Acquired Valvular Disease- Endocarditis Flashcards
describe infective endocarditis
- inflammation of the endocardial surface of the heart with invasion by an infectious agent (bacteria, rickettsial organisms, fungal organisms)
- endocardial surface includes: surface of the valves, mural/wall, edges of septal defects, and chordae tendinae
- synonyms:
-infective endocarditis: microbial infection (bacterial, fungal, etc.)
-bacterial endocarditis: bacterial infection
-vegetative endocarditis: vegetations (composed of platelets, fibrin, microorganisms, and inflammatory cells), adherent
contrast endocardiosis to endocarditis
endocardiosis: degenerative/myxomatous
-gross lesion: smooth, glistening, nodular thickening of valve margins
endocarditis: inflammatory/infectious
-gross lesion: friable, rough, irregular yellowish raised proliferative lesions (vegetative lesions)
describe incidence/prevalence of endocarditis
cows: relatively common
-important cause of hardware disease
dogs: uncommon diagnosis
-middle-aged to older, medium to large breed, purebred dogs
horses, pigs, camelids: sporadic: can be mural (wall) in camelids and cattle
cats: rare
avian: very few cases documented
describe pathogenesis of endocarditis
- endothelial damage/injury:
-collagen exposure due to endocardial damage
-healthy endothelium is resistant!! to bacterial colonization, so injury is required vie direct trauma, inflammation, or turbulent bloodflow to allow colonization
-underlying cardiac defect is NOT present is 87-94% of vet cases, of those with lesions, 75% have congenital subaortic stenosis
-endocardiosis is NOT a predisposing factor - formation of non-bacterial thrombotic endocarditis (NBTE):
-ECM, thromboplastin, and tissue factor trigger coagulation and formation of coagulum (fibrinogen, fibrin, platelet proteins)
-body is just trying to heal itself! - bacteremia:
-can be transient or persistent
-predisposing events: chronic infections, GI/GU tract surgery, immunosuppression (systemic illness: DM, cushings, or iatrogenic via corticosteroids) - bacterial colonization of NBTE:
-circulating bacteria adhere and attach to the thrombus
-bacteria that most easily adhere to valves are most commonly involved (staph, strep)
-bacteria have surface proteins that bind fibrin/fibrinectin - activation of clotting cascade and lesion extension:
-bacteria become embedded and trigger tissue factor production and induce platelet aggregation
-this forms a protected environment for bacterial growth where they are shielded from host defenses and antimicrobial drug penetration
describe lesion pathology in small animals
- almost exclusively mitral and aortic valves (left sided valves)
- lesions most often associated with lower-pressure side of valve/lesions
describe lesion pathology in large animals
cows: right sided valves, esp tricuspid!
-FOR SURE ON EXAM!!!!!!!!!!
-due to dirty environment venous flow potentially
horses, pigs, camelids: left sided valves»_space; right sided valves
-can be mural (or wall) as well
describe etiologic agents in small animals
- we only ID the agent in 60% of cases!
- commonly cultured in dogs:
-staphylococcus: aureus, intermedius
-streptococcus: canis, bovis
-E. coli
-bartonella spp. - commonly cultured in cats:
-pasteurella
don’t memorize bacteria according to Hammond!! (just have the MSCRAMMS, ability to stick to scab)
describe bartonella endocarditis in small animals
unique!
- has a strong predilection for aortic valve
- associated with poorer outcome: more CHF, earlier death
- affected dogs are usually afebrile
-only 20% have fever - difficult to isolate from blood
-responsible for up to 20% of cases that are culture negative with routine methods
describe etiologic agents in large animals
cattle:
-trueperella pyogenes: 80% of cultures
-streptococcus spp.
-E. coli
horses:
-actinobacillus
-streptococcus spp.
-staphylococcus spp.
pigs:
-streptococcus spp.
describe cardiac consequences of infective endocarditis (local disease)
- valve leaflet injury:
-insufficiency: most common
–bacterial enzymes destroy affected valve, leading to necrosis/perforation that leads to valvular regurgitation, followed by volume overload, left heart enlargement, and CHF
-obstruction/stenosis: increases cardiac workload, resulting in concentric hypertrophy
- extension of infection into surrounded tissues
-AV/bundle branch blocks
-abscess formation
-purulent pericarditis
-myocarditis
-intracardiac perforation
describe systemic consequences/metastatic disease of infective endocarditis
- embolic disease:
-end organ infarction/metastatic infection
–in 84% of cases at necropsy, most commonly in the kidney and spleen
–increased risk: larger, mobile vegetations (>10-15mm) or mitral valve involvement - immune-mediated disease
-cell mediated and humoral immune responses cause circulating immune complex deposition and complement activation, resulting in inflammatory tissue damage
-most commonly affected: joints (polyarthritis), kidneys (glomerulonephritis) - renal failure: up to 33% of cases
-metastatic infection/infarction
-glomerulonephritis - septic shock
describe history and clinical findings of infectious endocarditis
- risk factor:
-prior or current infection
-immunosuppressive disease or drug history - fever
- constitutionally ill
- palpable joint effusion
- new heart murmur:
-ejection murmur: fever, increased slow, stenotic semilunar valve from large vegetation
-regurgitant murmur:
–AoV: diastolic, left base
–MV: systolic, left apex
–TV: systolic, right apex
- intermittent lameness
- signs of vasculitis (cutaneous hemorrhage, thrombosis)
- other possible cardiac findings:
-tachycardia
-hyperkinetic pulses
-arrhythmia
-signs of CHF - lethargy, weight loss, inappetance, weakenss
SUPER vague, have to go hunting
describe diagnostics for IE
- CBC: variable
-leukocytosis
-anemia - serum biochem: variable
-azotemia
-elevated globulin - urinalysis:
-pyuria - modified Duke criteria: tells the probability that the patient has IE
-major criteria:
–positive echocardiogram: oscillating, vegetative lesion, erosive lesion, abscess
–new valvular insufficiency
–positive blood culture in at least 2 samples
minor criteria:
–fever
–presence of predisposing factors: med to large breed dog, suboartic stenosis
–evidence of systemic sequelae: thromboembolic disease, immune-mediated disease (polyarthritis, glomerulonephritis)
–positive blood culture not meeting major criteria
–bartonella serology
describe echocardiography for IE
- most important tool for antemortem dx of IE
- hyperechoic, oscillating, irregular-shaped (shaggy) mass adherent to endothelial cardiac surface
describe the modified duke criteria
- major criteria (FOR SURE KNOW THESE)
-positive echocardiogram: oscillating, vegetative lesion, erosive lesion, abscess
-new valvular insufficiency
-positive blood culture in at least 2 samples
- minor criteria:
-fever
-presence of predisposing factors: med to large breed dog, suboartic stenosis
-evidence of systemic sequelae: thromboembolic disease, immune-mediated disease (polyarthritis, glomerulonephritis)
-positive blood culture not meeting major criteria
-bartonella serology
definite: 2 major criteria OR 1 major + 3 minor OR 5 minor
