Spectral analysis of heart rate variability (HRV) may predict the future development of essential hypertension

Analysis of autonomic nervous pattern in hypertension based on short-term heart rate variability

Physiological studies have found that the autonomic nervous system plays an important role in controlling blood pressure values. This paper, based on machine learning approaches, analysed short-term heart rate variability to determine differences in autonomic nervous function between hypertensive patients and normal population. The electrocardiogram (ECG) of hypertensive patients are 137 ECG recordings provided by Smart Health for Assessing the Risk of Events via ECG (SHAREE database). The RR intervals of healthy subjects include the data of 18 subjects from the MIT-BIH Normal Sinus Rhythm Database (nsrdb) and 54 subjects from the Normal Sinus Rhythm RR Interval Database (nsr2db). In this paper, each RR segment includes continuous 500 beats. Seventeen features were extracted to distinguish the hypertensive heart beat rhythms from the normal ones, and Kolmogorov-Smirnov test and sequential backward selection (SBS) were applied to get the best feature combinations. In addition, support vector machine (SVM), k-nearest neighbor (KNN) and random forest (RF) were applied as classifiers in the study. The performance of each classifier was evaluated independently using the leave-one-subject-out validation method. The best predictive model was based on RF and enabled to identify hypertensive patients by five features with an accuracy of 86.44%. The best five HRV features are sample entropy (SampEn), very low frequency spectral powers (VLF), root mean square of successful differences (RMSSD), ratio of low frequency spectral powers and high frequency spectral powers (LF/HF) and vector angle index (VAI). The results of the study show sympathetic overactivity and decreased parasympathetic tone in hypertensive patients.

Heart rate variability in hypertensive pregnancy disorders: A systematic review

BACKGROUND

Hypertensive pregnancy disorders (HPD) are associated with dysfunction of the autonomic nervous system. Cardiac autonomic functions can be assessed by heart rate variability (HRV) measurements.

OBJECTIVE

To study whether HRV detects differences in the function of the autonomic nervous system between pregnant women with HPD compared to normotensive pregnant women and between women with a history of a pregnancy complicated by HPD compared to women with a history of an uncomplicated pregnancy.

METHODS

A systematic search was performed in Medline, EMBASE, and CENTRAL to identify studies comparing HRV between pregnant women with HPD or women with a history of HPD to women with (a history of) normotensive pregnancies.

RESULTS

The search identified 523 articles of which 24 were included in this review, including 850 women with (a history of) HPD and 1205 normotensive controls. The included studies showed a large heterogenicity. A decrease in overall HRV was found in preeclampsia (PE), compared to normotensive pregnant controls. A trend is seen towards increased low frequency/high frequency-ratio in women with PE compared to normotensive pregnant controls.

CONCLUSION

Our systematic review supports the hypothesis a sympathetic overdrive is found in HPD which is associated with a parasympathetic withdrawal. However, the included studies in our review showed a large diversity in the methods applied and their results.

Cardiovascular risk assessment by electrocardiographic Holter monitoring in patients with chronic hepatitis C

INTRODUCTION

Cardiovascular diseases are ranked as the third cause of mortality among people infected with hepatitis C virus (HCV), but the relationship of infection with cardiovascular risk remains disputable. We have focused on the comprehensive use of parameters obtainable during long-term electrocardiographic (ECG) Holter monitoring.

MATERIAL AND METHODS

Heart rate variability and turbulence (HRV and HRT), deceleration/acceleration capacity (DC/AC), corrected QT interval (QTc) and late potential (LP) were used. 36 persons were included, and 30 healthy subjects formed a control group. All were submitted to 24-hour Holter ECG-monitoring.

RESULTS

The studied groups were not statistically significantly different with regards to basic anthropometric parameters. Statistically significantly higher medium and maximum heart rhythm and aminotransferase activities were recorded in patients with hepatitis C. The HRV parameters r-MSSD, p50NN, HF, and absolute DC/AC values were significantly lower in the subjects with hepatitis C than those in the control group. The QTc interval, measured for nocturnal hours, was also significantly longer in that group. There were no differences in the albumin level or basic echocardiographic parameters, including left ventricle ejection fraction. Nor was there any difference in the HRT parameters, or LP. The most interesting observation was the positive correlation among the number of viral RNA copies and DC, and LF.

CONCLUSIONS

We confirmed the presence of autonomic disorders with prevalence of sympathetic system activity and prolonged QTc interval in patients with chronic hepatitis C. Those parameters significantly correlated with infection intensity. Our results suggest that HCV infection could be an independent cardiovascular risk factor, not associated with the lipid profile. Further prospective studies are needed.

Effect of weight loss on sympatho-vagal balance in subjects with grade-3 obesity: restrictive surgery versus hypocaloric diet

Few and mostly uncontrolled studies indicate that weight loss improves heart rate variability (HRV) in grade-3 obesity. The aim of this study was to compare in grade-3 obesity surgery and hypocaloric diet on clinical and metabolic variables and on autonomic indices of HRV. Twenty-four subjects (body mass index, BMI 45.5 ± 9.13 kg/m(2)) underwent surgery (n = 12, gastric banding, LAGB) or received hypocaloric diet (n = 12, 1,000-1,200 kg/day). Clinical [BMI, systolic blood pressure (SBP) and diastolic blood pressure (DBP), heart rate] and metabolic variables [glucose, cholesterol, HDL- and LDL-cholesterol, triglycerides, AST and ALT transaminases] and 24-h Holter electrocardiographic-derived HRV parameters [R-R interval, standard deviation of R-R intervals (SDNN); low/high-frequency (LF/HF) ratio, and QT interval] were measured at baseline and after 6 months. The two groups were identical at baseline. BMI (-7.5 ± 3.57 kg/m(2), mean ± SD), glucose (-24.1 ± 26.77 mg/dL), SBP (-16.7 ± 22.19 mmHg) and DBP (-6.2 ± 8.56 mmHg) decreased in LAGB subjects (p < 0.05) and remained unchanged in controls. At 6 months, SDNN increased in LAGB subjects (+25.0 ± 37.19 ms, p < 0.05) and LF/HF ratio diminished (2.9 ± 1.84 vs. 4.9 ± 2.78; p = 0.01), with no change in controls; LF (daytime) and HF (24 h and daytime) increased in LAGB subjects, with no change in controls. Decrease in BMI correlated with SBP and DBP decrease (p < 0.05), and DBP decrease correlated with HR decrease (p < 0.05) and QT shortening (p < 0.05). Weight loss is associated with improvement of glucose metabolism, of blood pressure, and with changes in time and frequency domain parameters of HRV; all these changes indicate recovery of a more physiological autonomic control, with increase in parasympathetic and reduction in sympathetic indices of HRV.

Cardiovascular dysfunctions and sympathovagal imbalance in hypertension and prehypertension: physiological perspectives

Hypertension (HTN) and prehypertension (pre-HTN) have been identified as independent risk factors for adverse cardiovascular events. Recently, increased psychosocial stress and work stress have contributed to the increased prevalence of HTN and pre-HTN, in addition to the contribution of obesity, diabetes, poor food habits and physical inactivity. Irrespective of the etiology, sympathetic overactivity has been recognized as the main pathophysiologic mechanism in the genesis of HTN and pre-HTN. Sympathovagal imbalance owing to sympathetic overactivity and vagal withdrawal is reported to be the basis of many clinical disorders. However, the role played by vagal withdrawal has been under-reported. In this review, we have analyzed the pathophysiologic involvement of sympathovagal imbalance in the development of HTN and pre-HTN, and the link of sympathovagal imbalance to cardiovascular dysfunctions. We have emphasized that adaptation to a healthier lifestyle will help improve sympathovagal homeostasis and prevent the occurrence of HTN and pre-HTN.

Physiological reactivity to psychological stress in human pregnancy: current knowledge and future directions

Cardiovascular and neuroendocrine reactivity to acute stress are important predictors of health outcomes in non-pregnant populations. Greater magnitude and duration of physiological responses have been associated with increased risk of hypertensive disorders and diabetes, greater susceptibility to infectious illnesses, suppression of cell-mediated immunity as well as risk for depression and anxiety disorders. Stress reactivity during pregnancy has unique implications for maternal health, birth outcomes, and fetal development. However, as compared to the larger literature, our understanding of the predictors and consequences of exaggerated stress reactivity in pregnancy is limited. This paper reviews the current state of this literature with an emphasis on gaps in knowledge and future directions.

Infrared LED irradiation applied during high-intensity treadmill training improves maximal exercise tolerance in postmenopausal women: a 6-month longitudinal study

Reduced aerobic fitness is associated with an increased risk of cardiovascular diseases among the older population. The aim of this study was to investigate the effects of LED irradiation (850 nm) applied during treadmill training on the maximal exercise tolerance in postmenopausal women. At the beginning of the study, 45 postmenopausal women were assigned randomly to three groups, and 30 women completed the entire 6 months of the study. The groups were: (1) the LED group (treadmill training associated with phototherapy, n = 10), (2) the exercise group (treadmill training, n = 10), and (3) the sedentary group (neither physical training nor phototherapy, n = 10). The training was performed for 45 min twice a week for 6 months at intensities between 85% and 90% maximal heart rate (HRmax). The irradiation parameters were 39 mW/cm(2), 45 min and 108 J/cm(2). The cardiovascular parameters were measured at baseline and after 6 months. As expected, no significant differences were found in the sedentary group (p ≥ 0.05). The maximal time of tolerance (Tlim), metabolic equivalents (METs) and Bruce stage reached significantly higher values in the LED group and the exercise group (p < 0.01). Furthermore, the HR, double product and Borg score at isotime were significantly lower in the LED group and in the exercise group (p < 0.05). However, the time of recovery showed a significant decrease only in the LED group (p = 0.003). Moreover, the differences between before and after training (delta values) for the Tlim, METs and HR at isotime were greater in the LED group than in the exercise group with a significant intergroup difference (p < 0.05). Therefore, the infrared LED irradiation during treadmill training can improve maximal performance and post-exercise recovery in postmenopausal women.

Skinfold thickness is related to cardiovascular autonomic control as assessed by heart rate variability and heart rate recovery

The purpose of this study was to determine if heart rate recovery (HRR) and heart rate variability (HRV) are related to maximal aerobic fitness and selected body composition measurements. Fifty men (age = 21.9 ± 3.0 years, height = 180.8 ± 7.2 cm, weight = 80.4 ± 9.1 kg, volunteered to participate in this study. For each subject, body mass index (BMI), waist circumference (WC), and the sum of skinfolds across the chest, abdomen, and thigh regions (SUMSF) were recorded. Heart rate variability (HRV) was assessed during a 5-minute period while the subjects rested in a supine position. The following frequency domain parameters of HRV were recorded: normalized high-frequency power (HFnu), and low-frequency to high-frequency power ratio (LF:HF). To determine maximal aerobic fitness (i.e., VO2max), each subject performed a maximal graded exercise test on a treadmill. Heart rate recovery was recorded 1 (HRR1) and 2 (HRR2) minutes during a cool-down period. Mean VO2max and BMI for all the subjects were 49.5 ± 7.5 ml·kg(-1)·min(-1) and 24.7 ± 2.2 kg·m(-2), respectively. Although VO2max, WC, and SUMSF was each significantly correlated to HRR and HRV, only SUMSF had a significant independent correlation to HRR1, HRR2, HFnu, LF:HF (p < 0.01). The results of the regression procedure showed that SUMSF accounted for the greatest variance in HRR1, HRR2, HFnu, and LF:HF (p < 0.01). The results of this study suggest that cardiovascular autonomic modulation is significantly related to maximal aerobic fitness and body composition. However, SUMSF appears to have the strongest independent relationship with HRR and HRV, compared to other body composition parameters and VO2max.

Prediabetes and blood pressure effects on heart rate variability, QT-interval duration, and left ventricular hypertrophy in overweight-obese adolescents

This ancillary, descriptive correlational study examined the effect of glucose regulation, blood pressure (BP), and their combined effects on cardiac autonomic function in 128 overweight-obese 11-18-year-olds. Measures included body mass index, resting BP, fasting glucose, glucose tolerance, and cardiac autonomic function (heart rate variability, QT, and Cornell voltage). After adjusting for age and gender, multivariate analysis of covariance revealed no differences in cardiac autonomic measures based on glucose regulation (p = .319), BP (p = .286), or the interaction between glucose regulation and BP (p = .132). The additive effect of prediabetes and elevated BP did not impact cardiac autonomic function in overweight-obese youth.

Blood pressure and heart rate variability complexity analysis in pregnant women with hypertension

BACKGROUND

In this work, we perform a comparative analysis of blood pressure and heart rate variability complexity during pregnancy between normal, hypertensive, and preeclamptic women.

METHODS AND RESULTS

A total of 563 short electrocardiographic (10 min) records were obtained from 217 pregnant women (135 normal, 55 hypertensive, and 27 preeclamptic) during several gestational ages in sitting position. We used a mixed unbalanced model for the longitudinal statistical analysis and besides the conventional spectral analysis, we applied Lempel-Ziv complexity, sample entropy, approximated entropy, and detrended fluctuation analysis in the complexity measurement.

CONCLUSIONS

The obtained results revealed significant differences between pathological and normal states with important considerations related to pregnancy adaptability and evolution as well as the relationship of complexity and blood pressure with factors such as maternal age, familial history of diabetes or hypertension, and parity.

Heart rate variability dynamics for the prognosis of cardiovascular risk

Statistical, spectral, multi-resolution and non-linear methods were applied to heart rate variability (HRV) series linked with classification schemes for the prognosis of cardiovascular risk. A total of 90 HRV records were analyzed: 45 from healthy subjects and 45 from cardiovascular risk patients. A total of 52 features from all the analysis methods were evaluated using standard two-sample Kolmogorov-Smirnov test (KS-test). The results of the statistical procedure provided input to multi-layer perceptron (MLP) neural networks, radial basis function (RBF) neural networks and support vector machines (SVM) for data classification. These schemes showed high performances with both training and test sets and many combinations of features (with a maximum accuracy of 96.67%). Additionally, there was a strong consideration for breathing frequency as a relevant feature in the HRV analysis.