Repeated intravascular treatment with amiodarone in a fetus with refractory supraventricular tachycardia and hydrops fetalis

Refractory Fetal Supraventricular Tachycardia with Hydrops Successfully Converted by Intraperitoneal Flecainide in the Fetus: A Case Report

INTRODUCTION

Supraventricular tachycardia is the most common fetal tachyarrhythmia and if persistent often associated with fetal hydrops which can cause intrauterine and neonatal death.

CASE PRESENTATION

We present a case of early second trimester supraventricular tachycardia in a hydropic fetus, initially refractory to transplacental treatment.

CONCLUSION

The supraventricular tachycardia was successfully treated when supplemented with intraperitoneal flecainide in the fetus.

Fetal dysrhythmias

Fetal dysrhythmias are common abnormalities, usually manifesting as irregular rhythms. Although most irregularities are benign and caused by isolated atrial ectopics, in a few cases, rhythm irregularity may indicate partial atrioventricular block, which has different etiological and prognostic implications. We provide a flowchart for the initial management of irregular rhythm to help select cases requiring urgent specialist referral. Tachycardias and bradycardias are less frequent, can lead to hemodynamic compromise, and may require in utero therapy. Pharmacological treatment of tachycardia depends on the type (supraventricular tachycardia or atrial flutter) and presence of hydrops, with digoxin, flecainide, and sotalol being commonly used. An ongoing randomized trial may best inform about their efficacy. Bradycardia due to blocked bigeminy normally resolves spontaneously, but if it is due to established complete heart block, there is no effective treatment. Ongoing research suggests hydroxychloroquine may reduce the risk of autoimmune atrioventricular block. Sinus bradycardia (rate <3rd centile) may be a prenatal marker for long-QT syndrome.

Successful in utero transesophageal pacing for severe drug-resistant tachyarrhythmia

Sustained fetal tachyarrhythmia can evolve into a life-threatening condition in 40% of cases when hydrops develops, with a 27% risk of perinatal death. Several antiarrhythmic drugs can be given solely or in combination to the mother to achieve therapeutic transplacental concentrations. Therapeutic failure could lead to progressive cardiac insufficiency and restrict therapeutic options to either elective delivery or direct fetal administration of antiarrhythmic drugs, which may increase the risk of death. We report for the first time successful fetal transesophageal pacing to treat a hydropic fetus with drug-resistant tachyarrhythmia.

Fetal dysrhythmias

Fetal cardiac dysrhythmias are potentially life-threatening conditions. However, intermittent extrasystoles, which are frequently encountered in clinical practice, do not require treatment. Sustained forms of brady- and tachyarrhythmias might require fetal intervention. Fetal echocardiography is essential not only to establish the diagnosis but also to monitor fetal response to therapy. In the last decade, improvements in ultrasound methodology and new diagnostic tools have contributed to better diagnostic accuracy and to a greater understanding of the electrophysiological mechanisms involved in fetal cardiac dysrhythmias. The most common form of supraventricular tachycardia - that caused by an atrioventricular re-entry circuit - should be differentiated from other forms of tachyarrhythmias, such as atrial flutter and atrial ectopic tachycardia. Ventricular tachycardia is rare in the fetus. Sustained tachycardias, intermittent or not, might be associated with the development of congestive heart failure and hydrops fetalis. Prompt treatment with either anti-arrhythmic drugs or delivery must be considered. Persistent fetal bradycardias associated with complete heart block are also potentially dangerous, whereas bradyarrhythmia due to blocked ectopy is well tolerated in pregnancy. Heart block can be associated with maternal anti-Ro/La autoantibodies or develop in fetuses with left atrial isomerism or with malformations involving the atrioventricular junction. The treatment of fetuses with immune-mediated heart block remains debatable. The use of antenatal steroid therapy is not widely accepted and there is concern over the risks and benefits of its use in the fetus. Direct fetal cardiac pacing has rarely been attempted.

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.

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.

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.

Role of amiodarone in the treatment of fetal supraventricular tachyarrhythmias and hydrops fetalis

We report three consecutive hydropic fetuses with fetal tachyarrhythmias treated with amiodarone-two in combination with digoxin and one with digoxin, procainamide, and propranolol. Sinus rhythm was achieved in one case and ventricular rate control was achieved in two cases. All fetuses treated with amiodarone gradually improved. Observed side effects of amiodarone were a maternal rash in one mother and transient neonatal hypothyroidism in one infant. We conclude that amiodarone might be effective and safe for fetal tachyarrhythmias and impending hydrops. The small number of patients suggests that a multicenter cooperative approach is required in order to determine if this is correct.

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.

Flecainide in the intrauterine treatment of fetal supraventricular tachycardia

OBJECTIVES

To assess the efficacy of flecainide in the intrauterine treatment of fetal supraventricular tachycardia (SVT) with 1 : 1 atrioventricular conduction.

DESIGN

Twenty fetuses (21-35 weeks of gestation) with SVT ranging between 215 and 280 bpm were analyzed retrospectively. Fetuses received flecainide and digoxin as either first, second or third line therapy. Intracardiac blood flow, venous Doppler waveforms and cardiotocograms were evaluated before and after drug induced conversion to sinus rhythm.

RESULTS

After initiation of combined flecainide and digoxin therapy, the median time interval until final conversion to sinus rhythm was 5 days (range, 0-14 days). The majority of fetuses (n = 15; 75%) converted to sinus rhythm within 7 days of treatment, whereas the remaining five (25%) showed initial reduction of the heart rate to 160-215 bpm over several days, with restoration of a triphasic venous blood flow pattern before late conversion within 7-14 days after initiation of flecainide treatment. One of these fetuses showed a decrease in fetal heart rate to 160-190 bpm without conversion to sinus rhythm but with resolution of hydrops. All fetuses survived.

CONCLUSIONS

Flecainide is safe and highly effective in the intrauterine treatment of hydropic fetuses with supraventricular tachycardia. Conversion into sinus rhythm can be expected 72 h after initiation of therapy but may take up to 14 days. Therefore therapy should be continued beyond 72 h, especially when an initial decrease of fetal heart rate is observed which may represent an early therapeutic response.

The effects of amiodarone on the thyroid

Amiodarone is a benzofuranic-derivative iodine-rich drug widely used for the treatment of tachyarrhythmias and, to a lesser extent, of ischemic heart disease. It often causes changes in thyroid function tests (typically an increase in serum T(4) and rT(3), and a decrease in serum T(3), concentrations), mainly related to the inhibition of 5'-deiodinase activity, resulting in a decrease in the generation of T(3) from T(4) and a decrease in the clearance of rT(3). In 14-18% of amiodarone-treated patients, there is overt thyroid dysfunction, either amiodarone-induced thyrotoxicosis (AIT) or amiodarone-induced hypothyroidism (AIH). Both AIT and AIH may develop either in apparently normal thyroid glands or in glands with preexisting, clinically silent abnormalities. Preexisting Hashimoto's thyroiditis is a definite risk factor for the occurrence of AIH. The pathogenesis of iodine-induced AIH is related to a failure to escape from the acute Wolff-Chaikoff effect due to defects in thyroid hormonogenesis, and, in patients with positive thyroid autoantibody tests, to concomitant Hashimoto's thyroiditis. AIT is primarily related to excess iodine-induced thyroid hormone synthesis in an abnormal thyroid gland (type I AIT) or to amiodarone-related destructive thyroiditis (type II AIT), but mixed forms frequently exist. Treatment of AIH consists of L-T(4) replacement while continuing amiodarone therapy; alternatively, if feasible, amiodarone can be discontinued, especially in the absence of thyroid abnormalities, and the natural course toward euthyroidism can be accelerated by a short course of potassium perchlorate treatment. In type I AIT the main medical treatment consists of the simultaneous administration of thionamides and potassium perchlorate, while in type II AIT, glucocorticoids are the most useful therapeutic option. Mixed forms are best treated with a combination of thionamides, potassium perchlorate, and glucocorticoids. Radioiodine therapy is usually not feasible due to the low thyroidal radioiodine uptake, while thyroidectomy can be performed in cases resistant to medical therapy, with a slightly increased surgical risk.

Effects of amiodarone administration during pregnancy on neonatal thyroid function and subsequent neurodevelopment

Amiodarone, a benzofuranic derivative, iodine-rich drug, has been used in pregnancy for either maternal or fetal tachyarrhythmias. Amiodarone, its main metabolite (desethylamiodarone) and iodine are transferred, albeit incompletely, through the placenta, resulting in a relevant fetal exposure to the drug and iodine overload. Since the fetus acquires the capacity to escape from the acute Wolff-Chaikoff effect only late in gestation, the iodine overload may cause fetal/neonatal hypothyroidism and goiter. Among the reported 64 pregnancies in which amiodarone was given to the mother, 11 cases (17%) of hypothyroidism in the progeny (10 detected at birth, 1 in utero) were reported, 9 non-goitrous (82%) and 2 (18%) associated with goiter. Hypothyroidism was transient in all cases, and only 5 infants were treated short-term with thyroid hormones. Only 2 newborns had transient hyperthyroxinemia, associated with low serum TSH concentrations in one. Neurodevelopment assessment of the hypothyroid infants, when carried out, showed in some instances mild abnormalities, most often reminiscent of the Non-verbal Learning Disability Syndrome; however, these features were also reported in some amiodarone-exposed euthyroid infants, suggesting that there might be a direct neurotoxic effect of amiodarone during fetal life. Breast-feeding was associated with a substantial ingestion of amiodarone by the infant, but in the few cases followed it did not cause changes in the newborn's thyroid function. In conclusion, amiodarone therapy during pregnancy may cause fetal/neonatal hypothyroidism and, less frequently, goiter. Thus, the use of amiodarone in pregnancy should be limited to maternal/fetal tachyarrhythmias which are resistant to other drugs or life-threatening. If amiodarone is used during gestation, a careful fetal/neonatal evaluation of thyroid function and morphology is warranted. It seems prudent to advise that fetal/neonatal hypothyroidism be treated, as soon as the diagnosis is made, even in utero, to avoid neurodevelopment abnormalities, although the latter may occur independently of hypothyroidism. If breast-feeding is allowed, careful evaluation of the infant's thyroid function and morphology is required because of the continuing exposure of the infant to the drug.

Digoxin, flecainide, and amiodarone transfer across the placenta and the effects of an elevated umbilical venous pressure on the transfer rate

Clinical observations suggest that flecainide might pass the placenta more easily than digoxin, and that its transfer is less disturbed in case of hydrops fetalis than that of digoxin. The purpose of the study was to compare the materno-fetal transplacental transfer of digoxin, flecainide, and amiodarone, another antiarrhythmic agent used in the treatment of fetal tachyarrhythmia, and to assess the effect of an elevated umbilical venous pressure (UVP) on the transfer rate. Isolated lobules of 16 human placentas were dually perfused after spontaneous delivery or caesarean section. The transplacental transfer (area under the curve in the maternal compartment [maternal AUC], area under the curve in the fetal compartment [fetal AUC], kinetic parameters) of digoxin, flecainide, and amiodarone was calculated after these drugs were added to the maternal circuit. In five experiments, the effect of increased UVP on the transplacental transfer rate was assessed by elevating the UVP by 10 cm H2O. Flecainide efflux out of the maternal compartment was significantly greater than that of digoxin (maternal AUC 57.4% +/- 5.1 %/min vs 73.9% +/- 1.5%/min), whereas the flecainide influx into the fetal circulation was smaller (fetal AUC 9.3% +/- 4.1%/min vs 11.5% +/- 2.0%/min). Only in 50% of the experiments were the smallest amounts of amiodarone detectable in the fetal compartment. An elevation of the UVP reduced the influx of digoxin and flecainide into the fetal compartment (fetal AUC) from 11.5% +/- 2.0%/min to 7.4% +/- 1.9%/min and from 9.3% +/- 4.1% to 4.7% +/- 1.4%/min, respectively. Materno-fetal transplacental transfer of digoxin, flecainide, and amiodarone decreases in this sequence. Fetal cardiac insufficiency accompanied by an elevation of the UVP might reduce the transplacental transfer of these drugs, although no significant difference could be found between the reduction of transfer of digoxin and flecainide.

Successful treatment of refractory supraventricular tachycardia by repeat intravascular injection of amiodarone in a fetus with hydrops

We report the case of a fetus with supraventricular tachycardia complicated by congestive heart failure and ascites. After failure of initial transplacental treatment, the injection of amiodarone into the umbilical vein combined with evacuation of ascites achieved conversion to sinus rhythm and restored cardiac function thus allowing pregnancy to go to term. This report suggests that direct fetal therapy by umbilical vein puncture and evacuation of effusions constitutes an effective treatment for supraventricular tachycardias with massive fetal hydrops which do not respond to transplacental treatment.

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.

Diffusion characteristics of placental preparations affect the digoxin passage across the isolated placental lobule

Our aim was to evaluate the isolated placental lobule to study maternofetal transplacental digoxin transfer and accumulation in placental tissue in vitro. Digoxin passage across the isolated lobule of 10 human placentas was calculated from repeated fetal and maternal perfusate samples, and placental tissue digoxin concentrations were measured at the end of the experiments. To determine the degree of overlap of the fetal and the maternal circulation, the antipyrine clearance was used. Digoxin disappearance from the maternal circuit was not significantly affected by the degree of overlap. In contrast, the increase of digoxin in the fetal compartment was significantly higher in "well-perfused" placentas (antipyrine clearance > 1.60 ml/min; n = 5) than in "malperfused" placentas (antipyrine clearance < 1.50 ml/min; n = 5) (end-feto to initial maternal digoxin ratio 0.44 +/- 0.08 vs. 0.30 +/- 0.08; p < 0.05), whilst the accumulation in placental tissue was higher in the latter group (0.45 +/- 0.07 vs. 0.62 +/- 0.10 ng/mg protein; p < 0.05). We conclude that the isolated placental lobule is suitable to quantify transplacental digoxin transfer in vitro, but the diffusion characteristics of each preparation have to be considered.

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.

Longitudinal study in 18 cases of fetal supraventricular tachycardia: Doppler echocardiographic findings and pathophysiologic implications

A longitudinal study was performed in nine nonhydropic and nine hydropic fetuses with supraventricular tachycardia (SVT). First, because of a lack of reference methods in utero, the validity of spatial (length and area) and temporal parameters for semiquantitative grading of atrioventricular (AV) valve regurgitation by color Doppler flow mapping and M-Q mode imaging was evaluated by a longitudinal intraindividual study before and after drug-induced cardioversion to sinus rhythm and by correlation with the severity of hydrops and the time required for complete remission of hydrops. Second, with the demonstration of AV valve incompetence and changes in venous blood flow velocity wave forms, new data were collected concerning chronic SVT in the fetus. AV valve incompetence occurred in eight fetuses: during SVT only in three severely hydropic fetuses, during sinus rhythm in one nonhydropic fetus, and in seven hydropic fetuses including those previously mentioned, where AV incompetence outlasted tachycardia. The length and area of the regurgitant jet as imaged by color Doppler flow mapping and the temporal duration of regurgitation in relation to the systolic phase as measured by M-Q mode continuously diminished intraindividually but with great interindividual differences in the time span required for complete remission, which ranged from 5 to 42 days. Pulsed-wave Doppler studies of blood flow in the inferior vena cava and left hepatic vein demonstrated normal biphasic forward flow with a systolic and a diastolic surge during sinus rhythm in all fetuses and in two instances also during SVT of 190 and 195 beats/min, respectively. In all cases a pulsatile reversal of blood flow with systolic forward flow and diastolic reverse flow was observed during tachycardia greater than 220 beats/min. Thus the presence of functional AV valve incompetence as a result of annular enlargement seems to be a sign of SVT-induced "cardiomyopathy" during fetal life. AV valve incompetence during SVT was always associated with extremely severe hydrops and seemed to indicate the most severe degree of ventricular dysfunction, which could influence the selection of antiarrhythmic drugs. After termination of SVT, severe AV valve insufficiencies also occurred in other cases of hydrops, probably because of the markedly increased diastolic filling distending the already enlarged annular ring. The observed great interindividual differences in time required for disappearance of AV valve incompetence and hydrops could be explained by a different state of progression of tachycardia-induced "cardiomyopathy" at the time of drug-induced cardioversion.(ABSTRACT TRUNCATED AT 400 WORDS)

Umbilical venous pressure in nonimmune hydrops fetalis: correlation with cardiac size

OBJECTIVES

Our objectives were to examine the relationship between umbilical venous pressure and cardiac size in nonimmune hydrops fetalis and to assess the role of cardiac failure in the pathogenesis of the disease.

STUDY DESIGN

Fourteen fetuses with nonimmune hydrops fetalis were investigated in a tertiary referral unit with high-resolution ultrasonography, echocardiography, and fetal blood sampling. Fetal heart size was assessed by measurement of the cardiothoracic ratio. Umbilical venous pressure was measured at the time of fetal blood sampling with a fluid-filled system.

RESULTS

The 10 fetuses with elevated umbilical venous pressures had significantly increased cardiothoracic ratios (p = 0.02). These fetuses also had ascites. Four other fetuses had normal-sized hearts, normal umbilical venous pressures, and no ascites. There was a linear relationship between cardiothoracic ratio and umbilical venous pressure (r = 0.75, p = 0.003).

CONCLUSION

Measurement of umbilical venous pressure validates cardiothoracic ratio as a noninvasive assessment of cardiac function in nonimmune hydrops.

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.

Amiodarone. An overview of its pharmacological properties, and review of its therapeutic use in cardiac arrhythmias

Amiodarone, originally developed over 20 years ago, is a potent antiarrhythmic drug with the actions of all antiarrhythmic drug classes. It has been successfully used in the treatment of symptomatic and life-threatening ventricular arrhythmias and symptomatic supraventricular arrhythmias. In patients with left ventricular dysfunction amiodarone does not usually produce any clinically significant cardiodepression and the drug has relatively high antiarrhythmic efficacy. Preliminary studies indicate that amiodarone may have a beneficial effect on mortality and survival in certain groups of patients with ventricular arrhythmias, an action probably related to both its antiarrhythmic and antifibrillatory effects. The adverse effect profile of amiodarone is diverse, involving the cardiac, thyroid, pulmonary, hepatic, gastrointestinal, ocular, neurological and dermatological systems. Interstitial pneumonitis and hepatitis are potentially fatal, but the vast majority of adverse events are less serious, and some may be dose dependent. Pretreatment monitoring, regular assessments and the use of minimum effective doses are, therefore, necessary. Thus, with appropriate monitoring to control its well recognised adverse effects amiodarone has an important place as an effective 'broad spectrum' antiarrhythmic drug which has, so far, been used when other treatments have proved ineffective. More recent preliminary data also suggest that it may also have a beneficial effect in the prevention of sudden death in some patients.

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.

Determination of digoxin in the blood of pregnant women, fetuses and neonates before and during anti-arrhythmic therapy, using four immunochemical methods

Four immunochemical methods for digoxin assay were used to analyse control samples, 33 amniotic fluid samples, 57 samples from digitalis-treated, non-pregnant women, 90 pregnancy serum samples, and 72 samples of fetal or neonatal serum with or without digoxin therapy. One hundred and five samples were also submitted to ultrafiltration before analysis. Three methods (RIA, TDX, AMERLITE) showed practically the same precision, while the precision of the DELFIA was markedly inferior. In the analysis of serum samples from digoxin-treated, non-pregnant women, RIA and TDX gave practically the same values, whereas AMERLITE and DELFIA gave significantly higher values. Pregnancy serum and fetal serum contain "digoxin-like immunoreactive factors", and the qualitative and quantitative effects of these interfering factors are different for each of the four methods. The greatest sensitivity to "digoxin-like immunoreactive factors" is shown by TDX and DELFIA, while the lowest interference by "digoxin-like immunoreactive factors" is found in the analysis of ultrafiltered samples, using the TDX method. The composition of the "digoxin-like immunoreactive factors" in pregnancy serum and in fetal serum is altered by digoxin therapy, and these changes have different effects on the various analytical methods. The concentration of "digoxin-like immunoreactive factors" in the serum of fetuses receiving digoxin is markedly lower than that of healthy fetuses. For the reliable monitoring of digoxin therapy in the maternal and fetal circulation, the blood samples must be submitted to ultrafiltration before analysis.