1,720,997 research outputs found
Effects of Antihypertensive Drugs on Central Blood Pressure in Humans: A Preliminary Observation
No full textBACKGROUND: Central blood pressure (BP) is considered a better predictor of cardiovascular events than brachial BP. Modifications of central, beyond brachial BP, can be assessed by pressure amplification, a potential new cardiovascular risk factor. Comparison between drugs' effect on central hemodynamics has been poorly studied. Our aim was to assess the hemodynamic effect of a 12-week treatment with amlodipine 5mg, or candesartan 8mg, or indapamide sustained-release 1.5mg, in comparison with placebo.
METHODS: We analyzed 145 out-patients with essential hypertension in primary prevention enrolled in the Natrilix SR Versus Candesartan and Amlodipine in the Reduction of Systolic Blood Pressure in Hypertensive Patients (X-CELLENT) study, a multicenter, randomized, double-blinded, placebo-controlled trial. Arterial stiffness, central BP, pressure amplification, and wave reflection were measured by applanation tonometry.
RESULTS: Baseline characteristics of patients were homogeneous between groups. After treatment, we found that active drugs produced similar reduction of both central and peripheral BPs, with no significant interdrug differences (all P < 0.05; excluded peripheral pulse pressure, compared with placebo). Second, amlodipine (1.9% ± 15.3%), candesartan (3.0% ± 14.6%) and indapamide (4.1% ± 14.4%) all increased pulse pressure amplification, but only indapamide was statistically different from placebo (P = 0.02). Finally, no significant changes were observed on pulse wave velocity, heart rate, and augmentation index.
CONCLUSIONS: The 3 antihypertensive drugs similarly reduced peripheral and central BP, as compared with placebo, but a significant increase in pulse pressure amplification was obtained only with indapamide, independently of arterial stiffness modifications
Central hemodynamic modifications in diabetes mellitus.
No full textArterial stiffness in hypertension is markedly influenced by age, mean arterial pressure (MAP) and heart rate, whereas factors influencing this parameter in diabetes mellitus are not yet fully understood. The aim of our study was to compare central hemodynamics in diabetics (n = 126) versus non-diabetic controls (n = 203), most of whom were hypertensive, and with similar MAP. Anthropometric, laboratory and clinical measurements were collected. Hemodynamic parameters (central blood pressure, aortic pulse wave velocity [PWV], augmentation index [AIx] and pulse pressure amplification [PPA]) were measured using applanation tonometry. PWV and AIx were significantly higher in diabetics, after adjustment for age, gender, MAP, and heart rate. After further adjustment for metabolic syndrome, only the difference in PWV persisted (P < 0.0001). PPA was marginally altered though not significantly. In diabetics, PWV did not correlate with MAP, suggesting that other structural alterations, resulting from insulin resistance, may account for diabetic arterial stiffening to a greater extent than, and independently of, blood pressure. Chronic treatment with insulin was associated with increased PWV, independently of blood pressure, diabetes control and duration, or other common confounding variables. In conclusion, hypertensive diabetics had greater arterial stiffness than hypertensive controls. In diabetes, multiple factors affect arterial stiffening independently of hemodynamic status. Notably, insulin therapy (IT) is associated with more severe arterial stiffness, suggesting a consistent relationship between these parameters. It remains to be determined whether IT should be considered as a marker of diabetes severity that leads to increased arterial stiffness, or whether it has a direct/indirect effect on arterial wall modifications
Heart disease and changes in pulse wave velocity and pulse pressure amplification in the elderly over 80 years: the PARTAGE Study.
No full textPulse pressure amplification, pressure waveform calibration and clinical applications.
No full textObtaining pulse pressure non-invasively from applanation tonometry requires the calibration of pressure waveform with brachial systolic and diastolic blood pressure. In the literature, several calibration methodologies are applied, and clinical studies disagree about the predictive value of central hemodynamic parameters. Our aim was to compare 4 calibration methodologies and assess the usefulness of pulse pressure amplification as an index independent of calibration. We investigated 108 subjects with tonometry in carotid, femoral, brachial, radial and dorsalis-pedis arteries; pulse pressure amplification between arterial waveforms was calculated. Four methods to calibrate the waveforms were compared: the 1/3 rule, the 40% rule, the integral of radial and brachial waveforms. Pulse pressure amplification in 5 arterial territories (carotid-femoral, carotid-brachial, carotid-radial and carotid-pedis amplifications; femoral-pedis amplification) was studied. Pulse pressure was successfully measured non-invasively at the 5 arterial sites. Pulse pressure was markedly dependent on calibration, with differences up to 18 mmHg between methods. Calculation of pulse pressure amplification eliminated effects of calibration method. Furthermore, pulse pressure amplifications in the 5 arterial sites presented a distinct pattern of clinical/biological determinants: heart rate and body height were common determinants of carotid to brachial, radial and femoral amplifications; diabetes was related to carotid to brachial amplification and pulse wave velocity to femoral to pedis amplification. In conclusion, the calibration of pulse pressure will influence results of clinical trials, but calculation of pulse pressure amplification can avoid this. We also suggest that the alteration of amplification in each arterial territory might be considered as a signal of clinical/subclinical damage
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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