Human Fetal Heart Research Articles

Cocaine‐Induced Arrhythmia in Human Foetal Myocardium in Vitro: Possible Mechanism for Foetal Death in Utero

We examined the acute in vitro effects of cocaine on cell membrane potentials and contractility of 12-16 week old human foetal heart, to better assess the potential for the induction of serious arrhythmia, in utero, by this abused substance. Ventricular preparations were maintained in a tissue bath, and continuously provided with oxygen and glucose during the measurement of membrane potentials with microelectrodes, and developed force of contractions with microforce transducers. Cocaine (600 ng/ml) had a significant effect on the ability of the heart to produce action potentials of normal rising velocity, amplitude, and duration. Within 90 min., all electromechanical activity had ceased. Under the conditions of our study, the effects of cocaine were reversible, however, reversibility in vitro may have no counterpart in utero, and irreversible loss of cardiac function may result.

The myosin gene switching in human cardiac hypertrophy.

Cardiac hypertrophy is associated with qualitative as well as quantitative changes in myocardial cells. To analyze the molecular basis of isozymic transitions of cardiac myosins in response to pressure overload, we have constructed and characterized two types of myosin heavy chain (MHC) cDNA clones, specifying alpha- and beta-MHCs, and two types of myosin alkali light chain cDNA clones, complementary to atrial type (ALC1) and ventricular type (VLC1) mRNAs from a human fetal heart cDNA library. Using the S1 nuclease mapping procedure, we showed that the MCH isozymic transitions from alpha- to beta-MHC in the pressure overloaded atria are produced by changes in the relative level of alpha- and beta-MHC gene expression. In addition, we observed that the expression of VLC1 gene is also induced in the atria subjected to severe pressure overload. Thus, it appears that the increased expression of VLC1 gene, together with the isogene switch from alpha- to beta-MHC gene, may participate in the adaptation of myocardium to new functional requirement. Then, to get a better understanding of the genetic mechanisms involved in the regulation of isogene expression, we have isolated and sequenced genomic clone for VLC1 isoform. Sequence analysis has identified multiple potential cis regulatory elements within a 686-bp upstream region. This region includes 28-bp alternating purine/pyrimidine sequences and two segment exhibiting homology to consensus sequence proposed for viral and cellular enhancer elements. In particular, a comparison of the VLC1 upstream gene sequence with those available for several muscle-specific genes revealed that CC(A + T-rich)6GG elements and CATTCCT sequence are conserved. These results suggested that CArG box (-96 to -87) has an important role in the positive regulation of the VLC1 gene and this element may be involved in the co-regulation of VLC1 and cardiac alpha-actin genes.

Morphometric Study on the Development of the Human Fetal Heart after Mid-term

Morphometric Study on the Development of the Human Fetal Heart after Mid-term

Culture and characterization of fetal human atrial and ventricular cardiac muscle cells

Atrial and ventricular cardiac muscle cells isolated from 14- to 18-wk old fetal human hearts were grown in culture and characterized. Once established in culture the flattened cells contracted spontaneously and possessed differentiated ultrastructural characteristics including organized sarcomeres, intercalated discs, and transverse tubules with couplings. Atrial granules were present in the cultured atrial cells. Some cultured ventricular myocytes also contained electron-dense granules associated with Golgi cisternae, which were similar in size and appearance to atrial granules. The cultured ventricular myocytes divided and expressed the genes for thymidine kinase, histone H4, myosin heavy chain, muscle-specific creatine kinase, atrial natriuretic factor, and insulin-like growth factor II. These results establish that differentiated fetal human heart muscle cells can be cultured in sufficient quantities for biochemical, molecular, and morphological analyses.

Atrial natriuretic peptide in the ventricles of patients with dilated cardiomyopathy and human foetuses

Immunohistochemical examination of atrial natriuretic peptide (ANP) was performed on endomyocardial biopsy specimens from 8 patients with dilated cardiomyopathy (DCM), 10 human foetal hearts obtained from legal abortions, and 8 adult hearts from autopsy control subjects without cardiovascular diseases. The indirect immunoperoxidase method, using specific monoclonal antibody to alpha-human ANP was employed. Immunoreactivity was observed at the light microscope level in the working ventricular cardiocytes of all patients with DCM as dark-brown, granular deposits. Peripheral plasma levels of ANP in these patients were also increased. In control adult hearts without cardiovascular diseases, immunoreactivity was detected both in the atria and in the ventricular impulse-conducting system, although the working ventricular cardiocytes were not immunoreactive. In foetal hearts, immunoreactivity was detected not only in the atria and ventricular impulse-conducting system, but also in the working ventricular cardiocytes. We conclude that ANP is present in the ventricular impulse-conducting system of the human hearts, and that ANP is also present in the working ventricular cardiocytes in patients with DCM as well as in human foetuses.

A moderate concentration of ethanol alters cellular membrane potentials and decreases contractile force of human fetal heart.

The effects of ethanol, although well studied in the adult myocardium, have been little studied in fetal tissue. Experiments in pregnant animals suggest that ethanol compromises fetal myocardial performance, in utero; however, the physiological mechanism(s) remains obscure. The present report examines, in vitro, the effects of a moderate concentration of ethanol (20 mM) directly on cell membrane potentials and contractility of human fetal left ventricle as determined using intracellular microelectrodes and microforce transducers. We observed significant decreases in action potential amplitude, upstroke velocity, duration of repolarization, and the force of contractions. These effects were reversible. As ethanol crosses the placenta, our findings suggest that moderate concentrations of ethanol, as occur during 'social drinking', may temporarily compromise fetal myocardial performance in utero.

Isolation and culture of beating cells from human fetal heart

A method is described for culture of myocardial cells from cardiac tissue of 8 to 12 wk-old human fetuses. Modification of the existing procedures for cell isolation and growth has helped to improve the yield of viable cells. Cultured myocardial cells can be used for experimental studies.

Localisation of atrial natriuretic peptide immunoreactivity in the ventricular myocardium and conduction system of the human fetal and adult heart.

Atrial natriuretic peptide immunoreactivity was found in ventricular and atrial tissues with specific antisera raised to the amino and carboxy terminal regions of the precursor molecule. In 13 developing human hearts (7-24 weeks' gestation) the immunoreactivity was concentrated in the atrial myocardium and ventricular conduction system but it was also detected in the early fetal ventricular myocardium. Immunoreactivity in five normal adults was largely confined to the atrial myocardium although it was also found in the ventricular conduction tissues of hearts removed from 10 patients who were undergoing cardiac transplantation. The ventricular conduction system is an extra-atrial site for the synthesis of atrial natriuretic peptide. In the failing heart this synthesis may be further supplemented by expression of the gene in the ventricular myocardium. It is possible that ventricular production of the peptide contributes to the raised circulating concentrations of atrial natriuretic peptide immunoreactivity found in severe congestive heart disease, particularly in patients with dilated cardiomyopathy.

Molecular cloning and characterization of human atrial and ventricular myosin alkali light chain cDNA clones.

We have isolated essentially full-length cDNA clones for atrial (ALC1) and ventricular (VLC1) myosin alkali light chains from a human fetal heart cDNA library. Comparison of overall nucleotide sequences of ALC1 and VLC1 cDNA clones has revealed that, while these two inserts show significant DNA sequence homology (78.4%) with respect to their coding regions, the 5'- and 3'-untranslated regions are highly divergent. Our statistical analysis suggests that human ALC1 and VLC1 diverged approximately 300 million years ago, during the time of separation of birds and mammals. RNA blot analysis shows that ALC1 mRNA is expressed in fetal ventricular and fetal skeletal muscles as well as fetal and adult atrial muscles and VLC1 mRNA is expressed in adult slow skeletal muscle as well as fetal and adult ventricular muscles. Southern blot analysis indicates that each protein is encoded by a single gene. Finally, we show that VLC1 mRNA is induced in pressure-overloaded human atrium.

Acute Effects of Maternal Smoking on Human Fetal Heart Function

M-mode echocardiography was used to evaluate fetal heart function following maternal smoking in 21 healthy smoking pregnant women between 24 and 39 weeks of uneventful gestation. Prior to smoking one cigarette (nicotine content 1.7 mg), a fetal M-mode echocardiographic examination was performed and repeated 5 and 10 min after maternal smoking. Maternal heart rate and systolic blood pressure increased 8.7% and 15.0%, respectively, immediately after smoking, while diastolic blood pressure remained unchanged. Fetal heart rate increased 4.3% and left ventricular diastolic and systolic diameters decreased 4.5% and 15.0%, respectively. No changes in right ventricular dimensions, ventricular ejection times, ventricular wall thickness or septal thickness were observed. Fractional shortening, mean velocity of fractional shortening, stroke volume and cardiac output of the left ventricle also remained unchanged subsequent to smoking. Thus, maternal smoking of one cigarette seems to elicit only a transitory acceleration in fetal heart rate without concomitant significant changes in fetal heart function.

Fetal Cardiac Function in Response to Long‐Term Maternal Terbutalin Treatment

To evaluate whether long-term human fetal exposure to beta 2-adrenergic receptor agonists elicit alterations in the human fetal heart, a fetal echocardiographic examination was performed in 9 fetuses between the 24th and 35th week of gestation (median 28 weeks) and 9 age-matched controls. Examinations were performed during long-term tocolytic terbutalin treatment. Drug dosages varied between 7.5 and 20.0 mg/day (median 10.0 mg/day) and treatment durations prior to examination varied between 14 and 60 days (median 25 days). No significant differences were noted between the exposed fetuses and their controls as regards FHR, left ventricular dimensions, interventricular septal thickness, left ventricular contractility (fractional shortening) and the derived left ventricular stroke volume. Despite the limited number of subjects it is believed that long-term terbutalin exposure does not have any untoward major fetal left ventricular consequences.

A mathematical model for analyzing beat-to-beat difference in the human fetal heart rate during gestation and labor

We devised a model suitable for mathematical analysis of beat-to-beat differences (BBDs) in fetal heart rates (FHRs). Factor analysis was applied, using a computer system, on a specially devised model of an FHR matrix. This matrix was arranged with FHRs and BBDs at 1-beat/min intervals by rows and columns, respectively. After obtaining the BBD by subtracting the antecedent FHR from the following FHR in a given pair of two consecutive FHRs, both variables of the antecedent FHR and BBD were crossed and the number of one was recorded at the corresponding element of the matrix. This procedure was done for all pairs of FHR and BBD yielding a matrix containing the cumulative incidences. Investigated was a total of 225,282 FHRs obtained from 20 fetuses between 37 and 41 weeks of gestation, by means of a scalp-lead electrocardiograph taken during labor. As shown by clusters of BBDs in units of beats/min, three different factors become evident: fluctuation around zero bpm, plus deviations and minus deviations. The first is considered to play a role in maintaining so-called baseline FHRs, and the second aand the third indicate accelerating and decelerating actions on FHRs, respectively. This analytical model is discussed with reference to the findings obtained.

Fetal and neonatal cardiac assessment with Doppler.

During recent years, Doppler ultrasound has become an instrument with which the fetal and neonatal cardiovascular system can be examined noninvasively. In fetuses with suspected cardiac anomalies, Doppler examinations can be used to complement two-dimensional and M-mode studies. Information derived from human fetal intracardiac studies has established that the human fetal heart is right-heart dominant, less compliant than the adult heart, and changes with advancing gestation. Much work remains to be performed to use this information to better manage ongoing pregnancies, and to optimize transition to neonatal life.

Patterns of human fetal heart rate accelerations from 26 weeks to term

Computerized analysis of the distribution of 2598 fetal heart rate accelerations in 83 healthy fetuses at 26 to 40 weeks' gestation demonstrated that the currently used definition of an acceleration as greater than or equal to 15 beats/min for greater than or equal to 15 seconds is applicable only after 30 weeks' gestational age in fetuses with a basal fetal heart rate of less than or equal to 128 beats/min. A significant negative correlation was found between the mean hourly basal fetal heart rate and the mean amplitude of fetal heart rate accelerations from 30 weeks to term. There was also a significant maturational process in the pattern of fetal heart rate and fetal heart rate accelerations that occurred between 26 and 28 and between 30 and 32 weeks; this was characterized by a decrease in basal fetal heart rate, an increase in the amplitude of fetal heart rate accelerations, and an increase in long-term fetal heart rate variability.

Atrial and ventricular myosins from human hearts. I. Isoenzyme distribution during development and in the adult

Two distinct types of native isomyosins, referred to as human fetal HF and human ventricular myosin HV-3, have been identified in the human fetal heart during two different periods of gestation and in the neonatal state, whose relative parts change with development. In the adult ventricle, only HV-3 was found. Two myosin isoforms designated as HA-3 and HA-1 occur in the atrial myocardium of the normal human heart, which are electrophoretically distinct from the fetal isoenzymes. In fetal tissue, the myosin light chain complement is composed of atrial and ventricular light chains. In support of recent results, we also found identical spots from the atrial ALC-1 and the fetal light chain FLC, suggesting a homology between them. Apart from the light chains typical for this tissue, the atrial myocardium also contains ventricular light chains. Therefore we hypothesize that atrial myosin consists of two atrial isoenzymes and presumably of a ventricular type, too. Differences between atrial and ventricular myosin from human hearts were demonstrated by measuring the temperature dependence of the Ca2+-ATPase.

Effects of heart rate on ventricular size, stroke volume, and output in the normal human fetus: a prospective Doppler echocardiographic study.

The effect of heart rate on cardiac output in the fetal heart is controversial. We used Doppler echocardiography to investigate the effects of increasing heart rate on stroke volume and ventricular output in the normal human fetal heart. Heart rate was increased in 25 human fetuses (mean age 36 weeks) by auditory stimulation with a sound emitter placed on the mother's abdomen. Aortic or pulmonary diameters were measured at valve level from two-dimensional echocardiographic images and cross-sectional areas were calculated. Blood flow velocity spectra from the pulmonary artery or aorta were digitized to obtain flow velocity integrals before and after auditory stimulation. Stroke volume was calculated as the product of the flow velocity integral and the area of the great vessel. Prestimulation mean heart rate was 132 +/- 8 beats/min and increased after auditory stimulation to 158 +/- 9 beats/min (p less than .001). Stroke volume decreased with the increase in heart rate from 3.7 +/- 1.4 ml before stimulation to 3.0 +/- 1.1 ml after stimulation (p less than .001), but ventricular output calculated as the product of stroke volume and heart rate remained unchanged (0.48 +/- 0.18 liter/min before vs 0.48 +/- 0.17 liter/min after stimulation). The decrease in stroke volume was accompanied by a decrease in ventricular end-diastolic area, although there was no change either in end-systolic area or fractional change in area. This study demonstrates that increases in heart rate within the physiologic range in the normal human fetus result in a decrease in ventricular size and stroke volume but no change in ventricular output or ventricular shortening.

Doppler echocardiographic evaluation of the normal human fetal heart.

Pulsed wave Doppler estimates of blood flow velocity were made across the mitral, tricuspid, aortic, and pulmonary valves in a series of 120 normal fetuses (gestational age 16-36 weeks). In 36 of these the data were obtained in all four sites. The maximum and mean velocities were calculated for each valve and these values were plotted against gestational age. There was little change in these values throughout pregnancy. The orifice dimensions of the valves were measured by cross sectional echocardiography. At all ages the tricuspid orifice was larger than the mitral and the pulmonary orifice was larger than the aortic. The blood flow values for each valve were derived from the product of the mean velocity and the valve orifice dimensions. The output of the right ventricle was usually, but not always, greater than that of the left ventricle. Combined ventricular output increased from approximately 50 ml/min at 18 weeks to 1200 ml/min at term. Despite limitations in the accuracy of the technique these results form a useful basis for the analysis of blood flow in the normal fetus and for the interpretation of abnormal Doppler findings in prenatal life.

Echocardiographic and pathoanatomic assessment of growth, function and chamber volumes of the normal human fetal heart.

AbstractTo assess the growth pattern, relative left ventricular (LV) and right ventricular (RV) sizes, function and volumes, 168 echocardiograms and 14 postmortem hearts of normal human fetuses were studied. LV and RV diameters, atrioventricular valve diameters, wall thicknesses and aortic diameter increased linearly with gestational age from 20 to 39 weeks, but percent changes in ventricular diameters and wall thickness were constant and similar between LV and RV in echocardiograms. The ratios of LV and RV diameters, wall thicknesses and mitral and tricuspid valve diameters were constant and were approximately 1.0 throughout the period studied in echocardiograms and postmortem hearts. LV and RV volumes in postmortem hearts were also similar. LV volumes of postmortem hearts were best approximately by an ellipsoid model, and clinical application of this model to echocardiograms showed a linear increase of LV volume with age and constant ejection fraction and LV output per body weight. These results suggest a linear growth pattern and constant systolic function of the fetal heart, and do not support the concept of RV dominance.

Acute effects of maternal smoking on human fetal heart function.

M-mode echocardiography was used to evaluate fetal heart function following maternal smoking in 21 healthy smoking pregnant women between 24 and 39 weeks of uneventful gestation. Prior to smoking one cigarette (nicotine content 1.7 mg), a fetal M-mode echocardiographic examination was performed and repeated 5 and 10 min after maternal smoking. Maternal heart rate and systolic blood pressure increased 8.7% and 15.0%, respectively, immediately after smoking, while diastolic blood pressure remained unchanged. Fetal heart rate increased 4.3% and left ventricular diastolic and systolic diameters decreased 4.5% and 15.0%, respectively. No changes in right ventricular dimensions, ventricular ejection times, ventricular wall thickness or septal thickness were observed. Fractional shortening, mean velocity of fractional shortening, stroke volume and cardiac output of the left ventricle also remained unchanged subsequent to smoking. Thus, maternal smoking of one cigarette seems to elicit only a transitory acceleration in fetal heart rate without concomitant significant changes in fetal heart function.

Growth and function of human fetal heart in normal, hypertensive and diabetic pregnancy.

Fetal cardiac left and right ventricular dimensions and contractility were measured by echocardiography in late pregnancy in 51 normal, 26 hypertensive and 18 diabetic pregnancies. In relationship with the fetal size, both of the ventricular dimensions, the contractility and left ventricular output were decreased in diabetic cases. In hypertensive pregnancy the relative size of the right ventricle was increased and its contractility decreased, but the function of the left ventricle was no different from normal. These findings may reflect biochemical changes in diabetic myocardium and increased peripheral fetal and placental resistance in hypertensive pregnancy.