PCI in The Patient With Resistance to Aspirin

Overview
The treatment for antiplatelet drug resistance is not well defined. Detailed patient evaluation and correcting possible clinical causes and factors may be the initial therapeutic steps. Careful drug choose to reduce possible interactions, optimizing blood glucose and cholesterol levels are also beneficial.

Administration of higher doses of Aspirin is evaluated and currently not an actual therapeutic strategy for the lack of evidence demonstrating improvement in clinical outcomes. Increasing the dose of aspirin has been suggested as a measure to overcome aspirin resistance but it is possible that increased doses of aspirin may overcome aspirin resistance in vitro in an individual patient. Higher doses of aspirin may also increase bleeding events.

Clinical Trial Data
CAPRIE study (Clopidogrel versus Aspirin in Patients at Risk of Ischemic Events)

Although, whether clopidogrel therapy is superior to aspirin in aspirin resistant patients is currently unknown, CAPRIE study investigators reported significant superiority of clopidogrel monotherapy over aspirin monotherapy. This beneficial effect was more frequently observed in high risk patients.

In fact, aspirin resistance is more frequent finding in high risk patients, such as diabetics and patients with diffuse atherosclerotic disease or acute coronary syndromes. This group or patients also have increased risk of recurrent ischemic events

ASCET trial (ASpirin non-responsiveness and Clopidogrel Endpoint Trial)

ISAR-REACT study (Intracoronary Stenting and Antithrombotic Regimen - Rapid Early Action for Coronary Treatment) data suggest that in patients at low to intermediate risk who undergo elective PCI after pretreatment with a high loading dose of clopidogrel, the use of a GP IIb/IIIa inhibitor, although more potent, is associated with no clinically measurable benefit within the first 30 days. In contrast, high-risk patients should receive triple antiplatelet therapy.

A low to medium risk patients study suggests that aspirin and clopidogrel may be insufficient in aspirin non responsive patients and resulted in quite similar results of ISAR-REACT.

Both study results indicate that there is a gap between applied medication and requirements for optimal antiplatelet treatment. Most interventional cardiologists give aspirin, clopidogrel, and heparin alone before PCI, however, up to 25% of these patients are aspirin non responsive.


 * RESISTOR trial (Research Evaluation to Study Individuals who Show Thromboxane Or P2Y12 Receptor Resistance)