The Current Pattern of Surgical Bypass in the Context of a Limb Preservation Practice

Multidisciplinary programs have been shown to improve outcomes for patients facing nonhealing wounds and possible limb loss.^12,13 This review assesses the pattern of surgical bypass performed in the context of such a multidisciplinary limb program. The goal of this analysis was to assess the impact of a such a program on the frequency of surgical bypass and type of bypass constructed in this complex patient population. The question arises as to whether an endovascular-first approach is increasingly used in a limb program or whether bypasses are performed in a limb program that are different than those performed in standard surgical practices. We have published basic criteria to guide the use of bypass in our limb practice,¹⁴ and these criteria were used as guidelines but not as dogmatic rules in the choice of revascularization type. Additionally, the BEST-CLI and BASIL-2 trials have addressed the issue of bypass vs endovascular therapy, but the timing of the publication of these trials had minimal impact on the time interval involved in this analysis. Although we believe that these trials will have an added impact on the decision-making process, a discussion of BEST-CLI and BASIL-2 is beyond the scope of this manuscript.

Our data noted a reversal in the trend of decreasing bypass frequency after formal initiation of the limb program. Interestingly, there was a corresponding increase in endovascular procedures during the same time interval, indicating an increase in total lower extremity revascularization in the context of the limb program. This increase in the number of surgical bypasses may be related 

to an increased complexity of the revascularization required due to the tertiary (often quaternary) referral patterns involved with such a limb preservation program, as well as many patients having had failed attempts at revascularization prior to referral. 

The type of bypass performed was also different in the limb program cohort compared with prior experience in a standard vascular practice. The saphenous vein has long been the gold standard autogenous conduit to treat CLTI.¹⁵ Tibial bypass surpassed popliteal bypass, and the use of prosthetic grafts with anastomotic adjuncts was increased based on a frequent lack of saphenous vein conduit due to prior lower extremity bypass, coronary bypass, varicose veins, or phlebitic veins. When an autogenous conduit is not available, it has been our practice to use HePTFE with appropriate anastomotic adjuncts as described. If a distal tibial artery is available as an outflow target for bypass, the DVP technique is used. This configuration alters the compliance mismatch between the diseased artery and the prosthetic graft, and offsets the hyperplastic response to the suture line between the graft and vein patch, thereby minimizing hyperplasia in the runoff tibial artery.¹⁶ Additionally, surgeons find the patch technically easier to suture to the diseased artery, often a calcified tibial artery, as compared with the larger, stiff prosthetic material. If the distal tibial target artery is suboptimal in terms of caliber or lack of inline runoff, an arteriovenous fistula is added to the DVP technique. This reduces outflow resistance and maintains graft velocity above the critical thrombotic threshold.^17,18 Recently, DVA has been added to the bypass armamentarium through the DVP technique (DVP-DVA). This technique is an option for patients with a “desert foot” lacking an outflow target as well as an available venous conduit.⁴ Our experience with deep venous revascularization by DVP bypass is ongoing and a subject for future analysis.

The presence of a multidisciplinary program may alleviate some reluctance for such referrals from other vascular providers, as the patient is referred for treatment of both soft tissue wounds as well as persistent ischemia. Such referrals to the limb preservation program often involve cases with failed prior attempts at revascularization. This increases the complexity of subsequent revascularization, especially in the form of a surgical bypass. In our experience, 41% of the bypass procedures were performed after a prior failed revascularization: endovascular (33) and prior bypass (9). Failed endovascular therapy can lead to an alteration of the target artery, or a more distal location on the target than would have been required with an initial bypass prior to endovascular failure.^19,20 The BASIL-1 trial demonstrated that bypass was less successful after failed balloon angioplasty.²¹ Prior failed bypass also increases subsequent bypass complexity through prior utilization of an autogenous conduit and available target arteries. Finally, up to 20% of patients in a limb-threatening situation present with a paucity of any suitable distal arterial targets, or the so-called “desert foot”.²² The cohort of patients treated in a limb preservation program can involve the difficult scenario that compounds several complex factors: lack of an autogenous conduit, prior failed revascularization, and a disadvantaged target artery. Therefore, alternative conduits and anastomotic adjuncts have been utilized to overcome these challenges in an attempt to prevent amputation. The need for surgical bypass as a significant revascularization option in the context of the limb preservation program is important and seems to stimulate an upward trend in terms of bypass frequency.  

There are certainly limitations to this data. The analysis was performed at a single institution with bypasses performed by a single surgeon; this inherently leads to practice bias. The number of bypasses performed after a failed endovascular therapy may demonstrate bias in patient selection, as patients with more complex pathologies and surgical history are more likely be referred to a limb preservation center compared to a standard surgical practice. As such, this data should be seen as an observation, stimulating further characterization or future trends in lower extremity revascularization after establishment of an endovascular-first/only approach in many centers treating CLTI for amputation prevention. Additionally, this study did not analyze outcomes of the techniques or effect of patient comorbidities. However, surgical bypass, often with a prosthetic conduit and anastomotic adjuncts, was observed to fill a significant role in revascularization in the context of a limb preservation program. It will be important to master these techniques so that revascularization can continue to be offered to patients for healing and amputation prevention. Establishment of a limb preservation program requires technical competence in all forms of revascularization; therefore, communication between interventionalists and surgeons to choose the appropriate strategy of revascularization in such a program is critical for success.