Patients with uncomplicated coronary artery disease have reduced heart rate variability mainly affecting vagal tone

Comprehensive evaluation of machine learning algorithms for predicting sleep-wake conditions and differentiating between the wake conditions before and after sleep during pregnancy based on heart rate variability

Introduction

Perinatal women tend to have difficulties with sleep along with autonomic characteristics. This study aimed to identify a machine learning algorithm capable of achieving high accuracy in predicting sleep-wake conditions and differentiating between the wake conditions before and after sleep during pregnancy based on heart rate variability (HRV).

Methods

Nine HRV indicators (features) and sleep-wake conditions of 154 pregnant women were measured for 1 week, from the 23rd to the 32nd weeks of pregnancy. Ten machine learning and three deep learning methods were applied to predict three types of sleep-wake conditions (wake, shallow sleep, and deep sleep). In addition, the prediction of four conditions, in which the wake conditions before and after sleep were differentiated-shallow sleep, deep sleep, and the two types of wake conditions-was also tested.

Results and Discussion

In the test for predicting three types of sleep-wake conditions, most of the algorithms, except for Naïve Bayes, showed higher areas under the curve (AUCs; 0.82-0.88) and accuracy (0.78-0.81). The test using four types of sleep-wake conditions with differentiation between the wake conditions before and after sleep also resulted in successful prediction by the gated recurrent unit with the highest AUC (0.86) and accuracy (0.79). Among the nine features, seven made major contributions to predicting sleep-wake conditions. Among the seven features, "the number of interval differences of successive RR intervals greater than 50 ms (NN50)" and "the proportion dividing NN50 by the total number of RR intervals (pNN50)" were useful to predict sleep-wake conditions unique to pregnancy. These findings suggest alterations in the vagal tone system specific to pregnancy.

COVID-19-induced Stress in Health-care Workers: Effect of 8-week Common Yoga Protocol on Autonomic Function and Inflammatory and Oxidative Stress Markers

Background

COVID-19 pandemic posed a huge stress on health-care givers affecting their physical and mental health. Wellness strategies like yoga can improve flexibility, resilience, and outlook.

Aim

The present study explored the effect of 8-week standard common yoga protocol (CYP) intervention on autonomic functions, emotional stress, oxidative stress, and inflammation markers in the nurse group of health-care givers.

Materials and Methods

It is a randomized controlled trial where 50 nurses underwent CYP and 50 participated as controls. Anthropometric parameters, cardiovascular parameters, autonomic function including time and frequency domain parameters, biochemical parameters, and psychological stress using the questionnaire were assessed before and after 8-week CYP.

Results

Total 88 nurses completed the study with 42 and 46 participants, respectively, in the CYP and control groups. CYP intervention resulted in a significant reduction in cardiovascular parameters systolic blood pressure, diastolic blood pressure, mean arterial pressure, pulse pressure, and rate pressure product (P < 0.001, P < 0.001, P < 0.001, P < 0.001, and P = 0.002, respectively), perceived stress score and Depression, Anxiety, and Stress Scale psychological variables of depression, anxiety, and stress, and serum lipid parameters compared to the control group. CYP significantly increased total power, low frequency, high frequency, root mean square of successive differences between adjacent NN intervals, change in successive normal sinus (NN) intervals exceeds 50 ms, and pNN50% (P < 0.001, P = 0.006, P = 0.006, P = 0.039, P < 0.001, and P = 0.013, respectively) suggesting improved resting autonomic modulation and parasympathodominance due to higher vagal efferent activity. There were significant reductions in serum cortisol, tumor necrosis factor-alpha, interleukin (IL)-1, and IL-6 in both the groups. Serum telomerase significantly reduced (P = 0.024) and total antioxidant capacity (P = 0.036) increased in the CYP group post intervention.

Conclusion

CYP intervention was beneficial in improving psychophysiological, autonomic, and biochemical profile of the nurse group of health-care workers.

Can peripheral biomarkers reflect the psychological condition in geriatric populations? The influence of cardiovascular comorbidities

BACKGROUND

Although previous studies indicated the association between peripheral biomarkers and psychological conditions, a higher prevalence of cardiovascular diseases (CVD) among geriatric populations may hinder the applicability of the biomarkers. The objective of this study was to assess the adequacy of the application of biomarkers to evaluate psychological conditions among geriatric populations.

METHOD

We collected information on the demographics and history of CVD in all participants. All participants completed the Brief Symptom Rating Scale (BSRS-5) and the Chinese Happiness Inventory (CHI), which are the measurement of negative and positive psychological conditions, respectively. Four indicators of the peripheral biomarkers, including the standard deviation of normal to normal RR intervals (SDNN), finger temperature, skin conductance, and electromyogram were collected for each participant during a 5-min resting state. Multiple linear regression models were conducted to evaluate the association between the biomarkers and the psychological measurements (BSRS-5, CHI) with and without the inclusion of the participants with CVD.

RESULTS

A total of 233 participants without CVD (non-CVD group) and 283 participants with CVD (CVD group) were included. The CVD group was older and with higher body mass index compared to the non-CVD group. In the multiple linear regression model with all participants, only BSRS-5 scores had a positive association with electromyogram. After the exclusion of the CVD group, the association between the BSRS-5 scores and electromyogram was more relevant, while CHI scores became positively associated with SDNN.

CONCLUSIONS

A single measurement of the peripheral biomarker may be insufficient to depict psychological conditions among geriatric populations.

QT variability unrelated to RR variability during stress testing for identification of coronary artery disease

Stress test electrocardiogram (ECG) analysis is widely used for coronary artery disease (CAD) diagnosis despite its limited accuracy. Alterations in autonomic modulation of cardiac electrical activity have been reported in CAD patients during acute ischemia. We hypothesized that those alterations could be reflected in changes in ventricular repolarization dynamics during stress testing that could be measured through QT interval variability (QTV). However, QTV is largely dependent on RR interval variability (RRV), which might hinder intrinsic ventricular repolarization dynamics. In this study, we investigated whether different markers accounting for low-frequency (LF) oscillations of QTV unrelated to RRV during stress testing could be used to separate patients with and without CAD. Power spectral density of QTV unrelated to RRV was obtained based on time-frequency coherence estimation. Instantaneous LF power of QTV and QTV unrelated to RRV were obtained. LF power of QTV unrelated to RRV normalized by LF power of QTV was also studied. Stress test ECG of 100 patients were analysed. Patients referred to coronary angiography were classified into non-CAD or CAD group. LF oscillations in QTV did not show significant differences between CAD and non-CAD groups. However, LF oscillations in QTV unrelated to RRV were significantly higher in the CAD group as compared with the non-CAD group when measured during the first phases of exercise and last phases of recovery. ROC analysis of these indices revealed area under the curve values ranging from 61 to 73%. Binomial logistic regression analysis revealed LF power of QTV unrelated to RRV, both during the first phase of exercise and last phase of recovery, as independent predictors of CAD. In conclusion, this study highlights the importance of removing the influence of RRV when measuring QTV during stress testing for CAD identification and supports the added value of LF oscillations of QTV unrelated to RRV to diagnose CAD from the first minutes of exercise. This article is part of the theme issue 'Advanced computation in cardiovascular physiology: new challenges and opportunities'.

The effects of clinical and angiographic aspects of coronary artery disease on the cardiac autonomic function: a single-center prospective cohort study

BACKGROUND

Autonomic malfunction is linked to elevated cardiovascular morbidity and mortality. Various patient characteristics can alter the cardiac autonomic function therefore, using a prospective observational study, we aimed to assess the effects of different clinical and angiographic factors of coronary artery disease (CAD) patients on the cardiac autonomic function evaluated by heart rate variability (HRV) measurement.

METHODS AND PATIENTS

100 patients undergoing coronary angiography when clinically indicated were enrolled. A short-term 5-minute HRV measurement was performed by CheckMyheart™ handheld HRV device manufactured by DailyCare BioMedical Inc, Taiwan. HRV data were fed to CheckMyheart™ 5-min HRV analysis software and interpreted based on the standard methods for HRV measurement as discussed in the Task Force of the European Society of Cardiology (ESC) and The North American Society of Pacing and Electrophysiology (NAPSE). Coronary angiography was done with an emphasis on SYNTAX (SX) score calculation.

RESULTS

The mean age of the recruited patients was 56.89±10.75 years with 85% of them were males and the mean SX score 13.11±8.52. Multivariate regression analysis of the different patient clinical and angiographic characteristics affecting HRV showed that CAD type either single or multi-vessel and SX score were the major independent variables affecting HRV in patients with CAD.

CONCLUSION

The complexity of CAD measured by SX score was the main independent predictor affecting the cardiac autonomic function estimated by HRV measurement.

Parasympathetic activity as a potential biomarker of negative symptoms in patients with schizophrenia

INTRODUCTION

Autonomic dysfunction in patients with schizophrenia has raised concern considering the higher cardiovascular mortality and morbidity rate. This phenomenon has been demonstrated using various measurements and is inferred to be associated with demographics, medical treatment, and psychopathology. However, few have targeted the role of negative symptoms within schizophrenia.

METHODS

Schizophrenia patients with stationary psychopathology were recruited from a chronic ward, a daycare center, and a nonintensive case management program. Demographic data, medication history, the Positive and Negative Syndrome Scale (PANSS) score, the Personal and Social Performance Scale (PSP) score, and the five-minute resting-state heart rate variability (HRV) were collected at trial initiation (Time 1) and a year later (Time 2). The relationships between variables and HRV indices were evaluated using correlation and regression analyses.

RESULTS

A total of 63 participants were recruited at Time 1, with 29 participants remaining at Time 2. Correlation analyses showed a negative correlation between the PANSS negative score (PANSS-N) and total power (TP), low-frequency power (LF), and high-frequency power (HF) at Time 1. The results were further examined with multiple linear regression analysis and remained significant between the PANSS-N score and HF (β = -0.306, P = .012). A generalized estimating equation model revealed the above negative association to be significant considering both timepoints.

DISCUSSION

The negative association between negative symptom severity and parasympathetic activity was significant, which may inspire further research into the corresponding treatment, the mechanisms, and the use of HRV as an applicable biomarker for treatment response.

Predictive value of heart rate deceleration capacity on coronary artery lesion in acute phase of Kawasaki disease

This study was to investigate the correlation of vagal activity with coronary artery lesion (CAL) in Kawasaki disease (KD) children, and assess the predictive value of heart rate deceleration capacity (DC) for CAL in acute phase of KD.50 KD children with CAL, 130 KD children without CAL, 30 children with acute upper respiratory infection and 100 healthy children were recruited and indicators reflecting vagal activity including DC were measstuogram. KD children with CAL showed decreased vagal activity with significantly lower values of DC. DC was negatively correlated with levels of N-terminal pro-brain natriuretic peptide (NT-proBNP) and C-reactive protein (CRP) in KD children. DC was a usable cardiac electrophysiological index to predict CAL in children with KD, with an area under the receiver operating characteristic curve (AUC) of 0.741. The cut-off value of DC for predicting CAL in KD children was 4.37 ms. DC was an independent predictor of CAL in children with KD, evaluated by multiple logistic regression analysis, KD children with DC ≤ 4.37 ms had an increased risk of CAL, with odds ratios (OR) of 5.94. Our study illustrates DC could be used to predict CAL in acute phase of KD.

Hyperventilation-induced heart rate response as a potential marker for cardiovascular disease

An increase of heart rate to physical or mental stress reflects the ability of the autonomous nervous system and the heart to respond adequately. Hyperventilation is a user-controlled breathing maneuver that has a significant impact on coronary function and hemodynamics. Thus, we aimed to investigate if the heart rate response to hyperventilation (HRRHV) can provide clinically useful information. A pooled analysis of the HRRHV after 60 s of hyperventilation was conducted in 282 participants including healthy controls; patients with heart failure (HF); coronary artery disease (CAD); a combination of both; or patients suspected of CAD but with a normal angiogram. Hyperventilation significantly increased heart rate in all groups, although healthy controls aged 55 years and older (15 ± 9 bpm) had a larger HRRHV than each of the disease groups (HF: 6 ± 6, CAD: 8 ± 8, CAD+/HF+: 6 ± 4, and CAD-/HF-: 8 ± 6 bpm, p < 0.001). No significant differences were found between disease groups. The HRRHV may serve as an easily measurable additional marker of cardiovascular health. Future studies should test its diagnostic potential as a simple, inexpensive pre-screening test to improve patient selection for other diagnostic exams.

Biological markers for anxiety disorders, OCD and PTSD: A consensus statement. Part II: Neurochemistry, neurophysiology and neurocognition

OBJECTIVE

Biomarkers are defined as anatomical, biochemical or physiological traits that are specific to certain disorders or syndromes. The objective of this paper is to summarise the current knowledge of biomarkers for anxiety disorders, obsessive-compulsive disorder (OCD) and posttraumatic stress disorder (PTSD).

METHODS

Findings in biomarker research were reviewed by a task force of international experts in the field, consisting of members of the World Federation of Societies for Biological Psychiatry Task Force on Biological Markers and of the European College of Neuropsychopharmacology Anxiety Disorders Research Network.

RESULTS

The present article (Part II) summarises findings on potential biomarkers in neurochemistry (neurotransmitters such as serotonin, norepinephrine, dopamine or GABA, neuropeptides such as cholecystokinin, neurokinins, atrial natriuretic peptide, or oxytocin, the HPA axis, neurotrophic factors such as NGF and BDNF, immunology and CO2 hypersensitivity), neurophysiology (EEG, heart rate variability) and neurocognition. The accompanying paper (Part I) focuses on neuroimaging and genetics.

CONCLUSIONS

Although at present, none of the putative biomarkers is sufficient and specific as a diagnostic tool, an abundance of high quality research has accumulated that should improve our understanding of the neurobiological causes of anxiety disorders, OCD and PTSD.

The Association Between Moderate Drinking and Heart Rate Variability in Healthy Community-Dwelling Older Women

The relationships among moderate alcohol use, autonomic tone, and arrhythmogenesis in older adults have not been adequately studied. Knowledge about these relationships is of increasing importance in light of population aging and recent epidemiological findings that associate moderate alcohol use with decreased rates of coronary artery disease. The purpose of this study was to assess the association between moderate drinking and autonomic tone in older women. Fifty-two Caucasian female participants (age 69 ± 5.2) were enrolled in the study. Autonomic tone was estimated by time-domain and frequency-domain measures of heart rate variability. Multivariate analysis revealed that alcohol consumption rate in the sample accounted for approximately one third of the 24-h variability in the SDNN and the SDANN, measures of variability cycle lengths of 24-h and more than 5-min, respectively. Significant contributions of alcohol consumption rate to the shorter-term time-domain measures rMSSD and ASDNN, all frequency-domain measures, and HR were not confirmed. However, repeated measures ANOVA revealed that, between the hours of 0000 and 0600, women who drank approximately 0.5 to 3 standard drinks per day had significantly lower [log] HF and [log] LF power compared to abstainers and a tendency toward sympathetic predominance during the evening and nighttime hours. The authors discuss the implications of these findings.

Heart Rate Variability Is Associated with Exercise Capacity in Patients with Cardiac Syndrome X

Heart rate variability (HRV) reflects the healthiness of autonomic nervous system, which is associated with exercise capacity. We therefore investigated whether HRV could predict the exercise capacity in the adults with cardiac syndrome X (CSX). A total of 238 subjects (57±12 years, 67.8% men), who were diagnosed as CSX by the positive exercise stress test and nearly normal coronary angiogram were enrolled. Power spectrum from the 24-hour recording of heart rate was analyzed in frequency domain using total power (TP) and spectral components of the very low frequency (VLF), low frequency (LF) and high frequency (HF) ranges. Among the study population, 129 subjects with impaired exercise capacity during the treadmill test had significantly lower HRV indices than those with preserved exercise capacity (≥90% of the age predicted maximal heart rate). After accounting for age, sex, and baseline SBP and heart rate, VLF (odds ratio per 1SD and 95% CI: 2.02, 1.19–3.42), LF (1.67, 1.10–2.55), and TP (1.82, 1.17–2.83) remained significantly associated with preserved exercise capacity. In addition, increased HRV indices were also associated with increased exercise duration, rate-pressure product, and heart rate recovery, independent of age, body mass index, and baseline SBP and heart rate. In subgroup analysis, HRV indices demonstrated similar predictive values related to exercise capacity across various subpopulations, especially in the young. In patients with CSX, HRV was independently associated with exercise capacity, especially in young subjects. The healthiness of autonomic nervous system may have a role in modulating the exercise capacity in patients with CSX.

Additive Value of Heart Rate Variability in Predicting Obstructive Coronary Artery Disease Beyond Framingham Risk

BACKGROUND

Heart rate variability (HRV) is usually reduced in patients with CAD. We therefore investigated whether reduced HRV is predictive of angiographic CAD beyond Framingham risk in patients with stable angina.

METHODS AND RESULTS

A total of 514 patients (age, 66.1 ± 14.3 years, 358 men) were enrolled. Holter ECG was performed before catheterization, and 24-h HRV was analyzed in both the frequency domain (VLF, LF, HF and total power) and the time domain (SDNN, SDANN, RMSSD and pNN20). Angiographic CAD was defined as ≥ 50% diameter reduction of 1 or more coronary arteries. On coronary angiography 203 patients (39.6%) had angiographic CAD. Patients with CAD had significantly higher Framingham risk and lower HRV according to both frequency and time domain parameters. After controlling for age, gender, heart rate, SBP, renal function, lipids and Framingham risk, reduced HRV indices remained predictors of CAD (OR, 95% CI for LF, HF, SDNN, RMSSD and pNN20: 0.81, 0.66-0.99; 0.77, 0.63-0.94; 0.75, 0.59-0.96; 0.72, 0.58-0.88; and 0.76, 0.62-0.94, respectively). On subgroup analysis, HRV parameters appeared to be predictive of CAD only in subjects with high Framingham risk or diabetes.

CONCLUSIONS

Reduced HRV is predictive of CAD in patients with stable angina, independent of traditional risk factors and Framingham risk. The predictive value of HRV may be relevant only in subjects with high Framingham risk or diabetes.

Heart rate and cardiovascular protection

Recent large epidemiological studies have confirmed that an elevated resting heart rate is an independent predictor of cardiovascular and overall mortality in the general population as well as in patients with hypertension, coronary heart disease and chronic heart failure. Pathophysiological studies indicate that a higher heart rate has detrimental effects that favor myocardial ischemia, ventricular arrhythmias, as well as an increase in vascular oxidative stress, endothelial dysfunction and atherosclerosis progression. Benefits of heart rate lowering drugs, such as beta-blockers and ivabradine, in reducing overall and cardiovascular-related mortality, have been demonstrated particularly in patients with coronary heart disease and heart failure. However, despite these evidences, resting heart rate is still an overlooked cardiovascular risk factor.

Blood pressure and heart rate variability during yoga-based alternate nostril breathing practice and breath awareness

BACKGROUND

Previous research has shown a reduction in blood pressure (BP) immediately after the practice of alternate nostril yoga breathing (ANYB) in normal healthy male volunteers and in hypertensive patients of both sexes. The BP during ANYB has not been recorded.

MATERIAL/METHODS

Participants were 26 male volunteers (group mean age ±SD, 23.8±3.5 years). We assessed (1) heart rate variability, (2) non-invasive arterial BP, and (3) respiration rate, during (a) ANYB and (b) breath awareness (BAW) sessions. Each session was 25 minutes. We performed assessments at 3 time points: Pre (5 minutes), during (15 minutes; for ANYB or BAW) and Post (5 minutes). A naïve-to-yoga control group (n=15 males, mean age ±SD 26.1±4.0 years) were assessed while seated quietly for 25 minutes.

RESULTS

During ANYB there was a significant decrease (repeated measures ANOVA) in systolic BP and respiration rate; while RMSSD (the square root of the mean of the sum of squares of differences between adjacent NN intervals) and NN50 (the number of interval differences of successive normal to normal intervals greater than 50 ms) significantly increased. During BAW respiration rate decreased. In contrast, respiration rate increased during the control state. ANYB and BAW were significantly different (2-factor ANOVA) in RMSSD and respiration rate. BAW and control were different with respect to respiration rate.

CONCLUSIONS

The results suggest that vagal activity increased during and after ANYB, which could have contributed to the decrease in BP and changes in the HRV.

Altered heart rate variability depend on the characteristics of coronary lesions in stable angina pectoris

OBJECTIVE

Dysfunction of cardiac autonomic nerve system is considered as one of risk factors for coronary atherosclerotic heart disease. Heart rate variability (HRV) has been used to study the correlation between damage of coronary artery and dysfunction of autonomic nervous system. We hypothesize the correlation between damage of coronary artery and dysfunction of autonomic nervous system by HRV among subjects with stable angina.

METHODS

A 236 subjects who diagnosed as stable angina pectoris by elective coronary angiography, were divided into two groups by Gensini score system (GS):GS≤32 (GS1) and GS2>32 (GS2). Subgroups were divided based on location of stenosis lesions and the number of coronary artery disease. 86 subjects suspicious with stable angina pectoris with normal coronary angiography were selected as the control group. All subjects were received 24-hour ambulatory electrocardiogram and the result of time-domain HRV was analyzed (SDNN, SDANN, SDNNind, RMSSD, PNN50).

RESULTS

Compared with control group, SDNN, SDNNind and RMSSD lower in GS1, and SDNN, SDANN, SDNNind, RMSSD, PNN50 lower in GS2; ccompared with GS1, SDNN was lower in GS2. Compared with control group, SDNN in one-vessel, SDNN, SDANN in two-vessel diseased and in three-vessel diseased were lower, and compared with two-vessel diseased, SDNN, SDANN lower in three-vessel diseased. Compared with right-coronary artery diseased, SDNN and SDANN in left-coronary artery diseased group were lower, while compared with lesions in left circumflex, SDNN in lesions in left anterior descending artery lower.

CONCLUSION

HRV may be play a crucial role in estimating the correlation between damage of coronary artery and dysfunction of autonomic nerve system.

Investigating the autonomic nervous system and cognitive functions as potential mediators of an association between cardiovascular disease and driving performance

Cardiovascular disease (CVD) impacts the autonomic nervous system and cognitive functions related to activities of daily living, including driving an automobile. Although CVD has been linked to unsafe driving, mechanisms underlying this relationship remain elusive. The aim of this study was to examine the role of cognitive functions and the autonomic nervous system as potential mediators of driving performance. Nineteen individuals having recently suffered a cardiac event and 16 individuals with no history of CVD completed a simulated drive using a STISIM simulator to assess driving performance. Heart rate was recorded throughout testing using a Polar RS800CX heart rate monitor, and measures of executive, orienting, and alerting functions were obtained through the Attention Network Test. We used the Baron and Kenny analysis method to assess potential mediating effects of the relationship between CVD and driving performance. Executive function was the only potential mediator investigated to be associated with driving (p < 0.01) and CVD (p < 0.05); however, it did not appear to play a mediating role (p = 0.28). These results suggest that individuals with CVD exhibit decrements in complex cognitive tasks such as driving and that further research is needed to better understand the mechanisms underlying this relationship.

Changes in autonomic variables following two meditative states described in yoga texts

OBJECTIVES

In ancient yoga texts there are two meditative states described. One is dharana, which requires focusing, the second is dhyana, during which there is no focusing, but an expansive mental state is reached. While an earlier study did show improved performance in an attention task after dharana, the autonomic changes during these two states have not been studied.

METHODS

Autonomic and respiratory variables were assessed in 30 healthy male volunteers (group mean age ± SD, 29.1 ± 5.1 years) during four mental states described in traditional yoga texts. These four mental states are random thinking (cancalata), nonmeditative focusing (ekagrata), meditative focusing (dharana), and effortless meditation (dhyana). Assessments were made before (5 minutes), during (20 minutes), and after (5 minutes), each of the four states, on four separate days.

RESULTS

During dhyana there was a significant increase in the skin resistance level (p<0.001; post hoc analysis following ANOVA, during compared to pre) and photo-plethysmogram amplitude (p<0.05), whereas there was a significant decrease in the heart rate (p<0.001) and breath rate (p<0.001). There was a significant decrease in the low frequency (LF) power (p<0.001) and increase in the high frequency (HF) power (p<0.001) in the frequency domain analysis of the heart rate variability (HRV) spectrum, on which HF power is associated with parasympathetic activity. There was also a significant increase in the NN50 count (the number of interval differences of successive NN intervals greater than 50 ms; p<0.001) and the pNN50 (the proportion derived by dividing NN50 by the total number of NN intervals; p<0.001) in time domain analysis of HRV, both indicative of parasympathetic activity.

CONCLUSIONS

Maximum changes were seen in autonomic variables and breath rate during the state of effortless meditation (dhyana). The changes were all suggestive of reduced sympathetic activity and/or increased vagal modulation. During dharana there was an increase in skin resistance. The changes in HRV during ekagrata and cancalata were inconclusive.

Sensitivity, specificity and predictive values of linear and nonlinear indices of heart rate variability in stable angina patients

BACKGROUND

Decreased heart rate variability (HRV) is related to higher morbidity and mortality. In this study we evaluated the linear and nonlinear indices of the HRV in stable angina patients submitted to coronary angiography.

METHODS

We studied 77 unselected patients for elective coronary angiography, which were divided into two groups: coronary artery disease (CAD) and non-CAD groups. For analysis of HRV indices, HRV was recorded beat by beat with the volunteers in the supine position for 40 minutes. We analyzed the linear indices in the time (SDNN [standard deviation of normal to normal], NN50 [total number of adjacent RR intervals with a difference of duration greater than 50ms] and RMSSD [root-mean square of differences]) and frequency domains ultra-low frequency (ULF) ≤ 0,003 Hz, very low frequency (VLF) 0,003 - 0,04 Hz, low frequency (LF) (0.04-0.15 Hz), and high frequency (HF) (0.15-0.40 Hz) as well as the ratio between LF and HF components (LF/HF). In relation to the nonlinear indices we evaluated SD1, SD2, SD1/SD2, approximate entropy (-ApEn), α1, α2, Lyapunov Exponent, Hurst Exponent, autocorrelation and dimension correlation. The definition of the cutoff point of the variables for predictive tests was obtained by the Receiver Operating Characteristic curve (ROC). The area under the ROC curve was calculated by the extended trapezoidal rule, assuming as relevant areas under the curve ≥ 0.650.

RESULTS

Coronary arterial disease patients presented reduced values of SDNN, RMSSD, NN50, HF, SD1, SD2 and -ApEn. HF ≤ 66 ms2, RMSSD ≤ 23.9 ms, ApEn ≤-0.296 and NN50 ≤ 16 presented the best discriminatory power for the presence of significant coronary obstruction.

CONCLUSION

We suggest the use of Heart Rate Variability Analysis in linear and nonlinear domains, for prognostic purposes in patients with stable angina pectoris, in view of their overall impairment.

Elevated heart rate and cardiovascular outcomes in patients with coronary artery disease: clinical evidence and pathophysiological mechanisms

There is an established body of evidence from epidemiological studies which indicates that an elevated resting heart rate is independently associated with atherosclerosis and increased cardiovascular morbidity and mortality, in both the general population and in patients with established cardiovascular disease. Clinical trial data suggest that in patients with coronary artery disease, an elevated heart rate identifies those at increased risk of adverse cardiovascular outcomes, and that lowering of heart rate may reduce major cardiovascular events in patients with an elevated heart rate and symptom-limiting angina. These results suggest that an increased heart rate may have an adverse impact on the atherosclerotic process and increase the risk of a cardiovascular event in patients with coronary artery disease. The precise pathophysiological mechanisms that link heart rate and cardiovascular outcomes have yet to be defined. Possibilities may include indirect mechanisms related to autonomic dysregulation and those due to an increase in heart rate per se, which can increase the ischaemic burden and exert local haemodynamic forces that can adversely impact on the endothelium and arterial wall. For these reasons, heart rate should be considered as a therapeutic target in the treatment of patients with coronary artery disease.

Emergency endoscopy for upper gastrointestinal bleeding in patients with coronary artery disease

BACKGROUND

Endoscopy is useful for diagnosis and treatment of upper gastrointestinal bleeding (UGIB). However, both endoscopy and UGIB may compromise the cardiovascular function. The present study is to investigate the cardiovascular responses of emergency endoscopy for patients with UGIB and stable coronary artery disease (CAD).

METHODS

Consecutive 50 patients with known CAD and 50 patients without CAD history (non-CAD group) in whom emergency endoscopy was requested for UGIB were prospectively enrolled. All patients received ambulatory electrocardiographic monitoring before, during, and after endoscopies. Cardiac indices including supraventricular and ventricular arrhythmia, ST ischemic change, and autonomic nervous function evaluated by heart rate variability were compared.

RESULTS

All patients in both groups had successful primary hemostasis, and peptic ulcer bleeding was the main etiology (82%). Compared with the non-CAD group, patients with CAD had a significantly higher incidence (42% vs 16%, P = .004) and frequency (1.19 vs 0.12 events per minute, P = .003) of ventricular arrhythmias during endoscopy. Nine patients with CAD and 1 patient without CAD had ischemic ST changes (P = .016). Comorbidity with congestive heart failure was not only associated with a higher frequency (P = .02) but also a more severe fluctuation (P = .002) of ventricular arrhythmia. None in both groups had angina or MI before, during, or after endoscopy. Heart rate variability did not show a difference.

CONCLUSIONS

Ventricular arrhythmias and myocardial ischemia, although mostly subclinical, were common in patients with stable CAD undergoing emergent endoscopy for UGIB, especially in those with concomitant congestive heart failure.

Use of heart rate variability analysis to determine the risk of cardiac ischaemia in high-risk patients undergoing general anaesthesia

The aim of this study was to investigate the use of pre-operative heart rate variability analysis to predict postoperative cardiac events (identified by 24 h Holter-ECG recording and an increase of creatine kinase MB) in high-risk cardiac patients. Length of hospital stay, the incidence of postoperative cardiac ischaemia and cardiac events after discharge were recorded. Fifty patients were assigned by the presence of cardiac events and the heart rate variability in 17 patients with an event was compared with 33 patients without. Total power was identified as a predictive parameter. The usefulness of this test was assessed in a second group of 50 patients. The incidence of cardiac events detected by Holter-ECG recording or an increased creatine kinase MB was greater and the duration of hospital stay longer in the 26 patients with total power < 400 ms(2).Hz(-1) compared with those with total power > 400 ms(2).Hz(-1) (eight and four patients and 10 (7) days (mean (SD)), vs 1 (p < 0.05) and 0 (p < 0.05) patients and 6 (2) days (p < 0.05), respectively). The total power of high-risk cardiac patients predicted postoperative cardiac events and extended length of hospital stay.

Heart rate variability derived from exercise ECG in the detection of coronary artery disease

The diagnostic performance of heart rate variability (HRV) analysis from exercise ECG in the detection of coronary artery disease (CAD) is unknown. Bicycle exercise ECG recordings from The Finnish Cardiovascular Study (FINCAVAS) of angiography-proofed CAD patients (n = 112) and a patient group with a low likelihood of CAD (n = 114) were analyzed. HRV parameters (SDNN, RMSSD, Poincaré SD1 and SD2) were calculated from 1 min segments before exercise, during exercise and after exercise. All the parameters were in addition calculated from heart rate (HR)-corrected RR-interval segments. The ST-segment depressions in each stage were also determined. The diagnostic performance of the parameters was evaluated with the area under the receiver operating characteristic (ROC) curve method. The uncorrected HRV parameters showed the best diagnostic performance in the recovery segments but the correlation with HR was also high (SDNN: 0.758/-0.64, RMSSD: 0.747/-0.60; area under the ROC/correlation coefficient). The HR correction decreased the correlation and the diagnostic performance in recovery segments (SDNN: 0.515/-0.12, RMSSD: 0.609/0.20). The diagnostic performance of ST-level at its best was higher than any of HRV parameters (ST-level: 0.795/0.36). According to the results, the HR correction decreased the diagnostic performance of the recovery phase. The HRV parameters calculated from 1 min segments of exercise test ECG were not as capable as traditional ST-segment analysis. In conclusion, the HRV analysis from exercise or recovery phase seems to be inadequate in the detection of CAD.

Spectral analysis, death and coronary anatomy following cardiac catheterisation

OBJECTIVE

To establish the associations and prognostic utility of angiographic, clinical and HRV parameters in a large cohort of patients undergoing diagnostic cardiac catheterisation (CC).

METHODS

Patients undergoing CC as elective day cases were enrolled at a single tertiary center from September 2001 to January 2003. Patient data, serum biochemistry, current drug therapy, catheter reports and five minute high resolution electrocardiograph (ECG) recordings were prospectively recorded and validated in an electronic archive. ECG recordings were used to generate time domain (SDNN (standard deviation of NN intervals)) and spectral HRV parameters (low frequency (LF) and high frequency (HF) power). Significant associations between dichotomized HRV variables and covariates were investigated using binary logistic regression. The independent prognostic ability of clinical markers was evaluated using the Cox proportional hazard model.

RESULTS

841 consecutive consenting patients of mean age 61+/-10 years were recruited into the study with a mean follow-up period of 690+/-436 days. In multivariate analysis decreasing LF spectral power was independently associated with proximal right coronary stenosis OR (odds ratio)=1.65 (95% CI=1.16-2.36), P=0.006 and to all cause mortality OR=5.01 (95% CI=1.47-17.01), P=0.010. Increasing LF power was also independently associated with normal coronary angiograms in patients investigated suspected coronary disease without a confirmed prior history of a coronary ischaemic event OR=2.16 (95% CI=1.26-3.73), P=0.002.

CONCLUSIONS

Reduced LF power independently predicts all cause mortality in a large cohort of patients receiving medical therapy after elective CC. LF power was also independently associated with >75% proximal RCA stenosis.

Heart rate variability is related to pain severity and predominant bowel pattern in women with irritable bowel syndrome

This study examined heart rate variability (HRV) in women with irritable bowel syndrome (IBS) to determine its association with gut pain and predominant bowel pattern. Women with IBS (constipation predominant n = 45, diarrhoea predominant n = 64, alternating n = 56) and healthy controls (n = 50) were recruited from the community. Severity of gut pain was measured retrospectively. The HRV (24 h) was summarized as high-frequency (HF) power and the ratio of low-frequency (LF) power to HF power. Among those women with IBS who have severe gut pain, the 15 constipation-predominant women had lower (P = 0.01) HF power and higher (P = 0.003) LF/HF ratio (geometric means 70 and 7.5, respectively) than the 21 women with diarrhoea-predominant IBS (286 and 3.1) and controls (224 and 3.9). In contrast, among women without severe pain, there is a smaller and not quite significant difference in the opposite direction. Using a broader definition of pain severity based on several questions nearly doubles the number of subjects in the severe pain group and shows even more significant results. The relationship of predominant bowel pattern to HRV is qualitatively different in the subgroup of patients with more severe pain than in the subgroup with less severe pain.

Relationship between electrocardiographic and biochemical variables in coronary artery disease

BACKGROUND

ECG (electrocardiogram) markers reflecting abnormal heart rate variability and abnormal repolarization as well as several biochemical markers reflecting inflammation, endothelial dysfunction, and procoagulation states were reported to show an association with increased cardiovascular mortality. ECG and biochemical markers could operate independently or they could interrelate in pathogenetic pathways of coronary disease. In this study, we aimed to explore the relationship between ECG and biochemical markers in a longitudinal study of coronary patients.

METHODS

A total of 499 observations from 52 patients with up to 12 repeated measurements were collected providing data on series of ECG (heart rate variability and repolarization) parameters and biochemical parameters. Generalized estimating equation models adjusting for repeated measurements were used for the analyses.

RESULTS

There was a significant association between ECG parameters reflecting abnormal repolarization (prolonged QT interval, lower T wave amplitude) and elevated levels of C-reactive protein and fibrinogen. Abnormal heart rate variability, increased sympathetic tone (low-frequency power) was associated with increased concentrations of soluble E-selectin, a marker of endothelial cell activation. There was no association between ECG markers and parameters reflecting increased procoagulation states.

CONCLUSION

These results indicate that there is an association between ECG parameters and blood markers reflecting endothelial function and inflammation in coronary artery disease patients. The pathophysiologic mechanisms of these associations remain to be elucidated.

Relationships between pulse wave velocity and heart rate variability in healthy men with a range of moderate-to-vigorous physical activity levels

Pulse wave velocity (PWV) is associated with heart rate variability (HRV) in 24-39-year-old men. This study of 40-65-year-old men ranging in moderate-to-vigorous physical activity levels investigated whether (a) PWV is related to spectral HRV, (b) using normalised units for HRV influences that relationship, and (c) HRV predicts PWV when other factors, including age and blood pressure, are accounted for. Subjects were healthy men (N=115), mean (SD) age 50.8 (7.1) years. Carotid-femoral PWV was measured using Complior. HRV was derived from a 5 min ECG for total, high-frequency, and low-frequency power (TP, HF, and LF, respectively), the LF/HF ratio, and normalised units for HF (HFnu) and LF (LFnu). Non-parametric data were natural log-transformed. PWV was 8.5 (1.4) m s-1. TP, HF, LF, LF/HF, HFnu and LFnu were 1908 (2195) m s2, 577 (1034) m s2, 457 (514) m s2, 1.5 (1.3), 46.8 (17.9), and 49.4 (19.4), respectively. PWV was inversely associated with TP (R2=0.061, p=0.008), HF (R2=0.095, p=0.001), LF (R2=0.086, p=0.002) and HFnu (R2=0.040, p=0.031), but was not associated with LF/HF (R2=0.020, p=0.136) or LFnu (R2=0.028 p=0.076). Only age and systolic blood pressure (adjusted R2=0.306, p<0.001) predicted PWV in multivariate analysis. This study has shown that PWV was weakly associated with TP and HF. The use of normalised units only influenced the relationship between PWV and LF. Finally, relationships between PWV and HRV are mediated through age and systolic blood pressure in this population of men ranging in moderate-to-vigorous physical activity level.

Altered Autonomic Cardiac Control Predicts Restenosis After Percutaneous Coronary Intervention

BACKGROUND

Early and late restenosis in up to 30% remains a major problem for long-term success after percutaneous coronary intervention (PCI). Compared to bare metal stents, the use of drug-eluting stents reduces restenosis below 10%, but implant coasts have to be considered. In restenosis noninvasive testing lacks diagnostic power. We applied a new approach to identify patients with a high risk for restenosis after PCI by combining heart rate (HR) and blood pressure variability (BPV) analyses.

METHODS

In 52 patients with clinical suspicion of restenosis and history of PCI, we investigated patterns of cardiovagal autonomic regulation prior to cardiac catheterization. The patients were separated in (i) patients with restenosis (CAD+R) and (ii) patients without restenosis (CAD-R), where restenosis is defined as a stenosis greater than 75% of luminal diameter in at least one main vessel. The following parameters/methods were evaluated: Canadian Cardiovascular Society grade (CCS-grade), vessel disease score (CAD-level), left ventricular ejection fraction (LVEF), heart rate variability (HRV), BPV, baroreflex sensitivity (BRS), as well as HR turbulence and blood pressure (BP) potentiation caused by premature ventricular complexes.

RESULTS

Whereas age, LVEF, CAD-level, CCS-grade, and mean BP did not differ between CAD+R and CAD-R, significant differences were found in (i) BPV: diastolic LF/P, systolic, and diastolic UVLF, (ii) in BRS: slope of tachycardic sequences, and (iii) in extrasystolic parameters: heart rate turbulence onset (HRTO) and potentiation of systolic BP (SBPP). Standard HRV parameters did not show significant differences between the groups. Using the two parameters diastolic LF/P (threshold >0.2) and HRTO (threshold >0) restenosis were predicted in 83.4%.

CONCLUSIONS

These results demonstrate that indicators of sympathetic activation or vagal depression identify restenosis in patients after PCI, thus opening a perspective for a new noninvasive monitoring.

Comparison of the short-term effects of salmeterol and formoterol on heart rate variability in adult asthmatic patients

STUDY OBJECTIVES

We investigated the effects of beta2-adrenergic agonists salmeterol and formoterol on heart rate variability (HRV) in adult asthmatic patients using time-domain measures of HRV.

PATIENTS

Thirty-nine adult patients with asthma were studied. All patients showed a mild-to-moderate decrease in baseline FEV1. Any diseases that might have influenced the autonomic function were excluded. All patients underwent a complete physical examination and medical history that revealed no cardiovascular disease or medication.

METHODS

The beta2-adrenergic inhaled agonists salmeterol, 50 microg, and formoterol, 12 microg, were used in the study. HRV analysis was performed for each 5-min segment: 5 min and 10 min before inhalation of the study drug, and 5, 10, 15, 20, 25, and 30 min after inhalation. Time-domain parameters of HRV were calculated: (1) the SD all normal-to-normal intervals; (2) the SD of the mean of all normal-to-normal intervals in all 5-min segments of the entire recording; (3) the root mean square of differences between adjacent normal-to-normal intervals; (4) the mean of the SD of all normal-to-normal intervals in all the 5-min intervals; and (5) the SD of the SD of all normal-to-normal intervals in all the 5-min intervals.

RESULTS

Baseline HRV parameters were not significantly different between formoterol and salmeterol groups. There were no significant differences in HRV parameters after formoterol and salmeterol inhalation. The HRV parameters in each 5-min segment in the formoterol group were not statistically significant different when compared to the same segment in the salmeterol group.

CONCLUSION

Salmeterol and formoterol have no short-term adverse effects on HRV.

Effects of amlodipine and lacidipine on heart rate variability in hypertensive patients with stable angina pectoris and isolated left ventricular diastolic dysfunction

OBJECTIVE

To estimate the influence of therapy with amlodipine (A) or lacidipine (L) on heart rate variability (HRV) time and frequency domain parameters in hypertensive patients with stable angina pectoris and isolated left ventricular diastolic dysfunction.

METHODS

After a 1-week washout period, the patients were randomized to receive amlodipine 10 mg (30 patients) or lacidipine 6 mg (30 patients) once-daily for 4 weeks. HRV parameters were determined over a period of 24 h, echocardiography and exercise test were performed before and after treatment.

RESULTS

All HRV time domain parameters after applying amlodipine did not change significantly. A reliable decrease only of the root mean square of differences between adjacent normal-to-normal intervals (RMSSD)-32.9 +/- 13 vs. 27.5 +/- 9-was noticed after treatment with lacidipine. In the lacidipine group, the change of RMSSD negatively correlated with the extent of ST segment depression during exercise testing (R = -0.43; P < 0.05). Both drugs reduced total power (A, 2234 +/- 1270 vs. 1813 +/- 889; L, 2205 +/- 1151 vs. 1825 +/- 896; P < 0.01), very low (A, 1451 +/- 733 vs. 1143 +/- 534; L, 1413 +/- 759 vs. 1213 +/- 616; P < 0.05), and low frequency power (A, 610 +/- 459 vs. 447 +/- 321; L, 569 +/- 323 vs. 442 +/- 241; P < 0.01). After amlodipine, high frequency power remained unchanged, whereas low-high frequency ratio decreased (4.54 +/- 1.72 vs. 3.77+/-1.73; P < 0.05). After lacidipine, high frequency power decreased (178.8 +/- 153.2 vs. 132.1 +/- 79.3; P < 0.05), whereas the ratio of low frequency to high frequency did not change.

CONCLUSIONS

Amlodipine and lacidipine reduce the influence of humoral control and sympathetic autonomic nervous system activity. The autonomic balance becomes shifted toward the increased vagal activity only by amlodipine.

Differential index, a novel graphical method for measurements of heart rate variability

BACKGROUND

Commonly used methods to evaluate heart rate variability require extensive filtering of the registrations in order to exclude artefacts and ectopic beats. We developed and validated a novel graphical method for time-domain measurements of heart rate variability, the differential index, which does not require filtering and is simple to use.

METHODS

The 24-h ambulatory long-term electrocardiogram recordings from 120 patients with angina pectoris and 49 control subjects were computerised without any filtering process. Sample density histograms of differences in the RR interval for successive beats were constructed and the widths of the histograms were used to obtain the differential index. For comparison, the same registrations were analysed by conventional methods.

RESULTS

The differential index was most closely related (P<0.001) to conventional short-term time domain (e.g. percent of differences between adjacent normal RR intervals >50 ms, pNN50, r=0.81) and frequency-domain (e.g. high frequency power, r=0.84) components, but also to long-term time domain (e.g. standard deviation of all normal-to-normal RR intervals for all 5-min segments of the entire registration, SDNNIDX, r=0.72) and frequency-domain (e.g. low frequency power, r=0.64) components.

CONCLUSION

The differential index method shows good agreement with established indices of heart rate variability. The insensitivity to recording artefacts and short-lasting disturbances of sinus rhythm make the differential index method particularly suited when data quality is imperfect. The simplicity of the method is valuable when large numbers of registrations are to be evaluated.

Atrioventricular conduction variability in coronary patients

Variability in atrioventricular (AV) conduction has been described in healthy subjects, whereas data for coronary patients are lacking. This study was designed to evaluate AV conduction variability in patients with stable coronary artery disease. Beat-to-beat PR interval variability with 5-minute resting high-resolution electrocardiogram recordings was measured in 30 men (mean age 50.9 years) with effort angina pectoris and 30 age-matched men without clinically evident coronary artery disease (controls). To evaluate the degree of coronary artery disease in coronary patients, coronary angiography was performed. Coronary patients displayed significantly lower values of PR interval variability compared with control subjects (P <.001). Relative PR variability (PRPP) index, calculated as the ratio of normalized PR variability to cycle length variability, was significantly higher in coronary patients (P =.001) and did depend on the degree of coronary artery disease. We concluded that coronary artery disease is associated with decreased beat-to-beat fluctuations in AV conduction. Increased relative PR variability index suggests inhomogeneous AV conduction in stable coronary atherosclerosis.

Preinfarction angina protects against out-of-hospital ventricular fibrillation in patients with acute occlusion of the left coronary artery

OBJECTIVES

The goal of this study was to evaluate the effect of preconditioning on out-of-hospital ventricular fibrillation (VF) in patients with acute myocardial infarction (AMI).

BACKGROUND

More than half of the deaths associated with AMI occur out of the hospital and within 1 h of symptom onset. In humans, preinfarction angina (PA), which can serve as a surrogate marker for preconditioning, reduces infarct size, but the protective effect against out-of-hospital VF has not been investigated.

METHODS

Preinfarction angina status and acute coronary angiographic findings of 72 consecutive patients with AMI complicated by out-of-hospital VF were compared with 144 matched controls without this complication.

RESULTS

Preinfarction angina is associated with a lower risk for VF (odds ratio [OR]: 0.40, 95% confidence interval [CI]: 0.18 to 0.88). In patients with acute occlusion of the left coronary artery (LCA) (n = 136), the risk reduction is pronounced (OR: 0.25, 95% CI: 0.10 to 0.66), whereas, in patients with acute occlusion of the right coronary artery (RCA) (n = 67), the protective effect of PA on VF was not observed (OR: 2.25, 95% CI: 0.45 to 11.22). Subgroup and multivariate analyses show that the protective effect is independent of cardiovascular risk factors, preinfarction treatment with beta-adrenergic blocking agents or aspirin, the presence of collaterals or residual antegrade flow or the extent of coronary artery disease.

CONCLUSIONS

Preinfarction angina protects against out-of-hospital VF in patients with acute occlusion of the LCA. This protection is independent of risk factors or coronary anatomy. A larger study is needed to examine the apparently different effect in patients with acute occlusion of the RCA.

A novel robust index to assess beat-to-beat variability in heart rate time-series analysis

A new index is proposed to estimate the variance of the differentiated heart rate (RR) time series from its truncated histogram. The index is more robust to artifacts than the standard deviation of the differentiated RR time series (rMSDD) and, unlike the pNN50, does not saturate for very high or very low heart rate variability.