Endocarditis / myocarditis Flashcards
What are risk factors for mortality in infective endocarditis
- Aortic valve involvement
- Bartonella (because affects aortic valve)
- Use of glucocorticoids before treatment
- Thrombocytopenia
- High creatinine
- Thromboembolic disease
List antimicrobial options for infective endocarditis
- Strep / Staph: ampicillin +/- sulbactam IV then Clavamox (except MRSA: amikacin then doxycycline or chloramphenicol)
- Enteric species: amikacin and/or ampi-sulbactam then based on susceptibility
- Pseudomonas: amikacin or piperacillin-tazobactam then based on susceptibility
- Bartonella: amikacin then doxycycline and enrofloxacin +/- azithromycin
- Negative culture: amikacin and piperacillin-tazobactam then Clavamox and enro
- Recommended first 1-2 weeks given IV then continue for at least 6-8 weeks
Should use higher range of dose
Bacteridical agents preferred
List the modified Duke criteria for infective endocarditis
Major criteria:
- Positive echocardiogram (vegetative, oscillating lesion or erosive lesion or abscess)
- New valvular insufficiency
- More than mild aortic insufficiency in the absence of subaortic stenosis
- Positive blood cultures (≥ 2 positive with typical organism or ≥ 3 positive with skin contaminant)
Minor criteria:
- Fever
- Dog > 15kg
- Subaortic stenosis
- Thromboembolic disease
- Immune mediated disease (polyarthritis, glomerulonephritis)
- Positive blood cultures not meeting major criteria
- Bartonella serology > 1:1024
Diagnosis:
- Definite = pathology of valve, 2 major or 1 major + 2 minor
- Possible = 1 major + 1 minor or 3 minor
- Unlikely = other diagnosis or resolution in <4 days or no evidence at necropsy
What 2 valves are most commonly affected by infective endocarditis
Mitral and aortic
What are common consequences / complications of infective endocarditis
- CHF
- Immune mediated disease (polyarthritis 75% cases, glomerulonephritis 36% cases)
- Thromboembolism (septic or aseptic) mostly to spleen and kidneys (* risk factor = mitral valve involvement)
Describe the pathophysiology of infective endocarditis
- Valve endothelial injury -> exposure of extracellular matrix proteins, tissue factor, thromboplastin
- Deposition of platelets, fibrinogen and fibrin
- Adhesion of bacteria to fibronectin and fibrin, facilitated by MSCRAMM (microbial surface component recognizing adhesive matrix molecules)
- Proliferation of bacteria within the fibrinous vegetative lesion
Mechanisms of escape from immune system:
- Internalization in host cells (S aureus, Bartonella)
- Resistance to platelet bactericidal proteins
- Bacterial cluster in vegetative lesion inaccessible to phagocytes + poor blood supply to valvular leaflets
What are the most common etiologic agents of infective endocarditis
- Staphylococcus spp (S aureus, S pseudintermedius, coagulase neg Staph)
- Streptococcus spp (S canis, S bovis)
- E Coli
(Others: Enterococcus, Pseudomonas, Enterobacter, Pasteurella, Bartonella, etc)
What are predisposing factors of infective endocarditis
- Factors causing endothelial disruption: subaortic stenosis (MMVD not associated with IE)
- Sources of bacteremia: diskospondylitis, prostatitis, UTI, periodontal disease, indwelling catheters, pyoderma
(* dental prophylaxis not a predisposing factor in itself)
What are echocardiographic findings with infective endocarditis
- Hyperechoic, oscillating, irregularly-shaped mass adherent to valve endothelium (but distinct from it) => pathognomonic
- Possible valvular erosive lesions
- Valvular insufficiency
- Dilation of left atrium and ventricle (eccentric) only if chronic
What are 2 diagnostic tests to perform in case of suspected endocarditis
- Echocardiography
- Blood cultures (although negative in 60-70% of cases): aseptic collection of 3-4 blood samples of 5-10mL from different sites 30 min - 1h apart
- Also consider Bartonella serology +/- culture on special medium or PCR after incubation and enrichment
Name causes of infectious myocarditis
- Viral: parvovirus, Distemper rarely, West Nile, possibly FIV
- Protozoal: Chagas disease (Trypanosoma cruzi), Toxoplasma, Neospora
- Bacterial: can happen with any bacteria, mostly Staph and Strep + Rickettsia, Ehrlichia, Bartonella, Borrelia (Lyme), Leptospira
What disease can develop following parvovirus related myocarditis in puppies?
DCM
What agent can cause non-infectious myocarditis
Doxorubicin
True or false: Doxorubicin cardiotoxicity is reversible
False
What are criteria suggestive of myocarditis
- History (doxorubicin, travel history)
- Signalment (unusual breed for heart disease)
- ECG: conduction abnormalities +/- arrhythmias
- Echo: myocardial dysfunction (diffuse or regional) with or without heart enlargement
- Lab: leukocytosis, eosinophilia, elevated cTnI
+/- testing for infectious agents - Definitive diagnosis is based on histopath (endomyocardial biopsy or necropsy)
