From the Masters: A sea-change for TransAtlantic Inter-Society Consensus (TASC)

Full fathom five thy father lies;

Of his bones are coral made;

Those are pearls that were his eyes:

Nothing of him that doth fade,

But doth suffer a sea-change

Into something rich and strange.

Sea-nymphs hourly ring his knell . . .

— William Shakespeare, The Tempest, I. ii.

In 1996, a novel consensus process was initiated entitled: ‘the Management of Peripheral Arterial Disease – TransAtlantic Inter-Society Consensus’, which is well known in the vascular community as TASC. ¹ As noted in the Introduction to the Consensus, a key rationale was to address the observation that a ‘surprising variation continues to be found in the management of individual patients with identical conditions’, with the goal to ‘help promote a uniform high-level of medical care across different countries’. The members of the writing group were from the major vascular societies at the time, representing vascular surgery, cardiology, vascular medicine/angiology, interventional radiology, vascular pathology and health economics and outcomes. The committee was chaired by two well-known and quite visionary vascular surgeons: John Dormandy from London and Robert Rutherford from Colorado. Bob was my mentor in medical school, where he enlisted me to do research in our vascular laboratory, and from that experience and Bob’s expansive personality, I knew I wanted to be a vascular physician. Then early in my career at the University of Colorado, I was very fortunate to represent the Society for Vascular Medicine (SVM) as a member of the TASC writing group. From that engagement, I embarked on a marvelous journey that opened my perspective to a broad international group of recognized leaders in their vascular disciplines. This group worked well together to run a disciplined writing committee that included input from the key vascular societies to develop a final document; the results published in the year 2000 generated 107 recommendations and 47 critical issues. ¹ Remarkably, all of these recommendations were agreed upon except for one footnote describing a TASC type B femoropopliteal lesion, where the Cardiovascular and Interventional Radiological Society of Europe had a slightly different definition.

In addition to providing a comprehensive overview of all aspects of the diagnosis and management of peripheral artery disease (PAD), this first consensus established a morphologic lesion stratification for iliac, femoropopliteal, and infrapopliteal lesions that was intended to provide a classification system and to recommend appropriate treatment strategies with the main options of endovascular versus open surgical repair. At that time, these recommendations were based mostly on a consensus, not evidence, and followed the concept that a simple proximal stenosis could be approached with an endovascular procedure and more complex and distal disease would usually require a surgical bypass.

Published in the year 2000, this guideline established many precedents. The writing committee was international (primarily Western Europe and North America) and represented the primary vascular disciplines, with a goal to harmonize efforts in order to provide the best care for the vascular patient. Subsequently, a number of key guidelines soon followed, including those from the American College of Cardiology/American Heart Association and additional guidelines from the various vascular subspecialties. ² Personally, working on TASC on behalf of the SVM was quite invigorating in that it opened up opportunities to establish new international relationships, to think rigorously, and to challenge my writing group peers to achieve a comprehensive and inclusive document. In addition, I valued the broader vision of bringing disparate societies together to improve patient care.

After publishing TASC, John Dormandy wanted to step down, and Lars Norgren who represented the European Society for Vascular Surgery (ESVS) was asked to take over as European editor for the TASC II, which was initiated in 2004 and published in 2007. ³ Lars asked me to become the American editor, to make the link between vascular surgery and vascular medicine even more evident. This second Consensus had a broader goal to not only reach the vascular specialist but also physicians in primary care who took care of patients with PAD. In addition, we broadened the geographic representation of the writing committee to not only include Europe and North America, but also Asia, Africa, and Australia. A similar writing group process to that developed for TASC with the addition of a rigorous grading system to evaluate levels of evidence and subsequent recommendations was established. Remarkably, a broad range of societies representing not only the vascular specialties but also the expanded geographic areas remained intact and cohesive in the development of the document while providing new evidence for recommendations.

In 2013, plans for a complete update (TASC III) were initiated and the additional societies and writing group members were enthusiastic to participate. However, critical questions were raised regarding the emerging strategy of an ‘endovascular-first’ approach, which relegated open bypass surgery for later stages of the disease. The problem with this thinking, as raised by vascular surgeons, was that it was not based on level 1 evidence and was felt to promote a lesion-focused approach to revascularization procedures. The BASIL trial of endovascular versus bypass surgery had been published in 2005 and indicated that in patients with severe leg ischemia, the two approaches were roughly equivalent on short-term outcomes, which did not support one approach over the other. ⁴ The Society for Vascular Surgery (SVS) and the ESVS pulled out of the process with the stated intent to develop a new global vascular practice guideline specific to their specialty. They also communicated that ‘Setting standards across the world for optimal care of this group of patients resides principally with vascular surgeons’. ⁵ The plans for a complete multidisciplinary TASC update were therefore abandoned. A supplement to TASC II, published in 2015, included an updated and comprehensive lesion classification that continued to promote an endovascular-first approach. ⁶ In 2019, the SVS and ESVS published their Global Vascular Guidelines on the management of chronic limb-threatening ischemia. ⁷ This is a scholarly document that provides a broad assessment of patients with ‘Chronic limb-threatening ischemia’ (CLTI), which is intended to replace the term ‘critical limb ischemia’ (CLI).

As for TASC, the editors felt there was a need for PAD guidelines that were appropriate for low- and middle-income countries that have a large burden of PAD but often lack resources to provide comprehensive care. In a TASC publication, prioritization of patient management goals were considered, but we were unable to continue that effort due to a lack of resources. ⁸ It is notable that TASC remains continuously cited: at the end of 2019, more than 8000 citations were recorded. In particular, the TASC lesion classification is still extensively used today.

It is interesting for me to reflect on this vascular journey. Twenty years ago, the key international vascular societies put aside their particular societal differences and did something amazing in creating a TASC consensus. However, at least in terms of developing comprehensive inter-societal guidelines, that consensus was not sustainable. We are now shifting back to a societal focus that while worthy, may not reflect the totality of vascular care or the importance of interdisciplinary collaboration in the management of the patient with vascular disease. These are complex patients who not only have arterial disease in their peripheral circulation leading to claudication symptoms, loss of function, and, in the most severe cases, the threat of limb loss, but also have a systemic disorder that substantially increases their risk of both cardiac and limb ischemic events that require aggressive medical management.

For vascular physicians, what does the future hold? Have we regressed back to what appears to be tribal behavior, or does the opportunity exist for ‘a sea-change into something rich and strange’? The quote by Shakespeare begins with the description of the death of a father now residing at the bottom of the sea. Nothing could be more grim, except that he is undergoing a metamorphosis, which is both beautiful and awesome – captured by the words ‘sea-change’. When you’re staring at the ocean from a remote place on the planet, and the waters undergo a sudden transformation, you have experienced a sea-change, which is a transformation into something both ‘rich and strange’.

As we enter 2020, I feel the vascular societies and specialties are going to find new reasons to work together – this time based on science and new evidence from clinical trials. For example, the BEST-CLI trial will attempt to establish the optimal treatment strategy (endovascular first versus surgical first) in the setting of critical limb ischemia (now CLTI) with a primary endpoint of major adverse limb event-free survival (MALE). ⁹ Rather than focusing just on technical or procedural success, this landmark trial will evaluate clinical endpoints referable to the leg and mortality in the composition endpoint. In addition, the VOYAGER PAD trial is nearing completion and will evaluate an antithrombotic treatment strategy initiated at the time of lower extremity revascularization. ¹⁰ This is the first cardiovascular outcome trial to study a dedicated PAD population with a novel primary composite endpoint including cardiovascular death, myocardial infarction, ischemic stroke (major adverse cardiovascular events – MACE), acute limb ischemia, and major amputation of a vascular cause (MALE). The treatment strategy involves all patients receiving background aspirin therapy with randomization to low-dose rivaroxaban versus placebo, which was successful at preventing MACE and MALE events in a subset of patients with stable PAD in the COMPASS trial. ¹¹

A new reality is now emerging with the promise of new evidence from clinical trials to address key treatment decisions for the patient with PAD. In the setting of revascularization, we know that any intervention in the leg targeting symptom relief or limb preservation is associated with a marked increased risk of acute limb ischemia, as well as a modest increased risk of MACE events for years after the procedure.^12,13 In stable symptomatic PAD, there are a number of lines of evidence that new and potent antithrombotic strategies prevent both MACE and MALE events. ¹⁴ Even more remarkable is that profound lowering of low-density lipoprotein (LDL) cholesterol levels in these patients is also associated with a reduction in MACE and MALE events. ¹⁵ Thus, we are entering a new phase of awareness and integration that will no longer allow for narrowly focused subspecialty care, which ignores the broader reality that appropriate, targeted, and intensive medical therapies are essential in the management of patients with PAD, regardless of whether they are treated with a revascularization or not.

The management of vascular disease is, by definition, multidisciplinary, and treatments should be seen as complementary, not competitive. For example, the debate on which revascularization strategy is ‘best’ has extended to exercise rehabilitation, where supervised exercise training and revascularization provide comparable improvements on exercise performance and patient-reported outcomes, but the real message is that the combination is better than either treatment alone. ¹⁶ An evidence-based antithrombotic strategy after lower extremity revascularization will not only improve the outcomes of the procedure but hopefully reduce the future risk of MACE and MALE. Although this is an exciting time for vascular physicians, the benefits of a comprehensive and multidisciplinary approach will only be realized if integrated vascular programs are developed that once again bring us back together. I very much look forward to seeing that happen – which will be consistent with the vision that Dr Rutherford articulated for me back in the 1970s.