A risk score system for predicting adverse outcomes and magnitude of benefit with glycoprotein IIb/IIIa inhibitor therapy in patients with unstable angina pectoris

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Abstract

Clinical outcomes of patients with unstable angina are variable. We sought to identify predictors of adverse clinical outcomes in patients with unstable angina and to investigate whether these factors would predict the magnitude of benefit achieved with platelet glycoprotein IIb/IIIa inhibition. We analyzed 20 variables in the 1,915 patients enrolled in the Platelet Receptor Inhibition for Ischemic Syndrome Management in Patients Limited by Unstable Signs and Symptoms trial. Five independent predictors were identified: age >65 years, prior coronary artery bypass grafting, antecedent aspirin use, antecedent β-blocker use, and ST depressions on the presenting electrocardiogram. A risk score system was created using these predictors in which patients were assigned 1 point for the presence of each risk factor. There was a progressive increase in the rate of the composite end point of death, myocardial infarction, or refractory ischemia at 7 days with an increasing number of risk factors. For patients treated with heparin alone, the composite end point event rate was 6.5% in the group with 0 or 1 predictor, 14.6% in the group with 2 predictors, 22.7% in the group with 3 predictors, and 37.1% in the group with 4 or 5 predictors (p <0.00001). When dividing patients into low- (0 or 1 point), medium- (2 or 3 points), and high-risk (4 or 5 points) groups, the addition of tirofiban to heparin therapy was associated with no significant benefit in the low-risk group, a 5.2% absolute reduction in the medium-risk group (p = 0.05), and a 16% absolute reduction in the high-risk group (p = 0.0055). Thus, we have developed a risk score system using 5 variables that can be used to identify patients at high risk for death and cardiac ischemic events and who experience the greatest benefit from the addition of a glycoprotein IIb/IIIa inhibitor to their treatment regimen.

Section snippets

Patients and end points

We analyzed the 1,915 patients enrolled in the PRISM-PLUS trial.3 In brief, patients with unstable angina or non-ST elevation myocardial infarction were randomly assigned to receive 1 of 3 regimens: tirofiban, tirofiban plus heparin, or heparin alone. Predefined primary end points were death, new myocardial infarction, and refractory ischemia. Myocardial infarction was defined as a new episode of chest pain with new electrocardiographic changes and an increase in serum creatine kinase to 2

Baseline characteristics

The baseline characteristics of the 1,915 patients analyzed in this study are listed in Table 1. Coronary angiography, which was encouraged per protocol, was performed during hospitalization in 90% of patients. Approximately 31% of patients underwent a percutaneous coronary intervention and 23% underwent coronary artery bypass graft surgery (CABG).

Risk factors for major adverse cardiac events

The odds ratio associated with each of the baseline characteristics for both the prespecified primary composite end point of death, myocardial

Discussion

The heterogeneity in outcome among patients presenting with unstable angina has challenged clinicians. The development of new and relatively expensive antiplatelet and antithrombin therapies has only underscored the need for an accurate and simple method for risk stratification in these patients to assist in triage to therapies. In our study, we identified 5 independent risk factors for the composite end point of death, myocardial infarction, or refractory ischemia at 7 days: age >65 years,

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This study was supported in part by a research grant from John and Marilee Polmonari. Drs. Sabatine and Januzzi are recipients of the William A. Schreyer Clinical Fellowship in Cardiology. Manuscript received January 11, 2001; revised manuscript received and accepted April 4, 2001.

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