Introduction
A disruptive technology can be defined as one that displaces a standard old method for performing certain functions because the new one is so clearly better. Examples of disruptive technologies would be the electric light displacing candle light, steam power displacing sail power for ships, jet engines displacing piston engines for long distance aircraft, and computer word processing displacing the typewriter. Disruptive technologies change the way things are done, put companies out of business, and lead to increased productivity and progress.
Vascular surgery has several examples of disruptive technology, including the interposition of vascular graft displacing ligation for aneurysm repair, prosthetic or venous grafts displacing sympathectomy for ischemic arterial occlusive disease, iliac stenting displacing bypass grafting for aortoiliac occlusive disease, and endovascular aortic graft repair of aneurysms displacing open aneurysm repairs in the abdomen and chest.
Although it may take some time for the displacements to occur, the clear advantages of the newer disruptive technologies so obviously outweigh those of the older alternative methods that there can be no question that the latter will largely slip into oblivion or that they will play only a very minor role alongside the new disruptive technology.
Is Carotid Stenting A Disruptive Technology?
In light of these considerations, one can fairly ask the question: Is carotid angioplasty and stenting (CAS) a similar disruptive technology? Carotid balloon angioplasty was first performed in 1980, and a stent was first used in 1989 to treat an intimal flap after angioplasty. Since then, there has been increasing interest in CAS, as interventional specialists who had little previous interest in treating carotid bifurcation arteriosclerosis rushed to apply their endovascular skills and tools in this new area of opportunity.
The technique for performing CAS was perfected largely by interventional cardiologists and a few interventional radiologists. Industry contributed technical improvements with lower profile systems, better stents, and a variety of embolic protection devices. Presentations, articles, registries, and courses proliferated dramatically.
It certainly appeared that CAS was a disruptive technology that would replace the previous gold standard — carotid endarterectomy (CEA). The emergence of this new disruptive technology was potentiated by low adverse event rates that were observed when CAS was performed extensively in registries made up largely of asymptomatic patients (up to 90% in some registries). Based on these registry results, in the early 2000s, some CAS enthusiasts, particularly in the interventional cardiology community, were claiming vociferously that carotid surgery was obsolete and that CAS was already equal to or better than the old gold standard, CEA.
All sorts of specialists rushed to get on the band wagon and learn how to perform the new disruptive technology before it was too late. These specialists included not only the colleagues of the many interventional cardiologists and the few interventional radiologists that had promoted CAS from the beginning, but also interventional neurologists. All saw the opportunity to earn procedural dollars. Even vascular and neurologic surgeons crowded courses in an effort to get on the rapidly moving train. CAS appeared truly to be a disruptive better technology that would blow away an old inferior one.
Recent Developments
However, around 2006 some disturbing cracks began to appear in the facade of the new disruptive technology. Unacceptably high adverse event rates were observed when CAS was performed in octogenarians, particularly those who were symptomatic.[1,2] High adverse event rates for CAS performed in symptomatic patients were later reported in several randomized prospective trials. In one of these, the French EVA 3S trial, CAS had a significantly higher stroke and death rate than CEA.[3] Although some CAS enthusiasts criticized this study, none of their criticisms appeared to be crucial. Moreover, meta-analyses of trials suggest that CEA is safer than CAS, particularly in symptomatic patients,[4-6] and 2 population based studies in the United States show that CAS has significantly higher stroke and death rates than CEA.[7,8]
Since the appearance of these data, many of the original CAS enthusiasts have expressed a note of caution and the need for those performing CAS to select patients more carefully, avoiding those with imperfect anatomy or ugly, very high-grade, or calcified lesions.
In light of these developments, it is fair to pose the question: Is CAS really a disruptive technology? If one defines a disruptive technology as one that will largely replace the existing treatment, the answer has to be no. If one defines a disruptive technology as one that shakes up and changes the existing treatment landscape, the answer has to be yes. Some patients will clearly be better treated with CAS; others will be better treated by CEA. And still others, perhaps the vast majority of asymptomatic patients with carotid bifurcation lesions, will be best treated with improved medical treatment, which includes optimal doses of statins, beta blockers, antiplatelet agents, and better diabetic and blood pressure control.
It will be at least several years until the exact proportions of patients who are best treated by these 3 modalities are known, CAS is already disruptive because it forces us to look at these questions and will certainly have some role to play. CAS will probably not be wholly disruptive, however, because it will never replace the current standard treatment (CEA) completely or even almost completely. Accordingly, CAS will never be as disruptive a technology as endovascular aneurysm repair to open abdominal aortic aneurysm repair or thoracic endovascular aneurysm repair to open thoracic aneurysm repair.
Conclusion
Thus CAS will never be as disruptive as its enthusiasts might have hoped it to be. It will, however, have a positive impact on the treatment of carotid artery disease, although the nature and extent of that impact remain to be determined.
Reviewed by Dr. Ramaz Mitaishvili
