Fetal magnetocardiography

The electrical activities of the heart causes weak changes of the magnetic field, which can be recorded as magnetocardiogram (MCG). Fetal cardiac magnetic activity is measured in the order of less than 10 pT. An advance of the novel technology of a superconducting quantum interference device enabled the first recording of fetal MCG (FMCG) in 1974. In Japan, FMCG instrument (MC6400, Hitachi High-Technologies Ltd) was approved as a diagnostic tool by Japanese Government in 2003 owing to the cooperative studies of Tsukuba University, National Cardiovascular Center and Hitachi Ltd. FMCG offers similar information to a fetal electrocardiogram, which is difficult to be recorded because the fetal skin is covered with fatty caseous vernix of weak electrical conductivity in the second and third trimester of pregnancy. Magnetic flux can pass through the fat layer, and thus FMCG can measure the electrical activity of the fetal heart. Besides FMCG has far higher resolutions in time domain than echocardiography does. The amplitude of FMCG signals depends on the size of fetal heart and the distance between the sensors and the fetal heart. The amplitudes of the QRS, P and T waves increases with gestational age. Since the amplitudes of P and T waves are often weak, averaging of FMCG signals is needed to improve the signal-to-noise ratio. Current-arrow map is a useful mapping technique even in FMCG. FMCG has been applied in the prenatal diagnosis of fetal arrhythmias such as bradyarrhythmia (atrioventricular block, long QT syndrome, etc), tachyarrhythmia (supraventricular tachycardia, atrial flutter, atrial fibrillation and WPW syndrome, etc) and extrasystoles. Fetal cardiomegaly with myocardial abnormalities can be also diagnosed by FMCG. Applications of FMCG for fetal heart rate monitoring using beat-to-beat variability have been also studied to obtain better information on fetal well-beings.     

Detection of atrial-flutter and atrial-fibrillation waveforms by fetal magnetocardiogram

Two cases of fetal tachycardia are reported: atrial flutter and fibrillation. The waveforms from each case were detected by fetal magnetocardiograms (FMCGs) using a 64-channel superconducting quantum interference device (SQUID) system. Because the magnitude of supraventricular arrhythmia signals is very weak, two subtraction methods were used to detect the fetal MCG waveforms: subtraction of the maternal MCG signal, and subtraction of the fetal QRS complex signal. It was found that atrial-flutter waveforms showed a cyclic pattern and that atrial-fibrillation waveforms showed f-waves with a random atrial rhythm. Fast Fourier transform analysis determined the main frequency of the atrial flutter to be about 7 Hz, and the frequency distribution of atrial fibrillation consisted of small, broad peaks. To visualise the current pattern, current-arrow maps, which simplify the observation of pseudo-current patterns in fetal hearts, of the averaged atrial flutter and fibrillation waveforms were produced. The map of the atrial flutter had a circular pattern, indicating a re-entry circuit, and the map of the atrial fibrillation indicated one wavelet, which was produced by a micro-re-entry circuit. It is thus concluded that an FMCG can detect supraventricular arrhythmia, which can be characterised by re-entry circuits, in fetuses.     

The event synchronous canceller algorithm removes maternal ECG from abdominal signals without affecting the fetal ECG

Fetal monitoring using abdominally recorded signals (ADS) allows physicians to detect occurring changes in the well-being state of the fetus from the beginning of pregnancy. Mainly based on the fetal electrocardiogram (fECG), it provides the long-term fetal heart rate (fHR) and assessment of the fetal QRS morphology. But the fECG component in ADS is obscured by the maternal ECG (mECG), thus removal of the mECG from ADS improves fECG analysis. This study demonstrates the performance of the event-synchronous interference canceller (ESC) in mECG removal from ADS data, recorded during pregnancy and labor. Its advantage as a compensation method for extended ADS processing is discussed.     

The influence of coincidence of fetal and maternal QRS complexes on fetal heart rate reliability

Bioelectrical fetal heart activity being recorded from maternal abdominal surface contains more information than mechanical heart activity measurement based on the Doppler ultrasound signals. However, it requires extraction of fetal electrocardiogram from abdominal signals where the maternal electrocardiogram is dominant. The simplest technique for maternal component suppression is a blanking procedure, which relies upon the replacement of maternal QRS complexes by isoline values. Although, in case of coincidence of fetal and maternal QRS complexes, it causes a loss of information on fetal heart activity. Its influence on determination of fetal heart rate and the variability analysis depends on the sensitivity of the heart-beat detector used. The sensitivity is defined as an ability to detect the incomplete fetal QRS complex. The aim of this work was to evaluate the influence of the maternal electrocardiogram suppression method used on the reliability of FHR signal being calculated.     

Women with bleeding in the first 20 weeks of pregnancy: value of general practice ultrasound in detecting fetal heart movement.

BACKGROUND: Real-time ultrasound scanning has made it possible to ascertain whether the fetus is alive in women who have bleeding in early pregnancy. Portable ultrasound machines are capable of detecting fetal heart movement reliably after the ninth week of pregnancy, and can be used in a general practice setting. An ultrasound clinic was set up in a health centre and 22 general practitioners in the local area could refer women patients with bleeding in early pregnancy. AIM: A study was carried out among women with bleeding in early pregnancy to compare the presence of fetal heart movement detected at the initial ultrasound scan with subsequent fetal survival during the first 20 weeks of pregnancy. METHOD: Data were collected during a three-year period on women referred opportunistically by their general practitioners. An abdominal scan was performed on the same day or the day after presentation and the presence or absence of fetal heart movement recorded. Diagnoses and outcome at 20 weeks were ascertained from patients' health centre records. RESULTS: A total of 240 women with bleeding in early pregnancy were scanned and at the first examination fetal heart movement was detected in 115 of the fetuses (48%). Three fetuses were subsequently miscarried spontaneously while 109 of the 115 continued to the 20th week (95%). Three fetuses had gross abnormalities and these pregnancies were subsequently terminated. No heart movement was detected in 117 fetuses (49%); all were subsequently miscarried. For eight women scanned it was not clear whether fetal heart movement was present. Three of these eight pregnancies survived to the 20th week. Predictive values of fetal survival to the 20th week of pregnancy from fetal heart movement detected by general practice ultrasound scan for women with bleeding in early pregnancy showed a sensitivity of 97% and a specificity of 98%. CONCLUSION: If fetal heart movement is detected at the initial scan, approximately 19 out of every 20 viable pregnancies (those in which the fetus appears normal) will not miscarry before the 20th week. Using ultrasound in general practice it was possible to identify promptly those women with bleeding whose fetus was alive. For those women found to have a non-viable pregnancy, appropriate arrangements could be made at an early stage in the knowledge that a miscarriage was inevitable, thus avoiding unnecessary bed rest for the patient. Where fetal heart movement was detected, there was a good prognosis and thus women could be given strong reassurance.     

A method for the automatic reconstruction of fetal cardiac signals from magnetocardiographic recordings

Fetal magnetocardiography (fMCG) allows monitoring the fetal heart function through algorithms able to retrieve the fetal cardiac signal, but no standardized automatic model has become available so far. In this paper, we describe an automatic method that restores the fetal cardiac trace from fMCG recordings by means of a weighted summation of fetal components separated with independent component analysis (ICA) and identified through dedicated algorithms that analyse the frequency content and temporal structure of each source signal. Multichannel fMCG datasets of 66 healthy and 4 arrhythmic fetuses were used to validate the automatic method with respect to a classical procedure requiring the manual classification of fetal components by an expert investigator. ICA was run with input clusters of different dimensions to simulate various MCG systems. Detection rates, true negative and false positive component categorization, QRS amplitude, standard deviation and signal-to-noise ratio of reconstructed fetal signals, and real and per cent QRS differences between paired fetal traces retrieved automatically and manually were calculated to quantify the performances of the automatic method. Its robustness and reliability, particularly evident with the use of large input clusters, might increase the diagnostic role of fMCG during the prenatal period.     

Real-time multichannel abdominal fetal ECG monitor using Digital Signal CoProcessor

A real-time multichannel fetal ECG monitor based on a personal computer (PC) and a MOTOROLA DSP56001 Digital Signal CoProcessor (DSP) is introduced. The DSP board is plugged into the PC, which functions as a HOST computer. An analog 8 Leads Interface and Analog to Digital circuits module is connected to the DSP through a synchronous, opticalisolated communication channel.

The fetal ECG detection is based on a cross-correlation technique. An averaged maternal ECG waveform is generated using a cross-correlation alignment procedure and a user-defined template. The fetal ECG signals present in the maternal waveform is suppressed during the averaging procedure, since both are uncorrelated. The average maternal ECG waveform is then subtracted from the abdominal real time signals, and maternal-free fetal ECGs signals are obtained, including fetal QRS complexes that coincide with maternal ones. Using the abdominal ECGs signals after subtraction, an averaged fetal waveform is generated. The maternal and the fetal heart rate are calculated during the process.

The algorithm described above can be performed in real time on up to eight abdominal ECG traces by the DSP, and the desired results are passed to the HOST PC, to be stored and displayed. Electrodes positioning procedures for detecting the fetal QRS complexes with the best signal to noise ratio are not needed. Using the multichannel system, the user can select the best channel for fetal QRS detection, and accurate results for the heart rate signal are obtained. Averaged fetal waveforms are obtained from all the leads.     

Impact of maternal supine position on some parameters of fetal function in rabbits

Fixation of a pregnant rabbit in the supine position is shown to result in hemodynamic disturbances in the maternal-placental-fetal system, apparently due to a hypotensive syndrome developing in the mother. The heart rate, body temperature, and motor activity in the fetuses of such mothers were similar to those recorded for fetuses with retarded development. It is concluded that maternal position needs to be taken into consideration in experiments designed to examine interrelated responses of mother and fetus to external stimuli. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 121, N ^o 1, pp. 33–35, January, 1996 Presented by B. I. Tkachenko, Member of the Russian Academy of Medical Sciences     

Maternal stress responses and anxiety during pregnancy: effects on fetal heart rate

This study examined the effect of an acute maternal stress response and anxiety on fetal heart rate. Seventeen healthy, 3rd-trimester pregnant women (mean age = 26 +/- 6 years) were instrumented for continuous electrocardiography, blood pressure (BP), respiration, and fetal heart rate (HR). Subjects completed the state anxiety subscale of the State Trait Personality Inventory (STPI), then rested quietly in a semirecumbent position for a 5-min baseline period, followed by either a 5-min arithmetic or Stroop color-word task. Over the entire 5-min stress period and when averaged across all subjects, the stressors led to significant increases in maternal systolic BP and respiratory rate but changes in maternal HR, diastolic BP, and fetal HR were not significant. However, when subjects were dichotomized into groups that had above or below average anxiety scores [ANX(+) and ANX(-)], both groups had similar respiration rate increases to the stressors, but the BP and fetal heart rate (FHR) responses were significantly different. Women in the ANX(-) group had significantly greater BP responses compared to women in the ANX(+) group whereas the fetuses of ANX(+) women showed significant HR increases and the fetuses of ANX(-) women exhibited nonsignificant decreases. These findings suggest that women's acute emotional reactivity during pregnancy can influence fetal HR patterns and that a stress-induced increase in maternal BP is not the primary signal by which a women's stress response is transduced to her fetus. The results are consistent with the hypothesis that maternal psychological variables may shape the neurobehavioral development of the fetus.     

Development of autonomic control of fetal circulation.

Development of parasympathetic and sympathetic reflexes controlling heart rate, vascular pressures, and blood flows was investigated in fetal lambs weighing 300-5,800 g (65-165 days' gestation). Cardiovascular responses to veratridine injections, atrial stretching, bilateral cervical vagotomy, and cholinergic blockade with atropine were used to test parasympathetic activities. Responses to propranolol and phenoxybenzamine were used to test beta- and alpha-adrenergic activities. Autonomic ganglionic blockade and stimulation provided additional information on both cholinergic and adrenergic systems. Fetal responses to various tests were compared to those of the mother. Results show: a) little parasympathetic tone on resting heart rate and other circulatory functions exists prior to fetal maturity; b) despite the feeble resting tone, the parasympathetic system is capable of exerting significant control when stimulated in both premature and mature fetuses, the capability increases as fetus approaches term; c) alpha- and beta-adrenergic tone in control of resting heart rate and peripheral circulation exists in early fetal life and increases as the fetus reaches maturity, and both adrenergic receptors respond strongly to stimuli in immature, premature, and mature fetuses; d) in immature fetuses, veratridine does not elicit a vagally mediated reflex; instead, it produces a centrally mediated alpha- and beta-adrenergic stimulation; e) the fetal cardiovascular response to any given test is dampened by the existence of the various vascular shunts, the umbilicoplacental circulation and, possibly, by incomplete maturation of vasomotor tone.     

A new animal model for fetal macrosomia in diabetic pregnancy

Fetal macrosomia in human diabetic pregnancy has long been recognized. However, an animal model suitable for studying fetal macrosomia and other fetal anomalies in diabetic pregnancy has been lacking. In the present study the visually recognizable macrosomic fetus was compared with its normal weight litter mates obtained on the 19.5 day of gestation from mildly diabetic Sprague-Dawley rats. The mean body weights of macrosomic fetuses and the normal litter mates were 4.72 ± 0.45 g (mean ± SE) and 2.76 ± 0.18 g, respectively. The rate of [³H]AIB influx from the maternal to fetal side for the macrosomic fetuses was approximately 50 times greater than the corresponding rate for the normal litter mates. The visual identification of macrosomia is thus verified by two different parameters (e.g., body weight and rate of metabolite influx). These results provide a rationale for comparing macrosomic fetuses with their litter mates for studying pathogenesis of macrosomia in diabetic pregnancies in an animal system. This model mimics the human fetal macrosomia more closely than those reported heretofore.     

Duplication of 20p12.3 associated with familial Wolff–Parkinson–White syndrome

Wolff–Parkinson–White (WPW) syndrome is caused by preexcitation of the ventricular myocardium via an accessory pathway which increases the risk for paroxysmal supraventricular tachycardia. The condition is often sporadic and of unknown etiology in the majority of cases. Autosomal dominant inheritance and association with congenital heart defects or ventricular hypertrophy were described. Microdeletions of 20p12.3 have been associated with WPW syndrome with either cognitive dysfunction or Alagille syndrome. Here, we describe the association of 20p12.3 duplication with WPW syndrome in a patient who presented with non‐immune hydrops. Her paternal uncle carries the duplication and has attention‐deficit hyperactivity disorder and electrocardiographic findings consistent with WPW. The 769 kb duplication was detected by the Affymetrix Whole Genome‐Human SNP Array 6.0 and encompasses two genes and the first two exons of a third gene. We discuss the potential role of the genes in the duplicated region in the pathogenesis of WPW and possible neurobehavioral abnormalities. Our data provide additional support for a significant role of 20p12.3 chromosomal rearrangements in the etiology of WPW syndrome. © 2012 Wiley Periodicals, Inc.     

Enhanced placental cholesterol efflux by fetal HDL in Smith-Lemli-Opitz syndrome

Previous studies from this laboratory have shown that maternal-derived cholesterol can be effluxed from trophoblasts to fetal HDL and plasma. We had the opportunity to study for the first time the ability of HDL and plasma from a fetus with the Smith-Lemli-Opitz syndrome (SLOS) to efflux cholesterol from trophoblasts. It was unclear whether cholesterol could be effluxed to fetuses with SLOS since lipoprotein levels are often very low. To answer this question, cord blood was collected from the placentas of an SLOS fetus and unaffected fetuses just after delivery. Plasma cholesterol concentrations were very low in the affected fetus; cholesterol, 7-dehydrocholesterol, and 8-dehydocholesterol concentrations were 14.1, 4.5, and 5.2 mg/dl, respectively. The HDL from the fetal SLOS effluxed approximately 50% more cholesterol from a trophoblast cell line, were smaller in size, and had a lower cholesterol to phospholipid ratio as compared to HDL from unaffected fetuses or adults. Plasma from the SLOS fetus effluxed cholesterol to a similar percentage as unaffected fetal plasma or adult plasma, possibly due to fewer HDL particles as demonstrated in previous SLOS patients. These novel data demonstrate that the cholesterol-deficient SLOS fetus is able to obtain cholesterol from trophoblasts at a time when cholesterol is playing a critical role in development, and has implications for design of treatments for cholesterol deficiency syndromes as well as understanding of prenatal cholesterol transport in humans.     

The effect of chronic hyperinsulinemia on ovine fetal growth

Infusion of exogenous insulin for 18 days to seven ovine twin fetuses caused hyperinsulinemia (31.0 +/- 6.9 microU/ml) when each was compared to its sham-infused twin (6.6 +/- 0.7 microU/ml). The hyperinsulinemic fetuses also had lower arterial serum glucose concentrations (0.77 +/- 0.07 mM) than their sham-infused controls (1.10 +/- 0.04 mM). There were no significant changes in fetal weight or height attributable to insulin infusion. Our methods would have detected a 12% difference in fetal weight; therefore, the lack of effect of insulin on fetal weights was not due to excessive variability of the difference in weights between twins. Hyperinsulinemia increased the myocardial cellular contents of protein and RNA, which suggested that myocardial hypertrophy occurred; however, heart weight itself was not significantly increased. This apparent contradiction may be due to considerable variability in heart weight. From the above data, we conclude that 19 days of documented ovine fetal hyperinsulinemia does not increase the growth rate of the nearterm ovine fetus.     

Antepartum non-invasive evaluation of opening and closing timings of the cardiac valves in fetal cardiac cycle

In this study, we propose a non-invasive algorithm to recognize the timings of fetal cardiac events on the basis of analysis of fetal ECG (FECG) and Doppler ultrasound signals. Multiresolution wavelet analysis enabled the frequency contents of the Doppler signals to be linked to the opening (o) and closing (c) of the heart’s valves (Aortic (A) and Mitral (M)). M-mode, B-mode and pulsed Doppler ultrasound were used to verify the timings of opening and closure of these valves. In normal fetuses, the time intervals from Q-wave of QRS complex of FECG to opening and closing of aortic valve, i.e., Q-Ao and Q-Ac were found to be 79.3 ± 17.4 and 224.7 ± 13.3 ms, respectively. For the mitral valve, Q-Mc and Q-Mo were found to be 27.7 ± 9.4 and 294.6 ± 21.3 ms, respectively. Correlations among the timings in opening and closing of cardiac valves were found to be higher in abnormal fetuses than that in normal ones.     

产前超声诊断单脐动脉的临床价值

目的探讨单脐动脉的产前超声诊断及其临床价值。方法对产前超声检查中发现的40例单脐动脉胎儿进一步进行全面筛查,并行脐血染色体检查,对妊娠结局进行随访。结果 40例单脐动脉中,单纯性单脐动脉28例(70%),合并其他畸形12例(30%),其中心血管系统畸形3例,中枢神经系统畸形2例,泌尿系统畸形2例,多发性畸形2例,消化系统畸形、桡骨发育不良及膈疝各1例;接受脐血染色体检查7例,染色体核型异常3例;单纯性单脐动脉预后良好。结论产前超声可以明确诊断单脐动脉。单脐动脉合并其他畸形的发生率高于正常,合并畸形时染色体异常发生率增高。当超声检查发现单脐动脉时,应进一步作系统筛查及染色体检查,并对单脐动脉胎儿生长发育指标进行监测评估,均具有重要的临床意义。     

胎儿心脏畸形孕早期筛查中脐静脉导管血流频谱参数与染色体异常的关系分析

目的探讨胎儿心脏畸形孕早期筛查中脐静脉导管血流频谱参数与染色体异常的关系。方法本研究回顾性分析了2013年1月至2018年5月期间1326例孕11~14w胎儿的临床资料。采用GE E8型彩色多普勒超声诊断仪检查胎儿脐静脉导管血流频谱参数,其中包括心室收缩期波峰(S波)、心室舒张早期波峰(D波)、心房收缩期波峰(a波)、阻力指数(RI)、搏动指数(PI)和S/a比值。结果1326例孕11~14w胎儿中共有1267例为正常胎儿,59例为异常胎儿。随着孕周的升高,胎儿的RI、PI和S/a比值均逐渐降低。43例脐静脉导管异常胎儿中38例为a波反向,5例为a波消失。脐静脉导管异常组的胎儿异常率(18.60%)显著高于正常组(3.98%),差异有统计学意义(P<0.001)。脐静脉导管正常组和异常组的染色体异常具有显著差异(P<0.05)。脐静脉导管血流频谱参数诊断染色体异常的特异度为0.74%,阴性预测值为96.08%。结论在孕11~14w胎儿的早期筛查中,脐静脉导管血流频谱参数异常主要表现为a波反向和消失。脐静脉导管血流频谱参数诊断胎儿染色体异常的特异度和阴性预测值较高,可作为胎儿染色体异常早期筛查的诊断指标。     

Recording and processing of fetal movements and sounds obtained with the Inpho inductive transducer

A recently developed transducer based on an inductive principle allows recording of fetal displacement signals on the maternal abdominal wall. The transducer is a relatively passive device, in contrast to commonly applied ultrasound transducers. This permits long-term observation of fetal movements and sounds. The bandwidth of the system is DC −200 Hz (±3dB), and signal-to-noise ratios of more than 96 dB have been measured in a laboratory setup, whereas in the practical situation a signal-to-noise ratio of 78 dB has been established. The transducer has been applied to study fetal respiratory sinus arrhythmia, which means that fetal breathing movements have to be extracted from the transducer's output. This proved possible by digital filtering of the displacement signal as detected by the transducer. The transducer has also been applied in a study where the signal-to-noise ratio of fetal heart sounds as a function of location of the fetus and position of the transducer on the maternal abdominal wall has been studied. It proved possible to adequately record fetal heart sounds for measurement of fetal heart rate. Also uterine activity could be recorded using the sensor's DC output.     

基于心电图QRS波群的心肌缺血时域分析

目的 ST-T段变化是心电图检测心肌缺血主要的临床表现,代表了心室复极的电位变化;但其特征点定位存在很大的不准确性,为了克服这一难点,本研究从心电图QRS波群出发进行心肌缺血分析.方法 从心电图QRS波群(代表了心室的除极过程)出发,综合提取QRS波群的各个时域参数,然后进行心肌缺血与非心肌缺血条件下的统计检验.结果 ...