Cardiovascular · PANCE / PANRE

Infective Endocarditis (IE)

Microbial infection of the endocardium or valve — diagnosed by modified Duke criteria; treated with prolonged IV antibiotics ± surgery.

Also known as: IE, endocarditis, bacterial endocarditis, SBE, ABE

Overview

Infection of the endocardial surface of the heart, most commonly involving heart valves, characterized by vegetations composed of platelets, fibrin, microorganisms, and inflammatory cells.

Epidemiology

Annual incidence 3-10 per 100,000. Rising in older adults with degenerative valve disease and prosthetic devices; injection drug use is a leading driver of right-sided IE in younger patients.

🔒 Free preview limit reached

Keep reading — start your free trial

You've read your 2 free diagnosis previews. Create your free account to unlock the full Infective Endocarditis (IE) outline — plus all 514 diagnoses, 3,500+ board-style questions, flashcards, and an AI tutor. Your 7-day free trial includes everything, and there's no credit card required.

Start your 7-day free trial → Sign in

Free to start · No credit card · Cancel anytime

Risk factors

Prosthetic heart valve or prior infective endocarditis
Congenital heart disease (especially cyanotic)
Injection drug use (right-sided IE — tricuspid valve)
Hemodialysis, indwelling intravascular catheters, pacemaker/ICD leads
Poor dentition and recent dental procedures (oral streptococci)
Acquired valve disease (rheumatic, degenerative, MVP with MR)
Immunosuppression, diabetes

Pathophysiology

Endothelial injury exposes subendothelial matrix; sterile platelet-fibrin thrombus forms (nonbacterial thrombotic endocarditis). Transient bacteremia seeds this nidus, producing a vegetation that grows and embolizes, destroys leaflets (perforation, regurgitation), invades adjacent tissue (abscess, conduction block), or seeds distal organs.

Clinical presentation

Symptoms

Fever (most common — present in >90%), chills, night sweats, malaise, weight loss
Constitutional symptoms over weeks (subacute) or fulminant sepsis (acute)
New or worsening dyspnea from valve destruction and heart failure
Focal neurologic deficits (septic embolic stroke), back pain (vertebral osteomyelitis), flank pain (renal infarct)
Right-sided IE in IDU: pleuritic chest pain, cough, hemoptysis from septic pulmonary emboli

Signs / physical exam

New regurgitant murmur (especially MR or AR)
Janeway lesions (painless erythematous palms/soles — embolic)
Osler nodes (painful nodules on finger pads — immune complex)
Splinter hemorrhages, Roth spots (retinal hemorrhages with pale centers)
Splenomegaly, petechiae
Signs of complications: stroke, heart failure, AV block (perivalvular abscess)

Classic findings

FROM JANE — Fever, Roth spots, Osler nodes, Murmur, Janeway lesions, Anemia, Nail-bed splinters, Embolic phenomena.

Differential diagnosis

Nonbacterial thrombotic endocarditis (marantic) — Sterile vegetations in advanced malignancy or chronic illness; embolic events with negative cultures
Libman-Sacks endocarditis (SLE) — Verrucous sterile lesions on either side of valve leaflets; positive ANA / anti-dsDNA
Atrial myxoma — Embolic events and constitutional symptoms; mobile LA mass on echo without bacteremia
Rheumatic carditis — Following strep pharyngitis; multiple Jones criteria; rising ASO
Catheter-related bacteremia without IE — Persistent positive cultures but no vegetation; resolves with line removal
Septic pulmonary emboli of other source — May mimic right-sided IE; identify primary site and rule out tricuspid vegetation

Diagnostic workup

Diagnostic criteria

Modified Duke criteria — Definite IE: 2 major OR 1 major + 3 minor OR 5 minor. Major: typical organism in 2 separate blood cultures (S. viridans, S. gallolyticus/bovis, HACEK, S. aureus, community Enterococcus without primary source) OR persistent bacteremia OR echocardiographic evidence (vegetation, abscess, new dehiscence) OR new regurgitation. Minor: predisposition, fever ≥38°C, vascular phenomena, immunologic phenomena, microbiologic evidence not meeting major.

Labs

≥3 blood cultures from separate venipuncture sites at least 1 hour apart BEFORE antibiotics
CBC (anemia, leukocytosis), ESR/CRP elevated
UA (microscopic hematuria, proteinuria — embolic glomerulonephritis)
BMP, LFTs, rheumatoid factor (Duke minor criterion)
HIV testing in IDU and high-risk populations

Imaging

Transthoracic echo — initial; sensitivity ~70% for native valve, lower for prosthetic
Transesophageal echo — sensitivity >90%; perform if TTE negative but high suspicion, prosthetic valve, or to assess for abscess
ECG: new AV block suggests perivalvular abscess at aortic root
CT chest/abdomen/pelvis or PET-CT for embolic foci, splenic/renal infarcts, mycotic aneurysms
Brain MRI if neurologic symptoms

Diagnostic algorithm

Modified Duke Criterion	Type	Definition
Typical organism × 2 cultures	Major	S. viridans, S. gallolyticus, HACEK, S. aureus, community Enterococcus
Persistent bacteremia	Major	≥2 positive cultures >12 h apart, or majority of 3+ cultures positive
Echo evidence	Major	Vegetation, abscess, or new prosthetic valve dehiscence
New regurgitation murmur	Major	Documented new valvular regurgitation
Predisposition	Minor	Predisposing heart condition or IV drug use
Fever ≥38°C	Minor
Vascular phenomena	Minor	Arterial emboli, septic pulmonary infarcts, mycotic aneurysm, ICH, conjunctival hemorrhage, Janeway lesions
Immunologic phenomena	Minor	GN, Osler nodes, Roth spots, RF positivity
Microbiologic evidence	Minor	Positive cultures not meeting major criterion

Modified Duke criteria for infective endocarditis (Definite: 2 major OR 1 major + 3 minor OR 5 minor).

Treatment

First-line

Empiric therapy AFTER cultures drawn — native valve acute: vancomycin (target trough 15-20 mcg/mL) + ceftriaxone 2 g IV q24h
Prosthetic valve (within 12 months): vancomycin + gentamicin + rifampin
Streptococcal IE (penicillin-susceptible): penicillin G 12-18 million units/day IV or ceftriaxone 2 g IV daily × 4 weeks
S. aureus native valve: nafcillin or oxacillin 2 g IV q4h × 6 weeks (MSSA); vancomycin or daptomycin (MRSA)
Enterococcus: ampicillin + ceftriaxone OR ampicillin + gentamicin × 4-6 weeks
HACEK organisms: ceftriaxone × 4 weeks
Duration typically 4-6 weeks IV from first negative culture

Second-line / adjunct

Surgical valve repair/replacement — Class I for heart failure from valve dysfunction, perivalvular abscess, heart block, persistent bacteremia >5-7 days on appropriate antibiotics, large mobile vegetation >10 mm with embolic event, fungal IE, or prosthetic valve dehiscence
Lifelong removal of injection drug paraphernalia, addiction counseling
Endocarditis prophylaxis for future high-risk procedures (dental work) — amoxicillin 2 g PO 30-60 min pre-procedure; if penicillin-allergic use cephalexin 2 g, azithromycin/clarithromycin 500 mg, or doxycycline 100 mg (clindamycin is NO LONGER recommended per 2021 AHA update)

Complications

Heart failure from valve destruction (leading cause of mortality)
Septic embolization: stroke, splenic/renal infarct, septic pulmonary emboli
Perivalvular abscess and conduction block (especially aortic)
Mycotic aneurysm (intracranial, peripheral)
Acute kidney injury (immune-complex glomerulonephritis, antibiotic toxicity)
Death — overall mortality 15-30%

PANCE pearls

Always draw at least 3 separate blood cultures BEFORE antibiotics unless septic shock dictates otherwise.
New AV block in a febrile patient with IE strongly suggests aortic root abscess — get TEE.
S. gallolyticus (formerly S. bovis) endocarditis is associated with colorectal cancer — colonoscopy is required.
Right-sided endocarditis in an IDU classically presents with septic pulmonary emboli; tricuspid is the most common valve.
Endocarditis prophylaxis is only indicated for HIGH-RISK cardiac conditions undergoing high-risk procedures, not routine MVP or bicuspid valve.

References

AHA 2015 — Infective Endocarditis in Adults: Diagnosis, Antimicrobial Therapy, and Management of Complications (Baddour et al., Circulation 2015)
ESC 2023 — 2023 ESC Guidelines for the Management of Endocarditis (Delgado et al., Eur Heart J 2023)
Duke Criteria — Modified Duke Criteria for Infective Endocarditis (Li et al., Clin Infect Dis 2000)
AHA 2007 — Prevention of Infective Endocarditis (Wilson et al., Circulation 2007)

Practice Cardiovascular questions on FirstPassPA

Turn this outline into retention. 3,500+ board-style questions with an AI tutor that explains every answer — free to start, no card required.

Start studying free → Browse all 514 diagnoses

Educational use only. This outline is a study aid for PA students and is not medical advice or a substitute for clinical judgment. FirstPassPA is an independent study tool and is not affiliated with, endorsed by, or sponsored by NCCPA. PANCE® and PANRE® are registered trademarks of the National Commission on Certification of Physician Assistants.