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Transcript
SDL 9- Rheumatic Heart Disease and Rheumatic Fever
Acute Rheumatic Fever
Clinical: mild sore throat, redness of throat, streptococci elevated (ASO titer)—3 weeks later, fever, painful swelling of
knee joints, followed by pain and swelling of elbow joints. Pericaridal friction rub and murmur suggestive of
mitral regurgitation
Acute Rheumatic Fever (ARF) is multisystem inflammatory disease from autoimmune reaction to infection to group A
streptococcal infection
Almost all manifestations resolve completely except cardiac valvular damage (rheumatic heart disease) may persist
RHD is chronic and progressive condition that causes diability and death after many years
Disease of poverty: common in all countries until the early 19002 where it declined in industrial countries
Introduction of antibiotics and improved systems of medical care
RHD is most common cause of heart disease in children in developing countries
Epidemiology: acute rheumatic fever is most common in children 5-15 years
Less common in older adolescents and young adults; rare in persons >30 years
Prevalence of rheumatic heart disease peaks from 25-40yrs
Twice as frequently as males
Etiology and Pathogenesis
Bacterial factors
ARF exclusively caused by pharyngeal infection with group A streptococci (any strain)
Cutaneous streptococcal infection may lead to acute glomerulonephritis but not to ARF
Host factors: susceptibility to ARF is an inherited characteristic
Associations with alloantigen D8-17 on B lymphocytes found in patients with history of ARF
Immune response: when a susceptible host encounters Group A strep, an autoimmune reaction results
Damage to human tissue occurs as a result of cross-reactivity between epitopes on bacterial and host
Epitopes on streptococcal cell wall, cell membrane, and M protein are immunologically similar to molecules in
human myosin, keratin, actin, laminin, vimentin, and N acetylglucosamine
Molecular mimicry is the basis for autoimmune response that leads to RAF
Hypothesis: human molecules (particularly eiptopes in cardiac myosin) result in T cell sensitization
T cells are recalled following subsequent exposure to group A streptococci bearing immunologically
similar epitopes
Does not explain valvular damage that is the hallmark of rheumatic carditis
Antibodies to cardiac valve tissue cross-react with the N-acetylglucosamine of group A streptococcal carb
Link may be laminin
SDL 9- Rheumatic Heart Disease and Rheumatic Fever
Clinical Manifestations
Latent period: 3 weeks (1-5 weeks) between precipitating group A infection (onset of pharyngitis) and the appearance of
the clinical features of ARF
Exception is chorea lasting up to 6 months
Infection is commonly subclinical—only confirmed using streptococcal Ab testing such as anti-streptolysin O,
anti DNase B titers
Major Clinical manifestation: polyarthritis carditis, Sydenham chorea, subcutaneous nodules and erythema marginatum
Most common presentation of ARF: Polyarthritis and fever
Joint involvement: migratory, move over period of hours, affects large joints and is asymmetric
Pain is severe and usually disabling until anti-inflammatory medication commenced
Joints are hot, swollen, red
Synovial fluid contains numerous neutrophils but bacterial cultures are sterile
Only when there is evidence on inflammation, polyarthriits qualifies as major manifestation
Arthralgia: pain in joints without inflammation—minor manifestation
Large joint in migratory patterns
Polyarthritis: lasts 4 weeks, resolution is complete with no residual damage
Heart involvement: up to 60% of patients with ARF progress to rheumatic heart disease
RHD has potential to cause long-term disablilty and death
Endocardium, pericardium, and myocardium may be affected
Valvular damage is hallmark of rheumatic carditis regurgitation, leaflet thickening, scarring,
calcification and valvular stenosis
Pericarditis: causes friction rub or small effusion and central chest pain
Myocarditis: usually clinically silent
Sydenham chorea: neurologic disorder in isolation after latent period of several months when all other ARF
manifestations are gone
Mainly in females; rapid, purposeless, involuntary movements of extremities and face
Speech is slurred and jerky; emotional lability
One sided= hemi-chorea
Involuntary movements is due to vasculitis of basal ganglia
Skin manifestations: erythema marginatum—begins as pink macules that clear centrall, leaving serpignous,
spreading edge
Trunk, limbs, never face
Not pruritic and leave no residual scarring
Subcutaneous nodules: painless, small (.5-2cm) diameter, mobile, round, and painless lumps beneath skin and
overlying bony prominences on hands, feet, elbows, occiput, vertebrae
Delayed manifestation—2-3 weeks after disease onset last for just a few days—associated with carditis
Histologically: fibrinoid necrosis in center of nodule (swollen, eosiniophilic collagen fibers) surrounded
by lymphocytes, plasma cells, and macrophages
Other features: fever (>39C), elevated acute phase reactants (CRP, ESR), peripheral leukocytosis, neutrophils
Exception: “pure chorea” may appear after these markers of inflammation have returned to normal
Preceding Group A strep infection: essential in making the diagnosis of ARF
Most cases do not have positive throat swab culture, streptococcal antibody tests are essential
Anti-streptolysin O (ASO titer) and anti-DNase B (ADB) and antihyaluronidase
Ab’s reach peak titer at time of onset of ARF
ASO titers >200 Todd unites/mL in adults; >320 in children are considered elevated
SDL 9- Rheumatic Heart Disease and Rheumatic Fever
Diagnosis: Jones Criteria: combination of typical clinical features with evidence of Group A strep and exclude other dx
Rheumatic Heart Disease
Most serious complication of ARF
Often produces pancarditis (inflammation of entire heart)
Clinical presentation: endocardidis manifests as new murmur
Mitral valve is most commonly and severely affected (70% of patients), aortic valve (25%)
Pulmonary valve rarely effected
Myocarditis: may manifest as congestive heart failure (tachycardia, orthopnea, JVD, rales, hepatomegaly, gallop
rhythm, edema, swelling of peripheral extremities)
Pericardial friction rub indicates that pericarditis is present
Increased cardiac dullness to percussion and muffled heart sounds are consistent with pericardial effusion
Morphology: inflammatory lesions in any layer of the heart, lesions are sterile
Endocarditis: in cardiac valves (mainly mitral and aortic) are small, translucent, beadlike vegetations “verrucae” that are
1-2 mm and become gray brown
Veruccae adhere to atrial aspect of AV valves, and on ventricular aspect of semilunar valves
Rarely embolize
Histologically: consist of platelets and fibrin and usually overlie an inflammatory reaction with fibrinois necrosis
(degenerating collagen), mononuclear cells, and fibroblasts in adjacent valve
Verucae develop as a result of damage to CT as part of immune reaction ulceration and thrombus
MacCallum patch or plaque: characteristic irregular thickening of LA endocardium
Rough, patch-like thickening of parietal atrial endocardium (2-3 cm) near annulus of posterior mitral leaf
Do not be confused with endocardial lesions that represent jet lesions from regurgitant valves
Myocarditis: takes form of scattered, often perivascular Aschoff bodies (Aschoff nodules) within the CT of interstitium
Aschoff bodies: most characteristic microscopic lesion within heart in acute RHD
Early degenerative phase: several weeks after onset of clinical attack—focal edema and fibrinoid necrosis of CT
Intermediate granulomatous phase: fibrinoid changes are present in nodule, but granuloma formation is key
Central foci of fibrinoid necrosis—surrounded by inflammatory cells such as lymphocytes, plasma cells
and plump macrophages called Anitschow cells
Anitschow cells: caterpillar/owl eye cells—abundant basophilic cytoplasm, ragged borders, and 1-4
nuclei
Pathognomic for rheumatic carditis
Late fibrous phase: fibrinoid changes gradually disappear, granuloma regresses, nodule becomes fibrotic (3-6mo
SDL 9- Rheumatic Heart Disease and Rheumatic Fever
Pericarditis: fibrinous or serofibrinous exudates
Pericardial cavity: serous effusion
Visceral and parietal surfaces: covered by fibrin, “bread and butter pericarditis—shaggy pieces of bread
Resolves over time with no sequelae, except for pericardial adhesions
Chronic RHD
Valvular sequelae: myocardial and pericardial lesions of RHD resolve without permanent sequelae
Acute rheumatic endocarditis (valvulitis) long-term structural and functional alterations
Valve leaflets develop neovascularization and diffuse fibrosis
Thickened, shrunken, retracted, less pliable
Healing of verrucous lesions fibrous adhesions between leaflets (esp at commisures—commissural fusion)
Shortening of cordae tendinae
Recurrent episodes of rheumatic fever progressive damage to valves
Sclerosis of the valve apparatus with fusion of leaflets and calcification stenosis and insufficiency develops
Mitral and aortic valves are most common targets of RHD
Mitral valve stenosis secondary to RHD in 99% of cases
LA dilates, may harbor thrombi in appendage or attached to atrial wall
Congestive changes in lungs pulmonary edema, RV hypertrophy, LV is usually normal
Clinical Manifestations
Years or decades after initial episode
Latent period is shorter, probably as a result of greater risk of repeated attacks
Critical mitral valve stenosis may occur before age of 20
Death rate of ARF usually peaks in 1st and 2nd decades of life
Death caused by Chronic rheumatic heart disease (chronic valvular deformities) is maximal in 5th decade