Prolonged N200 is the early neurophysiologic change in the patient with minimal hepatic encephalopathy

BACKGROUND

In neurophysiological studies, P300, is well known for reflecting early cognitive impairment in minimal hepatic encephalopathy (MHE). Although P300 is investigated extensively, other early event-related potential (ERP) parameters have not been studied in MHE.

METHODS

The subjects were 21 adult cirrhotic patients without clinical encephalopathy and 29 normal controls. For neuropsychological testing, number connection tests, A and B (NCT-A, NCT-B), the line tracing test, the serial dotting test (SDT), and the digit symbol test (DST) were performed. For ERP testing, auditory oddball paradigms were used. The N100, P200, N200, and P300 parameters were measured.

RESULTS

Cirrhosis had longer neuropsychological performance scores on NCT-A, SDT, and DST than the control group. In neurophysiological test, cirrhotic patients showed longer latencies for N100, P200, N200, and P300 than the control group. Although P300 alteration was not seen in patients without MHE compared to the control group (325.4±43.3 vs. 345.21±35.1, p=0.25), N200 latency was significantly prolonged in cirrhotic patients without MHE compared to the healthy group (242.1±30.3 vs. 259.58±33.3, p=0.006). N200 also showed good correlation with psychometric hepatic encephalopathy score and critical flicker frequency.

CONCLUSIONS

N200 is a useful tool for assessing early changes of cognitive dysfunction in cirrhosis. It suggests that slower auditory cortical processing is the first sign of cerebral deterioration in patients with hepatic encephalopathy.

Neurological and muscular manifestations associated with influenza B infection in children

BACKGROUND

Influenza viruses have been associated with various neurological and muscular symptoms. The aim of this study was to evaluate the pediatric neurological and muscular manifestations of influenza B during a 5-month epidemic at a single center.

METHODS

We retrospectively reviewed the medical records of 355 pediatric patients with laboratory-confirmed influenza B infection.

RESULTS

Neurological and muscular symptoms were exhibited by 28 patients (7.9%). The mean age was 48.7 ± 25.2 months. The mean time between respiratory symptoms and neurological symptoms was 2.2 ± 1.5 days. The most common symptom was seizure (19/28, 67.9%), followed by myositis (5/28, 17.9%), increased intracerebral pressure (1/28, 3.6%), delirium (1/28, 3.6%), and severe headache (1/28, 3.6%). There was one severe case of meningitis with myocarditis (1/28, 3.6%). All seizures were febrile: 15 simple febrile seizures (78.9%), three complex febrile seizures (15.8%), and one febrile status epilepticus (5.3%). The mean age of nine patients with their first seizures was 37.9 ± 22.2 months, which was older than the typical age of onset for febrile seizure. All the patients, except one, were treated with oseltamivir. There were no deaths or chronic debilitating sequelae.

CONCLUSIONS

The neurological and muscular complications of influenza B infection in children are relatively mild, and febrile seizure is the most common. However, clinicians should be alert to the possibility of rare severe complications during influenza B outbreaks.

Use of inhaled iloprost in an infant with bronchopulmonary dysplasia and pulmonary artery hypertension

Pulmonary artery hypertension is a common cardiovascular complication in preterm infants with bronchopulmonary dysplasia which is associated with increased morbidity and mortality. Inhaled iloprost is used as a therapeutic option in pulmonary hypertension, especially in adults. There have been but a few reports on the use of iloprost for neonates and infants. We report the case of a 5 month-old-male infant who received neonatal intensive care for 4 months due to respiratory distress syndrome and prematurity, during which he developed bronchopulmonary dysplasia. Echocardiography showed severe pulmonary hypertension. The initial treatment included respiratory support with high frequency oscillatory ventilation (HFOV); however, his clinical condition did not improve. Inhaled iloprost with sildenafil, an oral phosphodiesterase-5 inhibitor, was thus used. With the administration of iloprost and sildenafil, his condition improved and he was weaned from oxygen. Our clinical experience suggests that iloprost is a promising therapy for pulmonary hypertension, especially when inhaled nitric oxide is unavailable.

Source localization of triphasic waves: implications for the pathophysiological mechanism

To investigate the current source location from the electroencephalograms (EEGs) of 12 patients who showed typical triphasic waves attributable to various causes, using the combination of a dipole source model and a distributed source model. The triphasic waves were explained by a single main dipole in 10 of the 12 patients, and 2 patients had two dipoles responsible for the triphasic waves. All the main dipoles had a radial orientation with respect to the frontal pole. The current density of the triphasic waves was distributed mainly in the bilateral medial frontal regions along the cingulate cortices. These findings suggest that current sources located in the medial frontal area are crucial for generating triphasic waves. The source localization may be useful for elucidating the pathophysiologic mechanism of generalized non-epileptic EEG activities, such as triphasic waves.

Identification of Patients With Childhood Moyamoya Diseases Showing Temporary Hypertension After Anesthesia by Preoperative Multifractal Hurst Analysis of Heart Rate Variability

OBJECTIVE

This study was performed to determine whether the preoperative multifractal Hurst analysis of heart rate variability might identify and characterize childhood patients with moyamoya disease (MMD) who showed temporary postoperative hypertension.

METHODS

We studied 59 childhood patients with MMD. Thirty were classified as hypertensive group when the mean arterial pressure in the postoperative recovery room was 120% or greater than that during the preoperative period and 29 were classified as normotensive group. The 2 groups were compared with respect to preoperative indices of heart rate variability including frequency-domain measures, approximate entropy, and very short-term multifractal Hurst exponents of RR intervals (RRI). Using preoperative indices that showed significant differences, discriminant analysis was performed to identify postoperative hypertensive patients.

RESULTS

Only exponents of the order > or =3 (H3alpha, H4alpha, and H5alpha) were significantly lower in the hypertensive group than in the normotensive group. Frequency-domain measures, approximate entropy, and the exponents of the order < or =2 were not significantly different in the 2 groups. Discriminant analysis using all of the three exponents correctly identified 27/30 (90%) of the postoperative hypertensive patients.

CONCLUSIONS

Preoperative very short-term multifractal Hurst analysis of RRI variability identified 90% of childhood MMD patients who developed postoperative hypertension. The preoperative characteristic of RRI variability was the reduced smoothness at the 8-second-long, local RRI regions within which a very large change of RRI occurs.

Different etiologies of intrauterine growth restriction and different consistencies in the occurrence of abnormal local nonstationarity of fetal heart rate

Fetuses with intrauterine growth restriction (IUGR) can be programmed in utero to develop hypertension in adult life. The etiology of IUGR in human fetuses is not uniform. The present study demonstrated that different etiologies of growth restriction, idiopathic cause, and pregnancy-induced hypertension, produce different consistencies in the occurrence of an abnormal local very-short-term nonstationarity of heart rate during intrauterine period. Whether the consistent abnormality that was found in the growth-restricted fetuses associated with pregnancy-induced hypertension is linked to the different risk of later hypertension requires future studies.

Instability and frequency-domain variability of heart rates in fetuses with or without growth restriction affected by severe preeclampsia

This study investigated how the instability and frequency-domain variability in heart rates differ between fetuses affected only by severe preeclampsia and fetuses affected by both severe preeclampsia and growth restriction. From their antepartum fetal heart rates and those of control fetuses, the very short-term intermittency (C1alpha) and the spectral powers were calculated to evaluate the instability and frequency-domain variability, respectively. The fetuses affected only by severe preeclampsia showed abnormally high C1alpha and low- and high-frequency power. The fetuses affected by severe preeclampsia and growth restriction showed even higher C1alpha than that of the fetuses affected by severe preeclampsia and abnormally reduced low-frequency power. Conclusively, when compared to the heart rates of fetuses affected only by severe preeclampsia, the heart rates of fetuses affected by severe preeclampsia and growth restriction showed a greater abnormal instability and an abnormally reduced variability at low-frequency range.

Fourier transformation of arterial Doppler waveforms of the lower extremity

PURPOSE

Although it is well known that the normal, triphasic pulsatile arterial Doppler waveform changes in shape as flow is impaired, interpretation of the waveform has largely been subjective. We aimed to describe the Doppler waveforms of the lower extremity objectively using Fourier transformation.

METHODS

Sixty-eight zero-crossing detector arterial recordings from 25 lower extremities were grouped as follows: group 1, no ischemic symptoms with an ankle-brachial index (ABI) > 0.9 (n = 17, 8 limbs); group 2, no ischemic symptoms with ABI < 0.9 (n = 18, 5 limbs); group 3, symptoms of claudication (n = 19, 7 limbs); group 4, rest pain or tissue loss (n = 14, 5 limbs). The waveforms were Fourier transformed and their amplitudes and phases were compared up to the third harmonic (H3).

RESULTS

Amplitudes of both the fundamental (H1) and second harmonic (H2) were predominant in group 1. In contrast, amplitudes of the H2 and H3 decreased with altered flow (p < 0.0001 for group 1 versus others). The phases of the H1 and H2 were delayed with altered flow (p < 0.05 for group 1 versus others). Phases of the H1 were different between group 2 and 4 (p < 0.05). The difference of phase between the H3 and H1 was shortened with altered flow (p < 0.05 for group 1 or 2 versus group 4). Multivariate analysis revealed that the relative amplitudes of the H2 and H3, the phases of the H1 and H2, and the relative phase of the H3 were significant discriminators among the groups.

CONCLUSION

Abnormal waveforms could be characterized by the predominant amplitude of the H1, phase delay of the H1 and H2, and shortening of the relative phase of the H3. These parameters may be useful in the evaluation of Doppler waveforms in patients with peripheral arterial disease.

A Consistent Abnormality in the Average Local Smoothness of Fetal Heart Rate in Growth-Restricted Fetuses Affected by Severe Pre-Eclampsia

An abnormality in cardiovascular regulation during the prenatal period has been suggested to be the pathophysiological link between fetal growth restriction and adult hypertension. The purpose of this study was to determine how consistently abnormal the local smoothness of the very-short-term heart rate is in growth-restricted fetuses associated with severe pre-eclamptic pregnancy. Multifractal Hurst analysis on the structure function of heart rate was performed in control fetuses (n =150), in fetuses affected by severe pre-eclampsia and not showing growth restriction (n =66) and in fetuses affected by severe pre-eclampsia and showing growth restriction (n =58). The very-short-term (< or =15 heart beats) generalized Hurst exponents of the order of -5 to 5 in three groups were compared. Each exponent quantifies an average local heart rate smoothness at 15-successive-heart rate sites, which were specified by the magnitude of the heart rate variation within the sites determined by and positively correlated with the order of the exponent. This means that the fetal heart rates within the sites of q > or =2 have a large fetal heart rate (FHR) variation, and those within the sites of q < or =-2 have a small FHR variation. In the fetuses affected by severe pre-eclampsia and not showing growth restriction, only values of the exponents of the order > or =2 were abnormally lower. In the fetuses affected by severe pre-eclampsia and showing growth restriction, the values of the exponents of all orders were abnormally lower. In conclusion, the local smoothness of heart rate is consistently abnormal regardless of the magnitude of heart rate variation within a very-short-term period in growth-restricted fetuses affected by severe pre-eclampsia.

A very-short-term intermittency of fetal heart rates and developmental milestone

We noticed that fetal heart rates (FHR) of immature fetuses intermittently showed unstable sudden and brief falls below baseline FHR that occur over a few or several heartbeats. The frightening falls do not occur in mature fetuses. In nonlinear dynamics, the degree of such abrupt falls in time series is quantified as intermittency. We aimed to investigate the nature and maturational changes of intermittency of the FHR in normal fetuses and to present the intermittency values of normal fetuses according to gestational weeks. FHR data of 450 normal fetuses between 23 and 40 wk of gestation were studied. We performed multifractal analysis and highlighted a very-short-term intermittency (C1alpha, 4 </= scale < 16 heartbeats). The C1alpha values exhibited a strong negative linear correlation (r = -0.732, p = 0.0001) with the gestational weeks. At 27-28, 29-30, 33-34, and 37-38 gestational weeks, the C1alpha values were significantly lower than those of the previous 2 or 4 gestational weeks. The maturation of normal fetuses is related to decreasing the severity of the unstable sudden and brief falls in FHR that is measured by C1alpha, the very-short-term intermittency. The C1alpha values according to the gestational weeks that we presented can be used as credible normal milestone values when estimating the degree of maturity of certain FHR. Because the C1alpha captures the degree of the unstable fall in FHR, the C1alpha may also be used in identifying sick fetuses that are associated with hemodynamic instability and sudden bradycardia.

Prediction of severity of mean arterial pressure elevation after tracheal intubation in hypertensive patients by preanesthetic recurrence quantification analysis of heart rates

BACKGROUND

We tried to determine whether the severity of additional mean arterial pressure (MAP) elevation after endotracheal intubation during general anesthesia could be predicted with preanesthetic recurrence quantification analysis of heart rates in hypertensive and normotensive patients.

METHODS

Twenty-four newly diagnosed hypertensive patients and 34 normotensive patients were included. We defined DeltaMAP = maximal mean MAP after endotracheal intubation - average MAP before general anesthesia. We classified each of the hypertensive and normotensive patients into mild (DeltaMAP </= 35 mmHg [median value of DeltaMAP in the hypertensive patients]) and severe group (DeltaMAP > 35 mmHg). Using preanesthetic RR interval data, we calculated classical linear and non-linear indices of RR interval dynamics, and performed recurrence quantification analysis to calculate three preanesthetic recurrence indices, percentage of recurrence (%REC), percentage of determinism (%DET), and maximal length of recurrence (Lmax).

RESULTS

In the hypertensive patients, all preanesthetic classical indices showed no significant difference between the mild and severe group and showed no significant linear correlation with the DeltaMAP. However, the Lmax was significantly higher in the severe than in the mild group (16.10 +/- 3.79 vs. 7.90 +/- 0.73, P < 0.005) and, moreover, linearly correlated with the DeltaMAP (r = 0.671, P = 0.001). In the normotensive patients, all preanesthetic classical and recurrence indices showed no significant difference between the two groups.

CONCLUSION

In hypertensive patients, the severity of additional MAP elevation after tracheal intubation during general anesthesia can be predicted by the preanesthetic recurrence quantification analysis of heart rates.

Increased intermittency and decreased nonstationarity of heart rates during the daytime in patients with neurocardiogenic syncope

INTRODUCTION

During head-up tilt (HUT) test, patients with neurocardiogenic syncope show a sudden severe decrease in heart rate at the beginning of their induced syncopal attacks (termed intermittency). They also exhibit slow and progressive increases in their mean heart rates long before the induced syncopal attacks (termed nonstationarity). The aim of this study was to test our hypothesis that during daily activity, although not as prominently as during HUT test, patients show different degrees of intermittency and nonstationarity compared to healthy persons.

METHOD AND RESULTS

Thirty patients with a positive HUT test and 30 healthy controls without a history of syncope were studied. The RR intervals of their 24-hour ambulatory ECGs were analyzed. To quantify the intermittency (C1) and nonstationarity (H1) behavior, multifractal analysis was performed using Mexican hat and Haar wavelet function, respectively. In the syncope group, C1 and H1 were significantly higher at 6 A.M.-6 P.M. and lower at 6 A.M.-midnight, respectively. However, the values were not different at midnight-6 A.M. The significant night-day circadian change shown in the control group was lost in C1 and diminished in H1.

CONCLUSION

Patients with neurocardiogenic syncope show increased intermittency and decreased nonstationarity of heart rates in the daytime during daily activity, and abnormal night-day circadian changes of the intermittency and nonstationarity. These findings may be useful in the early identification of patients with neurocardiogenic syncope and in the investigation of abnormalities in heart rate regulating mechanisms.

Alterations in irregular and fractal heart rate behavior in growth restricted fetuses

OBJECTIVES

To determine whether irregularity, and short- and long-term fractal correlation reflecting smoothness of heart rate behavior are changed in intrauterine growth restricted fetuses.

STUDY DESIGN

Fetal heart rate data of 192 normal fetuses and 86 intrauterine growth restricted fetuses between 31 and 42 weeks of gestation were studied. Approximate entropy to quantify irregularity, and short-term (< or =80 beats, alpha1) and long-term (>80 beats, alpha2) fractal scaling exponents to quantify the short- and long-term fractal correlation were calculated.

RESULTS

In the intrauterine growth restricted fetuses, the approximate entropy was significantly lower (P<0.001). The alpha2 value was significantly higher (P=0.0001) than in the normal fetuses, which performed better (F=34.2, P<0.0001) than other heart rate variability indexes in differentiating the intrauterine growth restricted fetuses from the normal fetuses in stepwise discriminant analysis.

CONCLUSIONS

Compared to normal fetuses, intrauterine growth restricted fetuses show a difference in that the irregularity of the fetal heart is decreased. A more apparent difference is that the long-term fractal correlation of the fetal heart is increased and the fetal heart is smoother in the long-term scale.

Decreased entropy of symbolic heart rate dynamics during daily activity as a predictor of positive head-up tilt test in patients with alleged neurocardiogenic syncope

Entropy measures of RR interval variability during daily activity over a 24h period were compared in 30 patients with a positive head-up tilt (HUT) test and 30 patients with a negative HUT test who had a history of alleged neurocardiogenic syncope. Two different entropies, approximate entropy (ApEn) and entropy of symbolic dynamics (SymEn), were employed. In patients showing a positive HUT test, the entropies were significantly decreased when compared with the patients with a negative HUT test. In addition, SymEn in the patients with a negative HUT test was significantly lower than in the normal controls. Discriminant analysis using SymEn could correctly identify 89.3% (520/582) of the 1 h RR interval data of the patients with a positive HUT test regardless of the time of day. Baseline entropies of heart rate dynamics during daily activity were found to be significantly lower in patients with alleged neurocardiogenic syncope and a positive HUT test than in those with the same history but with a negative HUT test. The decreased entropy of symbolic heart rate dynamics may be of predictive value of a positive HUT test in patients with alleged neurocardiogenic syncope.

Prediction of the oculocardiac reflex from pre-operative linear and nonlinear heart rate dynamics in children

This study was aimed to determine whether pre-operatively measured linear and nonlinear analysis of heart rate variability might predict the occurrence of the oculocardiac reflex (OCR) or other arrhythmia during strabismus surgery in children (n = 185, mean (SD) age = 8.09 (3.31) years). We compared time- and frequency-domain, and nonlinear dynamic indices of pre-operatively measured RR interval data between the OCR-positive group (maximum heart rate decrement = 20 beat.min-1 during the traction of extraocular muscle, n = 54), OCR-negative group (< 20 beat x min(-1), n = 78) and arrhythmia-positive group (all other arrhythmias; n = 53). pNN50, rMSSD, high-frequency power and nonlinear prediction error were significantly lower in the OCR-positive and arrhythmia-positive groups than in the OCR-negative group. Discriminant analysis using these indices could correctly identify 39/54 (72.2%) OCR-positive patients. Some pre-operatively measured indices of linear and nonlinear heart rate variability, especially when used in combination, are valuable for predicting significant bradycardia during strabismus surgery in children.

ECP level in nasopharyngeal secretions and serum from children with respiratory virus infections and asthmatic children

Infection with respiratory virus has been shown to exacerbate asthma in humans. However, the role of a respiratory virus in the pathogenesis of chronic asthma and/or wheezing in young children has not been clearly defined. It has also been debated whether virus-induced wheezing in young children is one entity and allergic asthma another, or whether they are different expressions of the same disease. The present study was done to compare ECP concentrations in nasopharyngeal secretions and serum from 32 nonasthmatic wheezing children with viral infections (RSV in 15 children; influenza B virus in 17 children detected by immunofluorescence antibody technique), 8 asthmatic children without viral infections, and 13 normal children as the controls to understand the role of eosinophil inflammation. The geometric mean of ECP in nasopharyngeal secretions was significantly higher in asthmatic children than in children with virus-induced wheezing (p < 0.05). ECP levels of nasopharyngeal secretions from children with the virus-induced wheezing were significantly greater than those of the controls. However, there were no significant differences in ECP levels in serum among subjects.

Decreased RR interval complexity and loss of circadian rhythm in patients with congestive heart failure

The present study investigated how the RR interval complexity and variability and their circadian rhythms alter for patients with congestive heart failure (CHF). Sixteen patients aged between 41 and 72 years with CHF and 20 control subjects were included. 24-h ambulatory electrocardiographic recordings were analyzed, and digitized data was partitioned into sections of 30-min duration. For each section, time- and frequency-domain indices, and complexity indices of heart rate variability were calculated. For CHF patients, 24-h average values of all indices were significantly decreased. The circadian rhythms of mean RR intervals were preserved and resembled the abnormal circadian rhythms of the low-frequency power. The circadian rhythms of high-frequency power and all complexity indices shown in the normal control were lost. Conclusively, the patients with CHF showed decreased RR interval complexity and loss of its circadian rhythm, in addition to decreased frequency-domain RR interval variability and its abnormal circadian rhythm.

Abnormal cardiac autonomic activity and complexity in newly diagnosed and untreated hypertensive patients after general anesthesia

To investigate change of cardiac autonomic activity and cardiac complexity during general anesthesia in hypertensive patients, we analyzed electrocardiographic (ECG) data using power spectral analysis and approximate entropy (ApEn). Anesthesia was performed by a mixture of enflurane and nitrous oxide. From 10 minutes before induction of anesthesia(resting state) until 20 minutes after induction, ECG data were obtained from newly diagnosed and untreated hypertensive (n = 18) and normotensive patients (n = 18). Period 1 was defined as the initial 10 minutes after induction and period 2 as the following 10 minutes. The low-, mid-, and high-frequency power and the values of ApEn of the two groups were calculated from ECG recording. At resting state, the powers in all frequency bands and the values of ApEn in hypertensive patients did not differ from those of normotensive patients. During periods 1 and 2, the powers of all frequency range significantly decreased in normotensive group (p<0.05), while they did not change in hypertensive group. The values of ApEn in normotensive patients decreased significantly only during period 2, while those in hypertensive patients decreased during periods 1 and 2 (p<0.05 and p<0.05, respectively). These results suggest that, in the hypertensive patients, persistent autonomic activity under the condition of suppressed cardiac complexity may contribute to the unstable hemodynamic insults from the outset of general anesthesia.

Analysis of induced sputum to examine the effects of inhaled corticosteroid on airway inflammation in children with asthma

BACKGROUND

Analysis of induced sputum can be performed safely in children with asthma and is useful for both cellular and biochemical markers of inflammation. Glucocorticosteroid inhalation has become the first line therapy for chronic asthma by suppressing airway inflammation, which produces the decrease of bronchial hyperreactivity and reduces the number of eosinophil in bronchial submucosa.

OBJECTIVE

To determine the characteristics of the inflammatory cells and their markers in sputum and to examine the pharmacokinetic effects of glucocorticoid within 3 hours after inhalation therapy on FEV1 and sputum inflammatory indices in children with clinically defined chronic asthma.

METHODS

Thirty subjects with asthma included 14 current symptomatic asthmatics and 14 normal controls inhaled 4.5% hypertonic saline for 10 minutes by nebulizer. The expectorated sputum were collected from all asthmatics before and 3 hours after corticosteroid inhalation for children with asthma and were reduced by dithiotreitol. Total cell counts and differentials were determined. ECP was measured by CAP system. Interleukin-5, GM-CSF and albumin were measured by double sandwich ELISA.

RESULTS

The mean eosinophil percentage and ECP in induced sputum of asthmatics were significantly higher than that of controls. The induced sputum samples obtained after glucocorticoid inhalation showed a significant reduction in mean eosinophil percentage, but FEV1, IL-5, GM-CSF, albumin, and ECP values were not significantly decreased.

CONCLUSION

The present results in induced sputum may be interpreted to reflect direct steroid action on airways and lack of effect on bone marrow effectors at 3 hours after glucocorticoid inhalation.

Non-linear cardiac dynamics and morning dip: an unsound circadian rhythm

The frequency of sudden cardiac death increases in the morning. The relationship between decreased complexity of heart rate dynamics and sudden cardiac death has been documented. An understanding of circadian variation in the complexity of cardiac dynamics may be important to predict and prevent sudden cardiac death. Dynamic 24-h electrocardiographic recordings were obtained from 30 healthy ambulant subjects aged 41-50 years, and the digitized data were partitioned into sections of 30 min duration. For each section, four indexes obtained from separate algorithms of non-linear dynamics of the RR interval--modified correlation dimension, Lyapunov exponent, approximate entropy, and fractal dimension--were calculated. Normalized low-(0.04-0.15 hertz) and high-frequency (> 0.15 hertz) components were also calculated. All four indexes of non-linear dynamics showed a remarkably similar circadian rhythm: a prominent morning dip preceded by a steep decline during the late night, a recovery during the evening and a peak around midnight. In the morning, the low-frequency component rose rapidly with concomitant reduction in the high-frequency component. The complexity of cardiac dynamics decreases significantly in the morning, and this may contribute to the ominously increased rate of cardiac death in the morning hours.

Chaotic and periodic heart rate dynamics in uncomplicated intrauterine growth restricted fetuses

We studied how chaotic and periodic heart rate dynamics differ between normal fetuses (n = 192) and uncomplicated intrauterine growth restricted fetuses (n = 86), aged 31-42 weeks of gestation. We analyzed each fetal heart rate time series for 25 min. We quantified the chaotic dynamics of each fetal heart rate time series by correlation dimension. The periodic dynamics were analyzed by power spectral analysis. The correlation dimension and, therefore, the complexity, of the heart rate dynamics of the uncomplicated intrauterine growth restricted fetuses was significantly lower than that of the normal fetuses, which was marked at 38-42 weeks of gestation. The low-frequency (0.04-0.15 Hz) component and, therefore, the periodicity of the low-frequency range was significantly higher than that of the normal fetuses during all the gestational weeks. These results mean that, although the intrauterine growth restricted fetuses are not severely compromised, the overall integrity of their cardiovascular control is impaired, especially at term; and sympathetic modulation is increased, both of which may contribute to increased perinatal mortality.