The stent was a major breakthrough in the treatment of atherosclerotic vascular disease. The permanent vascular implant of a stent, however, changes the intra-stent blood flow hemodynamics. There is a growing consensu...The stent was a major breakthrough in the treatment of atherosclerotic vascular disease. The permanent vascular implant of a stent, however, changes the intra-stent blood flow hemodynamics. There is a growing consensus that the stent implant may change the artery wall shear stress distribution and hence lead to the restenosis process. Computational fluid dynamics （CFD） has been widely used to analyze hemodynamics in stented arteries. In this paper, two CFD models （the axisymmetric model and the 3-D stent model） were developed to investigate the effects of strut geometry and blood rheology on the intra-stent hemodynamics. The velocity profile, flow recirculation, and wall shear stress distribution of various stent strut geometries were studied. Results show strong correlations between the intra-stent hemodynamics and strut geometry. The intra-stent blood flow is very sensitive to the strut height and fillet size. A round strut with a large fillet size shows 36% and 34% reductions in key parameters evaluating the restenosis risk for the axisymmetric model and the 3-D stent model, respectively. This suggests that electrochemical polishing, a surface-improving process during stent manufacturing, strongly influences the hemodynamic behavior in stented arteries and should be controlled precisely in order to achieve the best clinical outcome. Rheological effects on the wall shear stress are minor in both axisymmetric and 3-D stent models for the vessel diameter of 4 mm, with Newtonian flow simulation tending to give more conservative estimates ofrestenosis risk. Therefore, it is reasonable to simulate the blood flow as a Newtonian flow in stented arteries using the simpler axisymmetric model. These findings will provide great insights for stent design optimization for potential restenosis improvement.展开更多
A 34-year-old man admitted to our de- partment with complex blunt pancreaticoduodenal injury af- ter a car accident. The wall of the first, second, and third portions of the duodenum was extensively lacerated, and the...A 34-year-old man admitted to our de- partment with complex blunt pancreaticoduodenal injury af- ter a car accident. The wall of the first, second, and third portions of the duodenum was extensively lacerated, and the pancreas was longitudinally transected along the supe- rior mesenteric vein-portal vein trunk. The pancreatic head and the uncinate process were devitalized and the distal common bile duct and the proximal main pancreatic duct were completely detached from the Vater ampulla. The length of the stump of distal common bile located at the cut surface of remnant pancreas was approximately 0.6 cm. A simplified Kausch-Whipple＇s procedure was performed after debride- ment of the devitalized pancreatic head and resection of the damaged duodenum in which the stump of distal common bile duct and the pancreatic remnant were embedded into the jejunal loop. Postoperative wound abscess appeared that eventually recovered by conservative treatment. Dur- ing 16 months follow-up the patient has been stable and healthy. A simplified pancreaticoduodenectomy is a safe alternative for the Whipple procedure in managing complex pancreaticoduodenal injury in a hemodynamically stable patient.展开更多
文摘The stent was a major breakthrough in the treatment of atherosclerotic vascular disease. The permanent vascular implant of a stent, however, changes the intra-stent blood flow hemodynamics. There is a growing consensus that the stent implant may change the artery wall shear stress distribution and hence lead to the restenosis process. Computational fluid dynamics （CFD） has been widely used to analyze hemodynamics in stented arteries. In this paper, two CFD models （the axisymmetric model and the 3-D stent model） were developed to investigate the effects of strut geometry and blood rheology on the intra-stent hemodynamics. The velocity profile, flow recirculation, and wall shear stress distribution of various stent strut geometries were studied. Results show strong correlations between the intra-stent hemodynamics and strut geometry. The intra-stent blood flow is very sensitive to the strut height and fillet size. A round strut with a large fillet size shows 36% and 34% reductions in key parameters evaluating the restenosis risk for the axisymmetric model and the 3-D stent model, respectively. This suggests that electrochemical polishing, a surface-improving process during stent manufacturing, strongly influences the hemodynamic behavior in stented arteries and should be controlled precisely in order to achieve the best clinical outcome. Rheological effects on the wall shear stress are minor in both axisymmetric and 3-D stent models for the vessel diameter of 4 mm, with Newtonian flow simulation tending to give more conservative estimates ofrestenosis risk. Therefore, it is reasonable to simulate the blood flow as a Newtonian flow in stented arteries using the simpler axisymmetric model. These findings will provide great insights for stent design optimization for potential restenosis improvement.
文摘A 34-year-old man admitted to our de- partment with complex blunt pancreaticoduodenal injury af- ter a car accident. The wall of the first, second, and third portions of the duodenum was extensively lacerated, and the pancreas was longitudinally transected along the supe- rior mesenteric vein-portal vein trunk. The pancreatic head and the uncinate process were devitalized and the distal common bile duct and the proximal main pancreatic duct were completely detached from the Vater ampulla. The length of the stump of distal common bile located at the cut surface of remnant pancreas was approximately 0.6 cm. A simplified Kausch-Whipple＇s procedure was performed after debride- ment of the devitalized pancreatic head and resection of the damaged duodenum in which the stump of distal common bile duct and the pancreatic remnant were embedded into the jejunal loop. Postoperative wound abscess appeared that eventually recovered by conservative treatment. Dur- ing 16 months follow-up the patient has been stable and healthy. A simplified pancreaticoduodenectomy is a safe alternative for the Whipple procedure in managing complex pancreaticoduodenal injury in a hemodynamically stable patient.
