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      Global REACH 2018 : High Blood Viscosity and Hemoglobin Concentration Contribute to Reduced Flow-Mediated Dilation in High-Altitude Excessive Erythrocytosis

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          Abstract

          <p class="first" id="d5719991e221">Excessive erythrocytosis (EE; hemoglobin concentration [Hb] ≥21 g/dL in adult males) is associated with increased cardiovascular risk in highlander Andeans. We sought to quantify shear stress and assess endothelial function via flow-mediated dilation (FMD) in male Andeans with and without EE. We hypothesized that FMD would be impaired in Andeans with EE after accounting for shear stress and that FMD would improve after isovolemic hemodilution. Brachial artery shear stress and FMD were assessed in 23 male Andeans without EE (age: 40±15 years [mean±SD]; Hb&lt;21 g/dL) and 19 male Andeans with EE (age: 43±14 years; Hb≥21 g/dL) in Cerro de Pasco, Peru (4330 m). Shear stress was quantified from Duplex ultrasound measures of shear rate and blood viscosity. In a subset of participants (n=8), FMD was performed before and after isovolemic hemodilution with blood volume replaced by an equal volume of human serum albumin. Blood viscosity and Hb were 48% and 23% higher (both P&lt;0.001) and FMD was 28% lower after adjusting for the shear stress stimulus ( P=0.013) in Andeans with EE compared to those without. FMD was inversely correlated with blood viscosity ( r2=0.303; P&lt;0.001) and Hb ( r2=0.230; P=0.001). Isovolemic hemodilution decreased blood viscosity by 30±10% and Hb by 14±5% (both P&lt;0.001) and improved shear stress stimulus-adjusted FMD from 2.7±1.9% to 4.3±1.9% ( P=0.022). Hyperviscosity, high Hb, or both, actively contribute to acutely reversible impairments in FMD in EE, suggesting that this plays a pathogenic role in the increased cardiovascular risk. </p>

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          Most cited references58

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          Ultrasound assessment of flow-mediated dilation.

          Developed in 1992, the flow-mediated dilation test is now the most commonly used noninvasive assessment of vascular endothelial function in humans. Since its inception, scientists have refined their understanding of the physiology, analysis, and interpretation of this measurement. Recently, a significant growth of knowledge has added to our understanding and implementation of this clinically relevant research methodology. Therefore, this tutorial provides timely insight into recent advances and practical information related to the ultrasonic assessment of vascular endothelial function in humans.
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            Consensus statement on chronic and subacute high altitude diseases.

            This is an international consensus statement of an ad hoc committee formed by the International Society for Mountain Medicine (ISMM) at the VI World Congress on Mountain Medicine and High Altitude Physiology (Xining, China; 2004) and represents the committee's interpretation of the current knowledge with regard to the most common chronic and subacute high altitude diseases. It has been developed by medical and scientific authorities from the committee experienced in the recognition and prevention of high altitude diseases and is based mainly on published, peer-reviewed articles. It is intended to include all legitimate criteria for choosing to use a specific method or procedure to diagnose or manage high altitude diseases. However, the ISMM recognizes that specific patient care decisions depend on the different geographic circumstances involved in the development of each chronic high altitude disease. These guidelines are established to inform the medical services on site who are directed to solve high altitude health problems about the definition, diagnosis, treatment, and prevention of the most common chronic high altitude diseases. The health problems associated with life at high altitude are well documented, but health policies and procedures often do not reflect current state-of-the-art knowledge. Most of the cases of high altitude diseases are preventable if on-site personnel identify the condition and implement appropriate care.
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              The heart and pulmonary circulation at high altitudes: healthy highlanders and chronic mountain sickness.

              More than 140 million people worldwide live >2500 m above sea level. Of them, 80 million live in Asia, and 35 million live in the Andean mountains. This latter region has its major population density living above 3500 m. The primary objective of the present study is to review the physiology, pathology, pathogenesis, and clinical features of the heart and pulmonary circulation in healthy highlanders and patients with chronic mountain sickness. A systematic review of worldwide literature was undertaken, beginning with the pioneering work done in the Andes several decades ago. Original articles were analyzed in most cases and English abstracts or translations of articles written in Chinese were reviewed. Pulmonary hypertension in healthy highlanders is related to a delayed postnatal remodeling of the distal pulmonary arterial branches. The magnitude of pulmonary hypertension increases with the altitude level and the degree of exercise. There is reversal of pulmonary hypertension after prolonged residence at sea level. Chronic mountain sickness develops when the capacity for altitude adaptation is lost. These patients have moderate to severe pulmonary hypertension with accentuated hypoxemia and exaggerated polycythemia. The clinical picture of chronic mountain sickness differs from subacute mountain sickness and resembles other chronic altitude diseases described in China and Kyrgyzstan. The heart and pulmonary circulation in healthy highlanders have distinct features in comparison with residents at sea level. Chronic mountain sickness is a public health problem in the Andean mountains and other mountainous regions around the world. Therefore, dissemination of preventive and therapeutic measures is essential.
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                Author and article information

                Journal
                Hypertension
                Hypertension
                Ovid Technologies (Wolters Kluwer Health)
                0194-911X
                1524-4563
                June 2019
                June 2019
                : 73
                : 6
                : 1327-1335
                Affiliations
                [1 ]From the Cardiovascular Stress Response Laboratory, School of Kinesiology and Health Studies, Queen’s University, Kingston, ON, Canada (J.C.T., K.E.P.)
                [2 ]Centre for Heart, Lung &amp; Vascular Health, Faculty of Health and Social Development, University of British Columbia—Okanagan, Kelowna, Canada (R.L.H., C.A.H., G.B.C., M.M.T., P.N.A.)
                [3 ]Laboratorio de Fisiología Comparada, Departamento de Ciencias Biológicas y Fisiológicas, Facultad de Ciencias y Filosofía, Universidad Peruana Cayetano Heredia, Lima, Perú (G.A.V.-G., R.J.F.-M., D.B., F.C.V.)
                [4 ]School of Physical Education, Sport and Exercise Sciences, Division of Sciences, University of Otago, Dunedin, New Zealand (T.D.G.)
                [5 ]Neurovascular Research Laboratory, Faculty of Life Sciences and Education, University of South Wales, United Kingdom (B.S.S., D.M.B.)
                [6 ]Human Pharmacology and Physiology Laboratory, Department of Anesthesiology, Duke University Medical Center, Durham, NC (D.B.M.)
                [7 ]Division of Pulmonary, Critical Care, Hyperbaric and Sleep Medicine, Loma Linda University School of Medicine, CA (C.G.).
                Article
                10.1161/HYPERTENSIONAHA.119.12780
                31006327
                ee290f38-a612-4952-92b4-3cd41b161d9f
                © 2019
                History

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