Perioperative changes of response to antiplatelet medication in vascular surgery patients

Monitoring antiplatelet therapy: where are we now?

Single antiplatelet therapy represents the cornerstone of thrombosis prevention in atherosclerotic cardiovascular disease. Dual antiplatelet therapy (DAPT), consisting of aspirin plus a P2Y12 inhibitor, is the standard of care for patients with acute coronary syndrome or undergoing both coronary and peripheral percutaneous interventions. Recent data suggest the efficacy of DAPT also after minor stroke. In this setting, a large body of evidence has documented that genetic and acquired patients' characteristics may affect the magnitude of platelet inhibition induced by antiplatelet agents. The implementation of tools allowing the identification and prediction of platelet inhibition has recently been shown to improve outcomes, leading to an optimal balance between antithrombotic efficacy and bleeding risk. We are therefore clearly moving towards tailored antiplatelet therapy. The aim of this paper is to summarize the available evidence on the evaluation of platelet inhibition in patients with coronary, peripheral, or cerebrovascular atherosclerosis. We will here focus on antiplatelet therapy based on both aspirin and P2Y12 inhibitors. In addition, we provide practical insights into the clinical settings in which it appears reasonable to implement antiplatelet therapy monitoring.

Association of PeriOPerative Aspirin-ResisTance and CardioVascular Outcome (POPART- CVO) - a prospective non-interventional cohort study

OBJECTIVES

New onset of aspirin-resistance during surgery, known as perioperative aspirin-resistance, is observed in up to 30% of vascular surgery patients and is associated with post-OP myocardial damage; questioning aspirin effectiveness towards perioperative cardiovascular events. The objective of this study was to prospectively evaluate whether perioperative aspirin-resistance in vascular surgery is associated with adverse cardiovascular outcome.

DESIGN AND METHODS

Based on a sample size calculation, 194 adult elective vascular or endovascular surgery patients receiving aspirin were analyzed in this prospective, single-centered, non-interventional cohort study. Platelet function was measured before surgery, one hour after incision, four hours postoperatively, and on the morning of the first and second postoperative days using the Multiplate® analyzer. The primary outcome was Myocardial Injury after Non-Cardiac Surgery (MINS). Secondary outcomes included major bleeding, admission to intensive care unit, length of hospital stay, and Major Adverse Cardiac and Cerebrovascular Events. Subgroup analyses were performed for patients with different cardiovascular risk and for patients who underwent endovascular surgery.

RESULTS

Perioperative aspirin-resistance was observed in 27.8% of patients but was not associated with MINS (27.8% vs. 32.1%, aspirin-resistance vs. no aspirin-resistance, OR 0.812, 95% CI [0.406;1.624], p=.555) or with any of the secondary endpoints (all p>.05). In nine of the ten subgroup analyses, aspirin-resistance was not associated with a difference in MINS rate. However, in patients with a low cardiovascular risk profile (RCRI 0-2), MINS occurred more frequently in patients without aspirin-resistance (p=.049).

CONCLUSIONS

We confirmed previous reports demonstrating that perioperative aspirin-resistance is frequent in patients undergoing vascular or endovascular surgery. However, in patients who continue aspirin throughout the perioperative period, aspirin-resistance is a phenomenon, that does not appear to be related to MINS. Measuring perioperative platelet function using the Multiplate® analyzer with the intention to identify and potentially prevent or treat perioperative aspirin-resistance seems to be dispensable.

Platelet reactivity testing in peripheral artery disease

DISCLAIMER

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PURPOSE

Oral antiplatelet therapy is routinely used to prevent adverse cardiovascular events in patients with peripheral artery disease (PAD). Several laboratory tests are available to quantify the degree of platelet inhibition following antiplatelet therapy. This article aims to provide a review of the literature surrounding platelet functional testing in patients with PAD receiving oral P2Y12 inhibitors and to offer guidance to clinicians for the use and interpretation of these tests.

SUMMARY

A literature search of PubMed and the Web of Science Core Collection database was conducted. All studies that performed platelet function testing and reported clinical outcomes in patients with PAD were included. Evaluation of the data suggests that, among the available testing strategies, the VerifyNow platelet reactivity unit (PRU) test is the most widely used. Despite numerous investigations attempting to define a laboratory threshold indicating suboptimal response to antiplatelet therapy, controversy exists about which PRU value best correlates with cardiovascular outcomes (ie, mortality, stent thrombosis, etc). In the PAD literature, the most commonly used PRU thresholds are 208 or higher and 235 or higher. Nonetheless, adjusting antiplatelet regimens based on suboptimal P2Y12 reactivity values has yet to be proven useful in reducing the incidence of adverse cardiovascular outcomes. This review examines platelet function testing in patients with PAD and discusses the interpretation and application of these tests when monitoring the safety and efficacy of P2Y12 inhibitors.

CONCLUSION

Although platelet functional tests may be simple to use, clinical trials thus far have failed to show benefit from therapy adjustments based on test results. Clinicians should be cautioned against relying on this test result alone and should instead consider a combination of laboratory, clinical, and patient-specific factors when adjusting P2Y12 inhibitor therapy in clinical practice.