Postoperative warfarin following mitral valve repair or bioprosthetic valve replacement

Short-term postoperative warfarin therapy has been used to decrease neurologic events following mitral valve repair or bioprosthetic replacement (MVR). The study aim was to compare the short- and long-term outcomes of patients undergoing mitral valve surgery with or without short-term postoperative warfarin.

A single academic US institution retrospective review was performed on discharged patients who underwent MVR between January 1996 and March 2010. Patients were allocated to two groups: MVR with four to six weeks of postoperative warfarin (n = 315; Warfarin group) or MVR without postoperative warfarin (n = 257; No warfarin group). Patients who required either preoperative or postoperative warfarin for any disease process (e.g., atrial fibrillation, mechanical valve, deep venous thrombosis) were excluded. Logistic and Cox proportional hazards regression models were constructed to evaluate the effects of warfarin on short- and long-term outcomes, respectively. Adjusted odds ratios (AOR) and adjusted hazard ratios (AHR), with 95% confidence intervals (CI) were constructed for each outcome. To reduce selection bias, propensity scoring methods were employed to balance the groups with respect to 54 preoperative variables.

Mean age was not significantly different between groups (No warfarin group = 56.8 +/- 14.5 years versus Warfarin group 55.9 +/- 12.9 years; p = 0.46). The average length of hospital stay was 9.8 +/- 8.4 days and 7.3 +/- 4.5 days in the No warfarin and Warfarin groups, respectively (p < 0.001). At the six-week follow up the incidences of stroke (p = 0.74), pleural effusions (p = 0.88), pericardial effusions (p = 0.75), and bleeding complications (p = 0.30) were similar between the two groups. In an unadjusted Kaplan-Meier analysis, the No warfarin group had a poorer long-term survival than the Warfarin group (p < 0.001). However, after propensity adjustment, the benefit of warfarin was not statistically significant (AHR = 0.66, 95% CI 0.40-1.08, p = 0.098).

The use of postoperative warfarin following MVR does not reduce the incidence of stroke at early follow up. However, there remains a trend for improved long-term outcomes in those patients receiving postoperative warfarin therapy.