IJCS | Volume 33, Nº1, January / February 2019

76 Geraldes et al. Oral anticoagulation in AF Int J Cardiovasc Sci. 2020;33(1):68-78 Original Article score, 20–50% of high-risk patients remain unprotected without anticoagulants. Several reasons may have contributed to these findings. Many physicians may not use any tools as structured as CHA 2 DS 2 -VASc for evaluation of thromboembolic risk in AF, using only their imprecise clinical impression 12 and failing to capture the actual risk of some patients. Besides, patients with higher CHA 2 DS 2 -VASc have a higher prevalence of comorbidities associated with both higher risk of stroke and bleeding risk. Exploring this assumption, we demonstrated a strong correlation between the CHA 2 DS 2 - VASc and HASBLED scores (Spearman’s r 0.706). Physicians may be fearful of prescribing anticoagulants for patients with higher CHA 2 DS 2 -VASc if they also present higher risk of bleeding, translated by higher HASBLED. Additionally, sincemany of these patients are also older and have higher prevalence of atherosclerotic disease, a significant percentage already use antiplatelet agents, which adds to the risk of bleeding and reluctance to prescribe anticoagulants. Predictors of use of anticoagulants and DOACs In our study, history of AF episodes and the presence of SAH individually increased by three- fold the chances of patients receiving anticoagulant prescription at discharge. On the other hand, at every 1 point where HASBLED increased, the chance of anticoagulation was reduced by 50%. These are logical and intuitive predictors of anticoagulation, since the first two increase the perception of thromboembolic risk and the last one increases the risk of bleeding. In the NCDR PINNACLE registry, there were more hypertensives among patients taking anticoagulants than among those who did not use anticoagulants (80% versus 74%; p < 0.001). 21 In an analysis of participants from the 2nd and 5th cohorts of the GARFIELD-AF study in the UK, the two main reasons for the physician to avoid using anticoagulant in patients with CHA 2 DS 2 -VASc ≥ 2 were risk of fall and hemorrhagic event, respectively. 22 Regarding the predictors of use of DOACs, we observed that for each 1.0 mg/dl increase in serum creatinine, there was 82% less chance of the patient being discharged on DOAC. For 1 year, Luger et al. analyzed AF patients who had stroke or TIA and concluded that the decision on the use of VKA or DOAC was mainly determined by the patient’s renal function and absence of previous anticoagulant therapy, both reducing the chance of using DOAC. 23 In addition to renal function, the presence of a biological valve prosthesis also significantly reduced the chance of DOAC prescription. Although not all studies comparing DOACs with VKA excluded patients with biological prostheses, which do not represent contraindication for the use of DOACs, the unfavorable experience of dabigatran in patients with mechanical prostheses 24 may cause some fear of using these anticoagulants in the context of any valve prosthesis. Appropriateness of DOAC prescription Our study demonstrated that in 28% of DOAC prescriptions, the doses were inadequate for the patients’ clinical profile. However, as opposed to the findings of the cited studies, the most frequent dosing error was improper reduction of DOAC dose, rather than lack of adjustment. Both the lack of adjustment and improper dose reduction may compromise the efficacy and safety of anticoagulant therapy with DOACs. The randomized cluster study IMPACT-AF showed that multifaceted educational interventions were able to improve the frequency of anticoagulation and reduce the incidence of stroke. 25 Limitations Limitations of this paper include its retrospective design based on electronic medical records, making it subject to registration bias due to lack of information in medical records. In some cases, for example, it was not possible to assess the suitability of the DOAC dose because we did not have serum creatinine, weight or height information. Some patients were excluded because they did not have electronic prescription for discharge. However, these events were infrequent and did not compromise the results found. Regarding the possibility of generalizing our findings to other populations, although it was conducted in a single center, the characteristics of the study population are similar to those of major international registries ofAF. However, because it was conducted in a private medical center, our data cannot be extrapolated to patients with AF from the public healthcare system. Conclusions This study demonstrated that, following the approval of DOACs for clinical use in Brazil in 2011, these anticoagulants were rapidly incorporated into clinical