Rheumatic Fever and Endocarditis Quiz

Rheumatic Fever and Rheumatic Heart Disease

• Rheumatic fever is an acute, immunologically mediated, post-streptococcal, multisystem inflammatory disease.
• It primarily affects the heart, joints, central nervous system, skin, and subcutaneous tissues.
• It usually occurs 1-5 weeks after a streptococcal infection (group A β-hemolytic streptococcal infection).
• The disease predominantly affects children aged 5-15 years.
• Tissue lesions in rheumatic fever are sterile, meaning they don't contain streptococci.
• Recurrence of rheumatic fever is always preceded by a streptococcal infection.

Pathogenesis

• Rheumatic fever is a post-infectious immunologic disease resulting from the immune system's reaction to streptococcal antigens.
• The body's antibodies cross-react with human tissue antigens, leading to inflammation.
• Key antigens involved include the cell wall polysaccharide of group A Streptococcus, which can cross-react with cardiac valves.
• The cell wall M protein shows cross-reactivity with sarcolemma and myosin in cardiac muscle.
• The hyaluronate capsule of group A Streptococcus is identical to human hyaluronate present in joint tissues.
• There may be autoantibodies in the brain that target basal ganglia and dopaminergic neurons.

Environmental Factors and Susceptible Hosts

• Environmental factors like overcrowding and socioeconomic status can influence the risk of rheumatic fever.
• Factors within the susceptible host, such as family history of the disease or genetic predisposition also play a significant role.
• Repeated or continuous streptococcal infections increase susceptibility to rheumatic fever.

Clinical Manifestations

• Cardiac: Pancarditis (inflammation of the endocardium, myocardium, and pericardium).
• Extracardiac: Fever, arthritis (migratory polyarthritis), arthralgia, skin lesions (erythema marginatum, subcutaneous nodules), and chorea.

Jones Criteria for Diagnosis

• To diagnose rheumatic fever, two major or one major and two minor criteria are needed.
• Major criteria: Carditis, arthritis (migratory polyarthritis), chorea, subcutaneous nodules, and erythema marginatum.
• Minor criteria: Clinical manifestations like fever, arthralgia, history of rheumatic fever or rheumatic heart disease. Laboratory findings like elevated acute-phase reactants (ESR, C-reactive protein, leukocytosis), prolonged PR interval on ECG. Supporting evidence of recent streptococcal infection (e.g., increased streptococcal antibody titers, positive throat culture for group A strep, or history of scarlet fever).

Morphology

• Acute phase of rheumatic fever: Characterized by Aschoff nodules, which are small lesions:
  • Foci of fibrinoid necrosis (immune complex reactions).
  • Surrounding lymphocytes, macrophages, and plasma cells.
  • "Activated" histiocytes (Anitschkow cells or Aschoff cells) with caterpillar-like appearance and central nuclei.
  • Found in pericardium, myocardium, and valves.
  • Eventually heal through fibrosis.
• Microscopic appearance of Aschoff bodies: Spherical or fusiform structures with central necrosis, surrounded by lymphocytes (primarily T cells), scattered plasma cells, and activated macrophages.
• Anitschkow cells have abundant cytoplasm and nuclei with centrally condensed wavy ribbon chromatin.

Pancarditis

• Pericarditis: Aschoff nodules form in the pericardium, potentially causing pericardial effusion, and serous exudate.
• Myocarditis: Aschoff nodules develop in the myocardium with interstitial oedema and mild inflammation, which can lead to left ventricular failure.
• Endocarditis: Aschoff nodules lead to irregularities in valve surfaces, with fibrin and platelet aggregations forming small vegetations ("verrucae"), often along the valve lines. Aortic and mitral valves are most susceptible to significant damage.

Extracardiac Manifestations

• Joints: Affects large joints like the knees, characteristically causing pain that subsides with aspirin.
• Syndenham's Chorea: A disorder characterized by involuntary dance-like movements, which are commonly seen in patients with rheumatic fever. Restlessness, difficulty maintaining still posture, involuntary movements, disappearing during sleep, and some emotional instability are characteristic.

Subcutaneous Nodules

• Painless nodules beneath the skin found on extensor surfaces of joints.
  • Usually found on elbows or wrists.
• Typically resolve within a few days to several weeks.

Erythema Marginatum

• Flat or slightly raised, painless rash with pale centers and rounded or serpiginous margins.
• Common in children.

Chronic Rheumatic Heart Disease (RHD)

• Permanent valve deformity due to post-inflammatory fibrosis occurring 10-30 years after repeated acute RF attacks.
• 70% of cases have just mitral involvement; some have both mitral and aortic.
• Endocarditis heals through progressive fibrosis; valvular leaflets fibrosis leads to stenosis. Cordae tendonae fibrosis leads to regurgitation.
• Valves thicken and retract, often fusing and with calcium deposits.
• Fibrous bridging across valvular commissures with calcification creates "fish mouth" stenosis.
• Microscopic examination shows neovascularization and diffuse fibrosis that obliterates normal leaflet architecture.

Long-Term Outcome of RHD

• Depends on chronic valve changes' severity.
• Potential heart failure from mitral stenosis, mitral incompetence, or mixed mitral valve disease.
• Susceptibility to infective endocarditis.
• Left atrial thrombus formation can occur.

Types of Endocarditis

• Non-infective (Non-microbial): Rheumatic heart disease, Libman-Sacks endocarditis (SLE), Non-bacterial thrombotic endocarditis (NBTE).
• Infective (Microbial): Primarily bacterial or fungal.

Non-bacterial Thrombotic Endocarditis (NBTE)

• Characterized by the deposition of small, sterile thrombi on cardiac valve leaflets.
• Occurs more commonly in mitral valves in debilitated patients (cancer or sepsis), often in those with mucinous adenocarcinomas.
• Sterile, bland, non-destructive vegetations.
• Doesn't cause tissue destruction nor show inflammation.

Endocarditis of Systemic Lupus Erythematosus (Libman-Sacks Endocarditis)

• Occurs in approximately 10% of patients with lupus.
• Lesions from immune complex deposition.
• Affects mitral and tricuspid valves, as small (1-4 mm), sterile vegetations.
• Appear warty (verrucous) in appearance.
• Microscopically, composed of fibrin and platelet thrombi with fibrinoid necrosis. Capillaries and infiltration by histiocytes, plasma cells, lymphocytes, and neutrophils occur in the endocardium.

Infective Endocarditis (IE)

• Microbial infection affecting heart valves or mural endocardium.
• Leads to vegetation formation (thrombotic debris and microorganisms), and often destroys underlying cardiac tissue.
• Classified into acute (ABE) and subacute (SABE) forms.

IE Pathogenesis

• Bacteria entering the bloodstream implant on cardiac valves or endocardium due to surface adhesion molecules.
• Bacteria preferentially lodge on damaged valves (especially in RHD and congenital heart disease) over healthy ones
• Conditions causing stress to valves lead to endothelial damage, favoring platelet thrombi formation, which then get infected by circulating bacteria.

Sub-acute Bacterial Endocarditis

• Damage to the pre-existing valve leads to platelet-fibrin deposits and thrombotic vegetations.
• Bacteria invade thrombotic vegetations and slowly proliferate causing gradual valve destruction.
• Poorly virulent causative agents like Streptococcus viridans.

Acute Bacterial Endocarditis

• Patients with normal valves affected by highly virulent causative agents (e.g., Staphylococcus aureus).
• Bacteria enter the bloodstream resulting in rapid proliferation of organisms on heart valve leading to necrosis and valve destruction.
• Rapidly forming vegetations depend on both virulence of the organism and the size of the bacterial invasion. Host immunity plays a role as well.

Risk Factors for IE

• Rheumatic heart disease, congenital heart malformations, other cardiac malformations, and various other heart conditions.
• Iatrogenic factors like prosthetic valves, indwelling catheters; immunocompromised patients.
• Infections like neutropenia, AIDS or, IV drug use.

IE Morphology

• Macroscopic: Friable (easily disintegrating), bulky vegetations that are bacteria laden.
  • Vegetations can be single or multiple and range in size from millimeters to centimeters.
• Microscopic: Acute endocarditis vegetations tend to be bulkier, can cause perforation or erosion of the valve leaflet, and potentially spread to myocardial abscesses. Subacute endocarditis vegetations tend to be smaller, don't usually cause perforation, and extend to adjacent mural endocardium. IE shows mixed inflammatory cells and colonies of bacteria.

IE Complications

• Cardiac: Valvular insufficiency, myocardial abscess, perforation of IV septum, suppurative pericarditis.
• Embolic: Left-sided lesions (brain, spleen, kidneys, limbs), and less commonly mycotic aneurysms in vessels. Right-sided lesions can affect the lung. Artificial valve dislodgement also a risk.

IE Diagnosis

• Clinical suspicion based on known risk factors, unexplained fever, septicemia, heart failure, and embolic infarcts.
• Investigations include raised ESR, white blood cell count, normochromic, normocytic anaemia, and blood cultures to identify the causative organism (if no antibiotics are being taken).
• Echocardiogram may show vegetation.

Major Forms of Vegetative Endocarditis

• Information on the location, pathogens, and microscopic/pathological features of different endocarditis types.

Test your knowledge about rheumatic fever and related cardiac conditions in this quiz. Answer questions about its pathology, manifestations, age groups affected, and diagnostic features. Ideal for medical students and healthcare professionals looking to reinforce their understanding of these topics.