3. Microbiology

been demonstrated to have a significant impact on the management and outcomes of infected patients. The goal of this text is to highlight some of the current concepts in the clinical charac-

There has been a significant increase in the overall incidence of infectious endocarditis—and there are many reasons for this. The two, probably, most important fundamental reasons are the growing number of patients with substantial comorbidities who are receiving therapies involving prosthetic material implanted into their hearts. Many of these patients have comorbidities that historically might have contraindicated advanced cardiac therapies (including heart valve surgery) years ago. Such comorbidities included not only frailty and advanced age but end-stage renal disease, history of solid or bone marrow transplantation, chronic highintensity immunosuppression, and multiple previous cardiac procedures. In addition, the fact that medical advances have resulted in these "sick" patients living longer, even if the absolute rate (i.e., cases/year) did not change, the total number of cases would increase as the overall

The second growing population of patients at risk for developing endocarditis are patients with a history of intravenous substance abuse—and even more so, those who continue to abuse IV drugs having already undergone a surgical procedure to repair/replace an infected cardiac valve [3, 4]. The global burden of substance abuse and the impact of infectious endocarditis are only recently been the sources of focused investigation with a growing appreciation of the magnitude of the problem [5]. Many of these patients tend to be younger—and as a function of their greater physiologic reserve, difficulties in getting appropriate access to healthcare and the means in which they become infected can result in this population presenting much later in the course of an infection with advanced cardiac structural destruction and are more likely to have polymicrobial or fungal infections. As many of these patients have received suboptimal therapy for their nonspecific presentations and symptoms, late presentations after weeks, or even months, of therapies for "viral syndromes," "community acquired pneumonias," or even "cellulitis" from local infections at the site of infection are not uncommon. Noncompliance with medical therapy, combined with mistrust in the healthcare system, in this population might also predispose them to presenting late in their disease. Nevertheless, as more patients receive advanced cardiac therapies—such as catheter-based valve replacements, implantable cardioverter defibrillators, pacemakers, intravascular remote pressure monitors, and ventricular assist devices—the risks for developing device-related infections are substantial and growing [6, 7]. Unfortunately, the growth in the overall utilization of these devices in sicker patients has exceeded our overall understanding of how to reduce, prevent, or provide prophylaxis against potential infections [8–10]. Furthermore, with the growing understanding of the natural history of endocarditis, risk factors for developing infections, the management of specific types of infections and their presenting complication, long-term outcomes of both medical and surgical therapies, and the overall heterogeneous

teristics, the presentation, the diagnosis, and the management options.

2. Epidemiology

4 Advanced Concepts in Endocarditis

population at risk over time has increased.

A growing challenge has also been the "war" between evolving resistant bacteria, multidrugresistant organisms, polymicrobial infections, and opportunistic fungi and the drug therapies that are available to safely and appropriately treat these infections. Such infections clearly have been shown to be predictors of poor outcomes and are often primary indications for urgent surgical intervention [11]. While advances in techniques used for testing of genetic techniques and cellular markers have improved the ability to define a causative agent, this does not inherently imply that such infectious are any easier to treat [12]. In addition, the growing recognition of "sepsis" and aggressiveness toward early treatment and diagnostic evaluations might have a secondary effect on the earlier recognition and overall incidence of diagnosing endocarditis. Nevertheless, without a doubt, the growing and routine use of immune modulating medications for common diseases such as rheumatoid arthritis, inflammatory bowel disease, and psoriasis (just to name a few) has also increased the incidence of unusual bacterial and fungal infections—of which progressing to endocarditis is common [13]. Another growing population is those adults with congenital heart disease. Many of these patients have had multiple previous surgical procedures involving prosthetic material and are, in general, living longer—both are risk factors for developing endocarditis [14, 15]. In addition, while the overall focus tends to be on infectious causes, there is clearly much to learn about noninfectious causes of endocarditis such as marantic or Libman-Sacks endocarditis [16].
