The paper describes several classification systems that could improve patient safety through semantic interoperability among contemporary electronic health record systems (EHR-Ss) with support of the HL7 v3 standard. We describe a proposal and a pilot implementation of a semantic interoperability platform (SIP) interconnecting current EHR-Ss by using HL7 v3 messages and concepts mappings on most widely used classification systems. The increasing number of classification systems and nomenclatures requires designing of various conversion tools for transfer between main classification systems. We present the so-called LIM filler module and the HL7 broker, which are parts of the SIP, playing the role of such conversion tools. The analysis of suitability and usability of individual terminological thesauri has been started by mapping of clinical contents of the Minimal Data Model for Cardiology (MDMC) to various terminological classification systems. A national-wide implementation of the SIP would include adopting and translating international coding systems and nomenclatures, and developing implementation guidelines facilitating the migration from national standards to international ones. Our research showed that creation of such a platform is feasible; however, it will require a huge effort to adapt fully the Czech healthcare system to the European environment.