FETAL ARRHYTHMIA DURING PREGNANCY AND LABOUR

Fetal premature atrial contractions: natural course, risk factors and adverse outcome

OBJECTIVES

Fetal premature atrial contractions (PAC) are usually benign but may be associated with congenital heart defect (CHD) and tachyarrhythmia, which in turn carry a risk of cardiac failure and fetal death. We aimed to explore the frequency of adverse outcome and to identify risk factors for tachyarrhythmia in pregnancies complicated by fetal PAC.

METHODS

This was a retrospective cohort study of fetuses diagnosed with PAC at two academic centers in Amsterdam, The Netherlands, between 2007 and 2022. Cases with a congenital anomaly and those with a prior diagnosis of CHD or other arrhythmias were excluded. M-mode and Doppler tracings were reanalyzed and the frequency of PAC was recorded. The incidence of the following adverse outcomes was examined: underlying CHD not identified at the 20-week fetal anomaly scan, tachyarrhythmia, other arrhythmia, administration of antiarrhythmic therapy and death. Risk factors for tachyarrhythmia were analyzed using odds ratios (OR).

RESULTS

In 24.1% of 1439 referred cases, PAC resolved before confirmation at the fetal medicine unit (FMU). Of the 939 included cases with confirmed PAC, the total incidence of adverse outcome was 6.8% (64/939). CHD was diagnosed in 14 (1.5% (95% CI, 0.9-2.5%)) cases, of which eight were diagnosed prenatally and six postnatally. Compared with baseline, the incidence of CHD was higher in the presence of fetal PAC (OR, 1.8 (95% CI, 1.0-3.3); P = 0.034). Tachyarrhythmia occurred prenatally and/or postnatally in 32 (3.4%) cases, of which eight (25.0%) showed signs of cardiac failure, and in 23 (71.9%) cases, antiarrhythmic therapy was required. No cases of tachyarrhythmia led to fetal or infant death. Risk factors for tachyarrhythmia were PAC with short runs of supraventricular tachycardia (OR, 98.7), blocked PAC (OR, 30.3), PAC in bigeminy (OR, 21.8), frequent PAC (one per 5-10 beats) (OR, 6.9), signs of cardiac failure (OR, 14.2) and the presence of a foramen ovale aneurysm (OR, 5.0).

CONCLUSIONS

PAC are generally benign and often resolve spontaneously. However, fetuses with an irregular heart rhythm should be referred for advanced ultrasonography, which should focus on classifying the type of PAC and risk of adverse outcome. When risk factors for tachyarrhythmia are identified, weekly fetal heart-rate monitoring is advised until resolution of the PAC. In the absence of risk factors, standard obstetric care may be sufficient, with additional instructions to report reduced fetal movements. Should tachyarrhythmia or cardiac failure develop, referral back to the FMU is indicated. © 2023 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Implications of fetal premature atrial contractions: systematic review

OBJECTIVE

Fetal heart-rate irregularities occur in 1-2% of pregnancies and are usually caused by premature atrial contractions (PAC). Although PAC are considered benign, they may be associated with cardiac defects and tachyarrhythmia. We aimed to determine the incidence of congenital heart defects (CHDs) and complications in fetuses with PAC.

METHODS

This was a systematic review and meta-analysis conducted in accordance with the PRISMA statement for reporting items for systematic reviews and meta-analyses. MEDLINE and EMBASE were searched from 1990 to June 2021 to identify studies on fetuses with PAC. The primary outcome was CHD; secondary outcomes were complications using the endpoints supraventricular tachyarrhythmia (SVT), cardiac failure and intrauterine fetal demise. Meta-analysis of proportions was performed, subdivided into high-risk and low-risk populations based on reason for referral. Pooled incidences with 95% CIs were calculated.

RESULTS

Of 2443 unique articles identified, 19 cohort studies including 2260 fetuses were included. The pooled incidence of CHD in fetuses with PAC was 2.8% (95% CI, 1.5-4.1%), when 0.6% is the incidence expected in the general population. The pooled incidence of CHD was 7.2% (95% CI, 3.5-10.9%) in the high-risk population and 0.9% (95% CI, 0.0-2.0%) in the low-risk population. SVT occurred in 1.4% (95% CI, 0.6-3.4%) of fetuses diagnosed with PAC. Cardiac failure was described in 16 fetuses (1.4% (95% CI, 0.5-3.5%)), of which eight were CHD-related. Intrauterine fetal demise occurred in four fetuses (0.9% (95% CI, 0.5-1.7%)) and was related to CHD in two cases.

CONCLUSIONS

Our findings suggest that the risk of CHD in fetuses with PAC is 4-5 times higher than that in the general population. CHD was present more frequently in the high-risk population. Consequently, an advanced ultrasound examination to diagnose PAC correctly and exclude CHD is recommended. Complications of PAC are rare but can result in fetal demise, thus weekly fetal heart-rate monitoring remains advisable to enable early detection of SVT and to prevent cardiac failure. © 2022 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Detection of fetal arrhythmias in non-invasive fetal ECG recordings using data-driven entropy profiling

Objective:Fetal arrhythmias are a life-threatening disorder occurring in up to 2% of pregnancies. If identified, many fetal arrhythmias can be effectively treated using anti-arrhythmic therapies. In this paper, we present a novel method of detecting fetal arrhythmias in short length non-invasive fetal electrocardiography (NI-FECG) recordings.Approach:Our method consists of extracting a fetal heart rate (FHR) time series from each NI-FECG recording and computing an entropy profile using a data-driven range of the entropy tolerance parameter r. To validate our approach, we apply our entropy profiling method to a large clinical data set of 318 NI-FECG recordings.Main Results:We demonstrate that our method (TotalSampEn) provides strong performance for classifying arrhythmic fetuses (AUC of 0.83) and outperforms entropy measures such as SampEn (AUC of 0.68) and FuzzyEn (AUC of 0.72). We also find that NI-FECG recordings incorrectly classified using the investigated entropy measures have significantly lower signal quality, and that excluding recordings of low signal quality (13.5% of recordings) increases the classification accuracy of TotalSampEn (AUC of 0.90).Significance:The superior performance of our approach enables automated detection of fetal arrhythmias and warrants further investigation in a prospective clinical trial.

Noninvasive fetal electrocardiography for the detection of fetal arrhythmias

OBJECTIVE

To assess whether noninvasive fetal electrocardiography (NI-FECG) enables the diagnosis of fetal arrhythmias.

METHODS

A total of 500 echocardiography and NI-FECG recordings were collected from pregnant women during a routine medical visit in this multicenter study. All the cases with fetal arrhythmias (n = 12) and a matching number of control (n = 14) were used. Two perinatal cardiologists analyzed the extracted NI-FECG while blinded to the echocardiography. The NI-FECG-based diagnosis was compared with the reference fetal echocardiography diagnosis.

RESULTS

NI-FECG and fetal echocardiography agreed on all cases (Ac = 100%) on the presence of an arrhythmia or not. However, in one case, the type of arrhythmia identified by the NI-FECG was incorrect because of the low resolution of the extracted fetal P-wave, which prevented resolving the mechanism (2:1 atrioventricular conduction) of the atrial tachycardia.

CONCLUSION

It is possible to diagnose fetal arrhythmias using the NI-FECG technique. However, this study identifies that improvement in algorithms for reconstructing the P-wave is critical to systematically resolve the mechanisms underlying the arrhythmias. The elaboration of a NI-FECG Holter device will offer new opportunities for fetal diagnosis and remote monitoring of problematic pregnancies because of its low-cost, noninvasiveness, portability, and minimal setup requirements.

Fetal dysrhythmias

Fetal cardiac dysrhythmias are potentially life-threatening conditions. However, intermittent extrasystoles, which are frequently encountered in clinical practice, do not require treatment. Sustained forms of brady- and tachyarrhythmias might require fetal intervention. Fetal echocardiography is essential not only to establish the diagnosis but also to monitor fetal response to therapy. In the last decade, improvements in ultrasound methodology and new diagnostic tools have contributed to better diagnostic accuracy and to a greater understanding of the electrophysiological mechanisms involved in fetal cardiac dysrhythmias. The most common form of supraventricular tachycardia - that caused by an atrioventricular re-entry circuit - should be differentiated from other forms of tachyarrhythmias, such as atrial flutter and atrial ectopic tachycardia. Ventricular tachycardia is rare in the fetus. Sustained tachycardias, intermittent or not, might be associated with the development of congestive heart failure and hydrops fetalis. Prompt treatment with either anti-arrhythmic drugs or delivery must be considered. Persistent fetal bradycardias associated with complete heart block are also potentially dangerous, whereas bradyarrhythmia due to blocked ectopy is well tolerated in pregnancy. Heart block can be associated with maternal anti-Ro/La autoantibodies or develop in fetuses with left atrial isomerism or with malformations involving the atrioventricular junction. The treatment of fetuses with immune-mediated heart block remains debatable. The use of antenatal steroid therapy is not widely accepted and there is concern over the risks and benefits of its use in the fetus. Direct fetal cardiac pacing has rarely been attempted.

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

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

Evaluation of fetal cardiac dysrhythmias with two-dimensional, M-mode, and pulsed Doppler ultrasonography

Forty-three patients with fetal cardiac dysrhythmia were referred to a tertiary ultrasound department for further evaluation. The patients were subdivided according to the type of dysrhythmia diagnosed. All patients with irregular fetal heart rate had a good perinatal outcome. Of the six patients with fetal tachycardia, two required in utero therapy with maternal digoxin, and one of these fetuses had a cardiac tumor. The eleven patients with fetal bradycardia had the worst perinatal outcome, with four deaths occurring. The results suggest that all patients with fetal tachycardia or bradycardia should have a complete fetal cardiac assessment in a center experienced with the management of such cases.

Clinical outcome and circulatory effects of fetal cardiac arrhythmia

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

Circulatory effects of fetal cardiac arrhythmias

The circulatory consequences of cardiac arrhythmia and its compensatory mechanisms were examined in utero in 37 fetuses. A combined real-time and 2-MHz pulsed Doppler technique was used to measure blood velocity for waveform analysis and flow estimation in the descending thoracic aorta of the fetuses. The pattern of blood velocity in the inferior vena cava was studied to classify the arrhythmia. Despite severe cardiac arrhythmias the aortic blood flow was within normal limits in all but one fetus which had associated cardiac malformation and congestive failure. The rising slope and the peak value of the maximum aortic velocity were significantly increased in the postpremature beats and in fetuses with atrioventricular block. The results support the validity of Frank-Starling's law for the fetal myocardium.

Evaluation and treatment of fetal arrhythmias

In a series of 31 cases referred for the evaluation of fetal arrhythmia, it was possible to identify the rhythm disturbance correctly using M-mode echocardiography. Cross-sectional echocardiography delineated structural abnormality where it occurred in association with an arrhythmia. Fifteen cases had premature atrial or ventricular contractions occurring in structurally normal hearts. These were not associated with perinatal mortality or morbidity in our series. Nine cases had complete heart block, three of which had structural cardiac anomalies. Seven cases were of atrial tachycardia, six were treated prenatally, one was delivered prematurely. Correct identification of an arrhythmia and appropriate prenatal therapy where indicated, was found to prevent unnecessary operative or premature deliveries.

[Fetal heart. Present investigative means]

Non invasive exploration of the fetal heart has been greatly facilitated by utilisation of high resolution echography using pulsed Doppler combined with B-scan. Investigation of the fetal heart in human medicine opens three important fields of interest. Better knowledge of fetal hemodynamics. Measurement of fetal heart function. Recognition of congenital heart disease. Acquisition of some fundamental knowledge is required for an ultrasonic approach to fetal echocardiography. Embryogenetic data lead to an understanding of the periods of vulnerability for each cardiac segment, whereas an understanding of physiology of the fetal circulation helps to explain the consequences of fetal congenital heart diseases and the methods used to evaluate fetal cardiac function. One section is devoted to the etiology of congenital heart disease. The most important cardiopathies encountered in cases of chromosomal anomalies and genetic disease as well as those due to environmental causes are presented so that the echographist may relate the examination to the clinical picture. In most instances the diagnosis of congenital heart disease is made by routine morphologic scanning of the fetal heart. Indications are given for the best orientation of the scans. All echographists should have precise knowledge of the echographic semeiology of the normal heart. When a cardiopathy or an anomaly of cardiac rhythm are recognized or suspected, the examination should be repeated with help of a cardiopediatrician so as to make an exact diagnosis and take the right decision. Study of fetal heart function is the most recent field for progress and covers in addition to the evaluation of congenital heart disease the development of new parameters allowing recognition of fetal jeopardy. Pulsed Doppler has already allowed the acquisition of interesting facts and certainly is one of the most exciting new inroads for progress in the field of fetal cardiology.

Evaluation of fetal arrhythmias by echocardiography

The normal fetal heart shows variation in rate and rhythm. Twenty three cases that fell outside the normal patterns of variation of heart rate and rhythm were evaluated by echocardiography. Ten showed atrial or ventricular extrasystoles and these were not associated with perinatal morbidity or mortality. Seven cases showed complete heart block, two in association with structural cardiac abnormality. Six cases were of supraventricular tachycardia, five of which were successfully treated and one was delivered prematurely. It was possible to diagnose accurately the type of arrhythmia using the M-mode echocardiogram to compare the relation between atrial and ventricular contraction. Cross-sectional echocardiography allowed identification of associated structural abnormalities. Recognition that an arrhythmia is present and appropriate prenatal treatment if this is indicated will avoid unnecessary operative or premature deliveries.

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

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

A contribution to the monitoring of fetal arrhythmias

Antepartum and intrapartum monitoring problems are discussed with reference to a case history of a fetal AV-block detected during the 36th week of pregnancy. CTG instruments where the internal logic criteria can be turned off are suitable for monitoring arrhythmias. During labor the direct fetal ECG permits exact diagnosis as to the type of arrhythmia. The necessity of antepartum diagnosis in regard to postpartum pediatric management and hypoxic states during labor justify the large expenditure on monitoring apparatus. During labor continuous tissue pH measurement via the fetal scalp give added information as to fetal condition.

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

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

Intrauterine fetal arrhythmia: atrial premature beats

A case of antepartum fetal arrhythmia is reported. The diagnosis of atrial premature beats was confirmed during labor by simultaneous recording of fetal heart rate and fetal electrocardiogram. The possibility of fetal distress during labor was excluded by fetal heart rate and acid-base monitoring. The difficulty of reaching a definitive antepartum diagnosis of the arrhythmia and its significance in relation to fetal well-being are discussed.