in human breast milk is very low. Finally, the child of the patient described here has normal initial growth and development at the present time. The transplacental penetration of a drug can be considered, according to gestational age and the disorder being treated, as being of no consequence, dangerous, or desirable. Flecainide appears to fall into this last category.

New antiarrhythmic drugs in pediatric use: amiodarone

Amiodarone, a class III antiarrhythmic agent, prolongs action potential duration and refractoriness of all cardiac structures. The drug is more rapidly metabolized in pediatric patients than in adults, but its kinetics are still unique compared with other drugs. Due to the unusual pharmacokinetic characteristics of amiodarone, treatment has to be started by administering loading doses, and there is a significant delay both in the achievement of the full anti-arrhythmic effect and in the development of side effects. Amiodarone is a highly effective agent in pediatric patients with automatic and reentrant supraventricular tachycardia as well as in refractory atrial flutter. Efficacy in ventricular tachycardia has been shown to be variable depending on the underlying anatomical substrate. The incidence of side effects is lower than that observed in adult studies with similar duration of therapy but their incidence is still significant. Amiodarone treatment is associated with a significant risk of proarrhythmic effects, requiring hospitalization of the patient during the loading period.

Flecainide acetate for treatment of tachyarrhythmias in children: review of world literature on efficacy, safety, and dosing

A review of all published experience with flecainide in infants, children, and fetuses was performed to evaluate the appropriate place of the drug in pediatric practice and to determine dosing guidelines. A total of 704 case references was generated. Flecainide appeared to be safe (no deaths with usual oral dosing, < 1% serious proarrhythmia) and effective (73% to 100% control, depending on mechanism) in children with supraventricular tachycardia. The drug was very effective for treatment of fetal tachyarrhythmias. Flecainide may not be safe for children who have structurally abnormal hearts and atrial flutter or ventricular arrhythmias. The safety of flecainide for patients with ventricular arrhythmias and normal hearts requires further investigation. Pharmacokinetic data reveal an age-dependent change in elimination half-life. Patients younger than 1 year of age have a plasma elimination half-life that is similar to that in children older than 12 years (i.e., 11 to 12 hours). Children aged 1 to 12 years have a mean elimination half-life of 8 hours. The effective flecainide dose is 100 to 200 mg/m2/day or 1 to 8 mg/kg/day. Toxicity may occur with doses in excess of these ranges, especially when high doses are accompanied by low serum trough levels. Milk blocks flecainide absorption, and toxicity may become manifest when milk products are removed from the diet.

Clinical and pharmacologic study of fetal supraventricular tachyarrhythmias

The purpose of this study was to evaluate the efficacy of maternal digoxin administration in 16 cases of fetal supraventricular tachyarrhythmia diagnosed by fetal echocardiography; cardiac anatomy was normal in all cases. The retrospective analysis included nine mothers who received digoxin orally in most cases, with control of the arrhythmia in two fetuses. The addition of amiodarone (five cases) and propranolol (two cases) yielded two successes with amiodarone. The therapeutic regimen of digoxin was then modified on the basis of poor response to orally administered digoxin. In the prospective study, digoxin was administered intravenously to seven mothers according to a standard protocol; high doses (1 to 2 mg intravenously) were prescribed for the first 24 hours and intravenous digoxin therapy was maintained for at least 5 days, depending on the fetal response. Digoxin pharmacokinetic studies of four mothers showed an increased plasma clearance and reduced elimination half-life. Digoxin controlled the five supraventricular tachycardias (with hydrops in four cases). Maternal flecainide therapy restored sinus rhythm in two cases of atrial flutter. Our prospective study emphasizes the efficacy and safety for the fetus and the mother of intravenously administered digoxin as a first-choice drug in the treatment of supraventricular tachyarrhythmias. Flecainide may be a promising second-choice drug but requires further clinical investigation. Amiodarone and propranolol seem to be ineffective.

Current concepts of fetal therapy

The development of fetal diagnostic techniques has facilitated the analysis of pathological conditions in abnormal fetuses. This has led to systematic fetal therapy for such diseases as fetal hydronephrosis and fetal struma. In this report, general characteristics and problems of fetal therapy are discussed and several representative diseases that have been treated by surgical and pharmaceutical methods are outlined.