Parasternal Short Axis – PSAX


PSAX (Parasternal Short Axis)

PSAX

Image from BSE website

From your best PLAX view rotate the probe 90 so the marker points towards the patient’s L shoulder. Sweep angle of probe to get views at aortic (anterior), MV, papillary and apex (posterior).

Narrow sector width and reduce depth to focus on area of interest.

Papillary level


Inspect for:

  • Papillary muscles (ant and post)
  • LV wall thickness
  • LV fx and RWMAs (see here for anatomy)
  • RV size and fx
  • Septal flattening

Measure:
LV area in diastole and systole (ignoring papillary muscles) to calculate fractional area change (a measure of systolic function).

Colour
Interventricular septum for VSD.

Apex
2D
LV function and RWMAs

MV level
2D
PSAX MV
Anterior and posterior leaflets visible. Note thickness, mobility and calcification.
Look for LV function, RWMAs and RV size.
Can measure MV orifice in systole with planimetry.
Colour
Over MV to look for precise position of regurgitant jets.
Over septum to look for VSD

Aortic level
2D
Inspect:

  • AV – should be tricuspid. Right, non and left coronary cusps as above (Royal National Lifeboat). Thickness, mobility and calcification.
  • TV
  • Inter-atrial septum (IAS)
  • Look for thrombus in RVOT and PA if PE suspected.

Measure:

  • Proximal RVOT diameter immediately above the AV (should have already measured this in PLAX).
  • PV annulus and main PA

Colour
Inter-atrial septum.
AV for regurg.
TV – inflow and regurg.
PV – stenosis and regurg.
Doppler
CW through TV and PV

  • Vmax of forward flow to measure peak gradient and calculate stenosis.
  • VTI (trace doppler forward flow) for mean gradient.
  • Vmax of any regurg (align with jet) – TR for PASP and PR for PA pressure – PR Vmax end diastole for end PADP and PR Vmax early diastole for mean PADP.

PW in TV and PV inflow – trace VTI which will measure mean gradient. 
Measuring the VTI just proximal to the PV will also allow stroke volume (SV) to be calculated provided the RVOT has been measured at the same point. 

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