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PubMed2006

Sporadic fetal heart rate decelerations associated with electrocortical changes in fetal lambs.

AIM: The purpose of this study was to determine a relationship between sporadic fetal heart rate (FHR) decelerations and fetal electrocortical changes in physiologically normal sheep fetuses. MATERIALS AND METHODS: A total of 20 experimental observations were conducted on eight chronically instrumented fetal lambs. For electrocorticogram (ECoG) recording, two stainless steel electrodes were implanted bilaterally on the fetal parietal skull. Classifications of ECoG tracings were visually divided into periods of low, high, intermediate and transitional voltage. During day and night observations, sporadic FHR decelerations related to fetal ECoG changes were counted. RESULTS: We found that 65% of the total sporadic FHR decelerations occurred in relation to fetal ECoG changes. The largest number of sporadic FHR decelerations was associated with a switch from low voltage to high voltage ECoG (37%). However, the greatest frequency of sporadic FHR decelerations occurred during intermediate ECoG periods (34%). CONCLUSION: The majority of sporadic FHR decelerations observed in physiologically normal sheep fetuses were associated with fetal ECoG changes.

Animals↗
PubMed1991

Response inhibition initiates cardiac deceleration: evidence from a sensory-motor compatibility paradigm.

Two experiments tested the hypothesis that response selection processes alter the timing of the shift between anticipatory cardiac deceleration and acceleratory recovery. Experiment 1 compared changes in cardiac interbeat interval induced by the manipulation of sensory-motor compatibility in a four choice reaction time task. A direct spatial mapping between a linear array of light-emitting diodes (LEDs) was compared to randomly assigned, indirect (non-compatible) mappings. Experiment 2 repeated these two tasks and added a two choice condition with direct spatial mapping, a task frequently employed to examine heart rate deceleration. Fifteen college aged males participated in Experiment 1; 18 college aged males participated in Experiment 2. In both experiments anticipatory cardiac deceleration either reached a plateau or shifted to acceleration by the interbeat interval in which the stimulus occurred. In contrast to previous reports, a secondary deceleration, rather than cardiac acceleration, often followed the stimulus. The secondary deceleration was greater with non-compatible mapping, slow response speeds, and short intertrial intervals. The findings suggested that the motoric inhibition required during response selection induces a phasic cardiac deceleration.

Adolescent↗
PubMed2004

Uniform vascular contrast enhancement and reduced contrast medium volume achieved by using exponentially decelerated contrast material injection method.

PURPOSE: To investigate in computed tomographic (CT) angiography whether an exponentially decelerated contrast medium injection, as compared with a standard constant-rate injection, can facilitate uniform vascular contrast enhancement with a reduced contrast material volume. MATERIALS AND METHODS: CT angiography of the abdominal aorta was performed in 46 subjects by using an exponentially decelerated injection method: 134 mL of contrast medium was injected for 40 seconds, starting at 4.0 mL/sec and decreasing exponentially to 2.7 mL/sec by the end of the injection. Twenty-one of these subjects also underwent CT angiography with a constant-rate injection: 160 mL of contrast medium was injected for 40 seconds at a constant rate of 4 mL/sec. Time-enhancement curves and the magnitude of peak vascular enhancement were measured. Enhancement uniformity was evaluated by using three indexes: (a) duration of contrast enhancement achieved within 80% of the peak (80% DCE), (b) SD of the normalized contrast enhancement (SDNCE) measured from the beginning of spiral CT scanning to the time when the enhancement decreased to a level lower than the beginning level, and (c) slope of the enhancement curve calculated by using linear regression analysis. RESULTS: Exponentially decelerated injection resulted in more uniform enhancement. Mean values generated by using exponentially decelerated versus constant-rate injection in 21 paired comparisons were, respectively, 30.8 seconds +/- 5.0 versus 22.6 seconds +/- 7.6 for 80% DCE, 0.052 +/- 0.017 versus 0.086 +/- 0.031 for SDNCE, and 0.47 HU/sec +/- 0.70 versus 2.27 HU/sec +/- 0.87 for slope (P <.001 for all indexes). Compared with the peak enhancement resulting from the constant-rate injection, that resulting from the exponentially decelerated injection was reduced by a mean of 17.2% +/- 10.0. CONCLUSION: Uniform vascular contrast enhancement and reduced contrast medium volume, which are desirable in CT angiography, can be achieved with exponentially decelerated injection.

Abdomen↗
PubMed2005

Catastrophe theory model for decelerations of fetal heart rate.

BACKGROUND: Decelerations of fetal heart rate (FHR) are the results of many pathophysiological factors that modulate the intrinsic rate of the heart. FHR change is a complex phenomenon and can be viewed as a type of nonlinear dynamic system. This paper presents a qualitative model of FHR decelerations based on catastrophe theory, especially to account for abrupt heart rate changes seen in variable decelerations. METHODS: One of the elementary catastrophes, the cusp catastrophe, was used to model FHR changes seen in variable, late, and early decelerations. RESULTS: Catastrophe theory describes typical variable decelerations as an abrupt response to a slowly changing force of attack (uterine contraction) and physiological defense. Because of its three-dimensionality and topological features, the cusp catastrophe model provides a qualitatively satisfying description of FHR decelerations. CONCLUSION: The organized complexity of living systems offers the best hope for the application of catastrophe theory. The nature of the elementary catastrophes will be essential knowledge in the mathematical analysis of biology.

Female↗
PubMed2002

Prevention of growth deceleration after withdrawal of growth hormone therapy in idiopathic short stature.

The treatment of children with idiopathic short stature by daily injections of human GH (hGH) is followed after its withdrawal by a growth deceleration with normal serum GH and IGF-I levels. The present study was designed to understand and prevent growth deceleration. We hypothesized that this phenomenon is due to tolerance at the target organ level, that tolerance develops in response to the unphysiological pharmacokinetics of daily-injected hGH, and that alternate day hGH therapy will prevent it. Thirty-eight prepubertal children with idiopathic short stature, aged 3.3-9.0 yr, were studied. Their heights were less than -2 SD score, growth rate was above the 10th percentile for age, bone age was less than 75% of chronological age, and the stimulated serum GH concentration was greater than 10 microg/liter. The children were matched for sex, height, and growth velocity SD score to receive daily or alternate day hGH at the same weekly dose of 6 mg/m(2) for a period of 2 yr. The 1st and 2nd year mean growth velocities were 3.4 and 2.3 SD score for the daily therapy group and 3.0 and 2.0 SD score for the alternate day group, respectively (P = NS). Over the initial 6 months after withdrawal of therapy, and growth velocity decelerated to a nadir of -3.9 SD score in the daily therapy group, whereas it decelerated in the alternate day group to only -0.2 SD score (P < 0.01). Over the entire 2 yr off therapy the latter group maintained mean growth rates of -0.2 to -1.2 SD score, similar to their pretreatment velocities. The daily group recovered slowly to resume their mean pretreatment rate only on the fourth semiannual evaluation off therapy. The cumulative 4-yr growth velocity (2 yr on and 2 yr off therapy) of the alternate day group was greater than that of the daily therapy group (mean, 0.9 vs. 0.3 SD score; P < 0.002). At the end of the 4-yr therapy period, the adult height prediction of the alternate day group was greater than that of the daily group by a mean 6.5 cm (P = 0.06). It is concluded that growth deceleration after withdrawal of hGH therapy in idiopathic short stature is due to tolerance to GH and IGF-I in response to the unphysiological pharmacokinetics of daily-injected hGH and that alternate day therapy allows for an alternate day physiological GH profile, thus preventing tolerance during therapy and growth deceleration thereafter.

Body Height↗
PubMedDate not supplied

A functional fatiguing protocol and deceleration time of the shoulder from an internal rotation perturbation.

CONTEXT: Muscular fatigue impedes sensorimotor function and may increase the risk of shoulder injury during activity. The effects of fatigue on the sensorimotor system of the shoulder have been studied with various results. Deceleration times have been used to study neuromuscular control of the shoulder; however, no studies involving the effects of fatigue on deceleration times have been reported. OBJECTIVE: To compare shoulder deceleration times after a shoulder internal rotation perturbation before and after a repetitive throwing exercise protocol. DESIGN: A 2 x 2 repeated-measures design. SETTING: Exercise and sport injury laboratory. PATIENTS OR OTHER PARTICIPANTS: Twenty healthy, recreationally active men (age = 24.76 +/- 4.03 years, height = 178.41 +/- 8.36 cm, mass = 80.16 +/- 15.20 kg) volunteered to participate in the study. To ensure familiarity with the overhead motion, all subjects chosen had previously participated in an overhead throwing sport. INTERVENTION(S): The independent variables were time (preintervention and postintervention) and session (experimental and control). The intervention consisted of continuous overhead throwing. The subjects were considered fatigued when a 10% decrease in velocity was noted on 3 consecutive pitches. MAIN OUTCOME MEASURE(S): Time necessary to decelerate from an internal rotation perturbation. RESULTS: Deceleration time was significantly increased by the fatiguing intervention ( P = .001). CONCLUSIONS: The decreased ability to decelerate may be an adaptive response by the subjects to dissipate a lower percentage of force per second.

Journal Article↗
PubMed1987

An active management approach to the postdate fetus with a reactive nonstress test and fetal heart rate decelerations.

Reports have shown that a reactive nonstress test (NST) with decelerations in the postdate patient is associated with an increase in perinatal morbidity. Based on these observations, patients who exhibited this fetal heart rate (FHR) pattern during NST had labor induced. The purpose of this report was to determine what impact, if any, this approach had on subsequent maternal and fetal outcome. The pregnancy outcome of 470 patients who delivered during 1984 within seven days of their last NST was compared with data from this institution in 1980. The last NST was reactive in 420 patients (89.4%) and nonreactive in 50 (10.6%). Fetal heart rate decelerations occurred in 130 patients (27.7%); of these, 96 (73.9%) were reactive and 34 (26.1%) nonreactive. Postdate patients whose last NST was reactive with decelerations had similar outcomes to patients with a nonreactive NST on their last test, but less favorable outcomes than patients with reactive tests alone. Comparison with data from our institution in 1980 shows that prompt induction of labor in the postdate patient with a reactive NST and decelerations resulted in significantly lower perinatal morbidity, with no corresponding increase in maternal morbidity. These results lead us to conclude that a reactive NST without FHR decelerations is a reliable indicator of fetal well-being in the postdate pregnancy. However, in the postdate pregnancy with a reactive NST with FHR decelerations, induction of labor is indicated.

Female↗
PubMed1981

Combined decelerations--clinical significance and relation to uterine activity.

A combined fetal heart rate deceleration consists of a first (either early or variable) component and a second (late) component. All patients with combined decelerations during a 2-year period of routine fetal monitoring were studied. The incidence was 1.1% (70 patients). Most patient were at low risk, and the combined decelerations appeared predominantly late in the first stage of labor. In all but 5, labor was stimulated by oxytocin infusion. In two thirds of patients, intrauterine pressure was recorded; uterine hyperactivity was found in 78.7%. Combined decelerations with a total loss of at least 90 beats and lasting for at least 60 seconds were associated with low fetal scalp pH. Ten percent of infants were born in the occiput posterior position. The results indicate a relation between abnormal uterine activity and combined fetal heart decelerations. This type of deceleration could serve as a warning signal of excessive oxytocin administration.

Electrodes↗
PubMed1996

[The perinatal risk factors and periventricular leukomalacia (PVL) in premature infants--relationship between fetal heart rate decelerations and PVL].

Periventricular leukomalacia (PVL) has recently been recognized as an important risk factor of neurological impairment in premature infants. We studied 29 PVL cases on perinatal risk factors comparing with a non-PVL matched control group retrospectively. Variable decelerations were more frequently observed with statistical significance in the PVL group in the intrapartum period. Then another study was conducted to evaluate the relationship between fetal heart rate (FHR) decelerations and cystic PVL prospectively. Since January 1993 through December 1994 we studied 209 low birth weight infants (31.1 +/- 3.2 weeks, 1,424 +/- 419 g) who had been subjected to intrapartum FHR monitoring and postnatal sonographic intracranial examinations sequentially every 7 days until discharge. Cystic PVL was detected in 6 of 209 cases (2.9%) and occurred only in infants who had revealed severe variable deceleration or prolonged deceleration (6/37, 16%) in intrapartum FHR monitoring. We conclude that in low birth weight infants intrapartum severe variable deceleration or prolonged deceleration might play a causal role in cystic PVL.

Bradycardia↗
PubMed2001

Relationship between fear of falling and balancing ability during abrupt deceleration in aged women having similar habitual physical activities.

The purpose of this study was to evaluate the influence of fear of falling on balancing ability during abrupt deceleration in aged women. The subjects were 20 women aged between 67 and 75 years. They were classified into two groups, one having a fear of falling (group FF, n = 10) and another without this fear (group NFF, n = 10). The two groups had similar daily physical activities. Changes in the centre of foot pressure (CFP) were measured during postural sway following horizontal deceleration of the force platform on which they were standing, and the response time and CFP displacement were evaluated. In addition, the electromyogram (EMG) onset in the tibialis anterior muscle and medial gastrocnemius muscle during abrupt deceleration, and its difference between the two muscles were measured. and the relative level of co-contraction of antagonistic muscles (the co-contraction index, CCI) in the lower extremity muscle group was calculated. The response time and CFP displacement immediately after abrupt deceleration were significantly higher in group FF than in NFF (P < 0.05). The EMG onset in the two muscles did not significantly differ between the two groups. The difference in EMG onset between the two muscles was significantly lower in group FF than in NFF (P < 0.05). The CCI was significantly higher in group FF than in NFF (P < 0.05). These results suggest that there were negative effects of a fear of falling on the balancing ability immediately after abrupt deceleration. This may be because a fear of falling increases the co-contraction of antagonist muscles in the lower extremity muscle group.

Aged↗
PubMedDate not supplied

Prevalence of fetal heart rate decelerations in self-referred low-risk patients in the third trimester.

We tested the hypotheses that fetal heart rate decelerations are present during the third trimester in most low risk pregnant women, the prevalence of decelerations is a function of the length of time fetal heart rate monitoring occurs and their presence is not associated with an adverse prognosis. We performed a retrospective chart review of 114 self-referred low-risk pregnant patients who presented to the labor and delivery triage area of a tertiary care hospital at 26-41 weeks gestation. None required admission to the hospital. The control group consisted of patients who delivered immediately before and after the delivery of the study patient. Normal long-term variability and fetal baseline heart rate were found in all electronic fetal monitoring tracings. Accelerations were present in 91% and decelerations in 65% of patients. There was no correlation between length of time of monitoring and the incidence of decelerations. At delivery, there were no differences in birthweight, gestational age, 5-min Apgar scores or cord pH between the control and study patients. Variable decelerations were a common finding in the third trimester of low-risk pregnant patients who self referred to labor and delivery triage. They were not prognostic of an adverse perinatal outcome.

Adult↗
PubMed1999

Significance for fetal outcome of poor prognostic features in fetal heart rate traces with variable decelerations.

OBJECTIVE: To determine the clinical significance of the existence of poor prognostic features in fetal heart rate (FHR) traces with variable decelerations. STUDY DESIGN: This study was prospectively performed on 167 randomly selected women with a singleton pregnancy at term. Ninety-one patients had an FHR trace without pathological features. The remaining 76 women had variable decelerations and their FHR traces were analyzed carefully for the existence of poor prognostic features. Fetal and neonatal outcomes were compared in the normal and variable deceleration groups. RESULTS: There were statistically significant differences between the groups in 1 and 5 minute Apgar scores, fetal heart rate (FHR), umbilical artery blood pH, pCO2; whereas no significant differences were found in the levels of umbilical artery HCO3, pO2. CONCLUSION: Prolonged deceleration had the highest specificity for 1 minute Apgar score < 7.5 minute Apgar score < 7 and umbilical artery blood pH < 7.20 (95.0%, 96.3%, 97.5%, respectively). Loss of variability during deceleration showed the highest specificity for the same fetal features (66.7%, 72.3%, 63.9%, respectively). All other poor prognostic features had high specificities but low sensitivities.

Adult↗
PubMed1980

Clinical significance of fetal heart rate patterns during labor. VI. Early decelerations.

In a population of high-risk patients who had continuous "direct" monitoring during labor, 598 (46%) had no decelerations during the first stage, while 247 (19%) had presented early decelerations before completion of dilatation. The clinical characteristics, the fetal heart rate (FHR) baseline alterations, and neonatal outcome were compared between these two groups: there were no differences in any of the aspects evaluated, except that there was transient tachycardia more often among the early-decelerations group. The patients who had no decelerations were subdivided into vaginal deliveries and cesarean deliveries, and the same parameters were compared again: the cesarean section group had longer recordings and more contractions, lower Apgar 1 and 5 minute scores, and higher incidences of Apgar scores less than or equal to 6 at 1 minute, while all other aspects were similar. A possible explanation was that 82% of cesarean sections were done under general anesthesia and only 3% of vaginal deliveries. The implication of ruptured membranes in the etiology of early decelerations was extensively reviewed and discussed in view of these findings. It is concluded that amniotomy does not seem a maneuver deleterious to the fetal well-being.

Adult↗
PubMed1989

Effect of prolonged hypoxemia on fetal heart rate accelerations and decelerations in sheep.

Experiments were conducted in 10 chronically catheterized fetal sheep to determine the effect of 24 hours of hypoxemia in the absence of progressive acidemia on fetal heart rate accelerations and decelerations. Fetal hypoxemia was produced by mechanically restricting uterine blood flow with a vascular clamp placed around the maternal common internal iliac artery. Fetal arterial oxygen tension decreased from 22.3 +/- 1.8 to 17.8 +/- 1.5 mm Hg at 2 hours and remained low for the 24-hour experimental period. Fetal pH decreased from 7.34 +/- 0.01 to 7.20 +/- 0.05 at 2 hours and returned to normal values by 12 hours. No significant change was observed in the number or characteristics of fetal heart rate accelerations or decelerations during the 24-hour control period. There was a significant increase in the number of accelerations from 48 +/- 4 to 63 +/- 4 per hour at 8 hours of hypoxemia followed by a return to control values by 12 hours. There was no significant change in the mean amplitude or duration of accelerations. There was a significant increase in the number of decelerations per hour with an associated increase in the mean amplitude but a decrease in the mean duration of decelerations during the first 16 hours of hypoxemia. We conclude that prolonged hypoxemia in fetal sheep leads to an initial increase in the number of both accelerations and decelerations in fetal heart rate followed by a return to normal patterns indistinguishable from those of the normoexemic fetus.

Animals↗
PubMed1991

Variable decelerations in reactive nonstress tests with decreased amniotic fluid index predict fetal compromise.

A total of 3158 patients at greater than or equal to 34 weeks' gestation undergoing nonstress tests and amniotic fluid index determinations were divided into six groups according to the amniotic fluid index and the nature of the decelerations. Fetuses with antepartum decelerations had statistically significantly increased incidences of intrapartum decelerations and operative deliveries because of intrapartum "distress," regardless of the amniotic fluid index. They also had significantly increased rates of neonatal acidosis and low Apgar scores when there were "severe" decelerations and an amniotic fluid index less than 5 in the antepartum period. Thus spontaneous decelerations in reactive nonstress tests with an amniotic fluid index less than 5 may predict fetal compromise.

Adolescent↗
PubMed1992

The physiologic mechanisms of variable decelerations.

OBJECTIVES: The purpose of this study was to determine the cause and physiologic consequences of variable decelerations. STUDY DESIGN: Previous studies of heart rate changes in human and experimental animals were critically reviewed with respect to the autonomic nervous system component, the cause of the increased vagal activity, and the role of cord compression or other stimuli in these heart rate changes. RESULTS: There is abundant evidence from experimental and human studies that variable decelerations can be reproduced by either cord compression or head compression. The vagal reflex produced is probably caused by a combination of chemoreflex (earlier in the deceleration) and baroreflex (later). The variable deceleration is accompanied by an acidosis, primarily respiratory, and probably hypoxemia. Cord compression results in decreased umbilical blood flow. CONCLUSIONS: Recent Doppler velocimetry studies suggest that even though the variable decelerations may be similar in duration and depth, the reduction of umbilical blood flow may be greater when the prime cause is cord compression than when the prime cause is vagal reflex from another source.

Amniotic Fluid↗
PubMed1978

Anticipatory HR deceleration as a function of perceived control and probability of aversive loud noise: a deployment of attention account.

Five groups of 10 undergraduate subjects each participated in an experiment to examine the effects of perceived control over, and the probability of occurrence of, noxious (white-noise) stimulation on anticipatory heart rate (HR) deceleration. All groups performed an arithmetic task, the numbers for which were changed on each of the 20 trials, but three groups were defined as active groups since they were instructed that the occurrence of noxious stimulation was contingent upon their performance on the task. The actual probability of occurrence of noxious stimulation (i.e., either 0.9, 0.5 or 0.1) was manipulated between these three groups. A fourth (passive) group (0.5 probability of occurrence) was instructed as to the non-contingent relationship between performance and the aversive white noise. The last group was a control group which only performed the task, and thus both provided an estimate of the rate of return to baseline following the expected HR acceleration to the task and eliminated the need for a within-subject control period to assess HR deceleration. The results indicated that all active and passive groups produced significant HR decelerations, relative to the control group, prior to the noxious stimulus. However, all active groups (regardless of probability levels) displayed significantly greater, and required more trials to maximally develop, anticipatory deceleration than the passive group. In addition, the results for the active groups revealed a direct relationship between the probability of occurrence of noxious stimulation and the magnitude of anticipatory deceleration. It is argued that the results cannot be adequately accommodated by the preparatory-adaptive-response theory. A deployment-of-attention account is suggested since it appears both to account for the obtained pattern of results completely and to generate additional testable predictions for the future.

Adaptation, Psychological↗
PubMed1990

Abnormal velocity waveforms of the umbilical artery in growth retarded fetuses: relationship to antepartum late heart rate decelerations and outcome.

In 70 intrauterine growth-retarded (IUGR) fetuses with antepartum late heart rate decelerations recordings of velocity waveforms of the umbilical artery were made with Doppler ultrasound and calculated as pulsatility indexes (PI). In 29 of these fetuses longitudinal recordings were made. Abnormal PIs preceded the occurrence of late heart rate decelerations in 27 (93%) of the 29 fetuses. The median duration of the interval between the first abnormal PI and the first appearance of antenatal heart rate decelerations was 17 days (range 0-60 days). This wide range can mainly be attributed to the gestational age at which the first abnormal velocity wave-form was recorded; during early gestation the interval was much longer than later in pregnancy. Absent end-diastolic velocity (AEDV) was found in 17 of the 29 fetuses (59%) and preceded the occurrence of decelerations with a median interval of 12 days. In the total group, 4 of the 70 IUGR fetuses with antepartum decelerations had a normal velocity waveform of the umbilical artery. Fetuses with AEDV (n = 45) were more severely growth retarded and were delivered at an earlier gestational age than those with end-diastolic velocity (n = 25). Also perinatal mortality and morbidity were higher in the group with AEDV. Yet, when fetuses were matched for gestational age and birth weight no differences in perinatal outcome were found in the groups with and without end-diastolic velocity.

Adult↗