JC05 - Valvular heart disease Flashcards
(58 cards)
Pathophysiology of acute and chronic rheumatic fever
Acute: molecular mimicry
- Delayed immune response to infection with certain strains of Group A Strep
- Cross-reactiveness targeting cardiac proteins (anti-M)
- Result: inflammation in ALL layers: endocardium, myocardium and pericardium
Chronic:
- Repeated ARF attacks over decades → progressive fibrosis and fusion of heart valves
S/S of acute rheumatic fever
- Preceded by Strep throat 2-3m weeks before
- Fever, anorexia, lethargy
- Pancarditis: SOB, Palpitation, Angina, Murmurs
- Associated: Arthritis, Skin (subcutaneous nodules), Sydenham’s chorea
- Valvular involvement: Commonly Mitral (MS > MS+MR > MR) and Aortic
Type of murmur associated with acute rheumatic fever
Transient MR/AR murmur, MDM at apex (Carey-Coombs murmur)
Name of diagnostic criteria for rheumatic fever
Jone’s criteria
2 major manifestation or 1 major + 2 minor + evidence of preceding streptococcus infection
Investigation and treatment of acute rheumatic fever
Ix:
□ Throat swab (rarely positive) and serology for ↑ASO titres
□ ESR/CRP
□ Echocardiogram: MR ± AR, MVP, pericardial effusion
Tx:
Acute: single dose IM benzylpenicillin
Heart valves affected by rheumatic fever
Site: MV alone (most common)
AV+MV, AV alone
TV (rare)
Pathophysiology of IE
Endothelial damage → attract platelet/fibrin deposits → protects vs host defense
→ favours colonization by blood-borne organisms
Fibrin/platelet accumulation → growth of vegetation → obstruction/embolism
Infection destroy adjacent tissues → abscess formation
Risk factors of IE
Prior rheumatic HD (30%) Normal valves (40%) IVDU (10%) Congenital defects (10%) Prosthetic heart valve (10%)
Complications of IE
□ Systemic infection due to continuous bacteraemia
□ Valvular heart disease due to vegetation formation
□ Septic embolization due to dislodging of vegetation materials
□ Immune complex deposition due to systemic inflammatory response
Groups of pathogens that cause IE
S. aureus: most common
Viridans strep: 2nd most common cause (eg. S. sanguis, S. mutans)
Group A/B streptococci, i.e. S. pyogenes and agalactiae
Group D streptococci, i.e. Enterococcus, S. bovis
HACEK: group of slow-growing fastidious G- bacilli
Others:
- Animal contact: Coxiella burnetti (Q fever), Brucella
- Fungal (IV line, immunocompromised)
- Coagulase -ve staphylococcus (prosthetic valve)
Primary sources of bacteria that cause IE
S. aureus - skin/ skin infection/ IVDU
Viridans strep. - Oropharyngeal commensal, dental procedure, brushing
Group D strep. - GI/ GU tract diseases [classically a/w colonic ulcerative lesions, eg. CA colon, ulcerative colitis]
HACEK - oropharynx
Antibiotics sensitivity of causative bacteria of IE
S. aureus: variable, often penicillin-resistant
Viridans strep, Group A/B strep - Penicillin
Group D strep:
- S. bovis: penicillin
- Enterococcus: penicillin-resistant, need aminoglycoside
Staphylococcus/ HACEK: variable, often penicillin-resistant
Causes of negative blood culture for IE
Culture-negative endocarditis:
- Inadequate technique
- Prior antibiotics
- Fastidious organisms (require prolonged culture) e.g. Mycoplasma, HACEK
- Fungal (mainlining addicts, immunocompromised)
May take additional 3 cultures in these cases
Causes of Non-bacterial thrombotic endocarditis
Deposition of sterile thrombus on valve leaflets
Causes: metastatic malignancy (marantic, esp mucin-producing adenocarcinoma), thrombophilia, SLE Libman-Sacks endocarditis
S/S of systemic infection complication in IE
S/S:
- Persistent fever
- Chills and rigors
- General malaise
- weight loss
- Pallor
S/S of Cardiac involvement in IE
S/S
- Chest pain
- S/S of heart failure
- Changing murmurs (esp regurgitation murmurs)
S/S, associated conditions for Septic embolism due to IE
Conditions:
- Stroke
- Brain abscess
- Cold limbs
- Splenic/renal/visceral infarcts/abscesses
S/S:
- Skin petechiae
- Roth spots
- Janeway lesions
- Splinter haemorrhage
- Splenomegaly
S/S, associated conditions for systemic immune deposition due to IE
associated conditions:
- Arthralgia/myalgia
- Tenosynovitis
- Glomerulonephritis
P/E:
- Arthritis
- Uraemia
- Vascular phenomena
- Osler’s nodes
- Finger clubbing
Sample collection method for microbiological workup of IE
3 venous cultures taken at different sites, separated by ≥0.5h + 3 cultures if initially negative (esp if prior Abx)
Microbiological diagnosis:
>2 of 3 venous blood cultures(taken at different sites and separated by at least 0.5h) showingpersistent bacteraemia of typical organisms:
Imaging modalities for IE
Indications for each approach
Trans-thoracic echo - first line for screening
Trans-esophageal echo - see vegetation, cardiac complications, first line for prosthetic valve
- Indications:
(1) Prosthetic valve/ intracardiac device (difficult to visualize)
(2) TTE non-diagnostic or –ve but high clinical suspicion
(3) TTE +ve but high risk for complications
First-line investigations for IE
Blood culture
Echocardiogram
Blood: leukocytosis, ESR, CRP
Urine: proteinuria, haematuria, pyuria, RBC casts
ECG: AV block or conduction delays
CXR: HF, cardiomegaly, septic pulmonary emboli
Clinical diagnostic criteria for IE
Duke’s criteria: Pathologic + Clinical criteria:
Diagnosis made when one of following is met
□ Pathologic criteria:
→ Micro-organisms demonstrated in a vegetation
→ IE confirmed by histology
□ Clinical criteria:
→ Definite IE = 2 major OR 1 major + 3 minor OR 5 minor
→ Possible IE = 1 major + 1 minor OR 3 minor
List all major criteria in Duke’s criteria for IE
1) Positive blood culture: demonstrate persistent bacteria
→ Typical organisms grown in 2 separate blood C/ST or >12h apart
→ Skin contaminants grown in 3 or majority of ≥4 separate C/ST (with 1st and last drawn ≥1h apart)
→ Coxiella burnetii: single +ve C/ST or phase I IgG titre >1:800
2) Evidence of endocardial involvement:
→ Echo: vegetation, abscesses or prosthetic valve dehiscence
→ New valvular regurgitation
List all minor criteria in Duke’s criteria for IE
□ Predisposition: VHD/cardiac conditions or IVDU
□ Fever ≥38.0oC
□ Vascular phenomena, eg. embolism, septic PE, mycotic aneurysm, Janeway lesion, conjunctival haemorrhage
□ Immunological phenomena, eg. GN, Osler’s nodes, Roth spots, ↑RF
□ Suggestive blood cultures: organism grown but does not meet major criterion or serologic evidence
of active infection with organism consistent with IE
