ABC | Volume 113, Nº3, September 2019

Original Article Dracoulakis et al. High platelet activity during ASA use in ACS Arq Bras Cardiol. 2019; 113(3):357-363 Figure 1 – Comparison of COX-1-specific tests (WBPA with AA and VFN) between the acute and late phases. WBPA: whole blood platelet aggregation; AA: arachidonic acid; VFN: VerifyNow™; URA: units of reaction to acetylsalicylic acid. 4 3.5 2.5 1.5 0.5 3 2 1 0 550 504.39 Acute Chronic Phaser Results in Ω of WBPA with AA Results in URA of VFN Acute Chronic Phaser 473.71 p = 0.004 3.06 1.69 p = 0.029 450 350 300 500 400 Table 2 – Comparison of HPR by different platelet tests between the acute and late phases Test Acute Phase Late Phase p HPR HPR PFA 34.2% 40% 0.503 WBPA with AA 31.4% 12.8% 0.015 VFN 32.1% 16% 0.049 WBPA with Col 33.8% 30.8% 0.860 WBPA: whole blood platelet aggregation; AA: arachidonic acid; Col: collagen; PFA: Platelet Function Analyzer (PFA-100 ® ); VFN: VerifyNow™; p: p value. Table 3 – Correlation between platelet tests in the acute phase WBPA with AA WBPA with Col VFN PFA r s –0.429* –0.281* –0.279* WBPA with AA r s 0.498* 0.393* WBPA with Col r s 0.318* * p < 0.05, AA: arachidonic acid; Col: collagen; WBPA: whole blood platelet aggregation; PFA: PFA-100®; r s : Spearman correlation coefficient; VFN: VerifyNow™. patients with ACS or unstable angina undergoing PCI and considered nonresponders by WBPA with AA and adenosine diphosphate (ADP). Patients considered nonresponders to ASA were treated with increasing doses of 100 mg to 300 mg per day, and up to 500 mg, if necessary, with improved therapeutic response. On the other hand, our data demonstrate that, although there is a significant decrease in the incidence of HPR during the chronic phase, a significant percentage of the population still present HPR at this stage. The high rate of platelet turnover that occurs in several situations (including ACS) could be one of the explanations for our findings; however, this mechanism was not analyzed in the present study. As demonstrated in previous studies in diabetic patients in the postoperative period of cardiac surgery, 23-25 the number of circulating immature platelets increases as a consequence of increased platelet consumption, leading to an exponential increase in the platelet turnover rate. In a study by Dillinger et al., 26 comparing different doses of ASA twice daily in diabetic patients with CAD and at least one risk factor, twice daily use of the drug reduced HPR rate when compared to the same dose administered once a day. However, in the CURRENT study, the use of a double dose of ASA showed no benefit when compared to the conventional dose. 27 Another possibility would be the influence of the inflammatory process, which is characteristic of the acute phase, on platelet function, resulting in increased platelet activation and increased HPR in response to ASA. In the present study, there was a significant but weak association between inflammation and platelet reactivity, analyzed by PCR and VNF, respectively (r = 0.293, p = 0.03). In a stable CAD population, Bernlochner et al. 28 showed a significant, positive and independent association between CRP levels and platelet aggregation, which were assessed by WBPA with ADP. Similarly, Tantry et al. 29 reported a significant correlation between inflammatory markers 360