[Impact of biochemisty on the duration of treatment for pulmonary embolus].

Can the biochemical evidence for "new thrombophilic factors" influence the duration of AVK treatment following the occurrence of a first pulmonary embolus? Certainly for the classic but very rare antithrombin defects as well as for the existence of circulating anticoagulant. Possibly for protein C and S defects. On the other hand, the existence of a heterozygotic "Leiden" mutation of factor V, or factor II, and an increase of factors VIII, IX, or XI, do not at present warrant a change in AVK prescription. In effect, in the case where the existence of a thrombogenic state implies a prolongation of AVK treatment with its significant potential complications, it is indispensable that the risk/benefit ratio is well founded, which is not the case for these "new" thrombophilic states. The coexistence of several of these new biochemical anomalies (for example the association of a factor V and factor II mutation) probably represents an excess risk of thrombosis, but in this situation the reasoning remains the same. On the other hand, faced with a confirmed recurrence, the studies in the literature tell us that very long term treatment should be debated independently from the biochemical results. It is conceivable that there are biochemical anomalies (sometimes quite frequent which should be viewed as "normal variants") which, although they have great significance for improving the understanding of venous thrombo-embolic disease, do not at present warrant a change in our therapeutic protocols. Another facet of the problem concerns the use of D-dimers following the first months of AVK treatment in order to possibly distinguish patients at low risk of recurrence. The first results of this approach are interesting, but require confirmation before they can be used in practice.