Enoxaparin Is Effective and Safe as Bridging Anticoagulation in Patients with a Mechanical Prosthetic Heart Valve who Require Temporary Interruption of Warfarin because of Surgery or an Invasive Procedure.

Background: Enoxaparin is a low-molecular-weight heparin (LMWH) that is widely used in patients with an acute coronary syndrome and venous thromboembolism. However, there is concern about its use in patients with mechanical prosthetic heart valve because of recent reports of fatal TE occurring in pregnant women with a mechanical heart valve who received long-term enoxaparin, instead of warfarin, during pregnancy.

Patients and Methods: We performed a prospective cohort study to assess the efficacy and safety of enoxaparin as bridging anticoagulation in a consecutive patients with a mechanical prosthetic heart valve who required temporary interruption of warfarin therapy because of an elective surgical or other invasive procedure. Patients had warfarin interruption and bridging anticoagulation based on a standardized peri-operative protocol and underwent clinical follow-up for 3 months after surgery. We determined the incidence and associated 95% confidence interval (CI) during the follow-up period for the following outcomes: major bleeding; arterial thromboembolism (stroke, rtansient ischemic attack, systemic embolism, valve thrombosis); all-cause death.

Results: There were 174 patients included in this cohort (100 males; mean age: 67±10 years; mean weight: 76±16 kg; 115 with a mechanical aortic valve; 59 with a mechanical mitral valve or combined mechanical aortic and mitral valves) who received bridging anticoagulation with subcutaneous enoxaparin, 1 mg/kg twice-daily. No patient was lost to follow-up. Warfarin therapy was interrupted 5.7±2.2 days before the procedure. The mean number of doses of enoxaparin (1 mg/kg) administered before the procedure was 5.7±1.4 doses. After the procedure, warfarin was resumed on the evening or the next day after the procedure, and the mean number of doses of enoxaparin administered was 6.0±2.2 doses. After 3 months of clinical follow-up, 4 patients developed non-fatal major bleeding (2.3%; 95% CI: 0.06–5.7), 4 patients died (2.3%; 95% CI: 0.06–5.7), and 1 patient had a non-fatal stroke (0.56%; 95% CI: 0.01–3.1). There were no episodes of valve thrombosis or systemic embolism.

Conclusions: Enoxaparin appears to be effective and safe as bridging anticoagulation in patients with a mechanical prosthetic heart valve who require temporary interruption of warfarin therapy.