In this paper, Canadian researchers report that in the past, intravenous unfractionated heparin (UFH) was used routinely at their institution after heart valve replacement surgery to prevent thrombotic complications. They note that low-molecular-weight heparin (LMWH) is associated with a lower rate of heparin-induced thrombocytopenia (HIT) and HIT with thrombosis than UFH and may be a safer alternative after heart valve surgery. Therefore intravenous and subcutaneous UFH was replaced at their institution with subcutaneous LMWH in prophylactic or therapeutic doses for early anticoagulation after heart valve replacement surgery. They report their assessment of the efficacy and safety of anticoagulation with LMWH after heart valve surgery compared to UFH in this retrospective analysis.

Data were assessed for consecutive cardiovascular surgery patients in whom dalteparin (n = 100) was used as the postoperative anticoagulant. This group was compared to an earlier group of patients who received UFH (n = 103). The main outcomes included the efficacy of the anticoagulant regimens (incidence of valve thrombosis, arterial thromboembolic events, and venous thromboembolic events) and safety (major bleeding, HIT, thrombotic events in HIT-positive cases, and death).

The following findings were reported:

• There were fewer thrombotic events in the LMWH-treated group (4% vs. 11%, p=0.11), but this difference was not statistically significant.

• There was a higher rate of bleeding events in the UFH-treated group (10% vs. 3%, p=0.08).

• Six patients in the UFH-treated group developed HIT, 4 of whom had thrombotic events (HIT with thrombosis). In the LMWH-treated group, 3 patients developed HIT, 1 of whom had HIT with thrombosis.

The researchers conclude that their preliminary study found that an LMWH regimen after heart valve surgery was effective and safe, though they acknowledge that the findings are limited by the retrospective nature of the study and small sample size.