**1. Introduction**

Endocarditis is defined as the inflammation of the endothelium. The first case of endocarditis was described by Lazare Rivière in the seventeenth century. Since then, the clinical, etiological, epidemiological and therapeutic knowledge around it has expanded remarkably. Nevertheless, it is a complex disease in constant evolution that requires a multidisciplinary approach. Most endocarditis has an infectious cause of bacterial origin. Being a disease of the endocardium, it not only affects native structures -more frequently the valves or cardiac structures subjected to special hemodynamic conditions such as in congenital heart disease-, but also other endothelizable surfaces, such as valve prostheses, catheters, electrodes, or percutaneous devices.

In this chapter we will address endocarditis on Cardiac Implantable Electronic Devices (CIED).
