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      Central Hemodynamics for Management of Arteriosclerotic Diseases

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          Abstract

          Arteriosclerosis, particularly aortosclerosis, is the most critical risk factor associated with cardiovascular, cerebrovascular, and renal diseases. The pulsatile hemodynamics in the central aorta consists of blood pressure, flow, and stiffness and substantially differs from the peripheral hemodynamics in muscular arteries. Arteriosclerotic changes with age appear earlier in the elastic aorta, and age-dependent increases in central pulse pressure are more marked than those apparent from brachial pressure measurement. Central pressure can be affected by lifestyle habits, metabolic disorders, and endocrine and inflammatory diseases in a manner different from brachial pressure. Central pulse pressure widening due to aortic stiffening increases left ventricular afterload in systole and reduces coronary artery flow in diastole, predisposing aortosclerotic patients to myocardial hypertrophy and ischemia. The widened pulse pressure is also transmitted deep into low-impedance organs such as the brain and kidney, causing microvascular damage responsible for lacunar stroke and albuminuria. In addition, aortic stiffening increases aortic blood flow reversal, which can lead to retrograde embolic stroke and renal function deterioration. Central pressure has been shown to predict cardiovascular events in most previous studies and potentially serves as a surrogate marker for intervention. Quantitative and comprehensive evaluation of central hemodynamics is now available through various noninvasive pressure/flow measurement modalities. This review will focus on the clinical usefulness and mechanistic rationale of central hemodynamic measurements for cardiovascular risk management.

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          Most cited references121

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          2007 Guidelines for the management of arterial hypertension: The Task Force for the Management of Arterial Hypertension of the European Society of Hypertension (ESH) and of the European Society of Cardiology (ESC).

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            Arterial stiffness, pressure and flow pulsatility and brain structure and function: the Age, Gene/Environment Susceptibility--Reykjavik study.

            Aortic stiffness increases with age and vascular risk factor exposure and is associated with increased risk for structural and functional abnormalities in the brain. High ambient flow and low impedance are thought to sensitize the cerebral microcirculation to harmful effects of excessive pressure and flow pulsatility. However, haemodynamic mechanisms contributing to structural brain lesions and cognitive impairment in the presence of high aortic stiffness remain unclear. We hypothesized that disproportionate stiffening of the proximal aorta as compared with the carotid arteries reduces wave reflection at this important interface and thereby facilitates transmission of excessive pulsatile energy into the cerebral microcirculation, leading to microvascular damage and impaired function. To assess this hypothesis, we evaluated carotid pressure and flow, carotid-femoral pulse wave velocity, brain magnetic resonance images and cognitive scores in participants in the community-based Age, Gene/Environment Susceptibility--Reykjavik study who had no history of stroke, transient ischaemic attack or dementia (n = 668, 378 females, 69-93 years of age). Aortic characteristic impedance was assessed in a random subset (n = 422) and the reflection coefficient at the aorta-carotid interface was computed. Carotid flow pulsatility index was negatively related to the aorta-carotid reflection coefficient (R = -0.66, P<0.001). Carotid pulse pressure, pulsatility index and carotid-femoral pulse wave velocity were each associated with increased risk for silent subcortical infarcts (hazard ratios of 1.62-1.71 per standard deviation, P<0.002). Carotid-femoral pulse wave velocity was associated with higher white matter hyperintensity volume (0.108 ± 0.045 SD/SD, P = 0.018). Pulsatility index was associated with lower whole brain (-0.127 ± 0.037 SD/SD, P<0.001), grey matter (-0.079 ± 0.038 SD/SD, P = 0.038) and white matter (-0.128 ± 0.039 SD/SD, P<0.001) volumes. Carotid-femoral pulse wave velocity (-0.095 ± 0.043 SD/SD, P = 0.028) and carotid pulse pressure (-0.114 ± 0.045 SD/SD, P = 0.013) were associated with lower memory scores. Pulsatility index was associated with lower memory scores (-0.165 ± 0.039 SD/SD, P<0.001), slower processing speed (-0.118 ± 0.033 SD/SD, P<0.001) and worse performance on tests assessing executive function (-0.155 ± 0.041 SD/SD, P<0.001). When magnetic resonance imaging measures (grey and white matter volumes, white matter hyperintensity volumes and prevalent subcortical infarcts) were included in cognitive models, haemodynamic associations were attenuated or no longer significant, consistent with the hypothesis that increased aortic stiffness and excessive flow pulsatility damage the microcirculation, leading to quantifiable tissue damage and reduced cognitive performance. Marked stiffening of the aorta is associated with reduced wave reflection at the interface between carotid and aorta, transmission of excessive flow pulsatility into the brain, microvascular structural brain damage and lower scores in various cognitive domains.
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              Mechanical factors in arterial aging: a clinical perspective.

              The human arterial system in youth is beautifully designed for its role of receiving spurts of blood from the left ventricle and distributing this as steady flow through peripheral capillaries. Central to such design is "tuning" of the heart to arterial tree; this minimizes aortic pressure fluctuations and confines flow pulsations to the larger arteries. With aging, repetitive pulsations (some 30 million/year) cause fatigue and fracture of elastin lamellae of central arteries, causing them to stiffen (and dilate), so that reflections return earlier to the heart; in consequence, aortic systolic pressure rises, diastolic pressure falls, and pulsations of flow extend further into smaller vessels of vasodilated organs (notably the brain and kidney). Stiffening leads to increased left ventricular (LV) load with hypertrophy, decreased capacity for myocardial perfusion, and increased stresses on small arterial vessels, particularly of brain and kidney. Clinical manifestations are a result of diastolic LV dysfunction with dyspnea, predisposition to angina, and heart failure, and small vessel degeneration in brain and kidney with intellectual deterioration and renal failure. While aortic stiffening is the principal cause of cardiovascular disease with age in persons who escape atherosclerotic complications, it is not a specific target for therapy. The principal target is the smooth muscle in distributing arteries, whose relaxation has little effect on peripheral resistance but causes substantial reduction in the magnitude of wave reflection. Such relaxation is achieved through regular exercise and with the vasodilating drugs that are used in modern treatment of hypertension and cardiac failure.
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                Author and article information

                Journal
                J Atheroscler Thromb
                J. Atheroscler. Thromb
                jat
                jat
                Journal of Atherosclerosis and Thrombosis
                Japan Atherosclerosis Society
                1340-3478
                1880-3873
                1 August 2017
                : 24
                : 8
                : 765-778
                Affiliations
                Medical Center, Miyagi University of Education, Sendai, Japan
                Author notes
                Address for correspondence: Junichiro Hashimoto, Medical Center, Miyagi University of Education, 149 Aoba, Aramaki, Aoba-ku, Sendai 980-0845, Japan E-mail: hashimoto@ 123456med.tohoku.ac.jp
                Article
                10.5551/jat.40717
                5556183
                28603219
                ba508303-245b-4bd1-80f6-04dd842de0d7
                2017 Japan Atherosclerosis Society

                This article is distributed under the terms of the latest version of CC BY-NC-SA defined by the Creative Commons Attribution License. http://creativecommons.org/licenses/by-nc-sa/3.0/

                History
                : 30 March 2017
                : 24 April 2017
                Page count
                Figures: 3, Tables: 3, References: 156, Pages: 14
                Categories
                Review

                arteriosclerosis,aorta,stiffness,blood pressure,blood flow
                arteriosclerosis, aorta, stiffness, blood pressure, blood flow

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