Patterns of anticoagulation following bioprosthetic valve implantation: observations from ANSWER

The American College of Cardiology/American Heart Association (ACC/AHA) guidelines recommend a three-month administration of warfarin following bioprosthetic valve replacement (BVR). However, strong evidence supporting this recommendation is lacking, making process variation likely.

In the ANSWER Registry, a total of 386 patients who had received either Epic or Biocor BVRs between May 2007 and August 2008 at 40 centers was enrolled. Patterns of discharge anticoagulation and outpatient International Normalized Ratio (INR) values were collected. Mortality, embolic, and bleeding events were assessed up to six months after BVR.

The median patient age was 74 years (interquartile range (IQR): 67-80 years), 39% of patients were female, and 65% were classified as a high thromboembolic risk. Warfarin was prescribed in 38% of all BVR patients, and in 49% of those at high risk of thromboembolism. The median time to therapeutic INR was nine days (IQR: 1 to 18 days), and 20% of patients failed to reach therapeutic levels. Among those patients achieving a therapeutic INR, 78% and 57% respectively had at least one subtherapeutic or supratherapeutic INR during the subsequent follow up to three months. During the follow up, patients treated with warfarin had similar rates of embolic events (2.8% versus 3.1%, p = 0.884), but a substantially higher incidence of bleeding than those not treated with warfarin (12% versus 3%, p = 0.0012). Among patients who were anticoagulated, those with supratherapeutic INR-values had a seven-fold higher risk for overt bleeding events (26% versus 3%).

Anticoagulation strategies after BVR are highly variable. In this population, challenges in achieving and maintaining therapeutic warfarin anticoagulation are common, and are associated with an increased risk of bleeding. Further studies are required to clarify the optimal post-BVR anticoagulation strategy.