The effects of a low international normalized ratio on thromboembolic and bleeding complications in patients with mechanical mitral valve replacement

BACKGROUND Mechanical heart valve replacement has an inherent risk of thromboembolic events (TEs). Current guidelines recommend an international normalized ratio (INR) of at least 2.5 after mechanical mitral valve replacement (MVR). This study aimed to evaluate the effects of a low INR (2.0-2.5) on thromboembolic and bleeding complications in patients with mechanical MVR on warfarin therapy. METHODS One hundred and thirty-five patients who underwent mechanical MVR were enrolled in this study. The end points of this study were defined as TEs (valve thrombosis, transient ischemic attack, stroke) and bleeding (all minor and major bleeding) complications. Patients were followed up for a mean of 39.6 months and the mean INR of the patients was calculated. After data collection, patients were divided into 3 groups according to their mean INR, as follows: group 1 (n = 34), INR <2.0; group 2 (n = 49), INR 2.0-2.5; and group 3 (n = 52), INR >2.5. RESULTS A total of 22 events (10 [7.4%] thromboembolic and 12 [8.8%] bleeding events) occurred in the follow-up period. The mean INR was an independent risk factor for the development of TEs. Mean INR and neurological dysfunction were independent risk factors for the development of bleeding events. A statistically significant positive correlation was found between the log mean INR and all bleeding events, and a negative correlation was found between the log mean INR and all TEs. The total number of events was significantly lower in group 2 than in groups 1 and 3 (P = 0.036). CONCLUSIONS This study showed that a target INRs of 2.0-2.5 are acceptable for preventing TEs and safe in terms of bleeding complications in patients with mechanical MVR.