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Rheumatic heart disease is the
result of cardiac involvement by rheumatic fever.
Rheumatic fever occurs equally
in both sexes and at all ages, but it is more common in children with
the peak incidence occuring between ages 5 and 15 years.
 -Etiology:
(click on the image)
The
exact etiology of rheumatic fever is still controversial.
The disease
occurs after a latent period of two to three weeks following an
infection with a group A beta-hemolytic streptococcus, typically a
pharyngitis.
Streptococci
are considered the cause of the pharyngitis, because of elevated titres
of antibodies to streptococcal antigens, such as streptolysin O,
hyaluronidase or streptokinase in the serum.
The more
severe the initial streptococcal infection, the greater the chance of
subsequent rheumatic fever.
Some
streptococcal antigens cross-react with cardiac antigen. This raises
the possibility of an autoimmune etiology.
There seems to be an
additional hereditary factor for susceptibility to rheumatic fever
after streptococcal infection.
-Clinical
diagnosis:
The clinical
diagnosis of rheumatic fever is made when two major or one major and two
minor criteria - Jones Criteria, are met.
If this diagnosis is supported
by evidence of a preceding streptoccocal infection, the probability of
rheumatic fever is high.
The major clinical
manifestations include - Carditis (murmur, cardiomegaly, pericarditis,
and congestive heart failure) ; Erythema marginatum ; Migratory large
joint polyarthritis ; Sydenham chorea ; Subcutaneous nodules.
The minor manifestations
include - a previous history of rheumatic fever ; arthralgia ; fever ;
certain laboratory tests indicative of an inflammatory process (Eg:
Elevated sedimentation rate, positive test for C-reactive protein,
leukocytosis) and electrocardiographic changes.
-Fate of the
patients with rheumatic fever:
-
Complete recovery
after an acute attack of rheumatic fever is possible.
-
Adhesive
pericarditis, which follows the fibrinous pericarditis of the
acute attack, almost never results in constrictive pericarditis.
- Most
significant late result of rheumatic fever is
scarring of the
heart
valve.
- There is
increased
susceptibility to the localization of infectious agents
on the heart valves.
The irregular
scarred nature of the valves provides a suitable environment to
bacteria that would originally pass by.
The organism
settle down to establish bacterial endocarditis.
Because
bacteremia frequenly follows a tooth extraction or urethral
catheterization, a person who has prior diagnosis of rheumatic heart
disease should be treated prophylactically with penicillin before
performing these procedures.
-
Mural thrombi
can
form in the atrial or ventricular chambers and give rise to
thromboembolic and infarction of various organs. Atrial thrombosis
occurs in about 40% of patients with rheumatic valvular disease.
Rarely a large thrombs in the left atrial appendage develops a stalk
and acts as a ball valve that obstructs the mitral valve orifice.
-Causes of
death in rheumatic fever and rheumatic heart disease:
Cardiac
failure ; Infective endocarditis ;
Embolism ( involve brain followed by the kidneys, spleen
and lungs) ; Sudden death occur as a result of obstruction
of the mitral valve orifice by a ball thrombus in the left atrium or
as a result of coronary ischemia associated with aortic stenosis ;
Thrombophlebitis of leg veins and pulmonary embolism ; Death may occur
from various other conditions such as pneumonia.
-Extracardiac
lesions:
Image Link
-
Subcutaneous nodules
: ( Painless nodules occur in wrist, elbows, ankles and knees. Nodules
occur in children and last for 4 to 6 days unlike
rheumatoid nodules
which may persist for months or years and may be painfull and tender .
Microscopic features:
Consist of a central core of fibrinoid necrosis surrounded by a zone
of radially palisading histiocytes and fibroblasts ).
- Arteritis
: (coronary artery inflammation-rheumatic arteritis ) ;
-
Polyarthritis :
( Synovial
membrane and the periarticular connective tissues are the sites of
hyperemia, edema, neutrophilic infiltration, fibrinoid change
and necrosis, followed by granulomatous change) ;
- Lesions in
lungs and pleura
: (Pleuritis ; Pleural effusion ; Rheumatic
pneumonia ; Lungs are usually congested , hemosiderin-laden
heart failure cells are seen within alveoli, together with fibrosis of
the alveolar septal walls . In addition, there is usually some
pulmonary vascular change, principally muscular and intimal arteriolar
thickening. Right ventricular hypertrophy -cor pulmonale may
develop as a result of a reactive pulmonary hypertension) ;
- Lesions of
the central nervous system
: (Sydenham's
chorea : disordered and involuntary movements of the trunk and
extremities).
PATHOLOGICAL
FEATURES OF RHEUMATIC HEART DISEASE :
Image Link1
Acute Rheumatic Carditis:
Acute rheumatic heart disease
is a pancarditis, involving all three layers of the heart.
The
myocarditis
is most typically involved in the acute stage of the
disease. A diffuse non-specific myocarditis is present in some cases,
together with a unique type of interstitial inflammation - the Aschoff
body.
Pathology of Aschoff body: CLICK HERE
The main cause of death in the
acute stage of rheumatic heart disease is heart failure from the
myocarditis.
Also seen during the acute
stage of the disease is a prominent
pericarditis, characterized by
tenacious deposits of fibrin that resemble the shaggy irregular
surfaces of two slices of buttered bread that have been pulled apart-
the so called bread-and-butter appearance.
The pericarditis may be
recognized clinically by a friction rub, but the involvement has
little functional effect and only rarely leads to constrictive
pericarditis.
During the acute stage, an
endocarditis involves mainly the valves, which show a finely nodular "verrucous"
appearance at the line of closure.
Areas of focal collagen
degeneration in the valve are surrounded by inflammation with
ulceration of the valve endocardial surface and deposition of fibrin
on the surface.
Chronic Rheumatic Heart
Disease:
Image Link2
A patient who has has an
attack of rheumatic fever is more susceptible to recurrent episodes
following infections by beta-hemolytic streptococci.
Such recurrent
attack result in repeated progressively increasing damage to the heart
valves.
Thus in
chronic recurrent rheumatic heart disease the valve involvement, which
was of little clinical significance during the acute attack, becomes
the major problem.
For example the mitral valve
which is most frequently and severely involved valve, shows
conspicuous, irregular thickening and calcification of its leaflets,
often with fusion of its commissures and thickening and fusion
of the chordae tendineae.
Image Link3
As a result the valve is often severely stenotic and when viewed from the atrial aspect has a narrowed orifice
described as having a "fish mouth" appearance.
The aortic valve, the
second most commonly involved valve, shows typical fusion of the commissures and later pronounced thickening and calcification of the
cusps, with resulting stenosis or insufficiency.
The tricuspid valve
is similarly involved, although less frequently than the aortic and mitral valves and the pulmonary valve is the least frequently
involved.
The subendocardial collections
of Aschoff nodules, usually in the left atrium, induce thickenings
called MacCallum plaques (patch).
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