Digoxin-like immunoreactive substance in fetuses with and without cardiac pathology

Role of endogenous digitalis-like factors in the clinical manifestations of severe preeclampsia: a sytematic review

Endogenous digitalis-like factor(s), originally proposed as a vasoconstrictor natriuretic hormone, was discovered in fetal and neonatal blood accidentally because it cross-reacts with antidigoxin antibodies (ADAs). Early studies using immunoassays with ADA identified the digoxin-like immuno-reactive factor(s) (EDLF) in maternal blood as well, and suggested it originated in the feto-placental unit. Mammalian digoxin-like factors have recently been identified as at least two classes of steroid compounds, plant derived ouabain (O), and several toad derived bufodienolides, most prominent being marinobufagenin (MBG). A synthetic pathway for MBG has been identified in mammalian placental tissue. Elevated maternal and fetal EDLF, O and MBG have been demonstrated in preeclampsia (PE), and inhibition of red cell membrane sodium, potassium ATPase (Na, K ATPase (NKA)) by EDLF is reversed by ADA fragments (ADA-FAB). Accordingly, maternal administration of a commercial ADA-antibody fragment (FAB) was tested in several anecdotal cases of PE, and two, small randomized, prospective, double-blind clinical trials. In the first randomized trial, ADA-FAB was administered post-partum, in the second antepartum. In the post-partum trial, ADA-FAB reduced use of antihypertensive drugs. In the second trial, there was no effect of ADA-FAB on blood pressure, but the fall in maternal creatinine clearance (CrCl) was prevented. In a secondary analysis using the pre-treatment maternal level of circulating Na, K ATPase (NKA) inhibitory activity (NKAI), ADA-FAB reduced the incidence of pulmonary edema and, unexpectedly, that of severe neonatal intraventricular hemorrhage (IVH). The fall in CrCl in patients given placebo was proportional to the circulating level of NKAI. The implications of these findings on the pathophysiology of the clinical manifestations PE are discussed, and a new model of the respective roles of placenta derived anti-angiogenic (AAG) factors (AAGFs) and EDLF is proposed.

Transplacental treatment of fetal tachycardia: implications of drug transporting proteins in placenta

Sustained fetal tachyarrhythmia (> 180 bpm) is a potentially life-threatening condition for the unborn. Digoxin is commonly used as an initial monotherapy. Flecainide, sotalol, and verapamil are also used as a monotherapy or a combination therapy with digoxin. The treatment success rate with digoxin is about 50%. Presence of hydrops is associated with poor placental transfer of digoxin. Although transplacental pharmacotherapy has been available, it is a challenging task to maximize fetal drug exposure, while minimizing drug exposure of the mother. In addition, clear evidence behind drug of choice and treatment algorithm is lacking. Whereas prospective clinical studies with rigorous design remain to be seen, our knowledge on placental drug transport at a molecular level has been steadily increasing. For example, an ATP-dependent membrane protein, known as P-glycoprotein, is expressed in placenta, decreasing fetal exposure to maternal digoxin. Pharmacological manipulation of drug transporters may open a door to ultimate optimization of the transplacental pharmacotherapy.

Fetal cerebral AV-malformation and cardiomegaly, diagnostic and therapeutic problems

Intracerebral aneurysms are rare. However they are potentially life-threatening. Today by means of ultrasound investigations these malformations can occasionally be identified prenatally. In these cases questions of intrauterine therapy, mode and time of delivery and postnatal treatment have to be discussed with the parents. We describe two cases with prenatal diagnosis of intracerebral arteriovenous malformations, diagnostic workup, therapeutic options and fetal outcome.

Parathyroid hormone levels in preterm and term labor

This prospective study was undertaken to test the hypothesis that parathyroid hormone (PTH) might be involved in preterm or term labor. Four groups of patients were formed, 15 patients in each group. The preterm labor group were patients who were admitted to our perinatal care unit with preterm labor and unruptured membranes (< 35 weeks' gestation). The preterm or term nonlabor control groups were patients matched for gestational age, maternal age, and parity, who were not in labor. The term labor group were patients matched for maternal age and parity who were in active labor. Mean (+/-SD) level of biologically intact PTH was 18.9 +/- 10.6 pgr/mL, 7.6 +/- 4.7 pgr/mL, 20.8 +/- 10.1 pgr/mL, 13.7 +/- 5.3 pgr/mL in preterm labor group, preterm nonlabor group, term labor group, and term nonlabor group, respectively (p < 0.05). No statistically significant differences were observed in the levels of calcium, phosphorus, magnesium, or albumin. We therefore suggest that PTH may have a role in preterm or term labor. The nature of its role should be investigated in further studies.

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.

Transplacental passage of digoxin in severe Rhesus immunization

Maternal and umbilical vein digoxin concentrations were determined in 16 mothers and fetuses with severe Rhesus-D disease, eight with, and eight without prior digitalization of the mother, when umbilical cord puncture was performed for diagnosis and intrauterine blood transfusion. In the eight patients without digoxin treatment, the digoxin concentrations in both the mother and the umbilical vein were below the limit of detection (less than 0.3 nmol/l). In the other eight patients digitalization of the mother was started 24-48 hours before the first umbilical cord puncture. The maternal and umbilical vein digoxin concentrations were determined on 26 occasions. Except for two instances, digoxin concentrations in the umbilical vein were always below 1 nmol/l. The mean ratio of maternal to fetal digoxin concentrations before initial transfusion was 2.51 ( +/- ISD = 1.47) and before later transfusions 1.67 ( +/- ISD = 0.61). The differences in mean ratios between initial and later transfusions are not significant (p = 0.16). The mean ratio for the total group was 1.93 ( +/- ISD = 1.01). There was no correlation between the maternal to umbilical vein digoxin ratio and either gestational age or umbilical venous hematocrit. The results of our study indicate that the therapeutic effect of transplacental digitalization in severe Rhesus disease is questionable and that a multicentre randomized trial would be necessary to evaluate whether this treatment is of benefit.

Antenatal diagnosis and palliative treatment of non-immune hydrops fetalis secondary to fetal parvovirus B19 infection

Hydrops fetalis was diagnosed at 22 weeks. An ultrasound examination demonstrated cardiomegaly and a fetal blood specimen obtained by cordocentesis revealed thrombocytopenia, anaemia, and neutropenia. Fetal paracentesis yielded straw-coloured fluid with electrolytes indicative of a transudate. Non-enveloped icosahedral viral particles approximately 23 mm in diameter were visualized in the ascitic fluid by electron microscopy. Immune electron microscopy confirmed human parvovirus B19. Direct fetal digitalization led to a reduction in umbilical artery resistance, a decline in the abdominal circumference from 20.3 to 17.8 cm, and resolution of the ascites within 72 h. Despite this dramatic response to therapy, fetal death occurred on day 5 of treatment. The initial maternal serum was positive for anti-B19 IgM and IgG antibodies. Electron microscopy of fetal cardiac tissue obtained post-mortem revealed intranuclear viral particles typical of B19, confirming the antenatal diagnosis of myocarditis. This case demonstrates that direct viral identification is applicable to prenatal diagnosis. To our knowledge, this is the first reported case of the antenatal diagnosis and palliative treatment of fetal viral infection.

Atrial natriuretic factor, digoxin-like immunoreactive substance, norepinephrine, epinephrine, and plasma renin activity in human fetuses and their alteration by fetal disease

We measured five hormones presumably involved in fetal homeostasis in specimens obtained by cordocentesis for clinical indications from 106 fetuses. Norms for atrial natriuretic factor, digoxin-like immunoreactive substance, plasma renin activity, norepinephrine, and epinephrine were derived from fetuses ultimately shown to be free of detectable abnormality. Atrial natriuretic factor, digoxin-like immunoreactive substance, and plasma renin activity were unrelated to umbilical vessel source or gestational age. Digoxin-like immunoreactive substance was directly related to PCO2 (r = 0.63, p = 0.02). Digoxin-like immunoreactive substance level was elevated in all fetal disease states studied except isoimmunization. The level of atrial natriuretic factor was elevated in fetuses with immune hydrops (NS). Norepinephrine and epinephrine levels were higher in the umbilical artery than in the vein (p = 0.05 and 0.006, respectively). There was a significant correlation between norepinephrine and gestational age in normal fetuses (r = 0.7637, p less than 0.025) and between both catecholamines and many of the respiratory blood gas measurements, with pH and PCO2 being the major determinants. Most disease states were associated with an elevated norepinephrine concentration. There was a negative correlation between plasma renin activity and base deficit (p less than 0.0001). Plasma renin activity was elevated in fetuses with idiopathic growth retardation and nonimmune hydrops (p less than 0.05 for each). In summary, fetal homeostasis as reflected by these five hormones was altered by a variety of disorders. With these baseline values the effects of direct or indirect fetal therapy can begin to be studied.

Direct treatment of fetal supraventricular tachycardia after failed transplacental therapy

Digitalization by direct intramuscular injection of the fetus successfully controlled supraventricular tachycardia at 24 weeks' gestation after more traditional intensive trials of transplacental therapy with digoxin, verapamil, and procainamide, either separately or in combination, had failed. The fetal pharmacokinetics were calculated from fetal blood samples obtained by cordocentesis. No clear evidence of placental transfer of digoxin administered to the mother could be found despite a digoxin concentration in the mother that ranged from 1.8 to 2.6 ng/ml for 4 days. After direct fetal digitalization we calculated that the coefficient of elimination for digoxin from the fetus was 0.0463 h-1, and digoxin elimination half-life was 15.9 hours. The latter time span is substantially less than the 50-hour half-life previously reported in newborn infants with low birth weight. The fetal/maternal concentration ratio of procainamide was 0.914. However, maternal clearance of procainamide (9.7 ml/kg-1/min-1) was twice as long as the clearance reported for nonpregnant patients undergoing fast acetylation. We conclude first, that at least in the dose of this ill fetus, little digoxin administered to the mother crossed the placentae; and second, that while direct fetal therapy with digoxin is effective, the necessary frequent number of injections render this therapy impractical. Direct fetal digitalization should probably be reserved for the preterm fetus who has evidence of heart failure and has not responded to maternally administered therapy other than digoxin.