About This Page
This is a clinician-written, evidence-based summary aligned to the USMLE Step 2 CK Content Outline. It is intended for medical students preparing for USMLE Step 2 CK. Management reflects current ACC/AHA, USPSTF, and APA guidelines. Always cross-reference with UpToDate, institutional protocols, and clinical judgment.
The Bottom Line
- Suspect endocarditis with persistent fever plus murmur, positive blood cultures, embolic phenomena, injection drug use, prosthetic valve, or intracardiac device
- Obtain three sets of blood cultures from separate venipuncture sites before antibiotics if stable
- TTE first in many patients; TEE is preferred for prosthetic valves, intracardiac devices, S aureus bacteremia, complications, or nondiagnostic TTE with high suspicion
- Common organisms: S aureus, viridans streptococci, enterococci, coagulase-negative staph in prosthetic valves, HACEK organisms
- Empiric therapy depends on native vs prosthetic valve and acuity; definitive therapy is prolonged IV bactericidal antibiotics
- Surgery is needed for heart failure from valve dysfunction, uncontrolled infection, abscess, recurrent emboli, or selected large vegetations
Overview
Infective endocarditis is infection of a native valve, prosthetic valve, or endocardial surface. It causes vegetations composed of organisms, platelets, and fibrin, leading to persistent bacteremia, valve destruction, abscess, embolization, and immune complex disease. This infectious diseases page summarizes diagnosis and antimicrobial management; detailed murmurs and valvular complications can be cross-referenced with cardiovascular content.
Epidemiology
Risk factors include prior endocarditis, prosthetic valves, congenital heart disease, intracardiac devices, hemodialysis, injection drug use, degenerative valve disease, indwelling vascular catheters, and recent bacteremia. S aureus is the leading cause of acute endocarditis and is common in injection drug use and healthcare-associated disease. Viridans streptococci follow dental/oral sources. Enterococcus is associated with genitourinary or gastrointestinal sources and older adults.
Clinical Features
Symptoms
Fever, chills, night sweats, malaise, anorexia, weight loss
New or changing murmur, dyspnea, orthopnea, or heart failure symptoms
Stroke, focal neurologic deficit, back pain, flank pain, abdominal pain, or limb ischemia from emboli
Persistent bacteremia with S aureus, Enterococcus, or Candida
Injection drug use with fever and pleuritic chest pain may indicate right-sided endocarditis with septic pulmonary emboli
Prosthetic valve endocarditis may present with fever, heart failure, dehiscence, or conduction block
Signs
Murmur of regurgitant valve lesion or signs of heart failure
Petechiae, splinter hemorrhages, Janeway lesions, Osler nodes, Roth spots
Focal neurologic deficits or meningismus from emboli or mycotic aneurysm
Splenomegaly in subacute disease
New AV block suggests perivalvular abscess, especially aortic valve infection
Investigations
First-line
Blood cultures x3Obtain from separate sites before antibiotics if stable; persistent positivity is a major diagnostic clue
CBC, CMP, ESR/CRP, urinalysisAnemia, leukocytosis, renal injury, hematuria/proteinuria from immune complex glomerulonephritis
Transthoracic echocardiographyInitial imaging for suspected native valve IE; detects vegetation, regurgitation, and ventricular function
Second-line
Transesophageal echocardiographyHigher sensitivity; preferred for prosthetic valves, devices, S aureus bacteremia, suspected abscess, poor TTE windows, or high clinical suspicion
ECGNew conduction abnormality suggests perivalvular extension/abscess
CT/MRI targeted imagingEvaluate embolic stroke, splenic/renal infarct, vertebral osteomyelitis, or mycotic aneurysm
Specialist
Culture-negative workupIf cultures negative: prior antibiotics, Coxiella, Bartonella, Brucella, HACEK, fungi, Tropheryma whipplei; use serology/PCR as guided by exposure
Cardiac surgery consultationHeart failure, abscess, prosthetic dehiscence, persistent bacteremia, fungal IE, recurrent emboli, or large mobile vegetation
1
Initial management
- If stable, obtain three blood culture sets before antibiotics
- If unstable or acute destructive disease suspected, obtain cultures rapidly and start empiric IV therapy
- Empiric native valve severe disease often includes vancomycin plus cefepime or ceftriaxone depending healthcare exposure and local practice
- Consult infectious diseases for all definite or strongly suspected endocarditis
2
Pathogen-directed therapy
- MSSA: nafcillin/oxacillin or cefazolin; MRSA: vancomycin or daptomycin
- Viridans streptococci: penicillin G or ceftriaxone depending susceptibility; gentamicin only in selected regimens
- Enterococcus: ampicillin plus ceftriaxone is commonly used for E faecalis; vancomycin-based regimens if beta-lactam allergy/resistance
- HACEK: ceftriaxone is typical
- Candida/fungal IE: antifungal therapy plus surgery usually required
3
Surgical indications
- Heart failure due to acute severe valve regurgitation
- Uncontrolled infection: abscess, persistent bacteremia, enlarging vegetation, resistant organism, fungal infection
- Prevention of emboli: recurrent emboli or large mobile left-sided vegetation in selected cases
- Prosthetic valve dehiscence, severe dysfunction, or abscess
4
Prophylaxis
- Dental prophylaxis only for highest-risk cardiac conditions: prosthetic valve/material, prior IE, certain congenital heart disease, cardiac transplant with valvulopathy
- Use amoxicillin before qualifying dental procedures; alternatives for allergy per guidance
- Routine prophylaxis is not recommended for most GI/GU procedures
Complications
- Heart failure: Acute valvular regurgitation is the most common indication for surgery
- Emboli: Stroke, splenic infarct, renal infarct, limb ischemia, septic pulmonary emboli in right-sided IE
- Perivalvular abscess: Conduction block and persistent infection
- Immune phenomena: Glomerulonephritis, Osler nodes, Roth spots
- Mycotic aneurysm: Infected arterial aneurysm with rupture risk
USMLE Step 2 CK Exam Tips
- 1Fever + new murmur + positive blood cultures = endocarditis until proven otherwise
- 2Get three sets of blood cultures before antibiotics if the patient is stable
- 3TEE is best for prosthetic valve endocarditis or suspected abscess
- 4S aureus bacteremia requires evaluation for endocarditis, especially persistent bacteremia
- 5Right-sided IE in injection drug use causes septic pulmonary emboli
- 6New AV block in endocarditis = perivalvular abscess
- 7Dental prophylaxis is only for highest-risk cardiac lesions, not every murmur
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