Computational results of laminar incompressible blood-particle flow analyses in an axisymmetric artery segment with a smooth local area constriction of 75 percent have been presented. The flow input waveform was sinus...
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Computational results of laminar incompressible blood-particle flow analyses in an axisymmetric artery segment with a smooth local area constriction of 75 percent have been presented. The flow input waveform was sinusoidal with a nonzero average. The non-Newtonian behavior of blood was simulated with a modified Quemada model, platelet concentrations were calculated with a drift-flux model, and monocyte trajectories were described and compared for both Newtonian and Quemada rheologies. Indicators of ''disturbed flow'' included the time-averaged wall shear stress (WSS), the oscillatory shear index (OSI), and the wall shear stress gradient (WSSG). Implications of the vortical flow patterns behind the primary stenosis to the formation of microemboli and downstream stenoses are as follows. Elevated platelet concentrations due to accumulation in recirculation zones mixed with thrombin and ADP complexes assumed to be released upstream in high wall shear stress regions, could form microemboli, which are convected downstream. Distinct near-wall vortices causing a local increase in the WSSG and OSI as well as blood-particle entrainment with possible wall deposition, indicate sites susceptible to the onset of an additional stenosis proximal to the initial geometric disturbance.
It has been suggested that an impaired thrombomodulin (TM) function could constitute an abnormality leading to thromboembolic disease (TED). The TM gene from 51 unrelated American patients with TED and 100 American bl...
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It has been suggested that an impaired thrombomodulin (TM) function could constitute an abnormality leading to thromboembolic disease (TED). The TM gene from 51 unrelated American patients with TED and 100 American blood donors was screened for mutations. Four heterozygous point mutations in the TM gene were detected. The mutations are distributed throughout the TM gene and predict amino acid changes 1) pro(483) to Leu, 2) Gly(61) to Ala, 3) Asp(468) to Tyr (earlier described) and 4) a silent mutation not predicting any amino acid change at Glu(163). Family studies reveal that the occurrence of the different TM mutations is associated with a history of TED, but there are indications of multiple risk factors and no perfect co-segregation of the TM defects and TED. Among the controls, three individuals carried heterozygous TM variants predicting either a pro(477)-Ser mutation (two cases) or an Asp(468)-Tyr mutation. Our results thus demonstrate that a previously undocumented abnormality in the protein C anticoagulant pathway, a defect in the TM gene, to a certain extent co-segregates with familial thrombophilia. Further studies are needed to prove the causality of these TM mutations.
The outcome for children with deep vein thrombosis (DVT) and pulmonary embolism (PE) is unknown. An understanding of morbidity and mortality of DVT/PE is crucial to the development of rational treatment protocols. The...
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The outcome for children with deep vein thrombosis (DVT) and pulmonary embolism (PE) is unknown. An understanding of morbidity and mortality of DVT/PE is crucial to the development of rational treatment protocols. The Canadian Childhood Thrombophilia Registry has followed 405 children aged 1 mo to 18 y with DVT/PE for a mean of 2.86 y (range, 2 wk to 6 y) to assess outcome. The all-cause mortality was 65 of 405 children (16%). Mortality directly attributable to DVT/PE occurred in nine children (2.2%), all of whom had central venous line-associated thrombosis. Morbidity was substantial, with 33 children (8.1%) having recurrent thrombosis, and 50 children (12.4%) having postphlebitic syndrome. Recurrent thrombosis and postphlebitic syndrome were more common in older children, although deaths occurred equally in all age groups. The incidence of recurrent thrombosis and postphlebitic syndrome are likely underestimated because of difficulties in diagnosis, especially in younger children. The significant mortality and morbidity found in our study supports the need for international multicenter randomized clinical trials to determine optimal prophylactic and therapeutic treatment for children with DVT/PE.
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