WEEK 3: Rheumatic heart disease Flashcards
What is Acute Rheumatic fever (ARF)?
ARF is a multisystem autoimmune disease resulting from infection with group A streptococcus.
Many parts of the body are affected almost all resolve completely except for valvular injury.
Episodes tend to recur in the same individuals and may lead to rheumatic heart disease (RHD.
Discuss the epidemiology of ARF and RHD.
- ARF and RHD are diseases of poverty
- RHD is the most common cause of heart disease in children in developing countries
*Also a major cause of mortality and morbidity in adults
*Affect about 15 and 19 million people worldwide
*Causes about 250000 deaths occur each year.
*95% of them in developing countries.
*RHD is prevalent in sub-Saharan Africa, Pacific nations, Australasia, and Indian subcontinent.
About 500,000 persons acquire ARF each year
97 % are in developing countries where the incidence of ARF exceeds 50 per 100,000 children per year.
*ARF is a disease of children aged 5–15 years.
-Incidence decline thereafter
-Initial episodes are rare in adults older than 35 years
-Recurrent episodes remain relatively common in adolescents and young adults
*ARF is equally common in males and females, but RHD is more common in females
sometimes up to twice as frequently as males
Reasons are unclear
*No known association with ethnicity
Discuss the Etiological factors of ARF.
- Upper respiratory tract infection with group A streptococci
*any strain of group A streptococcus has the potential to cause ARF
Host Factors
-Approximately 3–6% of any population may be susceptible to ARF
-Particular HLA class II alleles appear to be strongly associated with susceptibility
Discuss the pathogenesis of ARF.
An autoimmune reaction triggered by molecular mimicry between
-Cell wall M proteins of the infecting Streptococcus pyogenes
-Cardiac myosin and laminin
During subsequent infection
-Antibodies or cellular immune responses directed against group A streptococci cross-react with epitopes on host tissue
-Valvular damage is caused by T-cell and macrophage infiltration, which persists for years after the initial event.
-The pathologic lesion of ARF is the Aschoff body
a granulomatous lesion containing T and B cells, macrophages, large mononuclear cells, multinucleated giant cells and polymorphonuclear leukocytes in the myocardium.
Describe clinical features of ARF.
-A latent period is of ~3 weeks (1–5 weeks).
-chorea and indolent carditis, may follow prolonged latent periods lasting up to 6 months.
-A prior group A streptococcal infection is commonly subclinical Confirmed using streptococcal antibody testing.
- Polyarthritis and fever are commonest.
Polyarthritis is present in 60–75% of cases. - Carditis in 50–60%.
*Carditis refers to inflammation of the heart, specifically involving the myocardium (the muscular tissue of the heart), endocardium (the inner lining of the heart chambers and valves), and pericardium (the outer lining or sac surrounding the heart). - Chorea in <2% to 30%.
*Chorea is a neurological disorder characterized by brief, involuntary, irregular, and purposeless movements that typically affect multiple body parts - Erythema marginatum and subcutaneous nodules are rare, found in <5% of cases
Discuss Carditis as a clinical feature of ARF.
*Usually pancarditis (involves pericardium, myocardium and endocardium)
Clinical manifestations varies widely
*Pericarditis- pericardial pain and a friction rub new murmurs or changing murmurs
*Myocarditis: heart failure
-The mitral valve is almost always affected
sometimes together with the aortic valve
isolated aortic valve involvement is rare.
-Early valvular damage leads to regurgitation
recurrent episodes results in leaflet thickening, scarring, calcification, and valvular stenosis
Myocardial inflammation may affect electrical conduction pathways
*Causes P-R interval prolongation
*Rarely produces clinical symptoms
*An important and helpful diagnostic clue
Discuss Joint Involvement Arthralgia as a clinical feature of ARF.
-Arthritis
migratory, moving from one joint to another over a period of hours, no residual deformity.
-Involve large joints—knees, ankles, hips, elbows
-Asymmetric
Have severe pain that highly responds to Salicylates (diagnostic
Less severe joint involvement
Qualifies only as a minor manifestation.
Affects large joints and has migratory pattern
Discuss Sydenham’s chorea as a clinical feature of ARF.
Commonly occurs as a sole expression of ARF
Late manifestation (thus no ESR or ASO titre elevation)
Common in females
Characterized by involuntary, purposeless, rapid, and abrupt movements associated with muscular weakness and emotional lability.
*The abnormal movements disappear during sleep.
Discuss skin manifestations of ARF.
- Erythema marginatum
-pink macules that clear centrally, leaving a serpiginous, spreading edge.
-evanescent, appearing and disappearing before the examiner’s eyes.
-occurs on the trunk and limbs
-never on the face - Subcutaneous nodules
-painless, small (0.5–2 cm), mobile lumps beneath the skin overlying bony prominences,
hands, feet, elbows, occiput, vertebrae.
-delayed manifestation, 2–3 wks after onset of disease
-commonly associated with carditis.
State other manifestations of ARF.
- Fever
-Occurs in most cases of ARF
-Low to high grade - Acute-phase reactants (CRP & ESR) often dramatically elevated
- Leukocyte count is mildly elevated.
Discuss the diagnosis of ARF.
- No definitive test
relies on
-Combination of typical clinical features and -Evidence of the precipitating group A streptococcal infection, and the exclusion of other diagnoses.
Called the Jones criteria.
Outline the major manifestation of ARF used in diagnosis.
Carditis
Polyarthritis
Chorea
Erythema magnatum
Subcutaneous nodules
Outline Minor manifestations used in the diagnosis of ARF.
Minor manifestations
Clinical: fever, polyarthralgia
Laboratory: elevated erythrocyte sedimentation rate or leukocyte count
Electrocardiogram: prolonged P-R interval
Evidence of a Preceding Group A Streptococcal Infection essential for ARF diagnosis.
Exception of chorea and low-grade carditis
Late manifestations
-Elevated or rising anti-streptolysin O (ASO) and anti-DNase B (ADB) titers.
-A positive throat culture
-Rapid antigen test for group A streptococcus
-Recent episode of scarlet fever.
Discuss Jones Criteria for diagnosis.
- Primary episode of rheumatic fever
- Recurrent attack of rheumatic fever in a patient without established rheumatic heart disease
- Recurrent attack of rheumatic fever in a patient with established rheumatic heart disease
- Primary episode of rheumatic fever
-Two major or one major and two minor manifestations plus evidence of preceding group A streptococcal infection
- Recurrent attack of rheumatic fever in a patient without established rheumatic heart disease
Two major or one major and two minor manifestations plus evidence of preceding group A streptococcal infection
- Recurrent attack of rheumatic fever in a patient with established rheumatic heart disease
Two minor manifestations plus evidence of preceding group A streptococcal infection
