Low-molecular-weight heparin as a bridging anticoagulant early after mechanical heart valve replacement

After mechanical heart valve replacement (MHVR), long-term use of unfractionated heparin is sometimes required because vitamin K antagonists (VKA) are temporarily contraindicated or because the time to reach the target international normalized ratio is long. The aim of this study was to investigate the feasibility of low-molecular-weight heparin treatment in these patients.

This work was conducted as a prospective study. We selected all patients (n=695) who underwent MHVR and were transferred to a postoperative cardiac rehabilitation center between January 2000 and January 2005. The study focused on patients who had not yet started VKA therapy or who had a below-target international normalized ratio despite VKA therapy. Unfractionated heparin was replaced by enoxaparin (100 IU/kg BID) until VKA treatment was fully effective. Two hundred fifty patients (60+/-11 years old) were enrolled 16+/-11 days after surgery (aortic valve replacement, n=190; mitral valve replacement, n=34; double valve replacement, n=26). Of these, 50% had permanent or transient atrial fibrillation, 40% had hypertension, 13% had diabetes, and 19% had a history of cardiac surgery. The mean duration of low-molecular-weight heparin treatment was 8.3+/-6.0 days. Patients were followed for 90 days, during which there were two major and three minor bleeding episodes and one transient ischemic attack. There were no cases of valve thrombosis and no deaths.

After MHVR, one third of patients leave the cardiac surgery unit before VKA treatment is fully effective. Bridging anticoagulation therapy with enoxaparin appears to be feasible during this high-risk period for thromboembolism and could shorten the length of hospital stay.