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PubMed1998

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.

Adolescent↗
PubMed1995

Spectral analysis of systolic blood pressure and heart rate after heart transplantation in children.

1. The aim of the study was to examine the short-term variability in blood pressure and heart rate in 19 children who had received heart transplants and in eight normal control children. 2. Blood pressure was determined by a finger arterial pressure device. We examined the power spectra for heart rate and systolic blood pressure in the supine and tilted positions. In addition, we studied the acute changes in blood pressure and heart rate during active standing. 3. In the transplanted children we could distinguish two groups (groups A and B) in whom heart rate variability differed, although in both it was greatly reduced compared with controls (group C). In group A there were no significant fluctuations in the mid-frequency range for heart rate. The gain of the relationship between systolic blood pressure and heart rate was very low and there were virtually no heart rate changes associated with passive tilting. 4. By contrast, in group B transplant patients the heart rate variability, as assessed by standard deviation, was about half that of normal controls. The power spectra attenuation was greater in the high-frequency than in the mid-frequency bands. On passive tilting the latter became enhanced, but not the high-frequency variability. On active standing the tachycardic response was about half that of controls. The findings suggest some reinnervation involving cardiac sympathetic fibres to a greater degree than the fast-responding vagal fibres. 5. In both groups A and B the drop in systolic blood pressure observed early in active standing was about 4-6 times as great as in controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Pressure↗
PubMed1981

Reversibility of abnormal arterial baroreflex control of heart rate in heart failure.

The reversibility of the abnormalities in arterial baroreceptor control of heart rate in heart failure was examined in an experimental model of canine high-output biventricular failure produced by an arteriovenous fistula that could be later surgically corrected by ligation. Marked attenuation of arterial baroreceptor control of heart rate in response to both hypertensive and hypotensive stimuli was seen in this model of heart failure. After surgical correction the heart rate response to a hypertensive stimulus did not return to normal but remained severely blunted for up to 8 mo of follow-up. The lack of reversibility after surgical correction suggests that permanent structural changes in arterial baroreceptors may occur after heart failure of short duration.

Animals↗
PubMed1996

Influence of beliefs about heart rate and actual heart rate on heartbeat counting.

The heartbeat counting task is used widely to assess the ability to perceive cardiac sensations. However, performance on this task may be determined by processes other than sensitivity to cardiac stimuli. Beliefs about the effects of postural and exercise challenges on heart rate were assessed by questionnaire prior to performing the heartbeat counting task, and then actual heart rate was manipulated during the counting task by changes in posture and exercise. On average, counted heart rates were closer to beliefs about heart rate than to actual heart rate. Hierarchical multiple regression analyses indicated that (a) believed heart rates predicted counted heart rates while controlling for actual heart rates and (b) actual heart rates also predicted counted heart rate while controlling for heart rate beliefs. These data suggest that the rate of heartbeat counting is influenced by beliefs about heart rate and by the processing of cardiac sensations.

Adult↗
PubMed1999

Dissociating beliefs about heart rates and actual heart rates in patients with cardiac pacemakers.

Performance on heartbeat counting tasks is usually interpreted in terms of cardiac sensitivity. We tested the hypothesis that heartbeat counting is influenced by beliefs about heart rates by dissociating beliefs about heart rates and actual heart rates. In a within-subjects design, heart rates of 50 patients with cardiac pacemakers were set to a low (50 bpm), medium (75 bpm), or high (110 bpm) pacing rate unknown to the patients via remote control while they performed a heartbeat tracking task. Results showed that patients' heartbeat counting did not follow the shifts in their actual heart rates adequately, although their overall performance was comparable to that of young and healthy control participants. As a result, tracking scores decreased significantly in the high pacing rate condition where beliefs about heart rates and actual heart rates were most extremely dissociated. The findings suggest that tracking scores reflect beliefs about heart rates rather than cardiac sensitivity.

Adult↗
PubMed1999

Association of heart rate and heart-rate variability with scores on the emotion profile index in patients with acute coronary heart disease.

We investigated the link between the eight basic emotions named by Plutchik and heart rate, heart-rate variability in the 114 patients, 86 men and 28 women (M = 53.8 yr., SD = 8.0) with acute coronary heart disease during the initial 24-hr. stay in the coronary care unit and again at hospital discharge. Variability in heart rate was significantly positively associated with scores on Trust (the emotional state acceptance) at hospital admission and discharge in the patients with unstable angina and non-Q-wave infarction, on Aggression in the patients with unstable angina at hospital discharge and at hospital admission in the patients with non-Q-wave infarction. There was inverse relation on Timid (the emotional state fear) and Gregarious (joy) at hospital admission and on Distrust (disgust or rejection), Depressed (sadness), and Dyscontrol (impulsiveness) at hospital discharge in the patient with non-Q-wave infarction. There was no significant association between heart-rate variability and the scores on the Emotion Profile Index in the patients with anterior and posterior myocardial infarction. There was no statistically significant association between heart rate and scores on the Emotion Profile Index in the patients with acute coronary disease at hospital admission and discharge. Our results suggest psychological interventions that enhance emotional states represented by the Trust and Aggression scales and minimize those represented by Depressed, Dyscontrol, Timid, and Distrust scales could have a beneficial effect on cardiovascular function in the patients with unstable angina and non-Q-wave infarction in a hospital setting.

Acute Disease↗
PubMed1999

Acute and chronic effects of a hypocaloric diet on 24-hour blood pressure, heart rate and heart-rate variability in mildly-to-moderately obese patients with essential hypertension.

We examined the acute and chronic effects of a nutritionally balanced, moderately hypocaloric diet on 24-hour ambulatory blood pressure, heart rate and heart-rate variability in mildly-to-moderately obese patients with essential hypertension. We enrolled 16 obese patients with essential hypertension [age: 51-76 years, body mass index (BMI): 26-32 kg/m2]. For the initial week, a standard diet of 2,000 kcal/day was given, followed by a 3-week of a hypocaloric diet of 850 kcal/day. In the last period of the standard diet and in the first and the last periods of the hypocaloric diet, each subject's 24-hour ambulatory blood pressure, heart rate and R-R intervals of the electrocardiogram were recorded, and electrolytes and catecholamines in 24-hour urine samples were also measured. A power spectral analysis of the heart-rate variability was performed over a 24-hour period based on the autoregressive method. The subjects lost 3.7+/-0.3 kg (mean +/- s.e.m.) of body weight during the 3-week hypocaloric diet period. The 24-hour blood pressure did not differ between the last period of the standard diet and the first period of the hypocaloric diet; however, it showed a significant reduction after 3 weeks of the hypocaloric diet. The decrease in the 24-hour blood pressure during the study period was 10.5+/-1.5 mm Hg systole and 4.3+/-1.8 mm Hg diastole. In contrast, the 24-hour heart rate was significantly reduced in the first period of the hypocaloric diet, although the body weight and blood pressure did not change, and the rate was maintained even in the last period of the hypocaloric diet. The decrease in the 24-hour heart rate during the study period was 2.8+/-0.9 beats per minute. The hypocaloric diet did not change any autonomic indices obtained from a power spectral analysis of the heart-rate variability. In conclusion, different responses to a hypocaloric diet were observed between the blood pressure and the heart rate in obese hypertensive patients. The changes in power spectral parameters of the heart-rate variability were less apparent than those found with the blood pressure or the heart rate.

Blood Pressure↗
PubMed2000

An examination of the relationship between resting heart rate variability and heart rate reactivity to a mental arithmetic stressor.

Resting heart rate variability can be an index of sympathetic or parasympathetic dominance, according to the frequency of the variability studied. Sympathetic dominance of this system has been linked to increased risk of cardiovascular disease (CVD). Similarly, rapid and dramatic increases in heart rate reactivity to a stressor task have also been suggested as indicating increased risk of CVD via atherogenesis. Although both of these variables have been related to the development of cardiovascular disease, and both may be related to increased sympathetic activity or parasympathetic withdrawal, most research studies have tended to focus on either variable independently of the other. In order to investigate whether these two indices of stressor reactivity were related in relatively young and healthy subjects, resting heart rate variability data were collected from 80 volunteers for 20 minutes. In addition, heart rate reactivity data were collected during a 2-minute mental arithmetic stressor, which has been previously shown to induce significant increases in heart rate. After classifying subjects according to whether their heart rate variability data were above or below the mean for their gender, heart rate reactivity data were examined via MANOVA to detect significant differences between subject groups. Females showed significant effects, and males showed nonsignificant trends, but these two sets of data were in different directions, suggesting that gender may be a confounding factor in the relationship between heart rate reactivity and heart rate variability.

Adolescent↗
PubMed1994

[Pharmacological control of heart rate].

Heart rate, an important risk factor of coronary mortality, is highly correlated with numerous anthropometric and biochemical variables: height, body weight and hyperlipidemia; it varies, furthermore, with smoking and age and can be modified during pharmacotherapy for hypertension. From meta-analyses on different cardiovascular treatments, given after coronary events, only the efficacy of drugs significantly reducing heart rate is borne out (beta-blockers with sympathomimetic activity, or calcium-antagonists with a prevalent vasodilatory action do not provide a protective effect). Among calcium-antagonists, while the mechanism of action is similar at the cell level (delay of opening of voltage-operated slow channels), the distribution of activity within the vascular system varies markedly. Dihydropyridines (e.g., nifedipine) exert a dominant peripheral effect, with consequent vasodilation, whereas phenylalkylamines (verapamil) have both peripheral vasorelaxant and cardiac negative chronotropic activity, because of a reduced sinus node action potential. A relative tachycardia may occur with dihydropyridines, secondary to the activation of baroreceptors; the compensatory heart mechanism operated by verapamil antagonizes this reflex tachycardia. The activity of verapamil on the atrioventricular conduction allows both a slowing of functional recovery of the channel in hyperexcitable conditions (supraventricular tachycardia), and, moreover, increased diastolic intervals, with consequent improvement of coronary flow. New molecules can selectively reduce the sinus node activity without exerting other effects (hypotensive, anti-arrhythmic). From a comparative evaluation of these molecules with verapamil, it clearly emerges how this latter can provide a more acceptable pharmacodynamic profile, both for the hypotensive activity, and also for the control of reflex tachycardia, with a consequently improvement of coronary flow.

Adrenergic beta-Antagonists↗
PubMed1989

Does fetal heart rate predict subsequent heart rate in childhood?

An investigation to determine whether there is any relationship between extremes of fetal heart rate during labour and subsequent heart rate at the age of 10 was carried out using data from the 1970 cohort of British Births. In 11,000 nationally representative children it was found that low fetal heart rate (below 120 beats/min) was associated with a heart rate at age 10 which was significantly lower than in those children whose fetal heart rate had remained between 120 and 160 beats/min (P less than 0.01). This relationship could not be explained by fetal asphyxiation, maternal antenatal hypotension or the method of pain relief during labour. There was no equivalent relationship with high fetal heart rate during labour. This could imply that some fetuses with low heart rates are not exhibiting fetal distress but have an inherent tendency to relatively slow heart rates.

Child↗
PubMed2003

Predicting metabolic rate from heart rate in juvenile Steller sea lions Eumetopias jubatus.

The validity of using heart rate to estimate energy expenditure in free-ranging Steller sea lions Eumetopias jubatus was investigated by establishing whether there is a relationship between heart rate (fH) and oxygen consumption rate ((O(2))) in captive sea lions while swimming and resting. Four trained Steller sea lions (2 males and 2 females; mass 87.4-194.4 kg; age 16 months-3 years) were each equipped with a datalogger and two dorsal subcutaneous electrodes to record electrocardiograms from which fH was calculated. (O(2)) (measured using open-circuit respirometry) was simultaneously recorded while the previously fasted animals were at rest within an enclosed dry metabolic chamber or while they swam in an enclosed swim mill against water currents of various speeds (0-1.5 m s(-1)). The mean regression equation describing the relationship between fH (beats min(-1)) and (O(2)) (ml h(-1) kg(-0.60)) for all four animals was (O(2)) =(71.3f(H)+/-4.3)-(1138.5+/-369.6) (means +/- S.E.M.) (r(2)=0.69, P<0.01). The relationship demonstrated between fH and (O(2)) while fasting suggests that heart rate can potentially be used to monitor energy consumption in free-ranging Steller sea lions. However, a short-term feeding experiment revealed no significant increase in heart rate following a 6 kg or 12 kg meal to match the observed increase in rate of oxygen consumption. This suggests that heart rate may not accurately reflect energy consumption during digestion events. Additional research should be conducted to further elucidate how the relationship between heart rate and oxygen consumption is affected by such factors as digestive state, stress and age.

Animals↗
PubMed1993

Alterations of heart rate and of heart rate variability after radiofrequency catheter ablation of supraventricular tachycardia. Delineation of parasympathetic pathways in the human heart.

BACKGROUND: Persistent inappropriate sinus tachycardia has been reported as a complication after radiofrequency (RF) ablation of the fast atrioventricular (AV) nodal pathway. The purpose of this study was to evaluate the prevalence of this complication and its mechanism using heart rate variability analysis. METHODS AND RESULTS: Time and frequency domain analysis of heart rate was performed in the electrophysiology laboratory immediately before and immediately after RF ablation in 64 patients with supraventricular tachycardia. Ablation targets in these 64 patients included the fast AV nodal pathway (n = 3), the slow AV nodal pathway (n = 14), a posteroseptal accessory pathway (n = 23), and a left lateral accessory pathway (n = 24). A control group of 21 patients undergoing diagnostic study but not ablation underwent identical analysis immediately before and at the conclusion of their procedure. Patients undergoing ablation also had time and frequency domain analysis performed on ambulatory 24-hour Holter tapes recorded before ablation and at 1 day, 1 month, and 6 months after ablation. Compared with preablation values, time domain analysis immediately after ablation revealed a significant increase in mean heart rate and significant reductions in heart rate variability expressed as SD, MSSD, and PNN50 in patients undergoing AV nodal modification or posteroseptal accessory pathway ablation. Frequency domain analysis revealed marked attenuation of high frequency (0.15 to 0.40 Hz) components, indicating parasympathetic denervation. These acute changes were not seen after ablation of left lateral accessory pathways or after diagnostic study without ablation. Time and frequency domain analysis of 24-hour ambulatory Holter monitors performed serially after ablation revealed resolution of abnormalities of heart rate and of heart rate variability 1 to 6 months after ablation, with reappearance of the high frequency parasympathetic component suggestive of reinnervation. CONCLUSIONS: RF ablation in the anterior, mid, and posterior regions of the low interatrial septum may disrupt preganglionic or postganglionic parasympathetic fibers located in these regions that are destined to innervate the sinus node. Such fibers become more scarce along the left AV groove with increasing distance from the posteroseptal space. Parasympathetic denervation may be one mechanism for persistent inappropriate sinus tachycardia after RF ablation.

Adult↗
PubMed1996

Neostigmine decreases heart rate in heart transplant patients.

PURPOSE: This study evaluated the effect of neostigmine on heart rate in cardiac transplant patients. METHODS: Neostigmine (2.5-50 micrograms.kg-1) was administered to ASA 1 or 2 patients with normally innervated hearts (controls), and to patients who had undergone recent (< six months before study) or remote (> six months before study) cardiac transplantation. RESULTS: Baseline heart rate was 66 +/- 3 beats.min-1 in controls (n = 10, mean +/- SEM), which was slower than that observed in recently (95 +/- 4 beats.min-1, n = 15, P < 0.001) and in remotely (88 +/- 3 beats.min-1, n = 16, P < 0.001) transplanted patients. Neostigmine produced a dose-dependent decrease in heart rate in all patients. Controls were the most sensitive to neostigmine, with a 10% decrease in heart rate produced by an estimated dose of 5.0 +/- 1.0 micrograms.kg-1. The recently transplanted group was the least sensitive, with the maximum dose producing only an 8.3 +/- 0.9% reduction. The response to neostigmine of the remotely transplanted patients was variable. The estimated dose to produce a 10% decrease in heart rate in this group was 24 +/- 6 micrograms.kg-1 which was greater than that for controls (P = 0.008). Administration of atropine (1.2 mg) reversed the neostigmine-induced bradycardia in all three groups. Reversal of the bradycardia consisted of a transient peak increase in heart rate in controls to 145 +/- 6% of baseline, a value which was greater than that observed in recent (103 +/- 1%, P < 0.001) and in remote (109 +/- 3%, P < 0.001) transplants. CONCLUSIONS: Neostigmine produces a dose-dependent bradycardia in heart transplant patients. Some remotely transplanted patients may be particularly sensitive to the bradycardic effects of neostigmine.

Cholinesterase Inhibitors↗
PubMed1992

Force-frequency relationship, contraction duration and recirculating fraction of calcium in postnatally developing rat heart ventricles: correlation with heart rate.

Heart rates (HR) of awake unrestrained animals, isometric contraction duration and force-frequency relationship of ventricular tissue were determined in adult and postnatally developing rats. Resting HR was lowest in newborns (256 beats min-1), reached maximum at the age of 2.5 weeks (506 beats min-1) and then declined to the level of adult rats (381 beats min-1). Duration of isometric contraction correlated negatively with HR. Time to peak tension (TPT) was 185 ms in newborns but fell rapidly during the first days of post-natal life. Minimum was attained at the age of 2.5 weeks (TPT = 98 ms), followed by a slight prolongation towards adulthood. Recirculating fraction of activator Ca2+ increased parallel with HR, being 6% in newborns, 33% in 11-day-old pre-weanlings, and 87% in adult rats. Similar developmental pattern of the parameters suggests that a post-natal increase in HR and a shortening of contraction duration are closely associated with a shift from extracellular to intracellular source of activator Ca2+. Force-frequency curves were similar at different developmental stages and consisted of three phases; a negative staircase between 0.05 and 1.0 Hz, a positive staircase between 1.0 and 4.0 Hz, and a secondary decline above 4.0 Hz. In adult rats the positive force staircase was weak or absent. Furthermore, our results show that negative staircase is not only a property of adult rat heart but is present, and even more pronounced, in pre-weanling and weanling rat heart. Therefore negative staircase is not solely explained by quantitative changes in the contribution of sarcoplasmic reticulum (SR) to contractile activation, but rather by the mechanisms which regulate loading and/or release of sarcoplasmic reticular Ca2+.

Animals↗
PubMed1993

Analysis of the work rates and heart rates of association football referees.

This study aimed to describe the work-rate profiles of referees during soccer matches and record heart-rate responses during these games. Using video-recordings 14 referees were observed and their heart rates during the games were monitored by short-range radio telemetry. These included 11 football league matches. The exercise intensity was largely submaximal with a change in activity every 6 s. The mean distance covered during the game was 9.44 km; a significant fall in work rate was noted in the second half (P < 0.05). The mean heart rate of 165 beats min-1 did not vary between first and second halves. The work rate and heart rate varied more between individuals than with the importance of the match, but this variation was small. It was considered that refereeing top level soccer places high physiological demands on the official. This has implications for training and fitness assessment.

Adult↗
PubMed2006

The relationship between heart rate recovery and heart rate variability in coronary artery disease.

BACKGROUND: Reduced heart rate recovery (HRR) in coronary artery disease (CAD) is predictive of increased cardiovascular mortality and is related to reduced parasympathetic tonus. OBJECTIVE: To investigate HRR and heart rate variability (HRV) measured at steady state condition and the relationship between these two parameters in CAD. MATERIALS AND METHODS: In our study, we enrolled 33 (28 males, mean age 52.4 +/- 9.6 years) patients with CAD who did not have heart failure, atrial fibrillation, pacemaker, and any disease state that could affect the autonomic functions and 38 age-matched healthy subjects (21 males, mean age 48.3 +/- 7.8 years). All the patients underwent submaximal treadmill exercise testing (Bruce protocol). HRR was calculated by subtracting the heart rate values at the 1st, 2nd, and 3rd minutes of the recovery phase from the peak heart rate (HRR(1), HRR(2), HRR(3)). Before exercise testing, short-term steady state HRV analyses of all subjects were obtained with the time- and frequency-domain methods and were correlated to HRR. For frequency-domain analysis, low-frequency HRV (LF, 0.004-0.15 Hz), high-frequency HRV (HF, 0.15-0.5 Hz), and LF/HF ratio were measured for 5 minutes in the morning. For time-domain analysis, standard deviation of the normal-to-normal NN intervals (SDNN), square root of the mean squared differences of successive N-N intervals (RMSSD), and proportion derived by dividing the number of interval differences of successive N-N intervals greater than 50 ms by the total number of N-N intervals (pNN50) were obtained. Only HRR(3) was used for the correlation analysis. RESULTS: In CAD groups, the HF, an indicator of parasympathetic activation, was significantly reduced, whereas the LF and LF/HF values, which are indicators of sympathetic activity, were increased (P = 0.0001 for each parameter). The time-domain parameters SDNN, RMSSD, and pNN50 were significantly reduced in the patient group (P = 0.0001, P = 0.009, and P = 0.0001, respectively). Similar to the HRV parameters, the HRR(1), HRR(2), and HRR(3) values were significantly reduced in the patient group (P = 0.0001 for each parameter). We observed a significant negative correlation between HRR(3) and LF (r =-0.67, P = 0.0001) and between HRR(3) and LF/HF (r =-0.62, P < 0.0001), while there was a significant positive correlation between HRR(3) and HF, SDNN, RMSSD, and pNN50 (r = 0.69, P = 0.0001; r = 0.41, P = 0.0001; r = 0.31, P = 0.008; and r = 0.44, P = 0.0001). CONCLUSIONS: HRR and HRV are significantly reduced in CAD. The reduction in HRR is parallel to the changes in HRV parameters. HRR, which can be measured easily in the recovery phase of exercise testing, can be used to detect the depression of parasympathetic tonus and to evaluate the basal autonomic balance in this patient group.

Case-Control Studies↗
PubMed2005

Cardiac resynchronization therapy improves heart rate profile and heart rate variability of patients with moderate to severe heart failure.

OBJECTIVES: This study sought to report long-term changes of cardiac autonomic control by continuous, device-based monitoring of the standard deviation of the averages of intrinsic intervals in the 288 five-min segments of a day (SDANN) and of heart rate (HR) profile in heart failure (HF) patients treated with cardiac resynchronization therapy (CRT). BACKGROUND: Data on long-term changes of time-domain parameters of heart rate variability (HRV) and of HR in highly symptomatic HF patients treated with CRT are lacking. METHODS: Stored data were retrieved for 113 HF patients (New York Heart Association functional class III to IV, left ventricular ejection fraction < or =35%, QRS >120 ms) receiving a CRT device capable of continuous assessment of HRV and HR profile. RESULTS: The CRT induced a reduction of minimum HR (from 63 +/- 9 beats/min to 58 +/- 7 beats/min, p < 0.001) and mean HR (from 76 +/- 10 beats/min to 72 +/- 8 beats/min, p < 0.01) and an increase of SDANN (from 69 +/- 23 ms to 93 +/- 27 ms, p < 0.001) at three-month follow-up, which were consistent with improvement of functional capacity and structural changes. Different kinetics were observed among these parameters. The SDANN reached the plateau before minimum HR, and mean HR was the slowest parameter to change. Suboptimal left ventricular lead position was associated with no significant functional and structural improvement as well as no change or even worsening of HRV. The two-year event-free survival rate was significantly lower (62% vs. 94%, p < 0.005) in patients without any SDANN change (Delta change < or =0%) compared with patients who showed an increase in SDANN (Delta change >0%) four weeks after CRT initiation. CONCLUSIONS: Cardiac resynchronization therapy is able to significantly modify the sympathetic-parasympathetic interaction to the heart, as defined by HR profile and HRV. Lack of HRV improvement four weeks after CRT identifies patients at higher risk for major cardiovascular events.

Female↗
PubMed1986

The relationship between antepartum fetal heart rate, intrapartum fetal heart rate, and fetal acid-base status.

The relationships between antepartum baseline fetal heart rate, baseline variability, accelerations, decelerations, and fetal movement and intrapartum fetal heart rate, fetal acid-base assessment at delivery, and Apgar scores 1 and 5 minutes after delivery were studied in 290 mature pregnancies. There was a significant relationship between antepartum and intrapartum baseline fetal heart rate and baseline variability. There was no relationship between antepartum and intrapartum accelerations or decelerations. There was no correlation between antepartum fetal heart rate or fetal movement and fetal acid-base status at delivery or Apgar scores 1 and 5 minutes after delivery. There was a trend for decreased accelerations and decreased fetal movements to be associated with a low Apgar score 1 minute after delivery.

Acid-Base Equilibrium↗