Rheumatic Carditis

Rheumatic Carditis

·        This includes rheumatic fever (acute rheumatic heart disease (ARHD), or “acute rheumatic carditis”) and chronic rheumatic heart disease. Chronic rheumatic valvulitis is the most common cause of mitral valve stenosis.

·        There may be some genetic susceptibility involved.

A. Etiology and pathogenesis

1.     Group A β-hemolytic Streptococci cause pharyngitis. (These have a clear halo in culture due to Hb lysis.)

2.     There’s a hypersensitivity reaction to the bacteria. Either way there’s immune-mediated injury and host inflammation.
a) Antibodies against bacterial Ag mistakenly cross-react with human tissues. So an Ab
    for bacterial cell wall M-proteins may mistakenly react cardiac myosin protein.
    OR
b) The infection evokes an autoimmune response against self-Ag.

3.     This results in rheumatic fever.
-  An acute, multisystem, immunologically-mediated disease inflammatory disease that   
   affects the heart (this is ARHD), joints, CNS, skin, etc. Most patients survive this
   without complications.

- Rheumatic fever occurs in 3% of children who have strep throat. There’s a low
  incidence in the U.S. It’s more common in developing countries where acute medical care,
  pediatricians, and antibiotics are less available.
 

B. Rheumatic fever—ARHD

ARHD is really sterile pancarditis. (Remember this—it was repeated a few times.)
-  “Sterile” because there are no bacteria in the lesions—just the body’s hypersensitivity
    response and self-inflicted injury (due to immune complexes with self-Ag).
-  “Pancarditis” because all 3 layers of the heart are affected.
The pathognomic (signature) lesions of AHRD are Aschoff bodies, which are easily seen in the myocardium. 

 1.      Myocarditis:

a)  Myocytes have undergone fibrinoid necrosis due to
     injury from immune complexes.

b)  They’re replaced by Aschoff bodies, which are
     collections of:  
      - Anitschkow cells (activated macrophages; pale),
      - lymphocytes (chronic inflammation; the blue dots),
      - interstitial edema (pale areas),
      - multinucleated giant cells.

c)  The necrosis eventually heals via fibrosis.

      2.  Pericarditis:

a)  Fibrinous exudates collect in the pericardial space. They eventually undergo

     organization (replacement by fibrous connective tissue).

b)  Bread-and-butter pericarditis: adhesions eventually form between the parietal and   
     visceral pleura. The “shaggy” deposition of fibrin on the heart surface looks like a piece
     of buttered bread dropped on the floor.

      3. Endocarditis:

a)  Small depositions of fibrin on the valves causes irregularities of leaflets (especially on
     the left-sided valves). These are termed vegetations (description of this under “Infective
     Endocarditis”) or verrucae (warty-looking).

b)  The resulting disruption of blood flow leads to formation of small thrombi.

c)  Aschoff bodies also develop within the thin leaflets, which causes erosion of the
     surrounding connective tissue, and more thrombus formation.

C. Rheumatic Fever—other symptoms

• Skin: rashes (erythema marginatum, erythema nodosum) and subcutaneous rheumatic nodules
• Basal ganglia: Sydenham chorea (gait and other motor issues)
• Joints: arthritis
  
   

D. Chronic Rheumatic Heart Disease (CRHD)

• Most patients survive rheumatic fever without complications. But those who have poor medical care and recurrent strep. pharyngitis infections may have reactivation of immune-mediated inflammation in adulthood.
• Repeated injury, inflammation, and healing results in:
  a)  “Fish mouth” or “button hole” valvular stenosis: repeated
       fibrous scarring of the leaflets causes stenosis (or less     
       commonly, regurgitation).
  b)  Short, thickened, fused chordae tendinae
  c)  Fusion of the cusp commissures and free edges of the leaflets
       (arrows in figure)
• The left-sided valves are most frequently affected. Right-sided valve disease is uncommon.

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