The Association Between Viscosity and Cardiovascular Risk may Reflect the Central Systolic Stress Response to Light Activity: An Exercise Haemodynamic Study

Abstract

nIncreased blood viscosity is associated with early atherogenesis and increased cardiovascular (CV) risk. Whilst the mechanism of these associations is unclear, it may be related to increased arterial wave reflection during activities of daily living. This study aimed to test this hypothesis.Methods: Twenty patients (14 males; aged 61 p 12 years) with polycythaemia rubra vera (n = 16) or haemachromatosis (n = 4) were studied at rest and during cycle exercise at 50% of maximal heart rate, before and after venesection (500 ml, volume replaced with saline) to elicit an acute decrease in plasma viscosity at stable blood pressure (BP). Radial tonometry was used to derive central BP and augmentation index (AIx) as a marker of arterial wave reflection. Healthy controls (n = 20) underwent the same protocol without venesection.Results:Venesection caused a significant decrease in plasma viscosity (1.46 p 0.10n1.41 p 0.11), protein and haemoglobin (p l 0.05 for all) in the patient group, but these parameters did not significantly change in the controls (p g 0.50 for all). Exercise AIx was significantly reduced in response to venesection (from 31 p 11n25 p 10%; p l 0.001), despite lack of significant change in mean arterial pressure, central or peripheral BP (p g 0.05 for all). Haemodynamics were not significantly changed in controls.Conclusions:Acute reduction in plasma viscosity lowers arterial wave reflection during light activity. Thus, the increased CV risk associated with viscosity may be related to central hypertension during daily activities.