Structural Correlates of Platelet Functional Damage by Physical Forces

Spatio-temporal Flow Analysis in Bileaflet Heart Valve Hinge Regions: Potential Analysis for Blood Element Damage

“…A comparison of the SJM and CM results highlighted the presence of lower RSS levels in the SJM hinge design. Based on previous studies of fluid mechanical effects on blood cells, 1,4,8,9,13,14,16,22,23,25,30,31,[34][35][36][37] these results point out that the SJM hinge may have a lower potential for hemolysis and platelet activation than the CM hinge design. However, it should be noted that this inference is only based on the RSS levels in the bulk of the flow (which, as shown later, are in fact below the reported thresholds for blood cell damage).…”

“…The temporal averaging of the spatially averaged velocity and RSS, along with the estimation of the exposure times as the hinge transit times, enables the comparison of the averaged loading on the blood elements crossing the hinge region with previously published blood damage shear stress thresholds. [1][2][3][4][5][6][7][8][9]12,[16][17][18][21][22][23][24][25][28][29][30][31][32][33][34][35]37 We first analyze the spatially averaged dynamics focusing on the influence of implant location and hinge design. We then discuss the results with respect to previously published models of blood damage based on stress and exposure time, together with rough estimates of viscous stress levels.…”

“…Figure 9 shows the RSS levels and estimated viscous stresses as a function of the transit time for each characteristic region for both leakage and forward flow phases. Also included are previously reported threshold levels for platelet activation 1,3,4,8,9,28,29,35 and hemolysis. 2,[5][6][7]12,[16][17][18][21][22][23][24][25][30][31][32][33][34]37 Figure 9 clearly indicates that the estimates of RSS and viscous stress levels along with their estimated exposure times are mostly below the established threshold levels.…”

“…8 In 1977 Bernstein demonstrated that high shear forces (10 6 dyn/cm 2 ) applied for a few milliseconds within the bulk flow affected both the platelet structure and function. 4 In another study, Anderson et al estimated the threshold for platelet activation at 150 dyn/cm 2 and showed that for platelet damage threshold shear stress increased with decreasing exposure time. 1 Anderson also underlined the fact that laminar and turbulent flows might not have the same impact on platelet damage.…”

“…Previous studies have emphasized the importance of stress magnitude, stress exposure history, and exposure time as main parameters in assessing shear related blood cell damage. 1,4,8,14,16,22,23,25,30,31,34,35,37 Clearly, existing published hinge data need to be revisited and discussed by taking into account realistic exposure times at representative shear stress levels. In this paper we present the basic analysis tools necessary to address the thromboembolic potential of the hinge region, a Lagrangian measure, from the Eulerian point-wise measurements published in our previous papers.…”