Abdominal Aortic Bifurcation Research Articles

Unilateral multiple variations of renal, phrenic, suprarenal, inferior mesenteric and gonadal arteries

Knowledge of the branching pattern of the abdominal aorta is clinically important for any abdominal surgeon operating on parts of the gut or neighboring structures. Variations of these vessels may influences urological, renal transplantation and laparoscopic surgeries. We present an unreported case of multiple variations of branching pattern of abdominal aorta. It includes double renal arteries for left kidney, a common trunk with right and left phrenic, right and left superior suprarenal and left middle supra renal arteries, and a common trunk originate 2.5 cm above the bifurcation of abdominal aorta gave off inferior mesenteric, accessory renal artery to the left kidney and left testicular arteries in the middle-aged normal male cadaver. The embryogenesis of such multiple variations of branches of abdominal aorta is not clear, but the anatomic consequences may have important clinical implications. Knowledge of these variations is important for urologists, radiologists and surgeons in general.

Diastolic Retrograde Arterial Flow and Biphasic Abdominal Aortic Doppler Wave Pattern: An Early Sign of Arterial Wall Deterioration?

Many authors have found that diastolic retrograde arterial flow is associated with increased stiffness of the arterial wall. Most of the studies were based in femoral or brachial artery examination. As the abdominal aorta is a large vessel routinely explored in abdominal ultrasound scans, we decided to study whether it could be useful for early identification of abnormalities of the arterial wall. Sixteen young and 16 old, healthy patients matched for sex, weight and height were studied using pulsed Doppler at the level of the abdominal aortic bifurcation. Different hemodynamic factors were measured and compared to establish the systolic and diastolic function of this artery. Triphasic wave pattern was present in 14 of 16 patients in the younger group and only in 4 of 16 in the older group. In addition, diastolic retrograde arterial flow duration and retrograde components of diastolic phase were more prominent in the advanced age group. Increased retrograde flow and incapacity to impulse arterial flow forward during diastolic time are early markers of vascular wall deterioration that can be observed easily in the abdominal aorta during routine abdominal ultrasound scans.

Atrial myxoma presenting as total occlusion of the abdominal aorta and its major four branches

The presentations of cardiac myxoma are diverse, from asymptomatic to a variety of symptoms due to embolization. Occlusion of abdominal aortic bifurcation by straddled myxoma is not common; however, obstructive level above renal artery is very rare. We present a patient with cardiac myxoma who presented with acute onset of paraplegia. The aorta was occluded from the level of the liver dome to the renal arteries, and catastrophic outcome (ischemia/reperfusion) following its removal.

PS36. Abdominal Aortic Bifurcation Anatomy and Endograft Limbs Size Affect the Use of Adjunctive Iliac Stenting during Endovascular Abdominal Aortic Aneurysm Repair

Objectives: Post-angioplasty residual stenosis 50% (PRS) of iliac endograft limb after endovascular abdominal aneurysm repair (EVAR) is an indication for intraoperative adjunctive stenting. The aim of the study is to determinate if abdominal aortic bifurcation diameter (AB), ratio of sum of iliac limb diameters to aortic bifurcation diameter (IL/AB) and aortic bifurcation calcification influence the PRS. Methods: Post-angioplasty residual stenosis 50% (PRS) of iliac endograft limb after endovascular abdominal aneurysm repair (EVAR) is an indication for intraoperative adjunctive stenting. The aim of the study is to determinate if abdominal aortic bifurcation diameter (AB), ratio of sum of iliac limb diameters to aortic bifurcation diameter (IL/AB) and aortic bifurcation calcification influence the PRS. Results: Two hundred forty-seven patients (233 men; mean age 74 7 years) with 494 endograft limbs were evaluated. Mean AB was 28.9 mm 12.9 mm. Median endograft iliac leg diameter was 16 mm. AB was 20 mm in 70 patients(28%), IL/AB was 1.4 in 35%, AB 20 mm associated with IL/AB 1.4 in 22% and aortic bifurcation calcification 25% in 61% of patients. Thirty-six (15%) aortic bifurcations developed PRS and were treated with adjunctive stenting. In this group, AB was 20 mm in 42%, IL/AB 1.4 in 56%, AB 20 mm associated with IL/AB 1.4 in 36% and aortic bifurcation calcification 25% in 67% of patients. The mean follow up was 36 months (range 6-65 months).Multivariate analysis identified AB 20 mm, IL/AB 1.4 and IL/AB 1.4 associated with calcification 25% as predictive factors for PRS (P .05, P .007 and P .015 respectively). Technical success and mid-term (36 months) clinical success were 100%. Conclusions: PRS of iliac endograft is a common pattern in the EVAR. AB 20 mm, ILs/AB 1.4 and aortic bifurcation calcification 25% associated with ILs/AB 1.4 are statistically correlated with PRS. Adjunctive stenting is a safe procedure and ensures patency in patients with PRS.

Reply to: Relationship of the lumbar lordosis angle to the abdominal aortic bifurcation and inferior vena cava confluence levels

Reply to: Relationship of the lumbar lordosis angle to the abdominal aortic bifurcation and inferior vena cava confluence levels

Extent II repair of thoracoabdominal aortic aneurysm secondary to chronic dissection.

Crawford extent II thoracoabdominal aortic aneurysm (TAAA) repairs generally involve replacing the full length of the thoracoabdominal aorta, from the left subclavian artery to the infrarenal abdominal aortic bifurcation, with a synthetic graft. Because of the extensive degree of aortic replacement involved, extent II repairs have been associated with the highest levels of risk for postoperative complications (1-6). To mitigate these complications, we routinely employ a multimodal approach to organ protection during these operations (7-9). To protect the spinal cord, we use mild passive hypothermia, cerebrospinal fluid drainage, left heart bypass (LHB), sequential cross-clamping, and selective reimplantation of intercostal or lumbar arteries (7,8,10,11). We intermittently deliver cold crystalloid solution to the kidneys to protect them from ischemic damage and prevent acute renal failure (12-14). We also deliver isothermic blood from the LHB circuit to the celiac axis and the superior mesenteric artery (SMA) to minimize ischemic times for the abdominal organs. To illustrate our technique for performing extent II TAAA repair, we present a video (Video 1) of such a procedure performed in a 55-year-old man with a symptomatic TAAA associated with chronic DeBakey type III aortic dissection (Figure 1). The patient had a history of hypertension, smoking, hepatitis B and C, and hepatic cirrhosis, as well as cocaine abuse, which is a risk factor for aortic dissection (15). At the time of his referral for surgical treatment, the patient was experiencing intermittent back pain. Preoperative imaging revealed a relatively normal-sized aortic arch with a dissection membrane starting just distal to the left subclavian artery. The true lumen was narrow, and the dissection extended into the celiac axis. The aneurysm measured 6 cm in diameter, and there was a large burden of thrombus in the infrarenal region. Open in a separate window Figure 1 Preoperative anatomy. Illustration and sections from a computed tomography scan showing the patient’s thoracoabdominal aortic aneurysm, which was associated with chronic aortic dissection. Note the narrow true lumen (double arrows) and the extension of the dissection into the celiac axis (single white arrow). The aneurysm begins to taper in the infrarenal region. Used with the permission of Baylor College of Medicine

A novel method for the generation of multi-block computational structured grids from medical imaging of arterial bifurcations

In this study a description of a new approach, for the generation of multi-block structured computational grids on patient-specific bifurcation geometries is presented. The structured grid generation technique is applied to data obtained by medical imaging examination, resulting in a surface conforming, high quality, multi-block structured grid of the branching geometry. As a case study application a patient specific abdominal aorta bifurcation is selected. For the evaluation of the grid produced by the novel method, a grid convergence study and a comparison between the grid produced by the method and unstructured grids produced by commercial meshing software are carried out.

Simulation of oscillatory flow in an aortic bifurcation using FVM and FEM: A comparative study of implementation strategies

AbstractCardiovascular diseases are one of the major causes of long‐term morbidity and mortality in human beings. The nearly epidemic increase in prevalence of such diseases poses a serious threat to public health and calls for efficient methods of diagnosis and treatment. Non‐invasive diagnostic procedures such as MRI are often used in this context; however, these are limited in terms of spatial and temporal resolution and do not provide information on time‐dependent pressures and wall shear stresses—key quantities considered to be partially responsible for the formation and development of related pathologies.The present study is concerned with the numerical simulation of oscillatory flow through the abdominal aortic bifurcation. Computational fluid dynamics simulation of oscillatory flow in a branched geometry at high Reynolds numbers poses considerable challenges. The present study reports a detailed comparison of simulations performed with a finite volume and a finite element method, two approaches with significant differences in their discretization strategy, treatment of boundary conditions and other numerical aspects. Both solvers were parallelized, using loop parallelization of the BiCGStab linear solver for the finite volume and domain decomposition based on the Schur complement method for the finite element technique. The experience gained with these two approaches for the solution of flow in a bifurcation forms the focus of this study. Although similar results were obtained for both methods, the computation time required for convergence was found to be significantly smaller for the finite element approach. Copyright © 2010 John Wiley & Sons, Ltd.

SU‐E‐T‐320: Micro CT Assessment of Magnetic Nanoparticle Retention in Arteries for Targeting Therapeutics

Purpose: Magnetic nanoparticles (MNP) may serve as a carrier for targeting therapeutics. In such application, it is crucial to achieve effective local retention of MNP under magnetic guidance. A micro CT imaging system of high spatial resolution was used to determine the volumetric retention of MNP subjected to magnetic guidance. Methods: Male Sprague Dawley rats were anesthetized to expose the bifurcation of abdominal aorta and iliac arteries. MNP (Chemicell) were injected intravenously while an NdFeB magnet (4.9 kG) was placed by the left iliac artery. Arteries were then ligated to preserve blood inside, removed, and fixed in paraformaldehyde solution prior to micro CT scanning. Micro CT was used to image the samples for evaluation of MNP retention in the artery. Results: Strong MNP attenuation was shown in the reconstructed images of micro CT from the experimental left‐iliac artery under magnetic influence; whereas the right arteries and aortas show little x‐ray attenuation. We further calculated the ratios of MNP volume over total sample volume to quantify the impact of external magnetic field on the MNP retention. The results show that the volume ratio of the left‐iliac artery group was much higher than that of the aorta/right artery groups. Conclusions: Our results suggest that local retention of MNP in the artery may be achieved with intravenous administration of MNP in vivo. In addition, micro CT analysis may be used for magnetic field optimization to improve local retention/distribution of MNP.

Calcification of the Aorta and Common Iliac Arteries

A 59-year-old man presented with paresthesia and weakness in both legs. Plain radiography of the abdomen showed marked calcification of the abdominal aorta, aortic bifurcation, and common iliac arteries. These findings were confirmed on CT of the lower abdomen.

High bifurcation of abdominal aorta upon horseshoe kidney at the level of upper L2 vertebral body: a rare case report

A high-positioned bifurcation of abdominal aorta upon a horseshoe kidney at the level of upper L2 vertebral body was detected during contrast enhanced abdominal computed tomography scan. The isthmus was clamped between the two elevated and extended common iliac arteries. The right renal artery arose from right common iliac artery supplying the superior and medium segments of right kidney. The left renal artery originated from right common iliac artery and branched off into three main arteries supplying the medium segment of right kidney, the inferior segment of right kidney and the lower half part of left kidney, respectively. The left accessory renal artery arose from abdominal aorta supplying the upper half part of left kidney. The inferior mesenteric artery arose from right common iliac artery. Lumbarization anomaly, scoliolosis, asymmetric pelvis and serious hydronephrosis of left kidney were also found. We describe this rare case of variations and discuss the possible embryonic development mechanism.

Evaluation of pelvic lymph node coverage of conventional radiotherapy fields based on bony landmarks in Chinese cervical cancer patients using CT simulation

To evaluate the pelvic lymph node coverage of conventional pelvic fields based on bony landmarks in Chinese patients with cervical cancer by using computed tomography (CT) simulation images to contour pelvic vessels as substitutes for lymph nodes location. A retrospective review of CT simulation images and conventional pelvic radiation planning data sets was performed in 100 patients with cervical cancer at the International Federation of Gynecology and Obstetrics (FIGO) Stage IIB to IIIB in our hospital. Pelvic arteries were contoured on CT simulation images, and the outlines of conventional pelvic fields were drawn as defined by the gynecologic oncology group (GOG) after hiding the contours. The distances between the following vessel contours and field borders were measured: D(1), the superior border of the anterior/posterior (AP) field and the bifurcation of abdominal aorta; D(2), the ipsilateral border of the AP field and the distal end of external iliac artery; and D(3), the anterior border of the lateral (LAT) field and the distal end of the external iliac artery. The distances were recorded as positive values if the measuring point was within the conventional pelvic fields, or they were recorded as negative values. Lymph nodes coverage was considered adequate when D(1)(0 mm, D(2)(17 mm or D(3)(7 mm. All patients had at least 1 inadequate margin, 97 patients (97.0%) had 2, and 22 patients (22.0%) had all the 3. On the AP field, 95 patients (95%) had the measuring point, the bifurcation of the abdominal aorta, out of the field (D(1)<0 mm), and all the patients had a distance less than 17.0 mm between the distal end of the external iliac artery and ipsilateral border (D(2)<17.0 mm). On the LAT field, 24 patients (24%) had a distance less than 7.0 mm between the distal end of the external iliac artery and anterior border (D(3)<7.0 mm). We observed that conventional pelvic fields based on bony landmarks provided inadequate coverage of pelvic lymph nodes in our patients with cervical cancer. CT simulation may be a feasible technique for planning pelvic fields optimally and individually.

Experience With the Endologix Powerlink Endograft in Endovascular Repair of Abdominal Aortic Aneurysms With Short and Angulated Necks

Endovascular aortic aneurysm repair (EVAR) for anatomically suitable abdominal aortic aneurysms (AAAs) has gained wide acceptance in the past decade, and EVAR for anatomically challenging or unsuitable AAAs such as short and angulated neck AAAs has become a hotly debated subject. The objective of this study is to summarize the unique experience of EVAR for short / angulated neck AAAs with Powerlink unibody bifurcated stent-graft. Data were retrospectively analyzed from 519 patients in our single unit from February 1999 to December 2007 who underwent EVAR using the Powerlink endograft, and had short or angulated necks. Short neck was defined as < or = 15 mm for the infrarenal neck length, and it was divided into 2 groups: Group A (short neck), 54 cases with the length 11 to 15 mm; and Group B (very short neck), 26 cases with the length < or = 10 mm. Angulated neck of 37 cases which was defined as > or = 60 degrees angulation between the longitudinal axis of infrarenal aorta and the aneurysm. The unique strategy of treating short / angulated neck AAAs is to build up the endoluminal exclusion system from the native aortic bifurcation to the renal artery level with suprarenal fixation. The Powerlink unibody bifurcated stent graft was implanted anatomically fixed on the aortic bifurcation and a long suprarenal cuff was built up to the renal arteries. A Palmaz stent can be used for proximal fixation and sealing enhancement in the most challenging necks. The follow-up imaging was performed at 1 month, 6 months, and yearly thereafter. The technical success rate was 97.4% (114/117). Intraoperative complications included 3 conversions due to delivery access problems, 6 proximal type I endoleaks, and 5 type II endoleaks. The 30-day mortality was 1.7% (2/117). The 2.6-year follow-up showed 4 (3.4%) proximal type I endoleaks, which were revised with proximal cuff and/or Palmaz stent. Limb occlusion occurred in 2 cases, and the total re-intervention rate was 5.3%. Three (2.6%) type II endoleaks were left in observation. There were 3 (2.6%) partial renal infarctions, no stent-graft distal migration, and no post-EVAR ruptures. Our experience demonstrates that building up the endoluminal exclusion system from the abdominal aortic bifurcation to the renal artery level using the Powerlink fully supported unibody bifurcated stent-graft with a long suprarenal cuff, and a Palmaz stent when needed, proved safe and effective in treating AAAs with short and angulated necks.

Multidetector CT Angiography Using a Dual-Head Power Injector and Bolus Tracking for the Diagnosis of Aortic Aneurysms at Reduced Contrast Material Dosage

To establish the utility of multidetector computed tomography (CT) angiography using dual-head power injector in the diagnosis of aortic diseases. In a prospective study, 151 patients with aortic diseases were examined by four-detector CT. Scanning was performed using bolus tracking technique. In all patients nonionic contrast was injected at the rate of 1.5 mL/sec. One hundred one patients were examined with dual-head power injector using 0.6 mL/kg contrast flushed by 30 mL of saline solution (group D). Fifty patients were examined with single-head power injector using 1.0 mL/kg contrast only (group S). We evaluated CT values at descending aorta, upper abdominal aorta, abdominal aortic bifurcation, and bilateral common femoral arteries. There were no statistically significant difference of CT values at descending aorta, upper abdominal aorta, abdominal aortic bifurcation, and right common femoral artery. At left common femoral artery, CT values in group D were higher than those in group S with statistically difference (P < .05). In group D, about 40% dose reduction was achieved without reducing image qualities. Multidetector CT angiography using dual-head power injector was valuable for the contrast dose reduction of aortic diseases.

Numerical study of a pulsatile flow in the abdominal aorta bifurcation

Numerical study of a pulsatile flow in the abdominal aorta bifurcation

Hydatid cyst of the abdominal aorta and common iliac arteries complicated by a false aneurysm: a case report

The rupture of hydatid cysts into the abdominal aorta is an unusual and serious complication of the hydatid disease. The authors describe a case of a 12-year-old girl with hydatid disease presenting as a retroperitoneal mass invading the wall of the abdominal aortic bifurcation and complicated by a false aneurysm. Difficulties of preoperative diagnosis and operative management were discussed, and the literature was reviewed.

Collagen versus gelatin-coated dacron versus stretch polytetrafluoroethylene in abdominal aortic bifurcation graft surgery: Results of a seven-year prospective, randomized multicenter trial

A prospective randomized multicenter trial was performed to compare knitted gelatin-coated Dacron bifurcation grafts, knitted collagen-coated Dacron grafts, and stretch polytetrafluoroethylene (PTFE) grafts. Between 1991 and 1998, 315 elective patients were randomized by age, gender, diabetes, runoff, indication (aneurysm, aortoiliac occlusive disease), and nicotine consumption at 3 centers of vascular surgery in Austria. The patients received gelatin-coated Dacron (GEL-D) grafts (n = 109), collagen-coated Dacron (COL-D) grafts (n = 100), or stretch PTFE grafts (n = 106). No intraoperative deaths occurred. The 30-day mortality was 3%. No difference was found between the 3 graft materials in long-term patency. The primary 5-year patency rates were 92% for GEL-D, 89% for COL-D, and 91% for stretch PTFE (P =.6001). The secondary 5-year patency rates also differed: 97% for GEL-D, 100% for COL-D, and 97% for stretch PTFE (P =.2062). Early occlusions were observed overall in 3% and late occlusions in 5% of patients. When both Dacron grafts were compared collectively with stretch PTFE, a difference was found in infection rate: Dacron 3% (6/209) versus PTFE 0% (0/106); P <.03. The bifurcation grafts of all 3 materials were comparable in primary and secondary patency rates, incidence of false aneurysms, and rate of perioperative complications. Graft infections were confined to the 2 Dacron grafts and did not occur in stretch PTFE grafts.

1212 三次元血管実形状測定システムの開発と計算流体力学シミュレーション

We studied the relationship between the blood flow and the atherosclerosis using Computational Fluid Dynamics (CFD). Atherosclerosis tends to grow at the bifurcation of abdominal aorta, particularly at the lateral side walls of the common iliac arteries. In general, the bifurcation of blood vessels has a sharp edge, and therefore the minute deformation and movement of the bifurcation are thought to have a large effect on the blood flow. In order to study the blood flow at the bifurcation using realistic CFD model, we developed a modeling system using micrometer thick slicing to reconstruct the 3-dimensional blood vessel configuration for CFD analysis.

The relationship between modified pulse wave transit time and cardiovascular changes in isoflurane anesthetized dogs.

To clarify the relationship between blood pressure and pulse wave transit time at the peripheral artery from the R wave of the electrocardiogram (m-PWTT), the effects of cardiovascular interventions on this relationship was evaluated. Ten mongrel dogs were anesthetized by isoflurane inhalation, and catheter tip pressure transducers were inserted into the ascending aorta and at the bifurcation of abdominal aorta to measure central and peripheral pulse wave arrival. Pulse wave arrival at the ascending aorta from the R wave represents pre-ejection period (PEP) and pulse wave arrival between the ascending aorta and bifurcation of aorta represents pulse wave transit time (PWTT), thus m-PWTT = PEP + PWTT. Hypertension was induced by the continuous infusion of dobutamine and phenylephrine, and hypotension was induced by deepening isoflurane anesthesia, acute blood loss and nitroglycerine infusion. The relationship between timing components (PWTT, PEP, and m-PWTT) and blood pressure was recorded and analyzed by using the least squares method. The relationship between timing components (PWTT, PEP and, m-PWTT) and blood pressure was significant and highly correlated. When the change in blood pressure was due to the myocardial contractility, such as after dobutamine infusion, the relationship between all timing components and blood pressure was consistent and negative. However, when the change in blood pressure was due to the vasoactive agents, such as phenylephrine, the relationship between timing components and blood pressure was dependent on the reflex change in PEP. Change in m-PWTT is a good parameter to predict blood pressure changes, although the absolute blood pressure value cannot be obtained.

Influence of vasoactive drugs on wall shear stress distribution in the abdominal aortic bifurcation: an in vitro study.

The present study compares the wall shear stress (rate) distribution in a compliant aortic bifurcation model under three different hemodynamic states: normal state, angiotensin II infusion state (vasoconstrictor), and isoproterenol infusion state (vasodilator). Using a Newtonian blood analog fluid, flow wave forms corresponding to each flow state were generated in an in vitro flow loop and a photographic flow visualization technique was employed to measure wall shear rate. The results indicate a zone of low mean wall shear stress and highly oscillatory shear stress on the outer (lateral) wall of the bifurcation. In this zone, the mean wall shear stress became negative for all three hemodynamic states indicating flow separation. However, the spatial extent of the flow separation zone was not affected significantly by the flow state. The study also revealed a large spatial variation of the phase angle between the hoop strain (circumferential strain due to radial artery expansion) and the wall shear stress, the two main mechanical stimuli acting on endothelial cells which affect their biology. In the zone of low mean wall shear stress on the outer wall, the two stimuli were more out of phase relative to the mother branch, whereas they were less out of phase (by about 50 degrees) on the inner wall (flow divider side). This phase angle was affected significantly by the flow state. For angiotensin II, the phase angle reached a maximum of 125 degrees in the low mean shear zone while the maximum was 94 degrees and 66 degrees for the normal and isoproterenol states, respectively. Our observation that large phase angles between the hoop strain and wall shear stress wave forms are localized in the low shear stress region where atherosclerotic disease occurs suggests the possible physiological relevance of this phase angle to the development of atherosclerosis.