Vascular Prosthesis Implantation Research Articles

Integral and Local Methods for the Evaluation of the Hemostasiological Profile in Sheep at Various Stages of Implantation of a Biodegradable Vascular Graft.

The object of the study was the whole blood of sheep collected at the stage of premedication, during the intraoperative period, and in the early postoperative period. Thromboelastography was used to assess the kinetics of clot formation and changes in its viscoelastic properties in whole blood samples. The thrombin generation test was performed in platelet-rich plasma (PRP) and platelet-poor plasma (PPP) with the assessment of quantitative and temporal parameters. The platelet factor 4 concentration in PRP and PPP was measured by the enzyme immunoassay. The functional activity of platelets in PPP was assessed with inductors and without additional stimulation. Prothrombin complex activity, APTT values, thrombin time, fibrinogen concentration, antithrombin III and protein C activity, soluble fibrin monomer complexes, and fibrinolysis were determined in blood plasma. Multidirectional changes in the hemostasiological profile at various stages of vascular prosthesis implantation have been revealed. On the one hand, it is an increased prothrombogenic status, on the other hand, it is the development of hypocoagulation. Shortening of the R (blood coagulation time) and K (clot formation time) intervals and an increase in the angle parameter and maximum amplitude on the thromboelastogram in all the studied periods relative to the reference values, a significant increase in platelet factor 4 in PRP and increased platelet aggregation testified in favor of hypercoagulation. However, the quantitative parameters of the thrombin generation test and a number of coagulogram indicators pointed to hypocoagulation in the intraoperative and early postoperative periods. The comparative analysis of local tests characterizing the state of hemostasis and indicators of integral methods demonstrated the advantages of the latter in assessing thrombotic risks during implantation of vascular grafts. Local tests are not sufficient to assess the dynamics of the coagulation process in real time and are not always sensitive to hypercoagulation. The use of integral methods will help to fill these gaps, make a timely diagnosis of hypercoagulability and minimize the risks associated with the implantation of vascular grafts in future.

Analysis of Sexual Disorders in Men with Infrarenal Abdominal Aortic Aneurysm Treated by Stent-Graft or Prosthesis Implantation-A Pilot Study.

Background and objectives: Patients with obstruction or stenosis of the aorta and iliac arteries or with aortic aneurysm, often co-existing with iliac artery aneurysms, suffer from sexual disorders because of insufficient perfusion to the pelvic organs and penis. This is often the cause of visits to a medical doctor’s office with reports of a difficult life situation and a problem with the satisfactory completion of sexual intercourse. A low percentage of vascular surgeons or angiologists are prepared to talk about issues related to the hereditary sphere with a patient who qualifies for the treatment of Leriche syndrome or abdominal aortic aneurysm. The aim of this study was to analyze sexual disorders in men with infrarenal abdominal aortic aneurysm treated by stent-graft or prosthesis implantation. Material and methods, Outcomes: 38 patients who completed the IIEF-5 (International Index of Erectile for Men) questionnaire are presented. Initially, 146 qualified for the study after meeting the study inclusion criteria for surgery (Group 1) or for endovascular treatment of abdominal aortic aneurysm (Group 2). Results: In the study, no negative impact of smoking was found; however, over 95% of respondents had been smoking for many years in both groups. Patients who qualified for vascular prosthesis implantation were subject to a more advanced atherosclerotic process involving the aorta and iliac arteries. Patients who qualified for stent-graft implantation were twice as often treated for coronary vessel stenosis. In Group 1, the percentage differences, as shown by questions 1 and 5, were statistically significant (58, i.e., 25%, and 40, i.e., 29%). Conclusions: Education should target medical personnel in terms of conversations with patients, as well as men who are directly affected by this problem, although their partners and families should not be neglected in these activities. The ability to communicate properly allows for an open dialogue on issues that the patient finds difficult, particularly in the field of sexology.

Surgical Treatment Methods of Post-coarctation Aneurysms of Aorta

Introduction. Aortal coarctation is one of the most studied conditions of heart congenital defects, which comprises from 7% to 10% of all congenital heart defects.
 During many years the various treatment strategies were used. Open surgical reconstructive intervention was first de-scribed in 1945, and this was, as a rule, resection of aortal narrowed portion.
 Although the treatment of coarctation is usually successful in a short-term perspective, there is a well-known fact of de-velopment of complications at the later stages, especially after surgical reconstruction, such as post-coarctation aneurysms.
 Objective. To analyze surgical methods of correction of coarctation.
 Materials and methods.in the National Amosov Institute of Cardiovascular Surgery of the National Academy of Medical Sciences of Ukraine during the period 1960–2017, 4245 patients were operated with native coarctation of aorta.
 Selective patients’ choice for this work was restricted only by such cases of aneurysm of descending aorta, for which the data were reliable. Considering the above, we will be limited by the period of observation, starting from 1995.
 Totally, 91 cases with aneurysm of descending aorta were included in this work, 85 (93.4%) of patients were re-operated, 6 (6.6%) of patients were not operated due to various reasons. The patient distribution by age and gender at the moment of correction of aortal coarctation showed that they included 68 (74.7%) males and 23 (25.3%) females in the ratio 2.9:1. The average patient age by that time was 14.7, ranging from 1 to 38 years.
 By the moment of discovery of post-coarctation aneurysm the patients’ age increased to an average 38.1, ranging from 21 to 60 years. The average time interval between the surgery of aortal coarctation and diagnosis of aneurysm of descending aorta was 22 years, ranging from 1 month to 45 years.
 The frequency of complications of aneurysm of descending aorta after surgery of aortal coarctation was different for various surgical methods. Among the aneurysms, which developed after coarctation correction, the most frequent were aneurysms after implantation of synthetic patch – 61(88.5%). The less frequent were aneurysms in 6 (8.7%) patients after implantation of tubular prostheses, and in 2 (2.8%) patients – after end-to-end anastomosis.
 Results and discussion. Till recent time the standard treatment practice was open surgical operation with direct access to proximal part of descending aorta by left-sided lateral.
 In our Department 85 surgical interventions were performed, including 69 surgeries by the traditional surgical method. From these patients, 7(10.1%) were operated two times, and 2(2.9%) – three times. In all 69(81.2%) cases, operated by open traditional surgical method, we performed vascular prosthesis implantation.
 Such operations require highly qualified anesthetic support with obligatory differential endobronchial intubation, cor-rection of disorders of respiratory and kidney functions, and compensation of present and possible blood loss [4]. Consider-ing high probability of uncontrolled hemorrhage at the stage of aneurysm mobilization, we installed temporary bypass graft – 75.3% or CPB pump – 24.7%, from ascending aorta or left atrium to descending aorta or femoral artery.
 Hospital mortality in this patient cohort was 5.9%.The use of endovascular treatment of thoracic aorta aneurysm increased considerably since Dake et al. in 1994 implanted the first stent-graft into thoracic aorta.
 In our Department, we performed 16(18.8%) of the procedures under general anesthesia with spinal drainage. For the patients, who require the covering of the zone of going of left subclavian artery or left common carotid artery, we perform extra-anatomic shunting 9(10.5%), or even subtotal debranching 2(0.2%), if there is no possibility to use individually pre-pared scalped stent-graft. The most common access is through common femoral artery by operative access 15(17.6%), or, more recently, by transcutaneous access 1(1.1%).

Modelling and numerical simulation of the in vivo mechanical response of the ascending aortic aneurysm in Marfan syndrome.

Marfan syndrome (MFS) is a genetic disorder that affects connective tissue, impairing cardiovascular structures and function, such as heart valves and aorta. Thus, patients with Marfan disease have a higher risk of developing circulatory problems associated with mitral and aortic valves prolapse, manifested as dilated aorta and aortic aneurysm. However, little is known about the biomechanical characteristics of these structures affected with MFS. This study presents the modelling and simulation of the mechanical response of human ascending aortic aneurysms in MFS under in vivo conditions with intraluminal pressures within normotensive and hypertensive ranges. We obtained ascending aortic segments from five adults with MFS subjected to a vascular prosthesis implantation replacing an aortic aneurysm. We characterised the arterial samples via ex vivo tensile test measurements that enable fitting the material parameters of a hyperelastic isotropic constitutive model. Then, these material parameters were used in a numerical simulation of an ascending aortic aneurysm subjected to in vivo normotensive and hypertensive conditions. In addition, we assessed different constraints related to the movement of the aortic root. Overall, our results provide not only a realistic description of the mechanical behaviour of the vessel, but also useful data about stress/stretch-based criteria to predict vascular rupture. This knowledge may be included in the clinical assessment to determine risk and indicate surgical intervention.

In Vitro Hemocompatibility Testing of Dyneema Purity Fibers in Blood Contact

Objective Heart valve and vascular prosthesis implantation is a common procedure for patients with heart valve stenosis or regurgitation and dilated or obstructive vascular disease. Drawbacks of conventional valve prostheses are the requirement for anticoagulant drugs, moderate durability, and suboptimal resistance to fatigue and tear. Dyneema Purity fibers are made from ultra-high-molecular-weight polyethylene filaments and are very thin, flexible, and fatigue and abrasion resistant and have high strength. Therefore, prostheses made from Dyneema Purity fibers might be attractive for use in the minimally invasive treatment of valvular- and vascular diseases. The aim of this study was to test the hemocompatibility of Dyneema Purity fibers in contact with blood. Methods Real-time platelet adhesion in human blood of 3 volunteers was quantified after 5 minutes of perfusion on single filaments (O 15 μm) of Dyneema Purity and polyester fibers. Plasma thrombin generation was measured by fluoroscopy for patches of Dyneema Purity fibers and for 5 commonly used polyester and expanded polytetrafluoroethylene cardiovascular prostheses. Results Platelet adhesion per 1 mm was 6 ± 1.4 on Dyneema Purity filaments and 15 ± 3.4 on polyester filaments (P = 0.02). Total formed thrombin and the time to peak of its maximum were noninferior for patches of Dyneema Purity fibers compared with the reference materials. Conclusions Dyneema Purity fibers are noninferior in adhesion and coagulation activation compared with commonly used cardiovascular prostheses.

In Vitro Hemocompatibility Testing of Dyneema Purity Fibers in Blood Contact.

Heart valve and vascular prosthesis implantation is a common procedure for patients with heart valve stenosis or regurgitation and dilated or obstructive vascular disease. Drawbacks of conventional valve prostheses are the requirement for anticoagulant drugs, moderate durability, and suboptimal resistance to fatigue and tear. Dyneema Purity fibers are made from ultra-high-molecular-weight polyethylene filaments and are very thin, flexible, and fatigue and abrasion resistant and have high strength. Therefore, prostheses made from Dyneema Purity fibers might be attractive for use in the minimally invasive treatment of valvular- and vascular diseases. The aim of this study was to test the hemocompatibility of Dyneema Purity fibers in contact with blood. Real-time platelet adhesion in human blood of 3 volunteers was quantified after 5 minutes of perfusion on single filaments (Ø 15 μm) of Dyneema Purity and polyester fibers. Plasma thrombin generation was measured by fluoroscopy for patches of Dyneema Purity fibers and for 5 commonly used polyester and expanded polytetrafluoroethylene cardiovascular prostheses. Platelet adhesion per 1 mm was 6 ± 1.4 on Dyneema Purity filaments and 15 ± 3.4 on polyester filaments (P = 0.02). Total formed thrombin and the time to peak of its maximum were noninferior for patches of Dyneema Purity fibers compared with the reference materials. Dyneema Purity fibers are noninferior in adhesion and coagulation activation compared with commonly used cardiovascular prostheses.

Electrophysiological, Hemodynamic, and Metabolic Response to Open Procedure or Endovascular Repair of Infrarenal Aortic Aneurysms

The occurrence of cardiovascular diseases in the group of patients undergoing vascular surgery because of abdominal aorta aneurysm is very high. Endovascular procedures are regarded as hemodynamically safer for the patients. The aim of this study was to compare the changes in electrophysiological, hemodynamic, and metabolic parameters depending on the type of operation, using invasive hemodynamic monitoring and Holter electrocardiography recording. A prospective, observational, nonrandomized study was conducted to compare dynamic changes of electrophysiological parameters (dominant rhythm, arrhythmia, corrected QT interval (QTc), invasive blood pressure, electrolytes, and acid-base balance in defined points during perioperative time in 2 groups: vascular prosthesis implantation group (91 patients) and stent-graft implantation group (83 patients). The study group comprised 174 consecutive adult Caucasian patients (mean age 64.4±8.9years in stent-graft group and 70.0±7.5years in vascular prosthesis implantation group). Although patients in the stent-graft implantation group were younger, they were diagnosed with lower limbs vascular atherosclerosis, type 2 diabetes mellitus, and a lower left ventricle ejection fraction more often than patients in the open procedure group. During the open procedure, higher blood pressure amplitudes (P=0.00009), higher decrease in pH (P=0.049), increase in the arterial lactate level (P=0.00002), prolonged QTc values (P=0.001), more frequent ventricular extrasystoles (P=0.005), and cardiovascular deaths were observed, when compared with those observed during the endovascular aneurysm repair. When compared with the chosen techniques, the one for infrarenal abdominal aneurysm was found to be associated with significant differences in electrophysiological, hemodynamic, and metabolic parameters.

Local tissue reaction and differentiation of the prosthesis‐specific antibody response following functional implantation of vascular grafts in pigs

The study was aimed at investigating the local tissue reactions through a histological examination of beta-1-integrin expression and neointima formation, and humoral immune responses by detection of prosthesis-specific antibodies, after functional implantation of vascular prostheses. In three groups of pigs, the infrarenal aorta was replaced with segments of collagen-impregnated Dacron-prostheses: M-prosthesis--medium primary porosity, double velour layer, crimping; C-prosthesis--low primary porosity, no velour, crimping; T-prosthesis--high primary porosity, no velour, no crimping. For each prosthesis type, one series with four animals was used for examining the tissue reactions, and a second series with eight animals was used to study the antibody response, both until 116 days postoperative. In the first three weeks, the M-prosthesis caused the highest tissue reactions and the highest antipolyester antibodies, but the lowest anticollagen antibodies, whereas the T-prosthesis caused the highest anticollagen antibodies, but the least tissue response and antipolyester antibodies in the early phase. On day 116, the C-prosthesis caused the highest tissue reactions and highest polyester-specific antibodies. These results indicate a possible association between local inflammatory reactions and humoral immune responses, influenced by properties of vascular grafts.

The challenges of imaging based computational fluid dynamics.

Image based Computational Fluid Dynamics (CFD) simulation of the cardiovascular system is increasingly becoming important and its application in everyday medical practice can already be envisaged. The goal of this workshop is to address all the factors involved in the development of a computational framework/software for modelling and analyses of the cardiovascular system and provide examples. The development of such framework, requires integration, management and interpretation of data from several technology areas such as a) feature detection and extraction of arterial geometry from imaging data, b) adaptive grid generation techniques for 3-D asymmetric geometries c) hemodynamic modelling, disparate length-scale model, and fluid-tissue interaction with high-performance computing, d) CFD data validation, e) feature extraction/detection and visualisation algorithms, f) graphical user interface to allow remote visualisation of post processed data. These computational tools are employed to study flow in specific problem sites in the vascular tree such as the carotid, femoral, coronary and abdominal arteries. Such studies provide understanding of the factors involved in the initialisation and evolution of arterial disease due to altered flow conditions (as a result of plaque formation) such as flow separation and reversal, and low and oscillatory wall shear stress. It is also used to study the effect of various clinical procedures such as the implantation of stents, vascular grafts, vascular prostheses and artificial valve implants on local and global hemodynamics. This workshop will address a new emerging paradigm in clinical practice known as predictive medicine for effective surgical planning and post surgical rehabilitation. The workshop will also address the difficulties in the implementation of some of the technology areas in this application with examples of carotid, femoral, and abdominal artery simulations.

Vascular closure staples reduce intimal hyperplasia in prosthesis implantation.

Vascular surgery, like the various other surgical specialities, has seen an increasing demand toward faster and more minimally invasive procedures. One such need is to create a reliable vascular anastomosis that is faster, easier and less damaging to the tissue. The vascular closure staples (VCS*) device provides such characteristics but, to date, no studies have investigated its effectiveness in reducing intimal hyperplasia when used for vascular prosthesis implantation. The present study evaluated its effectiveness compared with suturing of a graft in vascular prosthesis implantation. Twelve female Merino sheep underwent gelatin sealed Dacron patch graft implantation into the left and right common carotid artery. Grafts were randomly allocated so that one carotid artery and graft was anastomosed using sutures and the other with VCS*. The two techniques were compared for operation time, clip/suture numbers and blood loss during the implantation procedure. After a 4-week period, the sheep were killed and the grafts were harvested for intimal hyperplasia (IH) assessment. There was a significant reduction in the amount of IH seen in the VCS* group (mean +/- SD: 0.278 +/- 0.079 mm2/mm) when compared with the sutured group (0.575 +/- 0.331 mm2/mm) (P < 0.05). There was also significant reduction in anastomosis time (mean +/- SD: 14 +/- 4.4 min) and fewer points of contact (23 +/- 1.4) using the VCS* compared with suturing (22 +/- 3.2 min, P < 0.01; 27 +/- 3.3, P < 0.05, respectively). In this model, the VCS* shows several distinct advantages over suturing with significant time saving at operation and, most importantly, the reduction of IH seen at 1 month.

Immunogenicity of polymeric implants: long-term antibody response against polyester (Dacron) following the implantation of vascular prostheses into LEW.1A rats.

Implanted biomaterials trigger acute and chronic inflammatory responses directly correlated to the central role of phagocytic cells at the host-implant interface. This study was designed to evaluate specific humoral immune responses following repeated intraperitoneal implantations of collagen-impregnated polyester (Dacron) prosthetic segments into LEWIS rats. Serum antibody detection was performed by enzyme immunoassay with the prosthetic segments as a target. Cutoff values for antibody positivity were greater than or equal to the 99th percentile for control rats. Polymer immunoglobiulin G (IgG) antibodies were significantly increased (p < 0.05) by repeated implantation and were subsequently followed until experimental day 293. Antibody formation was significantly enhanced through the application of complete Freund's adjuvant in combination with the first implantation. All rats within this group were antibody-positive on day 53, but only 6 of 10 animals that received the prosthesis without the adjuvant were. After preincubation of sera with bovine collagen type I (solid phase adsorbed or in solution), polymer antibody binding was discovered not to be diminished, indicating that the IgG antibodies detected were not directed against the prosthesis impregnation. Furthermore, a significant correlation was obtained between polymer antibody binding to collagen-impregnated and nonimpregnated prostheses (r(s) = 0.797, p < 0.001). There was no substantiated correlation between antibody binding to polyester and to an irrelevant polymer (Tecoflex EG 80). We conclude that specific polymer antibodies may indeed provide an additional parameter for biocompatibility testing as well as a possible serological marker of an inflammatory response to implants.

Ruptures traumatiques aiguës de l’aorte thoracique et de ses branches. Résultats du traitement chirurgical

Study aim: The aim of this retrospective study was to report a series of 102 patients with acute traumatic rupture of the thoracic aorta and its branches (TRA) and to evaluate long-term results. Patients and methods: From April 1977 to April 2000, 102 patients with RTA were admitted to our unit. Age ranged between 12 and 74 years (mean age: 33 years). Localisation was: ascending aorta ( n = 3), aortic arch ( n = 1), isthmus ( n = 92), descending aorta ( n = 1), innominate artery ( n = 3), and left subclavian artery ( n = 2). Associated injuries mainly included craniocerebral lesions ( n = 76), rib fractures ( n = 68), and thoracic ( n = 38), and abdominal ( n = 24) lesions. Average time between trauma and surgery was 37 hours. Aortography was used routinely for diagnosis. Five patients were inoperable; the procedure was delayed in three patients. In all but two patients with rupture of the isthmus, descending aorta and subclavian artery, the operation included venous arterial femorofemoral assistance. Rupture was partial in 37 patients (37 direct sutures), and complete in 55 patients (40 direct sutures). In two cases of left subclavian artery desinsertion, the operation included suture of the aortic tear and reimplantation of the artery. In patients with rupture of the ascending aorta and aortic arch, surgery was carried out under cardiopulmonary bypass with deep hypothermia for aortic arch rupture. Repair consisted of direct suture. In patients with rupture of the innominate artery, the lesion was treated under cardiopulmonary bypass by direct suture. In five cases, abdominal injuries required emergency procedure before aortic repair. Results: Four patients died. No postoperative paraplegia occurred. The high morbidity rate was in relation to the associated injuries. Among the 93 survivors, the aortic clinical status was satisfactory in 91 patients (two patients were lost to follow-up). Two patients died from cancer and myocardial infarction 2 and 7 years later respectively. One patient had prosthetic sepsis and was reoperated on with homograft. Angiographic control by aortography ( n = 60) and angioMRI ( n = 22) was normal in 76 patients.There were five stenoses at the level of the prosthesis, four with a gradient < 20mmHg and one with a gradient > 50 mmHg and one aneurysm at the level of the isthmus.These last two patients were reoperated on with good result. Conclusion: RTA remains a surgical emergency with multiple difficulties. Despite the development of new imaging modalities, angiography remains the gold standard for the work-up of these patients. Venous arterial femorofemoral assistance with a pump remains the best procedure in order to avoid paraplegia and vascular prosthesis implantation when possible. Endovascular stent graft insertion, although still under investigation, holds tremendous promise for non-surgical treatment of these patients.

Intravascular therapy of aortic aneurysms: initial clinical results

A clinical study aiming at examining the implantation technique and the clinical results of a new vascular prosthesis in endovascular therapy of aneurysms of the aorta. In 21 patients (20 men of 55 to 87 years of age, average age 70 years) with aneurysms of the infrarenal abdominal aorta (AAA n = 19) and the thoracic aorta (n = 2), a self-expanding nitinol stent with outer Dacron sheath (tubular prosthesis n = 4; bifurcation prosthesis n = 17) was implanted by means of an F-18 introductory set after surgical opening of the inguinal artery. By means of the 4 tubular prostheses and 13 of the 17 bifurcation prostheses the aneurysm was bypassed completely. In 4 cases residual perfusion through leaks (n = 3) or collateral blood supply (n = 1) was seen. In 6 patients 7 complications occurred which did not require to be operated on. No patient died in consequence of the surgical intervention or during the hospital stay. Follow-ups up to 8 months after surgery did not reveal any late complications to date. Endovascular implantation of vascular prostheses is a promising new method for interdisciplinary treatment of aneurysms of the aorta.

The sonographic and computed radiographic findings in perigraft reactions after the surgical implantation of vascular prostheses

Between January 1988 and January 1994, 24 patients with heterologous vascular bypasses were examined with suspected diagnosis of a perigraft reaction (PGR). All patients were subjected to ultrasound and CT. PGR ist defined as a sterile inflammation along the course of a vascular prosthesis. The typical clinical presentation is a fluctuating tumour with a localised painless swelling. In all cases liquid formations could be confirmed by diagnostic imaging procedures; signs of infection could be excluded. The synopsis of the clinical presentation, the time interval after implantation of the prosthetic material and the signs of sonography and CT can reliably exclude infection of the prosthesis and confirm the diagnosis of a PGR.

主題I-1-3 小血管に対する代用血管移植術

主題I-1-3 小血管に対する代用血管移植術