Biomedical subjects
Publications and source records attributed to M Niederberger.
Arterial pressure varies over the course of the day depending on activities. It increases frequently in the presence of the physician. Long term blood pressure recording makes available a multitude of measurements taken during usual activities of the patient. These measurements permit identification of hypertensive patients at high risk i.e. patients with high blood pressure not only when facing their physician.
Hypertension is a multifactorial disease. Various antihypertensive drugs can lower arterial pressure in a given patient in a more or less efficient way. The sequential testing of several drugs is most promising for lowering blood pressure by monotherapy. If necessary a drug combination is preferable to dose adjustments of a single substance because of the risk for side effects growing with the dose.
The goal of this study was to investigate whether the elastic behavior of conduit arteries of humans or rats is altered as a result of concomitant hypertension. Forearm arterial cross-sectional compliance-pressure curves were determined noninvasively by means of a high precision ultrasonic echo-tracking device coupled to a photoplethysmograph (Finapres system) allowing simultaneous arterial diameter and finger blood pressure monitoring. Seventeen newly diagnosed hypertensive patients with a humeral blood pressure of 163/103 +/- 4.4/2.2 mm Hg (mean +/- SEM) and 17 age- and sex-matched normotensive controls with a humeral blood pressure of 121/77 +/- 3.2/1.9 mm Hg were included in the study. Compliance-pressure curves were also established at the carotid artery of 16-week-old anesthetized spontaneously hypertensive rats (n = 14) as well as Wistar-Kyoto normotensive animals (n = 15) using the same echo-tracking device. In these animals, intra-arterial pressure was monitored in the contralateral carotid artery. Mean blood pressures averaged 197 +/- 4 and 140 +/- 3 mm Hg in the hypertensive and normotensive rats, respectively. Despite the considerable differences in blood pressure, the diameter-pressure and cross-sectional compliance-pressure and distensibility-pressure curves were not different when hypertensive patients or animals were compared with their respective controls. These results suggest that the elastic behavior of a medium size muscular artery (radial) in humans and of an elastic artery (carotid) in rats is not necessarily altered by an increase in blood pressure.
The "Peripheral Arterial Vasodilation" hypothesis most completely explains the clinical spectrum of cirrhosis ranging from compensated to decompensated to the hepatorenal syndrome (Figure 15-1). As the systemic peripheral vasodilation increases, the neurohumoral responses to arterial underfilling are stimulated with resultant renal vasoconstriction, sodium and water retention. Hypoalbuminemia and portal hypertension, as well as local effects of vasodilation at the capillary level, also contribute to ascites formation and peripheral edema. The suppressed plasma renin activity and aldosterone concentrations and exaggerated natriuresis, which are observed in some patients with early cirrhosis during HWI and the supine position, probably indicate greater central translocation of splanchnic fluid in these volume expanded cirrhotic patients when compared with normal subjects. This interpretation is supported by the greater increases in ANF during HWI in these patients when compared with controls. The neurohumoral responses to arterial vasodilation in cirrhosis combine to decrease distal sodium and water delivery, an event which impairs escape from the sodium retaining effects of aldosterone and causes resistance to the distal tubular effect of ANF (Figure 15-3). As discussed, the peripheral arterial vasodilation of cirrhosis is no doubt multifactorial in nature and the resultant arterial underfilling may be worsened by events that could impair the cardiac response to afterload reduction, including bile salt accumulation, alcoholic cardiomyopathy, and tense ascites decreasing cardiac preload. This pathogenetic schema of cirrhosis is compatible with the unifying body fluid volume hypothesis (Figure 15-3), which we have recently proposed.
Non-invasive ambulatory blood pressure monitoring is increasingly being used in the diagnosis and the treatment of adult hypertensive patients. In children, the most obvious clinical use for intermittent blood pressure recordings is in the evaluation of borderline hypertension and the assessment of the efficacy of antihypertensive therapy. Adolescents who are hypertensive in the presence of the doctor are more often normotensive outside the physician's office than adult and elderly patients. Many elderly patients with isolated systolic hypertension have normal ambulatory systolic readings. Elderly patients with high blood pressures only in the physician's presence generally do not show a fall in ambulatory blood pressures when antihypertensive therapy is initiated or intensified. Thus, ambulatory blood pressure monitoring may be useful in detecting truly hypertensive patients among children and adolescents and in elderly people. This technique should make it possible to better define the cardiovascular risk, to avoid overtreatment and to individualize antihypertensive therapy.
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Pulse pressure waves are damped by the elastic properties of the blood vessels. This damping capacity can be evaluated by measuring vascular compliance a parameter which expresses changes of volume with respect to changes of pressure. Arterial compliance varies continuously with respect to intravascular pressure. Our group has developed an ultrasonograph which functions in the A mode capable of measuring the diameter of peripheral arteries during the cardiac cycle. This system is coupled to a photoplethysmograph which records non-invasively and continuously finger blood pressure. This enables construction of pressure-diameter graphs and the determination of arterial compliance and distensibility at each pressure value.
The present study was undertaken to assess in unanesthetized rats the effect of a kinin antagonist (D-Arg-Arg-Pro-Hyp-Gly-Thi-Ser-D-Phe-Thi-Arg-trifluoroacetic acid) on blood pressure, heart rate, and splanchnic nerve activity. The antagonist infused intra-arterially (50 micrograms/min) for 10 min had no blood pressure effect in control rats. It did, however, cause a significant increase in blood pressure in animals preinfused with a nonpressor dose of angiotensin II (1 ng/min i.v.) for 70 min. The antagonist-induced blood pressure rise was not associated with an increase in splanchnic nerve activity. Acute angiotensin-converting enzyme (ACE) inhibition with captopril (2.5 mg i.v.) had no influence on the pressor response to the kinin antagonist in angiotensin II-treated rats. These results obtained in conscious normotensive rats suggest that endogenous kinins participate in the control of blood pressure by attenuating the vasoconstrictor effect of angiotensin II. The involvement of kinin does not seem to be enhanced by acute ACE inhibition.
Three human testicular teratocarcinomas were serially passaged following subcutaneous transplantation into nude mice. Tumor cell suspensions from selected passages were injected intraperitoneally. The subcutaneous transplants of each tumor conserved the morphological characteristics of one component of the primary tumor, namely an embryonal carcinoma in one case and a yolk sac tumor in two. The latter maintained the capacity to synthesize alpha-fetoprotein (AFP). After intraperitoneal injection of cell suspensions, tumors, either attached to or even invading abdominal organs or in the form of free-floating tumor spheroids, were observed. AFP could be localized within the attached growths but not in the spheroids. A critical tumor volume and/or vascularization seemed to be necessary for AFP production in tumor cells. In spheroids from one tumor, cytogenetic analysis revealed both human and murine cells. Thus, these spheroids, apparently composed of tumor cells in the center and murine cells at the periphery, can not be considered to be embryoid bodies.
Correlations between scales and items of the "MPFH", and physical performance of MI-patients, lead us to conclude that the self-perception of decreased physical performance after MI is often generalized and thus leads to a decrease in self-esteem, often connected with feelings of social isolation. This pattern of reaction can in itself be a new risk factor during rehabilitation. Psychological rehabilitation must therefore focus on both: 1. trying to find a meaningful balance between moderate increase in physical performance and psychological adaptation to the reduction in performance, and 2. trying to reduce the feeling of social isolation which comes along with decreased physical performance.
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A special swimming programme was initiated during the course of rehabilitation of patients after myocardial infarction with additional disturbances of the musculoskeletal system. Allowance was made for aspects of individual training requirements. Patients were divided in two groups according initial values of physical working capacity: One group contained patients with less than 80% of the normal work capacity, the other those with borderline normal values. The first group showed an average increase of 35% in the initial values during a one-year period of swimming training once a week. The other group with practically normal initial values showed only a slight or negligible increase. Serum lipid levels were unchanged in both groups. No serious side effects were encountered in more than 3000 patients hours. However, no prediction of the risks of this type of training as compared to other forms of physical exercise in patients recovering from myocardial infarction can be made from this study.
For determination of the individual rehabilitation potential in patients after myocardial infarction, factors were extracted which are of importance for exercise capacity and its influence upon rehabilitation measures. Further results of exercise tests were correlated with psychological tests (Freiburg-personality-inventory) and the results of a patients' questionnaire for individual self-assessment, with concerning restitution by means of rehabilitation measures. 147 patients were admitted to a controlled rehabilitation program 10 weeks after myocardial infarction or later. Mean increase of exercise capacity after one year of rehabilitation was 21.6% of the initial test. Significantly greater increases of exercise capacity were achieved in patients with regular attendance particularly in younger patients in comparison with older patients. As evidenced by ergometric test data initially low maximal heart rate, low increase of heart rate, low exercise capacity and low double product were correlated with greater increase of exercise capacity. Patients with anterior-wall myocardial infarction tended to increased exercise capacity more. A relation between "psychosomatic disturbance" at onset of rehabilitation and a greater increase of exercise capacity could be determined as a trend. Connections between psychosocial factors and determinants of exercise capacity in influencing the rehabilitation potential are discussed.
The antianginal effect of perhexiline was evaluated in a placebo-controlled double-blind study of 20 patients with stable angina pectoris. Only patients with documented myocardial infarction of more than 6 months' standing and with ST-segment depression on exercise were admitted to the study. Objective parameters of bicycle stress tests at a submaximum level of 50 watts and a maximum exercise level were evaluated. Subjective data such as nitroglycerin consumption and incidence of anginal attacks per week were obtained from the patients' self-maintained records. No negative chronotropic effect of perhexiline was found at rest. At a submaximum exercise level with unchanged double-product, a significantly lower heart rate (p less than 0.05) and a significant reduction in ST-segment depression were observed in comparison with the placebo. At maximum exercise level an increase in exercise tolerance of 8.1% and in aerobic capacity of 8.3% resulted in a significant increase in the double-product (p less than 0.01), with a shift in the blood pressure/heart rate ratio. Discontinuation of exercise occurred at the same heart rate, but at a markedly higher level of exercise attainment. Heart rate on exercise proved to be the most valuable parameter in this study for the evaluation of the aerobic capacity of the individual patient. Nitroglycerin consumption and frequency of anginal attacks per week were reduced, but were not of statistical significance. Side-effects occurred in 6 patients, but these did not require termination or reduction of medication. The selective effect on heart rate during exercise opens a new field of application for perhexiline in comparison with beta-blocking agents.
The antihypertensive effect of atenolol, a cardioselective beta-blocker, was examined in 8 patients with essential hypertension. The most important haemodynamic changes observed were a significant reduction in heart rate (reduction in maximum heart rate at the end of symptom-limited exercise by 23% p less than 0.01) and a moderate fall in systolic blood pressure (reduction at submaximum level of exercise by 22%, p less than 0.01). The antihypertensive effect was attributable in half the patients to a drop in peripheral vascular resistance and in the other half evenly to a predominant reduction in cardiac output or to a reduction in both parameters. In view of the compensatory rise in stroke volume a significant reduction in cardiac output was not found. Symptom-limited exercise tolerance was increased in all patients. These results lead to the conclusion that the antihypertensive action of the cardioselective beta-blocker, atenolol is based on a lowering of the increased peripheral vascular resistance and a reduction in cardiac output; the latter mechanism is predominantly found in patients with hyperkinetic features.
Maximal work endurance of heart and circulation measured by submaximal work load on an ergometer can be estimated with reasonable accuracy by means of the physical working capacity 170 (PWC 170) only in healthy individuals aged 30 years or below. Limitation of exercise by pulmonary factors does not appear to bias the results essentially. In healthy people aged 40 or over, the risk of miscalculating maximal working ability based on PWC 170 increases considerably despite maintenance of high statistical correlation to maximal work load. In patients with coronary heart disease, there is no statistical correlation between PWC 170 and maximal work load; therefore, symptom-limited ergometry is required in these patients. For the assessment of quality in follow-up tests, the watt-pulse at submaximal work load appears to be the most adequate parameter. It is recommended that submaximal tests be also carried out in a rectangular-triangular manner, for the purpose of comparison with symptom-limited tests and for evaluation of changes in the dynamics of pulse and blood pressure regulation.
The effects of high altitude (3000 m, low-pressure chamber) on maximum exercise and maximum oxygen uptake were studied in four normal subjects. In order to separate the effects of hypobaria and of hypoxia, exercise testing was performed under normoxic, hypobaric conditions and compared with the results under normoxic, normobaric conditions. There was no significant difference in performance, nor in the effects of exercise on the measured cardiovascular parameters.