Academic literature on the topic 'Distal Graft/Artery'
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Journal articles on the topic "Distal Graft/Artery"
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Redzek, Aleksandar, Bogoljub Mihajlovic, Pavle Kovacevic, Nada Cemerlic-Adjic, Katica Pavlovic, and Lazar Velicki. "Patency of internal thoracic artery and vein grafts according to revascularized coronary artery properties." Medical review 64, no. 3-4 (2011): 137–42. http://dx.doi.org/10.2298/mpns1104137r.
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Long-term results of surgical myocardial revascularization are determined by the quality of grafts and the progression of atherosclerosis in coronary arteries. The aim of the study was to evaluate the patency rate of internal thoracic artery and great saphenous vein grafts in relation to the hemodynamic properties of revascularized coronary artery. The patency of internal thoracic artery and great saphenous vein grafts was analyzed in relation to the degree of coronary stenosis estimated by angiography and the diameter of distal portion of coronary artery assessed intra-operatively. The long-term patency of great saphenous grafts depends on the distal coronary artery diameter but not on the degree of coronary artery stenosis. The patency of internal thoracic artery graft depends on the degree of co?ronary artery stenosis but not on the distal coronary artery diameter. The internal thoracic artery is the superior graft in coronary surgery, but the low patency rate in case of moderate coronary artery stenosis emphasizes the importance of selective approach.
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Kaisar, Jeremy, Aaron Chen, Mathew Cheung, Elias Kfoury, Carlos F. Bechara, and Peter H. Lin. "Comparison of propaten heparin-bonded vascular graft with distal anastomotic patch versus autogenous saphenous vein graft in tibial artery bypass." Vascular 26, no. 2 (August 23, 2017): 117–25. http://dx.doi.org/10.1177/1708538117717141.
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Introduction Heparin-bonded expanded polytetrafluoroethylene grafts (Propaten, WL Gore, Flagstaff, AZ, USA) have been shown to have superior patency compared to standard prosthetic grafts in leg bypass. This study analyzed the outcomes of Propaten grafts with distal anastomotic patch versus autogenous saphenous vein grafts in tibial artery bypass. Methods A retrospective analysis of prospective collected data was performed during a recent 15-year period. Sixty-two Propaten bypass grafts with distal anastomotic patch (Propaten group) were compared with 46 saphenous vein graft (vein group). Pertinent clinical variables including graft patency and limb salvage were analyzed. Results Both groups had similar clinical risk factors, bypass indications, and target vessel for tibial artery anastomoses. Decreased trends of operative time (196 ± 34 min vs. 287 ± 65 min, p = 0.07) and length of hospital stay (5.2 ± 2.3 days vs. 7.5 ± 3.6, p = 0.08) were noted in the Propaten group compared to the vein group. Similar primary patency rates were noted at four years between the Propaten and vein groups (85%, 71%, 64%, and 57%, vs. 87%, 78%, 67%, and 61% respectively; p = 0.97). Both groups had comparable secondary patency rates yearly in four years (the Propaten group: 84%, 76%, 74%, and 67%, respectively; the vein group: 88%, 79%, 76%, and 72%, respectively; p = 0.94). The limb salvage rates were equivalent between the Propaten and vein group at four years (84% vs. 92%, p = 0.89). Multivariate analysis showed active tobacco usage and poor run-off score as predictors for graft occlusion. Conclusions Propaten grafts with distal anastomotic patch have similar clinical outcomes compared to the saphenous vein graft in tibial artery bypass. Our data support the use of Propaten graft with distal anastomotic patch as a viable conduit of choice in patients undergoing tibial artery bypass.
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Kallakuri, S., E. Ascher, A. Hingorani, T. Jacob, and S. Salles-Cunha. "Hemodynamics of Infrapopliteal PTFE Bypasses and Adjunctive Arteriovenous Fistulas." Cardiovascular Surgery 11, no. 2 (April 2003): 125–29. http://dx.doi.org/10.1177/096721090301100204.
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Purpose Blood flow, pressure and peripheral resistance in patients with established polytetrafluoroethylene (PTFE) grafts and adjunctive arteriovenous fistulas (AVF) have rarely been investigated. To better elucidate the effects of this AVF, we obtained noninvasive measurements of hemodynamic variables in patients with infrapopliteal PTFE grafts and an AVF. Methods Systolic, mean and diastolic arm and toe pressures were measured with an oscillometric technique employed in automatic blood pressure monitors. Peak-systolic velocity, end-diastolic velocity and flow rates at the graft and recipient distal artery were measured with duplex ultrasound. Resistance for the leg and foot in peripheral resistance units (PRU) was estimated as mean arm pressure divided by graft flow rate and as mean toe pressure divided by distal artery flow rate respectively. We analyzed data from 21 patients. Toe pressures were measurable in 13 patients. Bypass graft inflow was at the external iliac artery in 11 patients, common femoral in six, common iliac in two and superficial femoral in two. The distal anastomosis was at the anterior tibial artery in 10 patients, peroneal in seven and posterior tibial in four patients. Results Graft systolic and diastolic velocities were 91 ± 46 (mean±sd) and 38 ± 31 (mean±sd) cm/s respectively. Toe systolic pressure averaged 81 ± 28 (mean±SD) mmHg with a corresponding toe/brachial index (TBI) of 0.53 ±0.18 (mean±SD). The ratio between arm mean pressure, 104 ± 20 (mean±SD) mmHg, and graft flow rate, 413 ± 290 (mean±sd) ml/min, yielded an estimated leg resistance of 0.32 ± 0.20 peripheral resistance units (PRU) (mean±sd). The ratio between mean toe pressure, 51 ± 21 (mean ± SD) mmHg, and distal artery flow rate, 37 ± 26 (mean±SD) ml/min, produced an estimated foot resistance averaging 1.66 ± 1.18 PRU (mean±sd). Conclusions Average graft flow rate was five times greater than flow reported for standard tibial bypasses. Although distal artery flow rate and graft peak systolic velocity were within reported normal ranges, mean toe pressure and toe-brachial index were below normal. Leg and foot resistances were decreased. These data suggest that bypasses with arteriovenous fistulas have increased flow, desirable for graft patency, but may affect distal perfusion pressure.
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Diaz-Abele, Julian, Emily Saganski, and Avinash Islur. "Use of Arterial Grafts in Hypothenar Hammer Syndrome: Application of Perforator Flap Anatomy." Plastic Surgery 28, no. 4 (June 17, 2020): 204–9. http://dx.doi.org/10.1177/2292550320933684.
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Background: Hypothenar hammer syndrome (HHS) is traditionally treated with venous bypass grafting, but controversy has arisen as arterial grafts have become more available. Methods: A retrospective review of all patients undergoing ulnar artery bypass grafting for HHS with an arterial graft from 2008 to 2017 was performed. We also review the literature for patency rates and discuss the scenarios that favor different graft choices. Results: Six patients were included in our series. Five had primary surgery and 1 had revision surgery for HHS. Five arterial grafts were from the deep inferior epigastric artery and 1 was from the lateral circumflex femoral artery. The proximal anastomotic site was the ulnar artery for all: n = 6. The distal anastomosis site was the palmar arch and common digital artery (CDA) of the ring/small finger and CDA of the middle/ring finger: n = 3; the palmar arch and the CDA of the ring/small finger: n = 3. All patients were symptom-free at follow-up and had a patent ulnar artery on Allen’s testing or angiogram. Conclusion: Patency rates of arterial grafts for HHS appear to be excellent and this small series and may offer an alternative to traditional venous grafts and end-to-end arterial anastomoses. We suggest using arterial perforator grafts from free flap donor sites. These have well-described anatomy, are easily harvested, and carry minimal donor site morbidity. Lateral circumflex femoral artery graft is favored in patients requiring a single distal anastomosis, who have a ventral hernia, or who are obese. Deep inferior epigastric artery graft is preferred when multiple distal targets or versatile configurations are needed, in thin patients, or in female patients.
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Nossek, Erez, Peter D. Costantino, David J. Chalif, Rafael A. Ortiz, Amir R. Dehdashti, and David J. Langer. "Forearm Cephalic Vein Graft for Short, “Middle”-Flow, Internal Maxillary Artery to Middle Cerebral Artery Bypass." Operative Neurosurgery 12, no. 2 (September 23, 2015): 99–105. http://dx.doi.org/10.1227/neu.0000000000001027.
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Abstract BACKGROUND The cervical carotid system has been used as a source of donor vessels for radial artery or saphenous vein grafts in cerebral bypass. Recently, internal maxillary artery to middle cerebral artery bypass has been described as an alternative, with reduction of graft length potentially correlating with improved patency. OBJECTIVE To describe our experience using the forearm cephalic vein grafts for short segment internal maxillary artery to middle cerebral artery bypasses. METHODS All vein grafts were harvested from the volar forearm between the proximal cubital fossa where the median cubital vein is confluent with the cephalic vein and the distal wrist. RESULTS Six patients were treated with internal maxillary artery to middle cerebral artery bypass. In 4, the cephalic vein was used. Postoperative angiography demonstrated good filling of the grafts with robust distal flow. There were no upper extremity vascular complications. All but 1 patient (mortality) tolerated the procedure well. The other 3 patients returned to their neurological baseline with no new neurological deficit during follow-up. CONCLUSION The internal maxillary artery to middle cerebral artery “middle” flow bypass allows for shorter graft length with both the proximal and distal anastomoses within the same microsurgical field. These unique variable flow grafts represent an ideal opportunity for use of the cephalic vein of the forearm, which is more easily harvested than the wider saphenous vein graft and which has good match size to the M1/M2 segments of the middle cerebral artery. The vessel wall is supple, which facilitates handling during anastomosis. There is lower morbidity potential than utilization of the radial artery. Going forward, the cephalic vein will be our preferred choice for external carotid-internal carotid transplanted conduit bypass.
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Arbağ, Hamdi, Mehmet Erkan Ustun, Mustafa Buyukmumcu, Aynur Emine Cicekcibasi, and Cagatay Han Ulku. "A modified technique to bypass the maxillary artery to supraclinoid internal carotid artery by using radial artery graft: an anatomical study." Journal of Laryngology & Otology 119, no. 7 (July 2005): 519–23. http://dx.doi.org/10.1258/0022215054352153.
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Objective: This study aims to examine the use of a radial artery graft for bypass of the maxillary artery (MA) to the supraclinoid internal carotid artery (ICA) in treating ICA occlusions.Study design and setting: This method was carried out on five adult cadaver sides. The MA was reached 1–2 cm inferior to the crista infratemporalis, following a frontotemporal craniotomy and a zygomatic arch osteotomy. Extradurally 2–3 cm lateral to the foramen rotundum, a hole was drilled in the sphenoid bone with a 4 mm tipped drill. A radial artery graft was passed through the hole to the inside of the dura. Before giving the infraorbital artery branch, the MA was dissected from the surrounding tissue and transected. The proximal end of the graft was anastomosed end-to-end with the MA and the distal end of the graft end-to-side with the supraclinoid ICA.Results: The mean calibre of the MA was 2.6 ± 0.3 mm. The mean calibre of the proximal end of the radial artery graft was 2.5 ± 0.25 mm and the distal end was 2.35 ± 0.2 mm. The mean length of the radial artery graft was 4.0 ± 0.5cm.Conclusion: This study suggested that the cases with ICA occlusion, which require high blood flow, may be treated as an alternative to current bypass methods requiring long vein grafts.
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Shirasu, Takuro, Atsushi Akai, Manabu Motoki, and Masaaki Kato. "Clampless In-Situ Immobilized Branching (CLIMB) to Reconstruct the Internal Iliac Artery." Life 12, no. 11 (November 18, 2022): 1928. http://dx.doi.org/10.3390/life12111928.
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Background: Surgical reconstruction of the internal iliac artery (IIA) or its branches is sometimes demanding because of difficulty in distal clamping and suturing in the narrow pelvic space. Here we present a hybrid technique of ClampLess In-situ imMobilized Branching (CLIMB) to reconstruct IIA. Methods: in the CLIMB technique, an 8 mm artificial graft is sutured onto the surface of the common iliac artery (CIA) without clamping. Following puncture of the CIA wall, stent grafts are bridged from IIA to the graft. Finally, the graft is sutured to the ipsilateral external iliac artery (EIA). Concomitant endovascular aneurysm repair or IIA branch embolization can also be performed. We applied this technique to the patients unsuited for other IIA reconstruction. Results: eleven patients underwent the current technique. All but one patient underwent contralateral IIA interruption. Seven patients had a history of aorto-iliac repair before the index surgery. Iliac extender, internal iliac component, Viabahn VBX or Fluency covered stent were used for bridging the graft. Simultaneous IIA branch embolization was performed in 2 patients. Distal landing zones were IIA in 7 grafts, superior gluteal artery in 4 grafts and inferior gluteal artery (IGA) in 1 graft. Technical success was achieved in all cases. No patient complained of buttock claudication or other ischemic symptoms on the treatment side. During a mean follow-up period of 38 months, 11 out of 12 grafts were patent without any related endoleak. One IGA graft occluded at 56 months after surgery. Conclusions: the CLIMB technique is a viable alternative to preserve IIA with an acceptable mid-term durability.
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Kobayashi, Junjiro, Osamu Tagusari, Ko Bando, Kazuo Niwaya, Hiroyuki Nakajima, Michiko Ishida, Satsuki Fukushima, and Soichiro Kitamura. "Total Arterial Off-Pump Coronary Revascularization with Only Internal Thoracic Artery and Composite Radial Artery Grafts." Heart Surgery Forum 6, no. 1 (February 2, 2005): 30. http://dx.doi.org/10.1532/hsf.969.
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<P>Objective: Total arterial off-pump coronary artery bypass (OPCAB) grafting with only internal thoracic artery (ITA) and composite radial artery (RA) grafts has been applied extensively to avoid cerebral complications and late vein graft failure. We evaluated the initial experience with this method by clinical and angiographic study. </P><P>Methods: Between April 2000 and May 2002, 257 patients underwent OPCAB grafting with this technique. The range of ages at operation was 42 to 86 years (mean, 66.1 � 8.6 years). On average, 3.28 � 0.86 grafts per patient were completed. More than 4 distal anastomoses were performed in 88 patients (34%). For coronary revascularization, 289 ITA and 555 RA grafts were used. The RA was used as a Y graft in 211 patients, as an I graft (for ITA extension) in 52 patients, and as a K graft (the side of the RA attached to the side of the left ITA) in 28 patients. Sequential bypass grafting was performed with 190 RA and 7 ITA grafts. The sites of distal anastomoses were 256 left anterior descending arteries (30%), 236 posterolateral branches (28%), 144 posterior descending arteries (17%), 106 diagonal branches (13%), 82 obtuse marginal branches (10%), and 19 right coronary arteries (2%). </P><P>Results: There were 1 operative death (0.4%) due to cerebral hemorrhage and 2 episodes of stroke (0.8%) during postoperative angiography. There were no clinical underperfusion syndromes or new intra-aortic balloon pump insertions. Perioperative myocardial infarction occurred in 12 patients (4.7%), sternal dehiscence in 5 (1.9%), and early coronary intervention in 4 (1.6%). There was no deep wound infection, reexploration for bleeding, or hand ischemia. The actuarial survival rate and the cardiac event-free rate at 2 years were 98.6% � 2.4% and 94.2% � 0.8%, respectively. Early postoperative angiography revealed a 97.8% (264/270) graft patency of ITAs and 97.9% (512/523) graft patency of RAs in 238 patients. Flow competition of the RA graft was recognized in 22 patients and, as indicated by follow-up angiographic study, did not cause late graft occlusion. </P><P>Conclusions: OPCAB grafting with ITAs and composite RAs provides excellent early and intermediate clinical results and graft patency.</P>
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SAITOH, S., and Y. NAKATSUCHI. "Long-Term Results of Vein Grafts Interposed in Arterial Defects Using the Telescoping Anastomotic Technique and Fibrin Glue." Journal of Hand Surgery 21, no. 1 (February 1996): 47–52. http://dx.doi.org/10.1016/s0266-7681(96)80011-8.
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Fibrin glue has been applied in the anastomosis of vein grafts placed in rat femoral arteries using the telescoping technique at both ends of the graft. 34 out of 35 grafts which were patent 1 to 3 weeks post-operatively were kept for 3 months to assess the long-term patency, and the effect of the glue on the diameters of the graft and femoral artery. All 34 grafts were patent 3 months post-operatively. Excessive enlargement of the graft diameter was alleviated by the fibrin glue without affecting the diameter of the femoral artery. The diameter at the proximal anastomosis was 66% and that at the distal anastomosis was 87% of the diameter of the femoral artery.
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O'Brien, Thomas, Liam Morris, Michael Walsh, and Tim McGloughlin. "That Hemodynamics and Not Material Mismatch is of Primary Concern in Bypass Graft Failure: An Experimental Argument." Journal of Biomechanical Engineering 127, no. 5 (April 28, 2005): 881–86. http://dx.doi.org/10.1115/1.1992532.
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The long term patency of end-to-side peripheral artery bypasses are low due to failure of the graft generally at the distal end of the bypass. Both material mismatch between the graft and the host artery and junction hemodynamics are cited as being major factors in disease formation at the junction. This study uses experimental methods to investigate the major differences in fluid dynamics and wall mechanics at the proximal and distal ends for rigid and compliant bypass grafts. Injection moulding was used to produce idealized transparent and compliant models of the graft/artery junction configuration. An ePTFE graft was then used to stiffen one of the models. These models were then investigated using two-dimensional video extensometry and one-dimensional laser Doppler anemometry to determine the junction deformations and fluid velocity profiles for the rigid and complaint graft anastomotic junctions. Junction strains were evaluated and generally found to be under 5% with a peak stain measured in the stiff graft model junction of 8.3% at 100mmHg applied pressure. Hemodynamic results were found to yield up to 40% difference in fluid velocities for the stiff/compliant comparison but up to 80% for the proximal/distal end comparisons. Similar strain conditions were assumed for the proximal and distal models while significant differences were noted in their associated hemodynamic changes. In contrasting the fluid dynamics and wall mechanics for the proximal and distal anastomoses, it is evident from the results of this study, that junction hemodynamics are the more variable factor.
Books on the topic "Distal Graft/Artery"
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Walsh, Michael Thomas. Design of a distal graft/artery junction to increase the patency rates of peripheral bypass surgery. 2001.
Find full textBook chapters on the topic "Distal Graft/Artery"
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Kabinejadian, F., L. P. Chua, D. N. Ghista, and Y. S. Tan. "A New Coronary Artery Bypass Graft (CABG) Distal Anastomosis Design." In IFMBE Proceedings, 491–94. Berlin, Heidelberg: Springer Berlin Heidelberg, 2009. http://dx.doi.org/10.1007/978-3-642-03882-2_130.
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Kitamura, Siro, Junichi Ooida, Yoshinori Inoue, and Takehisa Iwai. "Numerical Simulations of Blood Flow at the Distal Anastomosis between a Prosthetic Graft and a Native Popliteal Artery." In Computational Fluid Dynamics 2002, 185–90. Berlin, Heidelberg: Springer Berlin Heidelberg, 2003. http://dx.doi.org/10.1007/978-3-642-59334-5_25.
Full textConference papers on the topic "Distal Graft/Artery"
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Ballyk, Peter D., Matadial Ojha, and Colin Walsh. "Vein Cuffs May Improve Anastomotic Patency by Reducing Suture-Line Intramural Stresses." In ASME 1997 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1997. http://dx.doi.org/10.1115/imece1997-0258.
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Abstract Intimal hyperplasia (IH) is an important complication of arterial bypass surgery which can ultimately lead to graft failure. The pathogenesis of IH involves the migration of smooth muscle cells from the media to the intima where they proliferate and secrete extracellular matrix. This results in a thickened vessel wall which may cause stenosis and/or thrombosis of the distal graft-artery junction. It has been shown that IH is a more significant problem in stiff synthetic grafts than in more compliant vein grafts (Bassiouny et al., 1992), and that synthetic grafts have a higher failure rate (Waiden et al., 1980). Consequently, autogenous vein (or artery) grafts are used clinically whenever possible. In cases where autogenous grafts are not long enough or not available (for e.g. if they have already been harvested or have been obliterated by disease), a vein cuff interposed between the distal end of a synthetic graft and the host artery can improve long term patency by reducing distal anastomotic IH (Miller et al., 1984; Suggs et al., 1988).
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Ballyk, Peter D., Matadial Ojha, and Colin Walsh. "Comparing the Influence of Graft Angle on Peri-Anastomotic Wall and Fluid Mechanics." In ASME 1997 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1997. http://dx.doi.org/10.1115/imece1997-0248.
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Abstract Distal anastomotic intimal hyperplasia (DAIH) can lead to outflow stenosis of vascular bypass grafts. In end-to-side graft-artery anastomoses, two separate regions of DAIH have been identified: (i) the suture line and (ii) the floor of the anastomosis across from the suture line (Bassiouny et al., 1992). Suture-line intimal thickening seems to be associated with post-surgical healing and influenced by graft-artery compliance mismatch (Trubel et al., 1994), while floor hyperplasia appears to be linked to fluid mechanical phenomena, such as temporal variations in wall shear stress (Ojha, 1994).
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Qiao, Aike, and Teruo Matsuzawa. "Hemodynamics of End-to-End Femoral Bypass Graft." In ASME/JSME 2004 Pressure Vessels and Piping Conference. ASMEDC, 2004. http://dx.doi.org/10.1115/pvp2004-3125.
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In the conventional femoral bypassing operation, side-to-end (STE) configuration at the proximal anastomosis and end-to-side (ETS) configuration at the distal anastomosis are usually employed. With these configurations, blood flow from the bypass graft at the distal anastomosis strongly strikes on the floor of the host artery opposite the anastomosis. This will result in the violent variations of hemodynamics in the vicinity of distal anastomosis, and further bring about anastomotic intimal hyperplasia (IH) and restenosis. Consequently, the effectiveness of bypassing surgery is compromised in the medium and long term by the development of these pathological changes. It is widely accepted that hemodynamics is close correlated to the geometry configuration of femoral bypass graft. It is verified that flow field at the distal junction has more influences on the pathogenesis and its aftereffects are more critical because the development of IH and restenosis is prone to occur in that region and endangers the patency of subsequent arteries. Nonuniform hemodynamics, characterized by nonuniform Wall Shear Stress (WSS) and large sustained Wall Shear Stress Gradients (WSSG), is also commonly considered as one of the most important causes among the numerous complex physiological and biomechanical factors. Purpose of the present study is to investigate an alternative geometry configuration to improve the hemodynamics at the vicinity of distal anastomosis and increase the medium and long term patency rate of bypass graft surgery. According to the clinical observation, the stenosed host artery may become fully stenosed after bypassing surgery and the bypass graft is the only way to restore normal blood flow to ischemic limbs. The authors presented a modified bypassing configuration with an end-to-end (ETE) conjunction at the distal anastomosis. In this new model, the proximal graft is arc-shaped with STE junction and the distal graft is sinusoid-shaped with ETE junction. The bypass graft is of the same diameter of d = 8mm as the host femoral artery, so the graft can be connected with the femoral artery smoothly at the distal junction. The polytetrafluoroethylene (PTFE) is employed as the graft material. The blood is assumed to be an isotropic, homogeneous, incompressible, Newtonian continuum having a constant density and viscosity. The vessel walls are assumed to be rigid and impermeable. The blood flow is assumed to be physiologically pulsatile laminar flow. The mean Reynolds number is Rem = 204.7, Womersley number is α = 6.14. The boundary conditions include: the physiologically pulsatile entrance velocities at the inlet section, the no-slip boundary condition on the wall, the symmetric condition in the centerline plane of femoral and graft, and the outlet pressure condition with a reference pressure P = 0 at the exit section. Three-dimensional idealized femoral bypass graft model is developed and discretized. The blood flow in the proposed model is simulated with computational fluid dynamics (CFD) method using the finite element analysis. The temporal and spatial distributions of hemodynamics such as flow patterns and WSS in the vicinity of distal anastomosis during the cardiac cycle were analyzed. Especially, the emphasis here was on the analysis of WSS, the temporal and spatial WSSG and the Oscillating Shear Index (OSI). The simulation results indicated that: (1) the ETE model is featured with small secondary flow; (2) WSS at the distal anastomosis is uniform, WSSG is small, and OSI of the ETE model has not much changes compared with ETS graft. The present study showed that the femoral bypassing configuration with ETE bypass graft was of more favorable hemodynamics, and it could consequently improve the flow conditions and decrease the probability of IH and restenosis. With the consideration of that numerical simulation was proved to be of great help and guidance meaning for the biofluidmechanics research and the biomedical engineering, the results of the present study can be applied to medical device design and clinical treatment planning in addition to the application of computational methods to cardiovascular disease research.
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Anayiotos, Andreas S., Pedro D. Pedroso, Ramakrishna Venugopalan, Evangelos Eleftheriou, and Maria A. Advincula. "Flow Evaluation of a Compliant Coronary Artery Anastomosis Model." In ASME 2001 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2001. http://dx.doi.org/10.1115/imece2001/bed-23123.
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Abstract Coronary artery bypass grafting (CABG) is a common surgical procedure for coronary artery diseases or severe stenosis of the coronary arteries. It makes use of a peripheral vein (usually the saphenous vein of the leg) to form a conduit between the aorta and the coronary artery distal to the obstructive lesion. It is rapidly becoming the treatment of choice in cases where the vessel is more than 70% occluded or when angioplasty is not possible. However, a significant number of grafts subsequently fail due to acute thrombosis in the early post-operative period or to restenosis within months or years. Intimal thickening in the CABG anastomosis has been implicated as the major cause of restenosis and long-term graft failure. Several studies point to the interplay between non-uniform hemodynamics (including disturbed flows and recirculation zones), wall shear stress, and long particle residence time as possible etiologies. An important feature of the anastomosis geometry, is a bulge that forms at the veno-arterial junction. This sinus forms as a result of the stretching of the thin venous wall when the graft is exposed to aortic pressure conditions. The resultant sinus, and the impedance mismatch of the vein-artery connection, contribute to a complicated region of highly disturbed flow at the divider and may have a primary role in restenosis and final failure of the graft.
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Ben-Hamo, Nati, Simcha Milo, Oded Gottlieb, and Gad Hetsroni. "Characterization of Venous Graft Wall Motion as an Indicator of Distal Anastomosis Quality in Coronary Artery By-Pass Surgery." In ASME 2008 9th Biennial Conference on Engineering Systems Design and Analysis. ASMEDC, 2008. http://dx.doi.org/10.1115/esda2008-59177.
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An essential parameter in assessing anastomosis quality and graft patency is associated with the graft flow rate measured at the end of a by-pass surgery. To date, no objective method to determine the quality of the anastomosis graft and to obtain graft flow rate has been endorsed by the medical community. This paper describes a non-invasive technique for measuring the integrity of a venal graft in a coronary artery bypass upon conclusion of surgery. An in vitro laboratory setup was designed to illustrate the dynamic conditions in a coronary by-pass graft. Experiments were conducted for a graft with constant flow and for a graft with pulsatile flow. The behavior of the vein wall was examined when both ends of the graft were open to flow, and also when one end of the graft was occluded. The dynamic behavior of the graft was found to change as a function of graft patency and venal pressure. A correlation was confirmed between the oscillation frequency at the graft mid span and the change in pressure at vein exit.
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Campbell, Triona, Reena Cole, Mark Davies, and Michael O’Donnell. "Stress Distributions Along the Inner Wall of the Femoropopliteal Bypass Graft Anastomoses." In ASME 2004 International Mechanical Engineering Congress and Exposition. ASMEDC, 2004. http://dx.doi.org/10.1115/imece2004-59395.
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The distal junction of a femoral or femoropopliteal artery bypass graft has a predilection for failure due to restenosis. However neither the initiation nor proliferation process of atherosclerotic plaque is completely understood. Presently it is hypothesized that the process of atherosclerosis initiates as a result of damage or ‘insult’ to the endothelium. The cause of this initial damage is unknown, although it is widely believed that wall shear stresses are a contributing factor. The primary cause of plaque proliferation has not yet been identified, however it is our belief that intramural pressure plays a significant role. In this study numerical models of the proximal and distal junctions were used to determine both the location and magnitude of the stresses caused by intramural pressure. The simulated artery bypass graft was examined under both static and dynamic conditions.
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Cole, Reena, Triona M. Campbell, and Mark R. D. Davies. "Pressure Induced Stresses and Strains in a Simulated Femoral Artery Bypass Graft Junction." In ASME 2003 International Mechanical Engineering Congress and Exposition. ASMEDC, 2003. http://dx.doi.org/10.1115/imece2003-42947.
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It has been clinically proven that vascular reconstructions tend to restenose within a relatively short period of time. Intimal hyperplasia and smooth muscle proliferation appear to be promoted by the altered intramural stress distributions at the distal anastomosis of the artery-graft junction. This paper examines the pressure induced stresses and strains in a simulated artery and bypass graft junction. Numerical and experimental methods were used to determine both the magnitude and location of the stresses and strains. A Finite Element package and silicon models were used for the in vitro analysis. Initial numerical analysis involved the modeling of a cylinder with homogenous material properties, followed by the modeling of a homogenous graft artery junction under static pressures. These experimental results were then used to validate the numerical model.
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Keynton, Robert S., Mary M. Evancho, Rick L. Sims, Nancy V. Rodway, and Stanley E. Rittgers. "Do Temporal Wall Shear Stress Gradients Promote the Development of Intimal Hyperplasia Within Vascular Bypass Grafts?" In ASME 1997 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1997. http://dx.doi.org/10.1115/imece1997-0247.
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Abstract The purpose of this paper is to determine the relationship between the temporal wall shear stress gradient and the development of intimal hyperplasia (IH) within an in vivo animal model of the distal anastomoses of vascular bypass grafts. Tapered Teflon® grafts were placed in the common carotid arteries of adult, mongrel dogs with 30° end-to-side proximal and distal anastomoses and a graft-to-artery diameter ratio of either 1:1 or 1:1.5. Simultaneous axial velocity measurements were obtained using a specially designed 20-MHz ultrasonic wall shear rate transducer. Peak and oscillatory temporal WSSGs were found, at best, to only weakly correlate with IH (r = 0.20 and r = 0.27, respectively). The results from this study suggest that the temporal WSSG parameter, by itself, does not promote the development of IH.
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Folts, J. D. "A MODEL OF ACUTE PLATELET THROMBUS FORMATION IN STENOSED CORONARY AND CAROTID ARTERIES." In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1643712.
Full textAbstract:
There is currently a great deal of interest in the diagnosis and treatment of unstable angina and silent ischemia.Many feel that these syndromes are due, in part, to periodic accumulation of platelet thrombi which subsequently embolize.In addition, anti-piatelet therapy is also considered necessary for patients after coronary artery bypass grafts (CABG'S), balloon angioplasty, and thrombolysis. Currently the two antiplatelet agents most commonly prescribed for the patient conditions mentioned above are aspirin (ASA), alone or in combination with dipyridamole (Dip). ASA reduces cardiac events in patients with unstable angina, and prolongs CABG graft patency. The addition of Dip to ASA therapy is very confusing since most studies done compared ASA + Dip to placebo. In several studies however,when an ASA group was compared to an ASA + Dip group there was no significant difference.We have developed and will describe ananimal model of coronary artery stenosis in the dog and the pig, or carotid arterystenosis in the monkey and the rabbit, with intimal damage, that simulates some ofthe conditions that exist in patients with coronary or carotid artery disease. The artery to be studied is dissected outand blood flow is continuously measured with an electromagnetic flowmeter probe. As acute platelet thrombus formation (APTF) developes in the stenosed lumen, the blood flow declines to low levels, producing ischemia until the thrombus emobolizesdistally resulting in abrupt restoration of blood flow. These cyclical flow reductions (CFR's), when they occur in the coronaries, produce ECG changes identical to those observed in patients with silent ischemia and unstable angina. They also produce significant transient regional dyskinesis of the ventricular wall, which resolves when blood flow is restored. Histologic examination of myocardial tissue in the bed distal to the stenosis shows focal areas of ischemic change presumably caused by the embolized platelet emboli.We have examined factors which exacerbate the size and frequency of these CFR"ssuch as; IV infusion of epinephrine (E) 0.4 μg/kg/min for 15 min, ventilating the animals with cigarette smoke, infusing nicotine IV, or placing chewing tobacco under the tongue.We have examined four groups of agentswhich prevent APTF in our model.1. Antiplatelet agents including ASA, indomethacin, ibuprofen and several other NSAI agentsas well as several experimental thromboxane synthetase inhibitors. These agents all block the production of TXA2and inhibit APTF in our model. Unfortunately the IV infusion of E reinstates APTtemporarily (by another biochemical pathway) until the E is metabolized. High (2-4 mg/kg) doses of Dip, alone or with sub threshold dose of ASA does nothing to I APTF.However,0.6mg/kg of chi orpromaz i ne abolishes APTF in all four species and protects agents renewal of APTF by E.2. Dietary Substances In our model, caffeine 10 mg/kg, or the extract from two garlic cloves, or enough ethanol to achieve a blood alcohol level of 0.07 mg% all significantly inhibit or abolish APTF in our model.3. Metabolic Inhibitors POCA, an oral hypoglycemic agent, which inhibits mitochondrial beta oxidation of fatty acids also inhibits APTF in our model possibly by reducing ATP production in the platelet.4. We have studied a monoclonal antibody(developed by Dr. Barry Coller) to the platelet I Ib�I I la glycoprotein receptor where fibrinogen binds platelets into aggregates and ultimately leads to APTF. This antibody 0.3 mg/kg/completely inhibits APTF, and also strongly inhibits in vitro platelet aggregation in response to either ADP or collagen given alone or each combined with E. This antibody is the most potent inhibitor of APTF that we have studied.
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Moore, James E., Joel L. Berry, Emil Manoach, and Alexander Rachev. "Fluid and Solid Mechanics in Stented Arteries." In ASME 1999 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1999. http://dx.doi.org/10.1115/imece1999-0382.
Full textAbstract:
Abstract Vascular stents are being used in increasing numbers to correct arterial flow limiting disorders. Although data exist on the in vivo performance of these devices, comparatively little is known about how these devices affect the arterial mechanical environment. The long-term success of stenting is very likely affected by the blood flow patterns and artery wall stresses that follow stent placement. This study was undertaken to identify the mechanical environment in stented arteries and to propose a stent design that minimizes the “mechanical trauma” of stent implantation. A series of pulsatile flow visualization experiments were performed with a Johnson & Johnson Palmaz/Schatz stent inserted in a straight compliant tube. A flow loop was constructed that was capable of applying a physiologic pulsatile flow indicative of conditions in the femoral or coronary arteries. The results showed that this stent design creates complex flow patterns including large-scale vortices, and that these patterns are caused by the compliance mismatch between the stented vessel and adjacent unstented vessel. The compliance mismatch also would be expected to create abnormal stress concentrations in the artery wall near the ends of the stent. A simplified model of an artery was constructed to estimate the stress in the artery wall. The stent/artery structure was assumed to be an axisymmetric thin shell made of a linear elastic, orthotropic material that undergoes small deformations. The stent diameter was assumed to be equal to the artery systolic diameter. The stresses were estimated under diastolic pressure, when the deflection of the artery due to the presence of the stent is greatest. It was found that the circumferential and axial stresses at the ends of the stent were 2 to 3 times higher than the stress far from the stent. Based on these mechanical studies, a new stent design was proposed that provides a smooth transition in compliance at the proximal and distal ends of the tube. Flow visualization studies with this new stent indicate that the flow disturbances are greatly reduced with this new design. The transition zone was incorporated into the shell model to estimate the artery wall stresses induced by this new model. It was found that the stress concentration was reduced by as much as 36% from the rigid stent value. These studies demonstrate the potential complexity of flow in stented arteries and provide some recommendations for optimizing stent design from a biomechanical point of view. This work was supported in part by a Linkage Grant from NATO.