Rapid Review·Cardiovascular
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PATHOLOGY
T2High yieldInfective Endocarditis
FA P318
Videos
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Focus on
The vegetations that seed the bloodstream, the peripheral signs they throw, and how the diagnosis is formally made.
Key takeaways
What it is and where it sits
Infective endocarditis
infection of the endocardial surface, typically involving one or more valves. Bacteria far outnumber fungi. Mitral is the most common, then aortic. Tricuspid involvement is associated with injection drug use (don't "tri" drugs).Pathogenesis, in order
damaged valve endothelium exposes the subendothelium, platelets and fibrin stick to it as a sterile vegetation, bacteria colonise the vegetation, and the growing vegetation of platelets, fibrin, and microbes destroys the valve (regurgitation) and throws septic emboli, systemic in left-sided and pulmonary in right-sided disease.Presents with fever, the most common finding, plus a new murmur
fever of unknown origin with a new murmur is endocarditis until proven otherwise. The rest is vascular and immunologic phenomena.| Vascular phenomena (embolic) | Immunologic phenomena (immune complex) |
|---|---|
| Septic embolism | Glomerulonephritis |
| Petechiae | Osler nodes: painful ("Ouchy"), raised, violaceous, on finger and toe pads. See the Osler node |
| Splinter hemorrhages, linear, in the nail bed. See the splinter hemorrhages | Roth spots: Retinal hemorrhages with pale centres. See the Roth spot |
| Janeway lesions: painless, flat, erythematous, on palms and soles ("Just a bump") |
Which organism
| Feature | Acute | Subacute |
|---|---|---|
| Organism | S aureus, high virulence | Viridans streptococci, low virulence |
| Valve | Previously NORMAL | Congenitally abnormal or already diseased |
| Vegetations | Large, destructive | Smaller |
| Onset | Rapid | Gradual |
| Setting | Bacteremia, injection drug use | After dental procedures |
| Association | Organism |
|---|---|
| Prosthetic valves | S epidermidis |
| GI or GU procedures | Enterococcus |
| Colon cancer | S gallolyticus (bovis) |
| Gram-negative | HACEK: Haemophilus, Aggregatibacter, Cardiobacterium, Eikenella, Kingella |
| Culture-negative | Coxiella, Bartonella |
| Injection drug use | S aureus, Pseudomonas, Candida |
Making the diagnosis
The workup
multiple blood cultures plus echocardiography. Draw blood cultures BEFORE starting antibiotics. Empiric therapy is vancomycin, with or without gentamicin.Definitive diagnosis
2 major, or 1 major plus 3 minor, or 5 minor criteria.The two MAJOR criteria
- Sustained bacteremia with a TYPICAL organism from 2 or more separate blood cultures: viridans streptococci, S aureus, S gallolyticus (bovis), HACEK organisms, enterococci.
- Endocardial involvement on echocardiography: a vegetation, abscess, or NEW valvular regurgitation, i.e. a new murmur.
The MINOR criteria, which is where the peripheral signs feed in
- Predisposing heart lesion or injection drug use
- Fever above 38 °C
- Vascular phenomena: Janeway lesions, septic or arterial emboli, mycotic aneurysm
- Immunologic phenomena: Osler nodes, Roth spots, glomerulonephritis, rheumatoid factor
- Microbiologic evidence not meeting a major criterion
TEE beats TTE
TEE is more sensitive than TTE for detecting vegetations, so a negative TTE does not exclude endocarditis.| Category | Criteria |
|---|---|
| Major (need 2) | Sustained bacteremia with a typical organism from 2+ cultures; echocardiographic vegetation, abscess, or new regurgitation |
| Minor (need 5 alone) | Predisposing lesion or IV drug use; fever above 38 °C; vascular phenomena; immunologic phenomena; microbiologic evidence falling short of major |
Nonbacterial thrombotic endocarditis
Marantic endocarditis
rare and noninfective. Sterile, platelet-rich thrombi on the mitral or aortic valve that dislodge easily. Associated with the hypercoagulable state of advanced malignancy, especially pancreatic adenocarcinoma, or with SLE, where it is called Libman-Sacks endocarditis. Usually asymptomatic until it embolizes.| Feature | Infective | Nonbacterial thrombotic (marantic) |
|---|---|---|
| Vegetations | Large, floppy, destructive, causing regurgitation | Small, verrucous, sterile, on both sides of the valve |
| Composition | Platelets, fibrin, microbes | Platelet-rich sterile thrombi |
| Setting | Bacteremia | Malignancy (pancreatic adenocarcinoma), SLE (Libman-Sacks) |
| Symptoms | Fever, new murmur | Asymptomatic until embolism |
Two separate cultures grow viridans streptococci and the echo shows a mitral vegetation. How many minor criteria do you still need?
None. Those are two major Duke criteria, which is definitive endocarditis on its own.
How it's tested
Osler nodes are painful and immunologic while Janeway lesions are painless and embolic, and that pairing is asked directly, with "Osler is Ouchy" as the hook. Culture-negative endocarditis points to Coxiella or Bartonella. The highest-value association is that Streptococcus gallolyticus bacteremia obligates a colonoscopy, because of the colon cancer link, so the answer to "next step" is not an antibiotic.
Two separate blood cultures growing viridans streptococci plus an echocardiogram showing a mitral valve vegetation satisfy two MAJOR Duke criteria, which is definitive infective endocarditis with no minor criteria needed. The other reliably tested points are procedural rather than diagnostic: cultures come before antibiotics, and TEE is more sensitive than TTE, so a negative transthoracic study in a convincing case means escalate the imaging rather than abandon the diagnosis.
Go deeper
First Aid 2026 — CV/Pathology (p.318) · B&B — Infective endocarditis; endocarditis diagnosis · Mehlman — HY Cardio (acute vs subacute, marantic vegetations, Duke major vs minor, TEE vs TTE)
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