Conceptualizing distributed Healthcare Information System is an important step toward the enhancement of clinical decision support system. In this paper, we propose a semantic mediation of Web Services interfaces for distributed healthcare system. Our proposal is an approach based on Web Services technology and their mediation in a Peer to Peer environment. This approach constitutes the foundation for the set-up of a mediation framework built around the JXTA P2P architecture applied to cardiology domain in collaboration with the National Institute of Health and Medical Research (INSER ERM 107). To achieve our goal, we used the OWL-S language as a means of describing semantics of Web Services interfaces, and the JXTA distributed architecture.