Reduced heart rate variability and new-onset hypertension: insights into pathogenesis of hypertension: the Framingham Heart Study

Obstructive sleep apnea and hypertension: a critical review

Obstructive sleep apnea (OSA) is a prevalent sleep disorder which is characterized by recurrent upper closure with oxygen desaturation and sleep disruption. OSA increases the risk of vascular disorders in the form of stroke, myocardial infarction, congestive heart failure, and hypertension. The mechanisms underlying the vascular disorders are several and include intermittent hypoxia with release of cytokines, angiogenic inhibitors, free radicals, and adhesion molecules. During apneas, arterial blood pressure gradually rises and surges abruptly after the termination of apnea. Two thirds of patients with OSA will ultimately have diurnal hypertension. This review discusses the literature supporting the significant role of OSA in hypertension and the effect of OSA treatment on blood pressure.

Personalized hypertension management in practice

The revolution occurring in genomic and personalized medicine is likely to have a significant impact on the management of hypertension. However, from the perspective of translating new knowledge into clinical practice, progress has been slow. This review article summarizes recent advances in hypertension-related diagnostics while also offering new perspective on hypertension management for the future. Such new perspectives will likely require a paradigm shift toward more integrated and holistic approaches for better prevention and treatment of hypertension in both individuals and the population as a whole.

Are smoking and passive smoking related with heart rate variability in male adolescents?

Objective

To analyze the relation between smoking and passive smoking with heart rate variability parameters in male adolescents.

Methods

The sample consisted of 1,152 males, aged 14 and 19 years. Data related to smoking and passive smoking were collected using a questionnaire. RR intervals were obtained by a heart rate monitor, on supine position, for 10 minutes. After collecting the RR intervals, time (standard deviation of all RR intervals, root mean square of the squared differences between adjacent normal RR intervals and the percentage of adjacent intervals over 50ms) and frequency domains (low and high frequency and sympathovagal balance) parameters of heart rate variability were obtained.

Results

No significant differences between smoker and nonsmoker adolescents were observed in heart rate variability parameters (p>0.05). Similarly, heart rate variability parameters did not show significant difference between exposed and not exposed to passive smoking (p>0.05).

Conclusion

Cigarette smoking and passive smoking are not related to heart rate variability in adolescence.

Association between left ventricular mechanics and heart rate variability in untreated hypertensive patients

The authors sought to investigate left ventricular (LV) mechanics and heart rate variability (HRV), and their relationship, in untreated hypertensive patients. A total of 63 untreated hypertensive patients and 45 healthy patients were included. All patients underwent 24-hour Holter monitoring and echocardiographic examination (two- and three-dimensional). All parameters of time and frequency domain of HRV were decreased in the hypertensive patients. Two-dimensional LV longitudinal and circumferential deformation was significantly reduced in hypertensive patients. Three-dimensional LV strain in all three directions as well as area strain were reduced in the hypertensive group. In two different models of multivariate regression, two-dimensional LV longitudinal and circumferential strain, as well as three-dimensional LV area strain, remained associated with HRV parameters independently of LV structural and functional parameters. This study showed that LV mechanics and HRV were significantly impaired in untreated hypertensive patients. Two- and three-dimensional echocardiographic LV deformation were independently associated with HRV parameters in the whole study population.

Identifying genetic variants for heart rate variability in the acetylcholine pathway

Heart rate variability is an important risk factor for cardiovascular disease and all-cause mortality. The acetylcholine pathway plays a key role in explaining heart rate variability in humans. We assessed whether 443 genotyped and imputed common genetic variants in eight key genes (CHAT, SLC18A3, SLC5A7, CHRNB4, CHRNA3, CHRNA, CHRM2 and ACHE) of the acetylcholine pathway were associated with variation in an established measure of heart rate variability reflecting parasympathetic control of the heart rhythm, the root mean square of successive differences (RMSSD) of normal RR intervals. The association was studied in a two stage design in individuals of European descent. First, analyses were performed in a discovery sample of four cohorts (n = 3429, discovery stage). Second, findings were replicated in three independent cohorts (n = 3311, replication stage), and finally the two stages were combined in a meta-analysis (n = 6740). RMSSD data were obtained under resting conditions. After correction for multiple testing, none of the SNPs showed an association with RMSSD. In conclusion, no common genetic variants for heart rate variability were identified in the largest and most comprehensive candidate gene study on the acetylcholine pathway to date. Future gene finding efforts for RMSSD may want to focus on hypothesis free approaches such as the genome-wide association study.

Menopausal status in relation to cardiovascular stress reactivity in healthy Japanese participants

OBJECTIVE

To investigate the hypothesis that postmenopausal women demonstrate greater cardiovascular stress reactivity during mental stress tasks than do both premenopausal women and men.

METHODS

The study included 979 Japanese participants (338 men and 641 women [238 postmenopausal]) aged 16 to 82 years. Blood pressure, heart rate, heart rate variability, and peripheral blood flow were measured at rest and during a mirror drawing stress task and a maze task. Differences between measured variables during tasks and at rest were calculated and considered to represent reactivity to stress. Analyses were adjusted for age and other potential confounding factors.

RESULTS

After adjusting for multiple factors, significant group effects were found for systolic blood pressure (SBP), diastolic blood pressure, heart rate, low-frequency (LF), LF/high-frequency, and peripheral blood flow (effect size: partial η = 0.015, 0.011, 0.013, 0.013, 0.008, and 0.009, respectively). Postmenopausal women were more reactive than men to stress for SBP (15.4 ± 0.8 versus 11.7 ± 0.6 mm Hg), diastolic blood pressure (10.4 ± 0.6 versus 8.0 ± 0.5 mm Hg), heart rate (2.7 ± 0.5 versus 0.7 ± 0.4 beats/min), LF (23.0 ± 5.2 versus 3.2 ± 3.8 ms/Hz), and peripheral blood flow (-39.0 ± 3.8 versus -25.9 ± 2.8 Laser Doppler Perfusion Units) and more reactive than premenopausal women (p < .050) for SBP (15.4 ± 0.8 versus. 12.4 ± 0.5 mm Hg) and LF/high-frequency (1.7 ± 0.1 versus 1.3 ± 0.1).

CONCLUSIONS

Postmenopausal Japanese women evidenced greater cardiovascular stress reactivity during mental stress tasks than did Japanese men or premenopausal women. Cardiovascular hyperreactivity could play a role in the higher risks of cardiovascular diseases in postmenopausal women.

Heart rate variability and cardiovascular risk factors in adolescent boys

OBJECTIVE

To establish reference values of heart rate variability (HRV) measures in a cohort of adolescent boys and to determine the relationship between HRV and the clustering of risk factors (RFs) for cardiovascular disease.

STUDY DESIGN

This cross-sectional study included 1152 adolescent boys (age: 16.6 ± 1.2 years old). Demographic data, health-related habits, obesity indicators, and blood pressure were evaluated. HRV measures of time (SD of all RR intervals, root mean square of the squared differences between adjacent normal RR intervals, and the percentage of adjacent intervals over 50 ms) and frequency domains were assessed (low [LF] and high [HF] frequency).

RESULTS

The components of HRV were RR interval (827 ± 128 ms), SD of all RR intervals (61.9 ± 23.5 ms), root mean square of the squared differences between adjacent normal RR intervals (54.5 ± 29.4 ms), percentage of adjacent intervals over 50 ms (29.4 ± 20.4%), LF (53 ± 16 nu), HF (47 ± 16), and LF/HF (1.44 ± 1.08). Greater sympathetic and lower parasympathetic modulation at rest were associated with higher adiposity, higher blood pressure and physical inactivity. Adolescents with 2 or more RFs also presented lower HRV than subjects with no RFs (P < .001).

CONCLUSIONS

The study has provided descriptive indicators that help the interpretation of HRV results in adolescents. Lower HRV measures are associated with the clustering of cardiovascular RFs.

Atrial fibrillation in essential hypertension: an issue of concern

Many clinical studies indicate that atrial fibrillation is closely related to hypertension. Atrial fibrillation is not only associated with the level of blood pressure (BP) but also with the circadian rhythms of BP. However, the underlying mechanisms of atrial fibrillation in essential hypertension patients remain largely unknown. Hypertension may facilitate the onset and persistence of atrial fibrillation by stretch-induced changes in the repolarization of atrial myocytes (triggers of atrial fibrillation) and atrial remodeling (structural and electrical remodeling). Importantly, the effects of hypertension on atrial fibrillation are progressive. These progressive anatomic, functional, electrophysiological and structural changes occur at different times. This characterization of the time course of atrial changes presents an intervention window before remodeling progresses to changes that are difficult to reverse. Given that the medium to long-term efficacy of antiarrhythmic drugs has proved poor, it is essential to seek new therapies to prevent the onset of atrial fibrillation and to effectively control recurrences of atrial fibrillation. The study of nonantiarrhythmic drugs that act on the atrial remodeling that constitutes the substrate of the arrhythmia is a new and very interesting field of research. Treatment with angiotensin-converting enzyme inhibitors angiotension-converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers (ARBs) seems more promising. However, from recent trials, only hypertension with structural heart disease, left ventricular dysfunction and left ventricular hypertrophy benefit from ACEIs and ARBs. This article reviews many aspects of atrial fibrillatio in essential hypertension patients to provide the foundation of atrial fibrillatio treatment.

Heart rate recovery after maximal exercise is blunted in hypertensive seniors

Abnormal heart rate recovery (HRR) after maximal exercise may indicate autonomic dysfunction and is a predictor for cardiovascular mortality. HRR is attenuated with aging and in middle-age hypertensive patients, but it is unknown whether HRR is attenuated in older-age adults with hypertension. This study compared HRR among 16 unmedicated stage 1 hypertensive (HTN) participants [nine men/seven women; 68 ± 5 (SD) yr; awake ambulatory blood pressure (BP) 149 ± 10/87 ± 7 mmHg] and 16 normotensive [control (CON)] participants (nine men/seven women; 67 ± 5 yr; 122 ± 4/72 ± 5 mmHg). HR, BP, oxygen uptake (V̇o2), cardiac output (Qc), and stroke volume (SV) were measured at rest, at two steady-state work rates, and graded exercise to peak during maximal treadmill exercise. During 6 min of seated recovery, the change in HR (ΔHR) was obtained every minute and BP every 2 min. In addition, HRR and R-R interval (RRI) recovery kinetics were analyzed using a monoexponential function, and the indexes (HRRI and RRII) were calculated. Maximum V̇o2, HR, Qc, and SV responses during exercise were not different between groups. ΔHR was significantly different (P < 0.001) between the HTN group (26 ± 8) and the CON group (36 ± 12 beats/min) after 1 min of recovery but less convincing at 2 min (P = 0.055). BP recovery was similar between groups. HRRI was significantly lower (P = 0.016), and there was a trend of lower RRII (P = 0.066) in the HTN group compared with the CON group. These results show that in older-age adults, HRR is attenuated further with the presence of hypertension, which may be attributable to an impairment of autonomic function.

A reduced heart rate variability is independently associated with a blunted nocturnal blood pressure fall in patients with resistant hypertension

BACKGROUND

A blunted nocturnal blood pressure (BP) fall is a marker of worse cardiovascular outcomes, and autonomic imbalance may be involved. The objective was to evaluate the associations between the nocturnal BP fall and heart rate variability (HRV) parameters in resistant hypertension.

DESIGN AND METHODS

In a cross-sectional analysis, 424 resistant hypertensive patients performed 24-h ambulatory BP and Holter monitoring, and 221 patients also performed polysomnography. Time-domain HRV parameters evaluated were the standard deviation of all normal RR intervals (SDNN), the standard deviation of the averaged normal RR intervals for all 5-min segments (SDANN), the root mean square of differences between adjacent R-R intervals (rMSSD) and the percentage of adjacent R-R intervals that varied by more than 50 ms (pNN50). Multivariate linear and logistic regressions assessed associations between the nocturnal BP fall and HRV parameters.

RESULTS

Two hundred and sixty-six patients (63%) presented a nondipping pattern. These patients had lower SDNN and SDANN than normal dipping patients, but equal rMSSD and pNN50. On multivariate analysis, after adjustments for several confounders, a reduced SDNN (<70 ms) implied a 2.9 to 3.4-fold [95% confidence interval (CI) 1.2-8.5] and a reduced SDANN (<50 ms) a 3.7 to 4.2-fold (95% CI 1.5-11.4) higher odds of having a nondipping pattern. Further adjustment for the presence and severity of obstructive sleep apnoea did not change the results.

CONCLUSION

Reduced SDNN and SDANN, two HRV parameters that mainly reflect sympathetic overactivity, were independently associated with a blunted nocturnal BP fall in resistant hypertension. These relationships offer insight into physiopathological mechanisms linking the circadian BP variability to cardiovascular outcomes.

[Heart rate variability is significantly reduced in non-diabetic patients with hypertension]

INTRODUCTIONS

Heart rate variability is reduced among patients with hypertension and/or with diabetes mellitus. Hypertension and diabetes show frequent co-morbidity, but it is still not entirely clear whether heart rate variability is reduced in non-diabetic patients with hypertension.

AIM

The aim of the authors was to evaluate the heart rate variability in hypertensive patients with and without diabetes and in control subjects.

METHOD

130 patients with hypertension, 48 patients with hypertension and type 2 diabetes mellitus, and 87 control subjects were involved in the study. Minimum, mean and maximum heart rate, and parameters of heart rate variability were measured.

RESULTS

The mean of minimum heart rate did not differ significantly between the three groups. However, all other parameters were significantly reduced in patients with hypertension with and without diabetes as compared to the control group. No significant differences were observed between hypertensive patients with and without diabetes mellitus.

CONCLUSIONS

Heart rate variability is significantly reduced in non-diabetic patients with hypertension. It seems that type 2 diabetes results in no further significant reduction of heart rate variability in patients with hypertension.

The association between heart rate variability and biatrial phasic function in arterial hypertension

We sought to investigate (1) left atrial (LA) and right atrial (RA) phasic function and mechanics; (2) heart rate variability (HRV); and (3) their relationship in untreated hypertensive patients. This cross-sectional study involved 73 untreated hypertensive patients and 51 subjects without cardiovascular risk factors with similar gender and age. All the subjects underwent a 24-hour Holter monitoring and comprehensive two- and three-dimensional echocardiography examination. LA and RA reservoir and conduit function, estimated by total and passive atrial emptying fractions and systolic and early diastolic strain rates, were reduced in the hypertensive patients. On the other hand, LA and RA booster function, assessed by active atrial emptying fraction and late diastolic strain rate, was increased in this group. All time and frequency domain heart-rate variability parameters were reduced in the hypertensive subjects. In the whole study population, parameters of cardiac sympathovagal balance (standard deviation of all normal RR intervals, root mean square of the difference between the coupling intervals of adjacent R-R intervals, 24-hour low-frequency domain [0.04-0.15 Hz], 24-hour high-frequency domain [0.15-0.40 Hz], and 24-hour total power [0.01-0.40 Hz]) correlated with LA and RA volume indexes, biatrial booster function assessed by active emptying fraction, biatrial longitudinal function evaluated by longitudinal strain; and biatrial expansion index. LA and RA phasic function and mechanics are significantly impaired in the untreated hypertensive patients. Heart-rate variability parameters are also deteriorated in the hypertensive population. Biatrial function and mechanics correlated with cardiac autonomic nervous system indexes in the whole study population.

Cognitive function is associated with impaired heart rate variability in ageing adults: the Irish longitudinal study on ageing wave one results

OBJECTIVE

To examine the independent association between heart rate variability (HRV) and cognitive performance, in a nationally representative population study of older adults.

METHODS

Cross-sectional analysis of wave 1 data from the Irish longitudinal study on ageing (TILDA) was performed. A subset of 4,763 participants who underwent ECG recording during resting and paced breathing periods were used for the analysis. HRV indices were divided into quintiles for comparison of values and cognitive performance was defined using the Montreal cognitive assessment (MOCA) score. Multivariate linear regression was used to model the association between cognition and different quintiles of each HRV index, after adjustment for covariates.

RESULTS

The mean age was 61.7 ± 8.3 years and 2,618 (55 %) were female. Lower quintiles of SDNN (P = 0.01-paced), LF (P = 0.001-paced), and LF:HF ratio (P = 0.049-paced) were significantly associated with lower MOCA scores (during both recording periods), independent of confounders. Sub-domains of MOCA responsible for the relationship were predominantly memory recall and language.

INTERPRETATION

Reduced HRV is significantly associated with lower cognitive performance at a population level in people aged 50 and older. This further strengthens the relationship between autonomic dysfunction and cognitive disorders.

Acupuncture Point Laterality: Investigation of Acute Effects of Quchi (LI11) in Patients with Hypertension Using Heart Rate Variability

Hypertension is one of the major risk factors for cardiovascular disease worldwide. Over 70% of the patients use antihypertensive drugs, so nonpharmacological treatments in addition to the medication are important. Our goal was to investigate acupuncture treatment on the Quchi acupoint using heart rate (HR) and heart rate variability (HRV) and to find out whether there is a laterality in acute effects. Sixty hypertensive patients (36 female, 24 male; mean age ± SD 55.8 ± 9.7 years) were randomly assigned to two manual needle acupuncture groups (group A: left Quchi (LI11) acupoint, group B: right Quchi acupoint). There was a significant (P < 0.05) decrease in HR immediately after inserting and stimulating the needle at the left and the right Quchi acupuncture point. In contrast, total HRV increased immediately after inserting the needle, but this increase was significant only towards the end of the stimulation phase and after removing the needle. There were some differences between stimulation of the left and right Quchi acupoint, but they remained insignificant. This study provides evidence that there is a beneficial effect on heart rate variability in patients with hypertension and that there are some effects of laterality of the acupoint Quchi.

Heart rate variability is severely impaired among type 2 diabetic patients with hypertension

INTRODUCTION

The aim of our study was to evaluate the relative effect of diabetes and hypertension on heart rate variability.

RESEARCH DESIGN AND METHODS

Four age-matched groups including type 2 diabetic patients with and without hypertension, non-diabetic patients with essential hypertension and healthy control subjects were studied. Autonomic function was evaluated by the standard cardiovascular reflex tests and 24-hour heart rate variability measurement. Heart rate variability was characterized by the triangular index value and by the spectral components of the frequency domain analysis.

RESULTS

According to the two-way analysis of variance on ranks, all parameters were influenced negatively by diabetes (heart rate variability triangular index: p < 0.001; low-frequency component: p < 0.0001; high-frequency component: p < 0.001; and total power: p < 0.0001), whereas hypertension had a negative effect only on the low-frequency component (p < 0.05). The interaction between hypertension and diabetes was not significant, indicating that their effects on the heart rate variability parameters are additive. Beat-to-beat variation upon deep breathing, the most sensitive cardiovascular reflex test was also negatively influenced by both diabetes (p < 0.001) and hypertension, (p < 0.05), and their effects were additive.

CONCLUSIONS

Diabetes appears to have a greater effect on autonomic dysfunction compared with hypertension. Patients suffering from both diabetes and hypertension are at the highest risk of reduced heart rate variability. Early assessment of the autonomic nerve function is suggested in diabetic patients with hypertension.

Delayed heart rate recovery is strongly associated with early and late-stage prehypertension during exercise stress testing

BACKGROUND

Heart rate recovery (HRR) has been shown to predict cardiovascular disease mortality. HRR is delayed in hypertension, but its association with prehypertension (PHT) has not been well studied.

METHODS

The study population consisted of 683 asymptomatic individuals (90% men, aged 47±7.9 years). HRR was defined as peak heart rate minus heart rate after a 2-minute rest. PHT was categorized into stage I (systolic blood pressure (SBP) 120-129mm Hg or diastolic BP (DBP) 80-84mm Hg) or stage II (SBP 130-139mm Hg or DBP 85-89mm Hg). Logistic regression was used to generate odds ratios (ORs) for the relationship between HRR and PHT.

RESULTS

The mean HRR was lower in the PHT groups than in those who were normotensive (60 bpm and 58 bpm in stages I and II PHT vs. 65 bpm in normal BP; P <0.01). Persons with PHT were more likely to be in the lowest quartile of HRR compared with those with normal BP (adjusted OR, 3.80 and 95% confidence interval [CI], 1.06, 13.56 for stage II PHT and adjusted OR, 3.01 and 95% CI 1.05, 8.66 for stage I PHT). In a fully adjusted model, HRR was still significantly associated with both stages of PHT.

CONCLUSION

Among asymptomatic patients undergoing stress testing, delayed HRR was independently associated with early and late stages of PHT. Further studies are needed to determine the usefulness of measuring HRR in the prevention and management of hypertension.

Heart rate variability and blood pressure among Japanese men and women: a community-based cross-sectional study

Heart rate variability (HRV) is associated with blood pressure levels; however, very few studies have correlated HRV to lifestyle in the general population. We investigated 1418 men and 2040 women aged 40-74 years and measured the HRV indices in the time and frequency domains using a 5-min R-R interval recording. Multiple linear regression analyses were used to estimate the association between HRV and blood pressure levels after adjustment for major confounders. HRV indices were not associated with systolic blood pressure levels in men, whereas in women, one-s.d. (1-s.d.) increment of s.d. of normal R-R intervals (SDNN) was associated with a 1.21-mm Hg decrease in systolic blood pressure after adjusting for several confounders (P<0.05). In addition, a 1-s.d. increment of SDNN corresponded with 1.00 and 1.10 mm Hg reductions in diastolic blood pressure in men and women, respectively (P<0.05). When stratified by the use or nonuse of antihypertensive medication, these inverse associations were more evident in the nonuser group. Furthermore, among men not using antihypertensive medication, reduced HRV was associated with increased systolic blood pressure levels in nondrinkers. The data suggest that HRV reflects diastolic blood pressure better than systolic blood pressure levels for both sexes and that alcohol intake strongly affects systolic blood pressure levels in men, which may have weakened the association with HRV.

Drug-resistant hypertensive patients responding to multielectrode renal denervation exhibit improved heart rate dynamics and reduced arrhythmia burden

Transluminal renal sympathetic denervation (RDN) reduces blood pressure (BP) in patients with drug-resistant uncontrolled hypertension. We assessed the effect of RDN on heart rate, supraventricular and ventricular ectopic activity and indexes of heart rate variability in 14 patients with drug-resistant uncontrolled hypertension who were all responders to RDN (defined as a reduction in office systolic BP ⩾ 10 mm Hg) at baseline and at 1 and 6 months after the procedure using the multielectrode EnligHTN ablation catheter (St Jude Medical). Office and 24-h systolic and diastolic BP were significantly reduced both at 1 and 6 months after RDN and all patients were office BP responders. There was a trend toward office heart rate reduction (by 6.9 b.p.m., P=0.064) at 1 month and a significant reduction by 10 b.p.m. (P=0.004) at 6 months. Mean 24-h Holter monitoring heart rate was reduced by 6.7 b.p.m. (P=0.022) at 1 month and by 5.3 b.p.m. (P=0.010) at 6 months after RDN. The total number of premature supraventricular and ventricular contractions was significantly decreased and time- and frequency- domain indexes were increased both at 1 and at 6 months after RDN (P<0.05 for both cases). Apart from the substantial BP lowering, RDN results in significant reduction of mean heart rate and arrhythmia burden, restoring autonomic balance in responder patients with drug-resistant uncontrolled hypertension.

Very Long (> 48 hours) Shifts and Cardiovascular Strain in Firefighters: a Theoretical Framework

Shift work and overtime have been implicated as important work-related risk factors for cardiovascular disease (CVD). Many firefighters who contractually work on a 24-hr work schedule, often do overtime (additional 24-hr shifts) which can result in working multiple, consecutive 24-hr shifts. Very little research has been conducted on firefighters at work that examines the impact of performing consecutive 24-hr shifts on cardiovascular physiology. Also, there have been no standard field methods for assessing in firefighters the cardiovascular changes that result from 24-hr shifts, what we call “cardiovascular strain”. The objective of this study, as the first step toward elucidating the role of very long (> 48 hrs) shifts in the development of CVD in firefighters, is to develop and describe a theoretical framework for studying cardiovascular strain in firefighters on very long shifts (i.e., > 2 consecutive 24-hr shifts). The developed theoretical framework was built on an extensive literature review, our recently completed studies with firefighters in Southern California, e-mail and discussions with several firefighters on their experiences of consecutive shifts, and our recently conducted feasibility study in a small group of firefighters of several ambulatory cardiovascular strain biomarkers (heart rate, heart rate variability, blood pressure, salivary cortisol, and salivary C-reactive protein). The theoretical framework developed in this study will facilitate future field studies on consecutive 24-hr shifts and cardiovascular health in firefighters. Also it will increase our understanding of the mechanisms by which shift work or long work hours can affect CVD, particularly through CVD biological risk factors, and thereby inform policy about sustainable work and rest schedules for firefighters.

Associations between the autonomic nervous system and the second derivative of the finger photoplethysmogram indices

AIM

The indices of the second derivative of the finger photoplethysmogram(SDPTG) denote stiffness of large arteries, peripheral vascular resistance and vascular aging. However, the association between the autonomic nervous activity and the SDPTG indices has not yet been elucidated.

METHODS

The SDPTG and heart rate variability(HRV) were consecutively measured in the sitting position on the day before surgery in 168 patients 18-89 years of age. The relationships between the SDPTG indices(b/a, c/a, d/a and e/a) and HRV indices(power spectral analysis and time domain analysis parameters) were analyzed. The relationships between c/a and atherosclerosis-based conditions and risk factors for atherosclerosis were also evaluated.

RESULTS

The SDPTG index b/a was negatively associated and the d/a index was positively associated with the low-frequency(LF)(R=-0.44 and 0.42, respectively) and high-frequency(HF) components(R=-0.31 and 0.35, respectively). The SDPTG index c/a was also positively associated with the LF(R=0.40) and HF(R=0.44) components. A multivariate regression analysis showed that the LF, HF and heart rate were independent determinants of the c/a. Furthermore, the c/a values were significantly lower in the patients with hypertension, diabetes mellitus and hyperlipidemia than in those without these diseases, and a reduced c/a was significantly associated with increased serum triglyceride and total cholesterol concentrations.

CONCLUSIONS

These findings suggest that a decrease in c/a is associated with a reduced baroreflex response of the peripheral vasomotor activity and a decreased cardiac parasympathetic activity. Furthermore, a decrease in c/a was found to be associated with atherosclerosis-based conditions, such as hypertension, diabetes mellitus and hyperlipidemia.

Autonomic dysfunction in essential hypertension: A systematic review

Introduction

Greater sympathetic drive has been established in the early stages of essential hypertension, suggesting that neurohormonal dysregulation may be key to its aetiology and progression. The aims of this review are to discuss evidence of the role of autonomic dysfunction in essential hypertension and proposed mechanisms, and also some applications of this knowledge to current management strategies of essential hypertension.

Methods

A computer search was performed using the PUBMED database for peer reviewed original articles comparing autonomic function tested via heart rate variability (HRV), muscle sympathetic nerve activity (MSNA) or plasma noradrenaline levels in normotensive (mean blood pressure (BP) of ≤140/90 mmHg or ≤135/85 mmHg if measured via home BP measurements) and hypertensive groups (mean resting BP of ≥140/90 mmHg (or ≥135/85 mmHg if measured via home BP measurements). Subjects were excluded with secondary causes of hypertension or autonomic dysfunction.

Results

A total of 17 studies were included for discussion. The main findings of this study include that of reduced baroreflex sensitivity, believed to be secondary to increased arterial stiffness, is hypothesised to be implicated in the pathogenesis of essential hypertension. Also, angiotensin converting enzyme inhibitors were not as effective on markers of autonomic control of blood pressure when compared with alternative anti-hypertensive drugs.

Conclusions

Consistent research is needed to establish the effectiveness of pharmacotherapies at each of stage of hypertension, and on markers of autonomic dysfunction. Consistent study designs will enable more accurate accumulation of data across multiple studies, and appropriate application of such data into clinical practice.

Reduced heart rate variability is associated with worse cognitive performance in elderly Mexican Americans

Reduced heart rate variability is a strong predictor of cardiovascular risk factors, cardiovascular events, and mortality and thus may be associated with cognitive neurodegeneration. Yet, this has been relatively unexplored, particularly in minority populations with high cardiovascular burden. We used data from the Sacramento Area Latino Study on Aging to examine the cross-sectional association of reduced heart rate variability with cognitive function among elderly Mexican Americans. A total of 869 participants (mean age, 75 years; 59% women) had their 6-minute heart rate variability measured using an ECG monitor and respiration pacer in response to deep breathing. We used the mean circular resultant, known as R bar, as a measure of heart rate variability and categorized it into quartiles (Q1 to Q4 of R bar: reduced to high heart rate variability). Cognitive function was assessed using the modified Mini-Mental State Examination, a 100-point test of global cognitive function, and the Spanish and English verbal learning test, a 15-point test of verbal memory recall. In fully adjusted linear regression models, participants in quartile 1 had a 4-point lower modified Mini-Mental State Examination score (P<0.01), those in quartile 2 had a 2-point lower score (P=0.04), and those in quartile 3 had a 1-point lower score (P=0.35) compared with those in the highest quartile of R bar. Reduced R bar was not associated with verbal memory. Our results suggest that reduced heart rate variability is associated with worse performance on the test of global cognitive function, above and beyond traditional cardiovascular risk factors.

Heart rate variability on antihypertensive drugs in black patients living in sub-Saharan Africa

Background

Compared with Caucasians, African Americans have lower heart rate variability (HRV) in the high-frequency domain, but there are no studies in blacks born and living in Africa.

Methods

In the Newer versus Older Antihypertensive agents in African Hypertensive patients trial (NCT01030458), patients (30–69 years) with uncomplicated hypertension (140–179/90–109 mmHg) were randomized to single-pill combinations of bisoprolol/hydrochlorothiazide (R) or amlodipine/valsartan (E). 72 R and 84 E patients underwent 5-min ECG recordings at randomization and 8, 16 and 24 weeks. HRV was determined by fast Fourier transform and autoregressive modelling.

Results

Heart rate decreased by 9.5 beats/min in R patients with no change in E patients (− 2.2 beats/min). R patients had reduced total (− 0.13 ms²; p = 0.0038) and low-frequency power (− 3.6 nu; p = 0.057), higher high-frequency (+ 3.3 nu; p = 0.050) and a reduced low- to high-frequency ratio (− 0.08; p = 0.040). With adjustment for heart rate, these differences disappeared, except for the reduced low-frequency power in the R group (− 4.67 nu; p = 0.02). Analyses confined to 39 R and 47 E patients with HRV measurements at all visits or based on autoregressive modelling were confirmatory.

Conclusion

In native black African patients, antihypertensive drugs modulate HRV, an index of autonomous nervous tone. However, these effects were mediated by changes in heart rate except for low-frequency variability, which was reduced on beta blockade independent of heart rate.

Obesity in american Indian and mexican american men and women: associations with blood pressure and cardiovascular autonomic control

Obesity is a serious public health problem, especially in some minority communities, and it has been associated with an increased risk of cardiovascular diseases. While obesity is a serious health concern in both American Indian and Mexican American populations, the relationship between obesity and cardiac autonomic control in these two populations is not well understood. The present study in a selected sample of American Indians and Mexican Americans assessed associations between obesity, blood pressure (BP), and cardiovascular autonomic control. Cardiovascular autonomic control, systolic and diastolic mean BP, and body mass index were obtained from one hundred thirty-two American Indian and Mexican American men and women who are literate in English and are residing legally in San Diego County. Men had a significant greater systolic and diastolic BP and were more likely to develop systolic prehypertension and hypertension than women. Obese participants showed greater mean heart rate (HR) and systolic and diastolic BP than nonobese participants. Obese men also exhibited greater cardiac sympathetic activity and lower cardiovagal control than obese women. These results suggest that obesity and gender differences in cardiovascular autonomic control may contribute to risk for cardiovascular disorders in this sample of American Indians and Mexican Americans.

Dysfunctional brain-bone marrow communication: a paradigm shift in the pathophysiology of hypertension

It is widely accepted that the pathophysiology of hypertension involves autonomic nervous system dysfunction, as well as a multitude of immune responses. However, the close interplay of these systems in the development and establishment of high blood pressure and its associated pathophysiology remains elusive and is the subject of extensive investigation. It has been proposed that an imbalance of the neuro-immune systems is a result of an enhancement of the "proinflammatory sympathetic" arm in conjunction with dampening of the "anti-inflammatory parasympathetic" arm of the autonomic nervous system. In addition to the neuronal modulation of the immune system, it is proposed that key inflammatory responses are relayed back to the central nervous system and alter the neuronal communication to the periphery. The overall objective of this review is to critically discuss recent advances in the understanding of autonomic immune modulation, and propose a unifying hypothesis underlying the mechanisms leading to the development and maintenance of hypertension, with particular emphasis on the bone marrow, as it is a crucial meeting point for neural, immune, and vascular networks.

Predicting 7-day survival using heart rate variability in hospice patients with non-lung cancers

BACKGROUND

A simple and accurate survival prediction tool can facilitate decision making processes for hospice patients with advanced cancers. The objectives of this study were to explore the association of cardiac autonomic functions and survival in patients with advanced cancer and to evaluate the prognostic value of heart rate variability (HRV) in 7-day survival prediction.

METHODS

A prospective study was conducted on 138 patients with advanced cancer recruited from the hospice ward of a regional hospital in southern Taiwan. Information on functional status and symptom burden of the patients was recorded. Frequency-domain HRV was obtained for the evaluation of cardiac autonomic functions at admission. The end point of the study was defined as the survival status at day 7 after admission to the hospice ward. Multivariate logistic regression analyses were performed to evaluate the independent associations between HRV indices and survival of 7 days or less.

RESULTS

The median survival time of the patients was 20 days (95% CI, 17-28 days). Results from the multivariate logistic regression analysis indicated that the natural logarithm-transformed high-frequency power (lnHFP) of a value less than 2 (OR = 3.8, p = 0.008) and ECOG performance status of 3 or 4 (OR = 3.4, p = 0.023) were significantly associated with a higher risk of survival of 7 days or less. Receiver operating characteristic (ROC) curve analysis revealed that the area under the curve was 0.71 (95% CI, 0.61-0.81).

CONCLUSIONS

In hospice patients with non-lung cancers, an lnHPF value below 2 at hospice admission was significantly associated with survival of 7 days or less. HRV might be used as a non-invasive and objective tool to facilitate medical decision making by improving the accuracy in survival prediction.

Age-related changes in cerebral hemodynamics and their correlations with cardiac autonomic functions

OBJECTIVES

This study was designed to evaluate the correlations between cerebral hemodynamics and cardiac autonomic functions in aging process using transfer function techniques.

METHODS

Arterial blood pressure (ABP), middle cerebral artery flow velocity (MCAFV) detected by transcranial Doppler sonography and electrocardiogram were recorded simultaneously in 20 young (27.5 +/- 0.9 years) and 20 middle-old-aged (54.3 +/- 1.5 years) healthy volunteers. Variability of ABP, MCAFV and heart rate (HR) were diffracted into very low (VLF, 0.016-0.04 Hz), low (LF, 0.04-0.15 Hz) and high frequency (HF, 0.15-0.4 Hz) components. Cerebral vasomotor reserve was quantified by specific ABP-MCAFV transfer function measurements.

RESULTS

The young group had significantly higher LF transfer phase and HF transfer magnitudes of ABP-MCAFV transfer function; higher HF powers of HR variability; and higher baroreflex sensitivity than those of the middle-old-aged group. LF phase and HF magnitude of ABP-MCAFV transfer function were positively correlated with HF powers of HR variability.

DISCUSSION

Although aging process is not obviously associated with changes in the static values of ABP, MCAFV and HR in this study, it is accompanied by significant declines in cerebral vasomotor reserve, cardiac vagal activity and baroreflex sensitivity. Besides, age-related changes in cerebral vasomotor reserve are positively related to those in cardiac vagal activity.

Impaired baroreflex sensitivity and the risks of new-onset ambulatory hypertension, in an elderly population-based study

BACKGROUND

Impairment of the autonomic nervous system activity may be involved in the development of hypertension. Yet the prognostic values of heart rate variability and baroreflex sensitivity in the risk of new-onset ambulatory hypertension have not been investigated. We sought to assess the relationship between heart rate variability and baroreflex sensitivity parameters and ambulatory hypertension in a community-dwelling elderly cohort.

METHODS

Normotensive subjects were selected from the PROOF study cohort, including 1011 subjects aged 65 years at baseline. The autonomic nervous system activity was assessed through 24-hour heart rate variability and 15-minute spontaneous baroreflex sensitivity at baseline. Incident hypertension was defined with the 24-hour, day-time and night-time ambulatory blood pressure measurements and antihypertensive treatment use, at two-years of follow-up.

RESULTS

At baseline, 13.7% of subjects developed day-time hypertension, 18.2% developed night-time hypertension and 13.6% developed 24-hour hypertension. Reduced baroreflex sensitivity at baseline was associated with onset of hypertension after adjustment for blood pressure level, C-reactive protein levels and depression score (OR = 0.45 [0.23-0.86]). Indices of heart rate variability were not associated with hypertension onset.

CONCLUSION

Baroreflex sensitivity may represent an intermediate goal for prevention of ambulatory hypertension at early stage.

Dysregulation of the autonomic nervous system predicts the development of the metabolic syndrome

CONTEXT

Stress is suggested to lead to metabolic dysregulations as clustered in the metabolic syndrome. Although dysregulation of the autonomic nervous system is found to associate with the metabolic syndrome and its dysregulations, no longitudinal study has been performed to date to examine the predictive value of this stress system in the development of the metabolic syndrome.

OBJECTIVE

We examined whether autonomic nervous system functioning predicts 2-year development of metabolic abnormalities that constitute the metabolic syndrome.

DESIGN

Data of the baseline and 2-year follow-up assessment of a prospective cohort: the Netherlands Study of Depression and Anxiety was used.

SETTING

Participants were recruited in the general community, primary care, and specialized mental health care organizations.

PARTICIPANTS

A group of 1933 participants aged 18-65 years.

MAIN OUTCOME MEASURES

The autonomic nervous system measures included heart rate (HR), respiratory sinus arrhythmia (RSA; high RSA reflecting high parasympathetic activity), pre-ejection period (PEP; high PEP reflecting low sympathetic activity), cardiac autonomic balance (CAB), and cardiac autonomic regulation (CAR). Metabolic syndrome was based on the updated Adult Treatment Panel III criteria and included high waist circumference, serum triglycerides, blood pressure, serum glucose, and low high-density lipoprotein (HDL) cholesterol.

RESULTS

Baseline short PEP, low CAB, high HR, and CAR were predictors of an increase in the number of components of the metabolic syndrome during follow-up. High HR and low CAB were predictors of a 2-year decrease in HDL cholesterol, and 2-year increase in diastolic and systolic blood pressure. Short PEP and high CAR also predicted a 2-year increase in systolic blood pressure, and short PEP additionally predicted 2-year increase in diastolic blood pressure. Finally, a low baseline RSA was predictive for subsequent decreases in HDL cholesterol.

CONCLUSION

Increased sympathetic activity predicts an increase in metabolic abnormalities over time. These findings suggest that a dysregulation of the autonomic nervous system is an important predictor of cardiovascular diseases and diabetes through dysregulating lipid metabolism and blood pressure over time.

Effects of omega-3 fatty acid supplementation on heart rate variability at rest and during acute stress in adults with moderate hypertriglyceridemia

OBJECTIVE

This study examined the dose-dependent effects of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) supplementation on heart rate variability (HRV) at rest and during standard laboratory stress tasks. We also investigated whether EPA + DHA supplementation was associated with changes in mood state.

METHODS

This placebo-controlled, double-blind, randomized, three-period crossover trial (8-week treatment, 6-week washout) compared two doses of EPA + DHA supplementation (0.85 and 3.4 g/d) in 26 adults with elevated triglycerides. After each treatment period, HRV was assessed during an acute stress protocol that included a resting baseline, standard laboratory stress tasks (speech task and cold pressor), and recovery periods. In addition, mood state was assessed.

RESULTS

Root mean square of successive differences in interbeat interval and total power increased 9.9% and 20.6%, respectively, after the high dose relative to placebo (Tukey p = .016 and .012, respectively). The low dose was not significantly different from the high dose or placebo dose. There was a trend for a treatment effect on high-frequency HRV (p = .058), with 21.0% greater power observed after the high dose compared with placebo (Tukey p = .052). Mood did not differ between treatments, and there was no association between mood state and HRV.

CONCLUSIONS

In healthy adults with elevated triglycerides, supplementation of 3.4 g/d EPA + DHA resulted in greater HRV, whereas 0.85 g/d EPA + DHA had no effect. These results indicate that EPA + DHA supplementation may improve autonomic tone in adults at increased risk for cardiovascular disease within 8 weeks.

TRIAL REGISTRATION

NCT00504309 (ClinicalTrials.gov).

Effects of isometric handgrip training dose on resting blood pressure and resistance vessel endothelial function in normotensive women

Isometric handgrip (IHG) training lowers resting blood pressure (BP) in both hypertensives and normotensives, yet the effect of training dose on the magnitude of reduction and the mechanisms associated with the hypotensive response are elusive. We investigated, in normotensive women, the effects of two different doses of IHG training on resting BP, and explored improved resistance vessel endothelial function and heart rate variability (HRV) as potential mechanisms of BP reduction. Resting BP, HRV, and resistance vessel endothelial function (venous strain-gauge plethysmography with reactive hyperemia) were assessed in 32 women before and after 4 and 8 weeks of 3×/week (n = 12) or 5×/week (n = 11) IHG training (four, 2-min unilateral contractions at 30 % maximal voluntary contraction), or 0×/week control (n = 9). IHG training decreased systolic BP in the 3×/week (94 ± 6 to 91 ± 6 to 88 ± 5 mmHg, pre- to mid- to post-training; P < 0.01) and 5×/week (97 ± 11 to 90 ± 9 to 91 ± 9 mmHg, P < 0.01) groups, concomitant with increased forearm reactive hyperemic blood flow (26 ± 7 to 30 ± 8 to 36 ± 9 mL/min/100 mL tissue, P < 0.01; and 26 ± 7 to 29 ± 7 to 38 ± 13 mL/min/100 mL tissue, P < 0.01, respectively), yet both remained unchanged in the control group. No changes were observed in diastolic BP, mean arterial BP, or any indices of HRV in any group (all P > 0.05). In conclusion, IHG training lowers resting systolic BP and improves resistance vessel endothelial function independent of training dose in normotensive women.

Gender differences in cardiac autonomic modulation during medical internship

Medical internship is known to be a time of high stress and long working hours, which increases the risk of depression and cardiovascular disease. Gender differences in medical interns' cardiovascular risk have not been reported previously. Thirty-eight medical interns (29 males) were repeatedly tested for depressive symptoms using the Hospital Anxiety and Depression Scale and 5-min spectral analysis of heart rate variability (HRV) at 3-month intervals during their internship. Among the male interns, the variance of the heart rate decreased at 6, 9, 12 months, and a reduced high frequency, which suggests reduced cardiac parasympathetic modulation, was found at 9 and 12 months into their internship. Increased depressive symptoms were also identified at 12 months in the male group. No significant differences in depression or any of the HRV indices were identified among the female interns during their internship.

Heart rate variability today

Heart rate variability (HRV) non-invasively assesses the activity of the autonomic nervous system. During the past 30 years, an increasing number of studies have related the imbalance of the autonomic nervous system (as assessed by HRV) to several pathophysiogical conditions, particularly in the setting of cardiovascular disease. Sudden death, coronary artery disease, heart failure, or merely cardiovascular risk factors (smoking, diabetes, hyperlipidemia, and hypertension) are the best-known clinical circumstances that can affect and/or be affected by the autonomic nervous system. Analyses of HRV variables have been proposed as a component of the clinical evaluation for patient risk stratification due to its independent prognostic information. Yet the potential for HRV to be used widely in clinical practice remains to be established.

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.

Hypertension in women: latest findings and clinical implications

Cardiovascular disease claims more women's lives than any other disease. Hypertension is an important risk factor for cardiovascular disease in women but is often underestimated and undiagnosed and there is an ongoing misperception that women are at a lower risk of cardiovascular disease than men. The attainment of clinical blood pressure goals can markedly reduce cardiovascular morbidity and mortality, yet approximately two-thirds of treated hypertensive women have uncontrolled blood pressure. Furthermore, there are special risk factors that are unique for women that needs acknowledgement in order to help prevent the great number of hypertension-related events in women. Guidelines for treatment of hypertension are similar for men and women. More studies on the interaction between gender and response to antihypertensive drugs would be of interest.

Cardiovascular-sleep interaction in drug-naïve patients with essential grade I hypertension

Lack of nighttime blood pressure (BP) reduction by 10-20% from the mean daytime values (dipping) has been described as a distinguishing feature of essential hypertension and associated, also in normotensive subjects, with increased cardiovascular (CV) risk. Mechanisms involved in the loss of the nocturnal dip are still unclear, but involvement of autonomic nervous system (ANS) activity probably plays a crucial role. Sleep is fundamental in modulating ANS activity to maintain the physiological BP circadian rhythm, and for this reason its integrity has been widely investigated in hypertension. We investigated, under controlled conditions, the autonomic control of the CV system through an autonomic reflex screen in the awake condition and by assessment of circadian rhythm-, day-night-, time-, and state-dependent changes of BP and heart rate (HR) and associated sleep parameters in patients with a recent (≤1 yr) diagnosis of essential grade I hypertension naïve of therapy. Fourteen hypertensive patients (6 males, age: 43 ± 11 yrs; body mass index [BMI]: 24 ± 3 kg/m(2)) were compared with 28 healthy controls matched for sex, age, BMI (2 controls/patient) for cardiovascular reflex and to 8 different subjects from previous controls (6 males), comparable for age and BMI, for the day-night and nighttime CV profiles during two consecutive nights. The cardiovascular reflex screen data showed increased sympathetic effect in hypertensive patients, represented by higher overshoot of BP after Valsalva maneuver. Nighttime sleep architecture during the dark period in terms of duration, representation of sleep stages, sleep fragmentation, and incidence of arousals-periodic limb movements in sleep (PLMS) and PLMS arousals-was similar in patients and controls. Hypertensive patients displayed higher 24-h BP and HR values, but their sleep-related BP decrease was significantly reduced compared with controls. The circadian rhythms of BP and HR were intact and similar in patients and controls, coupling with the expected physiological peak time. BP and HR showed normal state-dependent modulation in hypertensive patients that, however, was higher in all sleep stages compared with controls. The lowering of systolic blood pressure (SBP) during non-rapid eye movement (NREM) sleep stages 1 and 2 and REM sleep, relative to daytime wake values, was significantly attenuated in the hypertensive group, whereas it was comparable to controls during slow-wave sleep. In hypertensive patients, analysis of sleep and CV parameters in the 90 min following sleep onset and preceding morning awakening showed normal depressor effect during the first part of the night after sleep onset and significantly higher BP rise in the hours preceding morning awakening. These findings were associated with comparable sleep architecture, sleep fragmentation, incidence of arousals, and PLMS and PLMS arousals in patients and controls. Our data suggest that drug-naïve essential grade I hypertension is associated with signs of increased vascular sympathetic response to standardized stress of the Valsalva maneuver during the awake condition, and during sleep with a non-dipping BP profile plus higher BP surge preceding morning awakening, assessable only by around-the-clock ambulatory BP monitoring, both representing additional CV risk already in early-stage hypertension and, therefore, requiring proper selection of pharmacological treatment.

Cardio-pulmonary fitness test by ultra-short heart rate variability

Objectives:

It is known that exercise induces cardio-respiratory autonomic modulation. The aim of this study was to assess the cardio-pulmonary fitness by ultra-short heart rate variability.

Materials and Methods:

Study population was divided into 3 groups: Group-1 (n = 40) consisted of military sports man. Group-2 (n = 40) were healthy age-matched sedentary male subjects with normal body mass index [BMI = 19 - 25 kg/m²). Group-3 (n = 40) were healthy age-matched obese male subjects [BMI > 29 kg/m²). Standard deviation of normal-to-normal QRS intervals (SDNN) was recorded over 15 minutes. Bruce protocol treadmill test was used; and, maximum oxygen consumption (VO₂max) was calculated.

Results:

When the study population was divided into quartiles of SDNN (first quartile: < 60 msec; second quartile: > 60 and < 100 msec; third quartile: > 100 and <140 msec; and fourth quartile: >140 msec), progressive increase was found in VO₂max; and, SDNN was significantly linked with estimated VO₂max.

Conclusion:

In conclusion, the results of this study demonstrate that exercise training improves cardio-respiratory autonomic function (and increases heart rate variability). Improvement in cardio-respiratory autonomic function seems to translate into a lower rate of long term mortality. Ultra-short heart rate variability is a simple cardio-pulmonary fitness test which just requires 15 minutes, and involves no exercise such as in the treadmill or cycle test.

Diabetic autonomic imbalance and glycemic variability

Diabetic autonomic neural imbalance is a severe complication of long-term diabetes patients and may progress to diabetic autonomic neuropathy (DAN). The prevalence of DAN is reported to be between 20 and 70%, depending on the studies. The pathogenesis of DAN remains unresolved. However, emerging evidence suggests that glycemic variability (GV) may be associated with autonomic imbalance in patients with both type 1 and type 2 diabetes. As symptoms are initially weak and uncharacteristic, the condition often remains undiagnosed until late manifestations present themselves. Predominant symptoms may include nausea, vomiting, gastroparesis, involuntary diarrhea, postural hypotension, voiding difficulties, and sexual dysfunction. Analyzing the patterns of heart rate variability carries the potential for detection of autonomic imbalance in the subclinical and asymptomatic stages. In this context, GV may affect the sympathovagal balance by increasing oxidative stress and proinflammatory cytokines. Establishing a GV risk profile could therefore be important in determining risk factors in diabetes patients. This review addresses the issues above and in particular the possible association between diabetic autonomic imbalance and GV.

Body mass index contributes to sympathovagal imbalance in prehypertensives

BACKGROUND

The present study was conducted to assess the nature of sympathovagal imbalance (SVI) in prehypertensives by short-term analysis of heart rate variability (HRV) to understand the alteration in autonomic modulation and the contribution of BMI to SVI in the genesis of prehypertension.

METHODS

Body mass index (BMI), basal heart rate (BHR), blood pressure (BP), rate pressure product (RPP) and HRV indices such as total power (TP), low-frequency power (LF), normalized LF (LFnu), high-frequency power (HF), normalized HF (HFnu), LF-HF ratio, mean heart rate (mean RR), square root of the mean squared differences of successive normal to normal intervals (RMSSD), standard deviation of normal to normal RR interval (SDNN), the number of interval differences of successive NN intervals greater than 50 ms (NN50) and the proportion derived by dividing NN50 by the total number of NN intervals (pNN50) were assessed in three groups of subjects: normotensives having normal BMI (Group 1), prehypertensives having normal BMI (Group 2) and prehypertensives having higher BMI (Group 3). SVI was assessed from LF-HF ratio and correlated with BMI, BHR, BP and RPP in all the groups by Pearson correlation. The contribution of BMI to SVI was assessed by multiple regression analysis.

RESULTS

LF and LFnu were significantly increased and HF and HFnu were significantly decreased in prehypertensive subjects in comparison to normotensive subjects and the magnitude of these changes was more prominent in subjects with higher BMI compared to that of normal BMI. LF-HF ratio, the sensitive indicator of sympathovagal balance had significant correlation with BMI (P=0.000) and diastolic blood pressure (DBP) (P=0.002) in prehypertensives. BMI was found to be an independent contributing factor to SVI (P=0.001) in prehypertensives.

CONCLUSIONS

It was concluded that autonomic imbalance in prehypertensives manifested in the form of increased sympathetic activity and vagal inhibition. In prehypertensives with higher BMI, vagal withdrawal was predominant than sympathetic overactivity. Magnitude of SVI (alteration in LF-HF ratio) was linked to changes in BMI and DBP. BMI had an independent influence on LF-HF ratio. It was advised that life-style modifications such as yoga and exercise would enable achieve the sympathovagal balance and blood pressure homeostasis in prehypertensives.

Etiopathogenetic mechanisms of pulmonary hypertension in sleep-related breathing disorders

Obstructive sleep apnea syndrome is a common disorder with significant health consequences and is on the rise in consonance with the obesity pandemic. In view of the association between sleep-disordered breathing and pulmonary hypertension as depicted by multiple studies, current clinical practice guidelines categorize obstructive sleep apnea as a risk factor for pulmonary hypertension and recommend an assessment for sleep disordered breathing in evaluating patients with pulmonary hypertension. The dysregulatory mechanisms associated with hypoxemic episodes observed in sleep related breathing disorders contribute to the onset of pulmonary hypertension and identification of these potentially treatable factors might help in the reduction of overall cardiovascular mortality.

Heart rate variability in association with frequent use of household sprays and scented products in SAPALDIA

BACKGROUND

Household cleaning products are associated with adverse respiratory health outcomes, but the cardiovascular health effects are largely unknown.

OBJECTIVE

We determined if long-term use of household sprays and scented products at home was associated with reduced heart rate variability (HRV), a marker of autonomic cardiac dysfunction.

METHODS

We recorded 24-hr electrocardiograms in a cross-sectional survey of 581 Swiss adults, ≥ 50 years of age, who answered a detailed questionnaire regarding their use of household cleaning products in their homes. The adjusted average percent changes in standard deviation of all normal-to-normal intervals in 24 hr (24-hr SDNN) and total power (TP) were estimated in multiple linear regression in association with frequency [< 1, 1-3, or 4-7 days/week, unexposed (reference)] of using cleaning sprays, air freshening sprays, and scented products.

RESULTS

Decreases in 24-hr SDNN and TP were observed with frequent use of all product types, but the strongest reductions were associated with air freshening sprays. Compared with unexposed participants, we found that using air freshening sprays 4-7 days/week was associated with 11% [95% confidence interval (CI): -20%, -2%] and 29% (95% CI: -46%, -8%) decreases in 24-hr SDNN and TP, respectively. Inverse associations of 24-SDNN and TP with increased use of cleaning sprays, air freshening sprays, and scented products were observed mainly in participants with obstructive lung disease (p < 0.05 for interactions).

CONCLUSIONS

In predominantly older adult women, long-term frequent use of household spray and scented products was associated with reduced HRV, which suggests an increased risk of cardiovascular health hazards. People with preexisting pulmonary conditions may be more susceptible.

Impairment on cardiovascular and autonomic adjustments to maximal isometric exercise tests in offspring of hypertensive parents

The objective of the present study was to compare cardiovascular and autonomic responses to a mental stress test and to a maximal isometric exercise test between offspring of normotensive (ON, n = 10) and hypertensive parents (OH, n = 10). Subjects underwent a 3-min Stroop Color Word Test and a maximal isometric exercise test performed in an isokinetic dynamometer with continuous RR interval monitoring. At rest, arterial pressure and heart rate were similar between groups, but there was a significant reduction in total RR interval variance (ON: 5933 ± 493 vs. OH: 2967 ± 390 ms(2)) and an increase in low-high frequency components ratio of heart rate variability (ON: 2.3 ± 0.4 vs. OH: 4.6 ± 0.8) in OH group. In the first minute of the mental stress test and after both tests, the OH group presented increased heart rate as compared with the ON group. After both tests, only the ON group presented an increase in sympathetic component, thus reaching resting values similar to those of the OH group. Our data demonstrated increased resting cardiac sympathetic modulation in offspring of hypertensive parents at similar levels to that observed in offspring of normotensive parents after a mental stress test or a maximal isometric exercise test. Additionally, the exacerbated heart rate responses to these physiological tests in OH subjects may be associated with resting autonomic dysfunction, thus reinforcing these evaluations as important tools for detecting early dysfunctions in this genetically predisposed population.