Tertiary Centre For Fetal Cardiology Research Articles

Impact of early detection and steroid treatment on fetal ventricular heart rate and pacemaker implantation in anti-Ro/SSA positive congenital heart block.

We investigated the effects of timing of detection and transplacental fluorinated steroid treatment on ventricular heart rate (HR) and age at pacemaker implantation in fetal third-degree atrioventricular block (AVB). Twenty-five of 31 fetuses diagnosed with Ro/SSA autoantibody-positive AVB II-III at our tertiary fetal cardiology center (2000-2020) and AVB III as final feto-neonatal outcome were reviewed. AVB was detected approximately 5 weeks earlier in pregnancy if followed in a surveillance program compared to cases referred from primary care for bradycardia (20.6 [2.3] [mean (SD)] vs. 25.4 [3.2] weeks, p = 0.001). AVB detected before 24 weeks had higher HR than those detected later in gestation (63.3 [6.9] vs. 57.2 [6.9] bpm, p = 0.042), with a larger proportion having HR >60 bpm (80% vs. 33%, p = 0.041). The 17/25 cases that received treatment with fluorinated steroid were diagnosed earlier in gestation, with higher HR at diagnosis (61.7 [7.1] vs. 54.7 [6.3] bpm, p = 0.026), 1-2 weeks after diagnosis/treatment start, and before birth (65.4 [12.4] vs. 54.9 [5.7] bpm, p = 0.030) than untreated cases. Overall, 11 cases were commenced on betamimetics: three at diagnosis and eight at or after the examination made 1-2 weeks after diagnosis/treatment start, without any HR improvement. Two of 24 surviving babies were born preterm, and 4/24 received a neonatal pacemaker. Age at pacemaker implantation correlated significantly with HR before birth (Spearman R 0.57, p = 0.004), and fetuses with HR >60 bpm had a higher rate of pacemaker-free survival at three (90% vs. 40%, p = 0.018) and 12 months of age (80% vs. 13%, p = 0.002). The same trend was observed in pacemaker-free survival at 3 months of age in fluorinated steroid-treated compared to untreated cases (71% vs. 38%, ns). Our data confirm that AVB III detected earlier in gestation have a higher HR, and suggest that this higher HR can be successfully maintained to the end of gestation in cases treated with fluorinated steroids. Fetuses with HR >60 bpm before birth had a lower rate of pacemaker implantation at 3 and 12 months of age.

Tetralogy of Fallot in the fetus - from diagnosis to delivery. 18-year experience of a tertiary Fetal Cardiology Center.

Tetralogy of Fallot (TOF) is a common congenital heart disease but very heterogeneous in terms of detailed cardiac anatomy, associated malformations, and genetic anomalies, especially when assessed prenatally. We aimed to analyze the clinical spectrum of TOF in the prenatal period, including detailed cardiac morphology, coexisting anomalies, and their impact on short-term neonatal outcome. We also assessed changing trends in the prenatal diagnostic workup of TOF. A retrospective cohort study including fetuses diagnosed with TOF between 2002 and 2019 was conducted in a tertiary Fetal Cardiology Center. Medical records and echocardiographic examinations were reviewed to collect demographic, sonographic, and genetic data. Among 326 TOF fetuses, 237 (73%) had pulmonary stenosis (TOF-PS), 72 (22%) pulmonary atresia (TOF-PA), and 17 (5%) absent pulmonary valve (TOF-APV). The yearly number of diagnoses increased during the study period, with decreasing fetal age at the time of diagnosis. Extracardiac malformations were found in 172 (53%) fetuses, cardiovascular malformations in 159 (49%), and genetic anomalies in 99 (39% of the tested group). Hypoplastic thymus, right aortic arch, and polyhydramnios were sonographic markers of microdeletion 22q11. Left-to-right ductal flow was predictive of postnatal ductal dependency. The perinatal outcome was dependent on the presence of associated anomalies and disease subtype, with TOF-APV having the worst prognosis. Extracardiac and genetic anomalies are common in fetuses with TOF, and, together with disease subtype and ductal flow assessment, they impact the perinatal management and outcomes. Genetic testing with array comparative genomic hybridization should be offered in all cases.

Reference Ranges for Pulsed-Wave Doppler of the Fetal Cardiac Inflow and Outflow Tracts from 13 to 36 Weeks’ Gestation

Doppler assessment of ventricular filling and outflow tract velocities is an integral part of fetal echocardiography, to assess diastolic function, systolic function, and outflow tract obstruction. There is a paucity of prospective data from a large sample of normal fetuses in the published literature. The authors report reference ranges for pulsed-wave Doppler flow of the mitral valve, tricuspid valve, aortic valve, and pulmonary valve, as well as heart rate, in a large number of fetuses prospectively examined at a single tertiary fetal cardiology center. The study population comprised 7,885 fetuses at 13 to 36weeks' gestation with no detectable abnormalities from pregnancies resulting in normal live births. Prospective pulsed-wave Doppler blood flow measurements were taken of the mitral, tricuspid, aortic, and pulmonary valves. The fetal heart rate was recorded at the time of each assessment. Regression analysis, with polynomial terms to assess for linear and nonlinear contributors, was used to establish the relationship between each measurement and gestational age. The measurement for each cardiac Doppler measurement was expressed as a Z score (difference between observed and expected values divided by the fitted SD corrected for gestational age) and percentile. Analysis included calculation of gestation-specific SDs. Regression equations are provided for the cardiac inflow and outflow tracts. This study establishes reference ranges for fetal cardiac Doppler measurements and heart rate between 13 to 36weeks' gestation that may be useful in clinical practice.

Impact of prospective measurement of outflow tracts in prediction of coarctation of the aorta

Prenatal diagnosis of coarctation of the aorta (CoA) is associated with reduced mortality and morbidity, however, accurate prenatal prediction remains challenging. To date, studies have used retrospective measurements of the outflow tracts to evaluate their potential to predict CoA. Our primary objective was to evaluate prospectively acquired measurements of the outflow tracts in fetuses with prenatally suspected CoA. A secondary aim was to report the postnatal prevalence of bicuspid aortic valve in this cohort. Pregnancies with suspicion of isolated CoA and with a minimum of 6 months' postnatal follow-up available were identified from the cardiac database of a tertiary fetal cardiology center in the UK, between January 2002 and December 2017. Measurement of the aortic valve, pulmonary valve, distal transverse aortic arch (DTAA) and arterial duct (AD) diameters were undertaken routinely in fetuses with suspected CoA during the study period. Z-scores were computed using published reference ranges based on > 7000 fetuses from our own unit. Of 149 pregnancies with prenatally suspected CoA included in the study, CoA was confirmed within 6 months after birth in 77/149 (51.7%) cases. DTAA diameter Z-score and the Z-score of second-trimester DTAA/AD diameter ratio were smaller in fetuses with postnatally confirmed CoA than those in false-positive cases (-2.8 vs -1.9; P = 0.039 and -3.13 vs -2.61; P = 0.005, respectively). Multiple regression analysis demonstrated that the Z-scores of DTAA and AD diameters were the only significant predictors of postnatal CoA (P = 0.001). Bicuspid aortic valve was identified in 30% of the false-positive cases. Measurement of DTAA and AD diameter Z-scores can be used to ascertain risk for postnatal CoA in a selected cohort. The high incidence of bicuspid aortic valve in false-positive cases merits further study with respect to both etiology and longer-term significance. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd.

Benefits of fetal echocardiographic surveillance in pregnancies at risk of congenital heart block: single-center study of 212 anti-Ro52-positive pregnancies.

Assuming that autoimmune congenital heart block (CHB) is a progressive disease amenable to therapeutic modulation, we introduced a surveillance program for at-risk pregnancies with the dual aim of investigating if fetal atrioventricular block (AVB) could be detected and treated before becoming complete and irreversible, and to establish the incidence of AVB I, II and III in a large prospective cohort. This was a prospective study of 212 anti-Ro52 antibody-exposed pregnancies at risk of fetal AVB that were followed weekly between 18 and 24 weeks' gestation at our tertiary fetal cardiology center from 2000 to 2015. A 12-lead electrocardiogram (ECG) was recorded within 1 week after birth. Fetal Doppler atrioventricular (AV) intervals were converted to Z-scores using reference standard values derived from normal pregnancies. Each fetus was represented by the average value of the two recordings, obtained at two consecutive visits, which resulted in the longest AV interval. AV interval values were classified into normal AV conduction (Z-score ≤ 2.0) and three levels of delayed AV conduction: Z-score > 2.0 and ≤ 3.0, Z-score > 3.0 and ≤ 4.0, and Z-score > 4.0. AVB II or III developed in 6/204 (2.9%) pregnancies without a CHB history and 1/8 (12.5%) of those with a CHB history. AV intervals > 2 and ≤ 3, > 3 and ≤ 4, and > 4 were detected in 16.0%, 7.5% and 2.8% of cases, respectively, and were related to the PR interval on 185 available ECGs. Three of the five cases with AVB III and one of two cases with 2:1 AVB II developed within 1 week of AV interval Z-score of 1.0, 1.9, 2.8 and 1.9, respectively. Transplacental treatment with betamethasone was associated with restoration of 1:1 AV conduction in the two fetuses with AVB II, with a better long-term result (normal ECG vs AVB I or II) observed in the case in which treatment was started within 1 week after AVB developed. Betamethasone treatment did not reverse AVB III, although a temporary effect on AV conduction was observed in 1/5 cases. Notably, the three cases in which treatment was started within 1 week after AVB III development responded with a higher ventricular rate than the other two cases and did not require pacemaker implantation until a later age (2-5 years vs 1.5-2 months). Fetal AV interval is a poor predictor of CHB progression, but CHB surveillance still allows detection of fetuses with AVB II or III shortly after its development, allowing for timely treatment initiation and potentially better outcome. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd.

EP07.07: Atrioventricular septal defect: what can we predict for neonates based on prenatal diagnosis – retrospective analysis of 97 cases from a tertiary centre for fetal cardiology

EP07.07: Atrioventricular septal defect: what can we predict for neonates based on prenatal diagnosis – retrospective analysis of 97 cases from a tertiary centre for fetal cardiology

EP04.04: Double outlet right ventricle: what can we predict for neonates based on prenatal diagnosis–retrospective analysis of 39 cases from tertiary centre for fetal cardiology

EP04.04: Double outlet right ventricle: what can we predict for neonates based on prenatal diagnosis–retrospective analysis of 39 cases from tertiary centre for fetal cardiology

Fetal aortic valve stenosis: a critique of case selection criteria for fetal intervention.

Selection of fetuses with aortic stenosis (AS) for prenatal intervention has been influenced by published scoring systems. This study aimed to test these scoring systems by retrospective application to consecutive cases of fetal AS. Retrospective analysis of the echocardiographic findings of 31 consecutive fetuses with AS evaluated at a tertiary fetal cardiology centre. Published 'eHLHS' scores and threshold scores were applied to the group and compared to postnatal management, in terms of biventricular repair versus single ventricle palliation. Thirty-one fetuses were identified with AS, and eHLHS was identified in 17 at the initial echocardiogram. No fetus with a full eHLHS score (3/3 or 4/4) achieved a biventricular repair. Three fetuses had a favourable threshold score (≥4), one of whom had a successful biventricular outcome. Seven fetuses had an unfavourable threshold score (<4) and underwent a univentricular pathway. The eHLHS score is a reliable predictor for the progression to HLHS at term. The score identifies those who would achieve a biventricular repair postnatally without prenatal intervention. A minority of fetuses with favourable threshold scores may achieve a biventricular repair postnatally without prenatal intervention, but eHLHS and an unfavourable threshold score (<4) predict a single ventricle pathway postnatally.

Outcome after prenatal diagnosis of hypoplastic left heart syndrome (HLHS) in south wales over a 7 year period

ObjectiveTo assess the rate of antenatal detection of hypoplastic left heart syndrome (HLHS) and its outcome antenatally and postnatally. This review was undertaken to improve counselling and provide better surgical...

Outcome of all antenatally diagnosed cases of complete atrio-ventricular septal defect (CAVSD) in south wales over a 7 year period: impact of associated chromosomal anomalies

ObjectiveTo assess the rate of chromosomal problems with complete atrio-ventricular septal defect. This study was undertaken to improve counselling and provide better information for expecting parents in the future.MethodsAll cases...

An echocardiographic study of diagnostic accuracy, prediction of surgical approach, and outcome for fetuses diagnosed with discordant ventriculo-arterial connections

Our aims were to examine the diagnostic accuracy of prenatal diagnosis of concordant atrioventricular and discordant ventriculo-arterial connections, the accuracy of predictions made concerning the postnatal surgical approach, and a description of the different subtypes related to outcome. All fetuses were evaluated at a tertiary centre for fetal cardiology between January, 1994, and December, 2003. In this period, we identified congenitally malformed hearts in 1,835 fetuses, of whom 56 (3%) met the criterions of inclusion. Of the total, 30 (54%) had an intact ventricular septum, 9 (16%) had an associated ventricular septal defect, 7 (13%) had a ventricular septal defect and pulmonary stenosis, 1 (2%) had pulmonary stenosis and an intact ventricular septum, 8 (14%) had a ventricular septal defect and aortic coarctation, and 1 (2%) had coarctation of the aorta with an intact ventricular septum. All the discordant ventriculo-arterial connections were correctly identified. For associated ventricular septal defects, the diagnostic sensitivity was 96%, with specificity of 88%, positive predictive value of 85%, and negative predictive value of 97%. For aortic coarctation, the sensitivity was 100%, specificity 96%, positive predictive value 82%, and negative predictive value 100%. The prediction of the surgical approach was accurate in 41 of 48 cases (85%). For those fetuses with pulmonary stenosis and ventricular septal defect, the ratio of the diameters of the pulmonary trunk was shown to be helpful in predicting the possibility of an arterial switch as opposed to the Rastelli type of repair. Of the 49 liveborn infants, 46 were alive at 30 days (94%, with 95% confidence intervals from 83 to 99%), and 43 at one year (88%, 95% confidence intervals from 75 to 95%). Deaths were mainly related to the anatomy of the coronary arteries, and associated cardiac lesions.

OP04.09: Pulmonary blood supply in pulmonary atresia with ventricular septal defect: prenatal identification of systemic to pulmonary collateral arteries

Objective: To describe the antenatal findings of systemic to pulmonary collateral arteries (SPCA) in the setting of pulmonary atresia (PA) and ventricular septal defect (VSD) and the impact upon pregnancy management. Methods: Retrospective review of cases in tertiary fetal cardiology centre. All prenatally diagnosed cases of PA with VSD that presented between January 1997 and December 2004 were identified using hospital databases. Findings from prenatal echocardiography were compared to postnatal data, or autopsy findings in cases where pregnancy was terminated. Results: Of 4949 fetuses 29 (0.6%) had PA, 8 with an intact ventricular septum and 21 with a large VSD. Among those with a VSD, 8 had ‘tetralogy type’ anatomy with anterior deviation of the outlet septum and an overriding aorta: in 4 of these cases pulmonary blood supply was retrograde through the arterial duct and in 4 SPCA from the descending aorta were identified. In 3 of the 4 with SPCA despite absence of the arterial duct, central pulmonary arteries were identified. Pregnancy was continued in 2 cases while 2 underwent termination. In three cases the presence of SPCA was confirmed by cardiac catheterisation, post-mortem examination or postnatal echocardiography. Pregnancy was terminated in the fourth case and no post-mortem was performed. In the 2 live births we did not commence on prostaglandin E infusion. In one case, severe pulmonary stenosis rather than atresia was shown post-natally. In the remaining 13 cases with a VSD, PA was part of more complex anomalies and pulmonary blood supply was via the arterial duct in all. Conclusion: SPCA can be accurately identified prenatally with and without central pulmonary arteries. This allows precise description of pulmonary blood supply in the fetus with PA and VSD, thus helping prenatal counselling, pregnancy management and management of the newborn.

Dilated cardiomyopathy presenting during fetal life

To describe the echocardiographic features, underlying causes, and outcome of fetuses with dilated cardiomyopathy. A retrospective observational study between 1983 and 2003 at a tertiary centre for fetal cardiology. Affected fetuses were identified using a computerised database. We included fetuses with dilation and reduced systolic function of either the right ventricle, left ventricle, or both. We excluded fetuses with abnormal cardiac connections, arrhythmias, or stenosis of the aortic or pulmonary valves. In all, we identified 50 fetuses, born to 46 mothers. Of the fetuses, 24 had biventricular cardiomyopathy, 17 had isolated right ventricular cardiomyopathy, and 9 had isolated left ventricular cardiomyopathy. Two-thirds of the fetuses (32) were hydropic at some point during gestation. A cause of cardiomyopathy was identified in 37 cases (74 per cent). This was genetic or metabolic in 11 fetuses; infective in 11; fetal anaemia, without proven parvovirus infection, in 5; of cardiac origin in 5; and an association with renal disease in 5. In 10 cases (20 per cent), the pregnancy was terminated. Based on an intention to treat, the survival to delivery was 25 of 40 (62.5 per cent, 95 per cent confidence intervals from 46 to 77 per cent), at 28 days was 17 of 40 (42.5 per cent, 95 per cent confidence intervals from 27 to 59 per cent), and at 1 year was 15 of 40 (37.5 per cent, 95 per cent confidence intervals from 23 to 54 per cent). The overall survival of non-hydropic fetuses was 9 of 18 (50 per cent), compared to 6 of 32 (18 per cent) hydropic fetuses. Genetic, metabolic, infective, and cardiac diseases may present with dilated cardiomyopathy during fetal life. There is a high rate of spontaneous intra-uterine and early neonatal death. The prognosis is particularly poor for hydropic fetuses.

Detailed three-dimensional fetal echocardiography facilitated by an Internet link.

To assess whether a complete virtual cardiological examination can be achieved in stored three-dimensional volumes of the fetal heart, transmitted to a tertiary fetal cardiology center via the Internet. Thirty sequential normal singleton pregnancies were included in the study. Four cardiac volumes were acquired using a three-dimensional ultrasound system. The volumes were sent via the Internet to a tertiary fetal cardiology center, where a detailed fetal cardiac examination was attempted using the three-dimensional volumetric dataset. The median gestational age was 24 (range, 22-28) weeks. A complete heart examination was accomplished in 23 of 30 cases (76.7%; 95% confidence interval, 58-90%). The four-chamber view and the cardiac situs were seen in all cases. The right ventricular outflow tract was seen in 29 (96.7%) cases and the left ventricular outflow tract in 25 (83.3%) cases. The long-axis view of the aortic arch, superior vena cava, inferior vena cava and pulmonary veins were visualized in more than 80% of cases. The mean time of volume acquisition was 9.5 (standard deviation, 2.3) min and the mean examination time by the fetal cardiologist was 17 (standard deviation, 4.8) min. These preliminary results demonstrate that a three-dimensional virtual examination of the fetal heart is possible. There are limitations such as the lack of flow and functional information but complete ascertainment of the main cardiac connections was possible in the majority of cases. The use of an Internet link has major implications, particularly for situations in which the scanning center is geographically remote from the tertiary referral center.

F82Detailed three‐dimensional fetal echocardiography facilitated by an internet link

ObjectivesTo assess whether a complete virtual cardiologic examination can be achieved in stored three‐dimensional volumes of the fetal heart, transmitted to a tertiary fetal cardiology centre via the Internet.MethodsTwenty‐one sequential normal singleton pregnancies. 1–4 cardiac volumes were acquired using a Kretz Voluson 530D scanner. The volumes were sent via the internet to a fetal cardiologist. A detailed fetal cardiac examination, was attempted using the 3D volumetric dataset.ResultsThe mean gestational age was 24 weeks and 3 days. A complete heart examination was accomplished in 81% (95%C.I. 58% to 94%) of cases. The four‐chamber view, and the right ventricle outflow tract were seen in all cases. The ‘three vessel’ view was seen in 91% of the cases, while the left ventricle outflow, long axis view of the aortic arch, SVC/IVC and pulmonary veins in 81% of the cases. The mean time of volume acquisition was 10 min (SD: 2 min) and it was mainly influenced by fetal movements and the transfer time to the main computer. The mean examination time by the fetal cardiologist was 17.8 min (SD 6 min).ConclusionThese preliminary results demonstrate that 3D virtual examination of the heart is possible. Although there are limitations such as the lack of flow and functional information, complete ascertainment of the main cardiac connections was possible in the majority of cases. The use of an internet link has major implications, particularly in situations where the scanning centre is geographically remote from the cardiological centre.

Fetal Tachycardias

Objective—To review the management and outcome of fetal tachycardia, and to determine the problems encountered with various treatment protocols. Study design—Retrospective analysis. Subjects—127 consecutive fetuses with a tachycardia presenting between 1980 and 1996 to a single tertiary centre for fetal cardiology. The median gestational age at presentation was 32 weeks (range 18 to 42). Results—105 fetuses had a supraventricular tachycardia and 22 had atrial flutter. Overall, 52 fetuses were hydropic and 75 non-hydropic. Prenatal control of the tachycardia was achieved in 83% of treated non-hydropic fetuses compared with 66% of the treated hydropic fetuses. Digoxin monotherapy converted most (62%) of the treated non-hydropic fetuses, and 96% survived through the neonatal period. First line drug treatment for hydropic fetuses was more diverse, including digoxin (n = 5), digoxin plus verapamil (n = 14), and flecainide (n = 27). The response rates to these drugs were 20%, 57%, and 59%, respectively, confirming that digoxin monotherapy is a poor choice for the hydropic fetus. Response to flecainide was faster than to the other drugs. Direct fetal treatment was used in four fetuses, of whom two survived. Overall, 73% (n = 38) of the hydropic fetuses survived. Postnatally, 4% of the non-hydropic group had ECG evidence of pre-excitation, compared with 16% of the hydropic group; 57% of non-hydropic fetuses were treated with long term antiarrhythmics compared with 79% of hydropic fetuses. Conclusions—Non-hydropic fetuses with tachycardias have a very good prognosis with transplacental treatment. Most arrhythmias associated with fetal hydrops can be controlled with transplacental treatment, but the mortality in this group is 27%. At present, there is no ideal treatment protocol for these fetuses and a large prospective multicentre trial is required to optimise treatment of both hydropic and non-hydropic fetuses. Keywords: fetal tachycardia; atrial flutter; supraventricular tachycardia

Fetal tachycardias: management and outcome of 127 consecutive cases

ObjectiveTo review the management and outcome of fetal tachycardia, and to determine the problems encountered with various treatment protocols.Study designRetrospective analysis.Subjects127 consecutive fetuses with a tachycardia presenting between 1980 and...

Outcome of Intermittent Tachyarrhythmias in the Fetus

Persistent fetal tachycardias are known to have an adverse effect on fetal outcome. The outcomes of intermittent fetal tachyarrhythmias over a 12-year period at a tertiary fetal cardiology center were studied. Main outcome criteria included control of arrhythmia and death during the prenatal or postnatal period. A total of 28 fetuses had an intermittent tachyarrhythmia: 4 had intermittent atrial flutter and 24 had supraventricular tachycardia. At the time of presentation 14 fetuses were hydropic, and in 5 of the 14 an arrhythmia had not been noted prior to referral. Of the 28 fetuses, 23 were treated by drug administration to the mother. Control of arrhythmia was achieved in 10 of 11 (91%) nonhydropic fetuses and 8 of 12 (67%) hydropic fetuses, with resolution of hydrops in four cases. In the overall group there was one intrauterine death, two neonatal deaths, and one infant death, all of which occurred in the hydropic group. The arrhythmia recurred postnatally in 11 of 23 (48%) fetuses. We conclude that intermittent tachyarrhythmias may have a deleterious effect on the fetus with a significant risk of death pre- or postnatally. The fetus with nonimmune hydrops should be evaluated for a cardiac cause. Maternal antiarrhythmic therapy is indicated for intermittent fetal tachyarrhythmias. There is a high risk of recurrence of the arrhythmia during infancy, particularly if hydrops was documented during the prenatal period or if Wolff-Parkinson-White syndrome is diagnosed. Fetal echocardiography is a useful tool for diagnosis and for monitoring the progress of the fetus.

Natural history and outcome of aortic stenosis diagnosed prenatally.

OBJECTIVE: To document the growth of the left heart structures and outcome of fetuses with aortic stenosis. DESIGN: Retrospective echocardiographic and clinical study. SETTING: Tertiary centre for fetal cardiology. PATIENTS:...

Outcome of intermittent tachyarrhythmias in the fetus.

Persistent fetal tachycardias are known to have an adverse effect on fetal outcome. The outcomes of intermittent fetal tachyarrhythmias over a 12-year period at a tertiary fetal cardiology center were studied. Main outcome criteria included control of arrhythmia and death during the prenatal or postnatal period. A total of 28 fetuses had an intermittent tachyarrhythmia: 4 had intermittent atrial flutter and 24 had supraventricular tachycardia. At the time of presentation 14 fetuses were hydropic, and in 5 of the 14 an arrhythmia had not been noted prior to referral. Of the 28 fetuses, 23 were treated by drug administration to the mother. Control of arrhythmia was achieved in 10 of 11 (91%) nonhydropic fetuses and 8 of 12 (67%) hydropic fetuses, with resolution of hydrops in four cases. In the overall group there was one intrauterine death, two neonatal deaths, and one infant death, all of which occurred in the hydropic group. The arrhythmia recurred postnatally in 11 of 23 (48%) fetuses. We conclude that intermittent tachyarrhythmias may have a deleterious effect on the fetus with a significant risk of death pre- or postnatally. The fetus with nonimmune hydrops should be evaluated for a cardiac cause. Maternal antiarrhythmic therapy is indicated for intermittent fetal tachyarrhythmias. There is a high risk of recurrence of the arrhythmia during infancy, particularly if hydrops was documented during the prenatal period or if Wolff-Parkinson-White syndrome is diagnosed. Fetal echocardiography is a useful tool for diagnosis and for monitoring the progress of the fetus.