Bacterial Endocarditis

Pathophysiology of Bacterial Endocarditis

bacterial endocarditis is:

1) formation of bacterial vegetative thombi on cardiac valves
2) most commonly involved valves in bacterial endocarditis are aortic and mitral in non-IV drug abusers; tricuspid in IV drug abusers
3) affected valves “decay” with rupture and subsequent congestive heart failure
4) significant morbidity and mortality in bacterial endocarditis also arise from detachment of vegetations with embolization to brain, kidneys, lungs, gastrointestinal tract, and spleen with infarction and abscess formation
5) can have an acute (Staphylococcus aureus, beta-hemolytic streptococcus, of S. pneumoniae) or subacute presentation

Signs and Symptoms

1) fever
2) anorexia
3) weight loss
4) new onset heart murmurs
5) subungual hemorrhages
6) petechiae
7) clubbing of fingers
8) splenomegaly
9) dyspnea (due to PE or cardiac failure
10) neurologic deficits (due to CNS emboli0
11) Osler’s nodes (bluish red nodules on digits, palms, and soles
12) Janeway’s spots (small hemorrhages on palms and soles
13) Roth’s spots (whitish spots in retina)

Characteristic Test Findings

Laboratory

1) anemia
2) increased sed rate
3) circulating immune complexes
4) rheumatoid factor (50%)
5) increased C-reactive protein
6) microscopic hematuria

Echocardiography

7) used for diagnosis of lesions

Histology/Gross Pathology

1) vegetations in bacterial endocarditis are a mixture of bacteria, fibrin, and platelets
2) kidney shows focal embolic glomerulonephritis with immune complex deposition, causing a “flea-bitten” appearance
3) denuded endothelium at high pressure jets or low-pressure areas of cardiac defects is the first step in lesion propagation
4) virulent organisms can attach directly to bare areas

Associated Condtions

increased incidence in bacterial endocarditis in

1) rheumatic heart disease
2) congenital heart defects (patent ductus arteriosus, VSD, tetralogy of Fallot)
3) IV drug abuse
4) dental procedures
5) instrumentation of body orifices (endoscopy, catheter insertion)
6) elderly
7) diabetes
8) pregnancy
9) indwelling prostheses

Inheritance/Epidemiology

1) 6/100,000 in USA per year
2) mortality is 25-50% (with treatment)
3) 15% have negative blood cultures

Treatment

1) aggressive and prolonged antibiotic treatment (minimum 4 weeks)
2) surgical repair of deteriorating valve

Tips for USMLE

1) if a 72 year old diabetic man with mild aortic stenosis has a cystoscopy and 14 days later develops a low-grade feer, malaise, elevated sed rate, and weakness in his right hand, think bacterial endocarditis