1. The microscopic lesion characteristic
of Acute Rheumatic Fever shown in Figure
1 is an Aschoff body set in the interstitial
connective tissue for the heart. It is characterized by a center of
fibrinoid necrosis around which are disposed a scanty mononuclear infiltrate
with distinctive Anitschkow cells. The cells have vesicular nuclei with the
chromatin condensed in the center as a fine, wavy ribbon; descriptive names
include "caterpillar cells" or "owl eyed" cells, depending on the plane or
section. Similar lesions may be seen in other tissues.
As with many fibrinoid lesions, the
mechanism of injury is felt to the immunologic. The most popular theory is
that antigens on the streptococcus "mimic" endogenous cardiac antigens and
in the appropriate host the immune response to strep becomes an autoimmune
disease that can be exacerbated by future strep infections. This is in
contrast to Glomerulonephritis after strep infection which is thought to be
due to trapping of strep antigen/antibody complexes in the glomeruli and
subsequent activation of complement (i.e., the glomerulus is an innocent
bystander rather than a primary target of the antibody). Less clear is what
constitutes an appropriate host for ARF and why ARF only follows throat
infections and does not follow skin infections. The nephritis can be
associated with infection of either site. Note that ARF is the only collagen
vascular diseases based on similar "mimicries."
2. The fibrinous ("bread and butter")
pericarditis as shown in Figure 2 could certainly account for the friction rub. Other common
causes of pericarditis are adjacent myocardial infarct, pulmonary infarct,
pneumonia, or tumor as well as uremia.
3. Jones criteria based on sites of
involvement by ARF heart (pancarditis), joints, skin, brain (chorea).
4. The dentist fears
bacteremia from manipulation of teeth with organisms such as strep viridans
colonizing the damaged heart valves. Turbulent flow, endothelial injury, and
the formation of fibrin clot as a meshwork are presumed to be important in
the genesis and perpetuation of the valvular infection. Clinically, fever, a
murmur, sceptic emboli.
5.
Figure 3 shows mitral stenosis
with thickening of the valve and a "fish mouth" deformity.
6. With many types of prosthetic valves
the danger of infectious endocarditis persists and probably for similar
reasons - abnormal flow and foreign material as nidus for clotting. The
organisms may be more unusual (e.g., fungi).
7.
YES, but many patients present with the chronic
valvular disease and no history of ARF. Most of these are presumed to be due
to the same process. However, there is evidence that many cases of isolated
aortic valve stenosis may be due to a congenital malformation of the aortic
valve (bicuspid, etc) which then is injured with chronic wear and tear and
becomes calcified. Chronic rheumatic disease usually shows fused cusps or
leaflets whereas calcific aortic stenosis does not.
8. The incidence of ARF has decreased
markedly since about 1940. Due to antibiotic
therapy, changes in the strep organisms, host nutrition, routine throat
cultures, etc. It
remains a serious problem in developing countries. Death rate is U.S.A.
approximately 3.4
per 100,000.
