Inflammation Case Studies


CASE 5: Acute bacterial endocarditis


Clinical History:

A 35-year-old man had a history of intravenous drug use. Over several days' time, he developed a high fever, then dyspnea. On physical examination, his temperature was 39.4 C (103 F), and a heart murmur was heard. Needle tracks and a red, tender, fluctuant area were noted near the left antecubital fossa. A blood culture grew Staphylococcus aureus. Despite antibiotic therapy, he died three days later. The aortic valve is shown in image 5.1. Sectioning of the myocardium revealed multiple small soft yellow foci (image 5.2). The epicardium showed a shaggy appearance (image 5.3).
  1. What is the appearance of the aortic valve?

    2. At autopsy, the aortic valve showed extensive necrosis with vegetations composed of yellowish-red, friable material.

  2. Note the dark purple foci in this section of myocardium just by viewing the image without the microscope. Under the microscope, describe what you see in these foci.

    3. These foci are small abscesses filled with neutrophils. The myocardium and adjacent epicardial fat show suppurative necrosis.

  3. How do these foci in the myocardium relate to the lesions on the aortic valve?

    4. The vegetations on the aortic valve break off and embolize. Some may go out the coronary arteries to myocardium. These are "septic" emboli because they contain bacteria.

  4. Bacteria are being phagocytozed because what agents are acting as opsonins?

    5. Immunoglobulin (IgG) and complement C3b.

  5. What is the diagnosis? What is the pathogenesis of this process?

    6. This is acute bacterial endocarditis with septic emboli and myocardial and epicardial abscesses. Most IV drug users do not use sterile needles, so are at risk for infection (his antecubital lesion was probably an abscess at the site of injection).

  6. What is the process involving the epicardium (image 5.3)?

    7. The inflammation has led to exudation of fibrin, which has organized into a fibrinous pericarditis. The pink strands of fibrin gave the grossly shaggy appearance.