**4. Diagnosis**

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

The microbiology of IE has also evolved over the years. The growing incidence of difficult-totreat infections, methicillin-resistant Staphylococcus, polymicrobial infections with Gramnegative bacteria, primary or opportunistic fungi, and multidrug-resistant organisms has also increased the difficulties in managing this patient population—and is independently a predictor of worse outcomes and hence is often an indication for urgent surgery [7]. Advances in the ability of microbiology labs to better identify unusual organisms—including genetic material—have allowed for more accurately defining causative agents that otherwise would have been considered "culture negative." Furthermore, as more aggressive approaches to the diagnosis and management of sepsis have resulted in a more assertive approach to insuring appropriate and timely cultures, antibiotics, and a search of an infectious focus, there might be a more accurate and timely diagnosis of extensive bacterial infections [8], while it is unclear whether such an aggressive approach toward "septic" patients has changed the incidence of endocarditis or whether the significant increase in case presentations is more of a function of

area is an understatement.

4 Contemporary Challenges in Endocarditis

**3. Microbiology**

Positive blood cultures remain the *sine quo non* in the diagnosis of endocarditis—but the corollary is not always true as patients can present with significant valvular pathology and negative cultures. The Duke Criteria, discussed at length elsewhere and in this text, remain the cornerstones for the diagnosis of endocarditis [13]. Advances in imaging, much like advances in the microbiologic assessment, of patients has also contributed significantly to the diagnosis and management of infected patients [14]. While transthoracic and transesophageal imaging are still first-line diagnostic tests to evaluate potentially infected cardiac structures and current guidelines help outline appropriateness criteria [2, 12]—there are growing indications and roles for alternative imaging modalities such as the computed tomography (CT), magnetic resonance imaging, and even 3D echocardiography [15]. As discussed in this text—advanced imaging modalities clearly have an expanding role in the diagnosis and management of patient with endocarditis. Early and frequent imaging can be extremely helpful in guiding and assessing the response to therapy.
