Flow changes in the aorta associated with the deployment of a AAA stent graft

The purpose of this study was to investigate the hemodynamic implications of a proximal shift in the aortic bifurcation that results from abdominal aortic aneurysm (AAA) stent graft deployment. A flow model was constructed in which an anatomically accurate model of the aorta was subjected to physiologic pulsatile flow. The model included the celiac, superior mesenteric, left and right renal arteries. The aortic bifurcation, leading to the right and left iliac arteries was included, as well as the lumbar curvature. Flow simulations were performed under resting and mild exercise conditions with and without a Cordis AAA stent graft deployed. Flow patterns were visualized with dye injection and recorded onto video. The flow rates through the iliac and renal arteries were continuously monitored using ultrasonic flowmeters. Flow visualization revealed that flow disturbances at the level of the renal arteries were slightly increased with the deployment of the stent graft. The orientation of the endolegs within the aorta had no perceptible effect on these disturbances. Under mild exercise conditions, very little flow disturbance was observed. In conclusion, there are slight changes in flow disturbance near the renal arteries due to stent graft deployment, but these changes would not be expected to have significant clinical implications.     

Method for Assessing the Need for Case-Specific Hemodynamics: Application to the Distribution of Vascular Permeability

A common approach to understanding the role of hemodynamics in atherogenesis is to seek relationships between parameters of the hemodynamic environment, and the distribution of tissue variables thought to be indicative of early disease. An important question arising in such investigations is whether the distributions of tissue variables are sufficiently similar among cases to permit them to be described by an ensemble average distribution. If they are, the hemodynamic environment needs be determined only once, for a nominal representative geometry; if not, the hemodynamic environment must be obtained for each case. A method for classifying distributions from multiple cases to answer this question is proposed and applied to the distributions of the uptake of Evans blue dye labeled albumin by the external iliac arteries of swine in response to a step increase in flow. It is found that the uptake patterns in the proximal segment of the arteries, between the aortic trifurcation and the ostium of the circumflex iliac artery, show considerable case-to-case variability. In the distal segment, extending to the deep femoral ostium, many cases show very little spatial variation, and the patterns in those that do are similar among the cases. Thus the response of the distal segment may be understood with fewer simulations, but the proximal segment has more information to offer. © 2000 Biomedical Engineering Society. PAC00: 8719Uv, 8719Xx     

The anterior visceral branches of the abdominal aorta and their relationship to the renal arteries

Variations in the anatomy of the abdominal aorta and its branches are of interest as vessel geometry not only determines flow dynamics, but is also crucial in the pathogenesis of vascular disease. The relationship between the anterior visceral and renal arteries is important when undertaking diagnostic arteriography and endovascular interventions. To examine these relationships, the length of the abdominal aorta was determined and measurements taken of the position of origin of the celiac artery, superior mesenteric artery (SMA), inferior mesenteric artery (IMA) and renal arteries, as well as the three-dimensional projection of each vessel from the aorta. The mean level of bifurcation of the aorta was at the lower third of the body of L4, with the celiac artery, SMA, renal arteries and IMA arising at the level of the T12/L1 intervertebral disc, upper third of the body of L1, lower third of the body of L1 and lower third of the body of L3, respectively. The horizontal projection of the celiac artery, SMA and IMA was to the left of the midline; in the sagittal plane, the celiac artery and SMA projected anteriorly and the IMA posteriorly; in the coronal plane all vessels projected inferiorly, with the SMA to the right and the IMA to the left. The celiac artery, SMA and both renal arteries all arise from the proximal half of the abdominal aorta within 45 mm of each other, with the origins of the renal arteries being remarkably consistent. It is concluded that the celiac artery and SMA are both useful landmarks for determining the position of the renal arteries.     

Umbilical artery catheterization complicated by multiple mycotic aortic aneurysms

A premature infant had three pseudoaneurysms of the thoracic and abdominal aorta secondary to umbilical artery catheterization and sepsis. The infant had septicemia as the direct result of bacterial contamination of an umbilical artery catheter with Staphylococcus aureus. The thoracic pseudoaneurysm caused massive hemothorax and the infant's death. The upper abdominal aortic aneurysm developed at the level of the renal arteries and caused decreased left renal blood flow and renal hypoplasia. The lower abdominal aneurysm involved the right iliac artery and was complicated by mural thrombosis and ischemia of the right leg. To our knowledge, this is the first published case of multiple mycotic aortic aneurysms after umbilical artery catheterization.     

Contractile Responses in Arteries Subjected to Hypertensive Pressure in Seven-Day Organ Culture

Early stage changes in hypertensive arteries have a significant effect on the long-term adaptation of the arteries. Compared to the long-term adaptation, little is known about the early dimensional and functional changes in hypertensive arteries in the first few days of hypertension. To study the early stage changes in hypertensive arteries, porcine common carotid arteries were cultured for seven days in a simplified ex vivo artery organ culture system with pulsatile flow under hypertensive (200±30 mm Hg) or normotensive (100±20 mm Hg) pressure conditions while maintaining a physiological mean wall shear stress of 15 dyn/cm².Vessel viability was demonstrated by contractile diameter responses to norepinephrine (NE), carbachol (CCh), and sodium nitroprusside (SNP) as well as staining for mitochondrial activity and cell apoptosis/necrosis. The results show that arteries demonstrated strong contractile responses to NE, CCh, and SNP, basal tone, and viable mitochondria in the organ culture system for seven days. Hypertensive arteries demonstrated a stronger contractile response than normotensive arteries (p < 0.05). Diameter enlargement was observed in hypertensive arteries as compared to arteries cultured under normotensive conditions. In conclusion, the pulsatile culture system can maintain arteries viable with active vasomotion tone for up to seven days. Hypertensive pressure causes arterial adaptation by significantly increasing arterial diameter and contractile response within the first seven days. © 2001 Biomedical Engineering Society. PAC01: 8719Uv, 8719Rr, 8780Rb     

Origin of anterior descending coronary artery from right aortic sinus. Intramyocardial tunneling to left side of heart

We report a rare case of a coronary anomaly. All of the coronary arteries originated from a single ostium located in the right coronary cusp. The single coronary artery had a main branch corresponding to the usually dominant right coronary artery. The left anterior descending coronary artery arose from the right coronary artery and coursed intramyocardially within the right ventricular outflow tract to the anterior interventricular sulcus. The absence of evidence of myocardial ischemia in our patient, both clinically and at autopsy, and in three cases reported previously, suggests that the condition reported here was an unlikely cause of myocardial ischemia.     

Numerical Simulation and Experimental Validation of Blood Flow in Arteries with Structured-Tree Outflow Conditions

Blood flow in the large systemic arteries is modeled using one-dimensional equations derived from the axisymmetric Navier–Stokes equations for flow in compliant and tapering vessels. The arterial tree is truncated after the first few generations of large arteries with the remaining small arteries and arterioles providing outflow boundary conditions for the large arteries. By modeling the small arteries and arterioles as a structured tree, a semi-analytical approach based on a linearized version of the governing equations can be used to derive an expression for the root impedance of the structured tree in the frequency domain. In the time domain, this provides the proper outflow boundary condition. The structured tree is a binary asymmetric tree in which the radii of the daughter vessels are scaled linearly with the radius of the parent vessel. Blood flow and pressure in the large vessels are computed as functions of time and axial distance within each of the arteries. Comparison between the simulations and magnetic resonance measurements in the ascending aorta and nine peripheral locations in one individual shows excellent agreement between the two. © 2000 Biomedical Engineering Society. PAC00: 8719Uv     

Effects of Cardiac Motion on Right Coronary Artery Hemodynamics

The purpose of this work was to investigate the effects of physiologically realistic cardiac-induced motion on hemodynamics in human right coronary arteries. The blood flow patterns were numerically simulated in a modeled right coronary artery (RCA) having a uniform circular cross section of 2.48 mm diam. Arterial motion was specified based on biplane cineangiograms, and incorporated physiologically realistic bending and torsion. Simulations were carried out with steady and pulsatile inflow conditions (mean Re_D=233, =1.82) in both fixed and moving RCA models, to evaluate the relative importance of RCA motion, flow pulsation, and the interaction between motion and flow pulsation. RCA motion with a steady inlet flow rate caused variations in wall shear stress (WSS) magnitude up to 150% of the inlet Poiseuille value. There was significant spatial variability in the magnitude of this motion-induced WSS variation. However, the time-averaged WSS distribution was similar to that predicted in a static model representing the time-averaged geometry. Furthermore, the effects of flow pulsatility dominated RCA motion-induced effects; specifically, there were only modest differences in the WSS history between simulations conducted in fixed and moving RCA models with pulsatile inflow. RCA motion has little effect on time-averaged WSS patterns. It has a larger effect on the temporal variation of WSS, but even this effect is overshadowed by the variations in WSS due to flow pulsation. The hemodynamic effects of RCA motion can, therefore, be ignored as a first approximation in modeling studies. © 2003 Biomedical Engineering Society. PAC2003: 8719Uv, 8719Hh, 8719St, 8719Rr     

THE RELATIONSHIP BETWEEN ARTERIOSCLEROSIS AND THE WAVE LINE OF AORTA

The wave line is a structure that is frequently observed in aorta. Grossly this structure (wave line), measuring 0.3 0.5 cm in width and 5–10 cm in length, runs longitudinally or spirally along the long axis of the aorta. The distribution and the relation with arteriosclerotic plaque of wave line were studied. The wave line had three predilection sites: A) the wave line running down from closure of Botallo duct to ostium of 6–8th intercostal artery, B) the wave line between ostium of both renal arteries, C) the wave line running down from lumbar artery to iliac arteries. The wave line observed in the aortae of neonates gradually increased with age. Its frequency is about 80–100% in the second and the third decades. The association of arteriosclerosis with the wave line was frequently observed, especially on "C" region. Fifty-five percent of arteriosclerotic plaques in the fourth decade corresponded with the wave line.     

Intramyocardial Influences on Blood Flow Distributions in the Myocardial Wall

Flow velocity wave forms of coronary arterial inflow and venous outflow of myocardium are influenced by cardiac contraction and relaxation: arterial flow is exclusively diastolic; venous outflow is systolic. We first discuss the intramyocardial microvascular flow dynamics, then present some results of visualization of transmural microvessels by our needle-probe charge coupled device (CCD) microscope, along with an interpretation of the arteriolar and venular hemodynamics through a cardiac cycle. After describing a hierarchical system of coronary microvessels (small artery, arteriole, and capillary), we emphasize the importance of spatial heterogeneity of blood supply to myocardium with reference to a minimal vascular control unit (400 m). An understanding of mechanoenergetic interaction is fundamentally important to an understanding of intramyocardial coronary circulation, and the Physiome Project will provide powerful tools for understanding the integrated role of the intramyocardial microcirculation system. © 2000 Biomedical Engineering Society. PAC00: 8719Hh, 8719Ff, 8719Tt     

Reflex limb dilatation following norepinephrine and angiotensin II in conscious dogs.

Effects of intravenous and intra-arterial norepinephrine (NE) and angiotensin II (AN) were compared in 18 conscious dogs instrumented with Doppler or electromagnetic flow probes on the iliac, mesenteric, and renal arteries, and catheters in the aorta and iliac arteries. NE and AN administered intravenously constricted the mesenteric and renal beds, and constricted the iliac bed when administered directly into the iliac artery. In contrast, intravenous NE and AN caused striking reflex increases in iliac flow and reductions in iliac resistance, respectively, in 12 of 18 dogs studied. The reflex iliac dilatation was not prevented by beta blockade with propranolol, cholinergic blockade with atropine, or prostaglandin synthetase inhibition with indomethacin. However, the responses were abolished by either phentolamine, 1 mg/kv iv, or after local blockade of the limb with either phentolamine, 0.5 mg/kg, or with tripelennamine, 2 mg/kg. The dilatation was not prevented by either bilateral carotid sinus and aortic nerve section or by bilateral vagotomy alone, but was prevented by a combination of these procedures. Thus, intravenous NE and AN cause striking reflex iliac dilatation in the limb in the conscious dog; the afferent arc of this reflex involves both arterial baroreceptor and vagal pathways, while the efferent mechanism involves an interaction of alpha-adrenergic and histaminergic receptors.     

Role of tissue hypoxia in cerebrovascular regulation: a mathematical modeling study

This paper presents a mathematical model of cerebrovascular regulation, in which emphasis is given to the role of tissue hypoxia on cerebral blood flow (CBF). In the model, three different mechanisms are assumed to work on smooth muscle tension at the level of large and small pial arteries: CO₂reactivity, tissue hypoxia, and a third mechanism necessary to provide good reproduction of autoregulation to cerebral perfusion pressure (CPP) changes. Using a single set of parameters for the mechanism gains, assigned via a best fitting procedure, the model is able to reproduce the pattern of pial artery caliber and CBF under a large variety of physiological stimuli, either acting separately (hypoxia, CPP changes, CO₂ pressure changes) or in combination (hypercapnia+hypoxia; hypercapnia+hypotension). Furthermore, the model can explain the increase in CBF and the vasoconstriction of small pial arteries observed experimentally during hemodilution, ascribing it to the decrease in blood viscosity and to the antagonistic action of the flow-dependent mechanism (responsible for vasoconstriction) and of hypoxia (responsible for vasodilation). Finally, the interaction between hypoxia and intracranial pressure (ICP) has been analyzed. This interaction turns out quite complex, leading to different ICP time patterns depending on the status of the cerebrospinal fluid outflow pathways and of intracranial compliance. © 2001 Biomedical Engineering Society. PAC01: 8719Uv, 8719Tt, 8719Ff, 8380Lz     

Sequential analysis of single-center experience of living donor kidney transplants with several vascular anastomosis techniques

Background and aimVascular variations of grafts are handled with various reconstruction techniques in renal transplantation. We aimed to analyze the effects of these reconstruction techniques and sites on patient/graft outcomes.Materials and methodsRenal transplantation cases at the Transplantation Unit of the General Surgery Department, İstanbul University Cerrahpaşa Medical Faculty between January 1st, 2000 and December 31st, 2012 were analyzed retrospectively. Postoperative duplex ultrasound results, urea-creatinine reduction rates, and complications were evaluated.ResultsThere were 228 living-donor transplantation cases evaluated. For single-renal-artery living-donor transplantations, there were 45 end-to-side external iliac artery, 15 end-to-side internal iliac artery, 152 end-to-end internal iliac artery, and 3 end-to-side common iliac artery anastomoses performed. In cases with double-arteries, 3 had end-to-side external iliac artery anastomoses, and 10 had endto-end internal iliac artery anastomoses. No statistically significant differences were found between reconstruction techniques with regard to complications or urea-creatinine reduction rates.ConclusionInternal, external, and common iliac arteries can be safely used for anastomoses. The presence of more than one renal artery creates no short or long-term problems when a side-to-side anastomosis is initially performed.     

Unusual origin and course of the testicular arteries

Background The testicular arteries usually arise from the anterolateral aspect of the abdominal aorta just inferior to the renal arteries at the level of the second lumbar vertebra. However, they may also originate from the renal artery, middle suprarenal artery, one of the lumbar arteries, common or internal iliac artery, or the superior epigastric artery. Methods An unusual origin of the right testicular artery and an unusual course of the left one were observed during routine dissection of the retroperitoneal space of a 43-year-old male cadaver. Results The right testicular artery originated from the inferior segmental branch of the right renal artery. After the left testicular artery originated from the anterolateral surface of the abdominal aorta just inferior to the left renal artery it was located between the left renal vein and the left renal artery and descended anterior to the renal vein. Thereafter it coursed on its normal route distally with the testicular vein. Conclusions Awareness of variations of the testicular arteries, such as that shown in this case, is important during surgical and radiological procedures pertaining to kidney.     

Anatomical Variations in the Aortic Bifurcation in New Zealand White Rabbits on Arteriography

The radiologic anatomy of the aortic bifurcation in the rabbit has received little study but it is important as this anatomical area is widely used in atherosclerosis research. Thirty rabbits were used to study the aortic bifurcation and subsequent branching patterns on arteriography. Fifteen different arteries were identified. Mean arterial diameters of 2.88 ± 0.7 and 2.27 ± 0.55 mm were obtained for the aorta and external iliac arteries, respectively. The cranial and middle aspects at the seventh lumbar vertebra (L7) were the most frequent anatomical landmarks (53.3% of the cases) for aortic and common iliac bifurcations, respectively. The caudal aspect of L6 was the most frequent origin (50% of the cases) for the median sacral artery. Deep circumflex iliac arteries originated from common iliac arteries and not the abdominal aorta in the rabbit, showing anatomical asymmetry in 73.3% of the cases. No gender disparity was found in the anatomical location of any of the arteries of the study. Knowledge of normal vascular landmarks for the aortic bifurcation as well as anatomical variations should be helpful to future experimental studies. Anat Rec, 297:663–669, 2014. © 2014 Wiley Periodicals, Inc.     

Multiple variations in the paired arteries of the abdominal aorta

Variations in the origin of arteries in the abdomen are very common. The arteries that show frequent variations include the celiac trunk, renal arteries, and gonadal arteries. We observed multiple variations in a 45-year-old male cadaver. The variations found on the left side were: one accessory renal artery, two testicular arteries, and middle suprarenal and inferior phrenic arteries that branched from the celiac trunk. On the right side, the inferior phrenic and middle suprarenal arteries arose from the right renal artery.     

移植肾血管变异的临床处理

背景：血管吻合技术的好坏直接关系到肾移植的成败。 目的：提高肾移植变异血管吻合的技术方法。 方法：1999年9月至2010年12月广东省第二人民医院器官移植科共完成878例肾移植,对其中供肾存在的动静脉血管变异进行修整、合并、延长等重建处理后进行移植,副肾动脉采用改良支架支撑法同腹壁下动脉吻合。 结果与结论：878例肾移植中,55例供肾动脉变异,肾静脉变异22例,经血管修整重建后均成功与受者髂内或髂外血管吻合。23例直径大于1 mm副肾动脉与腹壁下动脉吻合均取得成功。移植后彩超显示肾动静脉吻合口血流及副肾动脉血流正常。提示移植肾血管变异及副肾动脉只要正确处理,吻合得当,可以安全有效地移植给受者并获良好效果。     

Changes of zero-bending-moment states and structures of rat arteries in response to a step lowering of the blood pressure

There are many papers on tissue remodeling of blood vessels in hypertension, but there are few documents describing the tissue remodeling of the blood vessels following a step lowering of the blood pressure. The present article presents data on the opening angle, the vessel wall thickness, and the thicknesses of the intima-media and adventitia layers of the blood vessels of the lower body (the abdominal aorta, and the common iliac, femoral, saphenous branch, medial plantar, and plantar metatarsal arteries) of the rat after a step lowering of the blood pressure and flow by a controlled constriction of the aorta below both renal arteries. We found a pattern of changes that depend on space (location on the vascular tree), time (after the blood pressure change), and the intensity of disturbance. We model mathematically the dynamics shown by the experimental results by means of the indicial response functions, which are defined as the morphometric changes in response to a step decrease of blood pressure or blood flow. Under the hypothesis that there is a range of linearity between the degree of tissue remodeling and the amplitude of the pressure change, we can use the indicial functions to predict the remodeling of the vessel under an arbitrary history of decreasing blood pressure; and conversely, we can compute the indicial response functions from pertinent results of a single experiment. The totality of all our experiments is consistent with the linearity hypothesis within the range of the experiment. The mathematical analysis and the formulas are presented in the Appendix. © 2002 Biomedical Engineering Society. PAC2002: 8719Uv, 8719Rr     

The relationship between arteriosclerosis and the wave line of aorta

The wave line is a structure that is frequently observed in aorta. Grossly this structure (wave line), measuring 0.3-0.5 cm in width and 5-10 cm in length, runs longitudinally or spirally along the long axis of the aorta. The distribution and the relation with arteriosclerotic plaque of wave line were studied. The wave line had three predilection sites: A) the wave line running down from closure of Botallo duct to ostium of 6-8th intercostal artery, B) the wave line between ostium of both renal arteries, C) the wave line running down from lumbar artery to iliac arteries. The wave line observed in the aortae of neonates gradually increased with age. Its frequency is about 80-100% in the second and the third decades. The association of arteriosclerosis with the wave line was frequently observed, especially on "C" region. Fifty-five percent of arteriosclerotic plaques in the fourth decade corresponded with the wave line.     

Rare origin of supernumerary renal vessels supplying the lower pole of the left kidney

The current observations have documented rare vascular anomalies in the right and left kidneys from a male and female cadaver, respectively. In the female left kidney in addition to being supplied by the normal renal artery and vein it contained a left lower polar renal artery and vein. The polar artery took origin from the inferior mesenteric artery to supply the lower pole and was drained by the left lower polar vein that opened into the left common iliac vein. The right kidney from a male cadaver showed supernumerary renal arteries and veins. The supernumerary upper renal artery took origin from the aorta and after a short course it gave rise into a cranial branch that took a long course to supply the lower pole and a caudal branch that entered the right kidney at the hilum. The supernumerary lower renal artery also took origin from the aorta and passed to supply the lower pole of the right kidney. Therefore, the lower pole of the right kidney received two arteries, but was not associated with a polar vein. The right kidney in addition to the normal right renal vein contained a supernumerary right renal vein. The vein was seen at the hilum and was the most posterior structure; passing behind the supernumerary lower renal artery to open into the posterior surface of the inferior vena cava. The anomalies described in the current observation present a unique pattern of congenital renal vascular abnormalities that may be of surgical importance.