Atrial fibrillation is the most common arrhythmia and is associated with increased morbidity and mortality, including thromboembolic events (1). The prevalence of atrial fibrillation (AF) is increasing globally and has been projected to increase to 5.6 million individuals in the USA by the year 2050 and 8.8 million adults over 55 years in Europe by the year 2060, indicating substantial public health and economic burden (2). AF is associated with an increased risk of acute myocardial infarction (AMI) and the presence of AF during AMI has been associated with a worse prognosis (3, 4).

In AF patients, oral anticoagulant (OAC) is required to reduce the risk of thromboembolic events, whereas antiplatelet therapy is essential to prevent thrombotic events, including stent thrombosis, in patients with ischemic heart disease undergoing percutaneous coronary intervention (PCI). However, there are concerns regarding the major bleeding due to the intensive combination antithrombotic therapy (5, 6). Thus, current guidelines recommend that early cessation of aspirin and continuation of dual antithrombotic therapy with an OAC plus clopidogrel up to 6–12 months in patients with AF at increased risk of stroke (CHA₂DS₂-VASc score ≥ 2) who have undergone PCI with stent implantation for ischemic heart disease (7, 8).

However, despite the recommendations of the current guidelines, a previous nationwide population-based study reported that only 22.7% of patients received triple therapy, i.e., the combination of dual antiplatelet therapy (DAPT) plus OAC, after PCI although 96.2% of them were indicated for anticoagulation (9). Until now, there is a paucity of data regarding the status of anticoagulant usage in AF patients who underwent PCI with stent implantation for AMI. Therefore, this study aimed to identify the trends in OAC usage patterns and the variables associated with the use of OAC from the real world in patients with AF presenting AMI who underwent PCI with stent implantation.

Among the entire 13,104 patients from the KAMIR-NIH registry, the prevalence of AF was 5.4% (712/13, 104) and the trend of annual AF incidence in patients with AMI was stable (p-value for trend = 0.21) (Figure 1). Of these patients, 17% (121/712) patients have been newly diagnosed AF after AMI. A total of 453 eligible patients with AF and AMI treated with stent implantation were analyzed. The mean age was 68.5 ± 12 years (range: 37–92 years), and 337 (74.4%) of the patients were men. The mean CHA₂DS₂-VASc Score was 3.7 ± 1.7.

Among 453 patients who underwent PCI with stent implantation successfully and were discharged, only 15.7% of patients were treated with OAC although 89.6% of them were indicated for anticoagulation (CHA₂DS₂-VASc score ≥ 2). The study population was classified into two groups according to the OAC usage after stent implantation as follows: patients who used OAC according to the clinical guidelines (n = 71, 15.7%) and did not use OAC (n = 382, 84.3%) (Supplementary Figure 1). Baseline characteristics of the study population are presented in Table 1. Compared with patients treated without OAC, those using OAC were higher rates of female, diabetes mellitus, current smoker, a history of cerebrovascular accident, and moderate to severe left ventricular systolic dysfunction. Aspirin and clopidogrel were used more frequently in OAC groups, while ticagrelor was used more often in the non-OAC group than in the OAC group. Other baseline characteristics were comparable between the two groups.

Angiographic and procedural characteristics are listed in Supplementary Table 1. Among these, disease extent, the total number of implanted stents, mean stent diameter, and total stent length did not significantly differ between the two groups, except for the distribution of infarct-related arteries.

Regarding the trends of antithrombotic therapy in both groups, among the 71 patients in the OAC group, triple therapy was used in 67 (94.4%) patients. The majority of patients with triple therapy received clopidogrel (61/67). Only four patients in the OAC group were treated with dual therapy. In patients treated without OAC, 378 (99%) patients received DAPT and four (1%) patients treated with single antiplatelet treatment (SAPT) (Table 2). Detailed information on the antithrombotic treatment at discharge and after 12 months is summarized in Table 3 and Figure 2.

The scores in CHA₂DS₂-VASc of the study population are described in Table 4. Mean CHA₂DS₂-VASc score was significantly higher in the OAC group than in the non-OAC group (4.7 ± 1.6 vs. 3.6 ± 1.7, p < 0.01), and the proportion of patients with a score of 2 or more were much higher in the OAC than in the non-OAC group [97.2% (69/71) vs. 88.2% (337/382), p = 0.02] (Supplementary Figure 2). The detailed distributions of the CHA₂DS₂-VASc scores are shown in Figure 3. Among the 453 study patients, 406 had a high risk of stroke (CHA₂DS₂-VASc Score ≥ 2). However, OAC was used only in 17% (69/406). In the low to intermediate stroke risk group (CHA₂DS₂-VASc Score <2), 4.3% (2/47) of patients were treated with OAC. Among the components of the CHA₂DS₂-VASc score, the OAC group had a higher prevalence of CHF, diabetes mellitus, prior stroke, TIA or thromboembolism history, age 65–74 years, and female gender (Table 4).

In the multivariate analyses for the determinants of the use of OAC, female gender, diabetes mellitus, and prior CVA history were significant determining factors. History of CHF or the presence of moderate to severe left ventricle (LV) systolic impairment (LVEF ≤ 40%) was also a significant determinant (Table 5).

During a 1-year follow-up, there were 44 major adverse cardiovascular and cerebrovascular events (MACCE) (28 all-cause deaths, five MIs, and six cerebral infarctions or TIAs) after stent implantation, and no significant difference was noted between the OAC and non-OAC groups in both the crude- and IPTW-analyses (Supplementary Table 2). The rates of MACCE, composite all-cause death and MI, composite cardiac death, and MI were also not significantly different between the two groups in both the crude- and IPTW-analyses.

The principal findings of the current study were as follows: (1) in real-world practice, the prevalence of AF in AMI patients was 5.4%; (2) only 15.7% of total AMI patients were treated with OAC although 89.6% of them were indicated for anticoagulation (CHA₂DS₂-VASc score ≥ 2); (3) the significant determinants for the use of OAC were female gender, diabetes mellitus, prior CVA history, and a history of CHF or the presence of moderate to severe LV systolic impairment.

The prevalence of AF in the entire Korean population was reported to be 67% in a previous study using the National Health Insurance Service database from 2008 to 2015 and the incidence and prevalence of AF increased in the Korean population over time (13). However, the prevalence of AF in Korean AMI patients has not been reported to date. Previous studies with the western population reported that AF occurred in 7.2–13.2% of patients with AMI (14, 15). In the China registry, the prevalence of AF was reported to be 3% in AMI patients (16). In the current nationwide study, the prevalence of AF in AMI patients was 5.4% and the trend of annual AF incidence in patients with AMI was stable. A previous study showed that the prevalence of AF was significantly higher in Caucasian (8%) than in black (3.8%), Hispanic (3.6%), and Asian (3.9%) ethnic groups (17). Therefore, our study results supported that the prevalence of AF in Asian patients with AMI was relatively lower when compared with Caucasians although more data should be collected (16).

Although the presence of AF during AMI has been associated with a worse prognosis (4), OAC was underused, in only ~15% of the AMI patients with AF undergoing PCI with a stent in the current study. Previous US registry reported only 27% (n = 448) of the total population received triple therapy at discharge among the 1,648 patients with AF with non-ST-elevation myocardial infarction who underwent PCI (18). The Swedish registry also reported the only 30% (1,848/6,182) of total AMI patients with AF admitted from 1995 to 2002 were prescribed OAC (19). The tendency of underused OAC in the current and previous studies could be explained by the concern regarding bleeding complications when patients were treated with triple therapy. Previous nationwide cohort study with AF patients following AMI and PCI showed that triple therapy increased both early and delayed bleeding risk compared with DAPT (20). Therefore, the concern for major bleeding may have affected the decision of physicians to not use OAC. However, since the introduction of non-vitamin K oral anticoagulants (NOACs), recent studies consistently showed a significant reduction in major bleeding with NOAC-based treatment compared with the vitamin K antagonist-based therapies, resulting in a rapid increase in triple therapy with NOAC after PCI for AMI in AF patients (21). As a result, the current guidelines recommend the preferable use of NOAC over vitamin K antagonists (21). In the era of NOAC, further study regarding recent trends of antithrombotic therapy in patients with AF and AMI is needed.

Cardiac catheterization with radial access has been reported to be more beneficial than femoral access with fewer occurrences of hemorrhagic events and short-term cardiac death (22). In the current study, only 27.6% (125/453) of total patients underwent PCI via transradial access. The proportion of transfemoral access is somewhat high, which may have affected the operator to be reluctant to prescribe OAC.

There are concerns regarding the major bleeding due to the intensive combination antithrombotic therapy. Thus, current guidelines recommend that early cessation of aspirin and continuation of dual antithrombotic therapy with an OAC plus clopidogrel up to 6–12 months in patients with AF at increased risk of stroke (CHA₂DS₂-VASc score ≥ 2) who have undergone PCI with stent implantation for ischemic heart disease (7, 8). Although this study was a study of patients from November 2011 to December 2015, the ESC guideline for STEMI published in 2012 also strongly recommended triple therapy with minimal duration to reduce bleeding risk in patients with obligatory indication for OAC after stent placement (Class 1, Level C) (23). However, unlike the recommendation of the guidelines, 14.8% (67/453) of AF patients who underwent PCI for AMI were treated with triple therapy at discharge, of which the majority of patients (58.2%) maintained triple therapy for 1 year. Therefore, further research and discussion on this area are needed.

A previous nationwide population-based study reported that the prior CVA history and congestive heart failure were significantly associated with a higher triple prescription rate in patients with AF undergoing PCI (9). In the current study, we also found that the prior CVA history and a history of CHF or the presence of moderate to severe LV systolic impairment were significant determinants for physicians to the use of OAC. Additionally, female gender and diabetes mellitus were significant factors affecting OAC usage. Among the components of the CHA₂DS₂-VASc score, our study results showed that older age and hypertension did not affect the use of OAC. This might be explained by the fact that previous studies, including the current study, were for patients with ischemic heart disease and AF, rather than overall AF patients, indicating different characteristics of OAC usage.

This study had several limitations. First, this study was a non-randomized, observational study, which has inherent selection and information biases. Second, the current study was conducted on patients registered in the registry, thus the results were difficult to apply with representation and in hypothesis generation. Third, details of the prescription of the OAC such as treatment duration of OAC and type of OAC (vitamin K antagonist or NOAC) were not considered. However, we identified the trend of change in antithrombotic therapy between the hospital discharge and 12 months after PCI. Fourth, currently available data did include only in-hospital bleeding events. Fifth, the comparison of 12-month clinical outcome was done by classifying the patients based on OAC usage at the time of hospital discharge without considering the treatment duration or type of OAC, or concomitant antiplatelet agents, so the results should be interpreted with caution. Nevertheless, this study expects physicians to be able to understand the trends in the use of OAC usage in patients with AMI and AF.

The nationwide prospective dedicated AMI registry demonstrated that the prevalence of AF was 5.4% in patients with AMI. Moreover, contrary to the guidelines, OAC was underused, in only ~15% of the AMI patients with AF undergoing PCI with a stent in real-world practice. The significant determinants for the use of OAC were female gender, diabetes mellitus, prior CVA history, and a history of CHF or the presence of moderate to severe LV dysfunction, although the older age and hypertension did not affect the use of OAC among the components of the CHA₂DS₂-VASc score.

The data supporting the conclusions of this article are available from the corresponding author upon reasonable request.

The studies involving human participants were reviewed and approved by Institutinal Review Board of each participating center. The approval number was CNUH-2011-172 at Chonnam National University Hospital. The patients/participants provided their written informed consent to participate in this study.

O-HL and YK study concept and design, acquisition, analysis, and interpretation of data, drafting for the manuscript, and critical revision of the manuscript for important intellectual content. YK, D-KC, J-SK, B-KK, DC, M-KH, MJ, and YJ acquired the data. D-KC, DC, M-KH, and YJ supervised the progress of the study. All authors listed have made a substantial, direct and intellectual contribution to the work, and approved it for publication.

This work was supported by a faculty research grant from Yonsei University College of Medicine (6-2020-0161) and a research seed money grant of Internal Medicine in Yongin Severance Hospital.

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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