This Scientific Statement for healthcare professionals from the American Heart Association is the 2015 update to the 2005 iteration on the same topic—infective endocarditis (IE) in adults. The following are key points to remember:

1. Definition. The definition of IE is based on the modified Duke criteria, including pathologic criteria (evidence of micro-organisms) and clinical criteria; and is definite, possible, or rejected IE.
2. Blood cultures. At least three sets of blood cultures should be obtained from different venipuncture sites, with the first and second separated by at least 1 hour.
3. Echocardiography. Transthoracic echocardiography (TTE) should be obtained expeditiously in all patients suspected of having IE. Transesophageal echocardiography (TEE) should be performed if initial TTE images are inadequate or negative in patients with an ongoing suspicion for IE, or with an initially positive TTE among patients with concern for intracardiac complications. If there is a high suspicion for IE despite a negative TEE, a TEE should be repeated after 3-5 days. In addition, TEE should be repeated in a patient with an initially positive TEE if clinical features suggest a new intracardiac complication. Finally, TTE is reasonable at the completion of antibiotic therapy, in order to establish a new baseline.
4. Potential need for surgical intervention. The following clinical and echocardiographic features suggest a potential need for surgical intervention:
   • Persistent vegetation after systemic embolization.
   • Anterior mitral leaflet vegetation, especially >10 mm.
   • ≥1 embolic event during the first 2 weeks of antimicrobial therapy.
   • Increase in vegetation size despite appropriate antimicrobial therapy.
   • Acute aortic or mitral regurgitation with signs of heart failure.
   • Heart failure unresponsive to medical therapy.
   • Paravalvular extension.
   • Valvular dehiscence, rupture, or fistula formation.
   • New heart block.
   • Large abscess or extension of abscess despite appropriate antimicrobial therapy.
5. Antimicrobial therapy. Specific antibiotic treatment recommendations are made for:
   • Native valve highly susceptible (MIC ≤0.12 µg/ml) viridans group streptococci (VGS) IE.
   • VGS and S gallolyticus (bovis) with MIC >0.12 to <0.5 µg/ml.
   • A defective and Granulicatella species, and VGS with penicillin MIC ≥0.5 µg/ml.
   • VGS or S gallolyticus involving prosthetic material.
   • Staphylococci.
   • Staphyococci involving prosthetic material.
   • Enterococci.
   • HACEK micro-organisms.
   • Non-HACEK gram-negative bacilli.
   • Culture-negative endocarditis.
   • Fungi.
6. Early surgery (native valve IE). Early valve surgery is recommended, or should be considered, for native left-sided IE in the following scenarios:
   • Valve dysfunction resulting in symptoms or signs of heart failure.
   • IE caused by fungi or highly resistant organisms.
   • IE complicated by heart block, annular abscess, or destructive perforating lesions.
   • Persistent infection (bacteremia or fever) lasting >5-7 days after the start of appropriate antimicrobial therapy, assuming other sources of infection or fever have been excluded.
   • Recurrent emboli or persistent/enlarging vegetations despite appropriate antimicrobial therapy.
7. Early surgery (prosthetic valve IE). Early valve surgery is recommended, or should be considered, for prosthetic vale IE in the following scenarios:
   • Symptoms or signs of heart failure resulting from valve dehiscence, intracardiac fistula, or severe prosthetic dysfunction.
   • Persistent bacteremia >5-7 days after the start of appropriate antimicrobial therapy.
   • Prosthetic valve IE complicated by heart block, annular abscess, or destructive perforating lesions.
   • Prosthetic valve IE caused by fungi or highly resistant organisms.
   • Recurrent emboli despite appropriate antimicrobial therapy.
8. Anticoagulation. Among patients with a mechanical valve and IE who have experienced a central nervous system (CNS) embolic event, it is reasonable to discontinue for 2 weeks all forms of anticoagulation. Although continuation of established antiplatelet therapy is reasonable among patients with IE and no bleeding complications, aspirin or another antiplatelet agent should not be initiated as adjunctive therapy at the time of IE diagnosis.
9. CNS imaging. CNS imaging should be performed to detect intracranial mycotic aneurysm or CNS bleeding in patients with IE who develop severe localized headache, neurological deficits, or meningeal signs.

Keywords: Anticoagulants, Anti-Infective Agents, Cardiac Surgical Procedures, Echocardiography, Echocardiography, Transesophageal, Endocarditis, Bacterial, Endocarditis, Heart Block, Heart Failure, Heart Valve Diseases, Mitral Valve Insufficiency, Platelet Aggregation Inhibitors, Staphylococcus

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