teach me important concept of infective endocarditis microbiology with easy notes but should cover all important and must know points to crack university exam
infective endocarditis vegetation heart valve microbiology
This intraoperative clinical photograph displays a macro-level view of excised cardiac vegetation, typical of infective endocarditis, resting on a white, sterile surgical gauze swab. The vegetation appears as an irregular, friable, and multi-lobulated tissue mass with a reddish-pink hue, indicating significant vascularization or associated blood clot formation. The specimen's texture is heterogeneous and rough, consistent with a collection of fibrin, platelets, and microorganisms typically found on heart valve surfaces during active infection. The surrounding white gauze shows several focal areas of bright red serosanguinous staining where the vegetation has been placed. This image is medically significant for illustrating the gross pathological morphology of a mitral valve vegetation following surgical excision and valve debridement. It serves as a visual record of the endovascular disease process, highlighting the size and friability of the mass that contributed to valvular regurgitation and potential embolic risk.
This composite educational image illustrates the macroscopic and histopathological characteristics of infective endocarditis on human heart valves. (A) Clinical photograph of an excised valve showing friable, reddish-brown vegetations (VG) contrasting against smooth, translucent normal tissue (N). (B, C) Light microscopy using Alcian blue and Nuclear Fast Red counterstain displays the interface between the septic thrombus (red-stained inflammatory cells and polylobed PMNs) and underlying valvular tissue exhibiting mucoid degeneration (blue-stained areas). The dotted line marks the clear boundary between the infected vegetation and the valve stroma. (D) TUNEL assay micrograph highlights the presence of cellular damage. Apoptotic cells (indicated by arrowheads) appear as dark, discrete nuclear spots, while extracellular fragmented DNA (indicated by arrows) shows diffuse, dark staining concentrated at the vegetation-valve interface. This visual series demonstrates the key pathological hallmarks of valvular infection, including thrombus formation, inflammatory infiltration, and programmed cell death.
Two-panel diagnostic echocardiography (ultrasound) images demonstrating infective endocarditis with multiple vegetations on the left heart valves. The left panel shows a parasternal long-axis view of the bicuspid aortic valve, with hyperechoic, irregular masses (vegetations) attached to the tips of the anterior (yellow arrow) and posterior (blue arrow) leaflets. The right panel highlights the mitral valve apparatus, where another distinct hyperechoic vegetation is visible on the body of the anterior mitral valve leaflet (green arrow). These findings are highly suggestive of active infective endocarditis, illustrating the characteristic appearance of mobile, irregular echoes attached to valvular endocardial surfaces. Clinical relevance includes the high risk of systemic embolization given the size and location of these vegetations, commonly associated with pathogens such as Streptococcus gordonii. This visual serves as an educational tool for identifying valvular pathology, measuring vegetation dimensions, and assessing the risk of secondary complications like septic emboli in a cardiothoracic or infectious disease context.
Diagnostic ultrasound montage demonstrating infective endocarditis (IE) and its surgical resolution via transthoracic echocardiography. Panels A (grayscale) and B (sepia-toned) show a parasternal long-axis view of the heart. A distinct, pedunculated, and echogenic mass labeled 'vegetation' is indicated by a white arrow, attached to the aortic valve leaflet. Panels C and D utilize color Doppler imaging in a four-chamber or modified atrial view to assess hemodynamic changes. Panel C illustrates an abnormal left-to-right atrial shunt, characterized by a high-velocity, turbulent multi-colored jet crossing the interatrial septum. Panel D, obtained postoperatively, shows the absence of this shunt and restored laminar flow (represented by stable red and blue signals), confirming successful surgical repair and removal of the infected vegetation. This image sequence serves as a clinical comparison for medical students and cardiologists to identify valvular vegetations and evaluate the efficacy of surgical intervention in congenital or acquired heart defects complicated by infection.
🫀 Infective Endocarditis (IE) - Complete Microbiology Notes for Exam
Sources: Robbins & Kumar Basic Pathology | Goldman-Cecil Medicine | Frameworks for Internal Medicine | Braunwald's Heart Disease | Fitzpatrick's Dermatology
1. DEFINITION
- Can also affect: aorta, aneurysmal sacs, prosthetic devices, pacemaker leads
- Vast majority caused by bacteria (rarely fungi, rickettsiae, Chlamydia)
2. CLASSIFICATION
| Feature | Acute IE | Subacute IE |
|---|---|---|
| Onset | Rapid (days) | Insidious (weeks to months) |
| Valves | Normal or abnormal | Usually abnormal/damaged |
| Virulence | High | Low |
| Classic organism | S. aureus | Viridans streptococci |
| Prognosis without Rx | Fatal in weeks | Survives months |
| Tissue destruction | Severe | Moderate |
Exam tip: The line between acute and subacute is not always clear - many cases fall on a spectrum.
3. PREDISPOSING CONDITIONS (Risk Factors)
Cardiac Risk Factors (Most Common)
| Risk Factor | Notes |
|---|---|
| Mitral valve prolapse (especially with regurgitation) | #1 preexistent risk factor today |
| Degenerative valvular disease | Calcific stenosis, bicuspid aortic valve |
| Rheumatic heart disease | Was previously #1, now less common |
| Prosthetic heart valves | Accounts for 10-20% of all IE cases |
| Previous IE | Major risk for recurrence |
| Congenital heart disease | Especially uncorrected VSD |
Non-Cardiac Risk Factors
- IV drug use (IVDU) - very high risk
- Neutropenia, immunodeficiency, malignancy
- Diabetes mellitus
- Prolonged use of indwelling vascular catheters
- Pacemakers / cardiac implantable electronic devices (CIEDs)
4. PATHOGENESIS - STEP BY STEP
STEP 1: Endothelial damage (turbulent flow, jets, catheters)
↓
STEP 2: Sterile platelet-fibrin thrombus forms at damaged site
↓
STEP 3: Bacteremia (from dental procedure, surgery, gut, skin, IV drugs)
↓
STEP 4: Bacteria adhere to thrombus via surface adhesins
↓
STEP 5: Bacteria proliferate within vegetation (protected from host defenses)
↓
STEP 6: Vegetation grows → valve destruction → emboli → metastatic infection
- Access to bloodstream (bacteremia)
- Ability to adhere to endocardium/thrombus
5. CAUSATIVE ORGANISMS - THE EXAM FAVORITE SECTION 🔑
The "Big 3" account for the vast majority of IE cases:
A. Viridans Group Streptococci (VGS)
| Feature | Detail |
|---|---|
| Species | S. sanguis, S. mitis, S. salivarius, S. mutans |
| Source | Normal oral/dental flora |
| Entry | Dental procedures, daily oral trauma |
| Type of IE | Subacute native valve IE |
| Valve | Left-sided (mitral > aortic) |
| Susceptibility | Highly penicillin-susceptible |
| Prognosis | Cure rates ~100% with 4 weeks IV penicillin |
| Frequency | 50-60% of community-acquired IE |
Memory hook: "Viridans = Viridans gums" - they live in the mouth and enter after dental work
B. Staphylococcus aureus
| Feature | Detail |
|---|---|
| Source | Skin flora; healthcare/nosocomial |
| Type of IE | Acute IE (rapid, destructive) |
| Valve | Any valve - normal OR diseased |
| IVDU | Classically affects tricuspid valve (right-sided IE) |
| Complications | Perivalvular abscess, metastatic septic emboli (lung, brain, kidneys) |
| Treatment (MSSA) | Nafcillin or oxacillin |
| Treatment (MRSA) | Vancomycin |
| Now #1 cause in | High-income countries, healthcare settings, IVDU |
Remember: S. aureus can infect normal valves - unique among common IE organisms!
C. Streptococcus gallolyticus (formerly S. bovis)
| Feature | Detail |
|---|---|
| Old name | Streptococcus bovis biotype I |
| Type | Subacute IE |
| Special association | Colon cancer / colonic polyps |
| Action required | Colonoscopy mandatory when isolated |
| Susceptibility | Highly penicillin-susceptible |
High-yield exam pearl: Any patient with S. gallolyticus endocarditis → rule out colonic malignancy!
D. Enterococci
| Feature | Detail |
|---|---|
| Species | E. faecalis (>90%), E. faecium |
| Source | GI and genitourinary tracts |
| Type | Can be subacute OR acute |
| Frequency | ~10% of all IE cases |
| Valve | Predominantly left-sided (even in IVDU) |
| Resistance | Intrinsically resistant to cephalosporins, low-level aminoglycosides |
| Treatment | Ampicillin + gentamicin (or streptomycin); alternative: ampicillin + ceftriaxone |
| Duration | 4-6 weeks |
E. HACEK Group (Gram-Negative Fastidious Organisms)
| Feature | Detail |
|---|---|
| Source | Normal oral/upper respiratory commensals |
| Type | Subacute IE |
| Frequency | ~5% of IE cases |
| Growth | Fastidious; grow in blood cultures within 7 days |
| Treatment | Ceftriaxone (ampicillin historically) |
| Eikenella | Associated with IVDU (needle/skin licking) |
F. Coagulase-Negative Staphylococci (CoNS) - e.g., S. epidermidis
| Feature | Detail |
|---|---|
| Source | Normal skin flora |
| Risk | Healthcare contact (catheters, prosthetics) |
| Native valve IE | Uncommon, but increasing |
| Prosthetic valve | Major pathogen (especially early PVE) |
| Concern | High rates of perivalvular abscess and heart failure despite subacute presentation |
| Resistance | Often oxacillin-resistant (treat as MRSA) |
G. Fungi
| Feature | Detail |
|---|---|
| Common organisms | Candida spp. and Aspergillus spp. |
| Risk | IVDU, prolonged IV catheters (TPN), cardiac valve surgery |
| Candida | Grows in blood cultures |
| Aspergillus | Rarely cultured from blood - need valve/embolic tissue |
| Mortality | Very high |
| Treatment | Usually requires valve replacement surgery |
H. Culture-Negative IE (~10% of all cases)
- Prior antibiotic therapy (most common reason)
- Fastidious/slow-growing organisms
- Coxiella burnetii (Q fever) - serologic diagnosis
- Bartonella spp. (homeless, louse exposure)
- Brucella, Legionella, Tropheryma whipplei
- HACEK organisms (if not incubated long enough - now less of an issue)
Exam tip: Always ask about prior antibiotic use in any patient with culture-negative IE!
6. ORGANISMS BY CLINICAL SETTING (HIGH-YIELD TABLE)
| Clinical Setting | Most Common Organism(s) |
|---|---|
| Community-acquired native valve | Viridans streptococci (50-60%) |
| Healthcare/nosocomial | S. aureus (#1) |
| IV drug use - tricuspid | S. aureus (>50%) |
| IV drug use - left-sided | Viridans streptococci, Enterococci |
| Prosthetic valve - Early (<2 months) | S. aureus, CoNS (S. epidermidis) |
| Prosthetic valve - Late (>2 months) | S. aureus, Viridans streptococci |
| Dental procedure | Viridans streptococci |
| GU/GI source | Enterococci |
| Colonic malignancy association | S. gallolyticus |
| Fungal IE | Candida, Aspergillus |
| Culture-negative | Coxiella burnetii (Q fever), Bartonella |
7. MORPHOLOGY OF VEGETATIONS
- Fibrin + platelets (thrombus) + bacteria + inflammatory cells (PMNs)
- Underlying valve: necrosis, inflammation, destruction
- May extend to cause perivalvular/ring abscess
| Type | Organisms | Location | Features |
|---|---|---|---|
| IE | Present | Along line of closure + leaflet | Friable, destructive, large |
| Rheumatic | Absent | Line of closure | Small, firm, "verrucous" |
| Libman-Sacks (SLE) | Absent | Both sides of valve | Small, flat, non-destructive |
| Marantic (NBTE) | Absent | Line of closure | Small, sterile, cancer/debility |
8. CLINICAL FEATURES
Peripheral Stigmata of IE (Must memorize!)
| Sign | Description | Mechanism | Exam Clue |
|---|---|---|---|
| Osler nodes | Painful, raised, red papulonodules on fingertips/toe pads | Immune complex / microemboli | Painful = Osler |
| Janeway lesions | Painless hemorrhagic macules on palms/soles | Septic emboli | Painless = Janeway (on Palms) |
| Splinter hemorrhages | Linear brownish-red lines in nail beds | Microemboli | Non-specific (can be normal) |
| Roth spots | Oval retinal hemorrhages with white/pale center | Immune complexes / microemboli | Seen on fundoscopy |
| Petechiae | Small red spots on skin/mucosa | Microemboli/vasculitis | Non-specific |
| Clubbing | Finger clubbing | Chronic IE | Subacute disease |
Memory trick: Osler = Ouch (painful), Janeway = Just painless (Janeway on palms/soles is PAINLESS)
9. MODIFIED DUKE CRITERIA (Diagnosis)
MAJOR Criteria
- Two separate positive blood cultures with typical organisms (S. viridans, S. bovis/gallolyticus, HACEK, S. aureus, Enterococcus) from community source
- Persistently positive blood cultures (≥2 positive, drawn >12 hours apart)
- Single positive blood culture for Coxiella burnetii, OR Phase I IgG titer >1:800
- New valvular regurgitation
- Oscillating intracardiac mass at site of endocardial injury
- Perivalvular abscess
- New dehiscence of prosthetic valve
MINOR Criteria
- Predisposing heart condition or IV drug use
- Fever ≥38°C (100.4°F)
- Vascular phenomena - arterial emboli, septic pulmonary infarcts, Janeway lesions, mycotic aneurysm, intracranial hemorrhage, conjunctival hemorrhages
- Immunologic phenomena - glomerulonephritis, Osler nodes, Roth spots, rheumatoid factor
- Microbiologic evidence not meeting major criteria (single positive culture for less typical organism)
Mnemonic for Minor criteria: "FVIMI" = Fever, Vascular, Immunologic, Microbiology, predIsposition
10. COMPLICATIONS (Know for Exam)
| System | Complication |
|---|---|
| Cardiac | Heart failure (most common cause of death), perivalvular abscess, conduction defects (AV block), pericarditis |
| Embolic | Stroke, TIA, renal infarcts, splenic infarcts, septic pulmonary emboli (right-sided IE) |
| Renal | Glomerulonephritis (immune complex deposition), renal infarcts |
| Neurologic | Stroke (15-20% of patients), meningitis, brain abscess, mycotic aneurysm |
| Metastatic | Bone (osteomyelitis), joints (septic arthritis), spleen (abscess) |
11. ANTIBIOTIC PROPHYLAXIS (Key Points)
- Prosthetic cardiac valve or material
- Previous IE
- Congenital heart disease (unrepaired cyanotic CHD, or within 6 months of repair)
- Cardiac transplant with valve abnormality
- Ventricular assist devices and implantable hearts (new addition)
- Amoxicillin 2g PO 30-60 min before procedure (first choice)
- Penicillin allergy: Doxycycline (clindamycin no longer recommended due to C. difficile risk)
12. TREATMENT OVERVIEW (Principles)
| Organism | Antibiotic | Duration |
|---|---|---|
| Viridans streptococci (penicillin-sensitive) | Penicillin G or Ceftriaxone | 4 weeks |
| S. aureus (MSSA) | Nafcillin / Oxacillin | 4-6 weeks |
| S. aureus (MRSA) | Vancomycin | 4-6 weeks |
| Enterococcus (susceptible) | Ampicillin + Gentamicin | 4-6 weeks |
| HACEK | Ceftriaxone | 4 weeks |
| Fungal | Amphotericin B + valve replacement | Long-term |
Surgery indications: Heart failure, persistent infection despite antibiotics, perivalvular abscess, fungal IE, prosthetic valve dehiscence, recurrent emboli
13. QUICK EXAM MEMORY AIDS
Organism Mnemonics
The "Rules of Right vs Left"
| Right-sided IE | Left-sided IE |
|---|---|
| Tricuspid valve (IVDU) | Mitral > Aortic valve |
| S. aureus | Viridans strep, Enterococcus |
| Septic pulmonary emboli | Systemic emboli (brain, kidneys) |
| Better prognosis (<10% mortality) | Worse prognosis |
Valve involvement frequency (general)
14. SUMMARY TABLE - "The Must-Know Organisms"
| Organism | Type | Key Setting | Unique Feature |
|---|---|---|---|
| Viridans Streptococci | Subacute | Dental/oral | Most common community IE; penicillin-sensitive |
| S. aureus | Acute | IVDU, healthcare | Can infect normal valves; #1 in high-income countries |
| Enterococci | Subacute/acute | GU/GI tract | E. faecalis most common; ampicillin + aminoglycoside |
| S. gallolyticus | Subacute | GI tract | Colonoscopy for colon cancer |
| HACEK | Subacute | Oral flora | Fastidious; ~5% of IE |
| CoNS (S. epidermidis) | Subacute | Prosthetic valves, healthcare | Major cause of PVE |
| Candida | - | IVDU, catheters | Grows in cultures; surgery usually needed |
| Aspergillus | - | Valve surgery, IVDU | Rarely cultured; check galactomannan |
| Coxiella burnetii | - | Q fever (animal exposure) | Culture-negative; serology >1:800 |
teach me important concept of rheumatic fever microbiology with easy notes but should cover all important and must know points to crack university exam
rheumatic fever Aschoff body mitral valve stenosis pathology
This clinical photograph shows a gross pathological specimen of a human heart, specifically an atrial view of the mitral valve. The image demonstrates hallmark signs of chronic rheumatic heart disease. Key features include significant thickening and fibrosis of the valve leaflets, resulting in a 'fish-mouth' or 'buttonhole' appearance of the valvular orifice. There is evidence of extensive commissural fusion and multiple focal areas of yellowish-white calcification along the leaflet margins and within the valve body. These structural changes characterize severe mitral stenosis, where the restricted opening of the valve impairs blood flow from the left atrium to the left ventricle. The surrounding atrial endocardium appears thickened, consistent with chronic pressure overload. This visual is highly representative for educational purposes in cardiology and pathology to illustrate the long-term sequelae of rheumatic fever on cardiac valves.
Two-panel diagnostic imaging featuring a 2D transthoracic echocardiogram (TTE) of severe mitral stenosis, typically associated with rheumatic heart disease. Panel (a) shows a parasternal long-axis view during diastole, highlighting significant thickening and increased echogenicity of the mitral valve leaflets. The anterior leaflet demonstrates characteristic 'doming' (hockey-stick deformity) with restricted excursion, indicating limited valve opening. Panel (b) presents a parasternal short-axis view at the level of the mitral valve orifice. White arrows point to commissural fusion, a hallmark of stenotic valvular pathology. The mitral valve area (MVA) is manually traced via planimetry (indicated by the dotted line), yielding a measurement of 0.73 cm², which falls into the category of severe stenosis (MVA < 1.0 cm²). These images demonstrate the classic morphology used in cardiology for assessing valvular narrowing, leaflet mobility, and subvalvular involvement to determine the clinical severity of mitral stenosis.
This diagnostic image is a transthoracic echocardiogram in the parasternal long-axis (PLAX) view, demonstrating classic features of mitral stenosis secondary to rheumatic heart disease. The image shows the left ventricle (LV), left atrium (LA), and the aortic root. Key pathology is localized to the mitral valve, where both the anterior and posterior leaflets exhibit significant thickening and increased echogenicity. The leaflets demonstrate restricted diastolic opening, resulting in a narrow valve orifice. The anterior mitral valve leaflet shows a characteristic 'doming' appearance (hockey-stick deformity), which is pathognomonic for rheumatic involvement. The LA appears moderately dilated, a common consequence of chronic mitral stenosis. This educational visual is intended for cardiology and radiology students to illustrate the valvular morphology and mechanical obstruction characteristic of rheumatic mitral valve disease, emphasizing the role of non-invasive ultrasound imaging in assessing valvular heart disease.
This diagnostic image is a transthoracic echocardiogram (TTE) in the apical four-chamber view, providing a simultaneous visualization of both the left and right sides of the heart. The ultrasound displays significant structural pathology of the atrioventricular valves. The mitral valve leaflets appear diffusely thickened and exhibit a characteristic 'doming' appearance during diastole, classic for rheumatic mitral stenosis. Similarly, the tricuspid valve leaflets demonstrate matching morphological changes, including thickening and diastolic doming, indicative of concurrent tricuspid stenosis. Measurement calipers (labeled 1 and 2) are visible across the dilated atria, with values of 5.8 cm and 4.5 cm recorded in the upper left corner. The image illustrates multi-valvular rheumatic heart disease involving both the left-sided and right-sided chambers, resulting in atrial enlargement secondary to obstructive valvular pathology. This image is an essential educational tool for identifying the echocardiographic hallmarks of chronic rheumatic valvulitis and assessing cardiac chamber dimensions in the setting of severe stenosis.
🔴 Rheumatic Fever - Complete Microbiology Notes for Exam
Sources: Medical Microbiology 9e | Robbins & Kumar Basic Pathology | Goldman-Cecil Medicine | Sherris & Ryan's Medical Microbiology | Harrison's Principles of Internal Medicine 22E
1. DEFINITION
Key rule: ARF follows THROAT infections with GAS only - NOT skin infections (pyoderma/impetigo). This is a critical exam distinction.
2. THE CAUSATIVE ORGANISM
Streptococcus pyogenes (Group A Streptococcus - GAS)
| Property | Detail |
|---|---|
| Gram stain | Gram-positive coccus in chains |
| Lancefield group | Group A (Lancefield classification based on C carbohydrate) |
| Hemolysis | Beta-hemolysis (complete hemolysis on blood agar) |
| Key virulence factor | M protein - anti-phagocytic, main rheumatogenic antigen |
| Rheumatogenic M types | Types 1, 3, 5, 6, 18 (specific types associated with RF) |
| Enzyme marker | Produces Streptolysin O (detected as ASO titer in patients) |
| Other enzymes | Streptolysin S, Streptokinase, DNase B, Hyaluronidase, Erythrogenic toxin |
Exam pearl: NOT all GAS strains cause RF - only rheumatogenic M serotypes. Nephritogenic strains (causing glomerulonephritis) are DIFFERENT M types.
3. EPIDEMIOLOGY
| Feature | Detail |
|---|---|
| Peak age | 5-15 years (school-age children) |
| Sex | Equal in males and females (RF); RHD more common in women |
| Season | Cooler months (mirrors streptococcal pharyngitis) |
| Socioeconomic | Overcrowding, low income = higher risk |
| Risk after untreated GAS pharyngitis | ~1-3% (only minority develop RF) |
| Developing countries | ~100 cases per 100,000 children/year |
| Recurrence | High risk with each subsequent GAS infection (if no prophylaxis) |
| Attack rate highest in | Patients with severe pharyngitis (though 1/3 have mild/asymptomatic infection) |
4. PATHOGENESIS - MOLECULAR MIMICRY 🔑
Group A Streptococcus pharyngitis
↓
GAS releases M protein antigen
↓
Immune system generates antibodies + T cells against M protein
↓
MOLECULAR MIMICRY:
M protein shares epitopes with human proteins
↓
Anti-M protein antibodies cross-react with:
• Cardiac myosin → MYOCARDITIS
• Sarcolemmal membranes → ENDOCARDITIS/VALVULITIS
• Synovium/articular cartilage → ARTHRITIS
• Basal ganglia → CHOREA
• Skin proteins → SUBCUTANEOUS NODULES
Key Immune Mechanisms
| Mechanism | Effect |
|---|---|
| Molecular mimicry (Type II hypersensitivity) | Antibodies cross-react with host tissues |
| Antibody-mediated | Complement activation + macrophage recruitment → tissue injury |
| T-cell mediated | CD4+ TH1 responses → macrophage activation → Aschoff bodies |
| Immune complexes (Type III) | Deposited in joints → arthritis; small vessels → skin lesions |
| Chorea mechanism | Antibody binding to basal ganglia |
Why the 2-3 week delay? Because it takes 2-3 weeks to generate an immune response. By the time symptoms appear, streptococci are completely absent from the lesions.
Why only ~1-3% develop RF? Genetic susceptibility - B-lymphocyte alloantigen occurs 4-5 times more frequently in RF patients vs. general population.
5. MORPHOLOGY / PATHOLOGY
The ASCHOFF Body (Pathognomonic!) 🔑
| Feature | Detail |
|---|---|
| What it is | Discrete inflammatory granuloma-like focus in myocardial interstitium |
| Composition | Lymphocytes (T cells) + plasma cells + plump activated macrophages |
| Special cell | Anitschkow cells (= "caterpillar cells") |
| Anitschkow cell | Large activated macrophage with wavy/caterpillar-shaped chromatin (centrally condensed) |
| Also called | "Owl-eye cells" or "caterpillar cells" |
| Central zone | Fibrinoid necrosis |
| Location | Myocardial interstitial connective tissue |
| Significance | Found in ALL 3 layers → supports pancarditis diagnosis |
PANCARDITIS - All Three Layers Affected
| Layer | Pathology | Features |
|---|---|---|
| Pericardium | Fibrinous pericarditis | "Bread-and-butter" appearance; resolves without sequelae |
| Myocardium | Myocarditis | Aschoff bodies in interstitium; scattered |
| Endocardium | Valvulitis + small vegetations | Fibrinoid necrosis along valve closure line |
Valve Changes
- Small, 1-2 mm verrucous vegetations along the line of closure of valve leaflets (NOT destructive like IE)
- Fibrinoid necrosis of valve leaflets
- Mitral valve most commonly affected
- Fibrous thickening + fusion of valve leaflets
- Commissural fusion → mitral stenosis ("fish-mouth" or "buttonhole" appearance)
- Fusion and shortening of chordae tendineae
- Neovascularization of valve
6. CLINICAL FEATURES
Timeline
- ARF develops ~2 weeks after acute streptococcal pharyngitis
- Symptoms persist 2-4 weeks
- Carditis resolves or progresses over months-years
Manifestations - Frequency
| Feature | Frequency |
|---|---|
| Fever | >90% |
| Large-joint migratory polyarthritis | ~75% |
| Carditis (pancarditis) | >50% |
| Sydenham's chorea | ~30% |
| Subcutaneous nodules | <10% |
| Erythema marginatum | <10% |
7. REVISED JONES CRITERIA (Diagnosis) 🔑
- Initial ARF: 2 Major, OR 1 Major + 2 Minor
- Recurrent ARF: 2 Major, OR 1 Major + 2 Minor, OR 3 Minor
MAJOR Criteria - "JONES" Mnemonic
| Letter | Major Criterion | Key Details |
|---|---|---|
| J | Joints (Migratory Polyarthritis) | Large joints (knees, ankles, elbows, wrists); migratory; sterile synovial fluid; responds rapidly to NSAIDs |
| O | Oh my heart (Carditis) | Clinical and/or subclinical (echocardiographic) valvulitis; pancarditis; most common = mitral regurgitation |
| N | Nodules (Subcutaneous) | 0.5-2 cm; painless; over bony prominences/extensor tendons |
| E | Erythema marginatum | Pink, non-pruritic, blanching macules/papules with serpiginous border; trunk + proximal limbs; spares face |
| S | Sydenham's Chorea | Involuntary, non-rhythmic, purposeless movements; more on one side; stops during sleep; "St. Vitus Dance" |
Memory trick: "JONES" = Joints, Oh-heart, Nodules, Erythema, Sydenham
MINOR Criteria
| Minor Criterion | Low-Risk Population | Moderate/High-Risk |
|---|---|---|
| Arthralgia | Polyarthralgia | Monoarthralgia |
| Fever | ≥38.5°C | ≥38.5°C |
| Elevated inflammatory markers | ESR ≥60 mm/h AND/OR CRP ≥3.0 mg/dL | ESR ≥30 mm/h AND/OR CRP ≥3.0 mg/dL |
| Prolonged PR interval | Yes (unless carditis = major criterion) | Yes |
Evidence of Preceding GAS Infection (ESSENTIAL - without this, Jones criteria alone are insufficient)
- Positive throat culture for GAS
- Rapid streptococcal antigen test (Rapid Strep Test)
- Elevated/rising streptococcal antibody titers:
- ASO (Anti-Streptolysin O) - most commonly used
- Anti-DNase B - more sensitive for skin infections
- Anti-hyaluronidase
Exam tip: ASO titer stays elevated for weeks-months after infection. Absence of elevated ASO = strong evidence AGAINST RF.
8. LABORATORY FINDINGS
| Test | Finding |
|---|---|
| ASO titer | Elevated (most important serologic test) |
| Anti-DNase B | Elevated |
| Throat culture | May be positive for GAS |
| ESR | Elevated |
| CRP | Elevated |
| WBC | Leukocytosis |
| CBC | Normochromic, normocytic anemia |
| ECG | Prolonged PR interval (first-degree AV block) - minor criterion |
| Synovial fluid | Sterile, lymphocyte predominant |
9. RHEUMATIC HEART DISEASE (Chronic Sequelae)
| Feature | Detail |
|---|---|
| Valve order of involvement | Mitral (100%) > Aortic (20-30%) > Tricuspid (15-40% histologically) > Pulmonary (rare) |
| Most common lesion | Mitral regurgitation (acute) → Mitral stenosis (chronic/recurrent) |
| Mitral stenosis | RHD is the #1 worldwide cause of acquired mitral stenosis |
| Progression to RHD | 35-70% of ARF patients with carditis |
| Peak severity | Third and fourth decades of life |
| In developing countries | Leading cause of bacterial endocarditis and cardiovascular mortality in young people |
Critical exam fact: "Rheumatic heart disease is essentially the only cause of acquired mitral stenosis" - Robbins
10. TREATMENT
Acute Phase
| Goal | Treatment |
|---|---|
| Eradicate GAS from throat | Benzathine penicillin G IM 1.2 million units (single dose) OR oral penicillin V 10 days |
| Arthritis | Aspirin 80-100 mg/kg/day, OR Naproxen; NSAIDs |
| Carditis/heart failure | Diuretics, ACE inhibitors/ARBs, bed rest; steroids in severe cases |
| Chorea | Usually self-limited; resolves in weeks-months |
Prophylaxis (Prevention of Recurrence) 🔑
| Duration of Secondary Prophylaxis | Condition |
|---|---|
| 10 years or until age 21 (whichever is longer) | No carditis |
| 10 years or until age 21 (whichever is longer) | Carditis, no residual valve disease |
| 10 years or until age 40 (whichever is longer) | Persistent valvular disease |
| Lifelong | Severe valvular disease / valve surgery |
Why lifelong prophylaxis matters: Each recurrence of RF can cause additional valve damage. Prevention of GAS throat infection = prevention of further deterioration.
11. COMPARISON: RF vs. GLOMERULONEPHRITIS (Post-GAS Complications)
| Feature | Rheumatic Fever | Acute Post-Streptococcal Glomerulonephritis |
|---|---|---|
| Cause | GAS | GAS |
| Follows | Pharyngitis ONLY | Pharyngitis OR skin infection |
| M types | Rheumatogenic (1,3,5,6,18) | Nephritogenic (types differ) |
| Mechanism | Molecular mimicry (Type II + T cell) | Immune complex deposition (Type III) |
| Organ | Heart, joints, skin, brain | Kidney (glomeruli) |
| Recurrence with GAS | YES - very high | Low (one episode usually protective) |
| Prophylaxis | Required (prevents recurrence) | Not typically required |
| Prognosis | Cardiac damage cumulative | Children recover well; adults may progress |
12. QUICK EXAM MEMORY AIDS
Major vs. Minor Criteria
MAJOR = "JONES" = Joints, Oh-heart (carditis), Nodules, Erythema marginatum, Sydenham's chorea
MINOR = "FEP" = Fever, ESR/CRP elevated, PR prolonged (+ arthralgia if arthritis not a major criterion)
Key "ONLY" Facts (Exam Favorites)
- RF follows pharyngitis only (not skin infection)
- RHD is the only common cause of acquired mitral stenosis
- Aschoff body is pathognomonic for RF carditis
- Streptococci are absent from lesions when symptoms appear
Organism Identification in Exam Questions
- "School-age child, sore throat 2-3 weeks ago, now fever + migratory joint pain + new murmur" → ARF
- "ASO titer elevated" → Recent GAS pharyngitis
- "Pancarditis + caterpillar cells in myocardium" → Aschoff bodies in RF
- "Fish-mouth mitral valve" → Chronic rheumatic heart disease
- "Benzathine penicillin every 4 weeks for years" → Secondary prophylaxis for RF
13. SUMMARY FLOWCHART
GAS (S. pyogenes, Group A β-hemolytic Strep) Pharyngitis
↓
Rheumatogenic M protein
↓
Immune response (antibodies + T cells)
↓
Molecular Mimicry
↙ ↓ ↘
Heart Joints Brain/Skin
(Carditis) (Arthritis) (Chorea + Erythema)
↓
Aschoff bodies (pathognomonic)
↓
Pancarditis → Valvulitis
↓
Healing + Scarring (with repeated attacks)
↓
RHEUMATIC HEART DISEASE
(Mitral stenosis = most classic)