Femoropopliteal bypass with externally supported knitted Dacron grafts: A follow-up of 200 grafts for one to twelve years

Femoropopliteal bypass with externally supported knitted Dacron grafts: A follow-up of 200 grafts for one to twelve years Sherif EI-Massry, MD, Ehab Saad, MD, Lester R. Sauvage, MD, Michael Zammit, MD, James C. Smith, MD, Christopher C. Davis, MD, Edward A. Rittenhouse, MD, and Lloyd D. Fisher, PhD, Seattle, Wash. Purpose: This article reports our experience with externally supported, preclotted knitted Dacron grafts in femoropopliteal bypass. Methods: This is a retrospective analysis of a consecutive series of 154 patients who received 200 grafts (175 above knee and 25 below knee). Follow-up extended to 12 years (mean 59 112 months). Results: Primary patency rates for the entire series were 75%, 70%, and 47% at 3,5, and 10 years, respectively. Above-knee grafts had 76%, 71%, and 50% rates and 3, 5, and 10 years, respectively. Below-knee grafts had 65% and 57% at 3 and 5 years, respectively. Limb-salvage rates were 87%, 79%, and 73% at 3, 5, and 10 years, respectively, for the 57 limbs operated on because of critical ischemia. The most significant predictor of graft failure was poor runoff as determined by preoperative arteriography. The effect of poor runoff was most pronounced in the first 3 months. Conclusion: Externally supported, preclotted knitted Dacron grafts provide encouraging primary patency rates for above-knee femoropopliteal bypass. Poor leg vessel runoff is a major determinant of early graft failure. (J VAse SURG 1994;19:487-94.)

Femoropopliteal bypass remains the most effective treatment for symptomatic superficial femoral artery occlusive disease that fails to respond to conservative measures. 1 In this setting the use of prosthetic grafts is generally reserved for patients with no available vein, although some consider polytetrafluoroethylene (PTFE) grafts an acceptable or even preferable alternative for primary above-knee bypasses. 2,3 In this article we present our experience with 200, 6 mm externally supported knitted Dacron grafts for femoropopliteal bypass. The follow-up extended to 12 years (mean 591/2 months), with eight grafts still patent at more than 10 years. PATIENTS AND METHODS From January 1978 through December 1990, 154 patients (44 women and 110 men) received 200 From the Hope Heart Instimte, the Providence Medical Center, and the Departments of Surgery and Biostatistics, University of Washington, Seattle. Reprint requests: Lester R. Sauvage, MD, The Hope Heart Instimte, 528 18th Ave., Seattle, WA 98122. Copyright © 1994 by The Society for Vascular Surgery and International Society for Cardiovascular Surgery, North American Chapter. 0741-5214/94/$3.00 + 0 24/1/47898

femoropopliteal bypasses with 6 mm diameter, externally supported, preclotted knitted Dacron grafts. For the purpose of this study, follow-up terminated on June 30, 1992. Follow-up extended to 154 months (mean 591/2 months). Indications for operation were disabling claudication (143 grafts) and limb salvage (57 grafts). The mean preoperative ankle-arm index was 0.57 for patients with claudication and 0.15 for patients with critically ischemic legs. Patients who had disabling claudication had failed conservative therapy (smoking cessation and graded exercise), manifesting either no improvement of the disabling claudication or actual deterioration limiting their walking ability to less than 100 feet. Patient ages ranged from 41 to 90 years with an average of 67 ± 9 years. Sixty-eight percent of patients had a history of smoking, 61 % hypertension, 57% coronary heart disease, 19% cerebrovascular insufficiency, and 23% diabetes mellitus. In most instances, prosthetic grafts were used preferentially in above-knee bypasses, in contrast to below-knee bypasses, where their use was obligatory because of lack of good saphenous vein. During the same time interval as this study, 33 above-knee and 80 below-knee femoropopliteal reconstructions and 487

488 Et-Massry et at.

130 femorotibioperoneal reconstructions were done with autologous veins. Grafts were preclotted by the four-step technique of Yates et al. 4 and placed in the subsartorial tunnel. The proximal anastomosis was made to the common femoral artery in 153 grafts or the distal end of an inflow bypass in 47 grafts (aortofemoral 36, axillofemoral 4, and femorofemoral 7). Distal anastomosis was made to the above-knee popliteal artery in 175 grafts and the below-knee popliteal artery in 25 grafts. Concomitant inflow procedures were done in 30 cases (19 aortobifemoral, 4 axillofemoral, 6 femorofemoral, and 1 common iliac artery endarterectomy). Endarterectomies of common femoral or popliteal arteries were necessary in 15 cases. Heparin in a dosage of 2 to 3 mg/kg body weight was routinely administered before application of vascular clamps. Intraoperative monitoring of activated clotting time determined the need for additional heparin. Anastomoses were made with either interrupted 4-0 or 5-0 Tycron or continuous 5-0 Prolene. Twentynine grafts were implanted as redo procedures. The proximal anastomosis was made to the ringed portion of the graft in 77% of cases and to the nonsupported portion in 23%. Popliteal anastomoses were made to the ringed portion of the graft in 38% of cases and to the nonsupported portion of the graft in 62%. Completion angiograms of the distal anastomosis and runoff were obtained routinely. Operative flows were measured several minutes after the clamps were released with an electromagnetic flowmeter (model FM 501; Carolina Medical Electronics, Inc., King, N.C.). These patients received 500 rnl dextran 40 during surgery and 20 ml/hr thereafter for the next 3 days. The senior author (L.R.S.) has used this regimen for the past 20 years because dextran 40 appeared to offer protection against immediate postoperative thrombosis without substantially increasing the risk of hemorrhage. This view was recently supported in a randomized prospective trial of Rutherford et al. 5 All patients were instructed to take aspirin (325 mg/day) after surgery, unless contraindicated by gastrointestinal intolerance. Patients were evaluated every 6 months by clinical examination, with special attention to symptom progression, walking ability, palpation of pulses below the distal anastomosis, and auscultation for murmurs. Insonation of the graft with a hand-held Doppler and measurement of the ankle pressures were done routinely. A palpable distal pulse or stable elevation of the ankle-arm index by at least 0.15 above the preoperative value was considered indica-

JOURNAL OF VASCULAR SURGERY March 1994

tive of graft patency. If there were doubts about graft patency an angiogram was obtained. Statistical analysis. Graft patency rates were calculated with the Kaplan-Meier estimator. Differences between subgroups were evaluated for equality with the Mantel-Cox test. Age at time of surgery (stratified to < 65 and ~ 65 years), gender, history of coronary heart disease, hypertension, smoking, diabetes, cerebrovascular disease, indications for operation, level of distal anastomosis, prior ipsilateral bypass procedures, and state of distal runoff were evaluated as potential risk factors for graft closure (200 grafts), limb loss (57 limbs), and death (154 patients) according to the Cox proportional hazards model. Distal runoff was considered good if there were two or three leg vessels in direct continuity with an open popliteal artery, visualized in the preoperative arteriogram (available for assessment for all 200 procedures) for two thirds of their course in the leg. Operative flows for different subgroups were compared for equality with the unpaired two-tailed t test and Mann-Whitney U statistics (Wilcoxon test). The guidelines of the Ad Hoc Committee on Reporting Standards of Peripheral Vascular Disease were followed. 6 RESULTS Morbidity and mortality rates. There were no intraoperative deaths; however, two patients (1.3%) died within 30 days of surgery. An additional 51 patients died of causes not related to surgery during the follow-up period. Coronary artery disease accounted for 58% of the deaths. Age of 65 years or greater (p = 0.04) and presentation with threatening limb loss (p = 0.003) were significant predictors for death. The 5- and 10-year actuarial survival rates of the 154 patients were 70% and 44%, respectively (Fig. 1). Wound complications included two instances of hemorrhage requiring prompt surgical control and five instances of hematoma necessitating surgical evacuation within the first few days after surgery. Superficial wound infection was diagnosed in 11 cases and lymphatic collections in 16 cases. These cases were managed conservatively without sequelae. Seven wounds developed slough of the skin flap and required surgical debridement; four required skin grafting. One graft became infected after thrombectomy and was successfully replaced. Graft patency. There were 69 graft closures during the follow-up period. Thirteen closures (19%) occurred by 3 months and 31 (45 %) by the end of the first year. Of all the risk factors studied, the

JOURNAL OF VASCULAR SURGERY Volume 19, Number 3

El-Massry et al.

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Table 1. Analysis of potential risk factors for graft closure with the Cox proportional hazards model

p Value Variable

Univariate

Multivariate

Age Sex Atherosclerotic heart disease Hypertension Diabetes mellitus Smoking Cerebrovascular disease Presentation Distal anastomosis (above knee vs below knee) Previous failed bypass graft Leg vessel runoff

0.066 0.476 0.967 0.762 0.108 0.368 0.942 0.676 0.247 0.832 0.009

0.117 0.370 0.759 0.540 0.079 0.204 0.550 0.509 0.037 0.487 0.001

most significant predictor of graft closure was poor leg vessel runoff (p = 0.009) (Table I). Primary patency rates for the 200 grafts were 75 % at 3 years, 70% at 5 years, and 47% at 10 years (Fig. 2). For the 175 above-knee grafts (58 closures), the rates were 76% at 3 years, 71% at 5 years, and 50% at 10 years, compared with 67% at 3 years and 57% at 5 years for the 25 grafts (11 closures) implanted below the knee (p = 0.086, log rank test) (Fig. 3). For the 143 grafts implanted because of severe claudication (51 closures), the primary patency rates were 76% at 3 years, 73% at 5 years, and 44% at 10 years, and grafts required for limb salvage (57 grafts; 18 closures) had a 3-year primary patency rate of70% and a 5-year rate of 55% (p = 0.82, log rank test) (Fig. 4). For the 129 grafts implanted above the knee

for severe claudication (44 closures), the 5-year patency rate was 74%, compared with 58% for the 46 grafts implanted above the knee for limb-salvage indications (14 closures) (p = 0.84, log rank test). Grafts with good runoff (136 grafts; 42 closures) had primary patency rates of 79% at 3 years, 75 % at 5 years, and 51 % at 10 years compared with 65% at 3 years and 57% at 5 years for 64 grafts with poor runoff (64 grafts; 27 closures) (p = 0.008, log rank test) (Fig. 5). Exclusion of the first 3 months resulted in loss of any significant difference in patency rates related to runoff (p = 0.16), whereas exclusion of the first 6 months resulted in almost parallel patency curves (p = 0.93) (Fig ..6). Grafts implanted above the knee with good runoff (115 grafts; 33 closures) had primary patency rates of 80% at 3 years, 77% at

JOURNAL OF VASCULAR SURGERY March 1994

490 El-Massry et al.

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Fig. 3. Cumulative primary patency rates of above-knee versus below-knee grafts. Broken line indicates SE of 10% or greater.

5 years, and 56% at 10 years, compared with 66% at 3 years and 57% at 5 years for the above-knee grafts with poor runoff (60 grafts; 25 closures) (p = 0.007, log rank. test). Grafts implanted below the knee with good runoff (21 grafts; 9 closures) had primary patency rates of 69% at 3 years and 59% at 5 years. These rates were not significantly different from those for grafts implanted above the knee with good runoff (p = 0.137, log rank. test). Of the four grafts with poor runoff implanted below the knee, two grafts occluded, at 2 weeks and 1 year, respectively.

Grafts with both anastomoses to the supported portion of the graft (42 grafts; 19 closures) had patency rates not significantly different from those of grafts with both anastomoses to the nonsupported portion of the graft (46 grafts; 25 closures) (p = 0.25, log rank. test). Grafts implanted as a redo procedure (29 grafts; 10 closures) had primary patency rates not significantly different from those of grafts implanted primarily (171 grafts; 59 closures) (p = 0.86, log rank. test). Limb salvage. Fourteen patients lost 16 limbs

JOURNAL OF VASCULAR SURGERY Volume 19, Number 3

El-Massry et al.

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Fig. 4. Cumulative primary patency rates of grafts implanted in patients with claudication versus patients undergoing limb-salvage procedures. Broken line indicates SE of 10% or greater.

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after repeated revascularization procedures. Two patients undergoing limb-salvage procedures later underwent bilateral amputations. The most significant predictor of limb loss was poor leg vessel runoff (p = 0.003). Of the 57 limbs operated on for critical ischemia (10 amputations), the actuarial limb salvage rates were 87% at 3 years, 79% at 5 years, and 73% at 10 years (Fig. 7). Of the 135 limbs operated on for severe claudication, six limbs were lost after failure of repeated revascularization procedures. The actuarial risk of limb loss among patients operated on for

severe claudication was 3% at 5 years and 9% at 10 years. Operative flows. Grafts with good runoff had a mean operative flow rate of 240.1 ± 138 ml/min compared with 174 ± 108 ml/min for grafts with poor runoff (p = 0.003, t test; p = 0.002, MannWhitney test). The mean values of operative flow rates for grafts that closed during the first month (p = 0.74), 2 months (p = 0.86), or 3 months (p = 0.63) were not significandy different from those of the rest of the grafts.

JOURNAL OF VASCULAR SURGERY March 1994

492 EI-Massry et al.

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DISCUSSION If the primary patency rate of a synthetic graft in the above-knee femoropopliteal position closely approximates that of a saphenous autograft, the prosthesis may be used preferentially to preserve the vein for use in more demanding locations, such as below the knee or in the coronary arteries, should the need arise. Taylor and Porter/ have reported an 88% primary patency rate at 5 years with good-quality saphenous vein grafts in the above-knee position. However, in three recent well-controlled multicenter

clinical trials of above-knee grafts, saphenous veins achieved primary patency rates of 62% at 3 years, 61 % at 4 years, and 59% at 5 years. S•lO The only acceptable method of comparing two types of grafts is a well-controlled prospective trial. Unfortunately, no randomized prospective comparisons of expanded PTFE and knitted Dacron grafts have been performed. The 5-year primary patency rates of expanded PTFE grafts for above-knee femoropopliteal bypass in retrospective reports have ranged from 42% to

JOURNAL OF VASeULAR SURGERY Volume 19, Number 3

62%.2,3,11 However, the 5-year primary patency rates of expanded PTFE in three randomized, wellcontrolled, prospective trials in the above-knee position have been remarkably similar, 38% to 39%.S,9,12 The 5-year primary patency rates reported in this study with 6 mm diameter externally supported knitted Dacron grafts were 74% for relief of severe claudication, with 51 grafts at risk, and 55% for limb salvage, with 9 grafts at risk. This difference is not statistically significant. In two reports of the same graft, Matsubara et al. 13 reported a 4-year primary patency rate of 71 % for above-knee femoropopliteal bypass 13 and Kremen et al,l4 reported a 91% cumulative patency rate at 11/2 years. Unfortunately, these two studies did not provide longer-term follow-up. These results suggest that externally supported, preclotted knitted Dacron has improved patency rates compared with crimped Dacron. 15 ,16 The external support enables use of a noncrimped graft without danger of kinking in the femoropopliteal position. When the knee is flexed, the tibia rotates so far posteriorly on the femoral condyles that even the above-knee poplital artery moves upward. The supported graft compensates for the reduced distance by assuming an S-shaped configuration, the only conformational change allowed by the support coil. In addition, in an experimental canine model we have observed that the noncrimped graft is more resistant to development of thrombosis than a crimped graft. 17 Pevec et al. 1S have recently reported a 5-year primary patency rate of 48% for nonsupported knitted Dacron femoropopliteal grafts, whereas expanded PTFE grafts had a 5-year primary patency rate of 27% (p = 0.009). Johnson et al. 9 have reported a 60% 5-year primary patency rate with the Dardik human umbilical vein graft in the above-knee femoropopliteal position. A limitation to the use of these grafts in patients with a life expectancy longer than 3 to 5 years is their high likelihood of developing aneurysmal changes. 19 The only study that has compared externally supported knitted Dacron with the Dardik graft was in the below-knee femoropopliteal position, predominantly for relief of critical ischemia (78% of cases); it revealed a 2-year primary patency rate of 57% for the Dacron grafts and 39% for the umbilical vein grafts (p = 0.001).20 Our study has shown lower operative flow rates in the grafts of patients with poor distal runoff than in the grafts of patients with good runoff. An analysis of conventional risk factors (Table I) showed that poor distal runoff had the most significant relationship to

Et-Massry et at.

493

graft closure, strongest in the first 3 months. After 6 months, the patency curves for grafts with good and poor distal runoff became parallel and remained so thereafter (Fig. 5). This suggests that there are factors other than those considered in Table I that may have a significant influence on the patency of femoropopliteal grafts. In a prior study we observed that high platelet aggregability exerted a direct and dominant influence on the patency rates of 4 mm diameter knitted Dacron grafts in the canine carotid artery.21 A similar direct and dominant relationship for femoropopliteal grafts has been observed in humans. 22 Although the results we have reported in this article were obtained without benefit of this new information, our current policy is to use 6 mm externally supported, preclotted knitted Dacron grafts preferentially for above-knee femoropopliteal bypass if the patient's platelet aggregability is either naturally low or can be lowered pharmacologically. Under these circumstances even higher primary patency results than those reported in this article could be expected. If high platelet aggregability is present and cannot be reduced, we use a good saphenous autograft (if one is available) for aboveknee bypass. If a good vein is not available, we would restrict operative intervention to patients with impending limb loss. We recommend a good saphenous graft for below-knee bypass. However, if the clinical need for a below-knee femoropopliteal bypass is great, we would use an externally supported, preclotted knitted Dacron graft with adequate antiplatelet therapy in the absence of a good vein.

REFERENCES 1. Moore WS. Therapeutic options for femoropopliteal occlusive disease. Circulation 1991;83(suppl):I-91-3. 2. Moore WS, Quifiones-Baldrich WJ. An argument against all-autogenous tissue for vascuJar bypasses below the inguinal ligament. Adv Surg 1991;24:91-101. 3. Patterson RB, Fowl RJ, Kempczinski RF, Gewirtz R, Shukla R. Preferential use of ePTFE for above-knee femoropopliteal bypass grafts. Ann Vasc Surg 1990;4:338-43. 4. Yates SG, Barros D'Sa AAB, Berger K, et al. The preclotting of porous arrerial prostheses. Ann Surg 1976;188:611-22. 5. Rutherford RB, Jones DN, Bergentz S-E, et al. The efficacy of dextran 40 in preventing early postoperative thrombosis following difficult lower extremity bypass. J VASC SURG 1989;1:765-73. 6. Ad Hoc Committee on Reponing Standards, Society for Vascular SurgeryjNorrh American Chapter, International Society for CardiovasculaT Surgery. Suggested standards for reports dealing with lower extremity ischemia. J V ASC SURG 1986;4:80-94. 7. Taylor LM, Porter JM. Clinical and anatomic considerations

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for surgery in femoropopliteal disease and the results of surgery. Circulation 1991;83(suppl):I-63-9. 8. Veith FJ, Gupta SK, Ascer E, et al. Six-year prospective multicenter randomized comparison of autologous saphenous vein and expanded polytetrafluoroethylene grafts in infrainguinal arterial reconstructions. J VASe SURG 1986;3:104-14. 9. Johnson WC, Lee KK, VA Cooperative Study Group No. 141. Comparative evaluation ofPTFE, HUV and saphenous vein bypasses in fern-pop AK vascular reconstruction [Abstract]. J VASe SURG 1992;15:1070-1. 10. McCollum C, Alexander C, Kenchington G, Franks PI, Greenhalgh R. PTFE or HUV for femoro-popliteal bypass: a multicentre trial. J VAse SURG 1991;13:150-62. 11. Quifiones-Baldrich WI, Prego AA, Ucelay-Gomez R, et al. Long-term results of infrainguinal revascularization with polytetrafluoroethylene: a ten-year experience. J VAse SURG 1992;16:209-17. 12. Aalders GJ, van Vroonhoven TJMV. Polytetrafluoroethylene versus human umbilical vein in above-knee femoropopliteal bypass: six-year results of a randomized clinical trial. J VASe ·SURG 1992;16:816-24. 13. Matsubara I, Nagasue M, Tsuchishima S, Nakatani B, Shimizu T. Clinical results of femoropopliteal bypass using externally supported (EXS) Dacron grafts: with a comparison of above- and below-knee anastomosis. J Cardiovasc Surg 1990;31:731-4. 14. Kremen AF, Mendez-Fernandez MA, Geis RC, Henly WS. The Dacron EXS graft: patency in femoropopliteal and femorotibial surgery. J Cardiovasc Surg 1986;27: 125-30. 15. Yashar JJ, Thompson R, Burnard RJ, Weyman AK, Yashar I, Hopkins RW. Dacron vs vein for femoropopliteal arterial

16.

17.

18.

19.

20.

21.

22.

bypass: should the saphenous vein be spared? Arch Surg 1981;116:1037-40. Rosenthal D, Evans RD, McKinsey J, et al. Prosthetic above-knee femoropopliteal bypass for intermitrent claudication. J Cardiovasc Surg 1990;31:462-8. Sauvage LR, Walker MW, Berger K, et al. Current arterial prostheses: experimental evaluation by implantation in the carotid and circumflex coronary arteries of the dog. Arch Surg 1979;114:687-91. Pevec WC, Darling C, L'Italien GJ, Abbotr WM. Femoropopliteal reconstruction with knitred, nonvelour Dacron versus expanded polytetrafluoroethylene. J VASe SURG 1992; 16:60-5. Dardik H, Miller N, Dardik A, et al. A decade of experience with the glutaraldehyde-tanned human umbilical cord vein graft for revascularization of the lower limb. J VAse SURG 1988;7:336-46. Clifford PC, Gazzard V, Lawrance RJ, Clyne CAC, Webster JHH. Below knee femoropopliteal bypass in severe ischemia: results using EXS Dacron and human umbilical vein. Ann R Coll Surg EngI1986;68:319-21. Kaplan S, Marcoe KF, Sauvage LR, et al. The effect of predetermined thrombotic potential of the recipient on small-caliber graft performance. JVAse SURG 1986;3:311-21. Saad EM, Kaplan S, El-Massry S, et al. Platelet aggregation index accurately predicts patency of externally supported knitred Dacron femoropopliteal bypass grafts. J VASe SURG 1993;18:587-95.

Submitted Feb. 9, 1993; accepted April 11, 1993.