Fundamental Study for Simulation of Blood Cell Motion in a Blood Vessel

PURPOSE: The objective of this study is to investigate the blood cell motion in human capillary by applying the boundary singularity method. METHODS: A particle motion of spherical shape falling in a vertical tube filled with Newtonian fluid is studied by using the boundary singularity method and the experiment. RESULTS AND CONCLUSION: As the eccentric ratio increases up to 0.6, the rotational velocity increases almost linearly and the falling velocity remains constant. However, as the eccentric ratio exceeds 0.6, the rotational velocity increases rapidly and the falling velocity decreases. As the tube radius increases, falling velocity increases and approaches the stokes velocity and the rotational velocity decreases.

Fundamental Study for Simulation of Blood Cell Motion in a Blood Vessel

PURPOSE: The objective of this study is to investigate the blood cell motion in human capillary by applying the boundary singularity method. METHODS: A particle motion of spherical shape falling in a vertical tube filled with Newtonian fluid is studied by using the boundary singularity method and the experiment. RESULTS AND CONCLUSION: As the eccentric ratio increases up to 0.6, the rotational velocity increases almost linearly and the falling velocity remains constant. However, as the eccentric ratio exceeds 0.6, the rotational velocity increases rapidly and the falling velocity decreases. As the tube radius increases, falling velocity increases and approaches the stokes velocity and the rotational velocity decreases.

Morphological Changes of the Endothelial Cell under the Influence of the Hemodynamic Stresses

PURPOSE: The objective of this study is to investigate the effects of hemodynamics on morphological changes of human endothelial cells. METHODS: The changes under the laminar flow condition are investigated by the in-vitro experiment and computer simulation. Micrographs of the endothelial cells in the laminar flow chamber are taken as a function of the exposed time. Idealized geometric shapes of the cells whose shapes are changing with the exposed time due to the flow stresses are portrayed by the computer simulation. Drag force on the cell due to the pressure and shear stress is calculated for two constraining conditions, that is, the cell changes its shape keeping its initial volume or initial surface area. RESULTS AND CONCLUSION: The drag force of the cell which keeps constant volume is smaller than that of the cell which keeps constant surface area.

Morphological Changes of the Endothelial Cell under the Influence of the Hemodynamic Stresses

PURPOSE: The objective of this study is to investigate the effects of hemodynamics on morphological changes of human endothelial cells. METHODS: The changes under the laminar flow condition are investigated by the in-vitro experiment and computer simulation. Micrographs of the endothelial cells in the laminar flow chamber are taken as a function of the exposed time. Idealized geometric shapes of the cells whose shapes are changing with the exposed time due to the flow stresses are portrayed by the computer simulation. Drag force on the cell due to the pressure and shear stress is calculated for two constraining conditions, that is, the cell changes its shape keeping its initial volume or initial surface area. RESULTS AND CONCLUSION: The drag force of the cell which keeps constant volume is smaller than that of the cell which keeps constant surface area.

A Case of Post-Carotid Endarterectomy Hyperperfusion Syndrome

Most neurologic complications after carotid endarterectomy (CEA) are ischemic in nature, either embolic or thrombotic. However brain edema can also cause neurologic dysfunction that may be related to hyperperfusion secondary to failure of vascular autoregulation. In Korea there has been no report on hyperperfusion syndrome following CEA. We report the first case of hyperperfusion syndrome in 70 cases of CEA series (1.43%) since November 1994. The patient presented with headache and seizures associated with marked unilateral cerebral hemispheric edema on the sixth post-CEA day. Imaging studies included CT, MRI, MRA, carotid duplex, TCD and SPECT. The possible risk factors for developing hyperperfusion syndrome in this patient included: high-grade stenosis, poor collateral flow, evidence of chronic ipsilateral hypoperfusion, development of immediate post-CEA hypertension, and post-CEA increment of internal carotid artery blood flow velocity to 190% of the pre-CEA level on follow-up TCD. Cerebral hyperperfusion syndrome is a rare but significant complication of CEA that may be reversible. Hyperperfusion syndrome should be questioned if the patient develops a new neurological problem after CEA.

Analysis of the Venous Hemodynamic Changes in the Primary Varicose Vein of the Lower Limbs

PURPOSE: To evaluate the changes of venous hemodynamics after the treatment of the primary varicose vein of the lower limbs. METHODS: We retrospectively analyzed 493 lower limbs (221 right and 272 left, 157 male and 336 female) who underwent surgery for the primary varicose veins from September 1994 to May 1999. All patients were evaluated using air-plethysmography (APG) pre-and post-operatively. RESULTS: The prevalent age was 40 to 49-year-old and the male to female ratio was 1:2. Presumed etiological factors included occupations requiring long periods of standing in 94 cases, and pregnancy in 188 female cases. The average duration of illness was 12.9+/-8.2 years. 232 limbs were treated with a method of the greater saphenous vein high ligation (GSV HL) and above knee (AK) stripping with varicosectomy (VS), 38 limbs with GSV HL and total stripping and VS, 101 with short saphenous vein HL and VS, 100 with external banding valvuloplasty of GSV and VS, 5 with external banding valvuloplasty of GSV only, 10 with Linton's operation, 6 with GSV branch ligation and VS, and sclerotherapy in 9. The reduction rate of venous volume (VV) were 13.9+/-6.6 % in GSV stripping group and 20.4+/-18.2% in GSV valvuloplasty group. The reduction rate of venous filling index (VFI) were 53.6+/-31.0% in GSV stripping group and 58.9+/-33.7% in GSV valvuloplasty group. The increasing rate of ejection fraction (EF) were 26.9+/-41.1% in GSV stripping group and 21.1+/- 32.2% in GSV valvuloplasty group. The reduction rate of ambulatory venous pressure (AVP) were 4.4+/-128% in GSV stripping group and 22.7+/-73.3% in GSV valvuloplasty group. CONCLUSION: In patients with primary varicose vein of the lower limbs, APG could be a useful method for the documentation of hemodynamic improvement by showing decrease in VV, VFI, AVP and increase in EF.

Prevalence of Asymptomatic Carotid Atherosclerosis in Korea

PURPOSE: To investigate the prevalence and risk factors of atherosclerotic disease of the extracranial carotid artery in healthy Korean population. METHODS: Eight hundred twenty-five patients without previous history of transient ischemic attack, amaurosis fugax, and/or any neurologic deficit who underwent carotid artery ultrasonography were evaluated retrospectively. The patients were divided into five groups according to the degree of carotid artery stenosis using real-time B-mode high resolution ultrasonography; Group A-normal carotid artery, Group B-below 30% of carotid artery stenosis, Group C-from 31% to 50% of carotid artery stenosis, Group D-from 51% to 70% of carotid artery stenosis, Group E-above 71% of carotid artery stenosis. Medical Records of all patients were investigated for following factors; sex, age, family history, smoking, hypertension, diabetes mellitus, total cholesterol, HDL- cholesterol, LDL-cholesterol, TG (triglyceride), HbA-1c (hemoglobin A-1c), and folate. RESULTS: 12.5% of asymptomatic patients have carotid stenosis due to atherosclerosis of extracranial carotid artery. The prevalence of extracranial carotid artery stenosis was as follows; Group B: 2.2%, Group C: 7.0%, Group D: 3.0%. The age, total cholesterol, LDL-cholesterol and HbA-1c were significantly higher in Group B, C, D than Group A (P=0.001, 0.016, 0.011, 0.001). The prevalence of diabetes and hypertension were significantly higher in Group B, C, D than Group A. Other factors, however, were not different among the groups. CONCLUSION: Asymptomatic carotid artherosclerosis is not uncommon in Korea. Carotid ultrasonography would be necessary for patients with hypertension, diabetes, and high serum cholesterol level.

Sclerotherapy with Pure Ethanol in Congenital Vascular Malformations Preliminary report

Congenital vascular malformations (CVM) have many different clinical presentations, ranging from an asymptomatic birthmark to a life-threatening status. There has been confusion in the classification of these malformations. Two major classification systems are used at the present time: one is the Mulliken and coworkers' system that has been adopted by the International Society for the Study of Vascular Anomalies, and the other is the Hamburg classification that was declared in the 7th Meeting of the International Workshop on Vascular Malformations in Hamburg 1988. The latter is used in this article. BACKGROUND: There are many difficulties in the surgical extirpation of CVM because of their invasiveness, variability, hypervascularity, and evolutibility, especially in a diffuse infiltrating type of CVM. Thus, many endovascular ablative agents have been utilized since 1930s, but there were some handicaps, such as recanalization of previously treated vessels. Since the 1980s, Yakes has reported on much research about the effectiveness of absolute alcohol (98% ethyl alcohol) which incurs permanent vessel wall destruction. AIMS: We performed this study to evaluate the effectiveness of pure ethanol (95-99% ethyl alcohol, Samsung Medical Center, Seoul, Korea) in the treatment of inoperable CVM, to identify the complications that occur and to establish the method of endovascular ablative therapy. MATERIALS AND METHODS: From August 1996 through October 1997, we applied 37 sessions of sclerotherapy using direct puncture technique with pure ethanol to 19 patients with the extratruncular, diffuse infiltrating type of CVM (11 predominantly venous, 8 predominantly arteriovenous shunting)among 250 CVM patients registered at the CVM Clinic of Vascular Center at Samsung Medical Center. RESULTS: Angiographically, the results were excellent in 33 (89%) and good in 3 (9%) sessions. Only one (3%) session failed due to extravasation of the contrast media. The mean follow-up period was only 6 months; 17 (89%) patients were symptomatically improved. Some complications, such as ischemic bullae, deep vein thrombosis, and hematuria, developed, but those patients were recovered without any problem. CONCLUSIONS: The short-term results of pure ethanol sclerotherapy for the diffuse infiltrating type of CVM were good. With more clinical experience, this new treatment modality will be more effective. Further investigations are needed to solve the some complications.

An Experience of Carotid-Carotid Bypass In Innominate Artery Stenosis

Innominate artery stenosis rarely cause irreversible neulogic changes, but symptoms and disability do occur. Stenosis lesions cause hypoperfusion, while microemboli may arise from ulcerative plaques. Symptoms include vertigo, ataxia, dizziness, syncope, cerebellar transient ischemic attacks. Surgical correction of stenotic lesions may relieve symptoms, but the best operative approch will vary depending on the site the obstruction or the multiplicity of arteries involved. The authors report a case of innominate artery stenosis with carotid-carotid bypass using polytetrafluoroethylene graft.