Perinatal outcome of paroxysmal tachycardia of the newborn with onset in utero. Report of 2 cases; review of the literature and a discussion of a clinical approach to fetal tachycardia

Resolution of tachyarrhythmia-related fetal hydrops after corticosteroid administration for fetal lung maturation

A case of hydrops fetalis (HF) that resolved after corticosteroid therapy despite persisting fetal tachycardia of 190 bpm is reported. The fetus with confirmed normal karyotype had HF in the presence of atrial flutter and sustained ventricular rate of 200-210 bpm at gestational week (GW) 31(-6/7). Aetiologies of HF other than fetal tachyarrhythmia were unlikely in this infant. The patient's family declined pharmacological treatment with maternal digoxin and desired to continue pregnancy with only intensive monitoring of fetal condition. Maternal transplacental β-methasone was given to facilitate fetal lung maturation. The fetal tachyarrhythmia ameliorated to 190 bpm at GW 32(-5/7) and HF gradually disappeared by birth. The otherwise healthy female neonate weighing 3050 g born at GW 37(-0/7) was successfully treated with cardioversion performed 60 min after birth. This case suggested that corticosteroid therapy contributed to the resolution of HF associated with tachyarrhythmia.

Fetal tachycardia: mechanisms and predictors of hydrops fetalis

OBJECTIVES

This study had three objectives: 1) to determine the electrophysiologic mechanisms of fetal supraventricular tachycardia at presentation and postnatally; 2) to identify the clinical and electrophysiologic predictors of hydrops fetalis; and 3) to describe the medium-term follow-up (1 to 7 years) of patients with fetal supraventricular tachycardia.

BACKGROUND

Fetal supraventricular tachycardia causes significant fetal and neonatal morbidity and mortality. Prenatal analysis and postnatal confirmation of fetal supraventricular tachycardia mechanisms have been limited.

METHODS

Supraventricular tachycardia mechanisms were evaluated by prenatal Doppler/M-mode echocardiography, immediate neonatal surface electrocardiography and postnatal transesophageal electrophysiologic procedures in 30 consecutive patients presenting with fetal supraventricular tachycardia (17 managed prenatally, 13 first managed postnatally).

RESULTS

The fetal supraventricular tachycardia mechanism was 1:1 atrioventricular conduction in 22 patients and supraventricular tachycardia with atrioventricular block (atrial flutter) in 8. At the postnatal transesophageal electrophysiologic procedure, tachycardia was induced in 27 of 30 patients; atrioventricular reentrant tachycardia in 25 (93%) of 27 and intraatrial reentrant tachycardia in only 2 (7%) of 27. Hydrops was present in 12 of 30 fetuses. Sustained supraventricular tachycardia (> 12 h) and lower gestation at presentation correlated with hydrops (p < 0.02, p < 0.05), but mechanism of tachycardia and heart rate did not. Gestational age at delivery was significantly greater in those who received intrauterine management (39 +/- 1.3 vs. 37 +/- 2.9 weeks, p = 0.04) despite earlier presentation (32.6 vs. 37.1 weeks). Cesarean section deliveries were reduced in the same group (3 of 17 vs. 11 of 13, p = 0.0006).

CONCLUSIONS

Atrioventricular reentrant tachycardia was the predominant mechanism of supraventricular tachycardia in the fetus. There was a high association of supraventricular tachycardia with atrioventricular block in utero and accessory atrioventricular connections. Outcome at 1 to 7 years was excellent regardless of severity of illness at clinical presentation.

Developmental characteristics of fetal arrhythmias during the period from intrauterine to early extrauterine life assessed using dual echocardiography

To evaluate the outcome of fetal arrhythmias, serial echocardiographic examinations were made on 29 fetuses between 18 and 41 weeks gestation, including 23 with premature contractions (PCs) and 6 with complete atrioventricular block (AVB). Of the cases of PCs 43.5% (10/23) disappeared spontaneously during the antenatal period. 39.1% (9/23) converted to a normal sinus rhythm in early neonatal life, while 17.4% (4/23) had complications of either atrial or ventricular tachycardia. All with AVB (6/6) remained, regardless of advance in gestational age and continued through to the postnatal period. PCs and AVB indicate functional error and an impairment during development of the conduction system, respectively.

Clinical outcome and circulatory effects of fetal cardiac arrhythmia

By means of abdominal fetal ECG and non-invasive ultrasound blood flow studies 113 cases of fetal cardiac arrhythmia were classified according to the origin of arrhythmia. Pregnancy outcome was characterized by an increased frequency of fetal distress and heart malformation, and increased fetal and neonatal mortality. The following types of arrhythmia were identified: supraventricular extrasystoles (n = 84), paroxysmal tachycardia (n = 6), sinus bradycardia (n = 3), atrial flutter (n = 1), ventricular extrasystoles (n = 14), and atrioventricular block (n = 5). In 37 cases the combined Doppler and real-time ultrasound technique was used to measure fetal aortic blood flow as a means of studying the circulatory effects of the arrhythmia. Increased peak velocity, rising slope and acceleration were found in the first post-pausal beat after a supraventricular extrasystole or a missed beat; this supports the validity of Frank-Starling law for the fetal heart and suggests that a strong relationship exists between these variables and myocardial contractility. In two cases of intra-uterine heart failure, the effect of digoxin treatment in utero on the fetal aortic flow variables was studied, results indicating a positive inotropic effect of the drug on the fetal myocardium. The estimation of fetal aortic volume blood flow in cases of fetal cardiac arrhythmia is useful for early detection of fetal cardiac failure, and for monitoring the effects of intra-uterine treatment.

Severe hydrops fetalis due to congenital supraventricular tachycardia

Intrauterine supraventricular tachycardia is one of the main causes of non-immunological intrauterine hydrops fetalis. Without early diagnosis and treatment it may terminate in fetal death or delivery of a baby with severe hydrops and extreme heart failure. With the improvement in non-invasive imaging techniques in prenatal medicine, this condition can be diagnosed early and treated successfully. A case is described of such a newborn diagnosed in utero and treated before and after delivery, and the different therapeutic approaches to congenital supraventricular tachycardia are discussed.

Haemodynamic assessment of fetal heart arrhythmias

The effects of fetal heart arrhythmias were examined serially in two pregnancies by three non-invasive methods: fetal ECG, fetal phonocardiography and ultrasonic measurement of fetal blood flow. In a case of supraventricular arrhythmia, there was evidence suggesting that the stroke volume varied with ventricular filling according to the Frank-Starling law. In a case of total atrioventricular block the mean blood flow in the fetal descending aorta and in the umbilical vein was within the normal range. Blood flow velocity in the inferior vena cava of the fetus reflected atrial contractions. In the phonocardiogram, a phenomenon similar to 'bruit de canon' was found. Both pregnancies had good outcomes and subsequent development of the infants was normal except for the persisting dysrhythmias. The two cases exemplify how fetal heart function can be assessed in utero.

Treatment of intrauterine supraventricular tachycardia with digoxin and verapamil

Intrauterine fetal supraventricular tachycardia (ISVT) is a rare condition which is connected with organic heart disease in only 4-10 per cent. However, neonatally these children develop heart failure in a high frequency (62 per cent). Intrauterine digitalization has been suggested as treatment, especially if the fetus is preterm. Fetal therapeutic concentrations might demand doses inconvenient to the mother. We hereby report one case of intrauterine SVT in the 26th gestational week treated with a standard dose of digoxin resulting in subtherapeutic umbilical digoxin levels. When no consistent influence on fetal heart rate could be seen, verapamil (80 mg x 3) was added to the treatment. A reversion of the tachycardia and the fetal ECG changes was achieved within two days. The verapamil treatment could be withdrawn after ten days, while the digoxin treatment was continued. An initial discrete heart enlargement also was reversed by the treatment. The delivery in gestational week 38 was uneventful and the child did well. A neonatal ECG showed a sinus rythm interfoliated with supraventricular extrasystoles. No signs of organic heart disease have appeared. When last seen at nine months of age, the ECG was normal and digoxin had been discontinued without recurrence of tachycardia.

Perinatal paroxysmal supraventricular tachycardia

Three cases of perinatal paroxysmal supraventricular tachycardia are described. In two patients the tachycardia was present prior to delivery; in the third baby, who also had the Wolf-Parkinson-White Syndrome, the time of onset of tachycardia is not known. The risks of this condition to the foetus are largely unknown but severe intra-uterine cardiac failure can occur. Possible lines of management are discussed.

Fetal echocardiography. A tool for evaluation of in utero cardiac arrhythmias and monitoring of in utero therapy: analysis of 71 patients

Fetal echocardiographic studies were performed in 71 patients referred for evaluation of cardiac rhythm disturbances at 24 to 40 weeks' gestation. After 2-dimensional echocardiographic study of cardiac structure was performed, M-mode echocardiograms were analyzed for measurement of cardiac rate, atrioventricular contraction sequence, atrioventricular valve motion, and duration of postectopic pauses. Arrhythmias were diagnosed in 59 patients. In 34 patients with isolated ectopic beats, the arrhythmia resolved during later pregnancy in 26 or within the first 5 days of life in 8. Six patients had mild sinus bradycardia and 8 had frequent sinus pauses; all 14 had resolution of the arrhythmia during pregnancy. Sustained arrhythmias occurred in 11 patients. Deaths occurred when there was associated fetal congestive heart failure (hydrops fetalis), structural heart disease, or both. M-mode echocardiography diagnosed supraventricular tachycardia in 3 fetuses. The echocardiogram was used thereafter for monitoring transplacental digoxin therapy.

Supraventricular tachycardia with edema, ascites, and hydrops in fetal sheep

Continuous supraventricular tachycardia was induced in 13 fetal sheep for 72 to 216 hours. The PaO2 decreased from 18.1 +/- 1.2 (SEM) to 15.4 +/- 0.9 mm Hg and the PaCO2 increased from 41.5 +/- 1.2 (SEM) to 46.0 +/- 1.0 (SEM) mm Hg with pacing. The hematocrit, total protein, albumin, serum [Na+] and [K+], and osmolality remained unchanged throughout the study. All study fetuses showed signs of ascites (mean = 88 +/- 67.5 [SD] ml), and one was grossly hydropic. Six fetuses, all of which had greater than or equal to 50 ml of ascites, died as the results of pacing. Gross pathologic findings in 13 fetuses included: cardiomegaly in seven, cyanotic myocardium in two, hepatomegaly in seven, pulmonary congestion in two, generalized edema in three, and massive edema (hydrops) in one. None of these conditions was found in the 14 control animals. There was no correlation of the severity of effects upon the fetus and the induced heart rate, the duration of tachycardia, or the site of implantation of the pacemaker. The conclusion was that organomegaly, generalized edema, and hydrops fetalis were the direct result of supraventricular tachycardia in utero; the exact mechanism of production and the reasons for the variable manifestations of tachycardia remain unclear.

Fetal cardiac arrhythmia: antepartum diagnosis of a case of congenital atrial flutter

A case of antepartum atrial tachyarrhythmia was detected in the 36th week of pregnancy. Cardiotocograph recordings done twice daily enabled close surveillance of the fetal condition after oxytoxin challenge testing had failed to show evidence of hypoxia. After a diagnosis of fetal cardiac arrhythmia had been made, elective caesarean section in the 40th week of pregnancy resulted in delivery of an infant in atrial flutter and cardiac failure. Both these problems were soon resolved by cardioversion and subsequent treatment with digoxin. Cardiac catheterisation showed no underlying cardiac abnormality. Increasing use of antenatal cardiotocography may show that intrauterine tachyarrhythmias are more common than had generally been believed.

Transplancental cardioversion of intrauterine supraventricular tachycardia with digitalis

Intrauterine congestive heart-failure caused by a supraventricular tachyarrhythmia was diagnosed in a fetus at 29-30 weeks' gestation. Major congenital malformations were excluded by sonography, amniocentesis, and fetal abdominal paracentesis, and those of the heart by intrauterine fetal echocardiography. The mother was given digoxin and the fetal tachycardia converted to sinus rhythm.

Intrauterine digoxin treatment of fetal paroxysmal tachycardia. Case report

A patient with fetal paroxysmal supraventricular tachycardia (PST) with a heart rate above 300 beats/minute in the 29th week of pregnancy is described. The fetus showed signs of severe cardiac failure and was, therefore, digitalized by giving the mother 0.5 mg digoxin intravenously on the first day and the 0.25 mg oral digoxin daily throughout the pregnancy. After one day a normal rhythm was observed. The patient was delivered of a healthy girl after 38 weeks of pregnancy. Digoxin concentrations in samples of umbilical cord vein and artery, intrapartum scalp capillary, and amniotic fluid were almost equal, but somewhat lower than in simultaneously obtained maternal serum. Intrauterine digoxin treatment of fetuses with PST is discussed.

Intrauterine supraventricular tachycardia

Six examples of intrauterine supraventricular tachycardia together with 31 previously reported cases are described and analyzed. Among the 37 infants, structural heart disease was present in only four (11%), three of whom died. Males comprised 68% of the group without identifiable heart disease or pre-excitation. Congestive heart failure was evident in 62% of the infants at birth or shortly thereafter; ascites was the predominant finding in three (8%). Neither the duration of SVT nor heart rate was predictive of the clinical status at birth. Infants without underlying heart disease or conduction abnormalities had a benign course after the neonatal period. Thirty-eight percent of the babies converted to sinus rhythm during or shortly after delivery without medication, and most of the others converted after digitalization. The failure of maternal digitalization to convert SVT to sinus rhythm in two of our infants was perhaps related to subtherapeutic maternal and fetal digoxin levels. Newborn infants presenting with unexplained ascites or congestive heart failure should have an ECG to determine whether pre-excitation is present, and their cardiac rhythm should be monitored for several days.

Congenital atrial flutter

Two cases of congenital atrial flutter, one of which was documented electrocardiographically before birth, are reported. In both patients sinus rhythm was restored with digoxin treatment; in one patient the transition was preceded by various arrhythmias. No cardiac malformation was found in either case, and no materal disease occurred during pregnancy. Both mothers had received medication during pregnancy, but its role as a causative factor is questionable.