Atherothrombotic Risk Stratification and Ezetimibe for Secondary Prevention.

Background: Ezetimibe improves cardiovascular (CV) outcomes in patients stabilized after acute coronary syndrome (ACS) when added to statin therapy. After ACS, patients vary considerably in their risk for recurrent CV events.

Objectives: This study tested the hypothesis that atherothrombotic risk stratification may be useful to identify post-ACS patients who have the greatest potential for benefit from the addition of ezetimibe to statin therapy.

Methods: The TIMI (Thrombolysis In Myocardial Infarction) Risk Score for Secondary Prevention (TRS 2°P) is a simple 9-point risk stratification tool, previously developed in a large population with atherothrombosis to predict CV death, myocardial infarction (MI), and ischemic stroke (CV death/MI/ischemic cerebrovascular accident [iCVA]). The current study applied this tool prospectively to 17,717 post-ACS patients randomized either to ezetimibe and simvastatin or to placebo and simvastatin in IMPROVE-IT (Improved Reduction of Outcomes: Vytorin Efficacy International Trial). Treatment efficacy was assessed by baseline risk for CV death/MI/iCVA, the IMPROVE-IT composite endpoints (CE), and individual component endpoints at 7 years.

Results: All 9 clinical variables in the TRS 2°P were independent risk indicators for CV death/MI/iCVA (p < 0.001). The integer-based scheme showed a strong graded relationship with the rate of CV death/MI/iCVA, the trial CE, and the individual components (p trend <0.0001 for each). High-risk patients (n = 4,393; 25%), defined by ≥3 risk indicators, had a 6.3% (95% confidence interval: 2.9% to 9.7%) absolute risk reduction in CV death/MI/iCVA at 7 years with ezetimibe/simvastatin, thus translating to a number-needed-to-treat of 16. Intermediate-risk patients (2 risk indicators; n = 5,292; 30%) had a 2.2% (95% confidence interval: -0.3% to 4.6%) absolute risk reduction. Low-risk patients (0 to 1 risk indicators; n = 8,032; 45%) did not appear to derive benefit from the addition of ezetimibe (p interaction = 0.010). Similar findings were observed for the IMPROVE-IT primary CE.

Conclusions: Atherothrombotic risk stratification using the TRS 2°P identifies high-risk patients who derive greatest benefit from the addition of ezetimibe to statin therapy for secondary prevention after ACS. (Improved Reduction of Outcomes: Vytorin Efficacy International Trial [IMPROVE-IT]; NCT00202878).