Functional Evaluation of Platelet Aspirin Resistance after On-Pump Coronary Bypass Grafting Using Multiple Aggregation Tests

Cilostazol increases adenosine plasma concentration in patients with acute coronary syndrome

WHAT IS KNOWN AND OBJECTIVE

Cilostazol is a specific and strong inhibitor of phosphodiesterase (PDE) type III which can suppress the platelet aggregation by increasing cyclic adenosine monophosphate (cAMP) levels. The clinical benefit of cilostazol in ACS patients suggested that the drug may have non-platelet-directed properties. Some in vitro and animal studies also indicated that the 'pleiotropic' properties of cilostazol might be related to the interaction with adenosine metabolism. Adenosine is an important regulatory metabolite and an inhibitor of platelet activation. However, no human study has been conducted to determine whether cilostazol could increase the adenosine plasma concentration in vivo. As a result, this study aimed to investigate the impact of cilostazol on adenosine plasma concentration (APC) in acute coronary syndrome (ACS) patients.

METHODS

We prospectively analysed 149 ACS patients undergoing percutaneous coronary intervention (PCI) with drug-eluting stents. The included patients were divided into two groups according to the presence (cilostazol group, n = 64) or absence (aspirin group, n = 85) of aspirin intolerance. The inhibition of platelet aggregation (IPA), APC and cAMP concentration was measured. Patient characteristics, medications and 30-day clinical outcomes were examined.

RESULTS

Patients receiving cilostazol had a significantly higher adenosine and cAMP plasma concentration than patients receiving aspirin (3.00 ± 0.67 vs 2.56 ± 0.74 mol/L, P < .001; 28.10 ± 14.74 vs 20.48 ± 11.35 pmol/mL, P = .0014). Cilostazol was associated with a higher inhibition rate of ADP induced platelet aggregation than aspirin (63.35 ± 26.71 vs 52.2 ± 28.35, P = .036). The plasma levels of adenosine and cAMP showed a positive correlation with ADP induced platelet aggregation.

WHAT IS NEW AND CONCLUSION

Cilostazol increases adenosine concentration compared with aspirin. Its potent antiplatelet effect in ACS patients may be partly mediated by adenosine.

Low platelet activity predicts 30 days mortality in patients undergoing heart surgery

Despite advanced techniques and improved clinical outcomes, patient survival following coronary artery bypass grafting (CABG) is still a major concern. Therefore, predicting future CABG mortality represents an unmet medical need and should be carefully explored. The objective of this study is to assess whether pre-CABG platelet activity corresponds with 30 days mortality post-CABG. Retrospective analyses of platelet biomarkers and death at 30 days in 478 heart surgery patients withdrawn from aspirin or/and clopidogrel. Platelet activity was assessed prior to CABG for aspirin (ASPI-test) with arachidonic acid and clopidogrel (ADP-test) utilizing Multiplate impedance aggregometer. Most patients (n = 198) underwent conventional CABG, off-pump (n = 162), minimally invasive (n = 30), artificial valve implantation (n = 48) or valves in combination with CABG (n = 40). There were 22 deaths at 30 days, including 10 in-hospital fatalities. With the cut-off value set below 407 area under curve (AUC) for the ASPI-test, the 30-day mortality was 5.90% for the lower cohort and 2.66% for patients with significantly higher platelet reactivity (P = 0.038). For the ADP-test with a cut-off at 400AUC, the 30-day mortality was 9.68% for the lower cohort and 3.66% for patients with higher platelet reactivity, representing a borderline significant difference (P = 0.046). Aside from the platelet indices, patients who received red blood cell (RBC) concentrate had a highly significant (P < 0.0001) risk of death at 30 days. Both aspirin and clopidogrel tests were useful in predicting 30 days mortality following heart surgery, suggesting the danger of diminished platelet activity prior to CABG in such high-risk patients. These preliminary evidence supports early discontinuation of antiplatelet therapy for elective CABG and requires adequately powered randomized trials to test the hypothesis and potentially improve survival.

Drug delivery and therapeutic impact of extended-release acetylsalicylic acid

Current treatment guidelines recommend once-daily, low-dose acetylsalicylic acid (ASA; aspirin) for secondary prevention of cardiovascular events. However, the anti-thrombotic benefits of traditional ASA formulations may not extend over a 24-h period, especially in patients at high risk for a recurrent cardiovascular event. A next-generation, extended-release ASA formulation (ER-ASA) has been developed to provide 24-h anti-thrombotic coverage with once-daily dosing. The pharmacokinetics of ER-ASA indicates slower absorption and prolonged ASA release versus immediate-release ASA, with a favorable safety profile. ER-ASA minimizes systemic ASA absorption and provides sustained antiplatelet effects over a 24-h period.