Perspective:

Data from prior studies clearly demonstrate that risk of venous thromboembolism and pulmonary embolism are increased in patients hospitalized for acute medical illness, though not nearly so much as patients hospitalized for surgical procedures. Although the risk is lower in medical patients, because of their larger numbers, the majority of pulmonary embolism cases occur in acutely ill medical, rather than surgical, patients. Prior studies have also clearly demonstrated that rates of venous thromboembolism, as documented by objective testing, are reduced in acutely ill hospitalized medical patients through the use of low molecular weight heparin prophylaxis. Nonetheless, medical thromboprophylaxis has not been shown to reduce mortality, and, possibly as a result, continues to be significantly underused. The current study attempted to determine if medical thromboprophylaxis use is associated with a reduction in mortality, in a very large randomized trial among acutely ill hospitalized medical patients. Despite the large size of this study, no difference in mortality could be discerned. This suggests that either the mortality reduction with medical thromboprophylaxis is too small (or absent) to be detected in this large study, or the study design led to possibly erroneous findings. Although intended to be definitive, the study raises many questions. First, the mortality rate observed was very low. Furthermore, the overwhelming majority of patients were enrolled in Asian countries, where the rate of venous thromboembolism is known to be much lower than in western nations. We are therefore left with the conundrum of knowing that medical thromboprophylaxis is effective at preventing venous thromboembolism, but appears, in this study, to be associated with no reduction in mortality. Further study is clearly warranted.