Introduction:
Aspirin (ASA) therapy reduces the risk of thrombotic events by inhibiting platelet aggregation, however some individuals have a diminished response to ASA. The ability to predict ASA non-responsiveness has important therapeutic implications. We studied patients with suspected acute coronary syndrome (ACS) to determine the characteristics of patients with ASA non-responsiveness.
Methods:
We enrolled 1010 patients with suspected ACS in the emergency departments (ED’s) of 5 sites. All subjects were on outpatient ASA therapy or received ASA in the ED, and were excluded if on clopidogrel. Blood was tested for ASA non-responsiveness (defined as ASA reactive units ≥ 550) on a VerifyNow® (Accumetrics) device.
Results:
Overall prevalence of ASA non-responsiveness was 10.3% (95% C.I. 8.6–12.3%). Responsiveness to ASA did not differ by age or sex, but varied significantly by race. Hispanics had a higher prevalence of ASA non-responsiveness, while whites and Asians had a lower prevalence (
Figure
). Other factors associated with increased prevalence of ASA resistance included outpatient ASA therapy (p<0.001), a history of alcohol (p=0.045) or drug abuse (p=0.02), a history of heart failure (p=0.01), and renal insufficiency (p=0.003). Patients with ASA non-responsiveness had lower BMI (p=0.006) and hemoglobin (p<0.001), and higher BNP levels (p<0.001), prothrombin time (p=0.01), and partial thromboplastin time (p<0.001).
Conclusions:
Among suspected ACS patients, the prevalence of ASA non-responsiveness varies by race and is highest in Hispanics. ASA resistance is also more prevalent in patients with clinical characteristics consistent with poorer health.
Prevalence of ASA Non-Responsiveness by Race
Factors Associated With Primary Vein Graft Thrombosis in a Multicenter Trial With Mandated Ultrasound Surveillance