Unfractionated heparin or low molecular weight heparin in patients with acute pulmonary embolism: a meta-analysis of randomized controlled trials

Abstract Introduction There is limited data on the use of unfractionated heparin (UFH) and low molecular weight heparin (LMWH) in patients admitted for acute pulmonary embolism (PE). Current ESC guidelines preferred LMWH over UFH based on extrapolated data. We aimed to compare UFH and LMWH in patients with acute PE using randomized controlled trials (RCTs). Methods A comprehensive literature search was performed from inception to 02/01/2024 of the PubMed database. Studies of adult patients comparing UFH to LMWH were evaluated for short-term (7-to-12 days) mortality, long-term mortality (90-days to 180-days), short-term (7-to-12 days) and long-term major bleeding (90-days to 180-days). Odds ratio (OR) with 95% confidence intervals (CI) were calculated using DerSimonian-Laird method. Results Of a total 2400 studies, nine RCTs with 1,996 subjects (1025 UFH and 971 LMWH) were included with mean age of 62.9 years and 48.5% males. There was no difference in short-term (OR= 0.89 [95% CI 0.44-1.82]; p=0.75; I2=0%; 6 trials) and long-term mortality (OR= 0.77 [95% CI 0.50-1.21]; p=0.26; I2=0%; 6 trials) with use of LMWH or UFH (Figure Panel A and B). Similarly, there was no difference in short-term (OR= 0.70 [95% CI 0.38-1.32]; p=0.27; I2=0%; 9 trials) and long-term major bleeding (OR= 0.92 [95% CI 0.53-1.60]; p=0.77; I2=0%; 6 trials) with use of LMWH or UFH (Figure Panel C and D). Overall, there was no evidence of publication bias using either funnel plot or eggers test (p > 0.05). Conclusions In this meta-analysis of 9 RCTs, there was similar efficacy and safety of UFH and LMWH in patients admitted for acute PE. However, future large-scale trials are needs to confirm these findings.