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B J TenVoorde

Publications and source records attributed to B J TenVoorde.

15 recordsLinked to original sources
PubMed2003

Measures of cardiovascular autonomic nervous function: agreement, reproducibility, and reference values in middle age and elderly subjects.

AIMS/HYPOTHESIS: Currently, three categories of cardiovascular autonomic nervous function measures are used: classic Ewing-test measures, measures of heart-rate variability (HRV), and measures of baroreflex sensitivity (BRS). Little is known about the agreement between these measures, and reference and reproducibility values for these measures have not been reported within the same group. METHODS: As part of the Hoorn Study, 631 subjects aged 50 to 75 participated in a study of autonomic nervous function. Cardiac cycle duration (RR interval) and continuous finger arterial pressure were measured under three conditions: during spontaneous breathing, during six deep breaths over 1 min, and during an active change in position from lying to standing. From these readings, ten measures of autonomic function were assessed (mean heart rate, three Ewing test measures, five HRV measures and one BRS measure). RESULTS: Regression analysis in a healthy subgroup (n=191) showed sex differences for two of the ten measures and seven measures decreased with age. Therefore, appropriate age-specific and sex-specific reference values were calculated. Reproducibility (n=39) of most measures was moderate, with a reliability coefficient of around 50%. Agreement between the measures of autonomic nervous function varied greatly, between 0% and 87%. The HRV-power ratio measure and the blood pressure changes in the lying-to-standing test showed the lowest agreement with all other measures. CONCLUSION/INTERPRETATION: This study provides age-specific and sex-specific reference values for a wide range of different autonomic function measures in an elderly population. Agreement among the different measures varied widely and reproducibility was only moderate.

Aged↗
PubMed2001

Impaired autonomic function is associated with increased mortality, especially in subjects with diabetes, hypertension, or a history of cardiovascular disease: the Hoorn Study.

OBJECTIVE: Measures of baroreflex sensitivity, heart rate variability (HRV), and the classical Ewing test parameters are currently used for the diagnosis of diabetic autonomic neuropathy and for mortality risk stratification after myocardial infarction. However, the strengths of the associations of these measures of autonomic function with risk of mortality have never been compared in one study population. Furthermore, no evidence is available on the possible effect of glucose tolerance on these associations. RESEARCH DESIGN AND METHODS: The study population (n = 605) consisted of a glucose tolerance-stratified sample from a general population (50-75 years of age). Cardiac cycle duration and continuous finger arterial pressure were measured under two conditions: at rest and on metronome breathing. From these readings, seven parameters of autonomic function were assessed (one Ewing, five HRV, and one baroreflex sensitivity). RESULTS: During 9 years of follow-up, 101 individuals died, 43 from cardiovascular causes. Subjects with diabetes and low levels of the autonomic function parameters, indicating impaired autonomic function, had an approximately doubled risk of mortality. This association was consistent, though not statistically significant, for all parameters. The elevated risk was not observed in subjects without diabetes, hypertension, or prevalent cardiovascular disease. CONCLUSIONS: Impaired autonomic function is associated with all-cause and cardiovascular mortality. Moreover, the results of the present study suggest that cardiac autonomic dysfunction in patients already at risk (diabetes, hypertension, or history of cardiovascular disease) may be especially hazardous.

Aged↗
PubMed2000

Glucose tolerance and other determinants of cardiovascular autonomic function: the Hoorn Study.

AIMS/HYPOTHESIS: Currently, three categories of measures are used to assess cardiovascular autonomic dysfunction: measures of the Ewing-test, measures of heart-rate variability, and measures of baroreflex sensitivity. We studied the determinants of these measures obtained from cardiovascular autonomic function tests in the Hoorn Study. METHODS: The study group (n = 631) consisted of a glucose-tolerance-stratified sample from a 50- to 75-year-old group of people. Cardiac cycle duration (RR interval) and continuous finger arterial pressure were measured under three conditions: during (a) spontaneous breathing, (b) six deep breaths over one minute, and (c) an active change in position from lying to standing. From these readings, ten measures of autonomic function were assessed (three Ewing, six heart-rate variability and one baroreflex sensitivity). As possible determinants we considered age, sex, glucose tolerance, cardiovascular disease, use of anti-hypertensive drugs, anthropometric factors, metabolic factors and lifestyle factors. RESULTS: Multivariate analysis showed that eight of ten cardiovascular autonomic function measures were most strongly associated with glucose tolerance. Furthermore, measures were moderately associated with age, sex, waist-to-hip ratio, use of anti-hypertensive drugs, and insulin. The measures were weakly associated with coronary artery disease but not with lipids. The strongest determinants seemed to differ between subjects with and without diabetes: in the non-diabetic subjects the most strongly associated were age and use of anti-hypertensive drugs and in subjects with diabetes, insulin. No consistent differences in association between the three categories of measures were observed. CONCLUSION/INTERPRETATION: The strongest determinants of autonomic function were age, presence of diabetes and use of anti-hypertensive drugs.

Aged↗
PubMed2000

The importance of high-frequency paced breathing in spectral baroreflex sensitivity assessment.

OBJECTIVE: Computation of the low-frequency (LF) blood pressure variability (BPV) to heart rate variability (HRV) transfer-index is a common method to assess baroreflex sensitivity (BRS), tacitly assuming that all LF-HRV is caused by baroreflex feedback of LF-BPV. However, respiration may also cause HRV by mechanisms not involving the baroreflex. Application of narrow-band (controlled) high-frequency breathing would keep such non-baroreflex-mediated HRV best out of the LF band. Spontaneous breathing, because of its broad-band character, might cause extra, non-baroreflex-mediated, HRV in the LF band, while paced LF breathing would even concentrate most non-baroreflex-mediated HRV in the LF band. Our study addresses the likely resulting BRS overestimation. DESIGN: We recorded HRV and BPV in 20 healthy young subjects in the sitting position. We varied the sympathovagal balance by gradual leg-lowering from horizontal till 60 degrees . At each angle the subjects performed controlled 0.10 Hz, spontaneous, and controlled 0.25 Hz respiration. RESULTS: Resting BRS values were 15.5(7.2), 13.1 (3.7), and 11.6(6.2) ms/mmHg, respectively. Both the 15/min and the free breathing values differed significantly, P< 0.01 and P= 0.04, from the 6/min breathing value. With lowered legs, the BRS values were 8.2(3.4), 8.3(2.9), and 8.3(3.4) ms/mmHg, respectively. CONCLUSION: Controlled 6/min breathing caused significant BRS overestimation under resting conditions. For the group, spontaneous respiration yielded acceptable BRS values, but individual BRS values deviated sometimes considerably. Conversely, with gravitational load, the respiratory pattern had only minor impact on BRS. Our results demonstrate that the risk of an overestimated BRS value is realistic as long as respiration is not controlled and of high-frequency.

Adult↗
PubMed2000

Correlated neurocardiologic and fitness changes in athletes interrupting training.

PURPOSE: We studied nine male Dutch top marathon skaters during a 1-month interruption of their training schedules after their last contest in the winter to investigate a possible decline in baroreflex sensitivity. METHODS: Before and after this period, a maximal exercise test was done, and at days 0, 4, 7, 14, and 28 neurocardiologic measurement sessions--heart rate and noninvasive baroreflex sensitivity, recumbent and tilt--were performed. RESULTS: Interruption of training resulted in a significant and relevant decrease in the maximal oxygen uptake (from 65.7 +/- 5.8 to 61.6 +/- 4.7 mL O2 x kg(-1) x min(-1); P = 0.03), most likely associated with decreased competitive possibilities. Resting heart rate modestly increased (from 54.6 +/- 7.2 to 58.8 +/- 7.5 bpm), however, not significantly. Heart rate during 60 degrees tilt increased considerably (from 70.1 +/- 6.1 to 80.1 +/- 9.1 bpm; P = 0.01), possibly due to a decrease in blood volume and an increase in cardiopulmonary baroreflex gain. Arterial baroreflex sensitivity decreased significantly in the recumbent (from 13.3 +/- 5.4 to 9.8 +/- 3.8 ms x mm Hg(-1), P = 0.04), but not in the 60 degrees tilt position (from 6.7 +/- 2.0 to 6.0 +/- 2.5 ms x mm Hg(-1)). The relative decrease in baroreflex sensitivity and maximal oxygen uptake correlated significantly (r = 0.71, P = 0.02). CONCLUSIONS: In summary, our data show that correlated detrimental changes in fitness and baroreflex sensitivity are measurable in these athletes after a month of interruption of training.

Adult↗
PubMed2000

A baroreflex model of short term blood pressure and heart rate variability.

Parameters based on heart rate variability alone or on both heart rate and blood pressure variability (baroreflex sensitivity) are becoming increasingly clinical relevant. Nevertheless a complete insight in physiological mechanisms underlying these parameters is still lacking. A computer model may help to fill up some of the gaps. We present a model which consists of a simple beat-to-beat hemodynamic part (Starling heart and Windkessel) linked to a detailed continuous modelled neural control part. The intermediate between continuous and beat-to-beat part is an integral pulse frequency modulator (IPFM) acting as cardiac pacemaker. Input for the IPFM is a "sympathovagal" balance signal, with different dynamics for sympathetic and vagal branches. Low-frequency variability is supposed to arise from resonance of existing noise, while high-frequency variability (respiration) is assumed to enter the closed loop at the hemodynamic (blood pressure) site. Results of three studies have been used for validation: (1) spontaneous variability in heart rate and blood pressure (baroreflex transfer functions), (2) vagal blockade with atropine, (3) a modified Valsalva manoeuvre performed in normal and quadriplegic man. Steady state as well as dynamic properties of the model reasonably well fitted to these experimental data.

Autonomic Nervous System↗
PubMed2000

Baroreflex sensitivity in the elderly: influence of age, breathing and spectral methods.

Baroreflex sensitivity (BRS) has been proposed as a diagnostic parameter for neurological disorders and as a survival-prognosis parameter in diabetic and cardiac patients. Therefore reference values and the reproducibility of BRS were assessed, taking into account the possible influence of age, gender, test conditions and some analysis variants. Healthy subjects (n=191) were randomly selected from the 50-75-year-old general population (the Hoorn Study). Variations in blood pressure and heart rate were recorded non-invasively during three breathing modes: spontaneous (3 min), slow metronome (1 min; 6 breaths/min=0.1 Hz) and fast metronome (1 min; 15 breaths/min=0.25 Hz), all in a supine position. From these recordings, BRS was assessed as the transfer gain between changes in blood pressure and heart period, and as the alpha coefficient. BRS values ranged from 5.0 to 8.9 ms.mmHg(-1). Slow metronome breathing resulted in higher BRS values than fast breathing, while during spontaneous breathing BRS in the low-frequency band was lower than that in the high-frequency band (respiratory origin). BRS values decreased with lower coherence criteria. BRS-alpha was significantly higher than BRS-gain. While regression analysis showed no gender differences, BRS decreased with age. Therefore age-specific reference values were calculated. The reproducibility of BRS values was in general moderate, with reliability coefficients ranging from 43 to 81% and coefficients of variation ranging from 34 to 59%. In conclusion, this study shows age, breathing mode, frequency and coherence threshold to affect measures of BRS. Therefore these factors should be considered in clinical studies; appropriate reference values are given.

Age Factors↗
PubMed1998

Longitudinal follow-up of cardiovascular reflex tests in multiple sclerosis.

Several studies have shown various degrees of autonomic dysfunction in patients with multiple sclerosis. Longitudinal follow-up studies are remarkably scarce up to now. We assessed autonomic dysfunction twice with an interval of 1 year in 20 relapsing remitting and 26 secondary progressive MS-patients. Autonomic function was assessed by the heart rate response during deep breathing, standing up and Valsalva manoeuvre. Only the maximum change in heart rate after standing up (in ms and beats/min) and the Max/Min ratio after standing up showed significant worsening over 1 year. The changes in EDSS scores also documented gradual deterioration of the neurological condition over the study period. We conclude that there is progression of autonomic dysfunction in MS over 1 year and that this could correlate with progression in clinical disability.

Adult↗
PubMed1997

Coronary heart disease risk indicators, aerobic power, and physical activity in men with spinal cord injuries.

OBJECTIVE: To compare the lipid and (apo-)lipoprotein profile and blood pressure of men with long-standing spinal cord injuries (SCI) to those of an age-matched able-bodied (AB) population, and to assess the most important determinants of this profile and blood pressure. DESIGN: A cross-sectional study of persons with chronic SCI residing in the community. SETTING: Tests were performed in a university research laboratory. SUBJECTS: Thirty-seven men (age 37.4 +/- 12.0 yrs) with longstanding (14.7 +/- 8.6 yrs) SCI ranging from level C4/5 to L5 volunteered to participate. Comparisons were made with published data from 3,498 AB men, age 20 to 59 yrs, from the same country. MAIN OUTCOME MEASURES: Lipid and lipoprotein profile (total cholesterol [TC], high-, low-, and very low-density lipoprotein cholesterol [HDL-C, LDL-C and VLDL-C, respectively], and triglycerides [TG]), as well as aerobic power, activity level, anthropometric variables, and blood pressure. Multiple regression analyses assessed the most important determinants of the lipid and blood pressure profile. RESULTS: None of the lipid variables were related to the lesion level. TC, HDL-C, and TC/HDL-C were not significantly different from the AB population. The most important determinants of TC, LDL-C, and the ratios TC/HDL and HDL-C/LDL-C were age, smoking behavior, and activity level. Aerobic power was not an important determinant of any lipid or (apo-)lipoprotein or blood pressure. CONCLUSION: Men with long-standing SCI do not appear to have an essentially different coronary heart disease risk profile compared with AB persons. Modifiable risk factors such as activity level, smoking, alcohol consumption, body mass index, and adipose tissue were more important than lesion level and aerobic power in the determination of the lipid and lipoprotein profile, suggesting several potential interventions.

Adult↗
PubMed1995

On the quantification of heart rate changes in autonomic function tests: relations between measures in beats per minute, seconds and dimensionless ratios.

1. Disorders of the autonomic nervous system are frequently diagnosed by measuring heart rate changes in response to deep-breathing and lying-to-standing manoeuvres. The heart rate changes in these manoeuvres are quantified in measures using various units, like beats per minute, seconds and dimensionless ratios. 2. In the present study we mathematically derived relationships between the measures which quantify heart rate changes in beats per minute, seconds and dimensionless ratios. The theoretical outcomes were experimentally confirmed by the results of the deep-breathing and the lying-to-standing test in 525 healthy and diabetic subjects. The measures were found to be non-equivalent, because the mean RR interval duration influenced the measures in different ways. 3. It is argued that measures in seconds are preferable to measures in beats per minute or ratios, because the physiological interpretation of this measure is easier, and the sensitivity of measures in seconds is expected to be greater. 4. Finally, we recommend that measures of heart rate variation in the deep-breathing and lying-to-standing manoeuvre are accompanied by information on the mean RR interval duration or mean heart rate to allow correct interpretation of the measures.

Autonomic Nervous System↗
PubMed1995

Effects of ketanserin on heart rate and blood pressure variability: implications for the effect on the baroreflex mechanisms.

Ketanserin is an antihypertensive drug with affinity to both serotonin S2- and alpha 1-adrenoceptors. The specific effects of ketanserin on the baroreflex are not fully understood. We, therefore, studied baroreflex regulation based on blood pressure (BP) and heart rate (HR) responses to several maneuvers before and after the administration of 2 x 5 mg of ketanserin i.v. both in supine and in standing posture. Seven young healthy volunteers were investigated. We measured spontaneous variability in HR and BP (Finapres), and performed deep inspiration, Valsalva, and lying-to-standing tests. We also used a modified Valsalva maneuver that consist of Deep Inspiration Breath-holding with closed glottis and EXpiration: DIBEX maneuver. From the BP recordings, peripheral resistance (TPR) and stroke volume (SV) were estimated by the Modelflow method. Thirty minutes after the administration of ketanserin, there was no significant change in mean HR, BP, spectral power of HR and BP variability, baroreflex sensitivity, or Valsalva ratio. Thus ketanserin did not affect the cardiac baroreflex mechanism. However, in standing position, SV increased and TPR decreased under the influence of ketanserin, and BP overshoot after the Valsalva and DIBEX maneuver was significantly decreased as well. There was also no reflex recovery of BP during the DIBEX maneuver in three volunteers, who felt faint. These observations indicate that there is a lack of vasoconstriction. We conclude that ketanserin is not a vasodilator but seems to inhibit vasoconstriction.

Adult↗
PubMed1994

Spectra of data sampled at frequency-modulated rates in application to cardiovascular signals: Part 1. Analytical derivation of the spectra.

Beat-to-beat cardiovascular signals, e.g. a series of systolic pressure values, can be considered as time series which are pulse amplitude modulated (PAM) and pulse frequency modulated (PFM). The latter process, due to variations in heart rate, causes the series to become non-uniformly spaced in time. If PAM is to be quantified by spectral analysis, the influence of PFM must be known. An analytical expression is therefore derived for the spectrum of sinusoids which are sampled according to the output event series of a linear integral pulse frequency modulator (IPFM). We conclude that two spectral components arise at the difference and sum of the PFM and PAM frequencies, fp +/- fx, with amplitudes proportional to the PFM modulation depth. These components appear as a DC component and as a first harmonic if both modulating frequencies are equal. In addition, a cluster of spectral components appears around the mean pulse frequency fo (i.e. mean heart rate), at frequencies fo-nfp +/- fx, which may leak into the signal band. From these theoretical considerations, we conclude that the amplitude spectrum of a sinusoidally varying systolic blood pressure series can contain up to 20-30% spurious components, owing to the heart rate modulation process.

Blood Pressure↗
PubMed1994

Spectra of data sampled at frequency-modulated rates in application to cardiovascular signals: Part 2. Evaluation of Fourier transform algorithms.

For three direct Fourier transform algorithms we quantified the influence of pulse frequency modulation (PFM) on the spectral estimation of pulse amplitude modulation (PAM). The simulation study is based on sinusoid functions sampled according to a pulse sequence which is the output of an integral pulse frequency modulator (IPFM). One algorithm exactly reproduces the theoretical spectrum derived in Part 1. The other two, including the classical FFT, scale all PFM-induced components in a different way, and in addition, generate higher modulating frequency harmonics. For a PFM depth below 30%, the sum of spurious PFM components is almost linearly dependent on this modulation depth, for all three algorithms. Dividing the effect of PFM in a 'harmonic' and 'aliasing' distortion, we found that the FFT has a relatively high harmonic distortion, compared to an algorithm that takes into account the non-uniform character of the data. In the cardiovascular (worst) case of 30% modulation in heart rate (PFM) at a frequency of 0.1 Hz, the FFT spectrum of beat-to-beat systolic blood pressure variations contains approximately 20% of spurious components caused solely by the modulation in time occurrences of the blood pressure samples. The 'non-uniform' algorithm performs twice as well in this case.

Algorithms↗
PubMed1994

Effects of epidural analgesia and atropine on heart rate and blood pressure variability: implications for the interpretation of beat-to-beat fluctuations.

Cardiovascular variables such as heart rate, arterial blood pressure, stroke volume and the shape of electrocardiographic complexes all vary beat-by-beat. This variability occurs because of the dynamic response of cardiovascular regulatory systems to perturbations in cardiovascular function. We applied spectral analysis to the effects of sympathetic vasomotor blockade by epidural analgesia and parasympathetic blockade of the heart by atropine on the beat-to-beat variability of heart rate and blood pressure in humans. High-frequency fluctuations in heart rate (+/- 0.2 Hz) are caused by respiratory induced fluctuations of blood pressure, mediated by the vagus nerve. Low-frequency fluctuations (0.06-0.12 Hz) are related to sympathetic baroreflex control of vasomotor activity and heart rate. In our study, even partial parasympathetic blockade of the heart by atropine decreased the power in the high and low frequency heart rate fluctuations. There were no significant changes in blood pressure fluctuations in either frequency range. Sympathetic blockade by epidural analgesia decreased only low-frequency fluctuations of both heart rate and blood pressure. From a cardiovascular model and our experimental results we support the view that high frequency fluctuations in heart rate are due to the vagal response to blood pressure fluctuations caused by respiration and that the fluctuations around 0.1 Hz in both heart rate and blood pressure have their origin in the sympathetic baroreflex control loop of vasomotor activity.

Adolescent↗