The Trans-Atlantic Inter-Society Consensus Document on Management of Peripheral Arterial Disease (TASC I), published in January 2001, resulted from cooperation between fourteen medical, radiological and surgical societies in Europe and North America. To briefly summarize TASC I, peripheral arterial lesions were classified by length, complexity and other factors. Based on published or expected outcomes, recommendations for therapy were offered.
To oversimplify them for the sake of brevity, EVT (endovascular therapy) was preferred for TASC A and B lesions, while surgery was generally preferred for TASC C and D lesions. TASC II was published in 2007 in response to rapid advances in endovascular techniques and devices. In my estimation, this effort was fundamentally flawed. Rather than focusing on therapeutic outcomes in defined patient subgroups with specific anatomic features, the lesion-focused Working Group instead decided to move the target by changing the anatomic classification system to justify EVT for increasingly complex lesions.
In a classic case of reductio ad absurdam, TASC IIb was reportedly set to recommend EVT for all anatomic lesions (aorto-iliac, femoro-popliteal and tibial), regardless of clinical presentation, estimated patient longevity, activity level, co-morbidities, availability of autogenous conduit and extent of foot infection and gangrene.
Almost all the recommendations were Grade C (unsupported by evidence). Thankfully, TASC has been sent back to the drawing board.
It is no longer debatable that endovascular therapy has a major role in the treatment of lower extremity PAD, even in patients with critical limb ischemia. Ongoing advances (subintimal angioplasty, debulking devices, self-expanding stents in the SFA, covered stents, drug-eluting stents, soon to be available absorbable stents, etc.) permit endovascular treatment of nearly all patients’ lesions. But just because we can approach nearly all lesions by EVT first does not mean that we should. After all, we are tasked with treating patients, not lesions. TASC IIb would have proposed that we treat only lesions regardless of the associated clinical patient scenario. What is desperately needed, is a means of selecting the optimal approach in any individual patient.
To any clinician with substantial experience in long-term PAD patient management, it is obvious that an endovascular first approach for every patient is neither tenable nor appropriate; neither is open bypass first better for all. For example, recently published 3-month outcomes of EVT for 77 tibial lesions > 8 cm long are sobering: 31.2% patent without stenosis; 31.2 % patent but hemodynamically failed (> 50% restenosis); and 37.6% occluded. The 3-month patency of state of the art EVT for tibial disease is thus less than half the 5-year, primary-patency of popliteal-pedal bypass with autogenous vein. Do intermediate and long-term patency rates really matter? About half of foot wounds in patients with CLI (especially those with diabetes) are not healed within 3 months. If the revascularization has failed and the foot isn’t yet healed, w(h)ither the foot?
The only modern randomized trial comparing EVT with bypass, BASIL, despite its flaws, showed that the early advantages of EVT first in patients with severe limb ischemia disappear at 2 years; thereafter, limb preservation and survival advantages accrue for patients who had bypass first. These and other prospective study data such as those from the Prevent III Trial suggest that revascularization durability is an important consideration in many patients, and that revascularization failure is not inconsequential.
What clinicians and the patients we treat need are better means to assess the combined impact of patient co-morbidities, likelihood of long-term survival, lesion anatomy, runoff score, severity of foot ischemia and infection, and a host of other analyzable factors that influence outcome in managing the broad spectrum of patients with lower extremity atherosclerosis in order to select the most appropriate therapy for each individual patient. We need a new classification system, a refined comorbidity index, and better outcomes measurements.
To derive and validate such an algorithm, a well-constructed registry approach, perhaps as part of the SVS VQI, would be fruitful. Having recently participated as part of the International Working Group on The Diabetic Foot (IWGDF), I can attest that reliable data on which to base therapy are presently sparse. Among over 15,000 articles on PAD in patients with diabetic foot ulcers identified by Medline and Embase searches, only 48 provided sufficient data to be considered for evidence-based analysis. Data to allow comparison between EVT and open bypass in this subset of PAD patients was virtually non-existent.
Please note that I am not an endovascular nihilist. In our own practice, 70% of CLI patients get EVT first. However, after careful analysis and follow-up, it is clear that some of these patients might well have done better with a bypass first. In a recently published study proposing EVT first for CLI patients, the authors identified gangrene as a significant risk factor associated with a nearly 2.5-fold increased risk of limb loss. I would skeptically note that gangrene is the indication for revascularization in almost all of my diabetic patients.
The question is can we do better in some patients with open bypass first compared to endovascular therapy first? The answer is almost certainly yes. We need to sort out what works best in which situations. Until centers and specialists develop and adhere to a unified classification system and reporting standards, we will never learn the answer. Let’s get started; our patients deserve better.
Dr. Joseph L. Mills, Sr. is the newest associate medical editor for Vascular Specialist. He has been professor and chief of Vascular Surgery at the University of Arizona College of Medicine in Tucson since 1994. He is the Co-Director of the Southern Arizona Limb Salvage Alliance (SALSA). He has authored over 250 peer-reviewed journal articles and book chapters. Dr. Mills is co-editor of Rutherford’s Vascular Surgery (7th and 8th ed.) and “Comprehensive Vascular and Endovascular Surgery,” and editor “Management of Chronic Lower Limb Ischemia.” He is also the Vascular Surgery Section Editor for UpToDate. He has been the principal investigator for over 40 clinical trials. He is Past-President of the Peripheral Vascular Surgery Society and also served as Treasurer of the SVS, Chair of the SVS Distinguished Fellows Council, and Secretary-Treasurer of the Western Vascular Society. A Diplomate of the American Board of Surgery, Dr. Mills is a director of the ABS, and the current Chair of the Vascular Surgery Board (2010-2013). He is also Past-President of the Association of Program Directors in Vascular Surgery (APDVS) and current President of the Rocky Mountain Vascular Society and of the Western Vascular Society.