Prevalence of Valvular and Non-valvular Atrial Fibrillation and the Application of Antithrombotic Treatment in a Tertiary Care Hospital

ABSTRACT Introduction: Atrial fibrillation is a common atrial tachyarrhythmia with an increased risk of throm-boembolism. This study aims to provide information about the application of antithrombotic treatment based on risk stratification schemes for stroke in real-life clinical practices. Methods: This was a descriptive cross-sectional study in 260 patients admitted at the tertiary care hospital with a diagnosis of atrial fibrillation from January 2019 to February 2020 after approval from the Institutional Review Committee (ref. no. 207/2018). Convenient sampling was used. Predisposing conditions for atrial fibrillation, risk factors for stroke, and the use of antithrombotics were obtained based on the pre-structured questionnaires. Data were analyzed by Statistical Package for the Social Sciences version 20. Results: The prevalence of valvular and non-valvular atrial fibrillation was 125 (48.0%), and 135 (51.9%) respectively. Among patients with a non-valvular variant, 102 (75.5%) had a CHA2DS2VASc-score of ≥2 who were eligible for oral anticoagulants, 13 (9.6%) patients received it with a majority having sub-therapeutic international normalized ratio. Among patients with valvular type, only 47 (37.6%) patients were receiving oral anticoagulants and 20 (42.5%) patients achieved therapeutic international normalized ratio. Two hundred forty three (93.4%) patients had dilated left atrium (≥40mm), 119 (45.9%) had hypertension and 27 (10.3%) had diabetes mellitus. Conclusions: Antithrombotics were markedly underused in patients with atrial fibrillation. There is a need for proper application of risk stratification schemes for stroke and appropriate use of anti-thrombotics to prevent thromboembolism.


INTRODUCTION
Atrial fibrillation (AF) is the most common sustained tachyarrhythmia which affects 1-2% of the general population. 1 AF is a risk factor for stroke and thromboembolism. There is higher mortality and morbidity when a stroke occurs in association with AF. Therefore, stroke prevention is a major concern when managing patients with AF. Various clinical risk factors have been identified, which confer a high risk of stroke.
An important aspect of AF management is the prevention of stroke, using antithrombotic agents including anti-platelets and oral anticoagulants (OACs). 2 Although the literature provides simplified rules for the use of antithrombotic in patients with AF, studies have shown that OAC is frequently underused in AF patients with reported use in between 30 and 60%. 1,3,4 This suboptimal use may be related to various physician and patient factors. This study provides information about the application of antithrombotic treatment for patients with valvular atrial fibrillation (VAF) and non-valvular atrial fibrillation (NAVF) in a tertiary care hospital.

METHODS
This descriptive cross-sectional study was conducted from January 2019 to February 2020. A total of 260 patients with AF (age ≥15 years) who attended the cardiology clinic or admitted to the cardiology unit of Nobel Medical College Teaching Hospital were enrolled based on a convenient sampling method. Ethical approval was obtained from the institutional review committee (NMCTH ref Taking a 10% non-respondent rate, the sample size becomes 204. However, the total sample size was 260. All participants were asked relevant questions to note demographic information, co-morbid conditions, use of antithrombotic agents, and risk factors for stroke based on pre-structured questionnaires. The international normalized ratio (INR) value of patients who were on vitamin K antagonists (VKA) was noted at the time of enrollment. CHA 2 DS 2 -VASc (Congestive heart failure, Hypertension, Age ≥75 years, Diabetes mellitus, prior stroke or transient ischemic attack, vascular disease, age 65-74, female sex) score was determined by using age and co-morbidities at the time of enrollment for stratifying stroke risk. 5 Electrocardiogram (ECG) and echocardiogram (Echo) were performed in each case.
Data were entered in Microsoft excel 2007 and converted into IBM Statistical Package for the Social Sciences (SPSS), version 20. Continuous and categorical variables were presented as mean, percentage, and range. The tabular presentation was made for necessary variables.

DISCUSSION
AF is the most common sustained cardiac tachyarrhythmia and a major risk factor for thromboembolism. 7 Antithrombotic agents is highly effective for the reduction of thromboembolism and stroke in patients with AF. VKA is more effective than Free Full Text Articles are Available at www.jnma.com.np aspirin with a relative risk reduction of 36%. 8 This study has shown the underuse of antithrombotic therapy in the form of either OACs or antiplatelet agents in patients with both VAF and NVAF according to contemporary international guidelines. 9 About 37.6% of patients with VAF and 9.6% of patients with NVAF received OACs. The majority of patients with both VAF and NVAF were receiving Aspirin as an antithrombotic agent. Likewise, a study done in a rural part of Nepal by the same author showed that 39.1% of patients with NVAF who had a CHA 2 DS 2 score of > 2 and eligible for oral anticoagulants, only 18.9 % of patients received it. Similarly, only 22.7% of patients with valvular AF obtained OACs. 10 The stroke risk in patients with NVAF with a high score corresponds to greater risk while a low score corresponds to a lower risk. 6 The European Society of Cardiology (ESC) 11 and National Institute for Health and Care Excellence (NICE) 12 guidelines recommend that if the patient has a CHA2DS2-VASc score of two and above, OAC is recommended. In our study, among 135 patients with non-valvular AF, 75.5% had a CHA2DS2VASc score of ≥ 2 who were eligible for oral anticoagulants, only 9.6 % of patients received it with the majority having sub-therapeutic INR.
Most of the discussions about the risk of stroke are related to NVAF from the western world. Owing to the high burden of RHD in our part of the world, we have a good number of mitral stenosis (MS) which increases the risk of stroke even in absence of AF, and the risk is increased markedly in the presence of AF. The risk of stroke is increased 17 fold in patients with AF and RHD. 13 15 There is still an unmet need for safer and easier to use antithrombotic drugs in Nepal.
This is a small cross-sectional study representing patients from the eastern part of Nepal. The therapeutic INR values may not be appropriate for comparison with other studies because a single INR value was noted at the time of enrollment. We found the marked underuse of antithrombotic in patients with AF but we did not look at the physician's and patient's factors for not prescribing antithrombotic treatment. Bleeding risk scores were not taken into account. Since DOACs are not easily available or costly in our country so data on the use of DOACs is not presented in this study.

CONCLUSIONS
This study provides information about current practices of the use of antithrombotic agents and stroke risk in our patient's population with AF. OACs were markedly underused who qualified for it. This indicates the need for appropriate use of OACs to prevent thromboembolism and stroke. Improved awareness and understanding of the perceived risks of underutilization of antithrombotics among physicians and patients may improve its use. Specialized anticoagulation clinics and laboratory services at the grassroot health care center may help to initiate and maintain safe oral anticoagulant therapy.