The use of unfractionated heparin and low molecular weight heparins greatly reduces the risk of mortality and morbidity in acute coronary syndromes. However, their use has been associated with a risk of adverse events such as major bleeding, which has prompted researchers to seek safer alternative anticoagulants such as the synthetic inhibitors of the Xa factor - a crucial enzyme in the coagulation cascade. We systematically reviewed efficacy and safety of factor Xa inhibitors in treating acute coronary syndromes when compared to unfractionated heparins or low molecular weight heparins. A total of four trials involving 27,976 subjects was included. Xa inhibitors reduced all-cause mortality at 30 days, with the effect becoming more significant at 180 days. However, no significant differences were observed in the incidence of myocardial infarction or reinfarction at 30 days. Factor Xa inhibitors were found to be safer than enoxaparin, a low molecular weight heparin, due to reduced incidences of major and minor bleeding at 30 patients in patients receiving conservative treatment.
The therapeutic efficacy of factor Xa inhibitors in ACS seemed to be related to a reduced risk in all-cause mortality at 90 to 180 days, with a better safety profile than enoxaparin in terms of reduce incidence of major and minor bleeding.
The activation of coagulation mechanisms plays a central role in the pathogenesis of acute coronary syndromes (ACS). Administration of unfractionated heparin (UFH) and low molecular weight heparins (LMWH), agents preventing the progression of thrombus formation, is a crucial therapeutic strategy. However, some limitations related to their use have recently stimulated the development of new synthetic agents.
To evaluate the clinical efficacy and safety of factor Xa inhibitors for treatment of ACS compared to UFH or LMWH.
We searched the Cochrane Central Register of Controlled Trials (CENTRAL) of the Cochrane Library (Issue 1, 2008), PubMed, EMBASE and LILACS as well as the publications from International Congresses and the reference lists of the selected studies in December 2008.
We used randomized controlled trials (RCTs) comparing factor Xa inhibitors to UFH or LMWH during the course of ACS. Outcome measures included all-cause mortality, myocardial infarction, re-infarction, ischemia recurrence, and adverse events.
The selection, quality assessment and data extraction of the included trials were done independently by two authors and disagreements were resolved by consensus. Data were analysed by the use of risk ratio (RR) with 95% confidence interval (CI), and the numbers needed to treat (NNT) were reported as needed.
A total of four RCTs involving 27,976 subjects were included. Fondaparinux was the only factor Xa inhibitor identified in our included RCTs. Fondaparinux appeared to be related to a lower risk in all-cause mortality at 90 to 180 days (RR 0.89; 95% CI 0.81 to 0.97), especially in the group where enoxaparin (a LMWH) was the control drug. Fondaparinux was also associated with a lower risk in major and minor bleeding at 30 days compared to enoxaparin (RR 0.63, 95% CI 0.55 to 0.73; RR 0.34, 95% CI 0.28 to 0.43, respectively), but not when compared to UFHs (RR 1.41; 95% CI 0.49 to 4.10; RR 0.70, 95% CI 0.14 to 3.39 respectively).