Hi, @aghigi
You may also read about such a way of mapping on OHDSI Wiki and see examples here.
In a few words, if an ICD concept does not have a full semantic equivalent in SNOMED and cannot be mapped via single “Maps to”, it is mapped to several Standard concepts, which, in combination, fully or partially, reflect the meaning of ICD concept from different semantic sides. In the future, this approach will enable us to develop the SNOMED Extension containing full equivalent Standard concepts for those ICD entities, which currently are mapped to multiple SNOMED concepts.
@zhuk, thanks for mentioning!