Aspirin resistance in patients with acute coronary events: Risk factors and prevalence as determined by whole blood multiple electrode aggregometry

Abstract

Objectives: To determine the prevalence of aspirin resistance and associated risk factors based on biochemical parameters using whole blood multiple electrode aggregometry. Methods:The study was conducted at the outpatients cardiology clinic of the Universiti Kebangsaan Malaysia Medical Centre (UKMMC) from August 2011 to February 2012. Subjects on aspirin therapy were divided into two groups; first-ever coronary event and recurrent coronary event. Aspirin resistance was measured by a Multiplate® platelet analyser. Results: A total of 74 patients (63 male, 11 female), with a mean age of 57.93 ± 74.1years were enrolled in the study. The patients were divided into two groups –first-ever coronary event group (n=52) and recurrent coronary event group (n=22). Aspirin resistance was observed in 12 out of 74 (16%) of the study patients, which consisted of 11 patients from the first-ever coronary event group and one patient from the recurrent coronary event group. There were significant correlations between aspirin resistance and age (r = -0.627; p = 0.029), total cholesterol (r = 0.608; p = 0.036) and LDL (r = 0.694; p = 0.012). LDL was the main predictor for area under the curve (AUC) for aspirin resistance. However, there was no association between aspirin resistance and cardiovascular events in both groups in this study. Conclusions: Aspirin resistance was observed in 16% of the study population. LDL was the major predictor of aspirin resistance. No association was found in the study between aspirin resistance with recurrent coronary events.

The Prevalence and Clinical Relevance of ASA Nonresponse After Cardiac Surgery: A Prospective Bicentric Study

“…Nevertheless, the incidence of ASA nonresponse observed postoperatively in this study was markedly higher than the numbers reported in patients without surgical trauma. 4 In addition to the effects of increased platelet turnover and postoperative hypercoagulability described above, the analgesic medication may have contributed to the high rates in ASA nonresponse. Pyrazolone, as well as other nonsteroidal antiinflammatory drugs, has been shown to interfere with the inhibitory effect of ASA on the synthesis of thromboxane within the normal therapeutic range.…”

“…2 The influences by genetic predisposition and risk factors, such as diabetes, obesity, or a metabolic syndrome, are under discussion but have not yet been fully clarified. 3,4 Individuals with a reduced response to ASA treatment had an increased risk of cardiovascular or cerebrovascular events such as myocardial infarction or stroke. 2,5,6 A problem addressed by most meta-analyses was the heterogenous definition of ASA nonresponse in the included studies with different technical devices and laboratory analyses used for the detection of ASA nonresponse.…”

Platelet response to increased aspirin dose in patients with persistent platelet aggregation while treated with aspirin 81 mg

“…Many past studies have concluded that patients are "aspirin resistant" if they exhibit platelet aggregation using whichever method of aspirin sensitivity testing is available, and many times have not increased the dose of aspirin to see if the patient will become responsive to a higher aspirin dose. 27 Thus, the prevalence of "aspirin resistance" might be grossly overestimated and cause clinicians to avoid the use of aspirin and rely on other currently available antiplatelet agents rather than simply increasing the dose of aspirin. In fact, reports of "aspirin resistance" range from 5.5% to 60%, which could be attributed to many factors including the lack of a good definition or be because many of these studies did not attempt to see if patients were sensitive at higher doses.…”

“…Many past studies have concluded that patients are “aspirin resistant” if they exhibit platelet aggregation using whichever method of aspirin sensitivity testing is available, and many times have not increased the dose of aspirin to see if the patient will become responsive to a higher aspirin dose . Thus, the prevalence of “aspirin resistance” might be grossly overestimated and cause clinicians to avoid the use of aspirin and rely on other currently available antiplatelet agents rather than simply increasing the dose of aspirin.…”

Multiple electrode aggregometry – only for cardiologists?

“…Regardless of the definition, multiple electrode aggregometry may help in recognizing patients who are low-responders to antiplatelet treatment. Research performed with multiple electrode aggregometry on patients with acute coronary syndrome showed that almost 5% of this group was acetylsalicylic acidresistant while almost 22% did not react to clopidogrel intake [15]. The same studies revealed that a high level of triglycerides is associated with resistance to clopidogrel.…”