Heart rate variability (HRV) is the temporal variation between sequences of consecutive heartbeats. On a standard electrocardiogram (ECG), the duration between two adjacent R wave peaks is termed the R-R interval. The resulting period between adjacent QRS complexes resulting from sinus node depolarization is termed the N-N (normal-normal) interval, and HRV is the measurement of the variability ...

Heart rate variability (HRV), the quantification of beat-to-beat variability, has been studied as a potential prognostic marker in inflammatory diseases such as sepsis. HRV normally reflects significant levels of variability in homeostasis, which can be lost under stress. Much effort has been placed in interpreting HRV from the perspective of quantitatively understanding how stressors alter HRV...

This study investigated the fluctuations of autonomic nervous activities during the menstrual cycle. Twenty college females were tested for cardiovascular reactivity to mental challenge during both follicular and luteal phases across two menstrual cycles. Power spectral analysis of heart rate variability (HRV) was used to examine the autonomic nervous activities. At baseline, although heart rat...

Personality and heart rate variability (HRV) each are strong predictors of well-being, particularly cardiac health and longevity. The present study compares the changes in HRV during resting state in the Type ̳A‘ and Type ̳B‘ personalities. The personality of subjects is chosen according to Glazer questionnaire. In each of these two groups 30 males were taken. After general interview of these s...

To clarify the role of autonomic nervous functions in cardiovascular adaptation to microgravity, heart rate variability (HRV) and blood pressure variability (BPV) were evaluated during thermoneutral head-out water immersion (HOI) of eight healthy young subjects 23 to 31 yr of age. The very low-frequency (VLF; 0.00-0.04 Hz) component of BPV tended to increase during HOI, whereas the low-frequenc...

The aim of the present research was to analyze autonomic stress response nursing students in a Objective Structured Clinical Evaluation (OSCE). We analyzed, 41 s-year degree (20.1 ± 2.3 years), modifications heart rate variability (HRV) monitor before, during and after 18 different scenarios complete OSCE. Heart mean nurse consistent with an anticipatory anxiety at beginning OSCE, showing sympa...

Endurance-trained athletes have increased heart rate variability (HRV), but it is not known whether exercise training improves the HRV and baroreflex sensitivity (BRS) in sedentary persons. We compared the effects of low- and high-intensity endurance training on resting heart rate, HRV, and BRS. The maximal oxygen uptake and endurance time increased significantly in the high-intensity group com...

BACKGROUND Heart rate variability (HRV) is an established tool for studying cardiac autonomic activity over time, while heart rate turbulence (HRT) is a recent method used to assess autonomic dysfunction. However, there are different autonomic tones at different times of a day. This study aimed to examine the effect of circadian change of autonomic tone on heart rate turbulence and variability,...

Different noninvasive approaches have been developed for risk stratification of patients with myocardial infarction and heart failure with aim to select patients at high risk of sudden cardiac death who might mostly benefit from preventive therapy. Reduced heart rate variability (HRV) was a strong predictor of mortality in myocardial infarction and heart failure in early studies. However, in th...

Physical exercise is associated with parasympathetic withdrawal and increased sympathetic activity resulting in heart rate increase. The rate of post-exercise cardiodeceleration is used as an index of cardiac vagal reactivation. Analysis of heart rate variability (HRV) and complexity can provide useful information about autonomic control of the cardiovascular system. The aim of the present stud...