Background: Aspirin is one of the main therapeutics in prevention of cardiovascular events due to its antiplatelet activity. However, a sufficient inhibition of platelet function by aspirin is not always achieved. This means that the extent of protection from cardiovascular event is limited. Recently, several studies have introduced the concept of residual platelet reactivity during aspirin therapy and suggested that about 40% of aspirin users may not respond adequately. We sought to determine whether the profile and prevalence of residual platelet reactivity, measured with the platelet function analyzer (PFA-100; Dade/Behring, Marburg, Germany) device could predict a recurrent cardiovascular event in patients undergoing coronary artery bypass surgery.
Methods: A cohort of 202 consecutive patients receiving primary coronary artery bypass surgery during 2004 was prospectively recruited. All patients postoperatively received regular standard daily 100 mg aspirin. Platelet function was analyzed by the PFA-100 at 30 +/- 6 days after surgery. A PFA100 closure time less than 190 seconds was defined as residual platelet reactivity. Eighty-six patients (43%) showed residual platelet reactivity. The mean follow-up time was 32 +/- 10 months and was 100% complete.
Results: A total of 75 cardiovascular events have been registered. The majority of these events were among patients with residual platelet activity (p = 0.001). Out of this number, graft failure was documented in 25 patients. The 42-month freedom from major cardiovascular events was significantly better for patients with adequate platelet inhibition (p = 0.001). At multivariable analysis residual platelet reactivity (p = 0.012), incomplete revascularization (p = 0.029), and diabetes (p = 0.0009) were independently associated with occurrence of negative events.
Conclusions: Our results demonstrate that high residual platelet reactivity independently correlates with a worst clinical outcome in patients treated by coronary artery bypass surgery. The PFA-100 point care test could cheaply and simply discover this condition and contribute to improve the outcome of this subset of patients.