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

Fetal PR Interval in Pregnancies with Intrahepatic Cholestasis of Pregnancy: A Case-Control Study

OBJECTIVE

 This study had three purposes: first, to explore differences in fetal cardiac function in patients with and without intrahepatic cholestasis of pregnancy (ICP) based on PR interval (the interval between the beginning of the atrial contraction and the beginning of the ventricular contraction). Second, to explore a potential correlation between PR interval and bile acid levels in pregnant women with ICP. Third, to study changes in PR interval of fetuses from pregnant women with ICP after administration of ursodeoxycholic acid (UDCA).

STUDY DESIGN

 This was a prospective observational case-control study. ICP was defined as palmar plantar pruritus of nocturnal predominance for more than 1 week associated with a total bile acid level >10 μmol/L. Control cases were women with pregnancies scheduled for induction or elective cesarean section at term.

RESULTS

 One hundred and ten women with ICP and 72 controls were included in the study. Median gestational age at inclusion was 35.9 weeks. Median PR interval was significantly longer in fetuses of women with ICP (122 vs. 102 ms, p < 0.001). There was a significant correlation between bile acid levels and PR interval (rho = 0.723, p < 0.001). In 22 fetuses, the median PR interval decreased significantly following UDCA administration (134 vs. 118 ms, p = 0.004).

CONCLUSION

 PR interval is longer in fetuses of women with ICP. PR interval was significantly correlated with bile acid levels, and administration of UDCA significantly reduced PR interval.

KEY POINTS

· Differences in fetal cardiac function in patients with and without intrahepatic cholestasis.. · PR interval and bile acid levels in pregnant women with intrahepatic cholestasis.. · Changes in PR interval of fetuses from pregnant women with ICP after use of UDCA..

The assessment of fetal cardiac functions in pregnancies with autoimmune diseases: a prospective case-control study

OBJECTIVES

This study aimed to assess the effect of the inflammatory process on fetal cardiac functions in pregnant women with autoimmune diseases (AID).

METHODS

This prospective study included 36 pregnant women with diagnosed AID. Nineteen systemic lupus erythematosus, 12 antiphospholipid syndrome, 5 Sjögren's syndrome, and 72 healthy pregnancies were included. Fetal cardiac functions were evaluated with pulsed-wave, tissue Doppler, and M-mode echocardiography.

RESULTS

Sociodemographic data were similar in both groups. Significant increases were found in tricuspid E (43.5 ± 0.9, p<0.001) and A (59.2 ± 2.2, p<0.001) and E/A (0.74 ± 0.03, p<0.001), E'/A' (0.64 ± 0.15, p<0.001), E/E' (6.5 ± 0.6, p<0.001), and left ventricular myocardial performance index (0.54 ± 0.03, p=0.005). We demonstrated a significant decrease in tricuspid E' (6.7 ± 0.6, p<0.001) and S' (6.9 ± 1, p<0.001) and in TAPSE (7.7 ± 0.5, p=0.002). We also found a significantly prolonged PR interval (130 ± 8, p<0.001). There was a significant increase in E' (6.8, p=0.033) and a significant decrease in E/E' ratio (6.4, p=0.027) in the group using hydroxychloroquine (HCQ) compared to non-users.

CONCLUSIONS

We found that pregnancy with autoimmune diseases affects fetal heart functions. Additionally, hydroxychloroquine may positively affect the heart of AID fetuses. This information might be useful to clinicians in the follow-up of cardiovascular diseases.

Intrahepatic cholestasis of pregnancy and fetal cardiac dysfunction: a systematic review and meta-analysis

OBJECTIVE

Intrahepatic cholestasis of pregnancy is associated with adverse perinatal outcomes. Fetal cardiac dysfunction may be 1 part of the pathophysiology of pregnancies complicated by intrahepatic cholestasis of pregnancy. This systematic review and meta-analysis aimed to evaluate the association between intrahepatic cholestasis of pregnancy and fetal cardiac dysfunction.

DATA SOURCES

Systematic searches were performed on the databases of Medline, Embase, and Cochrane Library (up to March 2, 2023) for studies evaluating fetal cardiac function in pregnancies complicated by intrahepatic cholestasis of pregnancy in addition to the reference lists of included studies.

STUDY ELIGIBILITY CRITERIA

Studies were eligible for inclusion if they assessed the fetal cardiac function by fetal echocardiography in women with intrahepatic cholestasis of pregnancy (mild or severe) and compared with fetuses of healthy pregnant women. The studies published in English were included.

METHODS

The quality of the retrieved studies was assessed using the Newcastle-Ottawa Scale. Data on fetal myocardial performance index, E wave/A wave peak velocities ratio, and PR interval were pooled for the meta-analysis using random-effects models. The results were presented as weighted mean differences and 95% confidence intervals. This meta-analysis was registered with the International Prospective Register of Systematic Reviews (registration number: CRD42022334801).

RESULTS

A total of 14 studies were included in this qualitative analysis. Of note, 10 studies that reported data on fetal myocardial performance index, E wave/A wave peak velocities ratio, and PR interval were included in the quantitative analysis and showed a significant association between intrahepatic cholestasis of pregnancy and fetal cardiac dysfunction. Significantly higher fetal left ventricular myocardial performance index values (weighted mean difference, 0.10; 95% confidence interval, 0.04-0.16) and longer fetal PR intervals (weighted mean difference, 10.10 ms; 95% confidence interval, 7.34-12.86) were revealed in pregnancies complicated by intrahepatic cholestasis of pregnancy. Compared with the situation in pregnancies complicated by mild intrahepatic cholestasis of pregnancy, PR intervals were even longer in pregnancies complicated by severe intrahepatic cholestasis of pregnancy (weighted mean difference, 5.98 ms; 95% confidence interval, 0.20-11.77). There was no significant difference in fetal E wave/A wave peak velocities ratio between the group with intrahepatic cholestasis of pregnancy and the healthy pregnant group (weighted mean difference, 0.01; 95% confidence interval, -0.03 to 0.05).

CONCLUSION

Our findings supported the idea that intrahepatic cholestasis of pregnancy is associated with overall impaired fetal myocardial performance and impaired fetal cardiac conduction system. However, current evidence about the association between fetal cardiac dysfunction and intrahepatic cholestasis of pregnancy-induced stillbirth is lacking. Further studies are needed to reveal the relationship between fetal cardiac dysfunction and adverse perinatal outcomes in pregnancies complicated by intrahepatic cholestasis of pregnancy.

Measurement of fetal atrioventricular intervals in pregnant women with anti-SSA/Ro antibodies

PURPOSE

The objective of our study was to compare and consider reference values of fetal atrioventricular (AV) intervals as measured by four different pulsed Doppler wave techniques (left ventricular inflow/outflow [LV in/out], pulmonary vein/pulmonary artery [PV/PA], innominate vein/ascending aorta [InnV/AA], and supra vena cava/ascending aorta [SVC/AA]) in pregnant women with anti-SSA/Ro antibodies.

METHODS

Between March 2014 and September 2020, 52 pregnant women with anti-SSA antibodies were enrolled. No bradyarrhythmia was observed in the group. A pulsed Doppler examination of the fetal heart was performed to obtain measurements of the mechanical Doppler AV interval. Doppler measurements were performed using four methods: LV in/out, PV/PA, InnV/AA, and SVC/AA. A statistical analysis was performed to examine the mean, standard deviation, significant difference, and correlation of the four methods. The detection rate of each method was also calculated.

RESULTS

There was no significant difference in the AV intervals between any of the four methods. There was also a positive correlation in the AV intervals of each of the four methods. The fetal heart rate and AV interval showed no correlation. The gestational age and AV interval also showed no correlation. The detection rate was highest for LV in/out (62.6%, 95% confidence interval: 56.5-68.4).

CONCLUSION

All four pulsed Doppler methods are useful for measuring AV intervals. The most practical method is LV in/out.

Case report: Prenatal diagnosis of fetal non-compaction cardiomyopathy with bradycardia accompanied by de novo CALM2 mutation

We herein report what appears to be the first case of fetal non-compaction cardiomyopathy in both ventricles accompanied by a mutation in the calmodulin gene (CALM2). A 25-year-old woman was referred to our hospital at 25⁺¹ weeks of gestation for evaluation of fetal defects. Prenatal echocardiography showed biventricular non-compaction cardiomyopathy with sinus bradycardia. After termination of the pregnancy, fetal biventricular non-compaction cardiomyopathy was confirmed by autopsy and histopathologic examination. Additionally, whole-exome sequencing of genomic DNA demonstrated a de novo heterozygous mutation (c.389A > G; p.D130G) in CALM2, whereas the parents were normal. In this case report, we highlight the importance of prenatal ultrasound and genetic testing in fetal non-compaction cardiomyopathy with arrhythmia.

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.

Diagnosis and Management of Fetal Autoimmune Atrioventricular Block

Autoimmune congenital atrioventricular block (CAVB) has been extensively studied in recent decades. The American Heart Association published guidelines for monitoring pregnant women with anti-Ro/Sjögren’s syndrome antigen A (SSA) or anti-La/Sjögren’s syndrome antigen B (SSB) autoantibodies, which are considered to increase the risk of CAVB. Information about the natural history of the disease in utero has contributed to the detection of fetuses with CAVB in the treatable stage. Hydroxychloroquine (HCQ) may be used to prevent CAVB. The lack of large randomized control trials is a major drawback to fully confirm the benefits of fluorinated steroids such as dexamethasone. Although, when combined with a β-sympathomimetic agent, the outcome of administering a fluorinated steroid in complete CAVB is still controversial. Novel treatments targeting the immunological process might prevent the recurrence of CAVB in pregnant women with previously affected children.

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.

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.

Causes of fetal third-degree atrioventricular block and use of hydroxychloroquine in pregnant women with Ro/La antibodies

INTRODUCTION/OBJECTIVES

Complete congenital atrioventricular block (AVB) may be due to cardiac malformations or the presence of maternal antibodies (autoimmune AVB). Our objective was to estimate the prevalence of autoimmune AVB among all AVB in newborns treated at our hospital. Secondly, we estimated the prevalence of AVB among mothers with anti-Ro/La antibodies and examined the relationship of those fetal AVB with mother's use of hydroxychloroquine during pregnancy.

METHODS

Retrospective cohort in which we reviewed electronic medical records from years 2000 to 2014 of (a) all mothers with children born with third degree AVB and (b) all pregnant women with anti-Ro/La-positive antibodies.

RESULTS

Twenty-three AVBs were diagnosed. Ten (43.5%, 95% CI 23.2-65.5) were associated with maternal rheumatologic disease. The remaining 13 were associated with cardiac malformations. Sixty-two pregnancies in 47 mothers with Ro/La antibodies were identified; eight (12.9%, 95% CI 5.7-23.8) suffered AVB. Fourteen mothers consumed hydroxychloroquine during full pregnancy (one newborn (7.1%) suffered AVB) and 48 did not (7 newborns with AVB (14.6%); p = 0.5).

CONCLUSIONS

All congenital AVB diagnosed at our hospital without cardiac malformations were associated with a maternal rheumatologic disease/antibodies. Therefore, if a AVB is diagnosed in a newborn without structural heart disease, the mother should be studied for an autoimmune disease. We found a high prevalence of AVB among mothers with anti-Ro/La antibodies. Although not statistically significant, AVBs in mothers with Ro/La antibodies were numerically more frequent in those not using hydroxychloroquine.Key Points• Although structural heart malformations were the predominant cause of third-degree AVB, autoimmune AVB was still a significant cause.• The distinction between structural or non-structural cause of AVB constitutes an essential issue since it determines the prognostic of these fetuses in terms of complications.• Although not statistically significant, AVBs in mothers with Ro/La antibodies were more frequent in those not using hydroxychloroquine.• If an AVB is diagnosed in a newborn without structural heart disease, the mother should be studied for an autoimmune disease.

Pulsed Doppler fetal atrioventricular interval measurement: Assessment of a new image scoring method

OBJECTIVES

We propose an image scoring method to improve the quality and the reproducibility of measurement of the AV interval before establishing reference tables of the measurements and studies on the prevention and treatment of first-degree AV block especially if the first child has been diagnosed AV block.

METHOD

Prospective study from May 2015 to June 2016. Sonographers were asked to measure AV interval with pulsed Doppler in a five-chamber view in standard second-trimester screening before and after having received our image scoring method. Images were scored by 2 blinded reviewers.

RESULTS

The intra-class correlation coefficient (ICC) between the two reviewers for the overall score was 0.91. On average, the measurement quality increased by 2.5 points/10 (95% CI 1.0-4.0). In the second set of images, after the scoring method was given, the score stared at 6.50 for the first image, with a significant improvement of 0.18 (p = 0.016) per subsequent image comparing to a non significant improvement for the first set of image. There was a significant improvement in intra-observer reliability, ICC: 0.680 [95% CI 0.606-0.854] versus 0.458 [95% CI 0.140-0.651].

CONCLUSION

The use of this scoring method is simple, reproducible and improves image quality and reproducibility of AV interval measurement in a five-chamber view.

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.

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.

A unique foetal case of left ventricular non-compaction associated with arrhythmia, structural cardiac anomalies, and agenesis of the ductus venosus

A 21-week gestational age foetus was diagnosed with left ventricular non-compaction, Ebstein's anomaly, sinus bradycardia, first-degree heart block, and agenesis of the ductus venosus. The prognosis was guarded given the constellation of findings, and the foetus was monitored closely. Despite a potentially poor outcome, the foetus survived. Prognosis in foetally diagnosed left ventricular non-compaction is usually poor; however, rarely, foetuses can survive postnatally.

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.

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.