Resistance to Aspirin Associated to Greater Risk of In-Stent Thrombosis and Death

Original title: Aspirin Treatment and Outcomes After Percutaneous Coronary InterventionResults of the ISAR-ASPI Registry. Reference: Katharina Mayer et al. J Am CollCardiol. 2014;64(9):863-871.

Aspirin administration, as part of the double antiagregation scheme, is essential in the context of PCI. The correlation between high platelet reactivity to on-clopidogrel treatment and higher events rates has been well established, while data on high platelet reactivity to on-aspirin treatment remains inconclusive. 

The ISAR-ASPI registry (Intracoronary Stenting and Antithrombotic Regimen – Aspirin and Platelet Inhibition) aimed at evaluating whether high antiplatelet reactivity to aspirin could be a possible predictor in PCI patients.

This study included 7090 consecutive PCI patients between February 2007 and May 2013. On-aspirin antiplatelet reactivity was measured right before procedure with the Multiplate analyzer and primary end point was death and in-stent thrombosis at one year. The upper quintile patients, n=1414 according to measurements, was defined as the aspirin resistant cohort. 

Compared to patients not resistant to aspirin (n=5676) those in the first group showed a significantly higher risk of death or in-stent thrombosis at one year (6.2% vs. 3.7% respectively; OR 1.78IC 95% 1.39 a 2.27; p < 0.0001).

Resistance to aspirin resulted an independent predictor of primary end point (HR adjusted 1.46; CI 95% 1.12 to 1.89; p=0.005).

Conclusion

Aspirin resistance when confirmed right before PCI is associated to a higher risk of death and in-stent thrombosis within the first year.

Editorial Comment

Even though it is clear that high on-aspirin platelet reactivity correlates with higher adverse events rates, on-clopidogrel treatment also represents a risk, and the way to reduce it still calls for research. Studies on clopidogrel administration with higher loading doses or double daily doses were not conclusive as to whether risk rates, after these interventions, matched the sensitive population rates.

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