Objectives To study the impact of time in therapeutic range (TTR) and international normalised ratio (INR) variability on the risk of thromboembolic events, major bleeding complications and death after mechanical heart valve (MHV) implantation. Additionally, the importance of different target INR levels was elucidated.

The safety and efficacy of warfarin in a large, unselected cohort of warfarin-treated patients with high quality of care is comparable to that reported for non-vitamin K antagonists. Warfarin is commonly used for stroke prevention in atrial fibrillation, as well as for treatment and prevention of venous thromboembolism. While reducing risk of thrombotic/embolic incidents, warfarin increases the risk of bleeding. The aim of this study was to elucidate risks of bleeding and thromboembolism for patients on warfarin treatment in a large, unselected cohort with rigorously controlled treatment. This was a retrospective, registry-based study, covering all patients treated with warfarin in the Swedish national anticoagulation register Auricula, which records both primary and specialised care. The study included 77,423 unselected patients with 100,952 treatment periods of warfarin, constituting 217,804 treatment years. Study period was January 1, 2006 to December 31, 2011. Atrial fibrillation was the most common indication (68 %). The mean time in therapeutic range of the international normalised ratio (INR) 2.0-3.0 was 76.5 %. The annual incidence of severe bleeding was 2.24 % and of thromboembolism 2.65 %. The incidence of intracranial bleeding was 0.37 % per treatment year in the whole population, and 0.38 % among patients with atrial fibrillation. In conclusion, warfarin treatment where patients spend a high proportion of time in the therapeutic range is safe and effective, and will continue to be a valid treatment option in the era of newer oral anticoagulants.

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Low-molecular-weight heparin (LMWH) is often recommended as a bridging therapy during temporary interruptions in warfarin treatment, despite lack of evidence. The aim of this study was to see whether we could find benefit from LMWH bridging. We studied all planned interruptions of warfarin within the Swedish anticoagulation register Auricula during 2006 to 2011. Lowmolecular-weight heparin bridging was compared to nonbridging (control) after propensity score matching. Complications were identified in national clinical registers for 30 days following warfarin cessation, and defined as all-cause mortality, bleeding (intracranial, gastrointestinal, or other), or thrombosis (ischemic stroke or systemic embolism, venous thromboembolism, or myocardial infarction) that was fatal or required hospital care. Of the 14 556 identified warfarin interruptions, 12 659 with a known medical background had a mean age of 69 years, 61% were males, mean CHADS 2 (1 point for each of congestive heart failure, hypertension, age 75 years, diabetes, and 2 points for stroke or transient ischemic attack) score was 1.7, and CHA 2 DS 2 -VASc score was 3.4. The total number of LMWH bridgings was 7021. Major indications for anticoagulation were mechanical heart valve prostheses 4331, atrial fibrillation 1097, and venous thromboembolism 1331. Bridging patients had a higher rate of thrombotic events overall. Total risk of any complication did not differ significantly between bridging (1.5%) and nonbridging (1.2%). Regardless of indication for warfarin treatment, we found no benefit from bridging. The type of procedure prompting bridging was not known, and the likely reason for the observed higher risk of thrombosis with LMWH bridging is that low-risk procedures more often meant no bridging. Results from randomized trials are needed, especially for patients with mechanical heart valves.

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