Changes of antithrombotic prescription in atrial fibrillation patients with acute coronary syndrome or percutaneous coronary intervention and the subsequent impact on long-term outcomes: a longitudinal cohort study

The optimal strategy for antithrombotic therapy in patients with atrial fibrillation (AF) and concomitant acute coronary syndrome (ACS) or percutaneous coronary intervention (PCI) is controversial. Dual antiplatelet therapy (DAPT) with a P2Y12 inhibitor plus aspirin is recommended in patients with ACS or those undergoing PCI. However, oral anticoagulation (OAC) is superior to DAPT for prevention of stroke and systemic thromboembolism in patients with AF. Current guidelines recommend a triple antithrombotic therapy (TAT) strategy involving DAPT plus an OAC after ACS or successful PCI in AF patients. However, this carries an increased risk of bleeding. In 2016, the PIONEER-AF study found that dual antithrombotic therapy (DAT) involving  a P2Y12 inhibitor plus the non-vitamin-K dependent oral anticoagulation (NOAC) rivaroxaban once daily was associated with a lower rate of significant bleeding than TAT with DAPT plus a vitamin-K antagonist (VKA). However, there is a lack of data evaluating the real-world use of these strategies.

The aim of this study was to evaluate investigate the prescribing patterns of antithrombotic regimen in different cohorts and their clinical impact.

This study provided real-world data on antithrombotic management in AF patients with ACS or PCI in two longitudinal cohorts in Taiwan. It showed that, since the publication of the PIONEER-AF study in December 2016, DAPT alone remains the most common antithrombotic regimen, and is used in more than half of all patients. The prescription rate of TAT has increased, particularly DAPT plus a NOAC, while the prescription rates of DAT and DAPT have decreased. This under-prescribing of OAC highlights a gap between guideline recommendation and real-world practice. However, changes of antithrombotic prescription were not associated with adverse safety and efficacy outcomes.

Despite the availability of NOACs, the prescription of DAPT remains high. There is a need to increase physician awareness of the optimal antithrombotic management of AF patients with ACS or PCI, and increase adherence to guidelines.

This was an observational study that evaluated longitudinal data from the Tri-Service General Hospital-Coronary Heart Disease (TSGH-CHD) registry in Taiwan between January 2016 and August 2018. A total of 121 patients with prior history of nonvalvular AF, who presented with ACS or underwent PCI were allocated to cohort 1 (n=35) if the prescribing date was before the publication of PIONEER AF-PCI study (December 31, 2016) and cohort 2 (n=86) after this date. Stroke risk was assessed using CHA2DS2-VASc scores. The antithrombotic regimens were prescribed according to physician discretion and were categorised as TAT, DAPT, and DAT. The TAT regimens included DAPT plus VKA, DAPT plus full-dose NOAC, and DAPT plus low-dose NOAC. DAT included single antiplatelet therapy (SAPT) plus VKA, SAPT plus full-dose NOAC and SAPT plus low-dose NOAC.

• Composite of major bleeding and/or clinically relevant non-major bleeding

• Composite of all-cause mortality, stroke/systemic embolisation, non-fatal myocardial infarction (MI), and coronary revascularisation (>30 days after discharge)

• Presented with stable angina (SA) or acute coronary syndrome (ACS), including unstable angina (UA), non-ST-segment elevation myocardial infarction (NSTEMI), or ST-segment elevation myocardial infarction (STEMI).

• Hospitalised without clinical suspicion of CAD (i.e. the purpose of the angiographic examination was pre-operative evaluation for major cardiac surgery or post-heart transplant coronary investigation)

• The prescription rate of triple antithrombotic therapy (TAT) increased from 17.1% in cohort 1 to 38.4% in cohort 2. Among these, the use of DAPT plus low-dose NOAC was more common than DAPT plus warfarin and DAPT plus full-dose NOAC in both cohorts
• The prescription rate of dual antithrombotic therapy (DAT) decreased  from 14.3% to 10.5%. Among these, SAPT plus a VKA was the most commonly prescribed (11.4%) in cohort 1, and SAPT plus a NOAC was more common (8.2%) in cohort 2
• The prescription rate of DAPT decreased from 68.6% to 51.2%
• The prescription of DAT was more common in patients with prior history of stroke or transient ischaemic attack.
• During follow-up, the primary safety endpoint occurred in 31.4% of patients in cohort 1 and 25.6% patients in cohort 2. There was no significant difference between the two cohorts (hazard ratio [HR], 0.87; 95% confidence interval [CI], 0.42–1.80; p=0.710)
• The secondary efficacy endpoint occurred in 20.0% of cohort 1 and 19.8% of cohort 2 (HR, 0.96; 95% CI, 0.40–2.32; p=0.930)

Currently, most guidelines recommended the TAT strategy for the majority of AF patients with ACS and/or underwent PCI, especially those with high ischaemic risk and low bleeding risk. These data show that, since the beginning of the NOAC era, the percentage of DAPT prescription has decreased but it remains the most common antithrombotic regimen compared with TAT and DAT. Although the prescription of antithrombotic regimen has changed over the study period, the safety and efficacy outcomes were similar during follow up. This gap between guideline recommendation and real-world practice has been reported in other Asian studies.

• This is a single-centre, observational cohort study from Taiwan and may not reflect other regions
• The sample size was small, potentially affecting statistical significance
• Not all dosages of NOAC were available in the centre, which may have affected the decision of which antithrombotic strategy to use
• There was a low prescription rate of guideline-recommended therapy, including RAS blockade, beta-blockade, and statins, which might affect clinical outcomes