Variable platelet response to aspirin and clopidogrel is a well-known phenomenon in patients with coronary artery disease and ischemic cerebral stroke. The objective of the present study was to evaluate the frequency and possible risk factors of antiplatelet resistance in patients with cerebrovascular and cardiovascular diseases. The VerifyNow system was used to evaluate adenosine-5-diphosphate and platelet P2YI2 receptor function in patients with cerebrovascular and cardiovascular disease, who received dual antiplatelet therapy. Aspirin resistance was defined as aspirin reaction units (ARU) ≥ 550. Clopidogrel resistance was defined as Platelet Reaction Units (PRU) > 230. In the group of cerebrovascular diseases there were 13.2% (n = 27) patients with aspirin and 24.5% (n = 50) with clopidogrel resistance. However, in the cardiovascular group there were 20% (n = 9) aspirin and 11.1% (n = 5) clopidogrel resistant patients. In the cerebrovascular group, aspirin resistant patients had a lower triglyceride level (p = 0.001, r = 0.26) than aspirin sensitive patients. Clopidogrel resistant patients had a significantly higher level of glycated haemoglobin (HbA1C) (p = 0.016, r = 023), triglycerides (p = 0.033, r = 0.16) and lower level of high-density lipoproteins (p = 0.027, r = 0.16) than clopidogrel sensitive patients. In the cardiovascular group, patients who were resistant to aspirin had a significantly higher high-density lipoprotein level (p = 0.038, r = 0.31). No other factors differed significantly between the aspirin or clopidogrel resistant and sensitive patients in the cardiovascular group. Aspirin resistance was more common in patients with cardiovascular disease, and clopidogrel resistance in patients with cerebrovascular disease, although the difference was not significant. Our findings indicate that diabetes mellitus and an elevated level of lipoproteins could be risk factors for aspirin or clopidogrel resistance in patients with cerebrovascular diseases. Further studies should be conducted using larger patient cohorts with balanced groups of patients to investigate clinical aspects of antiplatelet resistance.

INTRODUCTION: Cardiovascular diseases and stroke are steadily the leading causes of death in Latvia. Therefore, the greatest efforts should be given to recognize associative factors which may be modifiable to decrease the burden of ischemic events. OBJECTIVES: The aim of this study was to examine the frequency of aspirin and clopidogrel resistance and its associated risk factors in patients with acute cerebrovascular events. METHODS: The prospective, descriptive study included 204 patients. Patients were considered biochemical resistant to aspirin if platelet aggregation was ≥550 ARU, whereas biochemical clopidogrel resistance was defined when platelet inhibition was >230 PRU.RESULTS: Biochemical aspirin resistance was found in 27 (13%) patients, whereas clopidogrel resistance -in 44 (22%) patients. Five patients (2%) had resistance to both antiplatelet drugs. In the analysis of blood parameters, none were associated with aspirin resistance, except the level of triglycerides which were lower in the aspirin resistance group (p=0.001; r=0.26). In the analysis of clopidogrel sensitivity there was a difference in diabetes prevalence where it was more frequent in the clopidogrel resistance group (15.6% vs. 40.9%; p=0.001; r=0.255). Patients with clopidogrel resistance had higher levels of triglycerides 1.7 (1.3-2.6) than patients grouped as sensitive 1.4 ((1.1-2.0), p=0.033; r=0.16). CONCLUSION: Biochemical aspirin and clopidogrel resistance are quite common in patients with cerebrovascular diseases in Latvia. Our study found that patients with diabetes and elevated glycosylated hemoglobin level were more prone to clopidogrel biochemical resistance. However, the association between aspirin resistance and clinical, laboratory data remains inconclusive.