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PubMed1995

Relationship of the third heart sound to transmitral flow velocity deceleration.

BACKGROUND: The third heart sound (S3) occurs shortly after the early (E-wave) peak of the transmitral diastolic Doppler velocity profile (DVP). It is thought to be due to cardiohemic vibrations powered by rapid deceleration of transmitral blood flow. Although the presence, timing, and clinical correlates of the S3 have been extensively characterized, derivation and validation of a causal, mathematical relation between transmitral flow velocity and the S3 are lacking. METHODS AND RESULTS: To characterize the kinematics and physiological mechanisms of S3 production, we modeled the cardiohemic system as a forced, damped, nonlinear harmonic oscillator. The forcing term used a closed-form mathematical expression for the deceleration portion of the DVP. We tested the hypothesis that our model's predictions for amplitude, timing, and frequency of S3 accurately predict the transthoracic phonocardiogram, using the simultaneously recorded transmitral Doppler E wave as input, in three subject groups: those with audible pathological S3, those with audible physiological S3, and those with inaudible S3. CONCLUSIONS: We found excellent agreement between model prediction and the observed data for all three subject groups. We conclude that, in the presence of a normal mitral valve, the kinematics of filling requires that all hearts have oscillations of the cardiohemic system during E-wave deceleration. However, the oscillations may not have high enough amplitude or frequency to be heard as an S3 unless there is sufficiently rapid fluid deceleration (of the Doppler E-wave contour) with sufficient cardiohemic coupling.

Blood Flow Velocity↗

PubMed1989

Cerebral artery flow velocity acceleration and deceleration characteristics in newborn infants.

To evaluate maturational differences in the cerebral artery blood flow velocity characteristics, we measured the middle cerebral (MCA) and basilar artery blood flow velocity and time intervals using a real-time imaging pulsed Doppler system in 39 preterm and 25 term infants. Preterm MCA and basilar artery mean Doppler spectral area under the curve were approximately 22 and 25% lower than the corresponding term values, with a significant increase during gestation as revealed by regression models. Paradoxically, the mean MCA systolic acceleration and deceleration slopes were approximately 28 and 18% higher in preterm than in term infants: acceleration 701.2 +/- 160 cm/s2 versus 546.4 +/- 156.5/s2 (p less than 0.005), and deceleration 222.2 +/- 71.6 cm/s2 versus 188.2 +/- 52.2 cm/s2 (p less than 0.05), respectively. Similarly, acceleration and deceleration pressure half times for MCA were about 15 and 18% shorter in the preterm (p less than 0.01 and less than 0.005). Multiple regression models controlling for velocity and frequency terms revealed an inverse relationship between gestational age and MCA acceleration (p less than 0.005), and a positive relationship between gestational age and MCA acceleration pressure half times (p less than 0.02). In preterm infants the MCA specific index of pulsatility was about 32% higher (p less than 0.05) than in the term, which was also inversely related to gestational age in a regression model controlling for velocity terms (p less than 0.02). However, the basilar artery acceleration and deceleration slopes were not significantly different between term and preterm groups, nor showed a significant gestational age effect in the multiple regression models.(ABSTRACT TRUNCATED AT 250 WORDS)

Basilar Artery↗

PubMed1970

Independently delivered food decelerates fixed-ratio rates.

Following fixed-ratio baselines, the independent delivery of reinforcers was scheduled alone or concomitant with the fixed-ratio schedule for all subjects. Systematic manipulations of either the interreinforcement interval or the ratio size were also made during concomitant schedules. Response rates during the independent delivery of reinforcers did not decelerate until the subjects had been exposed for 50 or more sessions. Rates decelerated after a few sessions when the interreinforcement intervals were less than half of the original value and scheduled along with the ratio dependency. When both schedules were available, reductions in the ratio size resulted in slight deceleration of response rate when compared with the level of deceleration yielded by reductions in the independent reinforcement intervals.

Journal Article↗

PubMed1997

The effects of "decelerated" rehabilitation following anterior cruciate ligament reconstruction on a hyperelastic female adolescent: a case study.

Current concepts in postoperative anterior cruciate ligament (ACL) reconstruction management include participation in an "accelerated" rehabilitation program. There are no published reports examining the effects of accelerated or conservative rehabilitation on subjects with generalized ligamentous hyperelasticity. The purpose of this case study was to examine the effects of a conservative or "decelerated" rehabilitation program on the functional outcome of a hyperelastic female adolescent athlete following ACL reconstruction. The subject was a 15-year-old female basketball player who sustained a unilateral ACL tear and underwent subsequent ACL reconstruction using a patellar tendon autograft. The subject immediately began participation in a "decelerated" rehabilitation program in which the intensity and rate of progression was decelerated, emphasizing a prolonged period of maximum graft protection. Progress was objectively quantified with a battery of diagnosis-specific tests at scheduled intervals. Results at 52 weeks postoperative revealed normal range of motion, proprioception, balance, knee stability, quadriceps strength, hamstring strength, and subjective assessment values, and only a 4.0% deficit in functional scores. Our results suggest a "decelerated" rehabilitation program may be appropriate for the population with generalized ligamentous hyperelasticity by yielding excellent functional results without compromising the integrity of the graft and, ultimately, knee stability.

Adolescent↗

PubMed1998

Foetal compromise by spontaneous foetal heart rate deceleration in reactive non-stress test and decreased amniotic fluid index.

One hundred and sixty-three consecutive pregnant women with > 32 weeks gestation, undergoing non stress test (NST) and amniotic fluid index (AFI) determination were divided into six groups according to the amniotic fluid index and the nature of decelerations of foetal heart rate. Foetuses with antepartum decelerations had statistically significantly increased incidence of intrapartum decelerations, caesarean section due to intrapartum foetal distress, cord complications and small for gestational age infants. More so with decreased amniotic fluid index (p < 0.001). Low 5 minute apgar score was also significantly increased (p < 0.05). Prediction of foetal compromise might be done by spontaneous decelerations in reactive non-stress tests and with an amniotic fluid index < or = 5 cm.

Adult↗

PubMed1976

Fetal heart deceleration patterns in relation to asphyxia and weight-gestational age percentile of the fetus.

The relation between fetal heart rate deceleration patterns and fetal asphyxia and the weight-gestational age percentile characteristics of the fetus has been reviewed from data obtained from 533 patients monitored during the intrapartum period. There is a significant relation between the frequency of total and late decelerations and fetal asphyxia, again confirming this as a useful criterion in the identification of fetal asphyxia. There is a significant relation between decreasing weight-gestational age percentile of the fetus and increasing frequency of total and late decelerations, identifying this fetal characteristic as another variable which will influence fetal heart rate deceleration patterns. The appreciation of the effect of this variable is useful in the interpretation of the fetal heart rate record during the intrapartum period.

Birth Weight↗

PubMed1992

Amniotic fluid index and prolonged antepartum fetal heart rate decelerations.

Both prolonged fetal heart rate (FHR) decelerations and decreased amounts of amniotic fluid (AF) have been associated with adverse fetal outcome. To determine whether adverse outcome could be predicted by a quantitative assessment of AF in patients with prolonged FHR decelerations, we identified 97 consecutive pregnancies found during antepartum testing to have prolonged FHR decelerations. A four-quadrant AF index was measured concurrently in 92 of these 97 patients. Women with an AF index less than 2 cm had operative intervention for fetal distress in seven of 11 cases (64%), compared with 17 of 81 (21%) who had an index of 2 cm or more (P = .005). We conclude that in patients with a prolonged FHR deceleration during antepartum testing, the need for operative intervention for fetal distress is increased when oligohydramnios is present.

Amniotic Fluid↗

PubMed1991

[Pathogenesis of deceleration in the prenatal period].

Comprehensive examination, making use of cardiotocography, dopplerometry, and doppler echocardiography, was carried out to disclose the contribution of fetal hemodynamic disorders to the pathogenesis of antenatal deceleration in 69 pregnant women. Disorders of both intracardiac fetal hemodynamics and of the fetoplacental circulation were revealed in all the cases with deceleration. Therefore, circulatory disorders underlie the pathogenesis of decelerations. The development of decelerations is related to the progressive deterioration of fetoplacental circulation and, specifically, to marked changes in the intracardiac hemodynamics in conditions of augmenting peripheral vascular resistance and hypoxia of the fetus.

Adult↗

PubMed1989

Clinical associations of variable decelerations during reactive nonstress tests.

Six hundred ninety-three patients at or beyond 30 weeks' gestation with reactive nonstress tests (NSTs) were divided into groups based on the occurrence of variable decelerations of 15 seconds or more in duration and of 20 or more beats per minute in severity. Ultrasound examination within a month of testing showed no increases in nuchal cord localization or decreased amniotic fluid volumes in a subgroup of 181 patients. Fetuses with antepartum variable decelerations were more likely to demonstrate similar decelerations in labor (P less than .001), to undergo operative delivery for a diagnosis of "distress" (P less than .05), to require intensive care nursery admission (P less than .01), and to be small for gestational age (P less than .01). No significant differences were noted in frequency of nuchal or other cord entanglements, overall cesarean section rate, or low pH or Apgar score values. We conclude that variable decelerations in the absence of other alarming NST findings may aid in identifying patients at risk for adverse perinatal occurrences, although factors other than nuchal cord placement or oligohydramnios may be responsible.

Amniotic Fluid↗

PubMed1987

[Semi-quantitative evaluation of the intrapartum variable deceleration of the FHR pattern and its association with umbilical cord blood gas analysis].

Variable daceleration of FHR combined with no other abnormal pattern was semi-quantitatively evaluated to establish the diagnostic value of variable deceleration for fetal distress. FHR charts of 55 low risk vaginal deliveries by direct monitoring were analysed and the SDA (Sum of Dip Area) was calculated using the following equation: SDA = sigma Duration of dip (sec.) X Amplitude of dip (bpm.) X 10(-2) and correlation between SDA and umbilical cord blood gas analysis was obtained. A significant correlation was observed between SDA during labor (from 5 cm cervical dilation to delivery) and cord blood gas data. pHuv:r = -0.445 (p less than 0.005), PO2uv:r = -0.358 (p less than 0.01), BEuv:r = -0.538 (p less than 0.001), pHua:r = -0.441 (p less than 0.005), BEua:r = -0.463 (p less than 0.001). In 14 cases which showed prolonged deceleration (PD:more than 120 sec. in duration and below 100 bpm. in dip), excellent correlation was observed between the SDA of PD and pHuv:pHuv = 7.425-7.74 X 10(-4) SDA of PD (r = -0.756, p less than 0.005), whereas in 21 cases with severe variable deceleration (SVD:more than 60 sec. and recovered within 120 sec. in duration or below 60 bpm. in dip) no significant correlation was seen between the SDA of SVD and pHuv. These results suggest that the SDA value is helpful in evaluating variable deceleration during labor.

Female↗

PubMed1981

Prolonged end-stage fetal heart rate deceleration: a reanalysis.

In an earlier publication we reported on 18 patients who had what was described as prolonged fetal heart rate (FHR) deceleration in the second stage of labor and who had uniformly good outcome. It was believed that the reason for the good outcome was early diagnosis and rapid delivery when the FHR deceleration did not improve by the time the patient entered the delivery room. We have continued to handle this type of deceleration pattern in a similar fashion with good results, but 18 additional cases of prolonged end-stage FHR deceleration associated with a poor outcome are reported along with 1 case of intrauterine demise. Physicians who use the fetal monitor need to be aware of this potentially ominous FHR pattern.

Apgar Score↗

PubMed1981

Variable decelerations of the fetal heart rate during antenatal monitoring.

Variable decelerations were observed in only 52 (0,75%) of 4 509 patients in whom the fetal heart rate was monitored antenatally. In 14 patients fetal monitoring was performed less than 1 week before the test with variable decelerations. The results of 9 of these tests were normal. Tests were repeated within 1 week in 16 patients; normal results were seen in 11 of these. Fetal movements and acceleration patterns of the fetal heart rate occurred in 54% and 23% of patients respectively. The interval between testing and delivery ranged from 0 to 98 days, with a mean of 14 days, and there were no intra-uterine deaths. Fetal distress during labour was rare. Fetal outcome was favourable in only 4 of the 7 cases in which variable decelerations were complicated by reduced beat-to-beat variability. Variable decelerations during the antepartum period therefore do not necessarily indicate a complicated labour.

Female↗

PubMed1996

Implications of prolonged fetal heart rate deceleration during the second stage of labor.

In order to evaluate the neonatal outcomes of infants who had prolonged fetal heart rate (FHR) deceleration during the second stage of labor, the neonatal outcomes of 24 infants born after vaginal delivery at 37 to 42 weeks of gestation with prolonged FHR deceleration during the second stage of labor were compared with the outcomes of 28 infants of a similar gestational age who had normal FHR patterns. No differences in the Apgar scores, mean umbilical PaCO2, PaO2, HCO3- or base deficit values were observed between the two groups, but the mean pH values differed significantly. The occurrences of a 1-minute Apgar score < 7, umbilical arterial pH < 7.20, presence of meconium and admission to the neonatal intensive care unit were higher in the study group, but were not significantly different. None of the 24 infants with prolonged FHR deceleration experienced birth trauma, meconium aspiration, neonatal seizure or neonatal death, but three were found to have congenital heart disease. We conclude that prolonged FHR deceleration during the second stage of labor without FHR abnormalities during the first stage of labor is not always associated with an adverse neonatal outcome and does not mandate the need for surgical or immediate vaginal delivery. Their appearance on FHR tracings requires the implementation of additional methods to assess fetal well-being and also to diagnose fetal distress.

Adult↗

PubMed2003

In vivo anterior cruciate ligament strain behaviour during a rapid deceleration movement: case report.

The mechanism of anterior cruciate ligament (ACL) injury is still unclear. To gain this insight, knowledge of the mechanical behaviour of the healthy ACL during activities that may stress the ligament must be investigated in vivo. The goal of this research was to measure ACL strain in vivo during rapid deceleration, a sport type movement that has been previously shown to precede injuries to the ACL in healthy subjects. A young male subject with no previous knee joint injuries volunteered after informed consent. The strain gauge device (DVRT) was calibrated and surgically implanted in the antero-medial band of the intact ACL. The subject was then transported to the lab for data collection. The zero strain position of the ACL was determined using the slack-taut technique. The subject hopped as quickly as possible from a distance of 1.5 m to the target, an X taped at the centre of a force plate, landing with the instrumented left leg and stopping in the landed position. The entire collection window was five seconds at 1000 Hz. A total of three rapid deceleration trials were collected and averaged over the hop cycle. The slack-taut test was then repeated to ensure proper operation of the DVRT and the reliability of the results. The results showed an average peak strain of the ACL during the instrumented Lachman test of 2.00+/-0.17%. The average peak strain of the ACL during the rapid deceleration task was 5.47+/-0.28%. The data indicate that the RD task caused an increase in peak ACL strain that is much higher than during the instrumented Lachman test, and that the strain begins to increase during the flight phase, prior to landing, and reaches a peak that corresponds to the peak ground reaction force. This technique may be used in further sport-specific movements to gain insight into movement patterns associated with ACL injury mechanisms.

Adult↗

PubMed1985

Effects of deceleration on the humoral antibody response in rats.

The purpose of this experiment was to determine the effects of hyper-gravity (hyper-G) followed by a return to normal gravity (deceleration) on the immune system of rats. Hyper-G was simulated by chronic centrifugation. Eighteen 35-d-old male rats were divided into three groups of six rats each. Two groups were exposed to 2.1 G and 3.1 G, respectively, for 28 d. The third group served as 1.0 G controls. Rats were removed from the centrifuge on day 29. All rats were immunized with sheep red blood cells (SRBC) on days 29, 42, and 57; rats were bled on days 36, 47, and 62. Hematocrits and anti-SRBC titers were determined each day the rats were bled. White blood cell (WBC) counts were determined on day 47. On day 63, all rats were sacrificed and organ:body mass ratios obtained for a number of organs. Centrifuged rats ate and gained significantly less. The organ:body mass ratios for the adrenal glands, kidneys, lungs, heart, and thymus were unaffected by deceleration. Although marginally significant (p less than 0.05) decreased organ:body mass ratios were found for the liver and spleen in the 3.1 G group, this effect may not be real, due to the small number of rats used. No significant differences were found in hematocrits, WBC counts, or anti-SRBC titers. These experiments indicate that deceleration does not adversely affect these particular aspects of the immune system. However, they do not preclude the possibility that other aspects of the immune system, such as interferon or complement, may be affected.

Acceleration↗

PubMed1998

Disulfide isomerization within the C-terminus of cobrotoxin decelerates by thiol compounds and trinitrophenylation, but accelerates by modification of carboxyl groups.

A disulfide isomerization at the C-terminus of cobrotoxin occurred spontaneously by dissolving in alkali buffer. Irreversible conversion of cobrotoxin into its isomers was completely achieved within 4 days. The isomerization reaction was decelerated by thiol compounds including GSSG, GSH, cystamine, and cysteamine in a pseudo-first-order kinetic, and GSSG was the most effective one among the thiol compounds used. Moreover, the oxidized thiol compounds were always superior to reduced ones in decreasing the rate of disulfide interchange. To further assess the intrinsic elements essential for the occurrence of disulfide isomerization of cobrotoxin, the toxin molecule was subjected to modification on its Arg, Lys, Trp, Tyr, and carboxyl groups. In sharp contrast to other modified derivatives, the isomerization reaction was decelerated by trinitrophenylation on Lys-26, Lys-27, and Lys-47, whereas it was rapidly completed after modification of carboxyl groups. Neither chemical modification nor the toxin's conformation affected the irreversibility of isomerization reaction. Thus, the observed change in the rate of disulfide isomerization reflects the involvement of Lys residues and carboxyl groups in this reaction. Although thiol compounds further decelerated the conversion of trinitrophenylated cobrotoxin into its isomers, they did not exert a notable effect on the isomerization of carboxyl groups-modified derivative. These results clearly indicate that disulfide isomerization of cobrotoxin is, in part, driven by the positively charged Lys residues at positions 26, 27, and 47 of the toxin molecule, and that the thiol compounds are coordinated with the negatively charged groups of cobrotoxin to exert their inhibitory action.

Animals↗

PubMed1978

Fetal movements associated with fetal heart rate accelerations and decelerations.

In normal pregnant women, the relationship between the FHR and fetal movements (FM) was evaluated during 1,541 consecutive observed FM of at least 1 second's duration. Two observed FHR changes were: (1) accelerations and (2) accelerations followed by decelerations. An acceleration in FHR was observed in association with 91.2 per cent of all FM of 1 to 3 seconds' duration and with 99.8 per cent of FM of longer than 3 seconds' duration. FM were associated with an acceleration followed by a deceleration 66.7 per cent of the time. FM lasting longer than 1 second and associated with neither accelerations nor decelerations were seen 1.8 per cent of the time.

Female↗

PubMed1980

Fetal oxygen consumption and mechanisms of heart rate response during artificially produced late decelerations of fetal heart rate in sheep.

Delayed decelerations of fetal heart rate were produced by abruptly decreasing uterine blood flow to zero for 20 seconds in chronically instrumented, normoxic sheep. Fetal O2 consumption, O2 content, and O2 tension in umbilical blood decreased significantly before the decline in heart rate. Fetal arterial blood pressure did not change significantly. Complete vagal blockade abolished the late deceleration and uncovered a late acceleration, which in turn was eliminated by total beta-adrenergic blockade. We conclude that these late decelerations in normoxic sheep are vagally mediated and due to chemoreceptor rather than baroreceptor activity.

Animals↗