Update on Carotid Stenting: What Went Wrong?

“… the procedure is expected to greatly reduce the demand for a common operation in which surgeons slice open the neck and scrape the carotids clean from earlobe to collarbone”.

“The shift to angioplasty has drawn fervent opposition from surgeons who question angioplasty’s long-term effectiveness and safety…They also stand to lose a major source of income…”¹

The quotes above are from a USA Today article announcing the Federal Drug Administration’s approval of carotid stenting (CAS) in 2004. Much has happened since then! However, what did not happen was even more significant: the anticipated explosive growth of the new technique to become the dominant form of carotid revascularization… and the “rapid demise” of carotid endarterectomy (CEA). CEA remains the standard of care for most patients with severe CAS, both symptomatic and asymptomatic, and will remain so in the foreseeable future. So, it is appropriate to ask (and wonder): what went wrong…?

The truth be told, CAS faced a steep uphill battle from the outset. It was designed to go “against” (and compete with) the very best operation in vascular surgery. Unlike aortic repair, myocardial revascularization, and many others, the carotid territory is totally unique, in that standard open surgery (CEA) represents an excellent treatment option that produces optimal results for the majority of patients. While undoubtedly appealing, a less invasive percutaneous approach (CAS) would offer little, if any, potential gain in terms of morbidity or mortality, avoidance of surgical-scar disfigurement, hospital length of stay, recovery time, etc. In other words, there was (and is) a high level of satisfaction with the current standard of care. What’s a new technique to do in the face of such odds? Making a bad situation worse was the “approach” used by the early CAS proponents and enthusiasts. They recognized that NASCET was the foundation for modern-day CEA surgery and went on to focus (like a laser beam!) on the real and alleged shortcomings of that trial: the “many” exclusions, poor outcomes in certain patient subsets, the elderly, etc. And, almost misleadingly, the early experience with CAS was quite encouraging: it seemed relatively easy to perform (in the hands of expert interventionists), and proved to be reasonably safe. Appropriately, there was an early focus on the risk of cerebral embolization and the recognition that stroke prevention would be an absolute prerequisite for CAS to become a viable treatment option. So, embolic protection devices were developed and became well established rather quickly (but without solid proof of efficacy). The rest is history: CAS champions became convinced “CEA was dead in the water”. In the process, though, they appeared not to recognize a number of significant flaws in their thinking:

• the NASCET results and perceived shortcomings had been largely misconstrued, and increasingly irrelevant at the present time;²

• the assumption that NASCET-excluded patients would (somehow) benefit from CAS — no basis for that whatsoever;

• they thought of CAS as a competitive technique (to CEA), “destined” to overtake surgery and become (rapidly) the dominant carotid revascularization approach in the near future;

• many, many studies were designed and performed…but the question that really matters has not yet been answered or even addressed: which patients benefit the most from which technique?

To be fair, cardiologists were not alone in embracing CAS with gusto and unbridled enthusiasm as other interventional specialists became (early on) strong proponents as well — yours truly included. Interventional surgeons, however, remained open-minded about the relative merits and limitations of CAS. After all, we can still perform CEA, and do so increasingly as a result of the recognition that considerable evidence has accumulated on the existence of a group of patients that are at higher risk (for complications) when subjected to stenting: recent hemispheric symptoms, the elderly, unfavorable arch and carotid anatomies, extensive very tight stenoses, dense calcification, etc. At the same time a consensus of sorts has evolved on the clinical situations, where CAS is most likely to be safe and successful: asymptomatic disease, subcritical stenoses, stable plaques, absence of significant calcification, and the like. The problem is that — increasingly — experts are beginning to questions whether such patients need any intervention at all…especially many of those with asymptomatic disease who are likely to do quite well on optimal medical therapy alone. In closing, I would offer the following take-home messages:

• CAS is an important and exciting new treatment modality, but its role (overall) remains poorly defined;

• Most specialists agree today that the best indication for stenting (instead of CEA) relates to anatomic high risk;

• Available evidence from the completed international randomized trials that compared CEA and CAS is of moderate quality only, and points (roughly) to equivalence of both techniques in terms of mortality and risk of myocardial infarction, but CAS may be a little more dangerous to the brain.³

But CAS is not going away. In fact, I believe new technologies and other developments in the areas of embolic protection and access will one day propel CAS to a level of full competitiveness with CEA. In the meantime, we will await with some anxiety the results of the randomized CREST trial (by the end of 2009) that will likely provide the best evidence to date on the merits of one versus the other for the treatment of symptomatic and asymptomatic patients with severe CAS.