1,720,966 research outputs found
Pulse wave velocity testing in the Baltimore longitudinal study of aging.
No full textCarotid-femoral pulse wave velocity is considered the gold standard for measurements of central arterial stiffness obtained through noninvasive methods(1). Subjects are placed in the supine position and allowed to rest quietly for at least 10 min prior to the start of the exam. The proper cuff size is selected and a blood pressure is obtained using an oscillometric device. Once a resting blood pressure has been obtained, pressure waveforms are acquired from the right femoral and right common carotid arteries. The system then automatically calculates the pulse transit time between these two sites (using the carotid artery as a surrogate for the descending aorta). Body surface measurements are used to determine the distance traveled by the pulse wave between the two sampling sites. This distance is then divided by the pulse transit time resulting in the pulse wave velocity. The measurements are performed in triplicate and the average is used for analysis
Early contribution of arterial wave reflection to left ventricular relaxation abnormalities in a community-dwelling population of normotensive and untreated hypertensive men and women.
No full textWe examined the contribution of arterial wave reflection to early abnormalities in left ventricular relaxation, whether this association was modified by gender or hypertension and the role of reflected wave timing and amplitude. We studied a cohort of normotensive and untreated essential hypertensive Taiwanese participants (675 men, 601 women, mean age 52 years). Doppler flow and applanation tonometry were performed to assess carotid-femoral pulse wave velocity (PWV) and augmentation index (AI). Diastolic parameters including the ratio between the peak velocity of early and late diastolic mitral inflow (E/A), E-deceleration time and left atrial (LA) diameter were measured by echocardiography. In multivariate models predicting E/A, women were more likely to have lower E/A than men (β=-0.08, P<0.001). AI was significantly associated with lower E/A in both men (β=-0.09, P=0.005) and women (β=-0.12, P<0.001) independent of PWV. Inclusion of AI in the overall model reduced the gender difference in E/A by 61% and rendered it nonsignificant. There was a significant interaction between AI and hypertension (P=0.02). The inverse association between AI and E/A was significant only in normotensive men and women, and only for the amplitude but not timing of the reflected wave. In conclusion, the contribution of wave reflection to left ventricular diastolic dysfunction was independent of arterial stiffness, more pronounced in normotensive individuals and explained a significant portion of the gender difference in diastolic function
Impact of Central Obesity on the Estimation of Carotid-Femoral Pulse Wave Velocity.
No full textBACKGROUND:
Studies have found that central obesity is associated with higher carotid-femoral pulse wave velocity (PWV). However, traveled distance (TD) measured over the body surface can be substantially overestimated with wider waist circumference (WC). We sought to investigate whether central obesity biases the estimation of PWV and whether this bias explains the association between PWV and different measures of adiposity.
METHODS:
Seven hundred eleven participants (49.5% men) from the Baltimore Longitudinal Study of Aging with PWV, anthropometrics, and quantification of different fat depots by computed tomography and dual x-ray absorptiometry were included. TD and relative PWV were estimated with a tape measure over the body surface or linear distances taken from radiological images, unaffected by obesity.
RESULTS:
A significant association was found between wider WC and a greater difference between the 2 TD measurements and their respective PWV in both sexes (r ≥ 0.34; P < 0.001). This overestimation bias appeared to be generally higher in women than men (0.27 m/sec for each unit increase in WC; P < 0.0001). When TD estimated over the body surface was used to calculate PWV, greater WC, total body fat, subcutaneous fat, and visceral fat were all associated with higher PWV (P < 0.05 for all). However, when PWV was calculated using TD estimated from radiological images or body height, only the association with visceral fat held significant.
CONCLUSIONS:
When TD is measured over the body surface, the role of obesity on PWV is substantially overestimated. After accounting for this bias, PWV was still independently associated with visceral fat but not with other measures of adiposity, confirming its contribution to arterial stiffening
Prevalence, clinical correlates, and functional impact of subaortic ventricular septal bulge (from the Baltimore Longitudinal Study of Aging).
No full textA localized hypertrophy of the subaortic segment of the ventricular septum-ventricular septal bulge (VSB)-has been frequently described in series of elderly population, but its prevalence with age, clinical correlates, and impact on cardiac function and exercise capacity remain uncertain. We explored these associations in a cross-sectional sample without known cardiac disease from the Baltimore Longitudinal Study of Aging. We randomly selected 700 participants (50% men, mean age 64 ± 15, range 26 to 95 years) and reviewed their echocardiograms. We identified 28 men and 21 women with VSB (7% overall prevalence). The prevalence of VSB significantly increased with age in both genders (p <0.0001). In multivariate logistic regression including hypertension and other cardiovascular risk factors, only age displayed a significant independent association with VSB (OR 1.06 per year, 95% confidence interval 1.03 to 1.10, p = 0.0001). After multiple adjustments, participants with VSB compared with those without had enhanced global left ventricular contractility (fractional shortening 41 ± 1.3 vs 38 ± 0.3%, p = 0.04; ejection fraction 71 ± 1.6 vs 67 ± 0.4%, p = 0.06; systolic velocity of the mitral annulus 8.4 ± 0.1 vs 8.9 ± 0.3, p = 0.06), and larger aortic root diameters (3.3 ± 0.06 vs 3.1 ± 0.02 cm, p = 0.02). In subgroup of participants who completed a maximal treadmill test (177 women and 196 men), those with VSB (19, 5.1%) had significantly lower peak oxygen consumption than their counterparts (19.6 ± 3.8 vs 22.9 ± 6.6 ml/kg/min, p = 0.03). However, this association was no longer significant after multiple adjustments. In conclusion, the presence of VSB is independently associated with older age and determines enhanced left ventricular contractility, without any evident impact on exercise capacity
Longitudinal trajectories of arterial stiffness and the role of blood pressure: the Baltimore Longitudinal Study of Aging.
No full textCarotid-femoral pulse wave velocity (PWV), a marker of arterial stiffness, is an established independent cardiovascular risk factor. Little information is available on the pattern and determinants of the longitudinal change in PWV with aging. Such information is crucial to elucidating mechanisms underlying arterial stiffness and the design of interventions to retard it. Between 1988 and 2013, we collected 2 to 9 serial measures of PWV in 354 men and 423 women of the Baltimore Longitudinal Study of Aging, who were 21 to 94 years of age and free of clinically significant cardiovascular disease. Rates of PWV increase accelerated with advancing age in men more than women, leading to sex differences in PWV after the age of 50 years. In both sexes, not only systolic blood pressure (SBP) ≥140 mm Hg but also SBP of 120 to 139 mm Hg was associated with steeper rates of PWV increase compared with SBP<120 mm Hg. Furthermore, there was a dose-dependent effect of SBP in men with marked acceleration in PWV rate of increase with age at SBP ≥140 mm Hg compared with SBP of 120 to 139 mm Hg. Except for waist circumference in women, no other traditional cardiovascular risk factors predicted longitudinal PWV increase. In conclusion, the steeper longitudinal increase of PWV in men than women led to the sex difference that expanded with advancing age. Age and SBP are the main longitudinal determinants of PWV, and the effect of SBP on PWV trajectories exists even in the prehypertensive range
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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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