• Introduction(click on picture to enlarge)
  • S. aureus: most common cause of acute bacterial endocarditis associated with prosthetic/native valves 
• Endocarditis-definition:"Infective endocarditis is defined as the  microbial infection of a platelet-fibrin vegetation on the endothelial surface of the heart"-
  • from:"Infective Endocarditis", Zurawski, C.A. and Rimland, D., in Medicine for the Practicing Physician, Hurst, J.W., Fourth edition, Appleton & Lange, Stamford, Connecticut, p. 322,1996.
• Staphylococcal endocarditis: Clinical presentation:
  • Usually non-specific findings at presentation

  • Nonspecific findings: infective endocarditis

    Finding	Frequency
    Fever	80-90%
    Chills/weakness	38%-40%
    Sweats	24%
    Weight loss/anorexia	25%
    Malaise	25%

  • Acute, febrile illness {usually < a few weeks' duration}
  • Skin lesions-20%; stroke-18% (secondary to embolism)
  • Musculoskeletal
  •  Complications which develop typically prior to medical attention:
    •  meningitis
    •  brain/visceral abscess
    •  heart failure-- secondary to failure of valve function
      • dyspnea -36%
      • cough- 24%
    • myocardial abscess
    • pericarditis (purulent)

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• Valvular involvement:
  • non-IV drug users: mitral & aortic valves
  • IV drug users: tricuspid valve

   

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• Pathogenesis
  • Predisposing  hemodynamic factors
    1.  turbulent blood flow (caused by high-velocity jet stream)
    2.  flow direction: high-to low pressure cardiac chamber
    3.  high-pressure gradient secondary to narrow opening between chambers
       •  infective endocarditis lesions  form on the lower-pressure cardiac chamber valve surface, e.g.:
         •  ventricular surface of abnormal aortic valve
         •  atrial surface of abnormal mitral valve
  • Other lesion locations -- satellite lesions where bloodstream impacts  the endocardium
  • Sterile vegetations--  nonbacterial thrombotic endocarditis
    • Deposition of platelets & fibrin at damaged endothelial sites

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  • Infected vegetations
    • Bacterial deposition during bacteremia onto sterile vegetation
    • Virulence considerations:- not all bacteremia causes infective endocarditis,e.g.:
      •  E . coli, common bacteremia cause:  poor adherence to endothelial sites --® rarely causes endocarditis
      •  Streptococcus viridans: typically affects only damaged valves
      •  Staphylococcus aureus: highly virulent, may affect normal valves
    •  Infected vegetations enlarge with additional platelet & fibrin deposition that   isolates bacteria from host defense mechanisms {polymorphonuclear leukocytes & complement)
      • Consequence: prolonged bacteriocidal antibiotic use is required for cure {surgical treatment may be required for cure--especially if infection is due to grand-negative bacilli or fungi or if prosthetic valves are involved.

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  • Consequence of persistent bacteremia:
    • Humoral & cellular immune system stimulation
      • increased immunoglobulin expression-causing increased immune complex formation & nonspecific hypergammaglobulinemia
    • Immune complex deposition on renal glomerular basement membrane:
      •  glomerulonephritis,
      •  renal failure

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• Clinical manifestations (subjective)
  •  Risk groups (noting that < 50% of patients with infective endocarditis have valvular disease  and up to 25% of occurrences are nosocomial)
    •  Patients with underlying cardiac disease
      •  Special attention: rheumatic or congenital heart disease   (including (a) mitral valve prolapse & (b) asymmetric septal hypertrophy
    •  Patients with a history of IV drug use
    •  Presence of  prosthetic valves implants
    •  Recent invasive procedures/hospitalizations during which intravenous catheters were used
• Clinical manifestations (objective)
  •  Physical Examination
    • Fever & heart murmur: most common abnormal finding physical examination: frequency = 80%
    • Embolic consequences {brain, renal, spleen}; skin presentations {petechiae, splinter hemorrhages Osler's nodes (indicative of systemic embolization, painful, tender, erythematous nodules on the extremities), Janeway lesions (flat, irregular, nontender erythematous spots < 5 mm in diameter on the palms and soles)}-frequency <50%
      •   Less common manifestations
        • splenomegaly 20%-30% 
        • septic complications {pneumonia or meningitis, 20%}
        • mycotic aneurysms 20%
        • renal failure 10%-20%
        • clubbing 10%-20%
        • Roth's spots (fundal hemorrhages with whitish centers {may also be seen in other conditions, e.g. leukemia & anemia}), retinal lesions 5-10%

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  •  Laboratory Results: Typically abnormal

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• Diagnosis:
  • Suggestive  findings--
    • Unexplained fever in patient with known valvular/congenital heart disease {fever is resultant endocarditis can occur without evidence of valvular  or congenital disease}
    •  heart murmur & conjunctival hemorrhage
    •  subungual (beneath a nail) petechiae {small, pinpoint, non-raised, perfectly round, purplish red spot, due to intradermal or submucosal hemorrhage}
    •  peripheral purpuric lesions
  • Differential Diagnosis:
    •  bacteremia or fungemia {without endocarditis}
    •  thrombotic, noninfective endocarditis
    •  atrial myxoma
    •  septic emboli (noncardiac source)
  • Confirmatory findings--
    •  positive blood cultures (multiple: three sets a blood cultures identify >99% of cases)
    •  valvular vegetation observed by echocardiography
      • Echocardiography indicates:
        • which valves are involved
        • extent of valvular dysfunction
        • left ventricular function
        • present/absence of myocardial abscess.

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• * Quincke's pulses: capillary pulsations seen in a nail beds with gentle compression of the nail {capillary bed will alternately blanche and flush};

• *Water-hammer pulses: arterial pulse tendency to "slap" and fall away rapidly-indicative of aortic valve disease  (regurgitation), retrograde flow from the aorta into the left ventricle

• Other signs: 

  • double Duroziez' murmur = systolic murmur in the femoral artery  heard distal to finger pressure on the artery and the diastolic murmur proximal to finger pressure

  •  Corrigan's sign = large carotid neck pulsations

  •  de Musset's sign = head nodding resulting from the large stroke volume ballistic force

  • Traube's sign: sharp sound heard over the femoral pulse.

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• Primary Reference: "Staphylococcal Infections", Deresiewicz, R.L., and Parsonnet, J., in Harrison's Principles of Internal Medicines, (Fauci, A., et al., eds) 14th edition, McGraw-Hill, 1998.
• Primary Reference:"Infective Endocarditis", Zurawski, C.A. and Rimland, D., in Medicine for the Practicing Physician, Hurst, J.W., Fourth edition, Appleton & Lange, Stamford, Connecticut, pp 322-325,1996.
• "Infectious Diseases", Bloch, K. C. in Pathophysiology of Disease, An Introduction to  Clinical Medicine, (McPhee, S. J., Lingappa, V.R., Ganong, W.F., and Lange, J.D., eds), 3rd edition, Lange Medical Books, McGraw-Hill, pp. 59-61, 2000.