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  • br Pathophysiology and risk factors Patient with


    Pathophysiology and risk factors Patient with CIED may get infected at time of initial liquiritin or during pocket revision for device change or upgrade [8,2]. Device erosions are by default infected but most commonly are a secondary manifestation of slow growing underlying infection [8]. Pocket infection can track along the leads leading to endovascular infection. Less commonly, the pocket or the intravascular portion of a CIED can become infected as a result of hematogenous seeding during an episode of bacteremia [8,2,14]. The overlap between “pocket infection” and “endovascular infection” is large. Many patients with CIED pocket infection have positive blood cultures and even vegetation on the leads [7]. Most infections are monomicrobial but about 10% are polymicrobial [7]. Staphylococcal species with its ability to form biofilms account for over 80% of these infections [7,15]. Recently there has been increasing trend toward methicillin-resistant Staphylococcal species [7,9,10,15–17]. Poorly timed cultures or prior antibiotic use can lead to negative cultures despite clear clinical evidence of CIED infection [7]. Other microorganisms involved include Corynebacterium species, Enterococci, Gram-negative bacilli, fungi, anaerobes, Candida species, and mycobacteria [7,15]. Different studies have identified different risk factors for developing CIED infections. These factors can generally be divided into three groups: patient-related, procedure-related and microorganism related and they are presented in Table 1.
    Diagnosis Patients with CIED infections can have different presentations. Most patients present with pulse generator pocket infection manifested by inflammatory changes that involve the pocket itself (Erythema, tenderness, warmth, drainage, and erosion) [7,15] (Fig. 1). These local findings can sometimes be accompanied by systemic signs and symptoms (fever, chills, nausea/vomiting etc.). Other patients may present with a device pocket that looks intact, but with combination of inflammatory signs and symptoms supported by positive blood cultures and imaging data (echocardiography or computed tomography) that suggest endovascular infection of the CIED (Figs. 2 and 3). Patients are classified as having CIED endocarditis if they have echocardiographic evidence of vegetations and two or more positive blood cultures for typical skin organisms (coagulase-negative Staphylococci, Corynebacterium species, Propionobacterium species, or one positive blood cultures for all other microorganisms. All patients with suspected CIED infection should have two sets of blood cultures drawn prior to initiation of any antibiotic therapy. Percutaneous aspiration of the generator pocket should not be performed as part of the diagnostic evaluation and is considered contraindicated [2]. Transthoracic echo (TTE) is of great value and if negative transesophageal echo (TEE) should be performed especially among patients with positive blood cultures or suspected CIED endocarditis as it is more sensitive in detecting vegetations. In our experience, we found that many patients presenting with pocket infection could have evidence of vegetations on TTE or TEE [7]. This has lowered our threshold in obtaining TEE for the majority of patients presenting with CIED infection. One however should be careful in interpreting echo findings. It is not unusual to detect echo-densities adherent to the leads. These often represent thrombus or fibrous tissue rather than true vegetation. Making the distinction visually could be challenging and often impossible. Therefore, the interpretation of the echo findings should take into account the clinical scenario. Incidental finding of a small mass adherent to the leads in the absence of any findings to suggest infection is probably thrombus or fibrous tissue and does not require any intervention. On the other hand, the lack of echo findings does not rule out the diagnosis of CIED infection. In patients with bacteremia without any echocardiographic findings, relapsing infections after completion of antibiotic course or persistent bacteremia despite antibiotic therapy support the diagnosis of CIED infection that requires its removal [2].