Researchers from Beth Israel Deaconess Medical Center, Boston, developed a clinical prediction score showing modest accuracy in assessing ischemic and bleeding risks with dual antiplatelet therapy (DAPT) following coronary stent placement. Findings from the study are published in JAMA

Dual antiplatelet therapy reduces ischemia but carries an increased risk of bleeding. Evidence is not clear on which patients are at high risk for late ischemic events and would have the greatest benefit from longer dual antiplatelet therapy vs. patients at high risk for late bleeding events who may be harmed by continued treatment. 

Robert W. Yeh, MD, MSc, and colleagues designed a study to identify factors that would predict patients expected to derive benefit vs. harm from continued dual antiplatelet therapy beyond 1 year after coronary stent placement. Study patients from the DAPT Study (n=11,648) and the PROTECT trial (n=8,136) were included. They were exposed to 12 months of open-label thienopyridine + aspirin, then randomized to 18 months of continued thienopyridine + aspirin vs. placebo + aspirin. The main outcome measure was ischemia (myocardial infarction [MI] or stent thrombosis) and bleeding (moderate or severe) 12–30 months post-percutaneous coronary intervention (PCI). 

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Data for the DAPT Study showed ischemia occurring in 348 patients (3.0%) and bleeding in 215 patients (1.8%). The prediction rule designated 1 point each for MI at presentation, prior MI or PCI, diabetes, stent diameter <3mm, smoking, and paclitaxel-eluting stent; 2 points each for history of congestive heart failure/low ejection fraction and vein graft intervention; −1 point for age 65–<75 years; and −2 points for age ≥75 years.

For patients in the high score group (score ≥2), continued thienopyridine vs. placebo led to reduced ischemic events (2.7% vs. 5.7%, risk difference -3.0, 95% CI: -4.1% to -2.0%; P<0.001) compared to the low score group (1.7% vs. 2.3%, risk difference -0.7%, 95% CI: -1.4% to 0.09%; P<0.001). Continued use of  thienopyridine in patients with higher scores was associated with smaller increases in bleeding compared to the low score group. In this study, continued thienopyridine use resulted in an absolute risk reduction in MI or stent thrombosis that was 8.2 times greater than the absolute risk increase in bleeding.

Data for the PROTECT trial patients showed ischemia occurring in 79 patients (1.0%) and bleeding in 37 patients (0.5%). The high score patients in this group experienced more ischemic events vs. the low score patients and showed no significant difference in bleeding. 

The prediction rule to assess late ischemic and bleeding risks for determining duration of dual antiplatelet therapy demonstrated modest accuracy. “Use of this prediction score should be cautious until further validation is performed, and optimal clinical and procedural care to reduce overall bleeding and ischemic risks should be practiced independent of score,” Dr. Yeh noted.

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