INFECTIVE ENDOCARDITIS

Patients admitted to intensive care units often have fevers and positive blood cultures.  One of the concerns associated with confirmed bacteremia is the presence of endocarditis as a consequence of the bacteremia, or even as the source. This is especially true of the organisms grown on blood cultures have a preponderance to form vegetations on cardiac valves. 

They may also present with life-threatening refractory heart failure, strokes, mesenteric ischemia and critical limb ischemia.

Here we delve into the basic principles of infective endocarditis assessment. Given several nuances with making this diagnosis (e.g. native vs. prosthetic valves, presence of aortic root abscesses, etc.), when in doubt, consult with your local echocardiographer.

Given there are 4 main native valves (aortic, mitral, tricuspid, pulmonic) of the heart, they can become infected (e.g. bacterial, fungal, marantic, etc.), with a diagnosis known as endocarditis.

We will overview the principles of endocarditis interrogation, including:

  • Views (mid-esophageal 4-chamber, mid-esophageal long-axis, RV inflow-outflow, deep trans-gastric apical 5-chamber views)
  • Sweeping of the valve (to interrogate for IE)
  • Assessment/measurement of vegetations
  • Colour and spectral Doppler interrogations
  • Determining valvular endocarditis sequelae

2D/COLOUR/SPECTRAL DOPPLER/SWEEPING

  • We interrogate all valves of endocarditis with the following principles:
    • 2D structures:
      • Focus on the valve of interest
      • Zoom in on the valve structure
      • Sweep through the valve structure (by turning the probe clock-wise and counter-clockwise, and pulling/pushing the probe inward/outward or up/down) to ensure that the assessment for vegetations is THOROUGH 
      • Capture still images of the vegetation (caliper measurements)
  • Colour Doppler
    • Turn on colour box – keeping the Nyquist limit to:
      • High [~60-70cm/s] – for looking at regurgitant lesions
      • Remember to place the colour box across the valve, and have the box big enough to interrogate the entire chamber where regurgitation occurs
  • Spectral Doppler (continuous wave [CW])
    • Place CW across the center of most of the valve structure (to assess both for stenotic and regurgitant lesions)
    • AI CW assessed from deep TG A5C
    • MR and TR assessed best from ME4C

Assessment/measurement of vegetations

  • The best windows to assess for IE:
    • AV: ME LAX (~120 degrees)
    • MV: ME 4C (~0 degrees)
    • TV: ME 4C (~0 degrees)
    • PV: ME RV Inflow/Outflow or ME AV SAX (~60-90 degrees)
  • Vegetations can be measured using calipers (still image)
  • Large, mobile vegetations (>1cm) are considered higher risk for embolism (potential for earlier surgical decision)
  • Vegetations with INCREASED dimensions on serial TEE despite antimicrobial therapy = sign of UNCONTROLLED infection
  • TEE  is  the  method  of choice  for  measuring  the  size of  the  vegetation  and for  follow-up.

Colour and spectral Doppler interrogations

  • Vena contracta (VC): width of the regurgitant jet size –  approximates regurgitant orifice
    • Measure where the flow across the valve is preceded by a convergence zone – followed by a widening jet (hourglass appearance)
    • Tiny measurement – small errors lead to big discrepancies in severity
    • Not useful when multiple jets present
    • Mild: < 3mm, moderate: 3-7mm, severe: >7mm (remember to ZOOM on STILL image of colour)
  • Regurgitant lesions (colour/Spectral cutoffs):
    • Severe AI: colour occupies >65% of LVOT, diastolic flow reversal seen in descending aorta
      • Pressure half-time (PHT): CW
        • Mild: >500ms
        • Moderate: 200-500ms
        • Severe: <200ms
  • Severe MR: colour occupies >40% of LA, pulmonic vein flow reversal during systole, jet hits back wall of LA (e.g. Coanda effect)
  • Severe TR: colour occupies > 40% of RA, jet hits back wall of LA, hepatic vein flow reversal during systole
  • Severe PI: large colour jet width, brief duration, dense steep deceleration, early termination of diastolic flow, greatly increased pulmonary flow
    • Pressure half-time (PHT): CW
      • Mild: >1100ms
      • Moderate: 570-1100ms
      • Severe: <570ms

Determining valvular endocarditis sequelae

  • Vegetations  are  typically attached  on  the  low-pressure side  of the valve, but may be located anywhere on the valve or sub-valvular structure, mural endocardium, cardiac chambers, or aorta
  • When   large   and   mobile (> 1 cm),   vegetations  are more prone  to  embolism
  • Destructive  valve  lesions  are  very  frequently  associated  with vegetations (but can still be observed alone). 
  • They  may  provoke valve aneurysm, perforation, prolapse, chordae/papillary muscle rupture 
  • The usual final consequence of these lesions is severe valve regurgitation & heart failure 
  • Another anatomical  feature  of  IE  is  abscess  formation (Abscesses   are   more   frequent   in   aortic   and   prosthetic IE, and   may   be   complicated  by   pseudoaneurysm   or fistulization)

INFECTIVE ENDOCARDITIS TUTORIAL

In this tutorial, we will breakdown performance and interpretation of IE interrogation.

references

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