P4512Time in therapeutic range and risk of thromboembolism and bleeding in patients with mechanical heart valve prosthesis

Background: Oral anticoagulation with vitamin K antagonists (VKA) is recommended after mechanical heart valve replacement. However, data regarding the association between the quality of VKA treatment and the risk of complications are sparse. Purpose: This study sets out to examine the association between time in therapeutic range (TTR) and the risk of thromboembolic events and bleeding in patients with mechanical valve prostheses. Methods: Patients undergoing mechanical heart valve replacement (1997–2012) with available data on International Normalized Ratio (INR) values were identified in Danish registries. The quality of VKA treatment between discharge after valve replacement and 6 months post-discharge (index) was assessed as TTR >70% or <70%. Patients were followed from index until occurrence of an outcome of interest (i.e. thromboembolism and bleeding), death, or end of study (December 31, 2012). The risk of outcomes according to quality of VKA treatment was estimated with multivariable Cox regression. Results: In total, 659 patients undergoing mechanical heart valve replacement were included in the study (median age, 58.0 years [interquartile range (IQR) 50–64]; 70.1% men). Median number of INR measurements in the 6-month period after surgery was 13 (IQR 8–19). Median TTR was 54.9% (IQR 39.0–72.9), and 29.1% of patients had a TTR≥70%. Median follow-up was 6.1 years. The risk of thromboembolism was significantly lower in the group with TTR≥70% compared with TTR<70% (hazard ratio (HR) 0.44, 95% CI 0.22–0.85), while no significant difference concerning risk of bleeding among groups was found (HR 0.63, 95% CI 0.36–1.08).