Temporal conditioning of heart rate responses in newborn infants.

Evaluated temporal heart rate conditioning in 32 newborns (16 experimental and 16 control) by examining responses to the UCS, in anticipation of the UCS, and in its absence. There was weak evidence, only in the females, of a conditioned anticipatory deceleration immediately before the UCS. Response differences between the experimental and control groups following the UCS and in its absence were also found. (19 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Heart rate variability and newborn heart rate responses to illumination changes.

Investigated heart rate (HR) response patterns to the onset and offset of a 30-sec increase in illumination in 16 human newborns. Ss were divided into 2 groups based on a measure of pretrial HR variability. Only Ss with the high pretrial HR variability responded significantly to the change in stimulation. The response to onset was characterized by a significant quartic trend containing both decelerative and accelerative components. The response to offset only approached significance and had a pattern similar to the onset response. Although the occurrence of systematic response patterns was related to the level of pretrial HR variability, this measure of autonomic lability may have been related to influences associated with delivery and not to stable individual differences. (16 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Peripheral stimulus localization by infants: Attention, age, and individual differences in heart rate variability.

The effect of attention to a focal stimulus on 3- to 6-month-old infants' peripheral stimulus localization was examined. Fixation was engaged on a central visual stimulus, and a stimulus was presented in the periphery after discrete time intervals (0 to 12 s) or until changes in heart rate (HR) occurred. Peripheral stimulus localization occurred less frequently when a significant HR deceleration had occurred (sustained attention) than when HR had returned to its prestimulus level (attention termination). A signal detection analysis showed that response bias was altered by attention and that during inattention infants with high HR variability were more likely to shift fixation away from the central stimulus independently of the presence of the peripheral stimulus. These data suggest that infant attention affects decision processes for continuing focal stimulus fixation rather than peripheral stimulus discriminability. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Relationships between heart rate variability and antiarrhythmic effects of hydroquinidine

We report 2 elderly patients who present with a relatively acute onset of a severe symmetrical synovitis affecting the flexor digitorum tendon sheaths and wrist joints with pitting edema of the dorsum of both hands. These patients were seronegative for rheumatoid factor and responded to treatment with low dose predonisone (10 mg daily) without relapse. These presenting features were closely linked with the RS3PE syndrome originally described by McCarty.     

Development of heart rate in newborn infants during quiet sleep

The small number of investigations of the development of heart rhythm during the first half year of life provide only rough ideas regarding the maturation of heart rate control. In the present study, in 10 newborns, ECG and respiratory effort were recorded in 13 sessions from birth up to the sixth month. The total power (TP), power in the low (LF) and high frequency range (HF), and the ratio LF/HF were used from the heart rate power spectra. All parameters reveal no linear developmental patterns: TP, LF, and HF increase during the first days to a maximum, then decrease subsequently and remain low until the second month. TP and HF increase between the second and sixth month. LF/HF increases up to the second month followed by a decrease down to the sixth month. The developmental courses of TP, HF and LF/HF correlate with the course of breathing rate (BR), whereby high BR is associated with low HF and TP. The results hint at a maturated cardiorespiratory system.     

Heart rate variability in 1-day-old infants born at 4330 m altitude

BACKGROUND: Rates of low-birth-weight (LBW) infants are similar between Latina and white women, an epidemiologic paradox. However, few studies have analyzed the relationship between ethnicity, Latino subgroup, confounding variables, and LBW. METHODS: We analyzed 395070 singleton livebirths to Latina and non-Latina white women in California during 1992. Multivariate logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs) for the risks due to Latino ethnicity and Latino subgroup for very LBW (VLBW, 500-1499 g) and moderately LBW (MLBW, 1500-2499 g) outcomes. RESULTS: Latina and white women had similar unadjusted rates of VLBW (0.7% vs. 0.6%) and MLBW infants (3.7% vs. 3.4%). After adjusting for maternal age, education, birthplace, marital status, parity, tobacco use, use of prenatal care, infant sex, and gestational age, there was no difference in the odds of VLBW infants between Latina and white women (OR, 0.93 [95% CI, 0.81-1.071). Latina women had minimally elevated odds of MLBW infants (OR, 1.06 [95% CI, 1.01-1.11]) compared with white women. By Latino subgroup, there was no difference in the adjusted odds of VLBW infants among Central and South American, Cuban, Mexican, Puerto Rican, and white women. The adjusted odds of MLBW infants were elevated among Central and South American (OR, 1.14 [95% CI, 1.05-1.25]) and Puerto Rican women (OR, 1.41 [95% CI, 1.12-1.78]), relative to white women. CONCLUSIONS: The epidemiologic paradox of LBW in Latinos is valid. New conceptual models are needed to identify Latina women who are at risk for adverse pregnancy outcomes.     

Heart rate variability and heart rate in healthy volunteers. Is the female autonomic nervous system cardioprotective?

AIMS: Heart rate variability has been proposed as an indicator of cardiovascular health. Since women have a lower cardiovascular risk, we hypothesized that there are gender differences in autonomic modulation. METHODS AND RESULTS: In 276 healthy subjects (135 women, 141 men) between 18 and 71 years of age, 24 h heart rate and heart rate variability were determined. All heart rate variability parameters, except for pNN50 and high frequency power, were higher in men. After adjustment for heart rate, we obtained gender differences for: the standard deviation (P=0.049), the standard deviation of the 5 min average (P=0.047), low frequency power (absolute values, P=0.002; normalized units, P<0.001) and ratio low frequency/high frequency (P<0.001). There were no significant gender differences in heart rate variability parameters denoting vagal modulation. Gender differences were confined to age categories of less than 40 years of age. The majority of heart rate variability parameters decreased with age. Only in men, was a higher body mass index associated with a higher heart rate and with lower heart rate variability parameters (P<0.001). CONCLUSION: Cardiac autonomic modulation as determined by heart rate variability, is significantly lower in healthy women compared to healthy men. We hypothesize that this apparently paradoxical finding may be explained by lower sympathetic activity (low frequency power) in women. This may provide protection against arrhythmias and against the development of coronary heart disease.     

Heart rate variability index in congestive heart failure: relation to clinical variables and prognosis

AIM: To evaluate the clinical and prognostic value of the heart rate variability index in patients with congestive heart failure. METHODS: Sixty-four patients with chronic congestive heart failure and sinus rhythm underwent clinical assessment, 24-h ambulatory electrocardiography and echocardiography. Patients were followed for 6 to 30 months. Cardiac death or heart transplantation constituted the primary end-point of the study. RESULTS: The heart rate variability index was related to left ventricular ejection fraction (r=0.29, P=0.02) and New York Heart Association class (P=0.01). Patients with a restrictive left ventricular filling pattern had a lower heart rate variability index compared to patients with a non-restrictive pattern (26+/-11 vs 33+/-9 units, P=0.01). Patients who died (n=11) or underwent heart transplantation (n=4) had a lower heart rate variability index compared to survivors (21+/-10 vs 33+/-9 units, P<0.0001). In multivariate survival analysis, a reduced heart rate variability index was related to survival independent of parameters of left ventricular function. CONCLUSION: The heart rate variability index provides independent information on clinical status and prognosis in patients with chronic congestive heart failure.     

Heart rate variability: significance and clinic application

In vitro effects of two bioactive forms of pituitary adenylate cyclase activating polypeptide (PACAP): PACAP-38 and PACAP-27 were studied on rabbit vascular and non-vascular smooth muscle. Segments of the ovarian artery and muscle strips from the fallopian tube were used. Two series of experiments were performed on vessels: the dose-response relationship of PACAP-38 (10(-10)-10(-7) M) was established on noradrenaline- (NA, 10(-6) M) contracted vessels. In the other set of experiments the contractile effect of 10(-8)-10(-4) M NA added cumulatively, was studied on arterial segments incubated with PACAP-38 (10(-7) M), PACAP-27 (10(-7) M) or VIP (10(-7) M). The effect of PACAP-38, PACAP-27 and VIP (10(-10)-10(-6) M) was investigated on spontaneously contracting smooth muscle of the fallopian tube. Longitudinally as well as transversally cut specimens were investigated. PACAP-38 produced a significant dose-related relaxation on the NA-precontracted vessels. However, pre-incubation of the vessels with 10(-7) M PACAP-38, PACAP-27 and vaso active intestinal polypeptide (VIP) did not induce a general rightward shift of the NA concentration-response curves, although a tendency to inhibition in the low-dose interval was observed. The peptides caused a significant, dose-dependent inhibition of both frequency and amplitude on the fallopian tube smooth muscle activity. The effects of the three peptides on longitudinally as well as transversally cut specimens were alike.     

Heart rate variability, the autonomic nervous system, and neuroeconomic experiments.

Measuring the activity of the autonomic nervous system may yield insights into individual stress levels. One small, nonintrusive instrument for collecting such data is a high-resolution heart rate monitor that allows measurement of heart rate variability (HRV). This complements brain-scanning methods and increases the number of participants that can be studied simultaneously. Combining HRV data with recorded data on the decisions made in experimental games throws light on how different individuals react in (economic) decision-making situations. This article therefore introduces the HRV measurement method and, using data from an ultimatum bargaining experiment in a laboratory environment, illustrates its application in experimental economic research. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Metaiodobenzylguanidine and heart rate variability in heart failure

It is assumed that the low-frequency power (LF) of heart rate variability (HRV) increases with progress of congestive heart failure (CHF), therefore positively correlating with cardiac 123I-metaiodobenzylguanidine (MIBG) washout. It is demonstrated here that HRV, including normalized LF, correlated inversely with MIBG washout and positively with the ratio of heart-to-mediastinum MIBG activity in controls and CHF patients, whereas these correlations were not observed within CHF patients. Thus MIBG washout may increase and HRV including normalized LF may decrease with CHF, although the HRV and MIBG measures may not similarly change in proportion to the severity of the cardiac autonomic dysfunction in CHF.     

Heart rate variability and preoperative anxiety

Power spectral analysis of heart rate variability has been used to gain some understanding of the activity of the autonomic nervous system. In this study various indices of heart rate variability were related to the degree of preoperative anxiety experienced by 32 patients presenting for day case surgery. It was found that there was no correlation between anxiety and mean heart rate, or between anxiety and the spectral power in the mid frequency band (0.05-0.15 Hz). However, there was an increase in the relative power of the higher frequency band (0.15-0.5 Hz) with increasing anxiety levels (Spearman correlation r = 0.4034). This suggests that preoperative anxiety may often be associated with a relative vagal predominance in the sympathovagal balance.     

Developmental patterns of heart rate and variability in prematurely-born infants with apnea of prematurity

At equivalent post-conceptional ages, prematurely-born infants have higher heart rates and reduced heart rate variability, relative to full-term neonates. Premature birth might exert long-lasting effects on central and peripheral mechanisms that control cardiovascular activity. We assessed development of heart rate and heart rate variability in symptomatic preterm infants up to 6 months of age. Fifty 6.5-h evening recordings of EKG and breathing were obtained from prematurely-born infants (gestational ages: 24-35 weeks). Cardiac R-R intervals were captured with a resolution of +/- 0.5 msec. One-min epochs were selected from three periods of regular respiration in recordings from premature infants and 72 recordings of full-term infants at comparable post-conceptional ages. Mean heart rate and heart rate variability were determined for each recording. At 40 weeks post-conception, prematurely-born infants with apnea of prematurity showed higher heart rates and reduced heart rate variability than did full-term neonates. These differences between premature and full-term infants persisted throughout the next 6 months in those infants born prior to 30 weeks gestation, and in those infants born at 30-35 weeks who experienced respiratory distress syndrome (RDS) during the neonatal period. The findings suggest that premature delivery, or complications thereof, exerts long-lasting effects on cardiac control.     

Heart rate variability as an assessment of acute rejection after heart transplantation

BACKGROUND: Orthotopic heart transplantation is currently a widely accepted treatment for end-stage heart disease. Early detection and adequate therapy of acute rejection increases the survival rate. Currently, the most reliable technique for the detection of acute cardiac rejection (ACR) is endomyocardial biopsy (EMB), which is an invasive procedure with some intrinsic problems. The purpose of this study was to assess heart rate variability (HRV) as a noninvasive procedure for frequent monitoring of ACR. METHODS: Six consecutive orthotopic cardiac transplant recipients were prospectively recruited into this study. The follow-up periods ranged from seven to 359 days (median; 146 days). A precordial electrocardiograph (ECG) of 288 seconds was recorded at 5:00 PM before the patient underwent EMB. The results from the frequency domain analysis of the ECG signals were evaluated to correlate with the findings from EMB. RESULTS: Of 48 EMBs, 42 (87.5%) showed no evidence of rejection, four showed mild focal ACR (EMB grade 1A), one mild diffuse ACR (1B) and one moderate plurifocal ACR (3A). There was no moderate focal ACR (2), severe diffuse ACR (3B) or severe ACR (4). Correlation between ACR (3A) and a significant increase in HRV with a corresponding 'broad-band' or bell-shaped pattern on the power spectrum was noted. CONCLUSIONS: Our study in consecutive cardiac transplant recipients indicates that the changes in HRV provide clinicians with a new concept for heart transplant monitoring. Further study is needed to verify clinical utility.     

Time, rate, and conditioning.

The authors draw together and develop previous timing models for a broad range of conditioning phenomena to reveal their common conceptual foundations: First, conditioning depends on the learning of the temporal intervals between events and the reciprocals of these intervals, the rates of event occurrence. Second, remembered intervals and rates translate into observed behavior through decision processes whose structure is adapted to noise in the decision variables. The noise and the uncertainties consequent on it have both subjective and objective origins. A third feature of these models is their timescale invariance, which the authors argue is a very important property evident in the available experimental data. This conceptual framework is similar to the psychophysical conceptual framework in which contemporary models of sensory processing are rooted. The authors contrast it with the associative conceptual framework. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Heart rate variability: two eras of investigation

Changes in membrane potential are a regulatory signal for voltage-gated ion channels including the family of Ca2+ channels. This regulatory role includes the voltage-dependent opening, closing, and inactivation of ion channels and the control of drug access and affinity for discrete channels states. Membrane potential is both a short- and long-term regulatory signal controlling the number and function of these voltage-gated channels. Depolarization of neuronal and neurosecretory cells produces down-regulation of L-type voltage-gated Ca2+ channels. These processes are described and their relevance to physiologic and pathologic processes of neuronal development and neuroprotection are indicated.     

Heart rate variability in coronary artery disease

Heart rate variability (HRV) reflects the modulation of cardiac function by autonomic and other physiological systems, and its measurement from ambulatory electrocardiograph (ECG) recordings is a useful method for both clinical and scientific purposes. Heart rate variability can be measured by several linear and non-linear methods, and various methods can give different information on neural and other physiological influences on the heart. Heart rate variability is abnormal in various settings of ischaemic heart disease, and the most important current application of HRV analysis in clinical cardiology is its measurement in postinfarction patients, in whom abnormal HRV indicates an increased risk of cardiac mortality. Future research may expand the clinical utility of HRV measurement to other clinical situations.     

Human operant heart rate conditioning: The importance of individual differences.

Respiratory, somatic-muscular, and CNS responses have all been suggested as possible mediators of operant heart rate changes. A review of studies concerned with each proposed mediator indicates that such responses can mediate heart rate change, but no studies have demonstrated the necessity for such mediation. Current hypotheses concerning mediating variables appear to oversimplify the complex interactions of autonomic and CNS modalities. A review of research on physiological patterns of response during stress, classical conditioning, and avoidance conditioning indicates that there are considerable individual differences in automatic and CNS responses during those tasks. It is suggested that individual differences in physiological responding also occur during operant heart rate conditioning and that E's should utilize such differences in constructing models of events that might mediate operant heart rate changes. (21/2 p ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)