A risk score to estimate the likelihood of coronary artery bypass surgery during the index hospitalization among patients with unstable angina and non-ST-segment elevation myocardial infarction

OBJECTIVES A simple risk score on admission to estimate the likelihood of in-hospital coronary artery bypass graft surgery (CABG) might be useful in selecting patients for early clopidogrel therapy. BACKGROUND Routine early use of clopidogrel in patients with unstable angina (UA) and non-ST-segment elevation myocardial infarction (NSTEMI) is associated with increased risk of bleeding in patients who undergo early CABG. METHODS The test cohort utilized to derive the score was the 2,220 patients with UA/NSTEMI enrolled in the Treat Angina with Aggrastat and Determine Cost of Therapy with an Invasive or Conservative Strategy-Thrombolysis in Myocardial Infarction-18 (TACTICS-TlMI-18) trial. Patients who under-went CABG after randomization during index hospitalization were identified and were compared with patients who did not undergo in-hospital CABG. RESULTS Overall, 362 patients (16.3%) underwent CABG during the index hospitalization. Patients with a history of prior CABG (n = 484) were significantly less likely to undergo in-hospital CABG (odds ratio [OR], 0.34). Five additional variables independently associated with CABG were identified: elevated troponin (OR, 3.9), prior stable angina (OR, 1.8), ST-segment deviation greater than or equal to0.5 mm (OR, 1.7), male gender (OR, 1.6), and history of peripheral arterial disease (OR, 1.6). A CABG risk score was generated by assigning numerical values to each of the variables based upon these odds ratios. Coronary artery bypass surgery rates increased significantly with increasing risk scores (6.2% for a risk score <3.0, 21.9% for 3 to 5, and 54.6% for >5.0). The association of the risk score with CABG was highly significant (p < 0.0001, c-statistic 0.72). The association remained significant in the validation cohorts from TIMI-IIB trial and TIMI-III registry. CONCLUSIONS Among patients with UA/NSTEMI, a novel risk score based on admission clinical variables can be used to estimate the likelihood of CABG. These data may assist in the identification of patients who might derive optimal benefit from early initiation of clopidogrel therapy. (C) 2004 by the American College of Cardiology Foundation.