I have a study that i'm trying to identify incident events of VTE in us claims database. When reviewing a concept set I found that the ICD9 453.7 'Chronic venous embolism and thrombosis of other specified vessels' gets mapped over to SNOMED concept 'Venous thrombosis' (444247). I would have expected it to map to something that is under the 'Chronic disease of cardiovascular system' such as 'Chronic thrombosis of subclavian vein' (which is perhaps too specific, but definitely something under a chronic disease). Looking at a more specific code 453.73 "Chronic venous embolism and thrombosis of upper extremity, unspecified" maps over to "Deep venous thrombosis of upper extremity" when there is a snomed concept "Chronic deep venous thrombosis of upper extremity".
I am not sure if there's a general problem mapping 'chronic' to 'general' conditions in the vocab, but this is making it difficult to weed out chronic from non-chronic diagnosis codes from our US claims.