Factors Affecting Quality of Anticoagulation Achieved with Warfarin as Thromboprophylaxis for Stroke Prevention in Non-valvular Atrial Fibrillation

Background: Atrial fibrillation is one of the common indications of oral anticoagulation. Warfarin continues to be the most commonly used oral anticoagulant, particularly in developing countries. However, its use is limited by many factors, the most important of which is monitoring its therapeutic effect.

Objective: The objective of our study was to assess the anticoagulation quality in patients with atrial fibrillation receiving warfarin for thromboprophylaxis and the impact of various factors on the anticoagulation quality.

Materials and Methods: A total of 79 cases with non-valvular atrial fibrillation with or without a history of ischemic stroke attending the neurology clinic from September 2019 to March 2020 were studied. INR readings were taken from the outpatient record register which was converted to TTR (Time in Therapeutic Range) using the Rosendaal method. Cases that had received warfarin for less than 1 year were excluded. TTR value > 70% was considered as good anticoagulation control, TTR 60-70% as intermediate control and TTR < 60% as poor control.

Statistical Analysis: Descriptive statistics and Pearson chi-square analysis using SPSS-20.

Results and Conclusion: The mean TTR in our study was 59.72. Only 21.5% of cases in our study achieved a good anticoagulation control (TTR > 70%) while as 55.69% had a poor anticoagulation control (TTR < 60%). Males were reported to have a higher mean TTR value as compared to females (64.24 vs 55.54). High CHA2DS2VASc score and HAS-BLED score proved to have a strong predictive value for TTR less than 60. Individually, alcoholism, diabetes mellitus, hypertension and chronic kidney disease were found to be predictors of poor anticoagulation control i,e. TTR < 60. The presence of Transient ischemic attack or ischemic stroke was found to have a positive correlation with TTR > 70. A high number of adverse events (thromboembolic and bleeding) were reported in patients with TTR less than 60. The observations reflect the poor quality of anticoagulation in non-valvular atrial fibrillation patients on warfarin in the studied population.