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From National Heart, Lung, and Blood Institute's Framingham Heart
Study, Framingham, Mass (J.P.S., M.G.L., H.T., J.C.E., C.J.O., D.L.); the
National Heart, Lung, and Blood Institute, Bethesda, Md (C.J.O., D.L.); the
Division of Epidemiology and Preventive Medicine, Boston University School of
Medicine, Boston, Mass (J.P.S., M.G.L., J.C.E., D.L.); the Divisions of
Cardiology and Clinical Epidemiology, Beth Israel Hospital, Boston, Mass
(D.L.); the Cardiac Unit, Department of Medicine, Massachusetts General
Hospital, Harvard Medical School, Boston, Mass (C.J.O.); and Kansai Medical
University, Osaka, Japan (H.T.).
Although previous studies from Framingham6 and
elsewhere7 8 9 10 11 have identified abnormal HRV in
systemic hypertension, there is a paucity of data examining the
association between HRV and blood pressure. Also, even though
sympathetic nervous system overactivity has been demonstrated in early
hypertension,1 2 little is known about the impact
of altered HRV on the development of new-onset hypertension. The
purpose of this study was to (1) compare the measures of HRV in
Framingham Heart Study subjects with and those without hypertension and
(2) assess the role of HRV as a predictor of new-onset hypertension
during 4 years of follow-up.
Subjects for the present study were original Framingham Heart Study
participants and Offspring Study subjects who underwent ambulatory ECG
recordings between 1983 and 1987 during a routine scheduled
examination at the Framingham Heart Study clinic. Subjects were
excluded if they met any of the following criteria: (1) history or
clinical evidence of myocardial infarction or congestive heart failure,
(2) atrial fibrillation, (3) diabetes mellitus, (4) use of
antihypertensive or cardioactive medication at the index examination,
and (5) technically inadequate ambulatory ECG recordings. The
diagnoses of myocardial infarction and congestive heart failure were
established by a committee of 3 physicians who evaluated records
from the Framingham Heart Study clinic examinations, interim
hospitalizations, and visits to personal physicians in accordance with
published criteria.15 At the index examination,
body height and weight measurements, medical history, physical
examination, and 12-lead resting and ambulatory ECG results were
routinely obtained.
Blood Pressure Measurements
HRV Assessment
Because clinic examinations typically lasted for 2 to 3 hours, only the
first 2 hours of data were analyzed for HRV. The time-domain
variables measured were the standard deviation of normal RR
intervals (2-hour SDNN), percentage of differences between adjacent
normal RR intervals exceeding 50 milliseconds (pNN50), and the square
root of the mean of squared differences between adjacent normal RR
intervals (r-MSSD). The frequency domain variables included total
power (TP, 0.01 to 0.40 Hz), high frequency power (HF, 0.15 to 0.40
Hz), low frequency power (LF, 0.04 to 0.15 Hz), very low frequency
power (0.01 to 0.04 Hz), and LF/HF ratio. Further details of HRV
assessment have been outlined in a previous
report.6
Follow-up
Statistical Analysis
The principal outcome, incident hypertension, was coded as no/yes and
was analyzed with logistic regression
models.18 Each of the 4 selected HRV
variables was assessed separately and adjusted for age, body mass
index, cigarette smoking, and alcohol consumption, as well as baseline
systolic and diastolic blood pressures. Heart rate
did not enter the model. Results are summarized by OR and 95%
confidence interval, with the OR expressed for a 1-SD decrement in the
log-transformed HRV variable. In addition, HRV measures were
compared between subjects who developed hypertension and those who
remained normotensive at the 4-year follow-up examination. An
association was considered statistically significant at a value of
P<0.05. All analyses were done on a Sparcstation 2
(SUN Microsystems) using the Statistical Analysis System
(SAS).19
Clinical and HRV Characteristics
Progression to Hypertension
On the basis of this model, crude probabilities of progression to
hypertension as a function of LF are displayed in Figure 1
Change in Blood Pressure
Because changes in blood pressure affect autonomic tone and vice versa,
HRV measures differ in hypertensive subjects when compared with those
with normal blood pressure. Our findings of reduced HRV in systemic
hypertension concur with results from 3 recently published
population-based studies.6 7 11 These studies
were either restricted to men7 or examined HRV in
men and women pooled together6 11 and included
subjects on a variety of cardioactive
medications.6 7 In contrast, our study included a
larger population-based sample in which referral bias was inherently
minimal. We examined the association between HRV and blood pressure
separately in healthy middle-aged men and women free from the
confounding effects of cardioactive medications.
The absence of a difference in the LF/HF ratio between normotensive and
hypertensive individuals could be explained by variable
responsiveness of the neural regulatory mechanisms between
individuals20 and the fact that the LF/HF ratio
correlated poorly with other HRV measures.6
Predictors of Hypertension
Gender differences in baseline HRV,6 22 hormonal
changes accompanying essential hypertension,23
and cyclic changes of HRV observed in women24 may
help explain the poorer predictive value of HRV in women. The weak
relation observed between HRV and diastolic blood pressure
as opposed to systolic blood pressure (Figure 2
Strengths and Limitations
This study was based on intermediate-duration recordings, which
yield different values for SDNN than shorter or longer
recordings. The recordings were obtained when subjects
underwent an extensive clinical evaluation and are not
representative of basal resting conditions. Such
activity can precipitate short-term changes in the autonomic tone that
can confound the relation of autonomic tone to resting blood pressure
measurements. It is uncertain in which direction this would have biased
our results.
Clinical Implications
Conclusions
Received January 12, 1998;
first decision February 4, 1998;
accepted March 12, 1998.
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Kaplan NM, ed. Clinical Hypertension. Baltimore, Md:
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6.
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MG, Feldman CL, Levy D. Determinants of heart rate variability.
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Materson BJ, Myerburg RJ. Alterations in heart rate variability and its
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10.
Guzzetti S, Piccaluga E, Casati R, Cerutti S, Lombardi
F, Pagani M, Malliani A. Sympathetic predominance in essential
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11.
Liao D, Cai J, Barnes RW, Tyroler AH, Rautaharju P,
Holme I, Heiss G. Association of cardiac autonomic function and the
development of hypertension. Am J Hypertens. 1996;9:11471156.[Medline]
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12.
Dawber TR, Meadors GF, Moore FE. Epidemiologic
approaches to heart disease: the Framingham study. Am J
Public Health. 1951;41:279286.
13.
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longitudinal studies in a community: the Framingham study. Ann
N Y Acad Sci. 1963;107:539556.
14.
Kannel WB, Feinleib M, McNamara PM, Garrison RJ,
Castelli WP. An investigation of coronary heart disease in
families: the Framingham Offspring study. Am J
Epidemiol. 1979;110:281290.
15.
Sorlie P. Cardiovascular Disease
and Death Following Myocardial Infarction and Angina Pectoris:
Framingham Study, 20-Year Follow-up. Washington, DC: US Government
Printing Office; 1977.
16.
Fifth Report of the Joint National Committee on
Detection, Evaluation, and Treatment of High Blood Pressure (JNC-V).
Arch Intern Med. 1993;153:154183.
17.
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Regression Analysis and Other Multivariable Methods.
Boston, Mass: PWS-Kent; 1988:102162.
18.
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Regression. New York, NY: John Wiley & Sons Inc; 1989:25134.
19.
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SAS Institute Inc; 1989;10711126,13511456.
20.
Malliani A, Pagani M, Furlan R, Guzzetti S, Lucini D,
Montana N, Cerutti S, Mela GS. Individual recognition by heart rate
variability of two different autonomic profiles related to posture.
Circulation. 1997;96:41434145.
21.
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22.
Ryan SM, Goldberger AL, Pincus SM, Mietus J, Lipsitz
LA. Gender- and age-related differences in heart rate dynamics: are
women more complex than men? J Am Coll Cardiol. 1994;24:17001707.[Abstract]
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hormones are altered in essential hypertension. J
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Sato N, Miyake S, Akatsu J, Kumashiro M. Power spectral
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MG, Feldman CL, Levy D. Reduced heart rate variability and mortality
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© 1998 American Heart Association, Inc.
Scientific Contributions
Reduced Heart Rate Variability and New-Onset Hypertension
Insights Into Pathogenesis of Hypertension: The Framingham Heart Study
![]()
Abstract
Top
Abstract
Introduction
Methods
Results
Discussion
References
AbstractHeart rate variability
(HRV) is a useful noninvasive tool to assess cardiac autonomic
function. The purpose of this study was to (1) compare measures of HRV
between hypertensive and normotensive subjects and (2) examine the role
of HRV as a predictor of new-onset hypertension. The first 2 hours of
ambulatory ECG recordings obtained from 931 men and 1111 women
attending a routine examination at the Framingham Heart Study were
processed for HRV. Three time-domain and 5 frequency-domain
variables were studied: standard deviation of normal RR intervals
(SDNN), percentage of differences between adjacent normal RR intervals
exceeding 50 milliseconds, square root of the mean of squared
differences between adjacent normal RR intervals, total power (0.01 to
0.40 Hz), high frequency power (HF, 0.15 to 0.40 Hz), low frequency
power (LF, 0.04 to 0.15 Hz), very low frequency power (0.01 to 0.04
Hz), and LF/HF ratio. On cross-sectional analysis, HRV was
significantly lower in hypertensive men and women. Among 633 men and
801 women who were normotensive at baseline (systolic blood
pressure <140 mm Hg and diastolic blood pressure
<90 mm Hg and not receiving antihypertensive treatment), 119 men
and 125 women were newly hypertensive at follow-up 4 years later. After
adjustment for factors associated with hypertension, multiple logistic
regression analysis revealed that LF was associated with
incident hypertension in men (odds ratio per SD decrement [OR], 1.38;
95% confidence interval [CI], 1.04 to 1.83) but not in women (OR,
1.12; 95% CI, 0.86 to 1.46). SDNN, HF, and LF/HF were not associated
with hypertension in either sex. HRV is reduced in men and women with
systemic hypertension. Among normotensive men, lower HRV was associated
with greater risk for developing hypertension. These findings are
consistent with the hypothesis that autonomic dysregulation is
present in the early stage of hypertension.
Key Words: heart rate hypertension, essential Framingham Heart Study autonomic nervous system pathogenesis
![]()
Introduction
Top
Abstract
Introduction
Methods
Results
Discussion
References
There is considerable
evidence to suggest that the autonomic nervous system plays an
important role in blood pressure regulation and in the development of
hypertension.1 2 Spectral analysis of HRV
can partially distinguish parasympathetic from sympathetic influences
on the heart3 4 and may provide important
insights into the role of the autonomic nervous system in the
pathogenesis of essential hypertension.5
![]()
Methods
Top
Abstract
Introduction
Methods
Results
Discussion
References
Subjects
The Framingham Heart Study is a prospective epidemiological
study established in 1948 to evaluate potential risk factors for
coronary heart disease. The original cohort included 5209 men
and women aged 28 to 62 years. In 1971, 5124 additional subjects were
entered into the Framingham Offspring Study. Study design and selection
criteria have been published.12 13 14
At each routine examination, blood pressure was measured in the
left arm twice, with the subject in the seated position, by the
examining physician using a mercury column sphygmomanometer. The
averaged values were then used to derive the respective examination
systolic and diastolic blood pressures. The index
examination was the one performed at the time of the ambulatory ECG
recording.
The first 2 hours of ambulatory ECG recordings were
processed for HRV. All ambulatory recordings included 2
channels of ECG information and were obtained on standard 4-track
cassette tapes with the use of either a Cardiodata PR2 or PR3 pace
recorder (Cardiodata Corp). The tape speed was 1 mm/s, and 1
channel was used to record a 32-Hz crystal-controlled timing track.
For analysis, the tapes were played back at 120 times real time
on the Cardiodata/Mortara Mk5 Holter analysis system (Mortara
Instrument Co), sampling each ECG channel at 180 samples per second.
Beat-to-beat RR interval data were obtained from the "beat stream
file." A linearly interpolated beat was substituted for intervals of
ectopic beats or artifact
2 RR intervals. The fast Fourier transform
was calculated on 100-second blocks of RR interval data. A continuous
curve was formed by linear interpolation between RR intervals; this was
subjected to a Hamming window and resampled at 1.28 times per second.
If there was a run of arrhythmia or artifact >1 beat long, the
100-second block was terminated, the partial block was discarded, and a
new block was started at the end of the usable period. Power density
spectrum was estimated by taking the sum of the squares of the
magnitude of the fast Fourier transform performed on all usable
100-second blocks. The resulting 100-second power spectra were
corrected for attenuation resulting from sampling and the Hamming
window and were averaged. Recordings with transient or
persistent nonsinus rhythm, premature beats >10% of beats, <1 hour
of recording time, or processed time <50% of recorded
time were excluded.
Blood pressure level measured 4 years after the index
examination was used to identify incident hypertension. New-onset
hypertension was defined as systolic blood pressure
140
mm Hg, diastolic blood pressure
90 mm Hg, or use
of antihypertensive medications on follow-up in a subject who was
normotensive at the index examination.16 Subjects
who developed congestive heart failure or who had a history of
myocardial infarction at the follow-up examination were
excluded.
All statistical analyses were gender specific. Measures
of HRV were natural-log transformed because their distributions were
highly skewed. Linear regression analyses were used to estimate
and test the strengths of associations between blood pressure
measurements and 4 preselected variables considered to be most
physiologically linked to blood pressure: LF,
HF, LF/HF ratio, and 2-hour SDNN. Multivariable regression
analysis was used to evaluate these relations after adjustment
for clinical covariates (age, gender, body mass index, alcohol
consumption, and cigarette smoking) that could affect autonomic
function.17 With the use of linear regression
analysis, age-adjusted increments in blood pressure were
estimated for 1-SD increments in the HRV measures.
![]()
Results
Top
Abstract
Introduction
Methods
Results
Discussion
References
Subjects Selected
HRV data were available for 2722 subjects; 567 subjects using
antihypertensive medication and 113 with a history of myocardial
infarction or congestive heart failure were excluded from
analysis: therefore, 931 men and 1111 women were eligible for
the study. For the analyses of incident hypertension, 472
subjects (245 men and 227 women) were excluded because of presence of
hypertension at the index examination, and 136 subjects did not attend
the examination 4 years later. Of the subjects eligible (633 men and
801 women) for the incidence study, 119 men and 125 women developed
hypertension at the follow-up examination 4 years later.
At the index examination, subjects with hypertension were older
than those with normal blood pressure (Table 1
). After age adjustment, body mass
index, baseline systolic and diastolic blood
pressures, and mean heart rate were higher in hypertensive men and
women compared with the normotensives. Alcohol consumption was higher
in hypertensive men, whereas no significant difference was observed for
smoking and coffee consumption (Table 1
). After adjustment for the
clinical covariates, all HRV measures, with the exception of the LF/HF
ratio, were significantly reduced in subjects with hypertension
compared with those with normal blood pressure (Table 2
).
View this table:
[in a new window]
Table 1. Mean Age and Age-Adjusted Clinical Characteristics
of Hypertensive and Normotensive Subjects at Index Examination
View this table:
[in a new window]
Table 2. Comparison of Adjusted Measures of Heart Rate
Variability Between Hypertensive and Normotensive Subjects at Index
Examination
The baseline adjusted HRV values in normotensive men who developed
hypertension during 4 years of follow-up were reduced in comparison to
those who remained normotensive (Table 3
). In women, LF and HF were lower at
baseline in those who developed hypertension during follow-up. Table 3
also shows the adjusted OR corresponding to a 1-SD decrement of each
HRV measure. These analyses revealed that LF was associated
with new-onset hypertension in men (OR, 1.38; 95% confidence interval,
1.04 to 1.83).
View this table:
[in a new window]
Table 3. ORs for Incident Hypertension on Follow-up Among
Normotensive Subjects According to HRV Measures at Baseline
. This has been plotted for nonsmoking
men and women (with mean values for other covariates) at 0.5-SD
decremental units. There is a steep curvilinear relation between LF and
the incidence of hypertension in men; this relation was less striking
in women.

View larger version (16K):
[in a new window]
Figure 1. Plots of probability of developing hypertension
during 4-year follow-up as a function of natural-log transformed low
frequency power (ln LF). The crude probability of developing
hypertension is displayed for men and women per 0.5-SD units of
natural-log transformed LF.
The impact of LF on longitudinal blood pressure change as a
continuous variable was analyzed using multiple linear
regression analysis. After adjustment for clinical covariates
and baseline blood pressure, a 1-SD decrement in LF was associated with
a mean increase of 1.95 mm Hg in systolic and 0.83
mm Hg in diastolic blood pressure in men and 0.70
mm Hg in systolic and 0.26 mm Hg in
diastolic blood pressure in women. Figure 2
displays the linear relations between
blood pressure changes during follow-up and LF. The magnitude of change
in blood pressure as a function of LF was larger in men than in women,
with a shallower trend observed for changes in diastolic
compared with systolic blood pressure.

View larger version (17K):
[in a new window]
Figure 2. Line plots of predicted changes in blood pressure
during 4-year follow-up as a function of the natural-log transformed
low frequency power (ln LF). This line graph was plotted for nonsmoking
men and women with mean values for other covariates. The crude
predicted rise in blood pressure (both systolic and
diastolic) is displayed per 1-SD unit of natural-log
transformed LF.
![]()
Discussion
Top
Abstract
Introduction
Methods
Results
Discussion
References
Our findings suggest the presence of reduced LF in men who are at
risk for developing hypertension. The presence of reduced HRV in
hypertensive subjects and the association of LF with new-onset
hypertension are consistent with the hypothesis that
dysregulation of the autonomic nervous system plays a role in the
pathogenesis of hypertension.
After adjustment for age, body mass index, smoking, alcohol
consumption, and baseline systolic and diastolic
blood pressures, the LF component of the power spectral
analysis remained predictive of the development of hypertension
in men. Earlier work from Framingham has shown adiposity to be a strong
predictor of hypertension in men and women.21 A
noteworthy finding in our study was that the LF component of HRV in men
was observed to be a stronger predictor of hypertension than body mass
index, a measure of obesity. These findings are in contrast to those of
a recent study that identified HF to be a better predictor of incident
hypertension when compared with LF.11 This
difference can be explained by methodological differences; Liao et
al11 studied ECG recordings of 2 minutes
in duration, which may be insufficient in length to appropriately
measure the LF. The association between HF and incident hypertension in
that report11 was similar in direction but
stronger compared with our study. This could be explained by the fact
that the authors did not adjust for baseline differences in body mass
index and baseline blood pressure in the multivariable estimation
of incident hypertension. A total of 244 subjects developed
hypertension (cumulative incidence of 17%) in the present report
compared with 64 (5%) in the study by Liao et
al.11
) could be a
reflection of the low incidence of diastolic hypertension
in the middle-aged Framingham Heart Study population. Subjects with
diastolic hypertension at the index examination also may
have been more likely to receive drug treatment and therefore be
excluded from follow-up for changes in diastolic blood
pressure than those with systolic hypertension; this could have
attenuated the relation between HRV and diastolic blood
pressure.
An important strength of this study is the well-characterized
study sample through the many years of follow-up. This information
allowed us to select subjects who were free of clinically apparent
cardiovascular disease, which can alter autonomic
function and HRV measurements. Additionally, the relatively large
number of subjects who developed hypertension allowed more precise
estimation of the risk of hypertension and permitted adjustment for age
and baseline blood pressure.
The present study extends the clinical utility of HRV beyond
its role in the surveillance of diabetics and patients after myocardial
infarction.25 26 A reduction in HRV is associated
with an increased risk of cardiac mortality27 and
has been shown to predict risk for cardiac
events25 28 and overall
mortality.25 27 Additional research is needed to
determine whether reduced HRV contributes to the increased cardiac
mortality in hypertension. It is possible that an assessment of HRV may
help guide the selection of antihypertensive
therapy.29
HRV is reduced in men and women with systemic hypertension. Among
normotensive men, lower HRV was associated with greater risk for
developing hypertension. Estimation of LF using spectral
analysis of ambulatory ECG recordings improves the
prediction of risk of hypertension in men above that which can be
obtained from measurements of baseline systolic and
diastolic blood pressures, body mass index, and age. These
findings are consistent with the hypothesis that autonomic
dysregulation is present in the early stage of hypertension.
![]()
Selected Abbreviations and Acronyms
HF
=
high frequency power
HRV
=
heart rate variability
LF
=
low frequency power
LF/HF
=
ratio of low frequency to high frequency power
OR
=
odds ratio
pNN50
=
percentage of differences between normal RR intervals >50 ms based on
2-hour recordings
r-MSSD
=
root-mean square of successive differences
SDNN
=
standard deviation of normal RR intervals
TP
=
total power
![]()
Acknowledgments
This study was supported by National Institutes of
Health/National Heart, Lung, and Blood Institute contract
NO1-HC-38038.
![]()
Footnotes
Reprint requests to Daniel Levy, MD, Framingham Heart Study, 5 Thurber St, Framingham, MA 01702.
![]()
References
Top
Abstract
Introduction
Methods
Results
Discussion
References
1.
Julius S. Autonomic nervous system dysregulation
in human hypertension. Am J Cardiol. 1991;67:3B7B.[Medline]
[Order article via Infotrieve]
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P. Coruzzi, M. Gualerzi, E. Bernkopf, L. Brambilla, V. Brambilla, V. Broia, C. Lombardi, and G. Parati Autonomic Cardiac Modulation in Obstructive Sleep Apnea: Effect of an Oral Jaw-Positioning Appliance. Chest, November 1, 2006; 130(5): 1362 - 1368. [Abstract] [Full Text] [PDF] |
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D. Felber Dietrich, C. Schindler, J. Schwartz, J.-C. Barthelemy, J.-M. Tschopp, F. Roche, A. von Eckardstein, O. Brandli, P. Leuenberger, D. R. Gold, et al. Heart rate variability in an ageing population and its association with lifestyle and cardiovascular risk factors: results of the SAPALDIA study Europace, July 1, 2006; 8(7): 521 - 529. [Abstract] [Full Text] [PDF] |
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M. A. Kizilbash, M. R. Carnethon, C. Chan, D. R. Jacobs, S. Sidney, and K. Liu The temporal relationship between heart rate recovery immediately after exercise and the metabolic syndrome: the CARDIA study Eur. Heart J., July 1, 2006; 27(13): 1592 - 1596. [Abstract] [Full Text] [PDF] |
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A. J. Hautala, T. Rankinen, A. M. Kiviniemi, T. H. Makikallio, H. V. Huikuri, C. Bouchard, and M. P. Tulppo Heart rate recovery after maximal exercise is associated with acetylcholine receptor M2 (CHRM2) gene polymorphism Am J Physiol Heart Circ Physiol, July 1, 2006; 291(1): H459 - H466. [Abstract] [Full Text] [PDF] |
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D. Lucini, G. Di Fede, G. Parati, and M. Pagani Impact of Chronic Psychosocial Stress on Autonomic Cardiovascular Regulation in Otherwise Healthy Subjects Hypertension, November 1, 2005; 46(5): 1201 - 1206. [Abstract] [Full Text] [PDF] |
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L. F. Berkman Tracking Social and Biological Experiences: The Social Etiology of Cardiovascular Disease Circulation, June 14, 2005; 111(23): 3022 - 3024. [Full Text] [PDF] |
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H. Hemingway, M. Shipley, E. Brunner, A. Britton, M. Malik, and M. Marmot Does Autonomic Function Link Social Position to Coronary Risk?: The Whitehall II Study Circulation, June 14, 2005; 111(23): 3071 - 3077. [Abstract] [Full Text] [PDF] |
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K. Dingli, T. Assimakopoulos, P.K. Wraith, I. Fietze, C. Witt, and N.J. Douglas Spectral oscillations of RR intervals in sleep apnoea/hypopnoea syndrome patients Eur. Respir. J., December 1, 2003; 22(6): 943 - 950. [Abstract] [Full Text] [PDF] |
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E. B. Schroeder, D. Liao, L. E. Chambless, R. J. Prineas, G. W. Evans, and G. Heiss Hypertension, Blood Pressure, and Heart Rate Variability: The Atherosclerosis Risk in Communities (ARIC) Study Hypertension, December 1, 2003; 42(6): 1106 - 1111. [Abstract] [Full Text] [PDF] |
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R. Wolk, A. S.M. Shamsuzzaman, and V. K. Somers Obesity, Sleep Apnea, and Hypertension Hypertension, December 1, 2003; 42(6): 1067 - 1074. [Abstract] [Full Text] [PDF] |
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C. C. Liu, T. B. J. Kuo, and C. C. H. Yang Effects of estrogen on gender-related autonomic differences in humans Am J Physiol Heart Circ Physiol, November 1, 2003; 285(5): H2188 - H2193. [Abstract] [Full Text] [PDF] |
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A. S. M. Shamsuzzaman, B. J. Gersh, and V. K. Somers Obstructive Sleep Apnea: Implications for Cardiac and Vascular Disease JAMA, October 8, 2003; 290(14): 1906 - 1914. [Abstract] [Full Text] [PDF] |
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D. Lucini, G. S. Mela, A. Malliani, and M. Pagani Impairment in Cardiac Autonomic Regulation Preceding Arterial Hypertension in Humans: Insights From Spectral Analysis of Beat-by-Beat Cardiovascular Variability Circulation, November 19, 2002; 106(21): 2673 - 2679. [Abstract] [Full Text] [PDF] |
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J E Mietus, C-K Peng, I Henry, R L Goldsmith, and A L Goldberger The pNNx files: re-examining a widely used heart rate variability measure Heart, October 1, 2002; 88(4): 378 - 380. [Abstract] [Full Text] [PDF] |
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J Gutierrez, R Santiesteban, H Garcia, A Voustianiouk, R Freeman, and H Kaufmann High blood pressure and decreased heart rate variability in the Cuban epidemic neuropathy J. Neurol. Neurosurg. Psychiatry, July 1, 2002; 73(1): 71 - 72. [Abstract] [Full Text] [PDF] |
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A Yildirir, M. K Batur, and A Oto Hypertension and arrhythmia: blood pressure control and beyond Europace, January 1, 2002; 4(2): 175 - 182. [Abstract] [PDF] |
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D. Lucini, G. Norbiato, M. Clerici, and M. Pagani Hemodynamic and Autonomic Adjustments to Real Life Stress Conditions in Humans Hypertension, January 1, 2002; 39(1): 184 - 188. [Abstract] [Full Text] [PDF] |
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K. Sevre, J. D. Lefrandt, G. Nordby, I. Os, M. Mulder, R. O. B. Gans, M. Rostrup, and A. J. Smit Autonomic Function in Hypertensive and Normotensive Subjects : The Importance of Gender Hypertension, June 1, 2001; 37(6): 1351 - 1356. [Abstract] [Full Text] [PDF] |
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T. G. M. Vrijkotte, L. J. P. van Doornen, and E. J. C. de Geus Effects of Work Stress on Ambulatory Blood Pressure, Heart Rate, and Heart Rate Variability Hypertension, April 1, 2000; 35(4): 880 - 886. [Abstract] [Full Text] [PDF] |
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C D A Goonasekera and M J Dillon Current topic: Measurement and interpretation of blood pressure Arch. Dis. Child., March 1, 2000; 82(3): 261 - 265. [Full Text] |
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H. Bettermann, D. Cysarz, H. C. Kummell, J. Singh, M. Larson, and D. Levy Heart Rate Variability: How to Assess Effects of Mild Therapies on Autonomic Control in Small Groups of Mild and Borderline Hypertensives? Hypertension, February 1, 2000; e7(2): . [Full Text] [PDF] |
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K. Narkiewicz and V. K. Somers Interactive Effect of Heart Rate and Muscle Sympathetic Nerve Activity on Blood Pressure Circulation, December 21, 1999; 100(25): 2514 - 2518. [Abstract] [Full Text] [PDF] |
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