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Jeffrey T. Kuvin - One of the best experts on this subject based on the ideXlab platform.
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peripheral augmentation index as a biomarker of vascular aging an invasive hemodynamics approach
European Journal of Applied Physiology, 2012Co-Authors: Kevin S. Heffernan, Richard H. Karas, Eshan A Patvardhan, Navin K Kapur, Jeffrey T. KuvinAbstract:We compared two measures of vascular function obtained from digital volume waveforms with measures of target organ damage and novel invasive measures of vascular function as they relate to vascular aging. Aortic pulse pressure amplification, pulsatility, form factor and extent of coronary atherosclerosis (modified Gensini score) were obtained invasively in 59 patients undergoing left heart catheterization. Digital volume waveforms were captured via peripheral arterial tone (PAT) and used to derive augmentation index (Aix) and the pulse wave amplitude-reactive hyperemia index (PWA-RHI). Aix was associated with age (r = 0.50, p < 0.05) and aortic pulsatility (r = 0.45, p < 0.05) and inversely associated with estimated glomerular filtration rate (−0.29, p < 0.05) aortic pulse pressure amplification (r = −0.28, p < 0.05) and aortic form factor (r = −0.38, p < 0.05). Aix was slightly higher in patients with left ventricular hypertrophy (LVH) versus those without left ventricular hypertrophy (30 vs. 14%, p = 0.058). There was no association between Aix and Gensini score. PWA-RHI was not associated with age, estimated glomerular filtration rate or invasive vascular parameters and did not differ in patients with versus without LVH (p = ns). PWA-RHI was inversely associated with Gensini score (r = −0.32, p < 0.05). Aix derived from PAT is correlated with age-associated changes in vascular function and target organ damage but not coronary atherosclerotic burden. PWA-RHI is associated with coronary atherosclerotic burden but is not associated with target organ damage or other measures of vascular aging assessed in this study. Each parameter provides distinct insight into systemic vascular aging and target organ damage.
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peripheral augmentation index and vascular inflammation in autosomal dominant polycystic kidney disease
Nephrology Dialysis Transplantation, 2011Co-Authors: Kevin S. Heffernan, Priya Chandra, Darya Rudym, Dana C Miskulin, Jeffrey T. Kuvin, Richard H. Karas, Mark J Sarnak, Ronald D Perrone, Vandana MenonAbstract:Background. Cardiovascular disease is the leading cause of premature mortality in autosomal dominant polycystic kidney disease (ADPKD). We examined peripheral augmentation index (Aix) as a measure of systemic vascular function and circulating markers of vascular inflammation in patients with ADPKD. Methods. Fifty-two ADPKD patients with hypertension and estimated glomerular filtration rate (eGFR) 0.05). ICAM, P-selectin, E-selectin and sFas were higher and FasL lower in all ADPKD groups compared to controls (P 0.05). According to multiple regression analysis, predictors of Aix in ADPKD included age, height, heart rate and mean arterial pressure (P < 0.05). Vascular inflammatory markers were not predictors of Aix in ADPKD. Conclusions. Systemic vascular dysfunction, manifesting as an increase in Aix and vascular inflammation is evident in young normotensive ADPKD patients with preserved renal function. Vascular inflammation is not associated with elevated Aix in ADPKD.
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augmentation index derived from peripheral arterial tonometry correlates with cardiovascular risk factors
Cardiology Research and Practice, 2011Co-Authors: Eshan A Patvardhan, Kevin S. Heffernan, Richard H. Karas, Jenny Ruan, Michael Hession, Patrick J Warner, Jeffrey T. KuvinAbstract:Background. Augmentation index (Aix) is traditionally obtained from pressure waveforms via arterial applanation tonometry. We sought to evaluate the association between Aix obtained from peripheral arterial tonometry (PAT) with cardiovascular risk factors (CRF) and coronary artery disease (CAD). Methods. 186 patients were enrolled in the study. The presence or absence of CRFs and CAD was assessed in each subject. Aix was calculated by an automated algorithm averaging pulse wave amplitude data obtained via PAT. Central blood pressures were assessed in a subset of patients undergoing clinically indicated cardiac catheterization. Results. An association was observed between Aix and age, heart rate, systolic blood pressure, mean arterial pressure, pulse pressure, body weight and body mass index. Aix was significantly lower in patients with 5 CRFs ( P = .02). CAD+ patients had significantly higher Aix compared to CAD− patients ( P = .008). Area under the ROC curve was 0.604 (P < .01). In patients undergoing cardiac catheterization, after adjusting for age, height and heart rate, Aix was a significant predictor of aortic systolic and pulse pressures (P < .05) Conclusion. Aix derived from PAT correlates with cardiac risk factors and CAD. It may be a useful measure of assessing overall risk for coronary artery disease.
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elevated augmentation index derived from peripheral arterial tonometry is associated with abnormal ventricular vascular coupling
Clinical Physiology and Functional Imaging, 2010Co-Authors: Kevin S. Heffernan, Richard H. Karas, Eshan A Patvardhan, Jenny Ruan, Michael Hession, Jeffrey T. KuvinAbstract:As a measure of late systolic load and systemic vascular function (Borlaug, et al. 2007) the augmentation index (Aix) may be a useful therapeutic target and secondary endpoint (Hashimoto, et al. 2007). Aix is associated with numerous cardiovascular morbidities (Nurnberger, et al. 2002), coronary artery disease (Hayashi, et al. 2002; Weber, et al. 2004), albuminuria (Tsioufis, et al. 2003), and predicts future cardiovascular events (Weber, et al. 2005) and mortality (London, et al. 2001). Moreover, the augmentation of systolic blood pressure owing to wave reflections (i.e. increased late systolic load) reduces left ventricular (LV) systolic and diastolic function (Borlaug, Melenovsky, Redfield, Kessler, Chang, Abraham & Kass 2007), increases LV pressure effort, increases myocardial oxygen demand and reduces coronary perfusion (Hashimoto, Imai & O'Rourke 2007; Hashimoto, et al. 2007; Hashimoto, et al. 2008). This resultant ventricular-vascular mismatch impairs cardiac metabolic efficiency and causes LV hypertrophy (Hashimoto, Nichols, O'Rourke & Imai 2008). Although typically derived from the contour of central and peripheral arterial pressure waveforms (Chen, et al. 1997), Aix can also be derived from digital pulse volume waveforms using finger plethysmography (peripheral arterial tonometry, PAT). Little is known regarding the systemic vascular correlates of Aix derived from PAT. The digital pulse volume waveform is influenced by wave reflections (Chowienczyk, et al. 1999) and correlates with pressure waveforms measured at the finger, radial artery and carotid artery, and changes in the digital volume pulse with perturbation have been shown to be very similar to changes in the pressure waveforms (Millasseau, et al. 2000; Millasseau, et al. 2003). Thus, it is reasonable to speculate that digital Aix derived from PAT may also serve as a proxy of ventricular-vascular load but this has yet to be empirically demonstrated. Ventricular-vascular coupling can be quantified via examination of the ratio of effective arterial elastance and LV end-systolic elastance derived either invasively from catheterization-derived pressure-volume loops or non-invasively from conventional blood pressure measurement and echocardiography (Chen, et al. 2001). Ventricular-vascular uncoupling is associated with low exercise capacity (Chen, et al. 1999; Wong, et al.), has been implicated in the etiology of numerous pathologies (Kass 2005) and has also recently been shown to be associated with B-type natriuretic peptide (BNP) in patients after myocardial infarction and predicts long-term CV mortality in this setting (Antonini-Canterin, et al. 2009). The purpose of this study was to examine the association between PAT-Aix and ventricular-vascular coupling. We hypothesized that elevated PAT-Aix would reflect abnormal ventricular-vascular coupling.
Ian B Wilkinson - One of the best experts on this subject based on the ideXlab platform.
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normal vascular aging differential effects on wave reflection and aortic pulse wave velocity the anglo cardiff collaborative trial acct
Journal of the American College of Cardiology, 2005Co-Authors: Carmel M Mceniery, Ian B Wilkinson, Ahmad Qasem, Ian R Hall, J R CockcroftAbstract:OBJECTIVES The aim of the current investigation was to test the hypothesis that age-related changes in augmentation index (Aix) are more prominent in younger individuals (50 years), whereas changes in aortic stiffness per se are more marked in older individuals (50 years). BACKGROUND Aging exerts a number of deleterious changes in the cardiovascular system, and, in particular, on the large arteries. Previous studies have suggested that Aix and pulse wave velocity (PWV) increase linearly with age, yet epidemiological data concerning pulse pressure suggest that large artery stiffening predominantly occurs later in life. METHODS Peripheral and central blood pressure, augmentation pressure (AP), and Aix were determined in 4,001 healthy, normotensive individuals, aged 18 to 90 years. Aortic and brachial PWV were also determined in a subset of 998 subjects. RESULTS Peripheral and central pulse pressure, AP, Aix, and aortic and brachial PWV all increased significantly with age; however, the age-related changes in Aix and aortic PWV were non-linear, with Aix increasing more in younger individuals, whereas the changes in PWV were more prominent in older individuals. CONCLUSIONS These data suggest that Aix might be a more sensitive marker of arterial stiffening and risk in younger individuals but aortic PWV is likely to be a better measure in older individuals. (J Am Coll Cardiol 2005;46:1753‐60) © 2005 by the American College of Cardiology Foundation Age is one of the most powerful determinants of cardiovascular risk and is associated with a number of deleterious changes in the cardiovascular system (1). Among the more prominent changes are stiffening and dilatation of the large arteries—arteriosclerosis—which has been documented in almost all societies worldwide. Such changes lead to a rise in pulse pressure (PP) and, ultimately, the development of isolated systolic hypertension. This condition affects approximately 50% of individuals over 60 years of age and is associated with considerable excess morbidity and mortality. The importance of large artery stiffening has been further highlighted by the observation that aortic pulse wave velocity (PWV), which is inversely related to distensibility (2), and central augmentation index (Aix), a composite measure that depends on the site and degree of wave reflection (3), are independent predictors of cardiovascular and total mortality in selected patient groups (4‐8). A number of studies have investigated the effects of age on aortic PWV and Aix (9‐12). Most suggest a linear, age-related increase in both indexes across a variety of different populations; however, epidemiological data indicate that PP increases significantly only after the fifth decade, suggesting that stiffening of the large arteries occurs predominantly in later life (13). Moreover, data from invasive studies suggest that the intensity of wave reflection becomes less marked in old age as impedance mismatch reduces (14). Such apparent discrepancies might reflect the fact that the majority of hemodynamic studies have been modest in size and encompassed a relatively narrow age range. Moreover, existing studies have not investigated the interaction between age, large artery stiffness, wave reflection, and PP within a single population. We hypothesized that age-related changes in Aix are more prominent in younger subjects, whereas changes in large artery stiffness per se are more marked in older subjects. The aim of the present study was to test this hypothesis in a large cohort of healthy individuals from the Anglo-Cardiff Collaborative Trial (ACCT) and, in doing so, expand our understanding of the effect of age and gender on these commonly measured parameters of arterial stiffness.
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normal vascular aging differential effects on wave reflection and aortic pulse wave velocity the anglo cardiff collaborative trial acct
Journal of the American College of Cardiology, 2005Co-Authors: Carmel M Mceniery, John R Cockcroft, Ian B Wilkinson, Ahmad Qasem, Ian R Hall, Acct InvestigatorsAbstract:OBJECTIVES The aim of the current investigation was to test the hypothesis that age-related changes in augmentation index (Aix) are more prominent in younger individuals (50 years), whereas changes in aortic stiffness per se are more marked in older individuals (50 years). BACKGROUND Aging exerts a number of deleterious changes in the cardiovascular system, and, in particular, on the large arteries. Previous studies have suggested that Aix and pulse wave velocity (PWV) increase linearly with age, yet epidemiological data concerning pulse pressure suggest that large artery stiffening predominantly occurs later in life. METHODS Peripheral and central blood pressure, augmentation pressure (AP), and Aix were determined in 4,001 healthy, normotensive individuals, aged 18 to 90 years. Aortic and brachial PWV were also determined in a subset of 998 subjects. RESULTS Peripheral and central pulse pressure, AP, Aix, and aortic and brachial PWV all increased significantly with age; however, the age-related changes in Aix and aortic PWV were non-linear, with Aix increasing more in younger individuals, whereas the changes in PWV were more prominent in older individuals. CONCLUSIONS These data suggest that Aix might be a more sensitive marker of arterial stiffening and risk in younger individuals but aortic PWV is likely to be a better measure in older individuals. (J Am Coll Cardiol 2005;46:1753‐60) © 2005 by the American College of Cardiology Foundation Age is one of the most powerful determinants of cardiovascular risk and is associated with a number of deleterious changes in the cardiovascular system (1). Among the more prominent changes are stiffening and dilatation of the large arteries—arteriosclerosis—which has been documented in almost all societies worldwide. Such changes lead to a rise in pulse pressure (PP) and, ultimately, the development of isolated systolic hypertension. This condition affects approximately 50% of individuals over 60 years of age and is associated with considerable excess morbidity and mortality. The importance of large artery stiffening has been further highlighted by the observation that aortic pulse wave velocity (PWV), which is inversely related to distensibility (2), and central augmentation index (Aix), a composite measure that depends on the site and degree of wave reflection (3), are independent predictors of cardiovascular and total mortality in selected patient groups (4‐8). A number of studies have investigated the effects of age on aortic PWV and Aix (9‐12). Most suggest a linear, age-related increase in both indexes across a variety of different populations; however, epidemiological data indicate that PP increases significantly only after the fifth decade, suggesting that stiffening of the large arteries occurs predominantly in later life (13). Moreover, data from invasive studies suggest that the intensity of wave reflection becomes less marked in old age as impedance mismatch reduces (14). Such apparent discrepancies might reflect the fact that the majority of hemodynamic studies have been modest in size and encompassed a relatively narrow age range. Moreover, existing studies have not investigated the interaction between age, large artery stiffness, wave reflection, and PP within a single population. We hypothesized that age-related changes in Aix are more prominent in younger subjects, whereas changes in large artery stiffness per se are more marked in older subjects. The aim of the present study was to test this hypothesis in a large cohort of healthy individuals from the Anglo-Cardiff Collaborative Trial (ACCT) and, in doing so, expand our understanding of the effect of age and gender on these commonly measured parameters of arterial stiffness.
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hemodynamic effects of amlodipine bisoprolol and lisinopril in hypertensive patients after liver transplantation1
Transplantation, 2004Co-Authors: David A J Neal, Morris J Brown, Ian B Wilkinson, Christopher D Byrne, Graeme J M AlexanderAbstract:Background: Hypertension is common after liver transplantation. There are few published data on optimum treatment. Augmentation index (Aix) is a measure of arterial wave reflection determined by pulse wave analysis. Methods: Amlodipine was administered to 24 hypertensive liver transplant recipients. Thirteen patients intolerant of or unresponsive to amlodipine were randomized to a crossover study comparing bisoprolol with lisinopril. Results: With amlodipine, systolic blood pressure (SBP) fell from 154+/-2 mm Hg to 130+/-2 mm Hg, and Aix also fell. With bisoprolol, SBP fell from 154+/-2 mm Hg to 142+/-4 mm Hg, but Aix increased. With lisinopril, SBP fell from 154+/-2 mm Hg to 130+/-5 mm Hg, and Aix also fell (P Conclusions: Amlodipine is an effective treatment for hypertension. The increased Aix with bisoprolol indicates increased wave reflection such that central aortic pressure is reduced less than peripheral SBP. Lisinopril reduces Aix and reduces SBP more than bisoprolol and is the preferred drug.
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inflammation and arterial stiffness in systemic vasculitis a model of vascular inflammation
Arthritis & Rheumatism, 2004Co-Authors: A D Booth, Carmel M Mceniery, S Wallace, John Brown, David Jayne, Ian B WilkinsonAbstract:Objective Arterial stiffness, an independent determinant of cardiovascular risk, is regulated by both structural and functional factors, including endothelium-derived nitric oxide. Endothelial dysfunction is associated with acute and chronic systemic inflammation. However, the role of systemic inflammation in arterial stiffening has not been determined. The aim of this study was to investigate the relationship between inflammation and arterial stiffness in patients with antineutrophil cytoplasmic antibody–associated systemic vasculitis (AASV) as a model of systemic inflammation. Methods Thirty-one patients with AASV (15 with active disease) and 32 age-matched controls were studied. Pulse wave velocity (PWV) and the augmentation index (Aix) were assessed noninvasively and related to serum levels of C-reactive protein (CRP), interleukin-6, and tumor necrosis factor α. Results In subjects with active disease, the Aix, PWV, and level of CRP were elevated compared with that in controls (mean ± SEM 31 ± 3% versus 22 ± 2% [P = 0.003], 9.2 ± 0.7 versus 7.5 ± 0.3 meters/second [P = 0.03], and 16.0 ± 4.0 versus 1.1 ± 0.1 mg/liter [P < 0.001], respectively). However, PWV and the Aix were not significantly different between patients with disease in remission and controls (8.0 ± 0.5 versus 7.5 ± 0.3 meters/second and 19 ± 3% versus 22 ± 2%, respectively). The CRP level was positively correlated with both PWV and the Aix. Multiple regression analysis indicated that age, mean arterial pressure (MAP), and CRP were independently related to PWV, and that age, MAP, CRP, sex, and heart rate were associated with the Aix. Conclusion These data indicate that AASV is associated with increased arterial stiffness, and that stiffness correlates with the degree of active inflammation.
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the influence of heart rate on augmentation index and central arterial pressure in humans
The Journal of Physiology, 2000Co-Authors: Ian B Wilkinson, Helen Maccallum, Laura Flint, J R Cockcroft, David E Newby, David J WebbAbstract:Arterial stiffness is an important determinant of cardiovascular risk. Augmentation index (Aix) is a measure of systemic arterial stiffness derived from the ascending aortic pressure waveform. The aim of the present study was to assess the effect of heart rate on Aix. We elected to use cardiac pacing rather than chronotropic drugs to minimize confounding effects on the systemic circulation and myocardial contractility. Twenty-two subjects (13 male) with a mean age of 63 years and permanent cardiac pacemakers in situ were studied. Pulse wave analysis was used to determine central arterial pressure waveforms, non-invasively, during incremental pacing (from 60 to 110 beats min−1), from which Aix and central blood pressure were calculated. Peripheral blood pressure was recorded non-invasively from the brachial artery. There was a significant, inverse, linear relationship between Aix and heart rate (r =−0.76; P < 0.001). For a 10 beats min−1 increment, Aix fell by around 4 %. Ejection duration and heart rate were also inversely related (r =−0.51; P < 0.001). Peripheral systolic, diastolic and mean arterial pressure increased significantly during incremental pacing. Although central diastolic pressure increased significantly with pacing, central systolic pressure did not. There was a significant increase in the ratio of peripheral to central pulse pressure (P < 0.001), which was accounted for by the observed change in central pressure augmentation. These results demonstrate an inverse, linear relationship between Aix and heart rate. This is likely to be due to alterations in the timing of the reflected pressure wave, produced by changes in the absolute duration of systole. Consideration of wave reflection and aortic pressure augmentation may explain the lack of rise in central systolic pressure during incremental pacing despite an increase in peripheral pressure.
Kevin S. Heffernan - One of the best experts on this subject based on the ideXlab platform.
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peripheral augmentation index as a biomarker of vascular aging an invasive hemodynamics approach
European Journal of Applied Physiology, 2012Co-Authors: Kevin S. Heffernan, Richard H. Karas, Eshan A Patvardhan, Navin K Kapur, Jeffrey T. KuvinAbstract:We compared two measures of vascular function obtained from digital volume waveforms with measures of target organ damage and novel invasive measures of vascular function as they relate to vascular aging. Aortic pulse pressure amplification, pulsatility, form factor and extent of coronary atherosclerosis (modified Gensini score) were obtained invasively in 59 patients undergoing left heart catheterization. Digital volume waveforms were captured via peripheral arterial tone (PAT) and used to derive augmentation index (Aix) and the pulse wave amplitude-reactive hyperemia index (PWA-RHI). Aix was associated with age (r = 0.50, p < 0.05) and aortic pulsatility (r = 0.45, p < 0.05) and inversely associated with estimated glomerular filtration rate (−0.29, p < 0.05) aortic pulse pressure amplification (r = −0.28, p < 0.05) and aortic form factor (r = −0.38, p < 0.05). Aix was slightly higher in patients with left ventricular hypertrophy (LVH) versus those without left ventricular hypertrophy (30 vs. 14%, p = 0.058). There was no association between Aix and Gensini score. PWA-RHI was not associated with age, estimated glomerular filtration rate or invasive vascular parameters and did not differ in patients with versus without LVH (p = ns). PWA-RHI was inversely associated with Gensini score (r = −0.32, p < 0.05). Aix derived from PAT is correlated with age-associated changes in vascular function and target organ damage but not coronary atherosclerotic burden. PWA-RHI is associated with coronary atherosclerotic burden but is not associated with target organ damage or other measures of vascular aging assessed in this study. Each parameter provides distinct insight into systemic vascular aging and target organ damage.
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peripheral augmentation index and vascular inflammation in autosomal dominant polycystic kidney disease
Nephrology Dialysis Transplantation, 2011Co-Authors: Kevin S. Heffernan, Priya Chandra, Darya Rudym, Dana C Miskulin, Jeffrey T. Kuvin, Richard H. Karas, Mark J Sarnak, Ronald D Perrone, Vandana MenonAbstract:Background. Cardiovascular disease is the leading cause of premature mortality in autosomal dominant polycystic kidney disease (ADPKD). We examined peripheral augmentation index (Aix) as a measure of systemic vascular function and circulating markers of vascular inflammation in patients with ADPKD. Methods. Fifty-two ADPKD patients with hypertension and estimated glomerular filtration rate (eGFR) 0.05). ICAM, P-selectin, E-selectin and sFas were higher and FasL lower in all ADPKD groups compared to controls (P 0.05). According to multiple regression analysis, predictors of Aix in ADPKD included age, height, heart rate and mean arterial pressure (P < 0.05). Vascular inflammatory markers were not predictors of Aix in ADPKD. Conclusions. Systemic vascular dysfunction, manifesting as an increase in Aix and vascular inflammation is evident in young normotensive ADPKD patients with preserved renal function. Vascular inflammation is not associated with elevated Aix in ADPKD.
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augmentation index derived from peripheral arterial tonometry correlates with cardiovascular risk factors
Cardiology Research and Practice, 2011Co-Authors: Eshan A Patvardhan, Kevin S. Heffernan, Richard H. Karas, Jenny Ruan, Michael Hession, Patrick J Warner, Jeffrey T. KuvinAbstract:Background. Augmentation index (Aix) is traditionally obtained from pressure waveforms via arterial applanation tonometry. We sought to evaluate the association between Aix obtained from peripheral arterial tonometry (PAT) with cardiovascular risk factors (CRF) and coronary artery disease (CAD). Methods. 186 patients were enrolled in the study. The presence or absence of CRFs and CAD was assessed in each subject. Aix was calculated by an automated algorithm averaging pulse wave amplitude data obtained via PAT. Central blood pressures were assessed in a subset of patients undergoing clinically indicated cardiac catheterization. Results. An association was observed between Aix and age, heart rate, systolic blood pressure, mean arterial pressure, pulse pressure, body weight and body mass index. Aix was significantly lower in patients with 5 CRFs ( P = .02). CAD+ patients had significantly higher Aix compared to CAD− patients ( P = .008). Area under the ROC curve was 0.604 (P < .01). In patients undergoing cardiac catheterization, after adjusting for age, height and heart rate, Aix was a significant predictor of aortic systolic and pulse pressures (P < .05) Conclusion. Aix derived from PAT correlates with cardiac risk factors and CAD. It may be a useful measure of assessing overall risk for coronary artery disease.
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elevated augmentation index derived from peripheral arterial tonometry is associated with abnormal ventricular vascular coupling
Clinical Physiology and Functional Imaging, 2010Co-Authors: Kevin S. Heffernan, Richard H. Karas, Eshan A Patvardhan, Jenny Ruan, Michael Hession, Jeffrey T. KuvinAbstract:As a measure of late systolic load and systemic vascular function (Borlaug, et al. 2007) the augmentation index (Aix) may be a useful therapeutic target and secondary endpoint (Hashimoto, et al. 2007). Aix is associated with numerous cardiovascular morbidities (Nurnberger, et al. 2002), coronary artery disease (Hayashi, et al. 2002; Weber, et al. 2004), albuminuria (Tsioufis, et al. 2003), and predicts future cardiovascular events (Weber, et al. 2005) and mortality (London, et al. 2001). Moreover, the augmentation of systolic blood pressure owing to wave reflections (i.e. increased late systolic load) reduces left ventricular (LV) systolic and diastolic function (Borlaug, Melenovsky, Redfield, Kessler, Chang, Abraham & Kass 2007), increases LV pressure effort, increases myocardial oxygen demand and reduces coronary perfusion (Hashimoto, Imai & O'Rourke 2007; Hashimoto, et al. 2007; Hashimoto, et al. 2008). This resultant ventricular-vascular mismatch impairs cardiac metabolic efficiency and causes LV hypertrophy (Hashimoto, Nichols, O'Rourke & Imai 2008). Although typically derived from the contour of central and peripheral arterial pressure waveforms (Chen, et al. 1997), Aix can also be derived from digital pulse volume waveforms using finger plethysmography (peripheral arterial tonometry, PAT). Little is known regarding the systemic vascular correlates of Aix derived from PAT. The digital pulse volume waveform is influenced by wave reflections (Chowienczyk, et al. 1999) and correlates with pressure waveforms measured at the finger, radial artery and carotid artery, and changes in the digital volume pulse with perturbation have been shown to be very similar to changes in the pressure waveforms (Millasseau, et al. 2000; Millasseau, et al. 2003). Thus, it is reasonable to speculate that digital Aix derived from PAT may also serve as a proxy of ventricular-vascular load but this has yet to be empirically demonstrated. Ventricular-vascular coupling can be quantified via examination of the ratio of effective arterial elastance and LV end-systolic elastance derived either invasively from catheterization-derived pressure-volume loops or non-invasively from conventional blood pressure measurement and echocardiography (Chen, et al. 2001). Ventricular-vascular uncoupling is associated with low exercise capacity (Chen, et al. 1999; Wong, et al.), has been implicated in the etiology of numerous pathologies (Kass 2005) and has also recently been shown to be associated with B-type natriuretic peptide (BNP) in patients after myocardial infarction and predicts long-term CV mortality in this setting (Antonini-Canterin, et al. 2009). The purpose of this study was to examine the association between PAT-Aix and ventricular-vascular coupling. We hypothesized that elevated PAT-Aix would reflect abnormal ventricular-vascular coupling.
Tadashi Kimura - One of the best experts on this subject based on the ideXlab platform.
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abnormal pressure wave reflection in pregnant women with chronic hypertension association with maternal and fetal outcomes
Hypertension Research, 2014Co-Authors: Takuji Tomimatsu, Mika Fujime, Shinsuke Koyama, Takeshi Kanagawa, Tomoko Kanayama, Kazuya Mimura, Masayuki Endo, Koichiro Shimoya, Tadashi KimuraAbstract:The current study tested the hypothesis that abnormal pressure-wave reflection may have an important role in identifying pregnant women with chronic hypertension who might develop pre-eclampsia (PE) and/or fetal growth restriction. Pulse-wave analyses were performed to assess maternal arterial stiffness during 26-32 weeks of gestation in 41 women with chronic hypertension. We measured the central systolic pressure (CSP) and augmentation index (Aix) noninvasively using pulse waveforms of the radial artery with an automated applanation tonometric system. In a multiple regression analysis that included Aix-75 (Aix at a heart rate of 75 beats per minute), brachial systolic pressure, maternal height, smoking status, gestational age at testing and the presence of antihypertensive treatment at testing as independent determinants, Aix-75 was the only significant determinant of birth weight, whereas the brachial systolic pressure was not. In pregnant women with chronic hypertension who subsequently developed both superimposed PE and fetal growth restriction, CSP, Aix, Aix-75, and the brachial systolic and pulse pressures were all significantly higher than those who did not develop superimposed PE nor small for gestational age. In contrast, Aix-75 was the only significantly elevated hemodynamic parameter in patients who developed fetal growth restriction but not superimposed PE. In addition, CSP was the only significantly elevated hemodynamic parameter in patients who developed superimposed PE but not fetal growth restriction. Abnormal pressure-wave reflection during 26-32 weeks of gestation showed a stronger correlation with birth weight than conventional brachial blood pressure. Our findings might provide new insight into the pathophysiology of fetal growth restriction as well as superimposed PE in pregnancies complicated with chronic hypertension.
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central aortic blood pressure and augmentation index during normal pregnancy
Hypertension Research, 2012Co-Authors: Mika Fujime, Takuji Tomimatsu, Yuko Okaue, Shinsuke Koyama, Takeshi Kanagawa, Takeshi Taniguchi, Tadashi KimuraAbstract:The current study tested the hypothesis that pregnancy-related changes are more pronounced in central hemodynamics, and both central aortic systolic blood pressure (cSBP) and augmentation index (Aix) are independent from brachial systolic blood pressure (bSBP) in normal pregnant subjects. In 830 healthy pregnant women from 12 to 36 weeks gestation, we measured cSBP and Aix-75 (Aix at heart rate of 75 beats per minute) non-invasively by pulse waveforms of the radial artery using an automated applanation tonometric system. In 69 pregnant women, we recorded these data longitudinally. cSBP and Aix-75 significantly declined during pregnancy, reaching its nadir in mid-pregnancy and rising towards term. Pregnancy-related changes were more pronounced in Aix-75 compared with cSBP, but less evident in bSBP. Aix-75, but not cSBP, was independent from bSBP throughout pregnancy. cSBP and Aix-75, but not bSBP, were significantly increased in healthy pregnant women older than 35 years. This study established normal values for pulse wave analysis parameters throughout pregnancy, and indicated that pulse wave analysis might offer additional and independent information about maternal arterial compliance to conventional brachial blood pressure measurements. These data may be used as the basis for further investigation into the role of pulse wave analysis in the assessment, management and prediction of disorders, which might interfere with pregnancy-related cardiovascular adaptations.
J R Cockcroft - One of the best experts on this subject based on the ideXlab platform.
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normal vascular aging differential effects on wave reflection and aortic pulse wave velocity the anglo cardiff collaborative trial acct
Journal of the American College of Cardiology, 2005Co-Authors: Carmel M Mceniery, Ian B Wilkinson, Ahmad Qasem, Ian R Hall, J R CockcroftAbstract:OBJECTIVES The aim of the current investigation was to test the hypothesis that age-related changes in augmentation index (Aix) are more prominent in younger individuals (50 years), whereas changes in aortic stiffness per se are more marked in older individuals (50 years). BACKGROUND Aging exerts a number of deleterious changes in the cardiovascular system, and, in particular, on the large arteries. Previous studies have suggested that Aix and pulse wave velocity (PWV) increase linearly with age, yet epidemiological data concerning pulse pressure suggest that large artery stiffening predominantly occurs later in life. METHODS Peripheral and central blood pressure, augmentation pressure (AP), and Aix were determined in 4,001 healthy, normotensive individuals, aged 18 to 90 years. Aortic and brachial PWV were also determined in a subset of 998 subjects. RESULTS Peripheral and central pulse pressure, AP, Aix, and aortic and brachial PWV all increased significantly with age; however, the age-related changes in Aix and aortic PWV were non-linear, with Aix increasing more in younger individuals, whereas the changes in PWV were more prominent in older individuals. CONCLUSIONS These data suggest that Aix might be a more sensitive marker of arterial stiffening and risk in younger individuals but aortic PWV is likely to be a better measure in older individuals. (J Am Coll Cardiol 2005;46:1753‐60) © 2005 by the American College of Cardiology Foundation Age is one of the most powerful determinants of cardiovascular risk and is associated with a number of deleterious changes in the cardiovascular system (1). Among the more prominent changes are stiffening and dilatation of the large arteries—arteriosclerosis—which has been documented in almost all societies worldwide. Such changes lead to a rise in pulse pressure (PP) and, ultimately, the development of isolated systolic hypertension. This condition affects approximately 50% of individuals over 60 years of age and is associated with considerable excess morbidity and mortality. The importance of large artery stiffening has been further highlighted by the observation that aortic pulse wave velocity (PWV), which is inversely related to distensibility (2), and central augmentation index (Aix), a composite measure that depends on the site and degree of wave reflection (3), are independent predictors of cardiovascular and total mortality in selected patient groups (4‐8). A number of studies have investigated the effects of age on aortic PWV and Aix (9‐12). Most suggest a linear, age-related increase in both indexes across a variety of different populations; however, epidemiological data indicate that PP increases significantly only after the fifth decade, suggesting that stiffening of the large arteries occurs predominantly in later life (13). Moreover, data from invasive studies suggest that the intensity of wave reflection becomes less marked in old age as impedance mismatch reduces (14). Such apparent discrepancies might reflect the fact that the majority of hemodynamic studies have been modest in size and encompassed a relatively narrow age range. Moreover, existing studies have not investigated the interaction between age, large artery stiffness, wave reflection, and PP within a single population. We hypothesized that age-related changes in Aix are more prominent in younger subjects, whereas changes in large artery stiffness per se are more marked in older subjects. The aim of the present study was to test this hypothesis in a large cohort of healthy individuals from the Anglo-Cardiff Collaborative Trial (ACCT) and, in doing so, expand our understanding of the effect of age and gender on these commonly measured parameters of arterial stiffness.
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the influence of heart rate on augmentation index and central arterial pressure in humans
The Journal of Physiology, 2000Co-Authors: Ian B Wilkinson, Helen Maccallum, Laura Flint, J R Cockcroft, David E Newby, David J WebbAbstract:Arterial stiffness is an important determinant of cardiovascular risk. Augmentation index (Aix) is a measure of systemic arterial stiffness derived from the ascending aortic pressure waveform. The aim of the present study was to assess the effect of heart rate on Aix. We elected to use cardiac pacing rather than chronotropic drugs to minimize confounding effects on the systemic circulation and myocardial contractility. Twenty-two subjects (13 male) with a mean age of 63 years and permanent cardiac pacemakers in situ were studied. Pulse wave analysis was used to determine central arterial pressure waveforms, non-invasively, during incremental pacing (from 60 to 110 beats min−1), from which Aix and central blood pressure were calculated. Peripheral blood pressure was recorded non-invasively from the brachial artery. There was a significant, inverse, linear relationship between Aix and heart rate (r =−0.76; P < 0.001). For a 10 beats min−1 increment, Aix fell by around 4 %. Ejection duration and heart rate were also inversely related (r =−0.51; P < 0.001). Peripheral systolic, diastolic and mean arterial pressure increased significantly during incremental pacing. Although central diastolic pressure increased significantly with pacing, central systolic pressure did not. There was a significant increase in the ratio of peripheral to central pulse pressure (P < 0.001), which was accounted for by the observed change in central pressure augmentation. These results demonstrate an inverse, linear relationship between Aix and heart rate. This is likely to be due to alterations in the timing of the reflected pressure wave, produced by changes in the absolute duration of systole. Consideration of wave reflection and aortic pressure augmentation may explain the lack of rise in central systolic pressure during incremental pacing despite an increase in peripheral pressure.