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Fixed-dose low-molecular-weight (LMW) heparin and
dose-adjusted intravenous unfractionated heparin both demonstrated
similar symptomatic events, and major and minor bleeding events,
in the initial treatment of pulmonary embolism (PE), according to
a meta-analysis of randomised controlled trials.
Unfractionated heparin is widely used to treat PE; however, the
role of LMW heparin in this area is less certain.
LMW heparin has been shown to be as safe and effective as unfractionated
heparin in the initial treatment of deep venous thromboembolism
(DVT), yet is easier to manage because it is administered subcutaneously
at fixed doses without laboratory monitoring, allowing a number
of patients to be treated at home.
Daniel J. Quinlan, MBBS, at King's College Hospital, London, United
Kingdom, and colleagues at the Royal Perth Hospital, Australia,
evaluated the safety and efficacy of LMW heparin in comparison to
intravenous unfractionated heparin in the initial treatment of PE.
The analysis included data from 12 randomised controlled trials
on 1,951 patients with symptomatic PE or asymptomatic PE with symptomatic
DVT. Each trial compared fixed-dose LMW heparin with dose-adjusted
intravenous unfractionated heparin and objectively measured the
incidence of symptomatic venous thromboembolism, death, major bleeding,
and minor bleeding.
"Our results suggest that in terms of thromboembolic recurrences
and major bleeding complications, low-molecular-weight heparin is
as effective and safe as unfractionated heparin for the initial
treatment of pulmonary embolism," wrote the authors.
LMW heparin was associated with a non-significant decrease in symptomatic
events at end of treatment and 3 months after treatment. Specifically,
3% of patients taking LMW heparin had a symptomatic event, while
4.4% of patients given unfractionated heparin had such an event
3 months after treatment. Notably, a similar treatment effect was
seen in both symptomatic and asymptomatic PE patients.
The incidence of major bleeding was 1.4% for patients taking LMW
heparin and 2.3% for those taking unfractionated heparin; the incidence
of minor bleeding events was 6.8% and 5.5%, respectively. Neither
comparison reached statistical significance.
Rates of all-cause mortality were also similar between groups.
The authors caution that these results "are tempered by the modest
number of outcome events in the trials."
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