A case of resistance to clopidogrel and prasugrel after percutaneous coronary angioplasty

Resistance on the Latest Oral and Intravenous P2Y12 ADP Receptor Blockers in Patients with Acute Coronary Syndromes: Fact or Myth?

Novel P2Y12 ADP receptor blockers (ADPRB) should be preferred in dual-antiplatelet therapy in patients with acute coronary syndrome. Nevertheless, there are still patients who do not respond optimally to novel ADP receptor blocker therapy, and this nonoptimal response (so-called "high on-treatment platelet reactivity" or "resistance") could be connected with increased risk of adverse ischemic events, such as myocardial re-infarction, target lesion failure and stent thrombosis. In addition, several risk factors have been proposed as factors associated with the phenomenon of inadequate response on novel ADPRB. These include obesity, multivessel coronary artery disease, high pre-treatment platelet reactivity and impaired metabolic status for prasugrel, as well as elderly, concomitant therapy with beta-blockers, morphine and platelet count for ticagrelor. There is no literature report describing nonoptimal therapeutic response on cangrelor, and cangrelor therapy seems to be a possible approach for overcoming HTPR on prasugrel and ticagrelor. However, the optimal therapeutic management of "resistance" on novel ADPRB is not clear and this issue requires further research. This narrative review article discusses the phenomenon of high on-treatment platelet reactivity on novel ADPRB, its importance in clinical practice and approaches for its therapeutic overcoming.

Oral antiplatelet therapy and platelet inhibition: An experience from a tertiary care center

AIMS AND OBJECTIVES

Although clopidogrel combined with aspirin is the most commonly used dual drug combination to avert thrombotic events in patients with coronary artery disease, the poor responsiveness to clopidogrel remains a concern. The objective of the current study is to assess the extent of resistance to clopidogrel, prasugrel, and ticagrelor in a real life set of patients with coronary artery disease who underwent percutaneous coronary intervention (PCI).

MATERIALS AND METHODS

A total of 539 patients, who underwent PCI and were on aspirin and on any of the three drugs, namely, clopidogrel, prasugrel and ticagrelor, were followed up regularly in the outpatient department. After 24h of initiation of antiplatelet medication, response to the treatment in all the patients was assessed using thrombelastography. The average percentage platelet inhibition was assessed along with the resistance and sensitivity to the drug in each patient. Sensitivity and resistance to the specific drug was defined as >50% and <50% of mean platelet inhibition, respectively.

RESULTS

About 99.15% of the patients treated with ticagrelor were sensitive to the drug and the difference between ticagrelor, clopidogrel, and prasugrel groups for sensitivity was significant with a p value of 0.00001, in favor of ticagrelor. It was also found that ticagrelor was significantly (p value of 0.001) associated with least resistance as compared with the other drugs assessed in the study.

CONCLUSIONS

Use of ticagrelor as dual therapy along with aspirin in patients with coronary artery disease (CAD) and undergoing PCI was associated with a significantly higher mean percentage platelet inhibition, higher sensitivity, and lower resistance as compared with the usage of clopidogrel or prasugrel.

Type 2 Diabetes and ADP Receptor Blocker Therapy

Type 2 diabetes (T2D) is associated with several abnormalities in haemostasis predisposing to thrombosis. Moreover, T2D was recently connected with a failure in antiplatelet response to clopidogrel, the most commonly used ADP receptor blocker in clinical practice. Clopidogrel high on-treatment platelet reactivity (HTPR) was repeatedly associated with the risk of ischemic adverse events. Patients with T2D show significantly higher residual platelet reactivity on ADP receptor blocker therapy and are more frequently represented in the group of patients with HTPR. This paper reviews the current knowledge about possible interactions between T2D and ADP receptor blocker therapy.

High On-Treatment Platelet Reactivity Associated With Prasugrel

Objective: To report a case of high on-treatment platelet reactivity (HTPR) with prasugrel maintenance therapy despite adequate initial platelet response to a loading dose. Case Summary: A 51-year-old woman presented to the emergency department complaining of chest pain. She was diagnosed with acute-on-chronic systolic heart failure and non-ST-elevated myocardial infarction (MI). She had a previous MI with bare metal stent placement and was taking aspirin and prasugrel 10 mg daily. Once admitted, a P2Y12 assay revealed HTPR (331 PRU); therefore, prasugrel was reloaded (60 mg). The next day a P2Y12 assay showed adequate platelet reactivity inhibition (118 PRU), so prasugrel 10 mg daily was continued in the hospital and on discharge. Seventeen days after discharge she was readmitted for possible ischemia. On day 3 of admission, a P2Y12 assay revealed HTPR (278 PRU); subsequently, prasugrel was discontinued and ticagrelor started. After 3 doses of ticagrelor, a P2Y12 assay was 97 PRU, so ticagrelor was continued. Five months have passed since discharge. The patient continues to take ticagrelor and has had no further cardiac events. Discussion: HTPR indicates hypo- or nonresponsiveness for antiplatelet agents and may result in serious adverse events. HTPR has rarely been reported with prasugrel or ticagrelor. An objective causality assessment of our case revealed a probable association between HTPR and prasugrel. Conclusion: Patient education and recognition of signs and symptoms associated with prasugrel HTPR may prevent morbidity and mortality from treatment failure. Additional research may determine incidence, risk factors, and optimal management of HTPR with prasugrel.

Tailored antiplatelet therapy to improve prognosis in patients exhibiting clopidogrel low-response prior to percutaneous coronary intervention for stable angina or non-ST elevation acute coronary syndrome

AIM

To investigate whether an intensified antiplatelet regimen could improve prognosis in stable or non-ST elevation in acute coronary syndrome (ACS) patients exhibiting high on-treatment platelet reactivity (HTPR) on clopidogrel and treated with percutaneous coronary intervention (PCI). There is a wide variability in the platelet reactivity to clopidogrel and HTPR has been associated with a poor prognosis.

METHODS

In this observational study, 923 consecutive patients without ST-elevation myocardial infarction (STEMI) and adequately pre-treated with clopidogrel were screened for HTPR with multiple electrode aggregometry after assessment of the coronary anatomy. Patients were grouped based on their response to clopidogrel and the assigned antiplatelet strategy. The primary endpoint was a composite of cardiovascular death, myocardial infarction, stroke, or stent thrombosis.

RESULTS

HTPR was demonstrated in 237 patients (25.7%). Of these, 114 continued on conventional clopidogrel therapy, while the remaining 123 received intensified antiplatelet therapy with either double-dose clopidogrel (150 mg daily, n = 55) or the newer P2Y12-inhibitors, prasugrel or ticagrelor (n = 68) for at least 30 days after the index procedure. The median follow-up was 571 days (interquartile range, 373-746). Intensifying antiplatelet therapy reduced the rate of the composite endpoint (p < 0.001). After adjustment for potential confounders, HTPR in combination with conventional clopidogrel therapy remained independently associated with an increased risk of cardiovascular events (hazard ratio (HR), 2.92; 95% CI, 1.90-4.48), whereas intensified treatment reduced the risk to a level equivalent to that of patients exhibiting normal platelet reactivity (HR, 1.08; 95% CI, 0.59-1.99).

CONCLUSION

Tailored antiplatelet therapy significantly reduced the event rate in patients exhibiting HTPR prior to PCI.

Clopidogrel resistance in diabetic patient with acute myocardial infarction due to stent thrombosis

Stent thrombosis is a morbid complication after percutaneous coronary intervention. Dual antiplatelet therapy significantly reduces stent thrombosis risk and forms currently the basis in acute ST elevation myocardial infarction pharmacologic treatment. The introduction of clopidogrel has made a major advance in the acute coronary syndrome treatment. However, there is growing evidence about failure in antiplatelet response after clopidogrel, which may lead to subsequent risk of future thrombotic events. The antiplatelet inhibitory effect of clopidogrel varies widely among individuals. High on-treatment platelet reactivity has been repeatedly associated with a hazard for cardiovascular events, including stent thrombosis. Laboratory monitoring of antiplatelet therapy efficacy may help identify patients with insufficient antiplatelet response. Prasugrel therapy was repeatedly described as an effective method to overcome clopidogrel resistance. We report a case of diabetic patient in whom myocardial reinfarction due to stent thrombosis developed. Clopidogrel resistance was detected in this patient using light transmission aggregometry and vasodilator-stimulated phosphoprotein phosphorylation assessment. After prasugrel administration, no other ischemic event occurred, and patient was released to outpatient care in good general condition.