Risk Score Predicts Stroke or Death in Carotid Stenting Candidates

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A risk score incorporating 6 key factors including impending major surgery, previous stroke, and age accurately predicts in-hospital stroke or death after carotid artery stenting (CAS), according to a study published online September 19, 2012, ahead of print in the Journal of the American College of Cardiology. According to the authors, the new methodology may help improve patient selection for CAS.

Researchers led by Robert W. Yeh, MD, MSc, of the Massachusetts General Hospital (Boston, MA), looked at 11,122 CAS procedures performed from April 2005 through June 2011 as part of the Carotid Artery Revascularization and Endarterectomy (CARE) Registry, a component of the National Cardiovascular Data Registry (NCDR). In-hospital stroke or death occurred in 2.4% of the cohort, with strokes occurring in 242 patients (2.2%) and death in 52 (0.5%).

After multivariable analysis, 6 independent predictors of in-hospital stroke or death (5 that increased risk and 1 protective factor) were identified (table 1).

Table 1. Independent Predictors of In-hospital Stroke or Death

  Abbreviation: CEA, carotid endarterectomy.

The model incorporating these risk factors showed moderate discriminatory ability within the overall population (C-statistic of 0.71) and was well calibrated, meaning there was little difference between observed and predicted event rates across all levels of risk (P = 0.51). The model was validated in a separate population undergoing CAS from July 2011 through December 2011, yielding a similar C-statistic for in-hospital stroke/death (0.68) and P value for calibration (0.38). Model reliability within the asymptomatic and symptomatic subgroups was similar to that observed in the overall population.

Adding other angiographic risk factors such as lesion length failed to significantly improve the model’s accuracy. After assigning weighted points to each of the 6 individual risk factors, an overall risk score was applied to the CARE population, with similar ability to predict 30-day events (C-statistic 0.67). The risk score was also able to stratify patients into different levels of risk.

For instance, scores and their approximate corresponding in-hospital stroke or death rates were as follows:

• < 2 = 0.4%
• 2-3 = 0.5%
• 4-5 = 1%
• 6-7  = 1.9%
• 8-9 = 3.4%
• 10-11 = 5.6%
• > 11 = 8.9%

In addition, scores above 5 exceeded the 3% threshold for 30-day event rates, while scores above 9 exceeded the 6% 30-day threshold.

Deciding Between “Unique Risks” of 2 Procedures

Dr. Yeh and colleagues note that “[i]n an environment where 2 carotid revascularization strategies each pose unique risks influenced by patient characteristics, a schema for risk assessment is necessary to assist patients in selecting the most appropriate therapy.” The NCDR CAS risk score, they add, “may enable clinicians to identify those patients at excessive risk of CAS so that medical therapy or CEA may be offered as alternatives. Similarly, in patients with prohibitive risk with CEA, this risk score is helpful in identifying patients with acceptable CAS risk.”

While many of the risk factors identified in the analysis are not modifiable, the authors noted that there are conceivable ways to reduce CAS risk, such as using more aggressive anticoagulation bridging in A-fib patients. Two factors identified in the study that have not previously been associated with increased risk after CAS are A-fib and impending major surgery.

A-fib patients may be at higher periprocedural cardioembolic stroke risk due to the need to discontinue oral anticoagulation, and impending major surgery likely reflects “selection of a uniquely higher risk patient population,” the researchers note.

According to Michael R. Jaff, DO, also of Massachusetts General Hospital but not involved with the study, the NCDR CAS risk score does add useful prognostic information.

“This is the first risk score I know about that actually uses statistics in a large patient population to determine risk of carotid stenting, so for that reason alone it’s worth it,” he told TCTMD in a telephone interview. In particular, he called knowing what score correlates with a 30-day stroke or death rate below the 3% threshold “very helpful.”

Age Carries Considerable Weight

Dr. Jaff noted that, surprisingly, some of the anatomical factors clinicians usually look at in determining risk of carotid stenting, like a challenging thoracic aorta with a type III arch or dense calcification in the internal carotid artery, turned out not to be risk factors in the current algorithm. “That bothers me a little bit, but it’s hard to invalidate this when they’re looking at almost 12,000 cases,” he said.

He added that the most important aspect of the risk score may be the contribution of age. For instance, age 60 carries twice the risk of stroke or death compared to age 59 (score of 4 vs. score of 2), while the score assigned to age goes up to 6 once a patient hits 70.                                                                                                                      

“That’s an impressive ramp-up in risk just based on decile of age,” Dr. Jaff said. “Just being over 60 puts you at the upper limit of that 3% stroke range, so if you add one more factor, it’s probably not the right procedure to do, and that’s helpful to know.”

The risk score does provide guidance in clinical decision making, he added. “An older patient with a prior stroke and recently symptomatic lesions with A-fib, that might be somebody you wouldn’t consider doing a carotid stent in based on this,” he said. “I do think this provides some new light in the way we think about this.”

 

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Source:
Hawkins BM, Kennedy KF, Giri J, et al. Pre-procedural risk quantification for carotid stenting using the CAS Score. A report from the NCDR CARE Registry. J Am Coll Cardiol. 2012;Epub ahead of print.

 

Disclosures:

• The research was supported by the American College of Cardiology Foundation’s NCDR.
• Dr. Yeh reports serving as an investigator at the Harvard Clinical Research Institute and as a consultant for the Kaiser Permanente Division of Research.
• Dr. Jaff reports serving as an unpaid consultant to Abbott Vascular, Cordis, Covidien, and Medtronic Vascular.

 

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