vEITH'S vIEWPOINT: Major Adverse Events Can Mislead

By: Frank J. Veith, M.D.

Major adverse event rates are an important criterion in the evaluation of new endovascular techniques or procedures and their safety and efficacy relative to other treatments. This is certainly true for carotid artery stenting (CAS), a procedure that some suggested early on was a valid alternative to carotid endarterectomy (CEA) as a method of stroke prevention.

Major adverse event rates (MAERs) associated with CAS are death, stroke, and myocardial infarction.

When first employed, CAS had higher MAERs than did CEA. However, with embolic protection devices, better patient selection, and improved balloons, stents, and introducer systems, these MAERs fell dramatically. These low MAERs prompted more claims that CAS was superior treatment for carotid stenoses and should replace CEA.

Partly because of such claims, there has been a stampede to place stents at the carotid bifurcation with specialists from many disciplines rushing to get trained and credentialed to perform CAS. In addition, enormous pressure was generated to obtain widespread reimbursement for the procedure. When Medicare reimbursement for CAS was restricted to trials and high-grade symptomatic disease, CAS registry trials proliferated. Most of these rush-to-treat efforts were the direct result of the presumption that CAS was a better treatment option based on the reports of low MAERs for the procedure.

It is therefore appropriate that physicians interested in vascular disease in general and carotid disease in particular step back and reexamine the real meaning and significance of MAERs. MAERs are calculated by dividing a numerator, the number of major adverse events associated with a procedure, by a denominator, the number of cases performed during the same period. The MAER can be lowered by decreasing the number of major adverse events or by increasing the number of cases performed without an event. The latter can be accomplished by performing the procedure on favorable cases.

With CAS this means choosing asymptomatic patients with favorable arch anatomy and relatively low-grade lesions. These are precisely the patients who might be better served with good medical management and no invasive intervention at all.

The latter statement is justified because all the so-called landmark trials comparing CEA and medical management of asymptomatic carotid stenoses were conducted in patients who did not systematically receive statins, antiplatelet agents, and ?-blockers, agents that may also prevent some strokes. These trials cannot be used to justify any invasive treatment in today's medical environment, and they certainly provide even less justification for performing carotid stenting in asymptomatic patients.

It is, therefore, inappropriate that low MAERs for CAS in largely (70%-90%) asymptomatic registry patients be used as a criterion for declaring the procedure safe, effective, and superior to other treatments. MAERs from patients who may not need the procedure are a misleading criterion for urging widespread adoption of CAS to treat carotid stenoses. Adequate prospective comparisons of CAS versus CEA in various groups of patients, and more importantly, adequate prospective comparisons of CAS and current medical management must be completed before the role of CAS is clearly defined and such recommendations can justifiably be made.

Moreover, the same limitations of MAERs must be considered when using this criterion to evaluate the comparative performance of surgeons and institutions as a basis for reimbursement. Those who unfairly lower their MAERs by performing procedures on easy patients and lesions that do not require treatment should not be rewarded for costly and unnecessary interventions which are of no real benefit to the patient