More and Better Options Needed for Patients with Resistance to Triple Antiplatelet Therapy After PCI
Almost one quarter of patients undergoing PCI for coronary artery disease may be resistant to either aspirin or clopidogrel.
There is a need for a proper therapeutic modality for patients with resistance to aspirin or clopidogrel administered as part of triple antiplatelet therapy after percutaneous coronary intervention (PCI), according to researchers from Yonsei University College of Medicine, Seoul, South Korea.
In a primarily Korean population, resistance to both drugs was 0.96% and resistance to either drug was 23.08%, said researchers, led by Se-Jung Yoon, MD, Yonsei Cardiology Hospital, Seoul.
Resistance prevalence
Antiplatelet therapy is effective in preventing subacute thrombosis after intracoronary stenting in patients with coronary artery disease (CAD), but more data are needed to understand responses to triple antiplatelet therapy with aspirin, clopidogrel, and cilostazol.
To understand resistance to these agents, Yoon and colleagues looked at aspirin and clopidogrel resistance prospectively in 104 patients who received triple antiplatelet therapy (aspirin 100 mg, clopidogrel 75 mg, and cilostazol 100 mg) for at least two weeks after coronary angiography and PCI.
Seven patients (6.7%) were resistant to aspirin, and 19 patients (18.1%) were resistant to clopidogrel.
Some response
The majority of patients (79 patients, or 75.96%) were responsive to both aspirin and clopidogrel. Eighteen patients (17.31%) were responsive to aspirin but resistant to clopidogrel. Six patients (5.77%) were resistant to aspirin but responsive to clopidogrel. One patient (0.96%) was resistant to both drugs.
The mean patient age was 63 ± 10 years, and 65 patients were men.
The researchers used the Ultegra Rapid Platelet Function Assay-Aspirin and Clopidogrel (Verify Now, Accumetrics Inc.) to determine resistance to aspirin and clopidogrel. Aspirin resistance was defined as aspirin reaction units of at least 550. Clopidogrel resistance was based on an inhibition rate below 20%.