Reference values for time intervals between atrial and ventricular contractions of the fetal heart measured by two Doppler techniques

Late-Onset Dilated Cardiomyopathy in Auto Immune-Mediated Complete Congenital Heart Block: A Case Report

Complete congenital heart block (CHB), a rare and fatal bradyarrhythmia observed in children, carries significant mortality and morbidity. When congenital heart block occurs in isolation with a structurally normal heart, it prompts suspicion of an autoimmune etiology, wherein maternal antibodies are transmitted transplacentally, impacting the fetal conducting system. The manifestation of congenital complete atrioventricular block (CCAVB) can lead to complications such as dilated cardiomyopathies, arrhythmias, and fibroelastosis in certain cases. Notably, dilated cardiomyopathy is a significant prognostic factor in children diagnosed with congenital heart block. Pathological investigations have revealed the presence of antibodies, complements, and indicators of inflammation or fibrosis across the myocardium, emphasizing the shared molecular mechanisms between CCAVB and the development of dilated cardiomyopathy (DCM). This article presents the case of a one-year-old female child who presented with signs of dilated cardiomyopathy, later identified through retrospective evaluation as having autoimmune congenital heart block. The mother of the child was diagnosed with Sjogren's syndrome, characterized by positive anti-RO titers. Remarkably, the child remained asymptomatic for a year without the need for pacing intervention. The child's condition was successfully stabilized with appropriate treatment, and plans for pacemaker insertion will be considered once specific criteria are met. The onset of cardiomyopathy in a known case of CCAVB should serve as a crucial alert for prognostic considerations and the potential necessity for early-pacing intervention.

Use of Polynomial Reference Ranges for Atrioventricular Intervals Assessed by Fetal Echocardiography in Anti-Ro/SSA Antibody-Positive Pregnancies to Exclude Fetal Heart Blocks: A Pilot Study

INTRODUCTION

Maternal anti-Ro/SSA antibodies can cause fetal atrioventricular blocks (AVB). This pilot study aims to apply previously published echocardiographic reference ranges of the fetal atrioventricular (AV) intervals in the setting of anti-Ro/SSA antibody-positive pregnancies in order to exclude a 1° AVB.

MATERIALS AND METHODS

Between January 2018 and September 2022, we included all women with known anti-Ro/SSA antibodies followed up at the prenatal ultrasound department of the University Hospital of Bern. AV intervals were serially measured by two previously reported methods and plotted against previously created reference ranges.

RESULTS

We included 23 pregnancies from 17 anti-Ro/SSA antibody-positive women with connective tissue diseases. 443 AV interval measurements were recorded between 16+3 and 38+4 weeks of gestation. 14 (3.2%) AV-intervals measured >150 ms, none measured >170 ms and 8 (1.8%) were found to be >95th percentile. In none of the pregnancies, serial AV-prolongations were noted. The postnatal electrocardiograms demonstrated normal sinus rhythm without AVB in all children.

CONCLUSION

AV intervals of pregnancies followed up for anti-Ro/SSA antibodies without neonatal AVB lie within our published polynomial reference ranges. While diagnosing a 1° AVB remains controversial, more data are needed to prove that our reference ranges are helpful exclude a 1° AVB.

Reference ranges and Z-scores of atrioventricular and ventriculoatrial time intervals in normal fetuses

OBJECTIVE

To establish a reference range and compare differences among three methods, and then to construct Z-score reference ranges in normal fetuses from the three methods to provide an extra tool for fetal conduction time assessment.

METHODS

A total of 227 echocardiographic examinations were finally included. Fetal atrioventricular (AV) time and ventriculoatrial (VA) time intervals were measured by three methods: superior vena cava/ascending aorta (SVC/AAO), pulmonary artery/pulmonary vein (PA/PV) and tissue Doppler imaging (TDI). Regression analysis of the mean and standard deviation was performed to establish Z-scores.

RESULTS

With the three methods, positive correlations of intervals with gestational age (GA) and fetal heart rate (FHA) were observed, while intervals were negatively correlated with fetal heart rate (FHR). Correlations between VA/AV and GA, FHA and FHR were weak. The general trend of all intervals was towards an increase. In AV intervals, PA/PV revealed the longest mean AV time interval and SVC/AAO showed the shortest interval. In addition, PA/PV revealed the shortest VA interval.

CONCLUSION

This study presents not only the reference range of AV and VA intervals with the three methods but also the Z-score reference ranges for these indices against GA and FHA in normal fetuses. Each method has a different reference range, and appropriate application can facilitate diagnosis and treatment.

Home fetal heart rate monitoring in anti Ro/SSA positive pregnancies: Literature review and case report

Anti-Ro/SSA antibodies are associated with a risk of 1-2 % to develop complete atrioventricular block (AVB) in fetuses of positive mothers. Complete AVB is irreversible, but studies suggest that anti-inflammatory treatment during the transition period from a normal fetal heart rate (FHR) to an AVB might stop this progression and restore sinus rhythm. The most efficient method for diagnostic evaluation of this arrhythmia is the pulsed-Doppler fetal echocardiography. However, weekly or bi-weekly recommended fetal echocardiographic surveillance can rarely identify an AVB in time for treatment success, also because the transition from a normal rhythm to a third degree AVB is very fast. Daily FHR monitoring in a medical facility could increase the chances of identifying the AVB onset but is difficult to realize. For this reason, an alternative method of FHR monitoring, performed directly by mothers in their home context, has been recently proposed. We present a case report utilizing this approach and review the current evidence about this condition.

Assessment of Mechanical Fetal PR Interval in Intrahepatic Cholestasis of Pregnancy and Its Relationship with the Severity of the Disease

OBJECTIVE

This study aimed to investigate the fetal atrioventricular conduction system in intrahepatic cholestasis of pregnancy (ICP) by measuring the fetal mechanical PR interval and to explore the significance of predicting the severity of the disease.

STUDY DESIGN

Forty pregnant women diagnosed with ICP, classified as severe and mild, and 40 healthy pregnant women participated in the study. Fetal mechanical PR interval was calculated, and fetal mechanical PR interval and neonatal outcome were compared between the groups. The relationship between the mechanical PR interval and the severity of ICP was analyzed.

RESULTS

The fetal mechanical PR interval was significantly longer in the ICP group than in the control group (p < 0.005). Likewise, laboratory parameters such as transaminases (alanine aminotransferase [ALT], aspartate aminotransferase [AST]) and total bilirubin levels were significantly higher in the ICP group (p < 0.005).There were no statistically significant differences in the fetal complications. There was a positive correlation between the severity of disease and fetal PR interval.

CONCLUSION

A prolonged fetal mechanical PR interval in fetuses of mothers with ICP was demonstrated in this study. It was also shown that there was a positive correlation between fetal PR interval and severity of the disease. The study concluded that fetal mechanical PR interval measurement can be used to predict the severity of disease in ICP.

A Broader Perspective on Anti-Ro Antibodies and Their Fetal Consequences-A Case Report and Literature Review

The presence of maternal Anti-Ro/Anti-La antibodies causes a passively acquired autoimmunity that may be associated with serious fetal complications. The classic example is the autoimmune-mediated congenital heart block (CHB) which is due in most cases to the transplacental passage of Anti-Ro/Anti-La antibodies. The exact mechanisms through which these pathologic events arise are linked to disturbances in calcium channels function, impairment of calcium homeostasis and ultimately apoptosis, inflammation and fibrosis. CHB still represents a challenging diagnosis and a source of debate regarding the best management. As the third-degree block is usually irreversible, the best strategy is risk awareness and prevention. Although CHB is a rare occurrence, it affects one in 20,000 live births, with a high overall mortality rate (up to 20%, with 70% of in utero deaths). There is also concern over the lifelong consequences, as most babies need a pacemaker. This review aims to offer, apart from the data needed for a better understanding of the issue at hand, a broader perspective of the specialists directly involved in managing this pathology: the rheumatologist, the maternal-fetal specialist and the cardiologist. To better illustrate the theoretical facts presented, we also include a representative clinical case.

Autoimmune Congenital Heart Block: A Review of Biomarkers and Management of Pregnancy

Autoimmune Congenital Heart Block (CHB) is an immune-mediated disease due to transplacental passage of circulating anti-Ro/SSA and anti-La/SSB autoantibodies. It occurs in 2% of anti-Ro/SSA-exposed pregnancies, and recurrence rate is nine times higher in subsequent pregnancies. Aim of this review is to identify biomarkers of CHB and treatment strategies. The Ro-system is constituted by two polypeptides targeted by the anti-Ro52 and anti-Ro60 autoantibodies. The central portion of Ro52 (p200), more than the full amino-acid sequence of Ro-52, is recognized to be the fine specificity of anti-Ro associated to the highest risk of cardiac damage. If anti-p200 antibody should be tested, as biomarker of CHB, over standard commercial ELISAs is still debated. Recent studies indicate that type I-Interferon (IFN) can activate fibroblasts in fetal heart. In the mother the anti-Ro/La antibodies activate the type I IFN-signature, and maternal IFN-regulated genes correlate with a similar neonatal IFN-gene expression. Evaluation of maternal IFN-signature could be used as novel biomarker of CHB. The measurement of "mechanical" PR interval with weekly fetal echocardiogram (ECHO) from 16 to at least 24 weeks of gestation is strongly recommended for CHB prenatal diagnosis. However, ECHO screening presents some limitations due to difficult identification of first-degree block and possible occurrence of a complete block from a normal rhythm in few days. Maternal administration of Hydroxychloroquine from the tenth week of gestation, modulating toll-like receptor and autoantibody-dependent type I IFN activation on the fetus, has an important role in preventing CHB in pregnant women with high risk for recurrent CHB.

Assessment of atrioventricular conduction by echocardiography and magnetocardiography in normal and anti-Ro/SSA-antibody-positive pregnancies

OBJECTIVES

The objectives of this study were, first, to evaluate the association between fetal echocardiographic atrioventricular (AV) and magnetocardiographic (fMCG) PR intervals at different gestational ages (GAs) in normal and anti-Ro/SSA-antibody-positive pregnancies; second, to determine if PR interval could be predicted by AV interval; and third, to assess the neonatal outcome of fetuses with prolonged AV and PR intervals, with the goal of developing criteria for fetal first-degree AV block (AVB-I).

METHODS

This was a retrospective study of anti-Ro/SSA-antibody-positive pregnancies (cases) and controls that underwent fMCG and fetal echocardiography at the same recording session. Cardiac cycle length, GA and AV (by mitral inflow/aortic outflow Doppler) and PR (by fMCG) intervals were measured. We tested for significant differences between AV and PR intervals using generalized estimating equations to account for repeat measurements, and assessed whether PR interval could be predicted reliably by AV interval. After delivery, infants with fetal AV or PR interval Z-score ≥ 3 underwent 12-lead electrocardiography.

RESULTS

Thirty-nine controls and 31 cases underwent 46 and 36 simultaneous fMCG and echocardiographic examinations, respectively; 101 controls and nine cases underwent fMCG only. AV and PR intervals increased with GA (P < 0.05 for both). Overall, AV and PR intervals were significantly different from each other (P < 0.001); this difference was not significant when compared between cases and controls (P = 0.222). PR interval could not be predicted accurately from AV interval and GA alone. Three of four cases with AV and PR interval Z-scores > + 3 had postnatal AVB-I despite treatment. The fourth fetus, which had predominately second-degree AVB and rare periods of AVB-I, progressed to third-degree AVB despite treatment with dexamethasone.

CONCLUSIONS

The diagnostic threshold for AVB-I, defined by AV interval Z-score, is GA dependent. Based on the observed data, an AV interval Z-score threshold of 3 (AV interval, 151-167 ms) may be appropriate. Echocardiographic AV interval was not predictive of fMCG-PR interval. 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

OBJECTIVES

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.

METHODS

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.

RESULTS

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).

CONCLUSION

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.

Evolution of the Fetal Atrioventricular Interval from 6 to 40 Weeks of Gestation

Doppler-based methods of estimating the atrioventricular interval are commonly used as a surrogate for the electrical PR in fetuses at risk of conduction abnormalities; however, to date, normal values for the fetal atrioventricular interval and an understanding of the evolution of its components in the late first trimester are lacking. We sought to investigate changes in the fetal atrioventricular interval from the first trimester to 40 weeks gestational age, and to explore functional and electrophysiological events that potentially impact its evolution. We prospectively examined healthy pregnancies by fetal echocardiography from 6 to 40 weeks' gestational age. The atrioventricular interval, heart rate, isovolumic contraction time, and A-wave duration were measured from simultaneous ventricular inflow-outflow Doppler tracings. Regression analysis was used to examine relations with gestational age, and linear relations with heart rate were assessed by Pearson's correlation coefficient. Data were collected in 305 fetuses from 279 pregnancies. Atrioventricular interval demonstrated an inverse relation with heart rate (r = -0.45, p <0.0001), dramatically decreasing before 10 weeks and slowly increasing thereafter. Between 6 and 9 weeks, isovolumic contraction time acutely decreased approaching 0, thereafter minimally increasing to term. In contrast, from 6 weeks, the A-wave duration linearly increased through gestation, and negatively correlated with heart rate (r = -0.62, p <0.0001). In conclusion, we have established normal measures of the atrioventricular interval from 6 to 40 weeks' gestational age. Before 10 weeks, a prolonged atrioventricular interval in healthy fetuses largely reflects the lengthened isovolumic contraction time which is likely influenced by the evolution of ventricular function and afterload.

Fetal cardiac arrhythmias: Current evidence

This article reviews important features for improving the diagnosis of fetal arrhythmias by ultrasound in prenatal cardiac screening and echocardiography. Transient fetal arrhythmias are more common than persistent fetal arrhythmias. However, persistent severe bradycardia and sustained tachycardia may cause fetal hydrops, preterm delivery, and higher perinatal morbidity and mortality. Hence, the diagnosis of these arrhythmias during the routine obstetric ultrasound, before the progression to hydrops, is crucial and represents a challenge that involves a team of specialists and subspecialists on fetal ultrasonography. The images in this review highlight normal cardiac rhythms as well as pathologic cases consistent with premature atrial and ventricular contractions, heart block, supraventricular tachycardia (VT), atrial flutter, and VT. In this review, the details of a variety of arrhythmias in fetuses were provided by M-mode and Doppler ultrasound/echocardiography with high-quality imaging, enhancing diagnostic accuracy. Moreover, an update on the intrauterine management and treatment of many arrhythmias is provided, focusing on improving outcomes to enable planned delivery and perinatal management.

Measurement of fetal atrioventricular time intervals: A comparison of 3 spectral Doppler techniques

OBJECTIVE

To establish nomograms for fetal atrioventricular (AV) time intervals assessed by 3 different pulsed-wave Doppler techniques: left ventricular inflow and outflow tracts (LV in/out), superior vena cava and ascending aorta (SVC/AA), and pulmonary artery and pulmonary vein (PA/PV).

METHODS

A cross-sectional study was performed in 311 normal fetuses divided into 5 groups between 16 and 38 weeks. Pulsed-wave Doppler-derived AV intervals were measured by interrogation of flow in LV in/out, SVC/AA, and PA/PV. Linear regression analyses were performed to examine correlations with gestational age (GA) and fetal heart rate (FHR). Intraclass correlation coefficients for reproducibility of each method were compared.

RESULTS

Pulmonary artery and pulmonary vein revealed the longest mean AV time intervals (P < .001). The AV intervals in all methods were positively correlated with GA (R²  = 0.20-0.36; P < .001) and negatively correlated with FHR (R²  = 0.09-0.19; P < .001). The SCV/AA time intervals demonstrated the weakest influence of FHR. For LV in/out, SVC/AA, and PA/PV, intraobserver and interobserver reliability coefficients showed excellent agreements (all intraclass correlation coefficients ≥ 0.80).

CONCLUSION

All pulsed-wave Doppler-derived AV time intervals increased with advancing GA and decreased with increasing FHR. Fetal AV interval measurements can be obtained in a clinically viable fashion with excellent reproducibility.

Congenital and childhood atrioventricular blocks: pathophysiology and contemporary management

Atrioventricular block is classified as congenital if diagnosed in utero, at birth, or within the first month of life. The pathophysiological process is believed to be due to immune-mediated injury of the conduction system, which occurs as a result of transplacental passage of maternal anti-SSA/Ro-SSB/La antibodies. Childhood atrioventricular block is therefore diagnosed between the first month and the 18th year of life. Genetic variants in multiple genes have been described to date in the pathogenesis of inherited progressive cardiac conduction disorders. Indications and techniques of cardiac pacing have also evolved to allow safe permanent cardiac pacing in almost all patients, including those with structural heart abnormalities.

CONCLUSION

Early diagnosis and appropriate management are critical in many cases in order to prevent sudden death, and this review critically assesses our current understanding of the pathogenetic mechanisms, clinical course, and optimal management of congenital and childhood AV block.

WHAT IS KNOWN

• Prevalence of congenital heart block of 1 per 15,000 to 20,000 live births. AV block is defined as congenital if diagnosed in utero, at birth, or within the first month of life, whereas childhood AV block is diagnosed between the first month and the 18th year of life. As a result of several different etiologies, congenital and childhood atrioventricular block may occur in an entirely structurally normal heart or in association with concomitant congenital heart disease. Cardiac pacing is indicated in symptomatic patients and has several prophylactic indications in asymptomatic patients to prevent sudden death. • Autoimmune, congenital AV block is associated with a high neonatal mortality rate and development of dilated cardiomyopathy in 5 to 30 % cases. What is New: • Several genes including SCN5A have been implicated in autosomal dominant forms of familial progressive cardiac conduction disorders. • Leadless pacemaker technology and gene therapy for biological pacing are promising research fields. In utero percutaneous pacing appears to be at high risk and needs further development before it can be adopted into routine clinical practice. Cardiac resynchronization therapy is of proven value in case of pacing-induced cardiomyopathy.

Cardiac Physiology of Pregnancy

Although the physiology of the heart and vascular system has not changed, there are many things we have learned and are still learning today. Research related to heart adaptations during pregnancy has been performed since the 1930s. Since the mid-1950s, researchers began to look at changes in the maternal cardiovascular system during exercise while pregnant. Research related to exercise during pregnancy and offspring heart development began and has continued since the 1970s. We will review the normal female cardiovascular system adaptations to pregnancy in general. Additionally, topics related to maternal cardiac adaptations to pregnancy during acute exercise, as well as the chronic conditioning response from exercise training will be explored. Since physical activity during pregnancy influences fetal development, the fetal cardiac development will be discussed in regards to acute and chronic maternal exercise. Similarly, the influence of various types of maternal exercise on acute and chronic fetal heart responses will be described. Briefly, the topics related to how and if there is maternal-fetal synchrony will be explained. Lastly, the developmental changes of the fetal cardiovascular system that persist after birth will be explored. Overall, the article will discuss maternal cardiac physiology related to changes with normal pregnancy, and exercise during pregnancy, as well as fetal cardiac physiology related to changes with normal development, and exercise during pregnancy as well as developmental changes in offspring after birth.

Perinatal arrhythmias

Cardiac arrhythmias are very frequent in fetuses and newborns. The prognosis depends on the nature of the arrhythmias but is most often either spontaneously benign or following short-term medication administration. A correct diagnosis is essential for both management and prognosis. It is based on echocardiography during the fetal period and mainly on history, physical exam, and electrocardiogram after birth, but other modalities are available to record transient arrhythmic events. Irregular rhythms are mostly benign and rarely require therapy. In most fetuses and infants, tachyarrhythmias resolve spontaneously or require short-term administration of antiarrhythmics. Approximately one third of these may recur later on, especially during adolescence. Persistent bradyarrhythmias might require pacemaker implantation when associated with failure to thrive or with risk of sudden death.

CONCLUSION

Arrhythmias in fetuses and infants are very common and mostly benign. History, physical exam, and recording of the arrhythmia are essential to make a correct diagnosis and establish an appropriate management for the rare potentially harmful arrhythmias.

Atrioventricular block during fetal life

Congenital complete atrioventricular (AV) block occurs in approximately 1 in 20,000 live births and is known to result in significant mortality and morbidity both during fetal life and postnatally. Complete AV block can occur as a result of an immune or a non-immune mediated process. Immune mediated AV block is a multifactorial disease, but is associated with the trans-placental passage of maternal autoantibodies (anti-Ro/SSA and/or anti-La/SSB). These autoantibodies attach to and subsequently damage the cardiomyocytes and conduction tissue in susceptible fetuses. In this report, we examine the evidence in reference to means of assessment, pathophysiology, and potential prenatal therapy of atrioventricular block.

Fetal diagnosis and imaging in cardiology

BACKGROUND

Fetal echocardiography plays a critical role in the diagnosis and management of structural, functional and rhythm-related fetal cardiovascular disease.

OBJECTIVES/METHODS

This article reviews the history of fetal echocardiography and the prenatal diagnosis of fetal cardiovascular disease as well as the evolution of the field of fetal cardiology. The clinical application of fetal echocardiography, including indications for referral, timing of referral and considerations in the diagnosis and serial assessment of fetal cardiovascular disease, is presented.

CONCLUSIONS

Newer directions in the field of fetal cardiology, including first trimester diagnoses and fetal intervention, will continue to expand its role in the evaluation and treatment of affected pregnancies in the future; however, equally as important are efforts to continue to improve prenatal detection rates.

Prenatal diagnosis of long QT syndrome with the superior vena cava-aorta Doppler approach

We describe a fetus at 36 weeks with long QT syndrome presenting with variable types of atrioventricular blocks, ventricular premature beats, and torsades de pointes. All these diagnoses were made with the superior vena cava-aorta Doppler approach and confirmed with postnatal electrocardiography.

Progression to first-degree heart block in preschool children exposed in utero to maternal anti-SSA/Ro52 autoantibodies

AIMS

To study the children exposed in utero to maternal anti-SSA/Ro52 antibodies in terms of impaired atrioventricular (AV) conduction or disturbed myocardial performance, and to investigate the ability of prenatal Doppler to predict conduction abnormalities during childhood.

METHODS

Fifty-seven children exposed in utero to anti-SSA/Ro52 antibodies were grouped in accordance with (A) prolonged AV time intervals in utero by Doppler or (B) normal findings and examined by ECG, 24-hour ECG and echocardiography.

RESULTS

PR interval on ECG was longer in group A (n = 16) compared with that of group B (n = 41), 140 ± 24 ms vs. 121 ± 13 ms (p < 0.01). Six cases of 1°Atrioventricular block (AVB) developed in group A, giving an estimated prevalence of 10.5%, (95% confidence interval; 4.4-22.2%), progressing from normal sinus rhythm at 1 month of age. Prenatal Doppler predicted development of 1°AVB at follow-up with a sensitivity of 100%, Positive predictive value (PPV) 37.5%, LR+ 5.1, and Negative predictive value (NPV) 100%. Children in group A had a slightly higher myocardial performance index in flow and tissue Doppler imaging recordings.

CONCLUSIONS

Ten per cent of children exposed in utero to anti-SSA/Ro52, with a normal ECG at birth or 1 month of age, progressed to 1°AVB during preschool years. Cases at risk can be identified by prenatal Doppler echocardiography.

Finding the "PR-fect" solution: what is the best tool to measure fetal cardiac PR intervals for the detection and possible treatment of early conduction disease?

In the absence of structural heart disease, the great majority of cases with complete congenital heart block will be associated with the maternal autoantibodies directed to components of the SSA/Ro-SSB/La ribonucleoprotein complex. Usually presenting in fetal life before 26 weeks' gestation, once third-degree (complete) heart block develops, it is irreversible. Therefore, investigators over the past several years have attempted to predict which fetuses will be at risk for advanced conduction abnormalities by identifying a biomarker for less severe or incomplete disease, in this case, PR interval prolongation or first-degree atrioventricular block. In this state-of-the-art review, we critically analyze the various approaches to defining PR interval prolongation in the fetus, and then analyze several clinical trials that have attempted to address the question of whether complete heart block can be predicted and/or prevented. We find that, first and foremost, definitions of first-degree atrioventricular block vary but that the techniques themselves are all similarly valid and reliable. Nevertheless, the task of predicting those fetuses at risk, and who are therefore candidates for treatment, remains challenging. Of concern, despite anecdotal evidence, there is currently no conclusive proof that a prolonged PR interval predicts complete heart block.

Atrioventricular conduction time in fetuses assessed by Doppler echocardiography

We performed measurement of mechanical atrioventricular conduction time intervals in human fetuses assessed by Doppler echocardiography and provided reference values. We found that atrioventricular conduction time interval was prolonged with gestational age and decreased with increasing fetal heart rate. No correlation between gestational age and heart rate was found. Using normal limits established by this study, mechanical atrioventricular interval >135 ms in the 20(th) week and/or >145 ms in the 26(th) week of gestation could be suspected of having the first-degree AV block. We compared reference values with fetuses of mothers with anti-SSA Ro/SSB La autoantibodies, being in risk of isolated congenital heart block development. One of 21 fetuses of mothers with positive autoantibodies was affected by prolonged atrioventricular interval according to the established limits, with sinus rhythm after the birth.

Hepatic venous Doppler in the evaluation of fetal extrasystoles

OBJECTIVES

To evaluate the use of fetal hepatic venous Doppler in the diagnosis of fetal extrasystoles, to estimate the prevalence and persistence of extra atrial and ventricular heart beats throughout pregnancy, labor and delivery, and to estimate the frequency of coexisting congenital heart disease.

METHODS

This was a retrospective study of 256 singleton pregnancies attending our hospital as outpatients due to fetal extrasystoles. Hepatic venous Doppler and detailed fetal echocardiography were performed. Information on fetal heart rate patterns during labor and neonatal conditions was collected. Congenital heart malformations and the frequency and persistence of fetal extrasystoles were noted.

RESULTS

On venous Doppler examination, 228 (89%) of the fetuses showed signs of supraventricular extrasystoles (SVES) and 28 (11%) had ventricular extrasystoles (VES). One fetus with SVES developed atrial flutter during pregnancy and another case developed supraventricular tachycardia postnatally. SVES persisted until labor and delivery in 28 (12.3%) fetuses and VES persisted in six (21.4%). In 31 of 34 (91.2%) fetuses with extrasystoles during labor and delivery, the conduction pattern normalized within 3 days. Five neonates were referred for evaluation by a pediatric cardiologist. Two cases had congenital heart disease. Extrasystoles persisted until labor and delivery more frequently in male fetuses (P < 0.0001).

CONCLUSION

Hepatic venous Doppler can differentiate between SVES and VES. Despite being the more uncommon of the two, VES persists throughout pregnancy more often. Our results strongly support the suggestion that extrasystoles are a benign finding, with very few cases developing tachycardia or having a coexisting congenital heart malformation.

Diagnosis and management of common fetal arrhythmias

Fetal arrhythmias are detected in at least 2% of unselected pregnancies during routine obstetrical scans. Most common are transient, brief episodes of a slow or fast heart rate or of an irregular heart rhythm. Less common are prolonged or persistent abnormalities such as supraventricular tachycardia and complete heart block which may lead to low cardiac output, fetal hydrops and demise. The objectives of this review are to update the reader on the diagnosis and management of the more common arrhythmias.

Diagnostic precision of Doppler flow echocardiography in fetuses at risk for atrioventricular block

OBJECTIVE

To investigate the diagnostic precision of three Doppler methods in their ability to predict postnatal first-degree atrioventricular (AV) block.

METHODS

This was a prospective, observational study carried out from December 1999 to March 2008, including 95 fetuses of anti-SSA/Ro positive mothers undergoing weekly fetal echocardiograms at 18-24 weeks' gestation. Doppler-derived AV time intervals for left ventricular inflow (MV), inflow and outflow (MV-Ao) and superior vena cava a-wave to aortic flow (SVC-Ao) were compared with the PR interval on postnatal electrocardiography. Reference values for MV intervals were established from 102 healthy fetuses, with previously published reference ranges used for the two other methods. Bayesian and receiver-operating characteristics (ROC) curve analyses were performed.

RESULTS

The prevalence of first-degree AV block at birth was 13.8%. Using a cut-off at the upper 95% confidence limit, MV-Ao and SVC-Ao time intervals had a sensitivity of 91.7%, and negative predictive value and negative likelihood ratio of 98.4% and 0.10, respectively. The corresponding positive predictive value/positive likelihood ratio for MV-Ao and SVC-Ao were 42.3%/4.5 and 47.8%/5.7, respectively. The areas under the ROC curve (AUC) for MV-Ao and SVC-Ao were 0.87 and 0.89, respectively (both P < 0.001), with generated cut-offs for abnormal AV time intervals at 134-138 and 132-138 ms. MV time intervals using a cut-off at the upper 95% confidence limit had a sensitivity of just 50% and an AUC of 0.74 (P < 0.01).

CONCLUSION

The MV-Ao and SVC-Ao Doppler methods make it possible to identify nearly all fetuses with first-degree AV block at birth and to exclude conduction disturbances in the case of a normal AV time measurement but at the cost of a positive predictive value of 50%.

Diagnosing foetal atrioventricular heart blocks

Foetal echocardiographic ultrasound techniques still remain the dominating modality for diagnosing foetal atrioventricular block (AVB). Foetal electrocardiography might become a valuable tool to measure time intervals, but magnetocardiography is unlikely to get a place in clinical practice. Assuming that AVB is a gradually progressing and preventable disease, starting during a critical period in mid-gestation with a less abnormal atrioventricular conduction before progressing to a complete irreversible AVB (CAVB), echocardiographic methods to detect first-degree AVB have been developed. The time intervals obtained with these techniques are all based on the identification of mechanical or hemodynamic events as markers of atrial (A) and ventricular (V) depolarizations and will accordingly include both electrical and mechanical components. Prospective observational studies have demonstrated a transient prolongation of AV time intervals in anti-Ro/SSA antibody-exposed foetuses, but it has not succeeded to identify a degree of AV time prolongation predicting irreversible cardiac damage and progression to CAVB. Causes of sustained bradycardia include CAVB, 2:1 AVB, sinus bradycardia and blocked atrial bigeminy (BAB). Using foetal echocardiographic techniques and a systematic approach, a correct diagnosis can be made in almost every case. Sinus bradycardia and CAVB are usually easy to diagnose, but BAB has a tendency to be sustained and shows a high degree of resemblance with 2:1 AVB when diagnosed during mid-gestational. As BAB resolves without treatment and 2:1 AVB may respond to treatment with fluorinated steroids, a correct diagnosis becomes an issue of major importance to avoid unnecessary treatment of harmless and spontaneously reversing conditions.

Ultrasonographic diagnosis of delayed atrioventricular conduction during fetal life: a reliability study

OBJECTIVE

The objective of the study was to evaluate the reliability of the 2 most commonly used ultrasonographic approaches for monitoring fetal atrioventricular conduction time (AVCT): (1) superior vena cava/ascending aorta (SVC/AA), and (2) left ventricular inflow/outflow tract (LVI/O) Doppler recordings.

STUDY DESIGN

Echographic studies from fetuses followed up for first-degree atrioventricular block (AVB-1) between 1998 and 2008 were reviewed. The ability to identify atrial contractions in the same fetuses by the SVC/AA and LVI/O approaches was analyzed.

RESULTS

Sixty-six studies of 13 fetuses with AVB-1 were available. Atrial contractions were visible in all SVC/AA studies. With the LVI/O approach, atrial contractions could not be identified in 26 studies (39%). AVCT delay was significantly greater in the nonidentifiable compared with the identifiable atrial contraction group (P < .001). Differences in heart rate and gestational age were not significant.

CONCLUSION

The LVI/O is unsuitable for prenatal screening of conduction system anomalies.

Controversies in the therapy of isolated congenital complete heart block

Controversies in the therapy of congenital complete heart block are reviewed in terms of the timing of pacemaker implantation, the type and complications of pacing and its role in the presence of myocardial dysfunction. Drug treatment may be useful in selected cases in the presence of pleural effusions, ascites and hydrops of the fetus, but have no effect on complete heart block. Administration of fluorinated steroids in anti-Ro antibody-positive mothers with the aim of preventing complete heart block has given controversial results. Because of the variety of the clinical presentations, especially in regard to pacing therapy, it is mandatory to refer patients with congenital complete heart block to specialized centers with adequate resources and experienced personnel.

Anti-Ro52/SSA antibody-exposed fetuses with prolonged atrioventricular time intervals show signs of decreased cardiac performance

OBJECTIVE

To investigate if anti-Ro/SSA antibody-exposed fetuses with prolonged atrioventricular (AV) time intervals also have prolongation of the isovolumetric contraction time (ICT).

METHODS

Seventy-eight anti-Ro/SSA (including 70 anti-Ro52) antibody-exposed fetuses at risk for congenital heart block (CHB) were followed weekly, between 18 and 24 weeks of gestation, with two Doppler echocardiographic methods designed to detect signs of first-degree AV block. One of these AV time measurements, using hemodynamic events from the mitral valve and aortic outflow as indirect markers of atrial and ventricular depolarization (MV-Ao), was also used to calculate a time interval representing an early phase of systolic cardiac performance, i.e. the ICT. Two hundred and eighty-four women with normal pregnancies served as controls for AV time intervals and another 106 were used to establish an ICT reference range.

RESULTS

Strong positive relationships were found between ICT and MV-Ao time intervals (r = 0.91, P < 0.001), as well as between ICT and time intervals obtained from the superior vena cava and aorta (r = 0.85, P < 0.001). The ICT was estimated to contribute more than 50% of the total AV time prolongation. Abnormal AV time and ICT intervals were only seen in anti-Ro52 positive pregnancies.

CONCLUSIONS

The ICT is an important contributor to prolongation of AV time intervals. This observation suggests that anti-Ro52/SSA antibody-exposed fetal hearts have not only disturbed electrical conduction but also decreased mechanical performance. Moreover, our findings have implications for the interpretation of AV time intervals used for surveillance of fetuses at risk for developing CHB.

Fetal Doppler mechanical PR interval: correlation with fetal heart rate, gestational age and fetal sex

OBJECTIVES

To establish normal fetal values for the mechanical PR interval by pulsed-wave Doppler at 16-36 weeks of gestation, and to evaluate the influence of fetal heart rate (FHR), gestational age (GA) and fetal sex.

METHODS

Fetal mechanical PR intervals were evaluated prospectively by obstetric ultrasound examination. Healthy mothers with sonographically normal fetuses from singleton pregnancies were included. Mechanical PR intervals were measured from simultaneous mitral and aortic Doppler waveforms, from the onset of left atrial contraction (mitral A-wave) to the onset of left ventricular ejection (aortic pulse wave). Simple and multiple linear regression analyses were performed to examine the correlation between PR interval and GA, FHR and fetal sex.

RESULTS

We evaluated 336 fetuses at 16-36 weeks. The mean +/- SD FHR was 143.4 +/- 8.3 beats per min (bpm). The PR intervals had a typical Gaussian distribution with a mean +/- SD of 122.4 +/- 10.3 ms. Robust linear regression showed that the PR increased by about 0.40 ms (95% CI, 0.22-0.58) per gestational week (P < 0.001), and this relationship remained after adjustment for FHR and fetal sex. PR intervals diminished by 1.4 (95% CI, 0.75 to 2.0) ms for each 5 bpm increase in FHR (P < 0.001), independently of GA and fetal sex. No fetal sex differences were observed.

CONCLUSIONS

We provide normal fetal values for the mechanical PR interval at 16-36 weeks of gestation. Mechanical PR intervals in normal fetuses are influenced by GA and FHR independently, and both variables should be taken into account when evaluating fetuses at risk for congenital heart block.

Serologic follow-up of children born to mothers with Ro/SSA autoantibodies

Neonatal lupus erythematosus (NLE) develops in foetuses of mothers with Ro/SSA and La/SSB antibodies and may include foetal atrioventricular block and dermatologic manifestations. In this study, we investigated postnatal Ro and La IgG, IgA and IgM antibody levels up to 1 year of age in 32 children born to Ro/SSA positive mothers. Antibody levels were correlated with NLE manifestations, and the role of breast feeding in transfer of autoantibodies from mother to child was evaluated. Ro52, Ro60 and La IgG antibodies all transferred from the mothers to their foetus in utero and were present in the infant at birth as detected by enzyme-linked immunosorbent assay using recombinant antigens and a synthetic peptide. A significant decrease in Ro52, Ro60 and La IgG autoantibody levels of the infants was observed from birth to 4-5 weeks of age (P < 0.05, P < 0.05 and P < 0.01). Ro- and La-specific IgA and IgM antibodies were detected in the serum from a subset of mothers. However, Ro- and La-specific IgA and IgM antibody levels were low or non-detectable in children raised both with and without breastfeeding. Furthermore, NLE skin lesions developed independently of breastfeeding. Our findings support a role for placental materno-foetal transfer of IgG autoantibodies in the pathogenesis of NLE and indicate that refraining from breastfeeding does not protect from NLE skin involvement.

[Fetal ultrasonography and Doppler in isolated congenital heart block]

Isolated congenital heart block is linked to transplacental passage of maternal anti-SSA/Ro and/or anti-SSB/La antibodies that may be related to a connective tissue disease. Ultrasonography and Doppler are essential to screen fetus at risk. They allow the diagnosis of first- and second-degree blocks which are probably preliminary stages in conducting tissue's injury. In these situations, a maternal treatment by fluorinated steroids can be proposed because of its possible effect on partial blocks. However, these early signs of nodal injury can be lacking: some fetus present a complete heart block without previously detected less advanced block. Moreover, the significance of first-degree block is unclear since it could reverse spontaneously. Other markers of nodal injury would be valuable. In case of complete congenital heart block, ultrasonography is useful to detect congestive heart failure and help the obstetrical management when unfavorable prognostic signs occur.

Cardiac manifestations of neonatal lupus erythematosus: guidelines to management, integrating clues from the bench and bedside

One of the strongest clinical associations with autoantibodies against components of the SSA/Ro-SSB/La ribonucleoprotein complex is the development of congenital heart block in an offspring, an alarming prospect facing 2% of primigravid mothers with these reactivities. This risk is increased tenfold in women who have had a previous child with congenital heart block. Accumulated evidence suggests that anti-SSA/Ro and anti-SSB/La antibodies are necessary but insufficient for fetal disease. Basic and clinical research is heavily focused on identifying fetal and environmental factors that convert disease susceptibility to disease development. A disturbing observation that has emerged from current research efforts is the rapidity of disease progression, with advanced heart block and life-threatening cardiomyopathy being observed less than 2 weeks after detection of a normal sinus rhythm. Once third-degree block is unequivocally identified, reversal has never been achieved, despite dexamethasone treatment. Accordingly, strategies aimed at preventing disease before irrevocable scarring ensues assume a high priority. One approach has been the implementation of serial echocardiography to monitor for a prolonged PR interval. Intravenous immunoglobulin is being evaluated as a potential prophylactic approach in mothers who have previously had an affected child.

Early Diagnosis and Treatment of Atrioventricular Block in the Fetus Exposed to Maternal Anti-SSA/Ro-SSB/La Antibodies

Background— A fetus exposed to maternal anti-SSA/Ro or anti-SSB/La antibodies (or both) may develop complete atrioventricular block (AVB), which results in high prenatal and postnatal morbidity and mortality. Until recently, only high-grade AVB could be diagnosed in utero. The tissue velocity–based fetal kinetocardiogram (FKCG) enables accurate measurement of AV conduction time and diagnosis of low-grade AVB. In the present multicenter observational study, we used FKCG to detect first-degree AVB in fetuses at risk.

Methods and Results— FKCG was performed in 70 fetuses of 56 mothers who were positive for anti-SSA/Ro and/or anti-SSB/La. Fetuses were monitored with weekly FKCG from 13 to 24 weeks’ gestation, followed by monthly assessments until delivery in unaffected fetuses and weekly assessments in affected fetuses. AV conduction in 70 at-risk and 109 normal fetuses was compared. FKCG was obtained readily in all fetuses; 6 showed first-degree AVB (AV conduction time >2 z scores above normal mean) at 21 to 34 gestational weeks. Immediate maternal treatment with dexamethasone resulted in normalization of AV conduction in all affected fetuses within 3 to 14 days. AV conduction time in the remaining 64 untreated fetuses remained normal throughout gestation. The ECG PR interval immediately after birth was normal in all affected newborns. No child developed AVB or cardiomyopathy in the subsequent 1- to 6-year (median 4-year) follow-up.

Conclusions— The present findings suggest that an FKCG can detect first-degree AVB in the fetus exposed to maternal anti-SSA/Ro or anti-SSB/La antibodies (or both). Dexamethasone given on detection was associated with normalized AV conduction in fetuses with first-degree AVB. No fetus in the present study developed complete prenatal or postnatal AVB.

Fetal Arrhythmias: A Clinical Review

Fetal rhythm abnormalities occur in 2% of pregnancies. They are usually identified by the obstetrician or midwifes after 20 weeks. There are four different methods used to assess fetal arrhythmias: scalp electrodes attached to electrocardiographic recordings, magnetocardiography (FMCG), fetal electrocardiographic recordings from the maternal abdomen, and fetal echocardiography (M-mode, pulsed-Doppler, Tissue-Doppler). In everyday practice the Doppler method was found to be the most useful method in the diagnosis and therapy of fetal arrhythmias. Doppler derived mechanical PR interval raised the possibility of refining the prenatal diagnosis of AV conduction abnormalities. A PR interval of >150 ms on Doppler, FMCG or postnatal ECG has been determined to be prolonged. Extrasystoles are most common cause of fetal arrhythmias, and are most often premature atrial contractions (PACs), what are usually identified in third trimester fetuses and their frequency may be highly variable. These are usually benign, resolving just before or shortly after birth. The follow-up is necessary, because some (1-3%) of affected fetuses have intermittent runs of supraventricular tachycardia. Ventricular tachycardia is rare during fetal life. With echocardiography in the setting of fetal tachycardia the findings of atrioventricular dissociation with a ventricular rate that is faster than the atrial rate suggests ventricular tachycardia. If there is 1:1 retrograde conduction it is impossible to distinguish between ventricular and supraventricular tachycardia. Atrial flutter accounted for 26.2% of all cases of fetal tachyarrhythmias and supraventricular tachycardia for 73.2%. Fouron and coworkers proposed to plan the management of the fetal tachyarrhythmia based on analysis of pulsed-Doppler recordings of fetal heart's blood flow. They determined short V-A tachycardia, when V-A (ventriculoatrial period) was shorter than AV (atrio-ventricular period) period. In the therapy of fetal supraventricular tachycardia there are different protocols, the most commonly used drugs are: digoxin, sotalol, amiodarone, flecainide. Persistent fetal sinus bradycardia is a rare condition and has been reported with central nervous system abnormalities, maternal treatment with beta blockers, excessive vagal tone, hydrops, long QT syndrome, intrauterine growth retardation and could be a sign of maternal anti-SSA/Ro antibodies. Prenatal sinus bradycardia or recognition of 2nd degree AV block may lead to early detection and treatment of long QT syndrome. Early detection of incomplete AV block, in cases of maternal anti SSA, SSB autoantibodies, successfully identifies a group at highest risk developing permanent AV block. The anti-inflammatory effects of dexamethasone might have interrupted on-going damage of the conduction system secondary to maternal autoantibodies. If the fetal arrhythmia resulted fetal hydrops, the mortality is high and the risk of late neurological morbidity must be taken into consideration. As a result of close follow-up, transplacentar treatment and well-organized perinatal management, the survival of sustained fetal arrhythmia significantly improved (50% versus 15%).

Antibodies to amino acid 200-239 (p200) of Ro52 as serological markers for the risk of developing congenital heart block

Maternal autoantibodies to the p200-epitope of Ro52 have been suggested to correlate with development of congenital heart block. The aim of the present study was to evaluate the clinical relevance and predictive value of p200-antibodies in high-risk pregnancies. Sera from 515 Finnish, Swedish and American women were included in the study. Sera originated from 202 mothers with an infant affected by second- or third-degree atrioventricular block (AVB), 177 mothers with rheumatic disease having infants with normal heart rate and female blood donors (n = 136). A novel serological assay for Ro52 p200-antibodies with intra- and inter-assay variability of 3% and 3.8% respectively was developed. Mothers of children affected by AVB II-III had significantly higher p200-antibody levels than mothers with rheumatic disease having children with normal heart rate (P < 0.001). In the Swedish cohort, a distinction between foetuses with normal conduction, AVB I, AVB II and III was possible. A significant difference in anti-p200 levels between AVB I and AVB II-III groups compared with foetuses with normal conduction (P < 0.05 and P < 0.01) was observed. Using p200-antibodies as a second step analysis in Ro52-positive pregnancies increased the positive predictive value for foetal cardiac involvement (AVB I, II or III) from 0.39 (0.27-0.51) to 0.53 (0.37-0.68). In conclusion, Ro52 p200-antibodies may occur in women with unaffected children, but levels are significantly higher in mothers of children with congenital heart block and are suggested as a relevant marker in evaluating the risk for foetal AV block.

Outcome and growth of infants fetally exposed to heart block-associated maternal anti-Ro52/SSA autoantibodies

OBJECTIVE

The purpose of this work was to analyze outcome with focus on growth in infants fetally exposed to heart block-associated maternal anti-Ro52/SSA autoantibodies and identify maternal factors other than the autoantibodies increasing the risk of fetal heart block.

PATIENTS AND METHODS

Thirty-two pregnancies in 30 anti-Ro52-positive mothers were included. Seven fetuses developed second-degree or third-degree atrioventricular block, 8 developed first-degree atrioventricular block, and 17 had normal atrioventricular conduction, as diagnosed by using Doppler echocardiography. Three of 6 surviving fetuses with second-degree or third-degree atrioventricular block received treatment with fluorinated steroids. Two fetuses with second-degree atrioventricular block converted to first-degree atrioventricular block without any signs of progression during the study period. Maternal and longitudinal infant data were collected from planned neonatal follow-up and childhood health records from birth to 12 months of age in 31 survivors.

RESULTS

Women giving birth to infants with prenatal second-degree or third-degree atrioventricular block were older and with higher parity than those with first-degree atrioventricular block or normal atrioventricular conduction. Second-degree or third-degree atrioventricular block pregnancies were <40 completed weeks, whereas pregnancies with first-degree atrioventricular block or normal atrioventricular conduction had a normal duration. Fetuses with second-degree or third-degree atrioventricular block were retarded by -0.98 +/- 0.77 SD in weight at birth and did not show any catch-up during infancy. In contrast, fetuses with first-degree atrioventricular block or normal atrioventricular conduction had a weight reduction of -0.51 +/- 1.01 SD with a catch-up during the first months after birth.

CONCLUSIONS

This report documents that newborns with autoantibody-mediated second-degree or third-degree atrioventricular block are retarded in growth, with no catch-up during infancy, whereas fetuses with first-degree atrioventricular block or normal atrioventricular conduction have a normal growth soon after birth. Increased maternal age and/or parity seem to carry an increased risk for fetal heart block.

Utility of cardiac monitoring in fetuses at risk for congenital heart block: the PR Interval and Dexamethasone Evaluation (PRIDE) prospective study

BACKGROUND

Anti-SSA/Ro-associated third-degree congenital heart block is irreversible, prompting a search for early markers and effective therapy.

METHODS AND RESULTS

One hundred twenty-seven pregnant women with anti-SSA/Ro antibodies were enrolled; 95 completed an evaluable course in 98 pregnancies. The protocol included fetal echocardiograms performed weekly from 16 to 26 weeks' gestation and biweekly from 26 to 34 weeks. PR intervals >150 ms were considered prolonged, consistent with first-degree block. Ninety-two fetuses had normal PR intervals. Neonatal lupus developed in 10 cases; 4 were neonatal lupus rash only. Three fetuses had third-degree block; none had a preceding abnormal PR interval, although in 2 fetuses >1 week elapsed between echocardiographic evaluations. Tricuspid regurgitation preceded third-degree block in 1 fetus, and an atrial echodensity preceded block in a second. Two fetuses had PR intervals >150 ms. Both were detected at or before 22 weeks, and each reversed within 1 week with 4 mg dexamethasone. The ECG of 1 additional newborn revealed a prolonged PR interval persistent at 3 years despite normal intervals throughout gestation. No first-degree block developed after a normal ECG at birth. Heart block occurred in 3 of 16 pregnancies (19%) in mothers with a previous child with congenital heart block and in 3 of 74 pregnancies (4%) in mothers without a previous child with congenital heart block or rash (P=0.067).

CONCLUSIONS

Prolongation of the PR interval was uncommon and did not precede more advanced block. There was a trend toward more congenital heart block in fetuses of women with previously affected offspring than those without previously affected offspring. Advanced block and cardiomyopathy can occur within 1 week of a normal echocardiogram without initial first-degree block. Echodensities and moderate/severe tricuspid regurgitation merit attention as early signs of injury.

PR interval: a comparison of electrical and mechanical methods in the fetus

BACKGROUND

Mechanical surrogates are used to assess fetal cardiac electrical activity.

AIMS

To compare electrical PR interval measured using non-invasive fetal electrocardiography (fECG) with mechanical atrioventricular (AV) interval using Doppler.

STUDY DESIGN AND SUBJECTS

Prospective study of 55 recordings made in 50 human fetuses. Those with structural heart defects, second degree or complete heart block were excluded.

OUTCOME MEASURES

Mechanical AV interval was measured from the onset of mitral A wave to onset of aortic ejection. Electrical PR interval was measured from a coherent averaged signal obtained using non-invasive fECG recorded from the maternal abdomen. Wilcoxon signed rank test was used to compare both methods. Agreement between AV and PR intervals was assessed using linear regression and by Bland-Altman plots. Bland-Altman analysis assessed inter-observer and intra-observer variability.

RESULTS

There was no significant difference in the heart rates of the 55 paired traces measured consecutively using both methods (p<0.35). AV interval was longer than PR (median [range] 116 [96-169] vs. 102 [75-143] ms; p<0.001), with mean difference -16.47 ms (95% Confidence Interval -43.43, 10.44), reflecting the increased proportion of the cardiac cycle measured. Using fECG, PR inter-observer and intra-observer mean differences were 0.4 ms (CI -7.29, 8.09) and 0.7 ms (CI -3.22, 4.62) respectively. R values for inter and intra-observer studies were 0.95 and 0.99 respectively. Using Doppler methods, AV inter-observer and intra-observer mean differences were -2.69 ms, (CI -15.33, 9.95) and 0.92 ms, (CI -9.41, 11.26) respectively. R values for AV measurements were 0.93 for inter-observer and 0.96 for intra-observer variation.

CONCLUSIONS

Non-invasive fECG is a robust tool to measure the PR interval with narrow limits of agreement.

Specificity and effector mechanisms of autoantibodies in congenital heart block

Complete congenital atrio-ventricular (AV) heart block develops in 2-5% of fetuses of Ro/SSA and La/SSB autoantibody-positive pregnant women. During pregnancy, the Ro/SSA and La/SSB antibodies are transported across the placenta and affect the fetus. Emerging data suggest that this happens by a two-stage process. In the first step, maternal autoantibodies bind fetal cardiomyocytes, dysregulate calcium homestasis and induce apoptosis in affected cells. This step might clinically correspond to a first-degree heart block, and be reversible. La/SSB antibodies can bind apoptotic cardiomyocytes and thus increase Ig deposition in the heart. The tissue damage could, as a second step, lead to spread of inflammation in genetically pre-disposed fetuses, progressing to fibrosis and calcification of the AV-node and subsequent complete congenital heart block. Early intrauterine treatment of an incomplete AV-block with fluorinated steroids has been shown to prevent progression of the heart block, making it clinically important to find specific markers to identify the high-risk pregnancies.

Fetal ECG: a novel predictor of atrioventricular block in anti-Ro positive pregnancies

OBJECTIVE

Approximately 2.8% of pregnancies are Ro/La antibody positive. 3-15% of fetuses develop complete heart block (CHB). First-degree atrioventricular heart block (1 degrees AVB) is reported in a third of Ro/La fetuses but as most have a normal postnatal ECG this may reflect inadequacies of Doppler measurement techniques.

METHODS

Comparison was made between mechanical (mPR) and electrical (ePR) intervals obtained prospectively using Doppler and non-invasive fetal ECG (fECG) in 52 consecutive Ro/La pregnancies in 46 women carrying 54 fetuses in an observational study at a fetal medicine unit. 121 mPR and 37 ePR intervals were recorded in 49 Ro/La fetuses. Five were referred with CHB and excluded. ePR was measured successfully in 35/37 (94%) and mPR was measured in all cases. 1 degrees AVB was defined as PR >95% CI. Logistic regression predicted abnormal final fetal rhythm from first mPR or ePR.

RESULTS

The ePR model gave 66.7% sensitivity (6 of 8 final abnormal fetal rhythm cases were predicted correctly in fetuses >20 weeks) and 96.2% specificity. mPR gave 44.4% sensitivity (4 of 9 cases) and 88.5% specificity. Z scores for ePR (zPR) were calculated from 199 normal fetuses. The area under the receiver operator characteristic (ROC) curve was 0.88 (95% CI, 0.754 to 1.007). A cut-off of 1.65 gave a sensitivity of 87.5% and specificity of 95% for those with prolonged and normal ePR intervals, respectively.

CONCLUSION

zPR is better than mPR at differentiating between normal and prolonged PR intervals, suggesting that fECG is the diagnostic tool of choice to investigate the natural history and therapy of conduction abnormalities in Ro/La pregnancies.

Doppler echocardiographic and electrocardiographic atrioventricular time intervals in newborn infants: evaluation of techniques for surveillance of fetuses at risk for congenital heart block

OBJECTIVE

To evaluate one novel and two previously reported Doppler flow velocimetric techniques to estimate atrioventricular (AV) time intervals, suggested to be useful for early identification of fetuses at risk for congenital heart block.

METHODS

In 22 newborn infants, Doppler tracings were obtained from the mitral valve/aortic outflow and the superior vena cava/ascending aorta, as an ECG was recorded simultaneously. AV time intervals were measured using the onsets of the mitral A-wave/aortic outflow (MV-Ao), superior vena cava a-wave/aortic flow (SVC-Ao), and mitral A-wave/mitral valve closure (MV) as indirect markers of electrical atrial/ventricular activation.

RESULTS

Close positive linear relationships to the electrocardiographic PR interval were demonstrated for the MV-Ao (r = 0.82, S(y/x) = 7.4 ms), SVC-Ao (r = 0.85, S(y/x) = 6.8 ms), and MV (r = 0.92, S(y/x) = 3.8 ms) approaches. Both techniques using the aortic flow to indicate ventricular activation overestimated the PR interval: the MV-Ao by + 32 +/- 7.7 ms (mean +/- SD) and the SVC-Ao approach by + 22 +/- 7.0 ms. The new MV approach using mitral closure for the same purpose did not overestimate the PR interval, but there was a trend towards underestimation of the PR intervals as time intervals increased.

CONCLUSIONS

When systematic differences between echocardiographic and electrocardiographic AV time intervals are compensated for, all three techniques are useful to get indirect estimates of the PR interval. As MV recordings only need insonation of a single valve, and are thus easier to obtain, this technique may be of value as a first screening method to identify fetuses in need for further surveillance. In cases with AV time prolongation the SVC-Ao method seems superior.

Assessment of fetal atrioventricular time intervals by tissue Doppler and pulse Doppler echocardiography: normal values and correlation with fetal electrocardiography

OBJECTIVE

To establish gestational age-specific reference values of normal fetal atrioventricular (AV) time interval by spectral tissue Doppler imaging (TDI) and pulse-wave Doppler (PD) methods, and to assess their correlation with signal-averaged fetal PR intervals (ECG).

DESIGN

Cohort study.

SETTING

Tertiary centre for fetal cardiology. PATIENTS AND MEASURES: 131 pregnant women between 14 and 42 weeks' gestation underwent 196 fetal echocardiograms and 158 fetal ECG studies. TDI-derived AV intervals were measured as the intervals from atrial contraction (Aa) to isovolumic contraction (IV) and from Aa to ventricular systole (Sa) at the right ventricular free wall. PD-derived AV intervals were measured from simultaneous left ventricular inflow/outflow (in/out) and superior vena cava/aorta (V/AO) recordings.

RESULTS

Measurements were possible by ECG in 61%, by TDI in 100%, by in/out in 100% and by V/AO in 97% of examinations. Aa-IV correlated significantly better with PR intervals (y = 0.67x + 38.29, R(2) = 0.15, p < 0.0001, mean bias 8.0 ms) than did in/out (R(2) = 0.10, p = 0.002, bias 18.7 ms) and V/AO (R(2) = 0.06, p = 0.02, bias 12.4 ms). Gestational age and AV intervals were positively correlated with all imaging modalities (R(2) = 0.19-0.31, p < 0.0001).

CONCLUSION

This study showed the feasibility of fetal AV interval measurements by TDI, and established gestational age-specific reference data. TDI-derived Aa-IV intervals track ECG PR intervals more closely than PD-derived AV intervals and thus should be used as the ultrasound method of choice in assessing fetal AV conduction.

Doppler tissue imaging in the assessment of atrioventricular conduction time: validation of a novel technique and comparison with electrophysiologic and pulsed wave Doppler-derived equivalents in an animal model

Accurate assessment of atrioventricular conduction time (AVCT) is crucial for early detection of evolving fetal heart block. Simultaneous pulsed wave Doppler (PD) interrogation of left ventricular inflow and outflow is mainly used to study fetal AVCT. Limitations of this modality include its dependency on loading conditions and merging early and late diastolic inflow waves at faster heart rate (HR). Sequential analysis of atrioventricular myocardial motion by Doppler tissue imaging (DTI) might be more useful in this regard. In 15 open-chest pigs, AVCT was measured by PD, DTI, and electrocardiogram at baseline HR and during incremental atrial pacing up to 200 beats/min. Electromechanical delay and pre-ejection period were assessed at baseline and maximal HR. DTI-derived AVCT correlated better with PR intervals and allowed measurements at faster HRs than did PD (P < .05). Pre-ejection period prolonged with faster HR (P < .001), unlike electromechanical delay. In conclusion, DTI allows more accurate measurement of AVCT over a wider HR range than does PD.