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Infective Endocarditis (Ref. Hari. 18th ed., pg -1052)

Definition – The proliferation of micro organisms on the endothelium of the heart.


Vegetation – mass of platelets, fibrin, microcolonies of micro organism and scanty inflammatory cells. They are bulky, friable, irregular, and multiple, occur along the cusp.



  1. Acute = 50% of all endocarditis occurs on normal valves. It follows an acute course and presents with acute heart failure
  2. Sub Acute =  Endocarditis on abnormal valves tends to run a subacute course.

Predisposing cardiac lesions: aortic or mitral valve disease; tricuspid valves in IV drug users; coarctation; patent ductus arteriosus; VSD; prosthetic valves. Endocarditis of prosthetic valves may be early (acquired at the time of surgery, poor prognosis) or 'late' (acquired hematogenously).

NB: Septum secundum ASD is the least important cause of endocarditis Q (AIPG 12)


Causes Bacteria:


  1. Any cause of bacteriemia exposes valves to the risk of bacterial colonization (dentistry; UTI; urinary catheterization; cystoscopy; respiratory infection; endoscopy colon cancer; gall bladder disease; skin disease; IV cannulation; surgery; abortion; fractures). Q
  1. Staph aureus is the most common cause.
  2. Strep viridans is also a common cause (Note: previously it use to be the most common cause)
  3. Others: enterococci; Staph aureus or epidermidis; and microaerophilic streptococci.
  4. Rarely: HACEK group of Gram negative bacteria (Haemophilus-Actinobacillus-Cardiobacterium-Eikenella- Kingella) Q (AIIMS May 2012)
  5. Coxiella burnetii, Chlamydia.
  6. Fungi: Candida, Aspergillus, and Histoplasma.
  7. Other causes: SLE (Libman-Sacks endocarditis) Q malignancy. 

Extra Edge: HACEK – They are fastidious, slowly growing, gram negative and CO2 for growth (UPSC 2013)
(Ref. Hari. 18th ed., pg - 1233)


Etiology –

  1. Native valve endocarditis:  Mitral valve is the most common valve involve.

Causative organism

  1. Most common cause in native valve = Staph aureus
  2. Streptococci viridans
  3. Streptococcus bovis (Polyp, colon tumors)
  4. Enterococci
  5. HACEK organisms (Hemophilus, Actinobacillus, Cardiobacterium, Eikenella, Kingella) 

Important Points: Hemophilus influenzae is not a part of HACEK group.  H. aphrophilus and H. parainfluenzae are the most common Haemophilus species isolated from case of HACEK endocarditis. (AIIMS May 2010) 

  1. Prosthetic valve endocarditis (Most common valve involved is aortic valve)
    1. With in 2 months of surgery = staph aures (OK)
    2. After 2 months of surgery = coagulase negative staphylococci (CoNS). (Ref. Hari. 18th ed. Pg - 1052)
      Note: A patient has prosthetic valve replacement and he develops endocarditis 8 months later. Organism responsible is CoNS
  2. Endocarditis in I.V. drug abusers (Most common valve involve is = tricuspid)


  1. Commonest– Staph aureus
  2. Pseudomonas aeruginosa
  3. Candida
  4. Polymicrobial infection is more common.
  5. Pseudomonas causes endocarditis in IV drug abuser. 

Extra Edge:

  1. Most common cause in native valve = Staph aures
  2. Most common cause in prosthetic valve = Coagulase negative staph aures
  3. Most common cause in IV drug abuser = Staph aures (AIIMS Nov 2010) 

Culture negative endocarditis

  1. Pyridoxal requiring streptococci (Abiotrophia)
  2. HACEK
  3. Bartonella
  4. Tropheryma whippelii
  5. Libmann sack endocarditis
  6. Marantic endocarditis

Note: Flat vegetations in pockets of valves are due to Libman sacks Endocarditis


Clinical features of endocarditis

  1. Fever, rigors, night sweats, malaise, weight loss, anaemia, splenomegaly Q, and clubbing Q.
  2. Cardiac lesions: Any new murmur, or a change in the nature of a pre-existing murmur.
  3. Vegetations may cause valve destruction, and severe regurgitation, or valve obstruction.
  4. An aortic root abscess causes prolongation of the P-R interval, and may lead to complete AV block.
  5. LVF is a common cause of death. 

Immune complex deposition:

  1. Vasculitis Q.
  2. Microscopic hematuria Q, is common in glomerulonephritis Q
  3. Acute renal failure may occur.
  4. Roth spots (boat-shaped retinal haemorrhage with pale centre; (LQ 2012)
  5. Splinter haemorrhages Q (on finger or toe nails);
  6. Osler's nodes Q (painful pulp infarcts in fingers or toes) 

Vascular phenomena:

  1. Emboli may cause abscesses Q.
  2. In right-sided endocarditis, pulmonary abscesses.
  3. Janeway lesions Q (painless palmar or plantar macules).

Complications of Endocarditis

  1. Heart failure      
  2. Embolic phenomena           
  3. conduction abnormality      
  4. CVA
  5. Meningitis        
  6. Mycotic aneurysm (Note: they are due to bacteria and not due to fungus!!!) (AIPG 10)
  7. VSD                 
  8. Perforation of aorta. 


  1. Blood cultures: 3 blood cultures sample should be taken
  2. Blood tests: Normochromic, normocytic anaemia, neutrophil leucocytosis, high ESR/CRP.
  3. Echocardiography Transthoracic Echo (TTE) may show vegetations, but only if >2mm.
    Transesophasial Echo (TEE) is more sensitive, and better for visualizing mitral lesions and possible development aortic root abscess.
  4. Diagnosis The Duke criteria for definitive diagnosis of endocarditis are given.

Table : The Duke Criteria for the Clinical Diagnosis of Infective Endocarditis

Major Criteria

1. Positive blood culture (LQ 2012)

2. Evidence of endocardial involvement   Positive echocardiogram (LQ 2012)

Minor Criteria

1. Predisposition: predisposing heart condition or injection drug use

2. Fever â38.0°C (100.4°F)

3. Vascular phenomena: major arterial emboli, septic pulmonary infarcts, mycotic aneurysm, intracranial hemorrhage,   conjunctival hemorrhages, Janeway lesions

4. Immunologic phenomena: glomerulonephritis, Osler's nodes, Roth's spots, rheumatoid factor

5. Microbiologic evidence: positive blood culture but not meeting major criterion as noted previously or serologic evidence of active infection with organism consistent with infective endocarditis


Criteria of How to diagnose: Definite infective endocarditis: 2 major or 1 major and 3 minor or all 5 minor criteria (if no major criterion is met).



  1. Antibiotics:
    1. Empirical therapy:
      1. Benzylpenicillin + gentamicin,              
      2. If acute, add flucloxacillin
    2. Definite therapy : If organism grows in blood culture.
      1. Enterococci: amoxicillin gentamicin.   
      2. Streptococci.' Benzylpenicillin for 2-4wks; then amoxicillin for 2wks.
      3. Staphylococci. flucloxacillin + gentamicin. 
      4. Coxiella: doxycycline indefinitely + co-trimoxazole, or rifamp­icin or ciprofloxacin.
  2. Consider surgery if: heart failure, valvular obstruction; repeated emboli; fungal endocarditis; persistent bacteriemia myocardial abscess; unstable infected prosthetic valve.

Prognosis 30% mortality with staphylococci; 14% with bowel organisms; 6% with sensitive streptococci



  1. Amoxicillin 2g orally 1h before dentistry. This suitable for those who have not received penicillin in the last month, including those with prosthetic valves (If penicillin allergic, clindamycin 600mg orally 1 hrs before surgery).  
  2. If past endocarditis, IV gentamicin and amoxicillin.

Risk of infective endocarditis in various lesion:

High Risk

Moderate Risk

Low Risk

Prosthetic heart valve

MVP + M.R.

ASD (LQ 2012)

Tetralogy of Fallot


MVP without MR




Coarctation of aorta






Mitral regurgitation




Tables 124–8 High-Risk Cardiac Lesions for Which Endocarditis Prophylaxis Is Advised before Dental Procedure


Prosthetic heart valves

Prior endocarditis

Unrepaired cyanotic congenital heart disease, including palliative shunts or conduits

Completely repaired congenital heart defects during the 6 months after repair

Incompletely repaired congenital heart disease with residual defects adjacent to prosthetic material

Valvulopathy developing after cardiac transplantation


Tables 124–7 Antibiotic Regimens for Prophylaxis of Endocarditis in Adults with High-Risk Cardiac Lesions


A. Standard oral regimen

1. Amoxicillin2 g PO 1 h before procedure

B. Inability to take oral medication

1. Ampicillin: 2 g IV or IM within 1 h before procedure

C. Penicillin allergy

1. Clarithromycin or azithromycin: 500 mg PO 1 h before procedure

2. Cephalexin: 2 g PO 1 h before procedure

3. Clindamycin: 600 mg PO 1 h before procedure

D. Penicillin allergy, inability to take oral medication

1. Cefazolin or ceftriaxone: 1 g IV or IM 30 min before procedure

2. Clindamycin: 600 mg IV or IM 1 h before procedure

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