**2. Epidemiology**

The incidence of infectious endocarditis, without a doubt, has increased significantly over the years. The reasons for this are multifactorial and reflect the growing number of patients who are at risk due to their comorbidities. The list of comorbidities is extensive and includes advancing age, chronic immunosuppression, end-stage renal failure, and those with preexisting intracardiac pathology. Furthermore, as patients are living longer and longer with more complex comorbidities, medical teams are seeing the pathological consequences of some

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

of the therapies that such patients require to prolong their lives. The dramatic increase in the use of cardiac support devices, such as pacemaker, defibrillators, intravascular monitoring devices, and left ventricular assist devices has presented unique and difficult challenges in management when patients are clinically dependent on them and then they become infected and may need to be removed. Clearly, endocarditis is one of those opportunistic problems that result from medical advances. However, without doubt, the largest populations of patients developing endocarditis are those with a history of intravenous drug abuse or those with a history of implanted cardiac devices [1, 2]. The undeniable worldwide epidemic of intravenous drug abuse has resulted in a dramatic increase in the incidence of younger patients presenting with polymicrobial invasive infections—often in the setting of overwhelming sepsis and difficult to manage social situations with established concerns of noncompliance. In this patient population, the primary cardiac infections might be the easiest of their presenting problems to manage long term. The other major patient population at significant risk is those with underlying cardiovascular pathologies requiring implantable support devices and lead system. In addition, the increasing long-term survival of patients with prosthetic heart valves, corrected congenital heart disease, and wider use of percutaneously implanted cardiac valves (i.e., TAVR) or repair devices (i.e., mitral clips) in high-risk surgical patients also place these patients at risk for device-related infection and the increasing incidence of endocarditis [3]. It is also becoming concerning, as discussed in this text, that infections in certain patient populations—such as those with end-stage renal disease requiring hemodialysis—are at substantial risk for endocarditis and life-threatening complications in ways that are only recently being appreciated and described in the literature. Nevertheless, guidelines for prophylactic antibiotics remain unclear in how "at risk" patients should be managed at the time of invasive procedures that might predispose to bacteremia and subsequent seeding of cardiac, native and prosthetic, structures [4–6]. To say that there is much controversy in this area is an understatement.
