What are the notes from the Braunwald cardiology textbook on Infective Endocarditis?

From the Guidelines

Braunwald's cardiology textbook emphasizes that infective endocarditis (IE) is a microbial infection of the endocardial surface of the heart, most commonly affecting the heart valves, and the diagnosis requires clinical suspicion, positive blood cultures, and echocardiographic evidence of vegetation or abscess, with empiric therapy typically including vancomycin plus ceftriaxone until culture results are available, as recommended by the American Heart Association 1. The diagnosis of IE requires a combination of clinical suspicion, positive blood cultures, and echocardiographic evidence of vegetation or abscess.

• Risk factors for IE include prosthetic valves, previous endocarditis, congenital heart disease, IV drug use, and degenerative valve disease.
• Common causative organisms include Staphylococcus aureus, viridans streptococci, enterococci, and HACEK organisms.
• Empiric therapy typically includes vancomycin (15-20 mg/kg IV q12h) plus ceftriaxone (2g IV daily) until culture results are available, as recommended by the American Heart Association 1.
• Definitive therapy depends on the identified organism, with penicillin G (12-18 million units/day IV) or ceftriaxone for streptococcal IE, vancomycin for MRSA, and combination therapy for enterococcal IE, typically for 4-6 weeks, as recommended by the Infectious Diseases Society of America 1.
• Surgical intervention is indicated for heart failure due to valve dysfunction, uncontrolled infection, prevention of embolic events with large vegetations (>10mm), or prosthetic valve endocarditis with complications.
• Prophylaxis is recommended only for high-risk patients (prosthetic valves, previous IE, certain congenital heart diseases, cardiac transplant recipients with valvulopathy) undergoing dental procedures involving manipulation of gingival tissue, with the standard prophylactic regimen being amoxicillin 2g orally 30-60 minutes before the procedure, with alternatives for penicillin-allergic patients, as recommended by the American Heart Association 1. The most recent and highest quality study recommends that patients with culture-negative endocarditis should be classified into 2 groups, with one group including patients who received antibiotic therapy before collection of blood cultures, and the other group including patients who did not receive antibiotic therapy, with empiric therapy tailored to the specific group, as recommended by the American Heart Association 1.

From the Research

Overview of Infective Endocarditis

• Infective endocarditis is a microbial infection of the endocardial surface of the heart 2, 3
• The choice of antibiotic therapy for bacterial endocarditis is determined by the identity and antibiotic susceptibility of the infecting organism, the type of cardiac valve involved, and characteristics of the patient 4

Antibiotic Regimens for Infective Endocarditis

• Treatment with aqueous penicillin or ceftriaxone is effective for most infections caused by streptococci 4
• A combination of penicillin or ampicillin with gentamicin is appropriate for endocarditis caused by enterococci that are not highly resistant to penicillin 4
• Vancomycin should be substituted for penicillin when high-level resistance is present 4
• Native valve infection by methicillin-susceptible staphylococci is treated with nafcillin, oxacillin, or cefazolin 4
• Infection of a prosthetic valve by a staphylococcal organism should be treated with three antibiotics: oral rifampin and gentamicin and either nafcillin, oxacillin, cefazolin, or vancomycin, depending on susceptibility to methicillin 4

Comparison of Antibiotic Regimens

• Limited and very low-quality evidence suggests that there are no conclusive differences between antibiotic regimens in terms of cure rates or other relevant clinical outcomes 2, 3
• A short-course antibiotic regimen compared to conventional antibiotic treatment for gram-positive cocci infective endocarditis showed that a shorter antibiotic time period would be as efficient and safe as the classic 4 to 6 weeks antibiotic regimen 5
• Ampicillin plus ceftriaxone (AMP + CTR) was effective against non-faecalis/non-faecium enterococci, but its clinical efficacy in IE cases is limited 6

Clinical Implications

• The choice of antibiotic regimen should be based on the specific characteristics of the patient and the infecting organism 4
• Further research is needed to determine the most effective antibiotic regimens for infective endocarditis 2, 3