Bacterial Endocarditis



Patient Story





A 25-year-old man presented to the office because he had been feeling tired and feverish for several weeks. He admitted to injecting heroin regularly in the last 2 months. On examination, he was febrile and had a heart murmur of which he was previously unaware. His fingernails showed splinter hemorrhages (Figure 50-1). His funduscopic examination revealed Roth spots (Figures 50-2 and 50-3). An echocardiogram demonstrated vegetation on the tricuspid valve. He was hospitalized and treated empirically for bacterial endocarditis. After his blood cultures returned Staphylococcus aureus, his regimen was adjusted based on sensitivities and continued for 6 weeks.







Figure 50-1



Splinter hemorrhages appearing as red linear streaks under the nail plate and within the nail bed. Although endocarditis can cause this, splinter hemorrhages are more commonly seen in psoriasis and trauma. (Courtesy of Richard P. Usatine, MD.)








Figure 50-2



Roth spots that are retinal hemorrhages with white centers seen in bacterial endocarditis. These can also be seen in leukemia and diabetes. (Courtesy of Paul D. Comeau.)








Figure 50-3



Close-up of a Roth spot, which is actually a cotton-wool spot surrounded by hemorrhage. The cotton-wool comes from ischemic bursting of axons and the hemorrhage comes from ischemic bursting of an arteriole. (Courtesy of Paul D. Comeau.)







Introduction





Bacterial endocarditis is a serious infection seen most commonly in patients with prosthetic valves; injection drug users; patients with HIV, especially those who use intravenous (IV) drugs; and patients who are immunosuppressed. Diagnosis is made based on Duke Criteria. Treatment is IV antibiotics. Mortality, despite treatment, is 26% to 37%.






Epidemiology






  • 5.0 to 7.9 cases per 100,000 patient-years.1

    • Historically more common in men; however, the incidence in women is increasing. Men and women 8.6 to 12.7 and 1.4 to 6.7 cases per 100,000 person-years, respectively.1
    • Average age has increased from 46.5 years (1980-1984) to 70 years (2001-2006).1
    • Incidence in IV drug users is 3 per 1000 person-years or 1% to 5% per year.2
    • Incidence in HIV-positive IV drug users is 13.8 per 1000 person-years.2

  • Seen in immunosuppressed patients with central venous catheters or hemodialysis patients.

    • Fifty percent healthcare-associated, 43% community-acquired, and 7.5% nosocomial.1
    • Mortality ranges from 16% to 37%.3

  • Prosthetic valve endocarditis makes up 10% to 15% of endocarditis cases.4

    • Incidence of 0.1% to 2.3% person-year.4
    • Can occur early (2 months after surgery) or late.






Etiology and Pathophysiology






  • Endothelium is injured by mechanical or inflammatory processes.
  • Microbes adhere to compromised endothelium during transient bacteremia.
  • Common organisms include S. aureus (IV drug users, nosocomial infections, prosthetic valve patients), Streptococcus bovis (elderly patients), enterococci (nosocomial infections), and Staphylococcus epidermis (early infection in prosthetic valve patients).
  • Blood contacts subendothelial factors, which promotes coagulation.
  • Pathogens bind and activate monocyte, cytokine, and tissue factor production, enlarging the vegetations on the heart valves.
  • The vegetations enlarge and damage the heart valves (Figure 50-4). This process can lead to death if not treated adequately in time.
  • Septic emboli can occur, most commonly in the brain, spleen, or kidney.4







Figure 50-4



Pathology specimen of a patient who died of bacterial endocarditis. Bacterial growth can be seen on the three cusps of this heart valve. (Courtesy of Larry Fowler, MD.)







Risk Factors






  • Prosthetic valve.
  • Injection drug use.
  • HIV infection.
  • Immunodeficiency.






Diagnosis






  • Duke criteria use a combination of history, physical examination, laboratory, and echocardiogram findings, and have a sensitivity of approximately 80% across several studies.5
  • Diagnosis is considered definite when patients have two major, one major and three minor, or five minor criteria.5
  • Diagnosis is considered possible with one major and one minor or three minor criteria.5
  • Major criteria include:5
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Jun 4, 2016 | Posted by in GENERAL & FAMILY MEDICINE | Comments Off on Bacterial Endocarditis

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