Without knowing anything more about the data, it looks like a perfectly reasonable data model to me. Do you need the synthetic key removed for a specific reason, or only because you were taught that you should always remove synthetic keys?
If you want these tables to be connected by both _PK_KeyTable and by _PK_Historia_Paciente, then it is probably reasonable for them to be connected by a synthetic key. A synthetic key is simply how QlikView models a connection between tables that involves more than one field.
My opinion on synthetic keys along with some discussion and disagreement can be found in the following thread: