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Take a look at a selection of our recent media coverage:
17th March 2022
Direct acting oral anticoagulants (DOACs) are more effective for the prevention of symptomatic venous thromboembolism in comparison to prophylactic dosing with low molecular weight (LMW) heparins. However, DOCAs are no more effective than high dose LMW heparins in non-cardiac surgical patients. This was the conclusion of a systemic review and network meta-analysis by researchers from the Department of Health Research Methods, Evidence, and Impact, McMaster University, Ontario, Canada
A venous thromboembolism is a significant problem in the peri-operative period with the potential to increase patient morbidity, mortality and associated health care costs. Typically, a venous thromboembolism presents as either a deep vein thrombosis or a pulmonary embolism. Although both the DOACs and LMW heparins are recognised as convenient and effective prophylaxis regimens against venous thromboembolism for at-risk surgical patients, there is a lack of direct and comparative evidence to guide clinician’s choice. Nevertheless, it seems that in practice, one survey of thrombosis experts revealed how 85.9% would recommend the use of LMW heparins.
With a level of uncertainty over the relative benefits of either DOACs or LMW heparins, the Canadian team undertook a systematic review and network meta-analysis of existing randomised controlled trials in which there was a comparison of LMW heparins, DOACs and no active treatment for thromboprophylaxis in patients undergoing non-cardiac surgery. The researchers suspected that the relative efficacy of the two therapeutic options would be similar across a range of surgical settings and hence used a network meta-analysis to enable a comparison to be made where there was an absence of direct comparative studies.
The team included randomised trials in adult patients (> 18 years of age) undergoing non-cardiac surgery, including general, urological, gynaecological, orthopaedic and thoracic procedures. They searched for studies in which the use of low dose LMW heparins (e.g., enoxaparin 40 mg daily), high dose (e.g., enoxaparin 30 mg twice daily) and DOACs had been employed. The outcome of interest was a reduction in symptomatic pulmonary embolism and/or deep vein thrombosis and they considered major bleeding as the primary anticipated harm.
DOACs and symptomatic venous thromboembolism
A total of 68 eligible studies with 45,445 patients were included in the analysis. In 25 trials with 30, 230 patients, 0.78% had a symptomatic venous thromboembolism and in 61 studies, 0.25% had a pulmonary embolism.
Overall and compared to no treatment, all three interventions were associated with a significant reduction in the odds of symptomatic venous thromboembolism. For example, DOACs (OR = 0.17, 95% CI 0.07 – 0.41), LMW heparins (OR = 0.33) and high dose LMW heparins (OR = 0.19).
When the different treatments were compared in the network meta-analysis, the use of DOACs was associated with a significant reduction in symptomatic venous thromboembolism compared to LMW heparin (odds ratio, OR = 0.53, 95% CI 0.32 – 0.89, p = 0.02). However, there was no significant difference compared to high dose LMH heparin (OR = 0.93, 95% CI 0.51 – 1.71).
In terms of bleeding, both DOACs and both doses of LMW heparins were associated with an increased risk of a major bleed. The risk was approximately two-fold higher for both DOACs and LMW heparins (e.g., OR = 2.01 for DOACs).
The authors concluded that both DOACs and LMW heparins are effective for symptomatic venous thromboembolism in non-cardiac surgery and that the former class of drugs are probably more effective and LMW heparins when used at the standard prophylactic dose.
Marcucci M et al. Benefits and harms of direct oral anticoagulation and low molecular weight heparin for thromboprophylaxis in patients undergoing non-cardiac surgery: systematic review and network meta-analysis of randomised trials BMJ 2022
27th January 2022
Prolonged TV viewing is associated with an increased risk of venous thromboembolism even among those who are physically active. This was the conclusion of a meta-analysis by a team from the National Institute for Health Research Bristol Biomedical Research Centre, Bristol, UK.
Both arterial thrombosis and venous thromboembolism (VTE) have been generally perceived as two distinct entities and while the traditional risk factors for arterial disease are not strongly associated with an increased risk of VTE, patients with VTE do carry these risk factors. Physical inactivity or sedentary behaviour, has been found to be independently associated with adverse cardiovascular outcomes, regardless of physical activity levels, whereas in contrast, a 2020 meta-analysis of 14 prospective studies, concluded that physical activity was protective such that higher levels of regular physical activity resulted in a lower incidence of VTE.
Prolonged TV viewing is a sedentary behaviour and thus intuitively linked to an increased risk of VTE. However, the available evidence is conflicting, with one study finding that greater frequency of TV viewing was independently associated with increased risk of VTE whereas another study found no evidence of an interaction between TV viewing, physical activity and the risk of VTE.
In trying to provide further clarity, the UK team sought to evaluate the magnitude of the prospective association between prolonged TV viewing and the risk of VTE. To enhance comparison and interpretations of the findings, the team dichotomised the data as prolonged vs never/seldom TV viewing.
From a total of 28 potentially eligible studies, only 3, which represented unique prospective cohort studies, including 131, 421 individuals and 964 VTE events with a follow-up duration of 5.1 to 19.8 years, were usable for their analysis.
The pooled multivariable adjusted relative risk (RR) of VTE comparing prolonged TV viewing compared to seldom/never, was 1.35 (95% CI 1.07 – 1.70). Interestingly, this positive association remained even after adjustment for physical activity which suggests that even though an individual might achieve the recommended amount of physically activity, this does not fully eliminate the risk of a VTE.
Based on these findings, the authors concluded that the results supported an association between prolonged TV viewing and a greater risk of a VTE. They added that frequent breaks and maintaining recommended levels of physical activity might be needed for VTE prevention but that further studies are required to explore this association in more detail.
Kunutsor SK et al. Television viewing and venous thrombo-embolism: a systematic review and meta-analysis Eur J Prev Cardiol 2022