Dual versus Single Antiplatelet Therapy in Medically Treated Acute Myocardial Infarction Patients with Baseline Thrombocytopenia - Insights from a Multi-Institute Cohort Study.

Background: The safety and efficacy of dual antiplatelet therapy (DAPT) in medically treated acute myocardial infarction (AMI) patients with baseline thrombocytopenia (platelet count < 150 × 10/uL) are unclear.

Methods: In this multi-institute retrospective cohort study, we included 468 patients with medically treated AMI with baseline thrombocytopenia and separated them into single antiplatelet therapy (SAPT) and DAPT groups according to the discharge anti-thrombotic strategy. The primary outcome was net clinical adverse events (NACEs), defined as a composite of death, ischemic events (myocardial infarction, ischemic stroke, and transient ischemic attack), and major bleeding within 30 days.

Results: There were 168 patients in the SAPT group (100 taking aspirin and 68 taking clopidogrel) and 300 in the DAPT group. A primary outcome occurred in 35 (24.11 per 100 patient-months) patients in the SAPT group and 39 (14.26 per 100 patient-months) patients in the DAPT group [adjusted hazard ratio (HR): 0.67; 95% confidence interval (CI): 0.40-1.10; p = 0.1145]. Kaplan-Meier curves showed favorable results in the DAPT group (log-rank p = 0.0243). Bleeding events occurred in 18 (10.71 per 100 patient-months) patients in the SAPT group and 18 (6.40 per 100 patient-months) patients in the DAPT group (adjusted HR: 0.66; 95% CI: 0.32-1.36; p = 0.2573).

Conclusions: DAPT versus SAPT as discharge anti-thrombotic strategy in thrombocytopenic patients with medically treated AMI did not significantly improve NACEs at 30 days. However, there was a trend towards favorable outcomes in the DAPT group. These results should be interpreted carefully with respect to the relatively limited trial population and study design.