Atrial fibrillation in acute coronary syndrome: patient characteristics and appropriate utilisation of anti-thrombotic therapy in New Zealand (ANZACS-QI 39).

Background: Concomitant atrial fibrillation (AF) and acute coronary syndrome (ACS) present the difficult therapeutic dilemma of balancing bleeding, cardio-embolic and coronary thrombotic risks with appropriate combinations of antithrombotic medications. We aim to evaluate current New Zealand practice by identifying the incidence of AF in ACS; describe the population characteristics; and assess our antithrombotic management.

Methods: Consecutive patients ≥18y presenting with ACS who had coronary angiography (2017-2018) were identified from the All New Zealand ACS Quality Improvement (ANZACS-QI) registry. The cohort was divided into three groups: 1) patients with pre-existing AF; 2) new-onset AF; and 3) no AF. Antithrombotic regimens included dual antiplatelet therapy (DAPT), dual antithrombotic therapy (DAT-single antiplatelet plus an oral anticoagulant (OAC)) and triple antithrombotic therapy (TAT).

Results: There were 9,489 patients, 9.6% with pre-existing AF, 4.4% new AF and 86% without AF. Both AF groups were older (median 74 vs 71 vs 65y, p=0.001), had poorer renal function, were more likely to present with heart failure (16% vs 19% vs 8%, p=0.001) and have left ventricular ejection fraction <40% (22% vs 28% vs 13%, p<0.001). They received less percutaneous coronary intervention (PCI) (53% vs 59% vs 70%, p=0.001). In the cohort, 25 different combinations of antithrombotic agents were utilised. Ninety-six percent of patients with any AF had a CHA2DS2VASC stroke risk score of ≥2, of whom 48% did not receive OAC. Twenty-four percent received TAT and 19% DAT. OAC use increased slightly with increasing stroke risk but were independent of CRUSADE bleeding risk. Of patients with AF treated with PCI, 53% received DAPT, 11% DAT and 35% TAT. 51% of those at high stroke risk were discharged on DAPT only. In contrast, 19% at low stroke risk received TAT.

Conclusion: In New Zealand, one in seven patients presenting with ACS have AF, a third being new-onset AF. Antithrombotic management is inconsistent, with underutilisation of anticoagulants, particularly the DAT regimen, and is inadequately informed by stroke and bleeding risk scores.