Outcomes according to cardiac catheterization referral and clopidogrel use among medicare patients with non-ST-segment elevation myocardial infarction discharged without in-hospital revascularization

Background-While use of P2Y12 receptor inhibitor is recommended by guidelines, few studies have examined its effectiveness among older non-ST-segment elevation myocardial infarction patients who did not undergo coronary revascularization. Methods and Results-We included unrevascularized non-ST-segment elevation myocardial infarction patients ≥65 years discharged home from 463 ACTION Registry-GWTG hospitals from 2007 to 2010. Rates of discharge clopidogrel use were described for patients with no angiography, angiography without obstructive coronary artery disease (CAD; ≥50% stenosis in ≥1 vessel), and angiography with obstructive CAD. Two-year outcomes were ascertained from linked Medicare data and included composite major adverse cardiac events (defined as all-cause death, myocardial infarction readmission, or revascularization), and individual components. Outcomes associated with clopidogrel use were adjusted using inverse probability-weighted propensity modeling. Of 14 154 unrevascularized patients, 54.7% (n=7745) did not undergo angiography, 10.6% (n=1494) had angiography without CAD, and 34.7% (n=4915) had angiography with CAD. Discharge clopidogrel was prescribed for 42.2% of all unrevascularized patients: 37.8% without angiography, 34.1% without obstructive CAD at angiography, and 51.6% with obstructive CAD at angiography. Discharge clopidogrel use was not associated with major adverse cardiac events in any group: without angiography (adjusted hazard ratio [95% CI]: 0.99 [0.93-1.06]), angiography without CAD (1.04 [0.74-1.47]), and angiography with CAD (1.12 [1.00-1.25], P_interaction=0.20). Conclusions-We found no association between discharge clopidogrel use and long-term risk of major adverse cardiac events among older, unrevascularized non-ST-segment elevation myocardial infarction patients. Clopidogrel use in this population requires further prospective evaluation.