Cardiovascular · Topic 28 of 48

Infective Endocarditis

Cardiovascular · endocarditis

Infective Endocarditis

Fever plus a murmur is endocarditis until proven otherwise: cultures before antibiotics, Duke criteria, echo, and early surgery when the valve fails or infection is uncontrolled.

Key numbers

Draw 2–3 culture sets before antibiotics≥ 2, ideally 3 sets

Definite IE by 2023 Duke-ISCVID criteria2 major · 1 + 3 · 5 minor

Surgery for HF, uncontrolled infection, embolivegetation > 10 mm

Left-sided IE: 6 weeks of IV antibiotics6 wk if left-sided

01 · FirstDraw 2–3 culture sets before antibiotics

Before any antibiotic, draw at least 2 (ideally 3) blood culture sets from separate fresh venipunctures; in an acutely ill patient obtain them within 1–2 hours, then start empiric therapy.

02 · GiveEmpiric vancomycin plus ceftriaxone

If the patient is seriously ill, start empiric therapy after cultures covering staphylococci (including MRSA) and streptococci — typically vancomycin plus ceftriaxone in the US — then narrow to the organism's susceptibilities.

03 · DoSurgery for HF, uncontrolled infection, emboli

Consult cardiac surgery for heart failure from valve dysfunction, uncontrolled infection (persistent bacteremia, fungal or resistant organism, abscess, heart block), or embolic risk (vegetation > 10 mm or recurrent emboli).

Causes & risk factors

Why it happens

Streptococci and S. aureus cause most casesStreptococci and Staphylococcus aureus cause 80–90% of endocarditis; S. aureus and enterococcal cases are rising. S. aureus causes acute disease and can infect normal valves; viridans streptococci cause subacute disease.

Culture-negative: prior antibiotics or fastidious organismsNegative cultures usually mean prior antibiotics or organisms that grow poorly (Coxiella, Bartonella — diagnosed by serology or PCR), or another diagnosis such as noninfective endocarditis or atrial myxoma.

Presentation

What you'll see

Osler nodes tender, Janeway lesions painlessLook for fever with a new regurgitant murmur plus peripheral stigmata: tender Osler nodes on finger or toe pads, painless Janeway lesions on palms and soles, splinter hemorrhages, conjunctival petechiae and Roth spots.

Diagnosis & monitoring

Work-up

Definite IE by 2023 Duke-ISCVID criteria must know2023 Duke-ISCVID: definite endocarditis = 2 major, 1 major + 3 minor, or 5 minor criteria. Major = typical organism in ≥ 2 separate culture sets, or imaging showing vegetation, abscess, perforation or new regurgitation.

Do right now

In this order

First moves

Draw 2–3 culture sets before antibiotics≥ 2, ideally 3 sets

→

Empiric vancomycin plus ceftriaxone

→

TTE first, then TEE

→

Surgery for HF, uncontrolled infection, embolivegetation > 10 mm

Why each step

Draw 2–3 culture sets before antibioticsBefore any antibiotic, draw at least 2 (ideally 3) blood culture sets from separate fresh venipunctures; in an acutely ill patient obtain them within 1–2 hours, then start empiric therapy.

Empiric vancomycin plus ceftriaxoneIf the patient is seriously ill, start empiric therapy after cultures covering staphylococci (including MRSA) and streptococci — typically vancomycin plus ceftriaxone in the US — then narrow to the organism's susceptibilities.

TTE first, then TEEStart with transthoracic echo (sensitivity 50–90%); order transesophageal echo (90–100%) for a prosthetic valve, a nondiagnostic TTE, or confirmed endocarditis to look for abscess, perforation or fistula.

Surgery for HF, uncontrolled infection, emboliConsult cardiac surgery for heart failure from valve dysfunction, uncontrolled infection (persistent bacteremia, fungal or resistant organism, abscess, heart block), or embolic risk (vegetation > 10 mm or recurrent emboli).

Management

Orders

MSSA: nafcillin or cefazolin. MRSA: vancomycinNative-valve S. aureus endocarditis: nafcillin or oxacillin 2 g IV every 4 hours (or cefazolin) for methicillin-susceptible strains; vancomycin for MRSA, with daptomycin an option for right-sided disease.

Remove the whole infected device systemEndocarditis involving a pacemaker or defibrillator requires complete removal of the generator and all leads; change existing IV catheters and drain or debride any source of bacteremia.

Red flags & don'ts

Avoid harm

Hold anticoagulation after cerebral emboli avoidWithhold anticoagulation in patients with cerebral emboli because of hemorrhagic transformation; valve surgery is usually delayed about a month after intracranial hemorrhage or a major ischemic stroke.

New heart block suggests a valve-ring abscess complicationNew conduction block suggests a myocardial or valve-ring abscess (low septal abscesses; more common with prosthetic valves); heart block or abscess is an indication for surgery.

Left-sided emboli: brain, spleen, kidneys complicationLeft-sided vegetations embolize systemically: about 35% of patients have CNS events (stroke, TIA, abscess, ruptured mycotic aneurysm), plus splenic and renal infarcts; mycotic aneurysms can form in any major artery.

The rules

Know these

Left-sided IE: 6 weeks of IV antibioticsAntibiotics run 2–8 weeks by organism and valve: guidelines give 6 weeks of parenteral therapy for left-sided endocarditis, 6 or more weeks for prosthetic valves, and shorter courses for some right-sided cases.

Dental prophylaxis only for high-risk patientsGive prophylaxis (single pre-procedure dose, usually amoxicillin) only for gingival or periapical dental work in high-risk patients: prosthetic valve or valve-repair material, prior endocarditis, certain congenital heart disease, transplant valvulopathy.

Left-sided or right-sided endocarditis?

Commonly confused

Valve	Mitral or aortic
Typical patient	Prosthetic valve, prior endocarditis or device
Emboli	Systemic — brain, spleen, kidneys
Prognosis and management	Worse; surgery more often needed

More detail

Reference

Show 8 reference facts

Enterococcal endocarditis (native or prosthetic): ampicillin 2 g IV every 4 hours plus ceftriaxone 2 g IV every 12 hours for 6 weeks.

Penicillin-susceptible viridans streptococci on a native valve: penicillin G or ceftriaxone 2 g daily for 4 weeks, or 2 weeks when gentamicin is added.

Prosthetic valve endocarditis affects 1–2% of patients in the first year; early infection (< 2 months) is usually Staphylococcus epidermidis, other resistant bacteria or fungi from surgery.

In-hospital mortality of endocarditis is 15–20% and 1-year mortality approaches 40%; untreated endocarditis is always fatal.

In stable uncomplicated left-sided endocarditis, switching to oral antibiotics after at least 10 days of IV therapy was noninferior to full IV therapy in a randomized trial.

Urinalysis often shows microscopic hematuria, sometimes RBC casts from immune-complex glomerulonephritis; anemia, raised ESR and rheumatoid factor are common but nonspecific.

Every patient with endocarditis needs a dental evaluation and treatment of oral disease, and an echo at the end of therapy to set a new baseline.

FDG-PET/CT and cardiac CT add sensitivity, especially for prosthetic valves and device leads, and both are major imaging criteria in the 2023 Duke-ISCVID criteria.

Pearl

Cultures first, always: one empiric dose before blood cultures can leave you with culture-negative endocarditis and no organism to target.

Sources · Merck Manual Professional — Infective Endocarditis · Fowler VG et al. The 2023 Duke-ISCVID Criteria for Infective Endocarditis. Clin Infect Dis 2023;77:518–526 · Merck Manual Professional — Clinical Criteria for Infective Endocarditis (2023 Duke-ISCVID) table · Baddour LM et al. Infective endocarditis in adults: diagnosis, antimicrobial therapy and management of complications — AHA scientific statement. Circulation 2015;132:1435–1486 · American Dental Association — Antibiotic Prophylaxis Prior to Dental Procedures (summarizing the 2021 AHA scientific statement) · Starter sheet built from the verified AGACNP fact map (facts reviewed 2026-10-15).