It has been found that the incidence of cardiovascular disease in patients with lower limb amputation is significantly higher than that in normal individuals, but the relationship between lower limb amputation and the episodes of cardiovascular disease has not been studied from the perspective of hemodynamics. In this paper, numerical simulation was used to study the effects of amputation on aortic hemodynamics by changing peripheral impedance and capacitance. The final results showed that after amputation, the aortic blood pressure increased, the time averaged wall shear stress of the infrarenal abdominal aorta decreased and the oscillatory shear index of the left and right sides was asymmetrically distributed, while the time averaged wall shear stress of the iliac artery decreased and the oscillatory shear index increased. The changes above were more significant with the increase of amputation level, which will result in a higher incidence of atherosclerosis and abdominal aortic aneurysm. These findings preliminarily revealed the influence of lower limb amputation on the occurrence of cardiovascular diseases, and provided theoretical guidance for the design of rehabilitation training and the optimization of cardiovascular diseases treatment.
Amputation ; Aorta, Abdominal/surgery* ; Aortic Aneurysm, Abdominal/surgery* ; Blood Flow Velocity/physiology* ; Hemodynamics/physiology* ; Humans ; Lower Extremity ; Models, Cardiovascular ; Stress, Mechanical

The objective of the present study was to evaluate the hemodynamic characteristics of an atherosclerosis-prone coronary artery compared to the aorta. We describe three- dimensional spatial patterns of wall shear stress (WSS) according to the impedance phase angle in pulsatile coronary and aorta models using in vivo hemodynamic parameters and computed numerical simulations both qualitatively and quantitatively. Angiography of coronary arteries and aortas were done to obtain a standard model of vascular geometry. Simultaneously to the physiologic studies, flow-velocity and pressure profiles from in vivo data of the intravascular Doppler and pressure wire studies allowed us to include in vitro numerical simulations. Hemodynamic variables, such as flow-velocity, pressure and WSS in the coronary and aorta models were calculated taking into account the effects of vessel compliance and phase angle between pressure and flow waveforms. We found that there were spatial fluctuations of WSS and in the recirculation areas at the curved outer wall surface of the coronary artery. The mean WSS of the calculated negative phase angle increased in the coronary artery model over that in the aorta model and the phase angle effect was most prominent on the calculated amplitude of WSS of the coronary artery. This study suggests that the rheologic property of coronary circulation, such as the fluctuation of WSS/WSR induces several hemodynamic characteristics. A separation of flow-velocity, a difference in phase between pressure conductance and blood flow and prominent temporal and/or spatial oscillatory fluctuations of the shear forces as a function of pulsatile flow might be important factors in atherogenesis and progression of atherosclerosis.
Adult ; Aged ; Aorta, Abdominal/*physiology ; Arteriosclerosis/etiology/*physiopathology ; Coronary Circulation ; Coronary Vessels/*physiology ; Electric Impedance ; Female ; *Hemodynamics ; Human ; Male ; Middle Age ; Stress, Mechanical

The hemodynamic characteristics of abdominal arterial bifurcation, such as blood flowing velocity vector, the shear stress at the vessel wall were calculated, studied and compared using the newly-induced boundary element method in this study. It was analysed why the atherosclerosis is asymmetrical at the bifurcation of abdominal arterial. The hemodynamic causes of production and development of the atherosclerotic were reasonabley explained by the shear stress calculation results of left and right common iliac branch vessel walls before and after the lesions. It is shown that the distribution of blood flowing velocity vector, the shear stress at the vessel wall are asymmetrical because of the asymmetrical geometry at the bifurcation of abdominal arterial, so that the shear stress of inner wall is higher than outside. The inner wall shear stress of right common iliac is higher than left. Blood velocity and shear stress increase at the atherosclerotic lesion because the blood vessel becomes narrower, and the blood velocity and shear stress decrease at the downstream of the lesion. It was also shown that the hemodynamic characteristics played a great important role in the occurrence and development of the atherosclerosis diseases at the bifurcation of abdominal arterial. Because of the increase of the shear stress, the atherosclerotic plaque surface will be damaged, leading to tissue hyperplasia. It will be lead to blood cell coacervation that the blood velocity and shear stress decrease at the atherosclerotic plaque downstream.
Aorta, Abdominal ; pathology ; physiopathology ; Atherosclerosis ; pathology ; physiopathology ; Blood Flow Velocity ; physiology ; Finite Element Analysis ; Hemodynamics ; Humans ; Shear Strength ; physiology ; Stress, Mechanical

To investigate the cellular mechanisms of pressure-overload cardiac hypertrophy transition to heart failure, we observed time course of changes in morphology and contractile function of cardiomyocytes in transverse abdominal aortic constriction (TAC) rats. Since TAC rats suffered higher stress, body weight had a slower growth rate compared with that of synchronous control rats. Therefore, the left ventricular to body weight ratio produced experimental bias to evaluate the degree of cardiac hypertrophy. Length and width of collagenase-isolated cardiomyocyte were directly measured. Length, width and calculated surface area of cardiomyocyte showed a progressive increase in 8-, 16-, and 20-week TAC rats. The increasing rate of surface area in cardiomyocytes was higher at the middle stage of TAC (from the eighth to sixteenth week). Due to the constraint of fibrosis formation, the increasing rate of surface area in cardiomyocytes was slower at the late stage of TAC (from the sixteenth to twentieth week). The sarcomere length of cardiomyocytes was unchanged, whereas sarcomere numbers were significantly increased in 8-, 16-, and 20-week TAC rats. Shortening amplitude of unloaded contraction in single cardiomyocyte was significantly enhanced in 1-week TAC rats, but not altered in 8-week TAC rats compared with that in the synchronous control rats. On the contrary, unloaded shortening amplitude of single cardiomyocyte was significantly reduced in 16- and 20-week TAC rats. The above results suggest that the reduced shortening amplitude may be associated with intrinsic molecular alterations in hypertrophied cardiomyocytes.
Animals ; Aorta, Abdominal ; Cardiomegaly ; etiology ; physiopathology ; Cell Enlargement ; Constriction ; Hypertension ; complications ; pathology ; physiopathology ; Male ; Myocardial Contraction ; physiology ; Myocytes, Cardiac ; pathology ; physiology ; Rats ; Rats, Sprague-Dawley

OBJECTIVETo establish a mouse model of abdominal aorta stenosis and analyze the alterations in the arterial wall response to high and low shear stress.

METHODSTwenty mouse were randomized equally into 4 groups, including 3 test groups (1, 7 and 14 day groups) with surgically induced stenosis of the abdominal aorta, and a sham-operated group without stenosis. The hemodynamics and the internal diameter of the blood vessel were measured by color Doppler flow imaging. The wall shear stress was calculated by Poiseiulle hydrodynamics formula (τ(m)=η×4×V(m)/D). Pathological examination and immunohistochemistry were performed to observe the arterial morphological changes and the endothelial vascular cell adhesion molecule-1 (VCAM-1) expression. The intimal-media thickness of the aorta was measured and endothelial VCAM-1 expression analyzed quantitatively.

RESULTSRegions of low and high flow shear stress were created upstream from the stenosis and within the stenosis, respectively. Compared with the sham-operated group, the mice with aorta stenosis showed gradually increased vascular intimal-media thickness and VCAM-1 expression intensity in the upstream aorta, but not within the regions of the stenosis.

CONCLUSIONVascular remodeling may occur shortly after exposure to low shear stress, which plays a significant role in initiation and progression of the pathological process of atherosclerosis mediated by VCAM-1, whereas high shear stress may exert an anti-atherosclerotic effect.

Animals ; Aorta, Abdominal ; metabolism ; pathology ; physiopathology ; Aortic Valve Stenosis ; physiopathology ; Atherosclerosis ; physiopathology ; Constriction ; Hemodynamics ; Male ; Mice ; Shear Strength ; physiology ; Stress, Mechanical ; Vascular Cell Adhesion Molecule-1 ; metabolism

OBJECTIVETo observe the effect of polyethylene oxide (PEO) solution at different concentrations on abdominal aortic blood flow and vascular resistance in rats and evaluate the safety and drag-reducing effect of PEO solution.

METHODSThirty-two rats were anesthetized and randomly divided into 4 groups. An ultrasonic flow probe was deployed on the abdominal aorta (5 mm above the common iliac artery) to measure the blood flow. The carotid artery pressure, iliac artery pressure, iliac vein pressure, central venous pressure (CVP) and ECG were also monitored. Saline or different concentrations of PEO [(1x10(-6)(low), 1x10(-5)(middle) and 5x10(-5)(high) g/ml)] were injected in the 4 groups of rats through the caudal vein at a constant rate of 5 ml/h for 20 min, and the changes of the vascular resistance was observed. RESULTS After injections of 1x10(-6) and 1x10(-5) g/ml PEO, the abdominal aortic flow increased significantly (P<0.05) while the vascular resistance was reduced (P(low)=0.052, P(middle)<0.001) as compared to those in the saline control group. Following the injection with 5x10(-5) g/ml PEO, the abdominal aortic flow increased to a threshold in the initial 4 min, after which it rapidly decreased to approach the baseline levels despite continuous infusion. Blood pressure remained stable after the injections except for 5x10(-5) g/mlPEO injection, which resulted in a reduction of the blood pressure by about 10 mmHg (P=0.014). The heart rate and CVP both underwent no significant changes following the injections.

CONCLUSIONThe drag-reducing effect of PEO is closely related to its concentration, and compared with 1x10(-6) g/ml, 1x10(-5) g/ml PEO more effectively increases the blood flow and decreases the resistance. The effectiveness and safety of EPO are attenuated at a concentration higher than 5x10(-5) g/ml.

Animals ; Aorta, Abdominal ; physiology ; Blood Flow Velocity ; drug effects ; Dose-Response Relationship, Drug ; Male ; Polyethylene Glycols ; pharmacology ; Random Allocation ; Rats ; Rats, Wistar ; Vascular Resistance ; drug effects

OBJECTIVETo study the effects of iptakalim (IPT) on pressure-overload induced cardiac remodeling in rats, and investigate correlation between this protection effects and plasma PGI2 content.

METHODThe pressure-overload induced cardiac remodeling model was induced by abdominal aorta constriction for 6 weeks, and the rats were divided into 5 groups repectively: (1) sham group, (2) control group, (3) IPT 3 mg/kg group (IPT 3), (4) indomethacin 2 mg/kg group (Indo 2), (5) indomethacin 2 mg/kg + IPT 3 mg/kg group (Indo 2 + IPT 3). RM6000 eight channel physiological recorder was used to record haemodynamics index, heart weight was weighed and the cardiac remodeling index was calculated, HE stain and Masson's stain were employed to perform histological analysis, colorimetric method was used to detect the hydroxyproline content in cardiac tissue, radioimmunological method was used to measure the plasma PGI2 content.

RESULTSAfter 42 days of aortic banding, the hyperdynamic circulation state, cardiac remodeling and decreased plasma PGI2 content were observed in the model group compared with those in the sham group, which were effectively reserved by treatment with IPT 3 mg/kg. Single-use indomethacin led to further deterioration of this pathophysiological changes, however, combination administration of IPT 3 mg/kg prevented these from worsening characteristic by ameliorating hyperdynamic circulation state and cardiac remodeling, augmnent plasma PGI2 content.

CONCLUSIONIPT can significantly reverse abdominal aorta binding/pressure-overload induced cardiac remodeling, its mechanism may contribute to binding K(ATP) channel in endothelial cells, ameliorating endothelium cells function, augmenting PGI2 synthesis and secretion.

Animals ; Aorta, Abdominal ; surgery ; Constriction ; Endothelium, Vascular ; metabolism ; physiology ; Epoprostenol ; blood ; Hypertension ; blood ; physiopathology ; KATP Channels ; drug effects ; Male ; Propylamines ; pharmacology ; Rats ; Ventricular Remodeling ; drug effects

Stenosis with 55.2% cross section area reduction was introduced into the rabbit aorta. Using Evans blue dye and scanning microscope, we observed the morphology of endothelial cells and the permeability of endothelium to albumin in the stenotic aorta. Numerical simulation of blood flow in the stenotic aorta was performed to obtain the distribution of wall shear rate. The results showed that in the immediately proximal and distal vicinity of stenosis, blood flow was disturbed significantly, resulting in apparent changes in the morphology of endothelial cells and the permeability of endothelium to albumin. These changes were not only attributed to the value of wall shear stress, but also attributed to the flow pattern in the stenosis. The result therefore is in good consistent with the clinical observation that atherosclerosis often occurs in the areas where blood flow is disturbed and flow separation occurs.
Animals ; Aorta, Abdominal ; pathology ; Aortic Diseases ; pathology ; physiopathology ; Atherosclerosis ; etiology ; physiopathology ; Blood Flow Velocity ; Blood Pressure ; Capillary Permeability ; Constriction, Pathologic ; Endothelium, Vascular ; pathology ; physiology ; Hemodynamics ; physiology ; Hemorheology ; methods ; Male ; Models, Cardiovascular ; Permeability ; Pulsatile Flow ; physiology ; Rabbits ; Stress, Mechanical ; Tensile Strength

This study was designed to evaluate the role of bcl-2 transcriptional regulation induced by calmodulin I (CaM I) in pressure overload rat hypertrophic hearts. The model of hypertensive Sprague-Dawley rat was established by abdominal aortic constriction. The hearts were collected four weeks after abdominal aortic constriction. Velocity and isopyknic gradient centrifugation was employed to fractionate rat myocardial nuclei. Western blot analysis revealed a marked increase in phosphorylated cAMP response-element binding protein (pCREB) of cardiac hypertrophy group compared with that in control group (P<0.05), while the protein level of cAMP response-element binding protein (CREB) was constant (P>0.05). Immunohistochemistry results showed a significant increase of CaM I protein in cardiac hypertrophy group relative to the control group (P<0.05). Nuclear run off transcription assay displayed a significant increase in bcl-2 mRNA treated with trifluoperazne compared with non-drug treatment (P<0.05). The results obtained suggest that the transcription of bcl-2 is possibly regulated by CaM I hypertrophic rat hearts, and CREB phosphorylation seems to be a minor factor in bcl-2 transcriptional regulation.
Animals ; Aorta, Abdominal ; pathology ; Calmodulin ; physiology ; Cardiomegaly ; metabolism ; physiopathology ; Constriction ; Cyclic AMP Response Element-Binding Protein ; genetics ; metabolism ; Male ; Phosphorylation ; Proto-Oncogene Proteins c-bcl-2 ; genetics ; metabolism ; RNA, Messenger ; genetics ; metabolism ; Rats ; Rats, Sprague-Dawley

Intravascular administration of magnesium (Mg) causes vasodilation and increases renal blood flow. The aim of this study was to investigate the renal effect of Mg following unclamping of the supraceliac aorta. Mongrels were divided into two groups, control (group C, n=7) and Mg group (group Mg, n=7). In group Mg, 30 mg/kg MgSO4 was injected as a bolus immediately prior to unclamping the supraceliac aorta and thereafter as an infusion (10 mg/kg/hr). The group C received an equivalent volume of saline solution. Systemic hemodynamics, renal artery blood flow, renal cortical blood flow (RCBF), renal vascular resistance, and renal function were compared. Following the aortic unclamping, cardiac output and RCBF were less attenuated, and the systemic and renal vascular resistance was elevated to a lesser degree in the group Mg compared to the group C. There was no significant difference in the plasma renin activity, serum creatinine and Cystatin-C between the two groups. The present study shows that Mg infusion improves systemic hemodynamics and RCBF after aortic unclamping. However, we did not observe any improvement in renal function when Mg was administered after supraceliac aortic unclamping.
Animals ; Aorta, Abdominal/physiology/*surgery ; Blood Pressure/drug effects ; Calcium/blood ; Cardiac Output/drug effects ; Comparative Study ; Creatinine/blood ; Cystatins/blood ; Dogs ; Female ; Heart Rate/drug effects ; Magnesium/blood ; Magnesium Sulfate/*pharmacology ; Male ; Renal Circulation/*drug effects ; Renin/blood ; Research Support, Non-U.S. Gov't