Infective endocarditis

This is due to microbial infection of a heart valve (native or prosthetic), the lining of a cardiac chamber or blood vessel, or a congenital anomaly (e.g. septal defect).

* Pre-exam preparation for medicine, HN Sarker

The types of endocarditis are:

1. Acute infective endocarditis
2. Subacute infective endocarditis
3. Postoperative infective endocarditis.

* Pre-exam preparation for medicine, HN Sarker

1. Streptococcus— Viridens group and enterococci.
2. Staphylococcus—Staphylococcus aureus and coagulase negative
3. Gram-negative bacilli—Haemophilus anaerobes
4. Others—Rickettsiae and fungi.

* Pre-exam preparation for medicine, HN Sarker

The peripheral stigmata of infective endocarditis are:

• Clubbing
• Splinter hemorrhage
• Osler’s nodes
• Janeway lesions
• Purpura
• Roth’s spots.

* Pre-exam preparation for medicine, HN Sarker

Figure: Clinical features which may be present in endocarditis

* Davidson’s Principles and Practice of Medicine, 22nd Edition Page: 627

Investigations

1. Blood culture
   • It is the crucial investigation because it may identify the infection and guide antibiotic therapy.
2. Echocardiography
   • For detecting and following the progress of vegetations, for assessing valve damage and for detecting abscess formation.
3. ESR: Elevation
4. CRP: Measurement of serum CRP is more reliable than the ESR in monitoring progress.
5. Hb% and PBF: Normocytic normochromic anaemia
6. CBC: Leucocytosis
7. Urinalysis:
   • Proteinuria may occur and microscopic haematuria is usually present.
8. ECG
   • Development of AV block (due to aortic root abscess formation) and occasionally infarction due to emboli.
9. Chest X-ray
   • Evidence of cardiac failure and cardiomegaly.

* Davidson’s Principles and Practice of Medicine, 22nd Edition Page: 627, 628

Diagnosis of infective endocarditis (modified Duke criteria)

Major criteria

• Positive blood culture
  • Typical organism from two cultures
  • Persistent positive blood cultures taken > 12 hrs apart
  • Three or more positive cultures taken over > 1 hr
• Endocardial involvement
  • Positive echocardiographic findings of vegetations
  • New valvular regurgitation

Minor criteria

• Predisposing valvular or cardiac abnormality
• Intravenous drug misuse
• Pyrexia ≥ 38°C
• Embolic phenomenon
• Vasculitic phenomenon
• Blood cultures suggestive: organism grown but not achieving major criteria
• Suggestive echocardiographic findings

Diagnosis

• Definite endocarditis = two major, or one major and three minor, or five minor
• Possible endocarditis = one major and one minor, or three minor

* Davidson’s Principles and Practice of Medicine, 22nd Edition Page: 627

• Acute—Flucloxacillin and gentamicin.
• Subacute or indolent—Benzyl penicillin and gentamicin. In those with penicillin allergy, a prosthetic valve or suspected methicillin-resistant Staph. aureus (MRSA)
• Infection—Triple therapy with vancomycin, gentamicin, and oral rifampicin.

* Pre-exam preparation for medicine, HN Sarker

Indications for cardiac surgery in infective endocarditis

• Heart failure due to valve damage
• Failure of antibiotic therapy (persistent/uncontrolled infection)
• Large vegetations on left-sided heart valves with evidence or ‘high risk’ of systemic emboli
• Abscess formation

N.B. Patients with prosthetic valve endocarditis or fungal endocarditis often require cardiac surgery.

* Davidson’s Principles and Practice of Medicine, 22nd Edition Page: 629