This paper presents a study of dependability in the specific case of microstimulator implanted in the human body. In spite of the critical nature of this kind of application, there is no general study or standard of dependability for it. Based on real circuits developed in the DEMAR project, this paper illustrates the general attributes of dependability applied to medical implants. This kind of systems consists in generating an electrical signal (Functional Electrical Stimulation) into a nerve or a muscle to activate it and restore some lost abilities for para or tetraplegia. In this context, this paper highlights some key points of such system to enhance the general dependability.