Comparison of endovascular and conventional vascular prostheses in an experimental infection model

INTRODUCTION

The causes and management of prosthetic graft infections have been extensively studied for conventional bypass grafts; however, the infectivity and therapy for endovascular graft infections are completely unknown. The aim of this study was to compare the biologic properties of infected aortic grafts when inserted by endoluminal or standard transabdominal techniques.

METHODS

Eighteen dogs underwent placement of polytetrafluoroethylene grafts in their infrarenal aortas either by an endovascular technique (8) or a standard interposition technique (10). Endovascular grafts were constructed from polytetrafluoroethylene (3 cm) and two balloon-expandable stents coaxially mounted onto a balloon catheter delivery system. The grafts were inserted through a left carotid arteriotomy under fluoroscopic control. Initially, seven grafts were infected with decreasing inocula of Staphylococcus aureus, starting at 10(7) organisms per ml for 30 minutes and then rinsed briefly (10 seconds) in normal saline solution, until a 50% infective dose for the standard grafts was determined to be 10(2) organisms per ml. After this initial experiment, a second group of 11 dogs were compared at a concentration of 10(2) S. aureus per ml. Five dogs underwent endovascular repair, and six dogs had standard graft interpositions after an identical period of bacterial exposure. All grafts were removed at 2 weeks under sterile conditions and were submitted for quantitative culture analysis.

RESULTS

Three of the six dogs (50%) with standard grafts appeared to clear their infections, whereas only one of the five dogs (20%) with an endovascular graft was free of organisms at 14 days. This results was further manifested by statistically significant lower postmortem colony counts in the standard grafts (p < 0.01).

CONCLUSIONS

The endoluminal position of the graft and its proximity to the arterial wall do not appear to provide protection against infection. These data suggest that if endovascular grafts become infected, they may be in a disadvantaged position for host defense mechanisms to be effective.

Endovascular aortounifemoral grafts and femorofemoral bypass for bilateral limb-threatening ischemia

PURPOSE

Although axillobifemoral bypass procedures have a lower mortality rate than aortobifemoral bypass procedures, they are limited by decreased patency, moderate hemodynamic improvement, and the need for general anesthesia. This report describes an alternative approach to bilateral aortoiliac occlusive disease using unilateral endovascular aortofemoral bypass procedures in combination with standard femorofemoral reconstructions.

METHODS

Seven patients who had bilateral critical ischemia and tissue necrosis in association with severe comorbid medical illnesses underwent implantation of unilateral aortofemoral endovascular grafts, which were inserted into predilated, recanalized iliac arteries. The proximal end of the endovascular graft was fixed to the distal aorta or common iliac artery with a Palmaz stent. The distal end of the graft was suture-anastomosed to the ipsilateral patent outflow vessel, and a femorofemoral bypass procedure was then performed.

RESULTS

All endovascular grafts were successfully inserted through five occluded and two diffusely stenotic iliac arteries under either local (1), epidural (5), or general anesthesia (1). The mean thigh pulse volume recording amplitudes increased from 9 +/- 3 mm to 30 +/- 7 mm and from 6 +/- 2 mm to 26 +/- 4 mm ipsilateral and contralateral to the aortofemoral graft insertion, respectively. In all cases the symptoms completely resolved. Procedural complications were limited to one local wound hematoma. No graft thromboses occurred during follow-up to 28 months (mean, 17 months).

CONCLUSIONS

Endovascular iliac grafts in combination with standard femorofemoral bypass grafts may be an effective alternative to axillobifemoral bypass in high-risk patients who have diffuse aortoiliac occlusive disease, particularly when bilateral axillary-subclavian disease is present.

Immunolocalization and temporal distribution of cytokine expression during the development of vein graft intimal hyperplasia in an experimental model

PURPOSE

Vein graft stenosis caused by intimal hyperplasia (IH) accounts for 30% to 50% of late bypass graft failures; however, the biochemical mediators of vein graft IH have been poorly defined. We attempted to evaluate the spatial and temporal distribution of five principal cytokines (interleukin-1 beta [IL-1 beta], platelet-derived growth factor-AA [PDGF-AA], basic fibroblast growth factor [bFGF], interferon gamma [INF gamma], and tumor necrosis factor alpha [TNF-alpha]) during the development of IH in a rat vein graft model.

METHODS

Rat epigastric vein interposition grafts in the femoral artery were harvested at 6 hours, 2 days, 1 week, 2 weeks, and 4 weeks after the grafting procedure and studied with immunohistochemical and standard histologic techniques. The cytokine expression in the endothelium and media/neointima was quantified as the percentage of immunopositive cells per high-power field.

RESULTS

Maximal hyperplasia occurred 2 weeks after the grafting procedure. Peak expression of IL-1 beta and bFGF occurred by 2 days. PDGF-AA expression paralleled the development of IH, peaking at 2 weeks and then declining. TNF-alpha expression increased at 1 week and remained elevated. INF gamma was seen only in control grafts.

CONCLUSIONS

The coordinated early release of IL-1 beta and bFGF and the down-regulation of INF gamma seem to trigger an inflammatory response, thereby initiating IH. The process then is propagated by the release of PDGF-AA and TNF-alpha, with concomitant smooth muscle cell proliferation and production of extracellular matrix. It is likely that this complex milieu of local paracrine signaling is required to generate the hyperplastic response seen in failing vein grafts.

Effect of polytetrafluoroethylene covering of Palmaz stents on the development of intimal hyperplasia in human iliac arteries

PURPOSE

The occurrence of neointimal hyperplasia within a stent may result in restenosis with recurrent symptoms of end-organ ischemia. This study evaluated the potential of a nonporous covering of a stent to function as a barrier to the formation of intrastent neointimal hyperplasia.

MATERIALS AND METHODS

Twelve endovascular stent grafts were used to treat 12 high-risk patients with limb-threatening ischemia secondary to long-segment iliac artery occlusion. A 6-mm, thin-walled polytetrafluoroethylene graft was inserted and anchored to the common iliac artery with use of Palmaz stents. Each stent was covered by graft material over one-half of its length. Control angiograms obtained immediately after graft insertion were compared with follow-up angiograms obtained between 4 and 6 months after the initial procedure. On each angiogram, the region of the stent was magnified by 20x to permit computerized luminal diameter measurements.

RESULTS

The mean luminal diameter within the stent was significantly greater on the covered (7.7 mm +/- 0.33 standard deviation) compared with the uncovered (6.7 mm +/- 0.85 standard deviation) portions (P < .01).

CONCLUSIONS

Partially covered stents are a unique model for assessing the effects of an extrinsic stent covering on arterial healing and myointimal hyperplasia. These data suggest that a relatively nonporous covering of polytetrafluoroethylene may inhibit stent-related restenosis in iliac arteries.

Endovascular repair of aortoiliac occlusive disease

Occlusive disease of the aorta and iliac and femoral arteries may lead to limb-threatening ischemia when multiple levels of disease are present. The combined treatment of severe aortoiliac and infrainguinal disease using standard techniques may be hazardous or contraindicated in patients with multiple, previous reconstructions or severe co-morbid medical illnesses. This report summarizes the technical feasibility and early results of aortoiliac endovascular stented grafts (ESGs) in combination with conventional surgical reconstructions for the treatment of multilevel arterial occlusive disease. Forty-two patients with multilevel aortoiliofemoral limb-threatening occlusive disease had an ESG inserted to treat long-segment, multilevel, occlusive disease. ESGs originated from either the aorta or the common iliac artery and were inserted into one of the femoral arteries. ESG lengths ranged from 16 to 30 cm (mean 21 cm). Conventional surgical bypasses were constructed, when necessary, from polytetrafluoroethylene (PTFE) or saphenous vein and were extended using standard techniques to the popliteal, tibial, or contralateral femoral arteries. Technical success of graft insertion was achieved in 39 of 42 attempted ESG procedures (93%). The 18-month primary and secondary cumulative patency rates for ESGs were 89 +/- 9 (SE) and 100%, respectively. Limb salvage was achieved in 94% of patients at 24 months. Four patients had minor postprocedure complications (10%), and there was one death. Endovascular aortoiliac grafts, often in combination with conventional surgical infrainguinal bypasses, are a technically feasible, potentially safe option for the treatment of limb-threatening aortoiliofemoral occlusive disease and have demonstrated encouraging early patency. Long-term follow-up is necessary before widespread application of this technique is instituted.

Fluoroscopically assisted thromboembolectomy: an improved method for treating acute arterial occlusions

We performed bilateral femoral artery dissections in a single 50 kg mongrel dog. Digital fluoroscopic arteriograms documented the luminal diameter of the left iliac and right superficial femoral arteries. Balloon thrombectomy catheter passage was performed through hemostatic sheaths by 12 surgeons. Embolectomy balloons were filled with radiographic contrast material and the balloon catheter diameter was compared with the underlying vessel diameter. The percentage of overdistention of the embolectomy balloon relative to the arterial wall was 23% +/- 5% in the iliac artery and 40% +/- 13% in the femoral artery. Over a 25-month period, we used fluoroscopically assisted thromboembolectomy to treat 21 patients with acute arterial or graft occlusions. As the balloon was gently withdrawn to extract intravascular thrombus, deformities of the compliant balloon profile caused by underlying arterial lesions were identified fluoroscopically and their locations recorded to facilitate further treatment. After initial clot removal in these 21 patients, 15 residual lesions were documented. Repeat thrombectomy (n = 8), balloon angioplasty (n = 3), and placement of intravascular stents (n = 4) eliminated all 15 lesions. Luminal continuity was successfully restored in all 21 of these patients, 10 of whom required distal open vascular reconstruction to correct existing outflow artery disease. Fluoroscopically assisted thromboembolectomy is a simple and safe method for treating acute arterial or graft occlusions in patients with diffuse arteriosclerosis. It minimizes arterial damage and blood loss during balloon thrombectomy and reduces the need for intravascular contrast agents. It also has the potential to facilitate accurate identification, localization, and treatment of significant underlying arterial lesions.

c-MYC oncoprotein production in experimental vein graft intimal hyperplasia

PURPOSE

The expression of c-MYC oncoprotein in proliferating smooth muscle cells (SMCs) was analyzed in an experimental model of vein graft intimal thickening.

METHODS

Superficial epigastric vein grafts were inserted into the femoral arteries of male Sprague-Dawley rats. The vein grafts were harvested at 6 hr, 2 days, 1 week, 2 weeks, and 4 weeks after grafting and were rapidly frozen in liquid nitrogen. Immunohistochemical labeling and morphologic analysis of vein graft sections with a double staining technique were used to identify c-MYC/alpha SMC actin and proliferating cell nuclear antigen (PC10)/alpha SMC actin within intimal cells. c-MYC/alpha SMC actin and PC10/alpha SMC actin positive cells were quantitated in the perianastomotic area (R-1) and the body of the graft (R-2) for each time period. Total wall and intimal thickness of perfusion fixed vein grafts were measured with a computer digitized system.

RESULTS

Intimal and total wall thickening in the R-1 region peaked at 1 week (27.4 and 579.4 microns respectively) and were significantly thicker (P < 0.01) than the same region at 6 hr after graft implantation (6.0 and 113.5 microns respectively). Staining for c-MYC and PC10 in R-1 was also significantly higher (P < 0.05) at 1 week (5.75 and 7.00 positive cells/10 cells, respectively) compared with that at 6 hr (1.5 and 1.33, respectively). The R-1 region stabilized and remodeled over the following 3 weeks, while c-MYC and PC10 staining progressively decreased. In the R-2 region, intimal thickness significantly increased (P < 0.05) from 6 hr (4.0 micrometers) to 1 week (12.0 micrometers) and stabilized, while total wall thickness increased throughout the first week and the difference became significant at 2 weeks (P < 0.05). Staining for c-MYC and PC10 paralleled the staining in R-1 with a significant peak at 1 week (P < 0.05).

CONCLUSIONS

c-MYC oncoprotein is expressed early after experimental vein grafting, with peak expression at 1 week. This occurs during a period of maximal intimal thickening, SMC proliferation, and increased expression of PC10. Expression of c-myc protooncogene may contribute to the induction and regulation of SMC proliferation, producing intimal hyperplasia.

Somatosensory evoked potential monitoring during carotid surgery

Controversy exists over the value of intraoperative monitoring and shunting in patients undergoing carotid endarterectomy. Although it is widely believed that contralateral carotid occlusion and previous stroke mandate intraoperative shunting, the susceptibility of these two groups of patients to cerebral ischemia during carotid artery endarterectomy is not well defined. Somatosensory evoked potentials (SSEPs) were monitored in 113 carotid artery endarterectomy patients. Of these, 32 (28.3%) had a previous stroke, 24 (21.2%) had a contralateral carotid occlusion and 33 (29.2%) were diabetic. There were no deaths and only one perioperative stroke (0.9%). Cerebral ischemia occurred in 14 patients (12.4%). Six of these patients had a contralateral carotid occlusion. Some 29 patients (25.7%) were shunted, including 10 with contralateral carotid occlusions that did not have major SSEP changes. In the latter half of the study, 14 patients with contralateral carotid occlusions were selectively shunted (six shunted, eight not shunted) with no neurological complications. Thirty-two patients with prior strokes were selectively shunted (nine shunted, 23 not shunted); of these, one shunted patient undergoing combined carotid artery endarterectomy and coronary artery bypass grafting had a perioperative stroke. Intraoperative monitoring with SSEPs accurately identifies cerebral ischemia secondary to carotid clamping as well as patients requiring shunts. With use of intraoperative SSEP monitoring, selective shunting may be safely performed in patients with a contralateral carotid occlusion or a previous stroke.

The merit of polytetrafluoroethylene extensions and interposition grafts to salvage failing infrainguinal vein bypasses

PURPOSE

The purpose of this study was to evaluate the merit of polytetrafluoroethylene (PTFE) extensions and interpositions for the management of failing infrainguinal vein bypass grafts.

METHODS

The treatment of 133 failing vein grafts in 125 patients over a 10-year period was retrospectively reviewed. Twenty-two graft-threatening lesions were detected in patients who did not have a usable autogenous vein conduit as determined by preoperative and intraoperative evaluations. A PTFE extension or interposition graft was used for the necessary reconstruction in all cases.

RESULTS

Ten lesions were within the vein graft, 11 were proximal to the graft in the femoral or popliteal artery segments, and one was distal to the graft in the popliteal artery. The treatment of these lesions included 19 extensions and three mid graft interpositions. The vein graft lesions developed significantly sooner (mean 10.6+/-2.5 months) after the bypass (p<0.05) than the arterial lesions (mean 28.0+/-6.1 months). The 3-year cumulative secondary patency rate for these vein grafts treated with PTFE extensions or interpositions was 84%+/-8%. This was not significantly different from the 3-year cumulative secondary patency rate for vein grafts treated with vein extensions or interpositions at our institution over the same time period (82%+/-10%). The 3-year limb salvage rates were 95% and 89%, respectively.

CONCLUSIONS

These results indicate that PTFE extensions and interpositions can be used successfully to maintain the patency of failing vein grafts and may serve to prolong limb salvage in patients without any usable autogenous vein. Early reintervention with a PTFE conduit in this difficult group of patients is appropriate to salvage a failing vein graft.

Polytetrafluoroethylene bypasses to infrapopliteal arteries without cuffs or patches: a better option than amputation in patients without autologous vein

PURPOSE

This study was undertaken to evaluate our results of polytetrafluoroethylene (PTFE) tibial and peroneal artery bypasses done for limb salvage.

METHODS

Within a group of patients undergoing infrainguinal limb salvage bypasses at our institution between January 1986 and May 1995, 63 patients faced an immediate amputation, had no autologous vein on duplex examination and operative exploration, and had only a tibial or peroneal artery as an outflow vessel for bypass. Most of these patients (82%) had two or more prior ipsilateral infrainguinal bypasses. These 63 patients underwent 66 PTFE bypasses to a tibial or peroneal artery without a distal anastomotic vein cuff or an adjunctive arteriovenous fistula. Our results were then compared with those reported from infrapopliteal (crural) bypasses performed with alternate autologous vein sources or PTFE in conjunction with various recommended adjuncts.

RESULTS

The 3- and 5-year cumulative primary graft patency rates for our PTFE infrapopliteal bypasses were 39%+/-7% and 28%+/-9%, respectively. Secondary graft patency rates were 55%+/-8% and 43%+/-10% at 3 and 5 years, respectively. Limb salvage rates were 71%+/-7% at 3 years and 66%+/-8% at 5 years. Two-year actuarial patient survival rate was only 67%+/-7%.

CONCLUSIONS

These results indicate that a PTFE bypass to an infrapopliteal artery remains a worthwhile option in patients without usable autologous vein. The secondary patency and limb salvage rates were acceptable in this setting and were not significantly different from the best results reported with prosthetic tibial/peroneal bypasses with distal vein cuffs or patches (74% at 1 year; 58% at 3 years), arteriovenous fistulas (71% at 1 year) or composite arm vein grafts (39% and 29% at 3 and 5 years, respectively).

Initial experience with transluminally placed endovascular grafts for the treatment of complex vascular lesions

OBJECTIVES

Complex arterial occlusive, traumatic, and aneurysmal lesions may be difficult or impossible to treat successfully by standard surgical techniques when severe medical or surgical comorbidities exist. The authors describe a single center's experience over a 2 1/2-year period with 96 endovascular graft procedures performed to treat 100 arterial lesions in 92 patients.

PATIENTS AND METHODS

Thirty-three patients had 36 large aortic and/or peripheral artery aneurysms, 48 had 53 multilevel limb-threatening aortoiliac and/or femoropopliteal occlusive lesions, and 11 had traumatic arterial injuries (false aneurysms and arteriovenous fistulas). Endovascular grafts were placed through remote arteriotomies under local (16[17%]), epidural (42[43%]), or general (38[40%]) anesthesia.

RESULTS

Technical and clinical successes were achieved in 91% of the patients with aneurysms, 91% with occlusive lesions, and 100% with traumatic arterial lesions. These patients and grafts have been followed from 1 to 30 months (mean, 13 months). The primary and secondary patency rates at 18 months for aortoiliac occlusions were 77% and 95%, respectively. The 18-month limb salvage rate was 98%. Immediately after aortic aneurysm exclusion, a total of 6 (33%) perigraft channels were detected; 3 of these closed within 8 weeks. Endovascular stented graft procedures were associated with a 10% major and a 14% minor complication rate. The overall 30-day mortality rate for this entire series was 6%.

CONCLUSIONS

This initial experience with endovascular graft repair of complex arterial lesions justifies further use and careful evaluation of this technique for major arterial reconstruction.

Endovascular aortoiliac grafts in combination with standard infrainguinal arterial bypasses in the management of limb-threatening ischemia: preliminary report

PURPOSE

Occlusive disease of the aortoiliac segment may lead to limb-threatening ischemia, if coexisting disease is present in the femoral, popliteal, or tibial arteries. The combined treatment of severe aortoiliac and infrainguinal disease with standard techniques may be hazardous or contraindicated in patients with multiple previous reconstructions, severe comorbid medical illnesses, or both. This report summarizes the technical feasibility and early results of aortoiliac endovascular stented grafts (ESGs) in combination with conventional surgical reconstructions for the treatment of multilevel arterial occlusive disease.

METHODS

Seventeen patients with multilevel aortoiliofemoral limb-threatening occlusive disease had an ESG inserted to treat long-segment occlusive disease followed by a conventional surgical bypass. ESGs originated from the aortoiliac junction (seven) or the common iliac artery (10) and were inserted into the common femoral (nine), superficial femoral (four), or deep femoral (four) artery. ESG lengths ranged from 16 to 30 cm (mean, 21 cm). Conventional surgical bypasses were constructed from polytetrafluoroethylene (15) or saphenous vein (two) and extended to the popliteal (12), tibial (two), or contralateral femoral (three) arteries.

RESULTS

Technical success in graft insertion was achieved in 17 (94%) of 18 attempted ESG procedures. The 1-year primary and secondary cumulative patency rates for ESGs were 94% +/- 10% and 100%, respectively, whereas the 1- and 2-year patency rates for the extravascular grafts were 92% +/- 10% and 100%, respectively. Four patients had minor postprocedure complications (23%), and no deaths occurred. One patient lost his limb at 16 months because of severe pedal sepsis.

CONCLUSIONS

Transluminally placed stented grafts in combination with conventional surgical infrainguinal bypasses are a technically feasible and potentially safe option for the treatment of limb-threatening aortoiliofemoral occlusive disease and have demonstrated encouraging early patency. Long-term follow-up will be necessary before widespread application of this technique is advocated.

Human transluminally placed endovascular stented grafts: preliminary histopathologic analysis of healing grafts in aortoiliac and femoral artery occlusive disease

PURPOSE

The purpose of this study was to perform a preliminary histopathologic analysis of explanted human endovascular stented grafts from patients treated for occlusive disease.

METHODS

Over a 16-month period, 26 endovascular stented grafts were placed in 21 patients with limb-threatening ischemia caused by aortoiliac or femoral artery occlusive disease. All grafts were inserted through open arteriotomies remote from the region of primary disease. During the follow-up period, two patients died of preexisting heart disease 2 weeks and 7 months after grafting, and a portion of their endovascular grafts were the surrounding artery was explanted. Specimens from five other endovascular grafts were obtained during surgical revision for graft stenosis after 3 and 6 weeks and for outflow artery stenosis after 3, 5, and 6 months. All specimens were formalin fixed and studied with hematoxylin and eosin and trichrome staining and immunohistochemically for factor VIII-related antigen, alpha actin smooth muscle, macrophage antigen (MAC-387) and PC-10 (a mouse monoclonal antibody which specifically recognizes proliferating cell nuclear antigen in paraffin sections).

RESULTS

Three weeks after placement of the stented grafts, organizing thrombus was present on both surfaces of the expanded polytetrafluoroethylene (PTFE) grafts. At 6 weeks, evidence of a neointima with overlying endothelium was seen in the perianastomotic region, and 3 months after grafting it was seen 1 to 3 cm from the anastomosis. The specimen explanted at 5 months demonstrated factor VIII-positive cells 8 cm from the anastomosis. The histopathologic condition of the external capsule appeared to vary, depending on the presence or absence of an external wrap on the PTFE graft and on which layer in the arterial wall the graft was inserted. A foreign body reaction characterized by multinucleated giant cells was seen adjacent to wrapped grafts or around those placed in an intraadventitial plane. Grafts inserted within the media were surrounded by orderly, arranged, smooth muscle cells and few mononuclear cells. Extensive smooth muscle cell proliferation (PC-10 activity) was not seen within native artery atherosclerotic plaques peripherally displaced and external to prosthetic endovascular grafts.

CONCLUSIONS

These preliminary observations on the healing of PTFE endovascular stented grafts in human beings demonstrate limited plaque hyperplasia and the presence of endothelial cells on the luminal surface remote from the graft-artery anastomosis. It is unclear whether this is a unique manifestation of healing in prosthetic grafts inserted within the walls of arteries.

Placement of endovascular stented grafts via remote access sites: a new approach to the treatment of failed aortoiliofemoral reconstructions

Endovascular grafting is a technique that combines the use of intravascular stents and prosthetic grafts to fabricate devices with unique properties. The purpose of this study is to describe the use of endovascular graft technology in the treatment of failed or failing standard aortoiliofemoral reconstructions. Over a 15-month period five patients with limb-threatening ischemia and failed aortofemoral or iliofemoral reconstructions underwent successful placement of six endovascular grafts to revascularize seven severely ischemic lower extremities. Standard thin-walled 6 mm polytetrafluoroethylene grafts and Palmaz balloon-expandable stents were used to fashion each reconstruction. In addition to the primary endovascular grafts, three patients underwent immediate femoropopliteal bypasses to improve distal outflow and one patient had a femorofemoral bypass graft to restore circulation to the contralateral ischemic extremity. The ankle/brachial indices of all patients significantly improved after the procedure (from a mean of 0.32 to a mean of 0.75) and all grafts are patent to date (mean follow-up 10 months). There were no deaths or limb loss in this group of patients. These favorable results indicate that this minimally invasive approach, which permits a new arterial graft to be inserted through a remote access site, is a valuable method for providing unobstructed arterial inflow after aortoiliofemoral graft failure. This procedure may be particularly valuable when there are contraindications to the use of axillary arteries or the thoracic aorta as alternatives to complex reoperative abdominal aortic surgery.

Transluminally placed endovascular stented graft repair for arterial trauma

PURPOSE

Intravascular stents have become important tools for the management of vascular lesions; however, stents in combination with vascular grafts have only recently reached clinical application. This report describes an experience with stented grafts for the treatment of penetrating arterial trauma.

METHODS

Seven transluminally placed stented grafts were used to treat one arteriovenous fistula and six pseudoaneurysms. These grafts were successfully inserted percutaneously or through open arteriotomies that were remote from the site of vascular trauma. The devices were composed of balloon-expandable stainless steel stents covered with polytetrafluoroethylene grafts.

RESULTS

Patency up to 14 months was achieved (mean follow-up 6.5 months) with these stented grafts. The use of stented grafts appears to be associated with decreased blood loss, a less invasive insertion procedure, reduced requirements for anesthesia, and a limited need for an extensive dissection in the traumatized field. These advantages are particularly important in patients with central arteriovenous fistulas or false aneurysms who are critically ill from other coexisting injuries or medical comorbidities.

CONCLUSIONS

The use of stented grafts already appears justified to treat traumatic arterial lesions in critically ill patients. Although the early results with the seven cases in this report are encouraging, documentation of long-term effectiveness must be obtained before these devices can be recommended for widespread or generalized use in the treatment of major arterial injuries.

Transfemoral endovascular stented graft treatment of aorto-iliac and femoropopliteal occlusive disease for limb salvage

BACKGROUND

Endovascular stented grafts employ a new technique that blends intravascular stent and prosthetic graft technologies. These devices may be used to treat arterial aneurysms, occlusive disease, and vascular injuries. This report describes the application of stented grafts to the treatment of limb-threatening ischemia secondary to occlusive disease of the aorta, iliac, and femoral arteries.

METHODS

Three patients with limb-threatening ischemia and severe comorbid medical illnesses were treated with transvascular stented grafts that were composed of 6-mm thin-walled polytetrafluoroethylene grafts and Palmaz balloon expandable stents. The grafts were inserted through a cutdown in an artery remote from the site of occlusion and introduced into the vascular system within 14-Fr introducer sheaths.

RESULTS

Technical success was documented in all three patients with restoration of arterial continuity following stent graft deployment. Patency and limb salvage has been achieved to 1 year. One patient required further dilatation of the proximal stent at 6 weeks. Complications were limited to an iliofemoral deep vein thrombosis in one patient.

CONCLUSIONS

Endovascular stented grafts can be inserted to treat limb-threatening ischemia. Although these initial results are encouraging, greater experience in more patients observed for longer periods of time is necessary before this technique can be advocated for widespread use.

Is percutaneous balloon angioplasty appropriate in the treatment of graft and anastomotic lesions responsible for failing vein bypasses?

We reviewed 95 cases of vein graft and anastomotic lesions treated with percutaneous transluminal balloon angioplasty (PTA) and 30 cases treated surgically. The therapy was deemed a failure if the lesion recurred or if the graft closed. The 21-month patency rate of lesions treated surgically was 86%, which was significantly better than the 42% patency rate for all lesions treated with PTA (P < 0.01). An evaluation of the lesion and graft characteristics that could influence the patency of stenotic lesions treated with PTA included: lesion length, minimum graft diameter, lesion location, and lesion type. The 66% patency rate at 24 months for the 41 simple lesions (single, nonrecurrent, < 15 mm in length, and within grafts > or = 3 mm minimal diameter) was significantly better than the 17% patency rate for the 50 complex lesions (multiple, recurrent, > or = 15 mm in length, or within grafts < 3 mm in minimal diameter) (P < 0.01). In addition, the 21-month patency rate for the surgically treated group (86%) was not significantly better than that of the angioplasty-treated simple lesions (66%). When feasible, vein graft lesions are best treated with simple surgical interventions. PTA can be useful to maintain the patency of severely compromised grafts prior to surgical repair, to treat simple lesions difficult to reach surgically, and for patients with medical contraindications for an operation.

Reaction to injury following balloon angioplasty and intravascular stent placement in the canine femoral artery

Intravascular stents are used clinically as an adjunct to coronary and iliac angioplasty. This study was performed to evaluate the thrombogenicity and intimal hyperplasia incited by stents deployed in non-injured and in balloon-injured femoral arteries in the canine model. Medinvent stents (4 mm) were placed in the femoral arteries bilaterally in five mongrel dogs via cut down. This was preceded by balloon catheter angioplasty of the stent site on one side. Platelet deposition was measured at 30, 60, and 90 minutes and at 24 and 48 hours after stent placement, using gamma camera imaging of Indium111 platelets. The animals were killed after 2 months using a pressure perfusion technique, and the stents harvested. All vessels were patent at the time of harvest. Neointimal thickness was measured by computer image analysis. Platelet deposition was significantly increased on the angioplastied side compared to the non-angioplastied side at 60 minutes (5.67 x 10(9) +/- 1.4 versus 2.17 x 10(9) +/- 0.5 platelets/cm; P < 0.05), at 90 minutes (8.13 x 10(9) +/- 1.8 versus 2.33 x 10(9) +/- 0.6 platelets/cm; P < 0.05), and at 24 hours (stent-to-blood ratio = 15.86 +/- 6.3 versus 3.75 +/- 1.5; P < 0.05). Neointimal thickness was also significantly greater on the side of combined angioplasty and stent placement (0.45 +/- 0.21 mm versus 0.33 +/- 0.09 mm; P < 0.05). These results demonstrate that placement of intravascular stents in normal arteries is associated with a certain degree of thrombogenicity and formation of neointimal hyperplasia. Combining balloon angioplasty with stent placement significantly augments both thrombogenicity and production of intimal hyperplasia.(ABSTRACT TRUNCATED AT 250 WORDS)

Transfemoral endoluminal stented graft repair of a popliteal artery aneurysm

This report describes the use of an endoluminally placed stented graft to repair a large (2.6 by 2.6 by 15 cm) popliteal aneurysm in a 63-year-old man with advanced heart disease. Two balloon-expandable stents were attached to a 6 mm polytetrafluoroethylene graft, which was inserted with the patient receiving local anesthetic through a proximal superficial femoral artery arteriotomy. Repeat arteriography and duplex ultrasonography performed up to 3 months after the procedure documented graft and distal artery patency and complete aneurysmal exclusion without distal emboli. This experience demonstrates technical feasibility and early graft patency. However, additional experience and follow-up will be needed to assess the value of this minimally invasive procedure in the management of popliteal aneurysmal disease.

Is surveillance to detect failing polytetrafluoroethylene bypasses worthwhile?: Twelve-year experience with ninety-one grafts

PURPOSE

The purpose of this study was to review the 91 failing polytetrafluoroethylene (PTFE) grafts that were treated at our institution over the past 12 years to better understand their cause and improve the diagnosis and treatment of these grafts.

METHODS

Eighty-five patients with 91 failing grafts were retrospectively reviewed. The 144 graft-threatening lesions associated with these grafts were characterized by location (inflow artery, outflow artery, anastomosis, or graft body) and treatment method used (surgery, balloon angioplasty, or thrombolysis).

RESULTS

Progression of atherosclerotic disease was the predominant cause of failing PTFE grafts with 43 inflow lesions and 83 outflow lesions, accounting for 87% of all lesions identified. Ten lesions (7%) were noted within the prosthetic grafts, whereas only eight (6%) lesions were noted at the anastomoses. Forty stenotic lesions 2 cm in length or less were treated with percutaneous transluminal balloon angioplasty, whereas 100 lesions were treated by patch angioplasty or graft extensions. The remaining four lesions, present within the prosthetic grafts, were treated with thrombolytic therapy. The 5-year cumulative patency rate for all failing PTFE grafts was 71%, whereas that of failing femoropopliteal PTFE grafts was 64%. The 5-year limb salvage rate for all failing PTFE grafts was 73%.

CONCLUSIONS

The progression of inflow and outflow disease is the predominant cause of failing PTFE grafts, which suggests that this process is a more important cause of PTFE graft thrombosis than is generally recognized. Frequent PTFE graft surveillance may permit detection of some threatening lesions before graft thrombosis occurs and may help maintain and prolong graft patency. The enhanced 5-year patency and limb salvage rates for treated failing PTFE grafts compared with the known poor outcome after reinterventions for PTFE graft failure support the conclusion that surveillance of PTFE grafts is worthwhile.

Selective screening for coronary artery disease in patients undergoing elective repair of abdominal aortic aneurysms

PURPOSE

The purpose of this study was to retrospectively evaluate the effectiveness of screening for coronary artery disease before elective repair of abdominal aortic aneurysms (AAA) was performed.

METHODS

Results of a screening algorithm for coronary artery disease in 263 patients admitted to a single hospital for elective repair of AAA between January 1986 and December 1989 were analyzed. Patients with no coronary artery disease indicators proceeded to surgery without further workup. Patients with cardiac disease indicators underwent dipyridamole-thallium scintigraphy, and patients with angina were screened by use of cardiac catheterization; those with a recent coronary revascularization underwent no additional screening unless symptoms or electrocardiographic changes suggested an intervening event. Twenty-eight patients underwent no screen other than medical history and electrocardiogram.

RESULTS

Among 164 patients screened with dipyridamole-thallium scintigraphy, 44 patients had redistribution defects that required catheterization, and 11 of these underwent coronary revascularization. Cardiac catheterization was performed directly in 42 patients, which led to 11 revascularizations before AAA repair. Previous coronary artery bypass or percutaneous transluminal angioplasty obviated additional screening in 29 patients. Of the 263 scheduled AAA repairs, 15 were cancelled because of unacceptable operative risks, 13 for cardiac reasons. One patient died of a ruptured AAA after an uneventful coronary artery bypass. Among the 247 AAA repairs performed, there were three perioperative deaths (1.2%), all of which resulted from sudden cardiac events; three additional patients had nonfatal myocardial infarctions (1.2%), for a total cardiac complication rate of 2.4%.

CONCLUSIONS

The low rate of cardiac complications in this experience affirms the effectiveness of preoperative screening and selective coronary revascularization before AAA repair.

Saphenous vein biopsy: a predictor of vein graft failure

PURPOSE

To determine why some vein grafts fail, we prospectively studied the relationship between the histologic condition of the greater saphenous vein (GSV) at the time of grafting and subsequent stenosis of the vein graft.

METHODS

Ninety-four remnant segments of GSVs were obtained at the time of infrainguinal bypass in 91 patients and were perfusion fixed before histologic and ultrastructural examination. All bypass grafts were evaluated clinically and by duplex ultrasonography at regular intervals from 1 to 30 months after operation. All 24 grafts that developed lesions that caused thrombosis (failed grafts) or flow reduction (failing grafts) underwent arteriography and appropriate operative or other interventional correction of the causative lesion.

RESULTS

There was no significant difference in the incidence of coronary artery disease, kidney disease, hypertension, or history of smoking in patients with normally functioning and failed or failing grafts. Diabetes occurred with an increased frequency in failed or failing grafts (p = 0.056). At the time of their insertion, GSVs that subsequently developed significant lesions had thicker walls (0.72 +/- 0.33 mm) compared with normally functioning grafts (0.58 +/- 21 mm; p < 0.02). Most of this difference was related to a significantly thicker intima (0.27 +/- 0.17 vs 0.11 +/- 0.7 mm; p < 0.0001). Another significant finding was the presence of subendothelial spindle-shaped cells greater than five cell layers thick. This occurred more often in pregraft biopsies from grafts that developed significant lesions (70.4% vs 7.5%, p < 0.0001). Electron microscopic examination of these cells demonstrated a subpopulation of poorly differentiated cells with few fibers and many vesicles. Four of 24 (17%) failed or failing grafts had evidence of vein wall calcification at the time of vein grafting. This was seen in only one (1.4%) of 70 normally functioning grafts without lesions (p < 0.005).

CONCLUSIONS

We conclude that GSVs with thick and calcified walls or hypercellular intima at the time of grafting are at increased risk of developing intragraft lesions that may lead to graft failure. Frequent duplex ultrasonography surveillance is particularly warranted for such high-risk grafts.

A new look at intraoperative completion arteriography: classification and management strategies for intraluminal defects

Completion arteriography is widely regarded as an essential component of infrainguinal bypasses. However, the significance of various intraluminal filling defects is poorly defined, and strategies for managing these defects are unclear. Completion arteriography was performed by a standard technique in 78 infrapopliteal bypasses and were evaluated prospectively for the presence of angiographic defects. Thirty-nine arteriograms (50%) had no visible abnormality (grade O). Six arteriograms (8%) had minimal (grade I) defects, i.e., round lucencies (bubbles) or valve leaflets. Eighteen arteriograms (23%) had moderate (grade II) defects, i.e., uniform smooth tapering (up to 90% of luminal diameter) of the graft or outflow artery, irregular intraluminal filling defect (less than 60% of luminal diameter) within the distal graft or its adjacent outflow artery, or incomplete or faint graft opacification. Fifteen arteriograms (19%) had severe (grade III) defects, i.e., total cutoff of graft or outflow artery opacification or irregular intraluminal filling defect (greater than 60%) in the distal graft or adjacent outflow artery. Completion arteriograms were further stratified for type of bypass and outflow characteristics. All 24 bypasses with grade I or grade II defects on completion arteriography had no further surgical treatment. However, the 18 bypasses with grade II defects on completion arteriography had minimal nonsurgical manipulations consisting of repeat arteriography without or with papaverine infusion or urokinase instillation. In all 18, repeat arteriography showed improvement in the defect. The 15 bypasses with grade III defects had further surgical intervention (graftotomy, thrombectomy, vein patching, interposition graft, or graft extension). One-month and 1-year patency rates for grafts with grade I and grade II defects (87% and 79%, respectively) were not significantly worse than those for the 39 grafts with no arteriographic abnormalities (87% and 82%, respectively). In contrast, grafts with grade III defects had significantly worse (p < 0.01) 1-month and 1-year patency rates (33% and 20%, respectively) despite aggressive surgical correction of the arteriographic defects. These results emphasize the value of repeat completion arteriography and minimal interventional strategies when grade I or II defects are seen on arteriography. The poor outcome with surgical correction of grade III defects suggests that completion arteriography may not always define the full extent of the problem or that the corrective surgical maneuvers were either incomplete or detrimental.