Prosthetic Vascular Graft Research Articles

Secondary Patency of Thrombosed Prosthetic Vascular Access Grafts with Aggressive Surveillance, Monitoring and Endovascular Management

Secondary Patency of Thrombosed Prosthetic Vascular Access Grafts with Aggressive Surveillance, Monitoring and Endovascular Management

Diagnostics of “non-acute” vascular prosthesis infection using 18F-FDG PET/CT: our experience with 96 prostheses

Vascular prosthesis infection (VPI) is a life-threatening complication that occurs in 0.5-5% of prostheses. Low-grade infections in non-acute patients are a diagnostic challenge requiring a new method with good diagnostic accuracy. The aim of this work was to define the accuracy of (18)F-FDG PET/CT in these settings and to identify essential parameters of the evaluation. PET/CT was performed prospectively in 76 consecutive patients with a total of 96 vascular prosthetic grafts in which infection was suspected. PET/CT scans were analysed in terms of the presence and intensity of focal and diffuse FDG uptake, the presence of an anastomotic pseudoaneurysm, the presence of an irregular boundary of infiltration, a combination of these, and the uptake ratio between the graft and blood background. The gold standard was based on operative/histopathological finding or a clinical follow up of >6 months. Among the various assessed parameters only focal FDG uptake and an irregular graft boundary were significant predictors of VPI. Focal intense FDG uptake together with an irregular boundary of the lesion on CT scan predicted VPI with 97% probability, while smooth lesion boundaries and no focal FDG uptake predicted a probability of VPI of less than 5%. Even in lesions with nondiagnostic inhomogeneous focal FDG uptake (18/96) an irregular boundary effectively helped in decision-making with a probability of 28% (smooth) or 77% (irregular) for VPI. PET/CT gave reliable results with an accuracy >95% in 75% of prostheses. PET/CT can identify those prostheses (25% of prosthesis) for which its diagnostic accuracy is diminished to 70-75%. In our series PET/CT was an excellent diagnostic modality for suspected VPI.

Infecciones asociadas a las válvulas protésicas cardíacas, las prótesis vasculares y los dispositivos de electroestimulación cardíacos

The implantation of biological or mechanical heart valves, pacemakers, defibrillators, and prosthetic vascular grafts can save the life of patients with valvular heart disease, conduction disorders, arrhythmia, or vascular disease. The use of these devices has increased in the general population. Antibiotic prophylaxis is indicated to prevent cardiovascular device-related infections, which are uncommon, but have high associated morbidity and mortality. We review the epidemiology, pathogenesis, clinical manifestations, diagnosis, treatment, and prevention of these infections. Staphylococci are the most common etiological agents, and the infection is thought to result from contamination during device implantation or in the early postoperative period. Positive blood culture status, and diagnostic imaging (transesophageal echocardiography, computed tomography, magnetic resonance imaging) and nuclear medicine study (scintigraphy using labeled leukocytes) are the basic tools to establish the diagnosis. Treatment is complex and requires prolonged antibiotic administration targeting the isolated organisms, and device removal to attain cure.

The in vivo stability of electrospun polycaprolactone-collagen scaffolds in vascular reconstruction

To avoid complications of prosthetic vascular grafts, engineered vascular constructs have been investigated as an alternative for vascular reconstruction. The scaffolds for vascular tissue engineering remain a cornerstone of these efforts and yet many currently available options are limited by issues of inconsistency, poor adherence of vascular cells, or inadequate biomechanical properties. In this study, we investigated whether PCL/collagen scaffolds could support cell growth and withstand physiologic conditions while maintaining patency in a rabbit aortoiliac bypass model. Our results indicate that electrospun scaffolds support adherence and growth of vascular cells under physiologic conditions and that endothelialized grafts resisted adherence of platelets when exposed to blood. When implanted in vivo, these scaffolds were able to retain their structural integrity over 1 month of implantation as demonstrated by serial ultrasonography. Further, at retrieval, these scaffolds continued to maintain biomechanical strength that was comparable to native artery. This study suggests that electrospun scaffolds combined with vascular cells may become an alternative to prosthetic vascular grafts for vascular reconstruction.

When Antibiotics are Unnecessary

Dermatologists can decrease unnecessary use of antimicrobial agents by avoiding them in situations wherein good evidence indicates that they are ineffective. Controlled trials indicate that antimicrobial agents are unhelpful in treating cutaneous abscesses, inflamed epidermal cysts, uninfected atopic eczema, and cutaneous ulcers caused by venous insufficiency or diabetes in the absence of significant contiguous soft-tissue inflammation. Prophylactic antibiotics are rarely appropriate for routine dermatologic surgery and are not indicated for patients who have prosthetic joints or vascular grafts. They are recommended only for a small group of patients who have abnormal cardiac valves, and then only with surgery involving clearly infected skin or soft-tissue. Topical antibiotics are no better than white petrolatum in covering sutured wounds, and with moist occlusive dressings, no ointment is necessary.

Infection primaire de prothèse vasculaire à salmonelle et traitement conservateur

The authors report an unusual case of prosthetic vascular graft infection due to Salmonella typhimurium. The initial treatment combined antibiotherapy and surgical replacement of the arteriovenous graft. The infection relapsed within 6 weeks and was successfully treated with antibiotics only. Five cases of vascular graft infection due to Salmonella have been reported so far, but only one occurred in a previously healthy man and was not related to local infection, but to bacteremic seeding. Specific features of vascular graft infection and importance of prevention are discussed.

Enhanced Perigraft Angiogenesis Prevents Prosthetic Graft Infection

Prosthetic vascular graft infection is an unsolved fatal complication after aortic surgery. We hypothesized that increased vascularity around a prosthetic graft may exert a preventive role against bacterial infection. Eighty-three Fischer rats were divided into five groups according to the types of subcutaneously implanted prosthetic graft and granulocyte-colony stimulating factor (G-CSF) treatment. The groups G and C had gelatin hydrogel microspheres-incorporated graft (gel graft) with or without concomitant systemic administration of G-CSF (50 microg/kg), respectively. The groups FG and F had the gel graft impregnated with 100 mug of basic fibroblast growth factor (bFGF) with or without systemic G-CSF. The group N received untreated grafts. Seven days after graft implantation, broth containing methicillin-sensitive Staphylococcus aureus (4.0 x 10(3) colony-forming units) was inoculated onto the graft. All the grafts and the surrounding tissues were explanted 2 days later. Quantitative culture for methicillin-sensitive Staphylococcus aureus from the grafts and histologic assessment for capillary number in the tissue were performed. Positive infection rates in the groups N, C, and G were 34.7%, 30.4%, and 15.3%, respectively; whereas those were zero in the F and FG groups. Tissue around the grafts demonstrated significantly higher number of capillaries in the groups F and FG compared with the groups C and G. The number of bacterial colonies inversely correlated with the number of capillaries around the implanted graft (r = -0.32, p < 0.05). Basic fibroblast growth factor incorporated into a prosthetic graft with or without systemic G-CSF can induce angiogenesis around the graft and prevent prosthetic graft infection.

Secondary Patency of Thrombosed Prosthetic Vascular Access Grafts with Aggressive Surveillance, Monitoring and Endovascular Management

Background: To study the long-term patency of thrombosed prosthetic vascular access grafts treated with percutaneous mechanical thrombectomy (PMT) followed by aggressive surveillance and monitoring and repeated endovascular interventions. Study design: Two hundred seven vascular access grafts presented with first-time thrombosis were treated with PMT using the AngioJet device (n = 185) or the Arrow-Trerotola percutaneous thrombolytic device (n = 22) followed by angioplasty (± stenting) of the anatomical lesion responsible for the thrombotic event. Clinical success was considered at least one successful subsequent hemodialysis session. Graft surveillance/monitoring included clinical and hemodialysis parameters to detect a failing or thrombosed graft. Results: PMT was technically successful in 202 cases (97.6%) and clinically successful in 193 cases (93.2%). During follow-up, 149 got thrombosed and either abandoned (n = 33) or underwent at least once repeat thrombectomy (n = 116); finally 100 grafts were abandoned (n = 90), ligated (n = 5) or removed (n = 5). Endovascular management (0.54 procedures per 100 graft-days, thrombectomy, n = 307 sessions and angioplasty, n = 162 sessions) increased significantly functional assisted-primary patency rates from 29% and 14% at 1 and 2 years to a secondary patency of 62% and 47%, respectively. Secondary patency was worse in loop grafts (P = .02) and intermediate graft thrombosis (occurred between 31–182 days after graft placement, P < .001) and better when renal failure was due to hypertension or diabetes (compared to other or cryptogenic causes, P = .048) or isolated angioplasty for graft dysfunction during follow-up had been performed (P < .001). Multivariate analysis identified intermediate graft thrombosis and isolated angioplasty as independent predictors of secondary patency (P < .001, relative risk 2.77 and P < .001, relative risk 0.28, respectively). Conclusions: PMT is a highly successful procedure with acceptable long-term secondary patency results, provided that aggressive endovascular management of subsequent thrombotic or dysfunction episode is performed. Further research to identify the causes of intermediate graft thrombosis is justified.

Secondary Patency of Thrombosed Prosthetic Vascular Access Grafts with Aggressive Surveillance, Monitoring and Endovascular Management

Background To study the long-term patency of thrombosed prosthetic vascular access grafts treated with percutaneous mechanical thrombectomy (PMT) followed by aggressive surveillance and monitoring and repeated endovascular interventions. Study design Two hundred seven vascular access grafts presented with first-time thrombosis were treated with PMT using the AngioJet device ( n = 185) or the Arrow-Trerotola percutaneous thrombolytic device ( n = 22) followed by angioplasty (± stenting) of the anatomical lesion responsible for the thrombotic event. Clinical success was considered at least one successful subsequent hemodialysis session. Graft surveillance/monitoring included clinical and hemodialysis parameters to detect a failing or thrombosed graft. Results PMT was technically successful in 202 cases (97.6%) and clinically successful in 193 cases (93.2%). During follow-up, 149 got thrombosed and either abandoned ( n = 33) or underwent at least once repeat thrombectomy ( n = 116); finally 100 grafts were abandoned ( n = 90), ligated ( n = 5) or removed ( n = 5). Endovascular management (0.54 procedures per 100 graft-days, thrombectomy, n = 307 sessions and angioplasty, n = 162 sessions) increased significantly functional assisted-primary patency rates from 29% and 14% at 1 and 2 years to a secondary patency of 62% and 47%, respectively. Secondary patency was worse in loop grafts ( P = .02) and intermediate graft thrombosis (occurred between 31–182 days after graft placement, P < .001) and better when renal failure was due to hypertension or diabetes (compared to other or cryptogenic causes, P = .048) or isolated angioplasty for graft dysfunction during follow-up had been performed ( P < .001). Multivariate analysis identified intermediate graft thrombosis and isolated angioplasty as independent predictors of secondary patency ( P < .001, relative risk 2.77 and P < .001, relative risk 0.28, respectively). Conclusions PMT is a highly successful procedure with acceptable long-term secondary patency results, provided that aggressive endovascular management of subsequent thrombotic or dysfunction episode is performed. Further research to identify the causes of intermediate graft thrombosis is justified.

In Vitro Approach to the Dilative Behavior of Knitted Vascular Prosthetic Grafts

The purpose of this report is to propose an in vitro approach to predicting the long-term dilative behavior of knitted polyester prosthetic grafts. Various techniques were applied to five warp knitted fabric prosthetic grafts in order to determine the following fabric properties: knitted fabric structure, textile structure, number and respective linear density of threads and strands, and length of yarn in each stitch. Following these investigations, the prosthetic grafts underwent testing to determine specific strength at break, breaking extension, and stress-strain curve. On two prosthetic grafts, image analysis was performed during circumferential tensile strength testing in order to monitor changes in structural features as a function of stress. Changes in the distance between two wales and two courses of stitches and stitch surface were measured. In addition to surface deformation, thickness was measured, using an induction sensor. Study of fabric structure showed many differences between the five models made by different manufacturers. Knit fabric structure was Indeforma in three cases and half-tricot in two. Strand number and size varied greatly from one model to another. Pattern also varied from one model to another, with knit stitch density varying from 1 to 3. Specific strength at break testing showed great differences in the mechanical properties of the grafts. These differences were especially obvious in the first part of the rheograms, which reflects the ability of the graft to comply in response to low-strength forces, i.e., much lower than those necessary to cause rupture. Image analysis of stitch behavior under stress further confirmed differences in graft behavior depending on the fabric structure adopted by the manufacturers. The in vitro approach proposed in this study to analyze the fabric characteristics of knitted prosthetic grafts effectively revealed differences in construction and behavior. These differences could account for differences in the dilative behavior of grafts in vivo.

An effective vacuum-assisted closure treatment for mediastinitis with aortic arch replacement

Little experience exists with the vacuum-assisted closure (VAC) therapy in the high-risk group of patients with perigraft abscess containing a large amount of prosthetic vascular grafts. We report our experience in the VAC therapy for patients with mediastinitis after aortic arch replacement. Between February 2003 and December 2006, five patients with a mean age of 72.2 years developed postoperative mediastinitis after aortic arch replacement, and were treated with the VAC system. In all the patients the mediastinal fluid and tissue examinations turned out to be negative for microbiological cultures, and successful closure of the midline incision was achieved with concomitant omental transfer after a mean duration of 22.6 days of VAC treatment. Four of the five patients survived to discharge and have been free from recurrent sign of mediastinal or graft infection at long-term follow-up. Our study indicates that the VAC treatment may reduce early mortality of life-threatening deep sternal wound infection complicated by a prior aortic arch replacement and become a preferred therapeutic option for the patients to whom another replacement is too risky.

Propofol and Systemic Inflammatory Response in Abdominal Aortic Surgery

Abdominal aortic surgery is relatively common associated with considerable postoperative morbidity and mortality. The aortic cross-clamping for the implantation of a vascular prosthetic graft induces a systemic inflammatory response (SIR) because of an ischemia-reperfusion (IR) injury. In our experimental models we have reported that propofol anesthesia, compared with sevoflurane, after IR modulates SIR and this effect might result in renal protection. Keywords: Propofol, Systemic inflammatory response, Aortic surgery, Aortic cross-clamping

Silver-coated dacron prosthesis in the treatment of infection in arterial surgery: Case reports

Although the incidence is low, infection of prosthetic vascular graft bears a high incidence of serious complications including 25-75% mortality rate and 40-75% limb loss. The standard treatment of vascular graft infection consists of excision of the prosthesis, wound debridement and extraanatomic revascularization. Conservative treatment might be an option in a limited number of patients. We present three cases of surgical and conservative treatment of vascular graft infection. Case 1: A patient developed silver-coated graft infection after femorodistal arterial reconstruction performed because of critical limb ischemia. In the early postoperative period, massive skin and subcutaneous tissue necrosis developed, with the graft being exposed. After two months of persistent debridement and wound toilette, the defect was covered with aThiersch skin graft. Case 2: PTFE graft infection in the right groin followed reconstruction of the isolated common femoral artery aneurysm. This graft was replaced with a silver-coated graft in situ. Reinfection of the proximal end of the implanted silver-coated graft occurred and the graft was exposed. After repeated debridement and wound toilette, the exposed prosthesis was covered with granulomatous tissue, and the wound healed. Case 3: A year after anastomotic pseudoaneurysm resection in the left groin, prosthesis was exposed following wound infection. This graft was substituted with a silver-coated graft in situ. The wound healed primarily. These three cases demonstrate that under some circumstances vascular prosthesis infection can be successfully treated conservatively without graft removal, and also by in situ replacement using silver-coated graft.

Laparoscopic Diagnosis and Treatment of Aortic Vascular Prosthetic Graft Infections in a Porcine Model

Laparoscopic Diagnosis and Treatment of Aortic Vascular Prosthetic Graft Infections in a Porcine Model

Endovascular repair of descending thoracic aortic aneurysm: preliminary experience

To report an initial experience with the endovascular repair of descending thoracic aortic aneurysm (DTAA). Endoprostheses were placed into 41 patients with DTAA between January 2001 and July 2007 which were retrospectively analyzed. The preliminary right-left carotid and left carotid-subclavian bypass was performed in 4 cases in which the distances from the proximal aneurysm to the origin of the left common carotid artery were no longer than 15 mm. EVAR was conducted 1 week after the bypass or immediately. All stent grafts were deployed in proper position. There were two deaths (4.9%) during perioperative period, resulting from multiorgan failure and acute cardiac infarction, respectively. Eighteen endoleaks occurred immediately after EVAR (43.9%), four disappeared after balloon dilatation. There were two acute renal insufficiencies (4.9%), one requiring hemodialysis for more than 30 days. Follow-up, which ranged from 1 to 60 months [median, (18.6 +/- 4.2) months] was carried out in 26 patients (63.4%). Type-I endoleak and type-III endoleak were detected in two patients in 4 years and 2 years after EVAR, might because of migration, and were corrected using another stent-graft each. Two patients died of other diseases during follow-up. Complete thrombosis of the thoracic aneurysm sac with no late migration or endoleaks was revealed on CT at 3 months postoperatively in the remaining patients. The decrease in maximal aneurysm diameter was 0-22 mm [median, (8.3 +/- 4.5) mm] and the prosthetic vascular grafts in four patients with preliminary carotid subclavian bypass surgery were patent during the follow-up period. The treatment of descending thoracic aortic aneurysm with an endovascular approach is feasible with less trauma, quick recovery and less complications. It may offer the best means of therapy for high risk patients.

Surgical Strategy in Aortoesophageal Fistulae

The surgical treatment of aortoesophageal fistulae (AEF) has a high morbidity and mortality rate. We report our experience with the sequential use of endovascular thoracic stentgrafts and cryopreserved aortic homografts for in situ repair of the descending thoracic aorta. In a 7-year period, 6 patients with AEF were treated at our center. After primary endovascular repair in all cases, 4 patients subsequently underwent in situ repair of the descending thoracic aorta with cryopreserved homografts. Long-term antibiotic therapy was given in all cases. Recent clinical status and radiologic findings on follow-up studies of each patient were analyzed. The mean follow-up time was 35 months (range, 2-76). Endovascular stentgraft repair was technically successful in all cases. Two patients were not candidates for open surgical repair because of their medical condition; they both died within 8 weeks after discharge from the hospital, 1 from recurrent septic episodes, and the other from upper gastrointestinal bleeding. One of 4 patients who had undergone open surgical repair died 1 year later from upper gastrointestinal bleeding that occurred presumably due to an infectious degeneration of the homograft after secondary infection with a methacillin-resistant Staphyloccocus aureus. In 1 case persistent paraplegia and in another case persistent renal failure occurred. The use of cryopreserved homografts is a valuable alternative to in situ repair with prosthetic vascular grafts or extra-anatomic reconstructions in the surgical treatment of AEF. Endovascular stentgraft placement plays a role as a bridging procedure in emergency situations.

Inhibition of Apoptosis Prevents Shear-Induced Detachment of Endothelial Cells

Biomaterials placed into the vasculature in man fail to develop an endothelial lining. Attempts to seed endothelial cells (ECs) on prosthetic vascular grafts have failed due to flow-induced detachment. The mechanism of flow-induced detachment of ECs from biomaterials is undefined. We hypothesize that endothelial detachment from biomaterials is caused by flow-induced apoptosis related to the inability of human ECs to adapt to and withstand mechanical loading. Human aortic endothelial cells were cultured on Dacron membranes, incubated in the presence or absence of a caspase inhibitor (Z-VAD-FMK), and exposed to 0, 1, 10, 20, or 30 dynes/cm(2) of shear stress for 2, 6, 12, and 24 h in a parallel plate bioreactor. The percent of ECs detached was determined and compared with no-flow controls. Apoptosis was determined by analyzing nuclear morphology and identifying cells with caspase activity using FAM-VAD-FMK. The actin cytoskeleton of cells was visualized with fluorescein phalloidin. Increasing shear stress resulted in detachment of ECs from the Dacron membranes, which was associated with increased apoptosis of the residual cells adherent to the membrane determined by both nuclear morphology and caspase activity. Significantly, treatment with the caspase inhibitor Z-VAD-FMK resulted in improved EC retention following exposure to high shear stress (20 and 30 dynes/cm(2)). The majority of apoptosis and detachment were determined to occur after 6 h. We have demonstrated that high shear stress-induced EC detachment from Dacron is an apoptosis-dependent phenomenon that can be pharmacologically inhibited by a pan-caspase inhibitor.

Laparoscopic Diagnosis and Treatment of Aortic Vascular Prosthetic Graft Infections in a Porcine Model

To study the feasibility and efficacy of experimental laparoscopy in the diagnosis of aortic graft infection in pigs. Eight pigs had an aortic tube graft implanted and inoculated with either 5 x 10(4) or 10(6) CFU of Staphylococcus aureus ATCC 29213. Laparoscopy was performed after a median of 20 days with debridement and sampling for bacterial culture. Thereafter, the grafts were locally soaked in rifampicin and postoperatively, the pigs received rifampicin and ciprofloxacin orally for two weeks and were then sacrificed. All pigs developed graft infection. One pig died from severe clostridial septicaemia before laparoscopy could be performed. The remaining pigs had all samples for bacterial culture taken by laparoscopy from the inflamed tissue. The temperature dropped significantly after laparoscopy, and no macroscopic signs of infection presented at autopsy. However, only culture from one pig was without S. aureus at autopsy. Laparoscopy is a potential diagnostic tool for aortic graft infection and also affords the opportunity to carry out bacteriological sampling and local antibiotic treatment. The efficacy of laparoscopic treatment needs further evaluation.

Prosthetic vascular grafts: Wrong models, wrong questions and no healing

In humans, prosthetic vascular grafts remain largely without an endothelium, even after decades of implantation. While this shortcoming does not affect the clinical performance of large bore prostheses in aortic or iliac position, it contributes significantly to the high failure rate of small- to medium-sized grafts (SMGs). For decades intensive but largely futile research efforts have been under way to address this issue. In spite of the abundance of previous studies, a broad analysis of biological events dominating the incorporation of vascular grafts was hitherto lacking. By focusing on the three main contemporary graft types, expanded polytetrafluoroethylene (ePTFE), Dacron and Polyurethane (PU), accumulated clinical and experimental experience of almost half a century was available. The main outcome of this broad analysis—supported by our own experience in a senescent non-human primate model—was twofold: Firstly, inappropriate animal models, which addressed scientific questions that missed the point of clinical relevance, were largely used. This led to a situation where the vast majority of investigators unintentionally studied transanastomotic rather than transmural or blood-borne endothelialization. Given the fact that in patients transanastomotic endothelialization (TAE) covers only the immediate perianastomotic region of sometimes very long prostheses, TAE is rather irrelevant in the clinical context. Secondly, transmural endothelialization seems to have a time window of opportunity before a build-up of an adverse microenvironment. In selecting animal models that prematurely terminate this build-up through the early presence of an endothelium, the most significant ‘impairment factor’ for physiological tissue regeneration in vascular grafts remained ignored. By providing insight into mechanisms and experimental designs which obscured the purpose and scope of several decades of vascular graft studies, future research may better address clinical relevance.

Prosthetic Vascular Graft Infection: The Role of 18F-FDG PET/CT

Graft infection after prosthetic vascular reconstruction is an uncommon but severe complication. The clinical presentation is often subtle and nonspecific and may occur long after surgery. Although defining a prosthetic vascular graft infection can be difficult, early diagnosis and treatment are important because of the relatively high rates of amputation and death. The present study assessed the role of PET/CT using 18F-FDG for the diagnosis of vascular graft infections. Thirty-nine patients (35 men and 4 women; age range, 44-82 y) with suspected vascular graft infection underwent 18F-FDG PET/CT. The performance of PET/CT for the diagnosis of an infectious process and its localization to the graft or soft tissues was assessed. The final diagnosis was based on histopathologic findings and microbiologic assays obtained at surgery or on clinical and imaging follow-up. PET/CT detected foci of increased 18F-FDG uptake suspected as infection in 27 patients and localized these findings to the graft in 16 patients. Vascular graft infection was confirmed in 14 of these patients (88%). PET/CT excluded graft involvement in 11 patients, and in 10 (91%) of these 11, long-term follow-up further confirmed that the infectious process was limited to surrounding soft tissues only. No abnormal 18F-FDG uptake was found in any of the 12 patients with no further evidence of infection. PET/CT had a sensitivity of 93%, specificity of 91%, positive predictive value of 88%, and negative predictive value of 96% for the diagnosis of vascular graft infection. 18F-FDG PET/CT is a reliable noninvasive imaging modality for the diagnosis of vascular graft-related infection. The precise anatomic localization of increased 18F-FDG uptake provided by PET/CT enables accurate differentiation between graft and soft-tissue infection.