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Vascular and Interventional Radiology |
1 From the Department of Internal Medicine II, Division of Angiology, General Hospital Vienna, University of Vienna Medical School, Währinger Gürtel 18-20, A-1090 Vienna, Austria. Received May 29, 2001; revision requested July 9; revision received August 30; accepted October 10. Address correspondence to E.M. (e-mail: erich.minar@akh-wien.ac.at).
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ABSTRACT |
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 TOP ABSTRACT INTRODUCTIONMATERIALS AND METHODSRESULTS DISCUSSIONREFERENCES |
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MATERIALS AND METHODS: This prospective cohort study included 30 consecutive patients who underwent Dacron-covered stent-graft implantation because of recurrent stenosis after percutaneous transluminal angioplasty in the femoropopliteal segment. After interventional treatment, 100 mg of acetylsalicylic acid daily and oral anticoagulation therapy (therapeutic level, international normalized ratio, 2.0–3.0) were administered. Patients were followed up with ankle-brachial index measurement, color-coded duplex ultrasonography, and angiography. Primary and secondary patency rates and postintervention complications were documented as was initial technical success. Kaplan-Meier and life table analyses were used for calculation of patency rates.
RESULTS: Initial technical success was achieved in all 30 patients, with significant improvement of ankle-brachial index from a preintervention mean of 0.5 ± 0.14 (SD) to a postintervention mean of 0.8 ± 0.17 (P < .001). Postimplantation noninfectious fever and leukocyte and C-reactive protein level elevation occurred in 12 patients (40%), and 17 patients (57%) reported persistent pain at the site of implantation for a mean of 5 days (range, 2–28 days). Early recurrent occlusion within the first 24 hours was found in five patients (17%). Within the mean follow-up period of 60 months ± 10, restenosis occurred in 25 patients (83%). At 6, 12, 36, and 72 months, respectively, primary patency rates were 27%, 23%, 17%, 17%, and secondary patency rates were 63%, 60%, 34%, 34%.
CONCLUSION: Implantation of Dacron-covered stent-grafts for treatment of femoropopliteal lesions leads to high early and late restenosis rates, with a considerable rate of complications, such as fever and pain.
© RSNA, 2002
Index terms: Arteries, extremities, 92.1286, 92.4522 • Arteries, grafts and prostheses, 92.1286, 92.4522 • Arteries, stenosis or obstruction, 92.721 • Interventional procedures, 92.1286, 92.4522
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INTRODUCTION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTS DISCUSSIONREFERENCES |
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The fabric of nitinol and Dacron was expected to help healing more than metal and to prevent neointimal proliferation inside the lumen. Another advantage of the nitinol stent-graft is its relatively good visualization at magnetic resonance angiography (13,14).
However, doubts have arisen concerning long-term patency rates of Dacron-covered stent-grafts (4,5,12,15), but long-term follow-up data have remained scarce. Furthermore, postprocedural vascular inflammation at the dilated segment, usually referred to as "postimplantation syndrome" (11), with noninfectious fever and local pain, occurred in as many as 50% of cases (4,8,11) and caused prolonged hospitalization (11) in these patients.
The aim of the present study was to assess immediate and long-term outcome after femoropopliteal implantation of a Dacron-covered stent-graft in patients with peripheral arterial disease.
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MATERIALS AND METHODS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTS DISCUSSIONREFERENCES |
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The Dacron-covered stent-graft (Cragg Endopro System 1, MinTec, Freeport, Bahamas; currently, Passager, Boston Scientific, Natick, Mass) is a flexible self-expanding endoprosthesis made of nitinol wire, a nickel-titanium alloy, covered with an ultrathin (0.1-mm) prosthetic graft of Dacron with the stent serving as an endoskeleton. The fabric is coated with low-molecular-weight heparin on the endoluminal surface. The structure of the Dacron-covered stent-graft is formed with a 0.28-mm-diameter monofilament of nitinol shaped into a tube with a series of longitudinal zigzags that are stabilized with a ligature of 7.0 polypropylene. The Dacron is attached to the nitinol stent-graft with the same ligatures of polypropylene that are used to stabilize the zigzag loops. After deployment, only a slight foreshortening (7%) occurs at the designated diameter of 5 or 6 mm (16).
The Rutherford classification was used to categorize the clinical stage of peripheral arterial disease (17). At the time of the patient’s hospital admission, atherothrombotic risk factors and comorbidities, as well as standardized physical examination findings, were recorded. All clinical data and clinical staging of peripheral arterial disease were evaluated in all patients with the supervision of one physician (E.M.).
At initial presentation, 23 patients (77%) had Rutherford stage II disease. Rutherford stage III disease was found in two patients (7%); Rutherford stage IV, in four patients (13%); and Rutherford stage V, in one patient (3%). Patient characteristics are presented in Table 1. The mean length of the target lesions was 8.5 cm ± 3.5. In 21 patients (70%), vessel occlusions were recanalized; nine patients had high-grade stenosis (mean grade, 90% ± 5). Two crural runoff vessels were present in 23 patients (77%), one crural runoff vessel in seven patients (23%), and three crural vessels in no patients.
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Once the stent-graft was in place and expanded, a percutaneous transluminal angioplasty balloon catheter was inflated with high pressure (14 atm) to remove any wrinkle in the fabric and seal the stent-graft with the vessel wall. The diameter of the percutaneous transluminal angioplasty balloon corresponded to the diameter of the stent-graft. When several stent-grafts were used, an overlap of at least 5 mm was attained. Length and grade of the target lesion and number, diameter, and length of implanted stent-grafts were recorded. A final angiogram (Iopamiro [300 mg/mL]; Gerot, Vienna, Austria) was obtained to assess stent-graft positioning and any residual stenosis. All procedures were performed by two authors (R.A., E.M.).
Anticoagulation
Treatment with 100 mg of acetylsalicylic acid daily was started before intervention and continued during follow-up. During the procedure, 5,000 IU of heparin was administered intraarterially after insertion of the introducer sheath. After implantation of the Dacron-covered stent-graft, heparin was continuously administered intravenously immediately after removal of the arterial sheath. The heparin dose was adjusted to achieve therapeutic prolongation (two- or threefold) of the activated partial thromboplastin time until oral anticoagulation results with phenprocoumon were in the therapeutic range (international normalized ratio, or INR, 2.0–3.0). The oral anticoagulant was continued for 6 months.
Technical Success and Follow-up
Technical success was defined as accurate positioning of the stent-graft within a 5-mm variability and residual stenosis of less than 30% reduction in vessel diameter. Primary patency was defined as continuous patency without recurrent stenosis of more than 50% at the treated segment and without secondary intervention. Secondary patency was defined as patency after secondary intervention, regardless of what the secondary intervention was, between stent-graft implantation and last follow-up. Restenosis was defined as 50% diameter reduction at the segment of the vessel with the stent-graft, as measured with color-coded duplex ultrasonography (US) with a 5-MHz linear-array color probe (XP 10; Acuson, Mountain View, Calif) and, if available, follow-up angiography performed according to our protocol.
The maximum peak systolic velocity in the dilated region was compared with the peak systolic velocity in the preceding normal segment. A focal increase in the peak systolic velocity of at least 140%, which corresponds to a peak velocity ratio at least 2.4, was considered indicative of a stenosis greater than 50% at that site (18). The presence and diameter of a hypoechogenic rim around the stent-graft was documented. All duplex US examinations were performed by a medical technician supervised by one physician (E.M.).
Routinely, all patients underwent ankle-brachial index measurement and duplex US at baseline and at 24 hours after the intervention. Duplex US was used to evaluate the adequacy of inflow. Furthermore, laboratory tests for signs of inflammation, including C-reactive protein level, complete blood cell count, and body temperature, were performed at 24 hours and, if elevated, daily until hospital discharge. Patient symptoms—in particular, duration of pain at the site of stent-graft implantation—were recorded.
Follow-up
Patients were followed up at the outpatient ward of the angiology department at 1, 3, 6, 12, 18, and 24 months, and then annually. Routine duplex US was performed at each visit for the first 36 months. After 36 months, duplex US was performed only in cases of deterioration of the ankle-brachial index of more than 0.15 or clinical suspicion for restenosis. All patients underwent follow-up angiography after 6 months. Repeat angiography was performed in only cases in which there was evidence of restenosis at duplex US.
Statistical Analysis
Continuous data were presented as the mean ± SD or as the mean and 95% CI. Percentages were calculated for dichotomous variables. Paired t tests were used for comparison of continuous paired variables. Life table analysis was performed to assess primary and secondary patency rates after stent-graft implantation. The rate of restenosis was presented as a Kaplan-Meier curve by means of the log-rank test to compare primary and secondary patency rates. All P values were two-tailed. Differences with a P value less than .05 were considered statistically significant. Calculations were performed by using commercially available software (Excel for Windows, version 97, Microsoft, Redmond, Wash; SPSS for Windows, version 10.0, SPSS, Chicago, Ill).
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RESULTS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTS DISCUSSIONREFERENCES |
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In 25 patients (83%), clinical improvement by at least one Rutherford stage was observed 24 hours after intervention; in five patients (17%), the clinical stage remained unchanged after intervention. In these five patients, early recurrent occlusion due to stent-graft thrombosis occurred within the first 24 hours after implantation.
After implantation, 12 patients (40%) developed noninfectious fever. Maximal body temperature in these patients was a mean of 38.2°C ± 0.4, and the duration of elevated temperature was a mean of 2.8 days ± 1.7. White blood cell count increased from a baseline mean of 8.2 x 109/L ± 2.0 to a mean of 12.7 x 109/L ± 4 at 1 day after the intervention (mean increase, 54%; P < .001). Maximum postintervention C-reactive protein level was a mean of 123 mg/L ± 5, which is an increase of 1,175% (mean baseline C-reactive protein level, 1.5 mg/dL ± 2.2). After intervention, 17 patients (57%) reported pain at the site of implantation (mean, 5 days; range, 2–28 days).
At discharge, 28 patients received the planned antithrombotic regimen with 100 mg of acetylsalicylic acid daily and phenprocoumon (mean international normalized ratio, 2.7 ± 0.3). In two patients, bleeding complications occurred during the initial hospital stay, and phenprocoumon had to be stopped. Neither of these patients had early restenosis, but one experienced recurrent stenosis after 18 months.
Follow-up
The mean follow-up was 60 months ± 10. Follow-up duplex US results demonstrated a hypoechogenic perivascular rim as large as 4 mm in diameter around the stent-graft. The hypoechogenic rim was found in all patients 24 hours after intervention, with a mean diameter of 0.8 mm ± 0.5 that increased to a mean of 2 mm ± 1 at 1 month after intervention. Thereafter, the diameter of the hypoechogenic rim decreased until 6 months after the intervention to a mean of 1 mm ± 0.5 (Fig 1). However, there was no association found between the diameter of the rim and laboratory parameters for inflammation or the rate of restenosis.
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In 25 patients (83%), restenosis occurred during follow-up; 50% of cases occurred within the first 3 months. In one patient, restenosis occurred inside the stent-graft; in the remaining patients, restenosis was located at the proximal or distal edge of the stent-graft (Fig 2).
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DISCUSSION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTS DISCUSSIONREFERENCES |
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Early results and short-term follow-up data seemed promising (5), but long-term follow-up data are not available. However, our findings indicate that Dacron-covered stent-graft implantation in the femoropopliteal segment for treatment of peripheral arterial occlusive disease is associated with high rates of early and late restenosis and a considerable frequency of postimplantation syndrome with noninfectious fever and local pain. Implantation of other covered stent-grafts in the femoropopliteal vessel segment was also associated with a considerable rate of complications (as high as 50%) and primary patency rates below 50% within 2 years (19,20). Therefore, the use of covered stent-grafts in nonaneurysmal femoropopliteal disease should be avoided.
After Dacron-covered stent-graft implantation, the postimplantation syndrome occurred in 40% of the patients in this series, which is in accordance with previous observations (4,8,11). Fever and elevation of leukocyte and C-reactive protein levels may be caused by a progressive perivascular inflammatory reaction at the site of implantation (21). In the present study, a hypoechogenic rim around the stent-graft was found at duplex US examination within the first months after implantation. Similarly, histologic evaluation after implantation of Dacron-covered endoprostheses has demonstrated an increased inflammatory vessel wall reaction (22). This inflammatory reaction might contribute to frequent recurrent occlusion, since inflammation is suggested to be a cornerstone of the process of restenosis (3,23–28).
Furthermore, in our study, 57% of patients reported persistent pain at the site of stent-graft implantation. This pain might be due to arterial wall ischemia related to the covering of the intima (29) or to local perivascular inflammation. Therefore, in a recently published article (30) concerning animal models, concerns regarding the safety of the device have been raised. Besides vascular ischemia (29) or inflammatory reaction to Dacron (22), the heparin treatment of the stent-graft may also be involved in the extent of postimplantation syndrome. Plain Dacron-covered stent-grafts generated a less extensive inflammatory response as compared with that with heparin-coated stent-grafts (21). It remains unclear whether treatment of larger vessels, such as the iliac segment, is connected to a substantially lower rate of early complications and postimplantation syndrome; however, it seems that the site of implantation may lead to variance in inflammation.
Early stent-graft thrombosis within the first 24 hours was found in 17% of the patients in this study, although all stent-grafts were heparin coated, and the strictly used anticoagulant regimen included a combination of acetylsalicylic acid and a full dose of intravenously administered heparin. It seems that intravascular stent-graft placement in the femoropopliteal arteries is an important trigger for thrombus formation. Immediate and late results after iliac implantation were considerably better (6,29) than patency rates after femoropopliteal implantation (4,5,8,10,11). Larger vessel diameters and altered flow or vessel wall characteristics in the iliac arteries may cause the better outcome. However, we found low intermediate and long-term patency rates in the femoropopliteal segment that are comparable with other published data (4,31).
In contrast to our findings, Henry et al (5,8) found acceptable secondary 2-year patency rates as high as 80% after femoropopliteal implantation. Their results were derived from clinical and hemodynamic follow-up findings. In our study, grading at duplex US was more accurate to identify recurrent stenosis, which may explain the higher rates in our study.
Restenosis of the Dacron-covered device occurred typically at the edges of the endograft, which is a major shortcoming of this method with respect to long-term patency. As compared with the edges of noncovered stent-grafts, the edges of the heparin-coated Dacron-covered stent-grafts show significantly increased neointimal thickening and inflammatory reaction (22,32). If stent-graft placement is indicated in the femoropopliteal segment (eg, in cases with primarily suboptimal results at percutaneous transluminal angioplasty), use of noncovered stent-grafts should be preferred for peripheral occlusive disease. However, covered stent-grafts are indicated for treatment of peripheral aneurysmal disease and in some cases after traumatic arterial injury.
In conclusion, inflammatory postimplantation syndromes with fever and local pain occur frequently after implantation of this Dacron-covered stent-graft. A high rate of early thrombosis and high early and late rates of restenosis at the ends of the device make this Dacron-covered stent-graft unacceptable for treatment of femoropopliteal arterial occlusive disease. The problems with this device are probably related to the inflammatory response to Dacron and possibly to the adjunctive heparin with which the Dacron is treated. Trauma at the ends of the prosthesis during implantation may be the cause for restenosis at this location.
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FOOTNOTES |
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REFERENCES |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTS DISCUSSIONREFERENCES |
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This article has been cited by other articles:
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  E. Hager, R. A. Larson, P. J. DiMuzio, and J. V. Lombardi New Techniques and Developments of Stenting for Infrainguinal Arterial Occlusive Disease: Are the Results Any Better Than Balloon Angioplasty Alone? Perspectives in Vascular Surgery and Endovascular Therapy, September 1, 2007; 19(3): 300 - 306. [Abstract] [PDF]
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 T. Zeller Current state of endovascular treatment of femoro-popliteal artery disease Vascular Medicine, August 1, 2007; 12(3): 223 - 234. [Abstract] [PDF]
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 E. Archondakis, G. Pero, L. Valvassori, E. Boccardi, and G. Scialfa Angiographic Follow-Up of Traumatic Carotid Cavernous Fistulas Treated with Endovascular Stent Graft Placement AJNR Am. J. Neuroradiol., February 1, 2007; 28(2): 342 - 347. [Abstract] [Full Text] [PDF]
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C. Klonaris, A. Katsargyris, A. Giannopoulos, and E. Bastounis Advances in Endovascular Treatment of Femoropopliteal Arterial Occlusive Disease Perspectives in Vascular Surgery and Endovascular Therapy, December 1, 2006; 18(4): 329 - 341. [Abstract] [PDF]
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 M. A. Mauro The Battle of Intimal Hyperplasia in the War against Femoropopliteal Disease Radiology, May 1, 2004; 231(2): 299 - 301. [Full Text] [PDF]
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