Management of antiplatelet therapy resistance in cardiac surgery

Development of a concept for a personalized approach in the perioperative antiplatelet therapy administration/discontinuation management based on multiple electrode aggregometry in patients undergoing coronary artery surgery

In patients undergoing coronary artery surgery, improvements in clinical outcomes currently rely on continued refinements of the surgical technique and modulation of adjuvant pharmacotherapy. Despite medical and technological advances, negligible rate of bleeding and ischemic events still persist necessitating further improvements in patient management. Platelet function testing (PFT) might play an important role in meticulous balancing between the risk of bleeding and thrombotic events. A suitable balance can be achieved by implementing a personalized, PFT based approach in antiplatelet therapy (APT) administration/discontinuation management. Despite emerging evidence on the widespread variability in platelet inhibitory response to APT, numerous PFT devices and heterogeneity in reporting study results hamper pooling of the evidence which in turn results with a lack of consensus in "on treatment" platelet reactivity associated with ischemic and bleeding events in perioperative phase. The literature on multiple electrode aggregometry (Multiplate(®); Roche Diagnostics, Mannheim, Germany) in coronary artery disease patients was reviewed systematically. Based on the evidence evaluating the relationship between "drug specific" PFT and bleeding or adverse ischemic events, we sought to define therapeutic window for the most commonly administered antiplatelet drugs such as aspirin (ASPI test) and adenosine-diphosphate receptor blockers (ADP test). Preoperatively, APT administration was primarily focused to avoid bleeding complications. ASPI test value of 20 AUC and ADP test value of <73 AUC were set as cut-off values that delineate bleeding tendency. Postoperatively, "therapeutic window" was set to avoid both bleeding and adverse ischemic events. Therapeutic ranges were as follows: 20 AUC < ASPItest ≤ 30 AUC and 19AUC < ADP ≤ 46AUC, respectively. This is the first attempt to define PFT based "therapeutic window" according to, perioperative APT administration/discontinuation management would be targeted. It seems that the "one-size-fits-all" concept of perioperative APT administration management is outdated and further development of PFT based, personalized APT administration/discontinuation management is desirable. This concept therefore presents a possible step forward in patient care and provides a platform for further interventional trials whereby the impact of its application on clinical outcomes would be validated.

Reduced aspirin responsiveness as assessed by impedance aggregometry is not associated with adverse outcome after cardiac surgery in a small low-risk cohort

Reduced aspirin responsiveness (i.e. persistent high platelet reactivity in platelet function testing) might be associated with increased risk of myocardial ischemia and cardiac mortality in patients with coronary disease. However, the impact in patients undergoing coronary artery bypass grafting (CABG) is unclear. The aim of this prospective cohort study was to evaluate the predictive value of reduced aspirin responsiveness on cardiac and thromboembolic events in patients undergoing elective isolated CABG surgery with aspirin intake until at least two days before surgery. We included 304 patients in this prospective single-center cohort study. Impedance platelet aggregometry (Multiplate®) was performed directly before and on the first day after surgery. Reduced aspirin responsiveness was defined as area under the curve in ASPItest (AUCASPI) ≥300 U. The primary outcome was a composite of all-cause mortality and/or major adverse cardiac or thromboembolic events within 1 year. Reduced aspirin responsiveness was found in 13 and 24% of patients pre and postoperatively, respectively. There was no difference in the outcomes between patients with normal and reduced aspirin responsiveness in the preoperative measurement (log-rank test, p = 0.540). Multivariate analysis including logistic EuroSCORE I and postoperative troponin T levels did not show any association of reduced aspirin responsiveness with adverse outcome (hazard ratio, 0.576; (95% CI 0.128-2.585; p = 0.471). Similarly, postoperative reduced aspirin responsiveness was not associated with adverse events. To conclude, reduced aspirin responsiveness as evaluated by Multiplate® platelet function analyzer was not associated with increased incidence of major adverse cardiac and thromboembolic events and mortality after CABG surgery.

Reduced Effect of Aspirin and Clopidogrel Following Hybrid Coronary Revascularization

OBJECTIVE

Reduced effect of antiplatelet therapy following coronary artery bypass grafting is associated with reduced graft patency. We sought to evaluate the impact of hybrid coronary revascularization on the effect of aspirin and clopidogrel and whether high baseline platelet aggregation, high postoperative levels of platelet turnover, and acute-phase response may contribute to the effect.

METHODS

We prospectively studied platelet aggregation (VerifyNow and Multiplate Analyzer), platelet turnover (immature platelets, mean platelet volume, and thrombopoietin), and acute-phase reactants (C-reactive protein, von Willebrand factor, and coagulation factor VIII) in 40 patients undergoing elective hybrid coronary revascularization (off-pump surgical revascularization through J-hemisternotomy followed by percutaneous coronary intervention [PCI]). Preoperative blood samples on- and off-aspirin were compared with blood samples obtained postoperatively, following PCI when dual antiplatelet therapy had been initiated and at 1-year follow-up.

RESULTS

The antiplatelet effect of aspirin was significantly reduced in the early postoperative period as measured by VerifyNow Aspirin but not by Multiplate ASPI test. The antiplatelet effect of clopidogrel was significantly reduced following PCI as measured by VerifyNow P2Y12 and Multiplate ADP test. The level of baseline aggregation did not predict the antiplatelet effect of aspirin or clopidogrel, and no association was found between platelet aggregation and postoperative platelet turnover or acute-phase reaction.

CONCLUSIONS

A transient reduction in the antiplatelet effect of aspirin and clopidogrel was observed after hybrid coronary revascularization despite limited surgical trauma and off-pump technique. Neither baseline platelet aggregation nor postoperatively increased platelet turnover and acute-phase response could explain this finding. ClinicalTrials.gov identifier, NCT02293928.