Abstract
OBJECTIVE: To determine the optimal anticoagulation intensity of warfarin in a South-East Asian population with moderate-to-severe rheumatic mitral stenosis. METHODS: A multicentre, retrospective study examined patients with rheumatic mitral stenosis who had not undergone valve replacement or repair and required long-term warfarin therapy at two hospitals in Thailand from 2013 to 2018. The main outcomes were thromboembolism and major bleeding. Incidence rate ratios for these events at each level of anticoagulation intensity (international normalized ratio [INR]) were compared. RESULTS: The study included 933 patients with 3538 patient-years of follow-up, a mean follow-up of 3.8 years and 23 700 INR values. Mean age was 56.1 ± 11.8 years. During follow-up, there were 149 thromboembolic events (4.2 per 100 patient-years) and 132 major bleeding events (3.7 per 100 patient-years). Net adverse clinical events were lowest at INR 2.50-2.99, with no significant difference between INR 2.00-2.49 and 3.00-3.50. Standard INR (2.0-3.0) and high-intensity INR (2.5-3.5) had comparable net adverse clinical event rates (incidence rate ratio 0.99, 95% confidence interval [CI] 0.66-1.54, P = .99). However, thromboembolism incidence was higher with standard INR (incidence rate ratio 2.49, 95% CI 1.13-6.23, P = .013), while major bleeding was lower (incidence rate ratio 0.57, 95% CI 0.35-0.98, P = .045). No significant difference in intracranial haemorrhage rates was observed between the two INR intensities. CONCLUSION: The standard anticoagulation intensity is an optimal range for Asian population with moderate-to-severe rheumatic mitral stenosis. High intensity anticoagulation (INR of 2.50-3.50) further reduces thromboembolism but increases major bleeding but not intracranial haemorrhage.