60 Antithrombotic therapy following surgical revascularisation in non ST-elevation myocardial infarction (NSTEMI)- what is the optimal regime?

Background Current European Society of Cardiology (ESC) guidelines advocate the use of dual antiplatelet therapy (DAPT) following surgical revascularisation of patients presenting with NSTEMI (1). We sought to ascertain adherence to current guidelines and compare outcomes with the use of different antithrombotic regimes in our institution. Methods 388 patients underwent urgent coronary artery bypass grafting (CABG) in our institution between 2016 and 2018. The national electronic healthcare record was used to retrospectively collect data. Patients meeting the ESC universal definition of myocardial infarction at presentation were included. The primary safety outcome was defined as any Bleeding Academic Research Consortium Bleeding (BARC) Type 2–5 event on therapy at 1 year. The primary efficacy outcome was defined as a composite of non-fatal MI, CV death, unplanned revascularisation and documented graft failure at 1 year. The net clinical composite end point was a combination of both ischaemic and bleeding end points at 1 year. Results 181 patients met our inclusion criteria (table 1). Mean age=67.8 ±9.4. Male sex=80.6%. Mean follow-up duration=710 ±177 days. 60.2% were managed with SAPT (aspirin 300 mg OD), 27.1% with DAPT (90% aspirin 75 mg OD plus clopidogrel 75 mg OD) and 12.7% with oral anticoagulation (OAC) plus SAPT. OAC regimes were warfarin plus aspirin (60.9%), NOAC plus aspirin (34.8%) and NOAC plus clopidogrel (4.3%). The primary safety end point was observed in 6.1% in the DAPT group, 9.2% in the SAPT group (HR 0.74; 95% CI 0.20–2.72; p 0.65) and 21.7% in the OAC plus SAPT group (table 2, figure 1). The primary efficacy end point occurred in 0.0% in the DAPT group, 1.8% in the SAPT group (p 1.0) and 4.3% in the OAC plus SAPT group. The net clinical efficacy/safety end point occurred in 6.1% in the DAPT group, 9.2% in the SAPT group (HR 0.66; 95% CI 0.18–2.40; p 0.53) and 26.1% in the OAC plus SAPT group (figure 2). Ischaemic stroke occurred in 4.1% in the DAPT group vs 1.8% in the SAPT group (p 0.59). Conclusions There was no statistically significant difference in either bleeding or ischaemic events between DAPT and SAPT. There was a trend towards reduction in both ischaemic and bleeding events with DAPT vs high dose SAPT. Our population size was underpowered to detect ischaemic events, however our findings would support the safety of current guidelines and advocate the use of DAPT following surgical revascularisation in NSTEMI. A significantly higher rate of bleeding was observed in the OAC plus SAPT group. This population are not readily comparable to the other regimes in view of the underlying need for OAC for stroke prophylaxis. This does however raise the question about the potential safety of OAC monotherapy post CABG in patients with non-valvular AF as a method of bleeding risk reduction.