Study: Carotid endarterectomy may increase mortality risk

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The groundbreaking CREST trial resulted in an expansion of carotid artery stenting (CAS) to patients at standard risk for adverse events during surgery. While the results were mostly positive, there was a higher risk of stroke after CAS and a higher risk of MI after carotid endarterectomy (CEA). Researchers have now reported that both MI and biomarker+ were more common with CEA and although these levels were modest, these events were independently associated with increased mortality, according to a substudy of the CREST trial published June 21 in Circulation.

To better understand the characteristics and importance of MI among patients undergoing CAS or CEA, Joseph L. Blackshear, MD, of the Mayo Clinic in Jacksonville, Fla., and colleagues used data from the CREST trial to measure cardiac biomarkers before and six to eight hours after a procedure.

The CREST trial randomized 2,502 patients to receive either CEA (1,240 patients) or CAS (1,262 patients) and found a higher risk of stroke after CAS and a higher risk of MI after CEA. Forty-two patients had an adjudicated MI during the CREST trial—14 occurred among CAS patients and 28 among CEA patients. The median biomarker ratio was 40 times the upper limit of normal.

MI was defined as biomarker elevation plus chest pain or ECG evidence of ischemia during CREST. The authors also specified an additional biomarker category with neither chest pain nor ECG abnormality (biomarker+ only).

The researchers found that eight patients in the CAS group and 12 patients in the CEA group had biomarker+ only. Their median biomarker ratio was 14 times the upper limit of normal. Compared with patients without biomarker elevation, mortality was higher over four years for those with MI or biomarker+ only.

After the researchers adjusted for baseline risk factors, MI and biomarker+ only remained independently associated with increased mortality. MI or biomarker+ only patients were older and had a greater incidence of prior cardiovascular disease and lower creatinine clearance.

The only independent predictor of MI for CREST trial patients was a previous history of cardiovascular disease. The use preprocedural thienopyridines was 83 percent in MI patients, 71 percent in biomarker+ only patients and 77 percent in patients who had neither MI nor biomarker+. The researchers found that overall 177 deaths occurred and the estimated four-year mortality was 7.1 percent. MI and biomarker+ only events increased the risk of MI.

“In this large randomized trial of carotid revascularization comparing CAS and CEA, either protocol-defined MI or positive biomarkers without other criteria for MI occurred in 2.5 percent of patients,” the authors wrote. Protocol-defined MI and biomarker+ only were twice as frequent in patients who underwent CEA.

“CREST patients with periprocedural MI or biomarker+ only were three times more likely to die during follow-up than those without MI, even after adjustment for important baseline characteristics,” Blackshear and colleagues wrote.

The researchers said that the occurrence of periprocedural biomarker elevation or clinical MI is a marker of more extensive atherosclerotic disease. However, the authors said that “whether the development of an ischemic event in relation to the performance of a procedure adds further to this risk cannot be assessed in CREST and has not been discernable from any of other multiple studies reporting such an association.” They added that it will be important to recognize that this association is important to avoid the procedure in high-risk patients.

“These findings demonstrate that the occurrence of periprocedural MI or biomarker+ only identifies a population of patients at greater risk of death in longer-term follow-up and suggest that individualized patient risk for such events may be an important consideration in the choice of CAS or CEA and the choice of carotid revascularization or medical therapy,” the authors concluded.

The study was funded by the National Institute of Neurological Disorders and Stroke (NINDS) and the National Institutes of Health.