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Senkuei Hsu - One of the best experts on this subject based on the ideXlab platform.
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broadband eight port Forward Wave directional couplers and four way differential phase shifter
IEEE Transactions on Microwave Theory and Techniques, 2018Co-Authors: Huiling Ting, Senkuei HsuAbstract:We propose a broadband eight-port Forward-Wave directional coupler (FWDC) with the dually symmetric structure. The novel coupler approximately achieves broadband impedance matching of the four modes. In addition, it can also provide almost constant phase differences among the four modes over a wide frequency range. Therefore, an eight-port FWDC with a broad bandwidth can be expected. Based on the Bloch–Floquet theorem, we build the equivalent models to predict the propagation properties. Also, a complete design procedure for the arbitrary power division is provided. Two samples are fabricated on Duroid substrate. Both measured and simulation results are shown for comparison and have good consistency. The achieved FBW is 47% for 0.5-dB variation. We also introduce a novel four-way phase shifter, composed of the proposed broadband eight-port FWDC with 0 dB through level and four delay transmission lines. It can support four independent pairs of the phase-shifting routes at the same time. The unique property can be applied to the three-layer broadband $8 \times 8$ Butler Matrix, as shown in this paper. It not only avoids the design of the complex crossovers, but also reduces the number of the needed phase shifters and the total size. A test sample is fabricated and measured. The obtained FBW is 36%. By properly choosing other broadband components, a compact and broadband $8 \times 8$ Butler matrix can be expected.
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miniaturization technique for Forward Wave directional couplers by using open stubs and patterned ground structures
Asia-Pacific Microwave Conference, 2014Co-Authors: Senkuei Hsu, Chenchia TsengAbstract:A novel compact 3-dB Forward-Wave directional coupler using periodic open stubs and patterned ground plane is proposed. Not only can the input impedances of the even and odd modes be matched, but also the phase difference between the two modes is largely enhanced. The size of the proposed coupler can be reduced significantly. A test sample is fabricated on Duroid substrate. The 3.3 dB coupling level of proposed coupler can be measured at 1.47 GHz. The size reduction of proposed structure is about 95 %. Compared to the previous works, the proposed coupler can be designed with a smaller size.
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bandwidth enhancement of 4 times 4 butler matrix using broadband Forward Wave directional coupler and phase difference compensation
IEEE Transactions on Microwave Theory and Techniques, 2013Co-Authors: Tonghong Lin, Senkuei HsuAbstract:A broadband Butler matrix by combining the proposed broadband Forward-Wave directional coupler and a broadband middle network is proposed. Test samples of both the proposed coupler and Butler matrix are fabricated on Ro4003 and the sizes are 0.4 λg × 0.14 λg and 1.02 λg × 1.17 λg, respectively. For the Butler matrix, the amplitudes of the output signals and the phase imbalances between output ports can be kept at an approximately constant level. The errors of phase imbalances can be kept within ±6° from 1.96 GHz to 3.15 GHz and the corresponding fractional bandwidth is 47%.
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a broadband Forward Wave directional coupler using periodic y shaped ground via structures with arbitrary coupling levels
IEEE Transactions on Microwave Theory and Techniques, 2013Co-Authors: Juichih Yen, Senkuei Hsu, Tonghong LinAbstract:A broadband Forward-Wave directional coupler loaded with periodic Y-shaped ground via structures is proposed. Broadband impedance matching of the even and odd modes can be approximately achieved. The proposed coupler can provide an almost constant phase difference between the even and odd modes over a wide frequency range. Therefore, a Forward coupler with broad bandwidth can be expected. Based on the Bloch-Floquet theorem, the Bloch impedances and the electrical lengths of both modes can be predicted with the aid of our simple equivalent models. Also, a complete design procedure for arbitrary coupling level is provided. A test sample is fabricated on a low-temperature co-fired ceramic substrate with coupled-line length 2.02 λg. The coupling level over 1.5 dB can be measured from 4.5 to 10.4 GHz, which corresponds to the fractional bandwidth of 79.2%. To our knowledge, the proposed coupler is the smallest design with such a broad bandwidth.
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size reduction of 3 db microstrip Forward Wave coupler using defected ground structure
Asia-Pacific Microwave Conference, 2011Co-Authors: Senkuei Hsu, Tonghong LinAbstract:A novel 3-dB directional coupler using defected ground structure is demonstrated. The input impedances of even- and odd-mode are perfectly matched and the phase difference between even- and odd-mode is also enhanced. Equivalent models are developed to predict the characteristic impedance and dispersion curve of the proposed structure. A tested sample is fabricated on the Duroid substrate. 3.4 dB coupling level of the proposed coupler is measured at 1.5 GHz. Compared with the microstrip Forward coupler, the proposed coupler can achieve about 95 % size reduction.
Matthew J Budoff - One of the best experts on this subject based on the ideXlab platform.
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resistive and pulsatile arterial load as predictors of left ventricular mass and geometrynovelty and significance the multi ethnic study of atherosclerosis
Hypertension, 2015Co-Authors: Payman Zamani, David R Jacobs, Richard A Kronmal, David A Bluemke, Raymond R Townsend, Daniel Duprez, Scott Lilly, Victor A Ferrari, Joao A C Lima, Matthew J BudoffAbstract:Arterial load is composed of resistive and various pulsatile components, but their relative contributions to left ventricular (LV) remodeling in the general population are unknown. We studied 4145 participants enrolled in the Multi-Ethnic Study of Atherosclerosis, who underwent cardiac MRI and radial arterial tonometry. We computed systemic vascular resistance (SVR=mean arterial pressure/cardiac output) and indices of pulsatile load including total arterial compliance (TAC, approximated as stroke volume/central pulse pressure), Forward Wave amplitude ( P f ), and reflected Wave amplitude ( P b ). TAC and SVR were adjusted for body surface area to allow for appropriate sex comparisons. We performed allometric adjustment of LV mass for body size and sex and computed standardized regression coefficients (β) for each measure of arterial load. In multivariable regression models that adjusted for multiple confounders, SVR (β=0.08; P P P b (β=0.73; P P f (β=−0.23; P =0.001) were significant independent predictors of LV mass. Conversely, TAC (β=−0.43; P P P f (β=−0.18; P =0.004) were independently associated with the LV wall/LV cavity volume ratio. Women demonstrated greater pulsatile load than men, as evidenced by a lower indexed TAC (0.89 versus 1.04 mL/mm Hg per square meter; P 2 ; P
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resistive and pulsatile arterial load as predictors of left ventricular mass and geometry the multi ethnic study of atherosclerosis
Hypertension, 2015Co-Authors: Payman Zamani, David R Jacobs, Daniel A Duprez, Richard A Kronmal, David A Bluemke, Raymond R Townsend, Scott Lilly, Victor A Ferrari, Joao Lima, Matthew J BudoffAbstract:Arterial load is composed of resistive and various pulsatile components, but their relative contributions to left ventricular (LV) remodeling in the general population are unknown. We studied 4145 participants enrolled in the Multi-Ethnic Study of Atherosclerosis, who underwent cardiac MRI and radial arterial tonometry. We computed systemic vascular resistance (SVR=mean arterial pressure/cardiac output) and indices of pulsatile load including total arterial compliance (TAC, approximated as stroke volume/central pulse pressure), Forward Wave amplitude ( P f ), and reflected Wave amplitude ( P b ). TAC and SVR were adjusted for body surface area to allow for appropriate sex comparisons. We performed allometric adjustment of LV mass for body size and sex and computed standardized regression coefficients (β) for each measure of arterial load. In multivariable regression models that adjusted for multiple confounders, SVR (β=0.08; P P P b (β=0.73; P P f (β=−0.23; P =0.001) were significant independent predictors of LV mass. Conversely, TAC (β=−0.43; P P P f (β=−0.18; P =0.004) were independently associated with the LV wall/LV cavity volume ratio. Women demonstrated greater pulsatile load than men, as evidenced by a lower indexed TAC (0.89 versus 1.04 mL/mm Hg per square meter; P 2 ; P
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resistive and pulsatile arterial load as predictors of left ventricular mass and geometry
Hypertension, 2015Co-Authors: Payman Zamani, David R Jacobs, Daniel A Duprez, Richard A Kronmal, David A Bluemke, Raymond R Townsend, Scott Lilly, Victor A Ferrari, Joao A C Lima, Matthew J BudoffAbstract:Arterial load is composed of resistive and various pulsatile components, but their relative contributions to left ventricular (LV) remodeling in the general population are unknown. We studied 4145 participants enrolled in the Multi-Ethnic Study of Atherosclerosis, who underwent cardiac MRI and radial arterial tonometry. We computed systemic vascular resistance (SVR=mean arterial pressure/cardiac output) and indices of pulsatile load including total arterial compliance (TAC, approximated as stroke volume/central pulse pressure), Forward Wave amplitude ( P f ), and reflected Wave amplitude ( P b ). TAC and SVR were adjusted for body surface area to allow for appropriate sex comparisons. We performed allometric adjustment of LV mass for body size and sex and computed standardized regression coefficients (β) for each measure of arterial load. In multivariable regression models that adjusted for multiple confounders, SVR (β=0.08; P P P b (β=0.73; P P f (β=−0.23; P =0.001) were significant independent predictors of LV mass. Conversely, TAC (β=−0.43; P P P f (β=−0.18; P =0.004) were independently associated with the LV wall/LV cavity volume ratio. Women demonstrated greater pulsatile load than men, as evidenced by a lower indexed TAC (0.89 versus 1.04 mL/mm Hg per square meter; P 2 ; P
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resistive and pulsatile arterial load as predictors of left ventricular mass and geometrynovelty and significance
Hypertension, 2015Co-Authors: Payman Zamani, David R Jacobs, Richard A Kronmal, David A Bluemke, Raymond R Townsend, Daniel Duprez, Scott Lilly, Victor A Ferrari, Joao A C Lima, Matthew J BudoffAbstract:Arterial load is composed of resistive and various pulsatile components, but their relative contributions to left ventricular (LV) remodeling in the general population are unknown. We studied 4145 participants enrolled in the Multi-Ethnic Study of Atherosclerosis, who underwent cardiac MRI and radial arterial tonometry. We computed systemic vascular resistance (SVR=mean arterial pressure/cardiac output) and indices of pulsatile load including total arterial compliance (TAC, approximated as stroke volume/central pulse pressure), Forward Wave amplitude ( P f), and reflected Wave amplitude ( P b). TAC and SVR were adjusted for body surface area to allow for appropriate sex comparisons. We performed allometric adjustment of LV mass for body size and sex and computed standardized regression coefficients (β) for each measure of arterial load. In multivariable regression models that adjusted for multiple confounders, SVR (β=0.08; P <0.001), TAC (β=0.44; P <0.001), P b (β=0.73; P <0.001), and P f (β=−0.23; P =0.001) were significant independent predictors of LV mass. Conversely, TAC (β=−0.43; P <0.001), SVR (β=0.22; P <0.001), and P f (β=−0.18; P =0.004) were independently associated with the LV wall/LV cavity volume ratio. Women demonstrated greater pulsatile load than men, as evidenced by a lower indexed TAC (0.89 versus 1.04 mL/mm Hg per square meter; P <0.0001), whereas men demonstrated a higher indexed SVR (34.0 versus 32.8 Wood Units×m2; P <0.0001). In conclusion, various components of arterial load differentially associate with LV hypertrophy and concentric remodeling. Women demonstrated greater pulsatile load than men. For both LV mass and the LV wall/LV cavity volume ratio, the loading sequence (ie, early load versus late load) is an important determinant of LV response to arterial load. # Novelty and Significance {#article-title-49}
J H Booske - One of the best experts on this subject based on the ideXlab platform.
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impact of random fabrication errors on backward Wave small signal gain in traveling Wave tubes with finite space charge electron beams
Journal of Applied Physics, 2013Co-Authors: S Sengele, M L Barsanti, T A Hargreaves, C M Armstrong, J H Booske, Y Y LauAbstract:A one-dimensional small-signal theory for the backward-Wave mode in a traveling-Wave tube (TWT) is developed, which includes the effects of random fabrication errors. This is of interest since the backward-Wave mode is the spatial harmonic typically responsible for instability in a TWT. The described model examines how gain and instantaneous 1-dB bandwidth of the backward-Wave mode is affected by random fabrication errors, which are modeled as random perturbations of the phase velocity, interaction impedance, and loss along the TWT's length. Random variation of the phase velocity is found to have the largest effect on both the backward-Wave gain and the bandwidth while having only a minor effect on fundamental, Forward-Wave mode behavior.
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impact of random fabrication errors on fundamental Forward Wave small signal gain and bandwidth in traveling Wave tubes with finite space charge electron beams
IEEE Transactions on Electron Devices, 2013Co-Authors: S Sengele, M L Barsanti, T A Hargreaves, C M Armstrong, J H BooskeAbstract:The 1-D small-signal theory for the fundamental spatial harmonic mode developed by Pengvanich et al. is adapted to include the effect of space charge forces in the electron beam. This model allows us to look at how traveling-Wave tube (TWT) performance is affected by random fabrication errors, which are modeled as random perturbations of the phase velocity, interaction impedance, and loss along the TWT's length. In particular, we examine the effect on TWT gain and instantaneous 1-dB bandwidth. Random variation of the phase velocity is found to have the largest effect on both the gain and bandwidth, but the impact is reduced as the amount of space charge in the beam is increased.
Gary F Mitchell - One of the best experts on this subject based on the ideXlab platform.
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relation of central arterial stiffness to incident heart failure in the community
Journal of the American Heart Association, 2015Co-Authors: Connie W Tsao, Martin G Larson, Naomi M Hamburg, Joseph A Vita, Daniel Levy, Emelia J Benjamin, Gary F Mitchell, Asya Lyass, Ramachandran S VasanAbstract:Background Arterial stiffness, pressure pulsatility, and Wave reflection are associated with cardiovascular disease. Left ventricular function is coupled to proximal aortic properties, but the association of central aortic stiffness and hemodynamics with incident clinical heart failure (HF) is not well described. Methods and Results Framingham Study participants without clinical HF (n=2539, mean age 64 years, 56% women) underwent applanation tonometry to measure carotid‐femoral pulse Wave velocity (CFPWV), central pulse pressure, Forward Wave amplitude, and augmentation index. CFPWV was inverse‐transformed to reduce heteroscedasticity and multiplied by −1 to restore effect direction (iCFPWV). Over 10.1 (range 0.04–12.9) years, 170 HF events developed. In multivariable‐adjusted analyses, iCFPWV was associated with incident HF in a continuous, graded fashion (hazards ratio [HR] per SD unit [SDU] 1.29, 95% confidence interval [CI] 1.02–1.64, P =0.037). iCFPWV was associated with HF with reduced ejection fraction (HR=1.69/SDU, 95% CI 1.19–2.42, P =0.0037) in age‐ and sex‐adjusted models, which was attenuated in multivariable‐adjusted models ( P =0.065). Central pulse pressure and Forward Wave amplitude were associated with HF in age‐ and sex‐adjusted models (per SDU, HR=1.20, 95% CI 1.06–1.37, P =0.006, and HR=1.15, 95% CI 1.01–1.31, P =0.036, respectively), but not in multivariable‐adjusted models (both P ≥0.28). Augmentation index was not associated with HF risk ( P ≥0.19 in all models). Conclusions In our prospective investigation of a large community‐based sample of middle‐aged to elderly individuals, greater aortic stiffness (reflected by higher iCFPWV) was associated with increased risk of HF. Future studies may investigate the impact of modifying aortic stiffness in reducing the community burden of HF.
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cross sectional relations of arterial stiffness pressure pulsatility Wave reflection and arterial calcification
Arteriosclerosis Thrombosis and Vascular Biology, 2014Co-Authors: Connie W Tsao, Daniel Levy, Emelia J Benjamin, Ramachandran S Vasan, Karol M Pencina, Joseph M Massaro, Udo Hoffmann, Christopher J Odonnell, Gary F MitchellAbstract:Objective—Arterial hemodynamics and vascular calcification are associated with increased risk for cardiovascular disease, but their inter-relations remain unclear. We sought to examine the associations of arterial stiffness, pressure pulsatility, and Wave reflection with arterial calcification in individuals free of prevalent cardiovascular disease. Approach and Results—Framingham Heart Study Third Generation and Offspring Cohort participants free of cardiovascular disease underwent applanation tonometry to measure arterial stiffness, pressure pulsatility, and Wave reflection, including carotid-femoral pulse Wave velocity, central pulse pressure, Forward Wave amplitude, and augmentation index. Participants in each cohort (n=1905, 45±6 years and n=1015, 65±9 years, respectively) underwent multidetector computed tomography to assess the presence and quantity of thoracic aortic calcification, abdominal aortic calcification, and coronary artery calcification. In multivariable-adjusted models, both higher carotid-femoral pulse Wave velocity and central pulse pressure were associated with greater thoracic aortic calcification and abdominal aortic calcification, whereas higher augmentation index was associated with abdominal aortic calcification. Among the tonometry measures, carotid-femoral pulse Wave velocity was the strongest correlate of all calcification measures in multivariable-adjusted models (odds ratio per SD for thoracic aortic calcification, 2.69 [95% confidence interval, 2.17–3.35]; abdominal aortic calcification, 1.47 [95% confidence interval, 1.26–1.73]; and coronary artery calcification, 1.48 [95% confidence interval, 1.28–1.72]; all P<0.001, respectively). We observed stronger relations of carotid-femoral pulse Wave velocity, central pulse pressure, and Forward Wave amplitude with nearly all continuous calcification measures in the younger Third Generation Cohort as compared with the Offspring Cohort. Conclusions—In community-dwelling individuals without prevalent cardiovascular disease, abnormal central arterial hemodynamics were positively associated with vascular calcification and were observed at younger ages than previously recognized. The mechanisms of these associations may be bidirectional and deserve further study. (Arterioscler Thromb Vasc Biol. 2014;34:2495-2500.)
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Forward and backward Wave morphology and central pressure augmentation in men and women in the framingham heart study
Hypertension, 2014Co-Authors: Alyssa A Torjesen, Na Wang, Martin G Larson, Naomi M Hamburg, Joseph A Vita, Daniel Levy, Emelia J Benjamin, Ramachandran S Vasan, Gary F MitchellAbstract:Central pressure augmentation is associated with greater backward Wave amplitude and shorter transit time and is higher in women for reasons only partially elucidated. Augmentation also is affected by left ventricular function and shapes of the Forward and backward Waves. The goal of this study was to examine the relative contributions of Forward and backward Wave morphology to central pressure augmentation in men and women. From noninvasive measurements of central pressure and flow in 7437 participants (4036 women) aged from 19 to 90 years (mean age, 51 years), we calculated several variables: augmentation index, backward Wave arrival time, reflection factor, Forward Wave amplitude, Forward Wave peak width, and slope of the backward Wave upstroke. Linear regression models for augmentation index, adjusted for height and heart rate, demonstrated nonlinear relations with age (age: B=4.6±0.1%; P<0.001; age2: B=−4.2±0.1%; P<0.001) and higher augmentation in women (B=4.5±0.4%; P<0.001; model R2=0.35). Addition of reflection factor and backward Wave arrival time improved model fit (R2=0.62) and reduced the age coefficients: age (B=2.3±0.1%; P<0.001) and age2 (B=−2.2±0.1%; P<0.001). Addition of width of Forward Wave peak, slope of backward Wave upstroke, and Forward Wave amplitude further improved model fit (R2=0.75) and attenuated the sex coefficient (B=1.9±0.2%; P<0.001). Thus, shape and amplitude of the Forward Wave may be important correlates of augmentation index, and part of the sex difference in augmentation index may be explained by Forward and backward Wave morphology.
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hemodynamic correlates of blood pressure across the adult age spectrum noninvasive evaluation in the framingham heart study
Circulation, 2010Co-Authors: Gary F Mitchell, Na Wang, Martin G Larson, Naomi M Hamburg, Joseph A Vita, Daniel Levy, Emelia J Benjamin, Joseph Palmisano, Ramachandran S VasanAbstract:Background—Systolic blood pressure and pulse pressure are substantially higher in older adults. The relative contributions of increased Forward versus reflected pressure Wave amplitude or earlier arrival of the reflected Wave to elevated pulse pressure remain controversial. Methods and Results—We measured proximal aortic pressure and flow, Forward pressure Wave amplitude, global Wave reflection, reflected Wave timing, and pulse Wave velocity noninvasively in 6417 (age range, 19 to 90 years; 53 women) Framingham Heart Study Third Generation and Offspring participants. Variation in Forward Wave amplitude paralleled pulse pressure throughout adulthood. In contrast, Wave reflection and pulse pressure were divergent across adulthood: In younger participants, pulse pressure was lower and Wave reflection was higher with advancing age, whereas in older participants, pulse pressure was higher and Wave reflection was lower with age. Reflected Wave timing differed modestly across age groups despite considerable diff...
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changes in arterial stiffness and Wave reflection with advancing age in healthy men and women the framingham heart study
Hypertension, 2004Co-Authors: Gary F Mitchell, Martin G Larson, Joseph A Vita, Emelia J Benjamin, Ramachandran S Vasan, Helen Parise, Michelle J Keyes, Daniel LevyAbstract:With advancing age, arterial stiffness and Wave reflections increase and elevate systolic and pulse pressures. An elevated central pulse pressure is generally ascribed to increased Wave reflection and portends an unfavorable prognosis. Using arterial tonometry, we evaluated central (carotid-femoral) and peripheral (carotid-brachial) pulse Wave velocity, amplitudes of Forward and reflected pressure Waves, and augmentation index in 188 men and 333 women in the Framingham Heart Study offspring cohort who were free of clinical cardiovascular disease, hypertension, diabetes, smoking within the past 12 months, dyslipidemia, and obesity. In multivariable linear regression models, advancing age was the predominant correlate of higher carotid-femoral pulse Wave velocity; other correlates were higher mean arterial pressure, heart rate, and triglycerides and walk test before tonometry (model R 2=0.512, P <0.001). A similar model was obtained for carotid-brachial pulse Wave velocity (model R 2=0.227, P <0.001), although the increase with advancing age was smaller. Owing to different relations of age to central and peripheral stiffness measures, carotid-femoral pulse Wave velocity was lower than carotid-brachial pulse Wave velocity before age 50 years but exceeded it thereafter, leading to reversal of the normal central-to-peripheral arterial stiffness gradient. In this healthy cohort with a minimal burden of cardiovascular disease risk factors, an age-related increase in aortic stiffness, as compared with peripheral arterial stiffness, was associated with increasing Forward Wave amplitude and pulse pressure and reversal of the arterial stiffness gradient. This phenomenon may facilitate Forward transmission of potentially deleterious pressure pulsations into the periphery.
Ramachandran S Vasan - One of the best experts on this subject based on the ideXlab platform.
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relation of central arterial stiffness to incident heart failure in the community
Journal of the American Heart Association, 2015Co-Authors: Connie W Tsao, Martin G Larson, Naomi M Hamburg, Joseph A Vita, Daniel Levy, Emelia J Benjamin, Gary F Mitchell, Asya Lyass, Ramachandran S VasanAbstract:Background Arterial stiffness, pressure pulsatility, and Wave reflection are associated with cardiovascular disease. Left ventricular function is coupled to proximal aortic properties, but the association of central aortic stiffness and hemodynamics with incident clinical heart failure (HF) is not well described. Methods and Results Framingham Study participants without clinical HF (n=2539, mean age 64 years, 56% women) underwent applanation tonometry to measure carotid‐femoral pulse Wave velocity (CFPWV), central pulse pressure, Forward Wave amplitude, and augmentation index. CFPWV was inverse‐transformed to reduce heteroscedasticity and multiplied by −1 to restore effect direction (iCFPWV). Over 10.1 (range 0.04–12.9) years, 170 HF events developed. In multivariable‐adjusted analyses, iCFPWV was associated with incident HF in a continuous, graded fashion (hazards ratio [HR] per SD unit [SDU] 1.29, 95% confidence interval [CI] 1.02–1.64, P =0.037). iCFPWV was associated with HF with reduced ejection fraction (HR=1.69/SDU, 95% CI 1.19–2.42, P =0.0037) in age‐ and sex‐adjusted models, which was attenuated in multivariable‐adjusted models ( P =0.065). Central pulse pressure and Forward Wave amplitude were associated with HF in age‐ and sex‐adjusted models (per SDU, HR=1.20, 95% CI 1.06–1.37, P =0.006, and HR=1.15, 95% CI 1.01–1.31, P =0.036, respectively), but not in multivariable‐adjusted models (both P ≥0.28). Augmentation index was not associated with HF risk ( P ≥0.19 in all models). Conclusions In our prospective investigation of a large community‐based sample of middle‐aged to elderly individuals, greater aortic stiffness (reflected by higher iCFPWV) was associated with increased risk of HF. Future studies may investigate the impact of modifying aortic stiffness in reducing the community burden of HF.
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cross sectional relations of arterial stiffness pressure pulsatility Wave reflection and arterial calcification
Arteriosclerosis Thrombosis and Vascular Biology, 2014Co-Authors: Connie W Tsao, Daniel Levy, Emelia J Benjamin, Ramachandran S Vasan, Karol M Pencina, Joseph M Massaro, Udo Hoffmann, Christopher J Odonnell, Gary F MitchellAbstract:Objective—Arterial hemodynamics and vascular calcification are associated with increased risk for cardiovascular disease, but their inter-relations remain unclear. We sought to examine the associations of arterial stiffness, pressure pulsatility, and Wave reflection with arterial calcification in individuals free of prevalent cardiovascular disease. Approach and Results—Framingham Heart Study Third Generation and Offspring Cohort participants free of cardiovascular disease underwent applanation tonometry to measure arterial stiffness, pressure pulsatility, and Wave reflection, including carotid-femoral pulse Wave velocity, central pulse pressure, Forward Wave amplitude, and augmentation index. Participants in each cohort (n=1905, 45±6 years and n=1015, 65±9 years, respectively) underwent multidetector computed tomography to assess the presence and quantity of thoracic aortic calcification, abdominal aortic calcification, and coronary artery calcification. In multivariable-adjusted models, both higher carotid-femoral pulse Wave velocity and central pulse pressure were associated with greater thoracic aortic calcification and abdominal aortic calcification, whereas higher augmentation index was associated with abdominal aortic calcification. Among the tonometry measures, carotid-femoral pulse Wave velocity was the strongest correlate of all calcification measures in multivariable-adjusted models (odds ratio per SD for thoracic aortic calcification, 2.69 [95% confidence interval, 2.17–3.35]; abdominal aortic calcification, 1.47 [95% confidence interval, 1.26–1.73]; and coronary artery calcification, 1.48 [95% confidence interval, 1.28–1.72]; all P<0.001, respectively). We observed stronger relations of carotid-femoral pulse Wave velocity, central pulse pressure, and Forward Wave amplitude with nearly all continuous calcification measures in the younger Third Generation Cohort as compared with the Offspring Cohort. Conclusions—In community-dwelling individuals without prevalent cardiovascular disease, abnormal central arterial hemodynamics were positively associated with vascular calcification and were observed at younger ages than previously recognized. The mechanisms of these associations may be bidirectional and deserve further study. (Arterioscler Thromb Vasc Biol. 2014;34:2495-2500.)
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Forward and backward Wave morphology and central pressure augmentation in men and women in the framingham heart study
Hypertension, 2014Co-Authors: Alyssa A Torjesen, Na Wang, Martin G Larson, Naomi M Hamburg, Joseph A Vita, Daniel Levy, Emelia J Benjamin, Ramachandran S Vasan, Gary F MitchellAbstract:Central pressure augmentation is associated with greater backward Wave amplitude and shorter transit time and is higher in women for reasons only partially elucidated. Augmentation also is affected by left ventricular function and shapes of the Forward and backward Waves. The goal of this study was to examine the relative contributions of Forward and backward Wave morphology to central pressure augmentation in men and women. From noninvasive measurements of central pressure and flow in 7437 participants (4036 women) aged from 19 to 90 years (mean age, 51 years), we calculated several variables: augmentation index, backward Wave arrival time, reflection factor, Forward Wave amplitude, Forward Wave peak width, and slope of the backward Wave upstroke. Linear regression models for augmentation index, adjusted for height and heart rate, demonstrated nonlinear relations with age (age: B=4.6±0.1%; P<0.001; age2: B=−4.2±0.1%; P<0.001) and higher augmentation in women (B=4.5±0.4%; P<0.001; model R2=0.35). Addition of reflection factor and backward Wave arrival time improved model fit (R2=0.62) and reduced the age coefficients: age (B=2.3±0.1%; P<0.001) and age2 (B=−2.2±0.1%; P<0.001). Addition of width of Forward Wave peak, slope of backward Wave upstroke, and Forward Wave amplitude further improved model fit (R2=0.75) and attenuated the sex coefficient (B=1.9±0.2%; P<0.001). Thus, shape and amplitude of the Forward Wave may be important correlates of augmentation index, and part of the sex difference in augmentation index may be explained by Forward and backward Wave morphology.
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hemodynamic correlates of blood pressure across the adult age spectrum noninvasive evaluation in the framingham heart study
Circulation, 2010Co-Authors: Gary F Mitchell, Na Wang, Martin G Larson, Naomi M Hamburg, Joseph A Vita, Daniel Levy, Emelia J Benjamin, Joseph Palmisano, Ramachandran S VasanAbstract:Background—Systolic blood pressure and pulse pressure are substantially higher in older adults. The relative contributions of increased Forward versus reflected pressure Wave amplitude or earlier arrival of the reflected Wave to elevated pulse pressure remain controversial. Methods and Results—We measured proximal aortic pressure and flow, Forward pressure Wave amplitude, global Wave reflection, reflected Wave timing, and pulse Wave velocity noninvasively in 6417 (age range, 19 to 90 years; 53 women) Framingham Heart Study Third Generation and Offspring participants. Variation in Forward Wave amplitude paralleled pulse pressure throughout adulthood. In contrast, Wave reflection and pulse pressure were divergent across adulthood: In younger participants, pulse pressure was lower and Wave reflection was higher with advancing age, whereas in older participants, pulse pressure was higher and Wave reflection was lower with age. Reflected Wave timing differed modestly across age groups despite considerable diff...
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changes in arterial stiffness and Wave reflection with advancing age in healthy men and women the framingham heart study
Hypertension, 2004Co-Authors: Gary F Mitchell, Martin G Larson, Joseph A Vita, Emelia J Benjamin, Ramachandran S Vasan, Helen Parise, Michelle J Keyes, Daniel LevyAbstract:With advancing age, arterial stiffness and Wave reflections increase and elevate systolic and pulse pressures. An elevated central pulse pressure is generally ascribed to increased Wave reflection and portends an unfavorable prognosis. Using arterial tonometry, we evaluated central (carotid-femoral) and peripheral (carotid-brachial) pulse Wave velocity, amplitudes of Forward and reflected pressure Waves, and augmentation index in 188 men and 333 women in the Framingham Heart Study offspring cohort who were free of clinical cardiovascular disease, hypertension, diabetes, smoking within the past 12 months, dyslipidemia, and obesity. In multivariable linear regression models, advancing age was the predominant correlate of higher carotid-femoral pulse Wave velocity; other correlates were higher mean arterial pressure, heart rate, and triglycerides and walk test before tonometry (model R 2=0.512, P <0.001). A similar model was obtained for carotid-brachial pulse Wave velocity (model R 2=0.227, P <0.001), although the increase with advancing age was smaller. Owing to different relations of age to central and peripheral stiffness measures, carotid-femoral pulse Wave velocity was lower than carotid-brachial pulse Wave velocity before age 50 years but exceeded it thereafter, leading to reversal of the normal central-to-peripheral arterial stiffness gradient. In this healthy cohort with a minimal burden of cardiovascular disease risk factors, an age-related increase in aortic stiffness, as compared with peripheral arterial stiffness, was associated with increasing Forward Wave amplitude and pulse pressure and reversal of the arterial stiffness gradient. This phenomenon may facilitate Forward transmission of potentially deleterious pressure pulsations into the periphery.