Dual Antiplatelet Therapy Score Utility for Risk Prediction
What is the utility of a decision tool for prescription of dual antiplatelet therapy (DAPT) duration in patients with or without prior myocardial infarction (MI) treated with coronary stents?
Patients were categorized according to any history of MI prior to the index procedure, or no history of MI. Risk differences during the randomized treatment period (12-30 months) for ischemic (MI and/or stent thrombosis [ST]) and bleeding (GUSTO moderate/severe) events were compared according to DAPT score. The consistency of the treatment effect between patients with any MI and patients with no MI was evaluated through Cox proportional hazards regression models with the main effects of randomized treatment and prior MI status and the inclusion of prior MI status by randomized treatment interaction term.
Rates of MI were 3.8% vs. 2.4% (p = 0.01), for patients with any MI versus no MI. Continued thienopyridine reduced late MI compared with placebo regardless of MI history (hazard ratios 0.46, p < 0.001 any MI; 0.60, p = 0.003 no MI) and increased bleeding (1.86, p = 0.01; 1.58, p = 0.01). DAPT scores ≥2 were associated with reductions in MI/ST with continued thienopyridine (vs. placebo) (2.7% vs. 6.0%, p < 0.001 any MI; 2.6% vs. 5.2%, p = 0.002 no MI), with bleeding rates of 1.5% vs. 1.1%, p = 0.24; 2.2% vs. 2.0%, p = 0.68. Among patients with DAPT scores <2, in both groups, continued thienopyridine was associated with increased bleeding (3.2% vs. 1.2%, p = 0.01; 2.9% vs. 1.6%, p = 0.004, respectively), and ischemic rates of 2.1% vs. 3.2%, p = 0.17; 1.5% vs. 2.0%, p = 0.21.
The authors concluded that the DAPT score improves prediction of patient benefit and harm from continued DAPT beyond assessment of MI history alone.
This post hoc study suggests that patients with any MI before percutaneous coronary intervention (PCI) have increased risk for ischemic events (vs. patients with no MI) in the year after PCI despite DAPT, and have higher rates of ischemic events than do patients with no MI between 12-30 months following PCI. The relative treatment benefit of prolonged thienopyridine therapy after PCI was consistent across patients stratified by MI status, but absolute reductions in ischemic event rates were greater among patients with any MI. Furthermore, the DAPT score further stratifies individual patients according to expected treatment benefit versus harm of prolonged (>12 months) DAPT compared with MI status only. It should be noted that the DAPT score was designed for the ‘DAPT–like’ population of patients who do not have events for the first 12 months, who do not have contraindications to DAPT, and who are tolerating dual therapy. Thus, caution is indicated for use of this prediction score until further prospective validation in other cohorts is performed, and optimal clinical and procedural care to reduce overall bleeding and ischemic risks should be practiced independent of a patient’s score.
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