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)
Why should digoxin be used cautiously with myocarditis?
Digoxin increased the expression of pro inflammatory cytokines in increased mortality in experimental myocarditis
What are risk factors for thromboembolism in dogs with infective endocarditis?
- Mitral valve envolvement
- Large mobile vegetative lesion (> 1-15 cm)
- Increasing lesion size during antimicrobial therapy
What kind of murmur is present with infective endocarditis?
Diastolic murmur - low intensity with bounding pulses
What was associated with prolonged survival in patients with IE in recent literature?
Antithombotics
