An overview of echocardiographic features for the diagnosis of infective endocarditis.
Risk Factors
- Risk factors – prosthetic valves, intracardiac devices, unrepaired cyanotic congenital heart disease, previous history, rheumatic heart disease, IVDU. 50% cases no known history of valve disease, cardiac transplantation with subsequent development valvulopathy.
Organisms
- Organisms- Most common Staphylococcus (S. aureus, CNS) followed by Streptococcus (S. viridans, S. pyogenes) and Enterococcus.
- Gram negative – HACEK group (haemophilus species, Aggregatibacter [formerly Actinobacillus] actinomycetemcomitans, Cardiobacterium hominis, Eikenella corrodens, and Kingella kingae), and Tropheryma whipplei.
- Blood culture negative organisms (2.5 to 20%) -Bartonella, Brucella, Coxiella burnetii, Aspergillus
Modified Duke’s Criteria
- 2 major criteria, or
- 1 major and 3 minor criteria, or
- 5 minor criteria
Major criteria
(ref LITFL http://lifeinthefastlane.com/ccc/infective-endocarditis-echocardiography/)
- Positive blood culture for Infective Endocarditis
Typical microorganism consistent with IE from 2 separate blood cultures, as noted below:
— viridans streptococci, Streptococcus bovis, or HACEK group, or
—community-acquired Staphylococcus aureus or enterococci, in the absence of a primary focus
or Microorganisms consistent with IE from persistently positive blood cultures defined as:
— 2 positive cultures of blood samples drawn >12 hours apart, or
— all of 3 or a majority of 4 separate cultures of blood (with first and last sample drawn 1 hour apart) - Evidence of endocardial involvement
Positive echocardiogram for IE defined as :
— oscillating intra-cardiac mass on valve or supporting structures, in the path of regurgitant jets, or on implanted material in the absence of an alternative anatomic explanation, or
— abscess, or
—new partial dehiscence of prosthetic valve - New valvular regurgitation (worsening or changing of preexisting murmur not sufficient)
Minor criteria
- Predisposition: predisposing heart condition or intravenous drug use
- Fever: T> 38.0° C
- Vascular phenomena: major arterial emboli, septic pulmonary infarcts, mycotic aneurysm, intracranial haemorrhage, conjunctival haemorrhages, and Janeway lesions
Vascular embolus
- Immunologic phenomena: glomerulonephritis, Osler’s nodes, Roth Spots, and rheumatoid factor
- Microbiological evidence: positive blood culture but does not meet a major criterion as noted below¹ or serological evidence of active infection with organism consistent with IE
- Echocardiographic findings: consistent with IE but do not meet a major criterion as noted above
TTE or TOE?
A TTE should almost always be the first line echo of choice and this is consistent with international guidelines.
A TOE is needed if :–
- Prosthetic valve or intracardiac device (pacemaker, AICD, VADs)
- Poor quality TTE
- TTE negative and still high clinical suspicion of IE.
If the TTE image if of excellent quality, a TOE may not be needed or if the risks associated with the TOE outweigh the benefit ( eg palliation). A nuclear med scan could be considered if the echo is negative and there is still clinical suspicion of IE. It is important to review previous echoes, if available, as not all intracardiac masses seen, are considered vegetations. More importantly, clinical findings need to support the diagnosis.
Echo Findings
Location, movement, size, complications- valve destruction +/- regurgitation, perivalvular extension
Key features
- Usually upstream from valves. Right sided lesions for at risk patients.
- Independent motion or oscillitating of mass to cardiac structures and cycle “floppy doppy”
- More than 1cm is associated with increase risk of embolization
- Assess for complications
Complications:
-Assess for SPREAD – vegetation on other valves; perivalvular extension- abscess or fistula (Colour Doppler communication between two neighbouring cavities through a perforation).
Abscess appears as non- homogenous, hypoechoic “space” with surrounding echogenicicity, more common in aortic or prosthetic valves.
-VALVE DESTRUCTION – regurgitation of affected valve, prolapse, perforation (Interruption of endocardial tissue continuity traversed by colour Doppler), chordae or papillary rupture
Excised mitral valve following infective endocarditis papillary rupture.
Pitfalls
Independent motion can be quite difficult to assess as other lesions can mimic vegetations eg ruptured chordae, redundant leaflets, papillary fibroelastomas, Lambl’s Excrescences. Useful clues would include: Atypical location (i.e. downstream of valve, LVOT attachment), Hair-like strands with narrow attachment, Lack of associated regurgitation / flow disturbance, Very bright reflectance (i.e. calcium/pericardium). When there is uncertainty, correlate echo findings with clinical picture, look at previous echo scans, and repeat echo about a week later if indicated.
It is important to look at other views of the affected structure.
Prosthetic valve endocarditis
Can be difficult to diagnose as it does not play by the rules.
- lower incidence of vegetations
- higher incidence of abscesses/perivalvular complications
- Mechanical valves: infection usually between sewing ring & annulus
- Bioprosthetic valves: leaflets affected more
- Sensitivity for endocarditis lower than for native valve disease
References:
- Hoen B, Duval X. N Engl J Med 2013;368:1425-1433.
- Escardio.org
- Recommendations for the practice of echocardiography in infective endocarditis Gilbert Habib, European Heart Journal – Cardiovascular ImagingMar 2010,11(2)202-219
Tags: abscess Duke's emboli fistula Infective endocarditis Lambl’s Excrescences papillary fibroelastomas prosthetic valve vegetation
