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3. Spectral measures of short-term blood pressure and heart rate variations: Methodological considerations

Author

Schachinger, H., Langewitz, W., Ruddel, H., Reino, S. T., Mulder, L. J. M., van Roon, A., Veldman, J. B. P., Schmieder, R., and Schulte, W.

Subjects
validity, DIABETIC AUTONOMIC NEUROPATHY, REST, heart rate variability, blood pressure variability, reproducibility, baroreflex sensitivity
Abstract

Since the non-invasive volume clamp technique (developed by Penaz) for continuous blood pressure (BP) recording became available, the assessment of short-term BP and heart rate (HR) variability and successive estimation of baroreflex sensitivity (BRS) by spectral analysis techniques has been inaugurated for clinical evaluation of autonomic neuropathy and various cardiovascular disorders. However, basic methodological requirements of short-term cardiovascular variability measures such as reliability and validity have to be investigated. In a first study we addressed reproducibility of short-term BP and HR variability, and in a second study we investigated the validity of BRS estimation based on spectral analysis of non-invasive BP and HR recordings. Non-invasive beat-to-beat BP (FINAPRES-system), HR and respiratory frequency were continuously recorded during rest and during paced respiration (0.3 Hz). Within a three weeks period 57 healthy subjects (age: 32 +/- 8 years, casual BP: 133 +/- 14 / 88 9 mmHg, HR: 76 +/- 9 bpm, mean respiratory frequency at rest: 0.24 +/- 0.08 Hz) were measured twice for 5 minutes respectively. power spectra and transfer functions between systolic BP and HR (coherence and modulus) were determined by a discrete Fourier analysis with frequency resolution of 0.01 Hz over an integral of 0.01 to 0.5 Hz (CARSPAN program). Log-transformed variability measures were calculated for the low (0.02-0.06 Hz), mid (0.07-0.14 Hz), high (0.15-0.40 Hz), respiratory related (mean respiratory frequency +/- 0.03 Hz) and total frequency band (0.02-0.5 Hz). BRS was mathematically defined by integration of the modulus function over the mid, high and respiratory related frequency bands respectively. For the purpose of validation BRS was determined by the spectral method, as well as by a standardized reference technique employing bolus angiotensine II (A2) injections in 18 observations. HR variability and systolic BP variability, as well as BRS estimated by spectral analysis showed significant test-retest stability (r > 0.6) in all frequency bands. Test-retest stability of BRS estimated by the spectral analysis further increased when periods of paced respiration were analysed. High correlations between BRS calculated by the standardized bolus A2 injections and spectral techniques could be found for the mid (r=0.62, p

Published
1996

4. Efficacy of four antihypertensive drugs (clonidine, enalapril, nitrendipine, oxprenolol) on stress blood pressure

Author

Schmieder, R.E., Bahr, M., Langewitz, W., Ruddel, H., Schachinger, H., and Schulte, W.

Subjects
Blood pressure -- Measurement, Enalapril -- Health aspects, Clonidine -- Health aspects, Stress (Physiology) -- Drug therapy, Hypertension -- Drug therapy, Nitrendipine -- Health aspects, Antihypertensive drugs -- Physiological aspects, Health
Abstract

The effect of four different blood pressure reducers (antihypertensives) on blood pressure during everyday life stress and during stress induced in a laboratory was studied. Sixty middle-aged men with mild to moderate high blood pressure (hypertension), never previously treated, were treated with low dose clonidine, oxprenolol, nitrendipine, or enalapril. All four groups were similar in age, weight, degree of obesity and blood pressure. After six months of therapy, diastolic (i.e., while the heart is at rest, between beats) blood pressure was the same in all four groups. Systolic blood pressure (during the pumping phase) was lower in patients treated with clonidine or oxprenolol than those treated with enalapril. Blood pressure under stress was lowest in patients treated with oxprenolol and nitrendipine together. Oxprenolol was not as effective as nitrendipine or enalapril during mental stress tests.

Published
1989

9. Pharmacological Modulation of StressInduced Cardiovascular Hyperreactivity in Essential Hypertension

Author

Schulte, W., Ruddel, H., Schmieder, R., Schweninger, H., Brautigam, M., and Welzel, D.

Abstract

The effects of the calcium antagonist isradipine and the ß-blocker metoprolol, which are based on different antihypertensive therapeutic principles, were evaluated in 52 men with mild-to-moderate hypertension in a 6-week, double-blind, randomized study. Mental stress-testing was performed before and after active treatment. With isradipine (n= 26), the stress-induced responses of cardiac output and total peripheral resistance were not significantly changed, but the blood pressure (BP) response, specifically the diastolic response, was decreased. With metoprolol (n= 26), there was a decreased response of cardiac output and an increased response of total peripheral resistance, and the BP response was even greater than it had been before treatment. Thus, these results indicate that ß-blockade is effective in reducing cardiac responsiveness but, because of vascular counterregulatory mechanisms, BP responsiveness is not decreased. In contrast, calcium antagonism preserves the physiological hemodynamic profile while reducing BP responsiveness to stress.

Published
1992

10. Cardiovascular changes during mental stress: correlations with presence of coronary risk factors and cardiovascular disease in physicians and dentists.

Author

McKinney ME, McIlvain HE, Hofschire PJ, Collins RE, Somers JA, Ruddel H, Buell JC, and Eliot RS

Subjects
Adult, Cardiovascular System physiopathology, Female, Hemodynamics, Humans, Male, Middle Aged, Physical Fitness, Problem Solving physiology, Risk Factors, Arousal physiology, Coronary Disease physiopathology, Dentists psychology, Hypertension physiopathology, Physicians psychology, Stress, Psychological complications
Abstract

Stress may play a role in the etiology of cardiovascular disease. Research showing that mental stress administered in laboratory settings causes great change in cardiovascular and hemodynamic functioning supports this hypothesis. In a small sample of physicians and dentists, those who showed greater cardiovascular reactivity (hot reactors) to stress were more likely to be hyperlipidemic or to have had a myocardial infarction or coronary bypass surgery. In addition, some of the nonreactive group were hypertensives taking medication, which may have blunted their response to stress. Persons with higher cholesterol, higher triglyceride levels, and lower HDL levels all showed greater increases in blood pressure (BP) in response to stress. Also, the reactive group reported less emotional support and experienced greater numbers of family-related stressful events in the previous year. The degree of aerobic fitness influenced resting hemodynamics and percentage of body fat but not reactivity to stress. Likewise, smoking did not affect reactivity, but former smokers did have a significantly elevated total systemic resistance at rest. While it is impossible to say whether reactivity causes disease, is the result of the presence of risk factors and disease, or is caused by some other factor which also contributes to disease, these results suggest that the presence of cardiovascular reactivity to mental stress is a sign of potential illness and indicates the need for further medical and risk factor study of the patient.

Published
1987

11. [Risks in the development of hypertension].

Author

Schmieder RE, Garavaglia G, Ruddel H, and Messerli FH

Subjects
Alcohol Drinking, Blood Pressure, Caffeine adverse effects, Contraceptives, Oral adverse effects, Diet adverse effects, Female, Humans, Male, Obesity complications, Risk Factors, Smoking adverse effects, Stress, Psychological complications, Hypertension etiology
Published
1988

12. Risks for arterial hypertension.

Author

Schmieder RE, Messerli FH, and Ruddel H

Subjects
Adult, Age Factors, Alcohol Drinking, Black People, Blood Pressure, Caffeine adverse effects, Contraceptives, Oral adverse effects, Female, Heart Rate, Humans, Hypertension diagnosis, Hypertension epidemiology, Hypertension genetics, Male, Middle Aged, Obesity complications, Risk, Smoking, Sodium Chloride adverse effects, Stress, Physiological complications, United States, Black or African American, Hypertension etiology
Abstract

In this article, the most important risk factors that may predict the transition from borderline to established hypertension are reviewed. Primary prevention has to focus on identifying individuals who are at highest risk and delaying or reversing further elevation of arterial pressure levels. A review of the literature indicates that several environmental and congenital factors can be identified as risk factors for the development of hypertension, including family history of essential hypertension, age, race, obesity, alcohol consumption, salt intake, hormonal status, and some stress factors. Of all diagnostic approaches to predict the development of hypertension, measurements of resting heart rate and responses to dynamic exercise have some predictive value.

Published
1986

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