Influence of vein size (diameter) on infrapopliteal reversed vein graft patency

Transcription

1 Influence of vein size (diameter) on infrapopliteal reversed vein graft patency Kurt R. Wengerter, MD, Frank J. Veith, MD, Sushil K. Gupta, MD, Enrico Ascer, MD, and Steven P. Rivers, MD, New York, N.Y. We reviewed 239 infrapopliteal reversed greater saphenous vein graft bypasses placed for critical ischemia over a 7-year period to determine the influence of vein diameter on graft patency and limb salvage. Grafts were assigned to four groups based on the minimum external diameter measured during operation: <3.0 mm, n = 18; 3.0 mm, n = 59; 3.5 mm, n = 67; and ->4.0 mm, n = 145. A pattern of increasing graft patency and limb salvage among the four groups was noted as the minimum external diameter increased from <3.0 mm to ram. When compared to the larger grafts i>4.0 mm, primary graft patency was significantly lower both for <3.0 mm grafts (0% for <3.0 mm vs 65% for i>4.0 mm at 3 years, p < 0.001) and for long (>45 cm) 3.0 mm grafts (38% for long 3.0 mm vs 75% for ->4.0 mm at 2 years, p < 0.005). All 3.5 mm and short (<45 cm) 3.0 mm grafts had patency rates similar to t>4.0 mm veins. Thus long 3.0 mm and all less than 3.0 mm reversed saphenous vein grafts should be considered at high risk for failure. Veins with fibrotic, thick-waued segments identified during operation (n = 19) had patency rates significantly lower than nonfibrotic veins (n = 270;p < 0.01), and this may play a role in the failure of some <3.0 mm minimum external diameter vein grafts. (J VA$C SURG 1990;i1: ) Diameter is widely accepted as an important factor in determining vein graft patency. However, most studies addressing the importance of vein diameter have dealt with femoropopliteal reconstructions. Early reports suggested that 4.0 mm was the smallest acceptable diameter for femoropopliteal 1 and femorodistal 2 vein bypass grafts, but these initial reports lacked accurate correlations of patency with vein size. Later studies correlating patency of femoropopliteal bypass grafts with vein diameter showed that veins as small as 3.5 mm s'4 and 3.0 mm 5 achieved Fatency rates comparable to larger (/>4.0 mm) vein grafts. Patency rates of infrapopliteal reversed small diameter (<4.0 mm) vein grafts have more recently been reported to be equal to otherwise similar grafts with a diameter equal to or greater than 4.0 mm, 6 whereas in situ grafts with a diameter less than 3.5 mm can reportedly be used in this fashion with resuks equal to larger diameter in situ veins. 7,8 However, From the Division of Vascular Surgery, Montefiore Medical Center--Albert Einstein College of Medicine. Supported in part by the Manning Foundation, the Anna S. Brown Trust, and the New York Institute for Vascular Studies. Presented at the Third Annual Meeting of the Eastern Vascular Society, Bermuda, May 4-7, Reprint requests: Kurt R. Wengerter, MD, 111 E. 210th St., New York, NY ~j4/6/18327 the lower limit of acceptable diameter has not been defined for either in situ or reversed distal grafts to infrapopliteal arteries. Over the past 5 years we have preferentially used greater saphenous vein and other alternative veins for infrapopliteal bypass graft, and for 2 years before that vein and polytetrafluoroethylene (PTFE) grafts were chosen as part of a prospective randomized study. 9 Although the largest diameter segment of vein was selected preferentially, veins as small as 2.0 mm were sometimes used when no larger vein segment was available. This has provided us with the opporumity to evaluate the influence of vein diameter on the patency of reversed vein bypass grafts to the tibial and peroneal arteries. METHODS A total of 289 reversed greater saphenous vein bypass operations to infrapopliteal arteries with recorded vein diameter measurements were performed at our institution from January 1981 to December The procedures were carried out in 254 patients, of which 60% (152) were men, and 40% (102) were women. Diabetes mellitus was present in 77% of all patients. Limb-threatening ischemia was the indication for the procedure in all cases. Two hundred forty-nine procedures (86%) were performed for tissue necrosis, and 40 (14%) were performed for rest pain; none were performed for clau- 525

2 526 Wengerter et al. Journal of VASCULAR SUKGERY Table I. Grouping of veins by minimum external diameter (MED) Group MED (mm) No. % I < II III IV -> Total dication. Nineteen percent of the procedures were secondary operations in which a prior revascularization had been performed to an infrapopliteal vessel in the same limb. Vein harvest. Selection of the portion of vein to be removed and placement of the incision were aided in the latter 2 years of the study by mapping the course and size of the vein before operation with duplex ultrasonography. In the earlier part of the study venography was performed in reoperative cases only. The techniques of vein harvest have been described previously. ~ Each vein was carefully examined for obstructing lesions, fibrotic segments, and other defects. Vein measurement. The diameter measurement was made by placing a metal ruler directly behind and perpendicular to the vein during distension to a pressure of 100 to 150 mm Hg. Measurements were made at multiple sites, and the largest and smallest values were recorded to the nearest 0.5 mm. To validate and confirm the accuracy of this technique, the diameter of 10 veins was determined at mukiple sites with an accurate ( ram) dial caliper and compared with determinations taken in the same locations by use of the method described. The difference in measurement ranged from less than 1% to 9%, with a mean of 4%. At completion of the procedure the length of the bypass graft was also measured. For data analysis, grafts were assigned to four groups based on their minimum external diameter (MED): I, less than 3.0 mm; II, 3.0 ram; III, 3.5 mm; and IV, equal to or greater than 4.0 mm. Bypass procedures. Sites of origin for the bypass grafts included the common femoral, superficial femoral, deep femoral, popliteal, and tibial arteries.. The distal outflow sites included the tibial arteries, the peroneal artery, and the dorsalis pedis and medial and lateral plantar arteries. Inflow and outflow sites were determined by preoperative angiography performed in all cases. Our surgical techniques and principles of care for infrapopliteal bypass procedures have been previously described, l 'n Completion intraoperative angiography was routinely performed, visualizing the distal anastomosis and the outflow vessels. Antiplatelet therapy was initiated before surgery in all patients, and after surgery all patients were maintained on 650 mg aspirin and 100 mg dipyridamole daily. Follow-up and data analysis. Patient follow-up ranged from 1 month to 7 years, with a mean of 20 months for those with patent grafts. Patency was assessed by pulse examination, segmental pressure measurements, pulse volume recordings, and duplex ultrasonography. Primary graft patency was defined following the criteria of the Ad Hoc Committee on Reporting Standards. 12 Life tables were constructed with standard techniques, 13 and statistical comparisons were carried out with the log rank test. RESULTS Graft diameter. As shown in Table I, 50% ff the procedures were performed with "small" veins, less than 4.0 mm in MED. Sixty-seven veins with an MED of 3.5 mm were used, 59 with an MED of 3.0 mm were used, and 18 veins with an MED of less than 3.0 rnm (2.0 to 2.5 mm) were used. One hundred forty-five veins were equal to or greater than 4.0 mm (4.0 to 6.0 mm) MED. Variables. There were no significant differences between the patients in the MED groups with respect to sex, smoking history, history of diabetes, and history of a prior reconstruction. In addition, none of these variables, nor any combination, were found to be predictive of the presence of small veins. Graft patency. Primary life-table graft patency is shown in Fig. 1 and Table II for each of the vein diameter groups. Graft patency of the four vein diameter groups was found to increase as MED increased. Only 47% of the smallest veins (>3.0 mm MED) remained patent at 6 months, and none remained patent beyond 3 years. The patency rate for these veins was significantly lower than veins equal to or greater than 4.0 mm MED (p < 0.001). Veins with an MED of 3.0 mm also had a significantly lower patency rate (p < 0.005) than did veins equal to or greater than 4.0 ram, although the difference was less marked. Veins with an MED of 3.5 mm had a patency rate slightly but not significantly lower than vein grafts with an MED of equal to or greater than 4.0 mm. Graft length. Patency of vein grafts with an MED of 3.0 mm originating from the popliteal artery

3 Volume 11 Number 4 April 1990 Vein graft diameter 527 Cumulative Patency (%) I00~ I \ "~ ~1~, ~ ~-~-----~,--, oo, 40 ~ ' I ~s 20. p<.o01 13 I3 # p,.oos ~ 1 ~ 0 ; i I : Months ]oo, 113 J '~ >-4mm '3 3.5mm ~ 3mm ~ <3mm Fig. 1. Cumulative life-table primary patency rates for the four MED vein groups; The number at each point represents the number of grafts at risk for that interval, and the vertical line represents the standard error. Statistically significant difference between/>4.0 mm group and <3.0 mm group: p < (*), and between >~4.0 mm group and 3.0 mm group: p < (#). Table II. Life-table primary graft patency analysis for all MED groups. Interval Cumulative Standard Interval No. Failed patency patency error (mo) at risk grafts Duration rate (%) (%) MED ->4.0 mm O MED = 3.5 mm i MED = 3.0 mm MED <3.0 mm

4 528 Wengerter et al. Journal of VASCULAR SURGERY Cumulative Patency (%) 100~ oo, o 8 l 7" 20 * p~.o I ' I " I ' I ' I Months s, }-4mm,,0 3.0mm Short ~ 3.0mm Long Fig. 2. Cumulative life-table primary patency rates of long and short 3.0 mm veins and all veins t>4.0 mm. The number at each point represents the number of grafts at risk for that interval. Statistically significant difference between long 3.0 mm veins and i>4.0 mm group: p < (~). Table III. Life-table primary graft patency analysis for long and short 3.0 mm MED veins Interval Cumulative Standard Interval No. Failed patency patency error (too) at risk grafts Duration rate (%) (%) MED = 3.0 mm, short veins MED = 3.0 mm, long veins (short grafts, <45 cm) were compared to those 3.0 mm MED grafts originating from the femoral arteries (long grafts, >45 cm). Fig. 2 and Table III show that short vein grafts 3.0 mm MED demonstrated patency rates similar to the larger veins equal to or greater than 4.0 mm MED, whereas longer 3.0 mm veins from more proximal inflow sites had patency rates significantly lower than the larger diameter veins (p < 0.005). Outflow. Preoperative and intraoperative angiograms were reviewed to evaluate the effect of outflow on graft patency of small diameter grafts. Good outflow was defined as the presence of continuous flow from the graft into the foot, or the presence of an intact pedal arch for bypasses into the foot arteries. The percentage of grafts with poor outflow was similar in each of the four minimal external vein diameter groups, ranging from 22% to 27%. The 20 grafts with an MED of 3.0 mm or less and poor outflow were found to have a 2-year primary patency rate not significantly different from the 57 vein grafts of the same diameter with good outflow (52% vs 57%)

5 Volume 11 Number 4 April 1990 Vein graft diameter 529 Limb Salvage (%) 100~ 80 6O ' I ~.~ 61%~ 15 I~ 29 [~79% (~11 Jj71% 13 l l 0 I I I I Months I I [] >-4mm 3.Smm <> 3.0mm ~ <3.0mm Fig. 3. Cumulative life-table limb salvage rates for the four MED vein groups. The number at each point represents the number of limbs at risk for that int~erval, and the vertical line represents the standard error. Primary graft patency also did not vary with outflow adequacy in the larger (>3.0 mm) diameter grafts. Fibroti veins. Nineteen veins were found to contain varying lengths of thick-walled, fibrotic segments, but they were used because of impending limb loss and the lack of other, better sources of vein. These veins performed poorly, with a primary graft patency of 26% at 1 year, significantly lower in comparison to the group of all other (nonfibrotic) veins (p < 0.01). A disproportionally high number offibrotic veins were found in the smallest MED group (<3.0 mm), 22% compared with 5% to 6% in each of the other groups. However, exclusion of these fibrotic veins from the less than 3.0 mm MED group did not significantly improve patency for the entire group, and therefore the presence of fibrotic segments does not alone explain the poor performance of these small grafts. No failure of a vein graft less than 3.0 mm could be attributed to a technical flaw in the operation. Limb salvage. The overall limb salvage rate for the 289 revascularization procedures performed was 73% at 3 years. Among the four vein diameter groups, limb salvage increased as MED increased (Fig. 3, Table IV), although none of the differences were significant. Vein use. During the period of this study a total of 338 infrapopliteal revascularization procedures were performed at our institution, with greater saphenous vein used in 85%. In 49 (15%)of these cases the greater saphenous vein was not used because it was absent or too short for the intended procedure (29 cases), because it was judged to be of poor quality (9 cases), or because it was small (~<2.0 ram, 11 cases). Thus, in only 3% of cases was the greater saphenous not used because of smalt diameter alone. Alternative grafts used for these 49 cases included the lesser saphenous vein (4), arm veins (8), and PTFE grafts (37). Life-table primary patency at 3 years for PTFE infrapopliteal bypass grafts used as alternative conduits (n = 37) was 26%, and limb salvage was 58%. DISCUSSION The results Of this study indicate that when grouped by externally measured diameter, infrapopliteal reversed vein bypass graft patency and limb salvage increase as the vein diameter increases. This is similar to the findings of Buxton et al.14 who analyzed these variables for femoropopliteal reversed vein grafts. A positive correlation of diameter and limb salvage was also found. Only Taylor et al.6 have reported on the patency rates of infrapopliteal reversed vein grafts as they relate to vein size. They found veins less than 4.0 mm in diameter functioned as well as larger veins. However, they did not subdivide the veins less than 4.0 mm into separate groups. In our study we found that reversed veins 4.0 mm in MED and larger gave the best infrapopliteal bypass patency rates, whereas

6 530 Wengerter et al Journal of VASCULAR SURGERY Table IV. Life-table analysis of limb salvage rate for each of the MED groups Interval limb Interval No. salvage (mo) at risk Amputation Duration rate Cumulative limb Standard salvage (~) error (~) MED ->4.0 mm MED = 3.5 mm MED = 3.0 mm MED <3.0 mm grafts 3.5 mm in diameter gave similar results and can be used with impunity. Veins 3.0 mm in diameter when used as short (<45 cm) reversed vein grafts had patency results comparable to the larger grafts, and thus are acceptable infrapopliteal grafts. Long (>45 cm) 3.0 mm vein grafts and all reversed vein grafts less than 3.0 mm performed poorly, with overall patency results less than 20% at 3 years. These procedures are at high risk for failure, and alternative veins should be sought before using such grafts as infrapopliteal reversed vein bypass grafts. Proponents of the in situ technique have long professed.that smaller veins function better as in situ grafts than as reversed grafts. Corson et al. 8 found veins smaller than 3.5 mm provide patency comparable to larger veins. In view of our findings their data suggest that the in situ technique may be preferable if only a 3.0 mm vein is available, especially when a long bypass graft is required. However, before concluding that in situ grafts are better, this suggestion should be confirmed by a comparative study carried out in the same institution preferably in a randomized prospective fashion. Moreover, separate patency data on in situ veins equal to or smaller than 3.0 mm are needed before accepting claims of better patency for such grafts. Indeed, some anecdotal information suggests 2.5 mm in situ veins may be at high risk for failure because of increased trauma during valve lysis, is Studies examining patency rates of small in situ veins in a prospective randomized setting comparing the in situ with small reversed vein grafts are needed to resolve these questions. Vein use depends on the length and quality of vein available and its diameter as well as the required length of the bypass that must be performed. As a result, patient population and referral base will also influence vein use, for example, larger numbers 6~ secondary procedures can be expected to limit the amount of vein available. In such circumstances the use of ectopic reversed vein grafts and the short vein graft concept may be helpful to maximize vein use Awareness of the influence of vein diameter on reversed vein graft patency can help to select both the appropriate source of vein and the appropriate procedure for the vein available. To these ends duplex ultrasonography and contrast venography may be helpful. However, in some patients actual exploration may be needed to make a final determination of vein availability and vein acceptability. REFERENCES 1. Darling RC, Linton RR, Razzuk MA. Saphenous vein bypass grafts in femoropopliteal occlusive disease: a reappraisal. Surgery 1967;61:31-40.

7 Volume 11 Number 4 April 1990 Vein graft diameter Bernhard VM, Ashmore CS, Evans WE, Rodgers RE. Bypass grafting to distal arteries for limb salvage. Surg Gynecol Obstet 1972;135: LiCalzi LK, Stansel HC. The closure index: prediction of long-term patency of femoropopliteal vein grafts. Surgery 1982;91: LoGerfo FW, Corson JD, Mannick JA. Improved results with femoropopliteal vein grafts for limb salvage. Arch Surg 1977;112: Sonnenfeld T, Cronenstrand R. The advantages of the great saphenous vein as a femoropopliteal graft. A report of its clinical use. Scand J Thorac Cardiovasc Surg 1980;14: Taylor LM, Phinney ES, Porter I'M. Present status of reversed vein bypass for lower extremity revascularization. ] VASC SURG 1986;3: Leather RP, Shah DM, Karmody AM. Infrapopliteal bypass graft for limb salvage: increased patency and utilization of the saphenous vein used "in situ". Surgery 1981;90: Corson JD, Karmody AM, Shah DM, Naraynsingh V, Young HL, Leather RP. In situ vein bypasses to distal tibial and limited outflow tracts for limb salvage. Surgery 1984;96: 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 VAsc SuRe 1986;3: Veith FJ, Gupta SK. Femorodistal artery bypasses. In: Bergan JJ, Yao JST, eds. Operative techniques in vascular surgery. New York: Grune & Stratton, Inc, 1980: Veith FJ, Gupta SK, Samson RH, et al. Progress in limb salvage by reconstructive arterial surgery combined with new or improved adjunctive procedures. Ann Surg 1981;194: Rutherford RB, Flanigan DP, Gupta SK, et al. Suggested standards for reports dealing with lower extremity ischemia. J VASC SURG 1986;4: Peto R, Pike MC, Armitage P, et al. Design and analysis of randomized trials required prolonged observations of each patient. I. Introduction and design. BrJ Cancer 1976;34: Buxton B, Lambert RP, Pitt TTE. The significance of vein wall thickness and diameter in relation to the patency of femoropopliteal saphenous vein grafts. Surgery 1979;87: Bandyk DF, Kaebnick HW, Stewart GW, Towne JB. Durability 0fthe in situ saphenous vein arterial bypass: a comparison of primary and secondary patency. J VAsc SuRc 1987;5: Veith FJ, Gupta SK, Samson RH, Flores S, Janko G, Sher LA. Superficial femoral and popliteal arteries as inflow sites for distal bypasses. Surgery 1981;90: Veith FJ, Ascer E, Gupta SK, et al. Tibiotibial vein bypass grafts: a new operation for limb salvage. J VASC SURG 1985;2: Ascer E, Veith FJ, Gupta SK, et al. Short vein grafts: a superior option for arterial reconstructions to poor or compromised outflow tracts? J VAsc SUe, G 1988;7:370-8.