Infective Endocarditis: Duke Criteria, Echo Findings & Antibiotic Protocols
About this video
Below is your **complete, concise-but-exhaustive** NEET PG–ready reference for **Infective Endocarditis (IE)** following your preferred pattern.
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# **Infective Endocarditis (IE): Duke Criteria, Echo Findings & Antibiotic Protocols**
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# **1. Definition**
Infective endocarditis is an infection of the **endocardial surface of the heart**, typically involving heart valves, caused by **bacteria** or **fungi**, leading to vegetation formation, valvular destruction, and systemic embolization.
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# **2. Pathophysiology**
1. **Endothelial injury** → deposition of platelets & fibrin → **nonbacterial thrombotic endocarditis (NBTE)**.
2. **Bacteremia** (transient/persistent) → organisms adhere to NBTE → **vegetation formation**.
3. Vegetations protect microbes → high bacterial load, low immune clearance → **metastatic emboli**, immune complex deposits, valvular dysfunction leading to **heart failure**.
Common organisms:
* **Native valve**: *S. aureus*, Viridans streptococci, *Enterococcus*.
* **Prosthetic valve (early <1 yr)**: *S. aureus*, coagulase-negative staph.
* **IV drug users**: *S. aureus* (Tricuspid).
* **Culture-negative**: HACEK group, Coxiella, Bartonella, Brucella.
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# **3. Clinical Features**
### **Constitutional**
* Fever, chills, night sweats
* Weight loss, malaise
### **Cardiac**
* New or changing **murmur**
* **Heart failure** due to severe valvular regurgitation
* Conduction block (abscess)
### **Peripheral signs**
* **Janeway lesions** (painless palms/soles emboli)
* **Osler nodes** (painful immunologic nodules)
* **Roth spots** (retinal hemorrhages)
* **Splinter hemorrhages**
* **Petechiae**
### **Embolic manifestations**
* Stroke, splenic infarct, renal infarct, pulmonary emboli (right-sided IE)
### **Immune complex manifestations**
* GN (hematuria, proteinuria)
* Positive RF
* Low complement
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# **4. Modified Duke Criteria (Diagnosis)**
Diagnosis requires:
### **✔ Definite IE**
* 2 Major OR
* 1 Major + 3 Minor OR
* 5 Minor
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### **Major Criteria**
1. **Positive Blood Cultures**
* Typical organism (Viridans strep, S. aureus, HACEK) **from 2 separate cultures** OR
* Persistently positive cultures (2 drawn 12 hrs apart)
2. **Evidence of Endocardial Involvement**
* **Echo** showing:
* Vegetation
* Abscess
* New partial dehiscence of prosthetic valve
* **New valvular regurgitation**
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### **Minor Criteria**
* Predisposition: heart disease / IV drug use
* Fever ≥38°C
* Vascular phenomena: emboli, Janeway, septic pulmonary infarcts
* Immunological phenomena: Osler nodes, Roth spots, GN, RF+
* Microbiology not fulfilling major criteria
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# **5. Echocardiographic Findings**
### **Transthoracic Echo (TTE)**
* First-line
* Sensitivity ~60%
### **Transesophageal Echo (TEE)**
* GOLD STANDARD
* Sensitivity ~90–100%
* Mandatory if:
* Prosthetic valve
* Prior TTE negative but high suspicion
* Staph aureus bacteremia
* Poor acoustic window
### **Echo Findings in IE**
* **Vegetations**: oscillating intracardiac mass attached to valve
* **Regurgitation** (MR/AR/TR)
* **Abscess cavity** (perivalvular)
* **Perforation** of valve leaflet
* **Prosthetic valve dehiscence** (rocking motion)
* **Pseudoaneurysm**
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# **6. Investigations**
* Blood cultures × **3 sets** before antibiotics
* CBC: anemia, leukocytosis
* ESR/CRP elevated
* Renal function
* Urinalysis (microscopic hematuria)
* ECG: conduction block suggests abscess
* CT/MRI: embolic events
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# **7. Management (Complete Stepwise)**
## **1️⃣ Initial Measures**
* Take **3 sets of blood cultures BEFORE antibiotics**.
* Start **empiric IV antibiotics** if patient is sick or high suspicion.
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# **8. Empiric Antibiotic Therapy**
## **Native Valve IE**
* **Ceftriaxone + Vancomycin**
OR
* **Vancomycin + Gentamicin** (rarely now)
## **Prosthetic Valve IE**
* **Vancomycin + Gentamicin + Cefepime**
OR
* Add **Rifampicin** for staphylococcal prosthetic valve IE.
## **IV Drug User (Tricuspid)**
* **Vancomycin** (cover MRSA)
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# **9. Targeted Therapy (Organism-Specific)**
### **1. Viridans streptococci / S. bovis**
* **Ceftriaxone** IV 4 weeks
OR
* **Penicillin G** 4 weeks
* Add **gentamicin** for 2 weeks in severe infection.
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### **2. Staphylococcus aureus**
**MSSA**
* **Nafcillin/Oxacillin** 4–6 weeks
OR
* **Cefazolin** (if non-anaphylactic penicillin allergy)
**MRSA**
* **Vancomycin** 4–6 weeks
OR
* **Daptomycin**
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### **3. Enterococcus**
* **Ampicillin + Gentamicin**
OR
* **Ampicillin + Ceftriaxone** (preferred due to less nephrotoxicity)
Duration: **6 weeks**
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### **4. HACEK organisms**
* **Ceftriaxone** 4 weeks
OR
* **Ampicillin-sulbactam**
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### **5. Culture-Negative IE**
* Early (<1 yr): **Vancomycin + Gentamicin + Cefepime**
* Late: **Vancomycin + Ceftriaxone**
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# **10. Indications for Surgery (Very Important for NEET PG)**
### **Absolute indications**
* **Refractory heart failure** from valve dysfunction
* **Uncontrolled infection**, e.g.,
* Abscess
* Persistent bacteremia >72 hrs
* Fungal IE
### **Prevention of embolization**
* Large vegetation >10 mm with embolic events
* Vegetation >15 mm even without emboli
### **Prosthetic valve IE with dehiscence**
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# **11. Complications**
* Heart failure
* Septic emboli (stroke, splenic infarct)
* Mycotic aneurysm
* Perivalvular abscess
* Conduction block
* Renal failure (GN)
* Death
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# **12. Prophylaxis (AHA Guidelines)**
Indicated ONLY for high-risk patients:
* Prosthetic heart valves
* Previous IE
* Congenital cyanotic heart disease
* Cardiac transplant with valvulopathy
**Procedure requiring prophylaxis:** Dental work involving gingiva
**Drug:** **Amoxicillin 2 g PO** 30–60 mins before
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