Anticoagulation with warfarin following bioprosthetic mitral valve replacement (BMVR) is recommended by multiple practice guidelines. We assessed practice variability and patient characteristics associated with warfarin prescription following BMVR.
7,637 patients in the Society of Thoracic Surgeons Database (1/1/2008-6/30/2011) who were discharged following isolated, primary, non-emergent BMVR were analyzed. Patients requiring pre-op warfarin, those with pre-op atrial fibrillation or contra-indication to warfarin were excluded. The association between patient, hospital, and surgeon characteristics and warfarin prescription were evaluated.
58.0% of this cohort (median age, 66; female, 58.7%), was prescribed warfarin. Warfarin patients were older (67vs65yrs, p<0.0001), were less likely to have pre-operative: stroke (9.3%vs12.1%, p<0.001), CHF (51.4%vs54.1%, p<0.02) or dialysis (4.9%vs9.0%, p<0.001) and had a longer post-operative length of stay (8.0vs7.0 days, p<0.01). Warfarin was prescribed less often for patients with post-operative gastrointestinal events (44.4%vs55.6%, p< 0.001) but more often for patients with a post-operative myocardial infarction (75.8%vs24.2%, p<0.001), new atrial fibrillation (68.0%vs32.0%, p<0.001) and those requiring blood transfusions (intra-op (55.7%vs44.3%, p<0.001), post-op (57.0%vs43.0%, p<0.03). Similar rates of warfarin prescription were observed in patients requiring reoperation for bleeding (54.9%vs45.1%, p=0.20) and those with a post-operative stroke (53.6 %vs46.4 %, p=0.30). After adjusting for patient characteristics, significant surgeon and hospital variation in warfarin prescription at hospital was observed.
Although patient characteristics and post-operative events may be associated with the prescription of warfarin following BMVR, substantial surgeon and hospital variability remains. This variability largely ignores the established practice guidelines, and warrants further study to define the optimal anticoagulation strategy in BMVR patients.