Tool Identifies Risk in Stenting ACS Patients

By Todd Neale, Senior Staff Writer, MedPage Today

Published: November 19, 2012

Reviewed by Dori F. Zaleznik, MD; Associate Clinical Professor of Medicine, Harvard Medical School, Boston and Dorothy Caputo, MA, BSN, RN, Nurse Planner

A new, easy-to-calculate risk score developed for patients with non-ST-segment elevation acute coronary syndromes (ACS) undergoing percutaneous coronary intervention (PCI) had better prognostic accuracy than other widely used risk scores, researchers found.

The ACUITY-PCI risk score includes six variables — insulin-treated diabetes, renal insufficiency, baseline cardiac biomarker elevation or ST-segment deviation, presence of a bifurcation lesion, small vessel/diffuse coronary artery disease, and extent of coronary artery disease, according to Gregg Stone, MD, of Columbia University Medical Center in New York City, and colleagues.

The 1-year rate of death or MI significantly increased from 5.3% in the lowest risk tertile to 9.1% in the middle tertile to 19% in the highest tertile (P<0.001), the researchers reported in the November issue of JACC: Cardiovascular Interventions.

Discrimination and calibration were greater with the ACUITY-PCI score than with other established scores.

“Although the TIMI and the GRACE scores have been shown to be valuable prognostic tools at the time of hospital admission for selecting pharmacological strategies and identifying those patients most likely to benefit from an invasive strategy, they have not been optimized for patients undergoing PCI and, thus, have relatively poor prognostic power to further risk stratify acute coronary syndrome patients undergoing PCI,” Stone and colleagues wrote.

“The ACUITY-PCI score is therefore intended to supplement the TIMI and GRACE scores when an invasive strategy has been undertaken and PCI is being considered.”

The researchers created the risk score using data from 1,692 patients enrolled in the angiographic substudy of the ACUITY trial, which was a comparison of heparin plus a glycoprotein IIb/IIIa inhibitor, bivalirudin (Angiomax) plus a glycoprotein IIb/IIIa inhibitor, or bivalirudin alone in patients with ACS undergoing an early invasive strategy. They then validated the score using another 846 patients from the same study.

Multivariate analysis revealed six variables that were significantly associated with 1-year mortality and MI and were included in the score. The researchers assigned points based on the strength of the predictor:

• Insulin-treated diabetes (12 points)
• Renal insufficiency (12 points)
• Baseline cardiac biomarker elevation or ST-segment deviation (8 points)
• Bifurcation lesion (4 points)
• Small vessel/diffuse coronary artery disease (2 points)
• Extent of coronary artery disease (1 point for each 10 mm of disease)

The C-statistic for the risk score — a measure of discrimination — was 0.67 in the derivation cohort and 0.70 in the validation cohort. In the validation cohort, the chi-square statistic for calibration was 6.2 and the index of separation was 0.44.

All of those values were better than those seen for four other established risk scores — TIMI, GRACE, SYNTAX, and Clinical SYNTAX. In addition, the net reclassification improvement with the new score ranged from 9% to 38% and the integrated discrimination index varied from 1.9% to 2.7%.

The researchers noted that the ACUITY-PCI score also was a good predictor of 1-year definite or probable stent thrombosis, with a C-statistic of 0.72.

In another study in the same journal, George Dangas, MD, PhD, of Mount Sinai Medical Center in New York City, and colleagues — including Stone — reported on the development of a risk score specifically for stent thrombosis in patients with ACS undergoing PCI.

The study included 6,139 patients from the HORIZONS-AMI and ACUITY trials, which included those with ST-segment elevation MI (STEMI) in the former trial and those with non-STEMI and unstable angina in the latter. The researchers used 4,093 patients for the derivation cohort and 2,046 for the validation cohort.

The risk score included 10 variables that were significantly associated with the risk of Academic Research Consortium-defined definite or probable stent thrombosis at 1 year:

• Type of acute coronary syndrome (4 points for STEMI, 2 points for non-ST-segment elevation ACS with ST deviation, and 1 point for non-ST-segment elevation ACS without ST changes)
• Current smoking (1 point)
• Insulin-dependent diabetes (2 points)
• Prior PCI (1 point)
• Baseline platelet count (1 point for 250 to 400 K/µL and 2 points for more than 400 K/µL)
• Absence of pre-PCI heparin therapy (1 point)
• Aneurysmal/ulcerated lesion (2 points)
• Baseline TIMI flow grade 0/1 (1 point)
• Final TIMI flow grade less than 3 (1 point)
• Number of treated vessels (1 point for two vessels and 2 points for three vessels)

Scores from 1 to 6 are considered low risk, 7 to 9 are intermediate risk, and 10 or higher are high risk.

The rates of stent thrombosis at 1 year were 1.36%, 3.06%, and 9.18% across the three risk tertiles in the derivation cohort (P<0.001 for trend), with a similar trend seen in the validation cohort.

The C-statistics were 0.67 in the derivation cohort and 0.66 in the validation cohort. Performance was comparable for events occurring both early (within the first 30 days) and late (from 1 month to 1 year).

“We believe that the development and initial validation of this stent thrombosis risk score can be a useful tool for both clinical practice and future clinical investigation (future analyses of trials or registries), as it can be a simple way to risk stratify patients immediately following a procedure,” Dangas and colleagues wrote. “The risk score could also be used in the informed consent process to better inform patients of their individual risk of stent thrombosis.”

But Ron Waksman, MD, and Israel Barbash, MD, of MedStar Washington Hospital Center in Washington, D.C., noted some limitations of the tool, including the pooling of different types of patients, the exclusion of important variables associated with stent thrombosis risk, and the use of mostly first-generation drug-eluting stents in the trials.

“It is imperative that the user of such a prediction tool be aware of its capabilities and performance, as well as its limitations, in various clinical scenarios,” they wrote in an accompanying editorial.

“A newly developed risk score for stent thrombosis should be robust and should be tested across broad study populations, stents, and antiplatelet regimens. A new model should also be validated in a setting different from the one in which it was derived,” they wrote. “Unfortunately, this is not the case with the newly proposed model.”

“Until such an encompassing tool is developed and validated,” they wrote, “one should rely on the known stent thrombosis risk factors and tailor an appropriate treatment for each patient.”

From the American Heart Association:

• 2011 ACCF/AHA/SCAI Guidelines for Percutaneous Coronary Intervention

Todd Neale

Senior Staff Writer

Todd Neale, MedPage Today Staff Writer, got his start in journalism at Audubon Magazine and made a stop in directory publishing before landing at MedPage Today. He received a B.S. in biology from the University of Massachusetts Amherst and an M.A. in journalism from the Science, Health, and Environmental Reporting program at New York University. He is based atMedPage Today headquarters in Little Falls, N.J.

SOURCE:

http://www.medpagetoday.com/Cardiology/AcuteCoronarySyndrome/36010