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Effects of Changing Blood Viscosity and Heart Rate on Vena Contracta Width as Evaluated by Color Doppler Flow Mapping. An In Vitro Study with a Pulsatile Flow Model
Author(s) -
Schmidt André,
Da Silva Júnior Telêmaco,
PazinFilho Antônio,
Otávio Murta Júnior Luiz,
César AlmeidaFilho Oswaldo,
GalloJúnior Lourenço,
Antonio MarinNeto José,
Carlos Maciel Benedito
Publication year - 2008
Publication title -
echocardiography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.404
H-Index - 62
eISSN - 1540-8175
pISSN - 0742-2822
DOI - 10.1111/j.1540-8175.2007.00561.x
Subject(s) - vena contracta , pulsatile flow , hematocrit , blood viscosity , viscosity , blood flow , biomedical engineering , cardiology , materials science , medicine , mechanics , chemistry , physics , regurgitation (circulation) , composite material
Background: There is only limited knowledge on how the quantification of valvular regurgitation by color Doppler is affected by changing blood viscosity. This study was designed to evaluate the effect of changing blood viscosity on the vena contracta width using an in vitro model of valvular insufficiency capable of providing ample variation in the rate and stroke volume. Methods: We constructed a pulsatile flow model filled with human blood at varying hematocrit (15%, 35%, and 55%) and corresponding blood viscosity (blood/water viscosity: 2.6, 4.8, 9.1) levels in which jets were driven through a known orifice (7 mm 2 ) into a 110 mL compliant receiving chamber (compliance: 2.2 mL/mmHg) by a pulsatile pump. In addition, we used variable pump stroke volumes (5, 7.5, and 10 mL) and rates (40, 60, and 80 ppm). Vena contracta region was imaged using a 3.5 MHz transducer. Pressure and volume in the flow model were kept constant during each experimental condition, as well as ultrasound settings. Results: Blood viscosity variation in the experimental range did not induce significant changes in vena contracta dimensions. Also, vena contracta width did not change from normal to low hematocrit and viscosity levels. A very modest increase only in vena contracta dimension was observed at very high level of blood viscosity when hematocrit was set to 55% . Pump rate, in the evaluated range, did not influence vena contracta width. These results in controlled experimental settings suggest that the vena contracta is an accurate quantitative method for quantifying valvular regurgitation even when this condition is associated with anemia, a frequent finding in patients with valvular heart disease.