Randomised, controlled trial of low-dose heparin for prevention of fatal pulmonary embolism in patients with infectious diseases. The Heparin Prophylaxis Study Group

Fatal pulmonary embolism and other thromboembolic complications are common in hospital inpatients. However, there is little evidence on the routine use of pharmacological thromboprophylaxis in non-surgical patients. We assessed the efficacy and safety of low-dose heparin in the prevention of hospital-acquired, clinically relevant, fatal pulmonary embolism in patients with infectious diseases. Our study used the postrandomisation consent design. 19,751 consecutive patients, aged 55 years or older, admitted to departments of infectious diseases in six Swedish hospitals, were screened for inclusion in the randomised, controlled, unblinded, multicentre trial. Of the eligible patients, 5776 were assigned subcutaneous standard heparin (5000 IU every 12 h) until hospital discharge or for a maximum of 3 weeks; 5917 were assigned no prophylactic treatment (control group). We sought consent only from the heparin group. Follow-up was for 3 weeks after discharge from hospital or for a maximum of 60 days from randomisation. The primary endpoint was necropsy-verified pulmonary embolism of predefined clinical relevance. By intention-to-treat analysis mortality was similar in the heparin and control groups (5.3 vs 5.6%, p = 0.39) and the median time from admission to death was 16 days in both groups (IQR 8-31 vs 6-28 days). Necropsy-verified pulmonary embolism occurred in 15 heparin-treated and 16 control-group patients. There was a significant difference between heparin and control groups in median time from randomisation to fatal pulmonary embolism (28 [24-36] vs 12.5 [10-20] days, p = 0.007). This difference corresponds to the duration of heparin prophylaxis. Non-fatal thromboembolic complications occurred in more of the control than of the heparin group (116 vs 70, p = 0.0012). Our findings do not support the routine use of heparin prophylaxis for 3 weeks or less in large groups of non-surgical patients. Further studies are needed to investigate whether heparin prophylaxis of longer duration may prevent fatal pulmonary embolism.