Score helps docs assess CAS risk in high-risk patients

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It is possible to analyze a number of commonly collected variables and use them to quantify the possibility that patients who present a high risk of surgical complications will experience death or stroke within 30 days of endovascular carotid artery stenting (CAS), concludes a study published in the December issue of Stroke

Patients with significant carotid artery disease are at high risk of stroke and other adverse events, but the standard treatments, CAS and carotid endarterectomy (CEA), may not be appropriate for patients who are at high risk for surgery. “In clinical practice there is consensus that there are groups of patients at increased risk of complications with CEA due to unfavorable anatomical features, medical comorbidities or both,” author Neil J. Wimmer, MD, of Brigham and Women’s Hospital in Boston, and colleagues wrote. Guidelines published by 14 multispecialty societies, including the American College of Cardiology, the American Heart Association and the Society for Vascular Surgery, suggest weighing a patient’s likelihood of complications and expected benefit when deciding on a treatment approach.    

Wimmer et al set out to develop a scoring mechanism to ease this analysis in patients who were high-risk surgical patients. They followed patients from SAPPHIRE (Stenting and Angioplasty with Protection in Patients at High-Risk for Endarterectomy), the only randomized clinical trial to enroll high-risk patients for the purpose of comparing their outcomes after CAS and CEA (Catheter Cardiovasc Interv 2009;73:129-136).

Researchers in the current study selected 10,186 patients from the SAPPHIRE cohort who underwent CAS between Oct. 30, 2006, and Sept.  30, 2010. The mean age of the selected patients was 72.3 years and 38.9 percent were female. Age of more than 75 years was the most common surgical risk factor (39.8 percent), followed by previous CEA recurrent stenosis (23.1 percent), contralateral occlusion (13 percent), severe pulmonary disease (12.2 percent), and congestive heart failure or left ventricular ejection fraction of less than or equal to 30 percent (11 percent).

The primary outcome was a composite of death and stroke. At 30 days post-procedure, there were 123 deaths and 301 strokes in the study population, affecting 366 patients. The researchers identified 10 significant predictors of death or stroke within 30 days: age, prior stroke, prior transient ischemic attack (TIA), MI within four weeks, dialysis, need for concomitant cardiac surgery plus carotid revascularlization, left-sided lesion, lesion length, type II or type III aortic arch and two 90-degree bends. 

Wimmer et al assigned integers to the various risk factors. Patients received three points for a history of stroke; three for a history of TIA; five for MI within four weeks; five for dialysis; four for need for cardiac surgery and carotid revascularization; one for a type II or III aortic arch; two for a right sided lesion; and two for two 90-degree bends. Points ranged from zero to three depending on length of lesion in mm, and patients received two points for each decade of age after 50.

According to this scoring method, patients with a score of eight or less have less than a 3 percent risk of stroke or death after CAS; patients scoring between nine and 12 points have a 3 to 6 percent risk; patients scoring between 13 and 15 points have a 6 to 10 percent risk; and patients scoring 16 or more points have more than a 10 percent risk of experiencing death or stroke within 30 days of undergoing CAS.

The authors asserted that their risk scoring model is superior to previous models because in developing it they used data from only high-risk patients who “were not well-represented in the original surgical studies that led to the adverse event rate thresholds that are present in the multispecialty guidelines.” Noting that clinicians typically refer high-risk patients to CAS rather than CEA, “the risk prediction model presented here will now allow clinicians to assess CAS risk in a more quantitative manner than previously possible.”

The authors identified several limitations of their study. First, they acknowledge that there may be unobserved factors that are not identified in their model. Also, some patients were not evaluated by a neurologist to evaluate stroke, and so the stroke endpoint may be under-reported. Third, angiographic data was self-reported without laboratory data. Finally, the model predicts only risk of stroke or death after CAS, and does not compare that risk with the risk of other standard treatments for significant carotid artery disease.