IVC DiameterCollapse with SniffRA Pressure (mmHg)
≤21 mm>50 %Normal
3 (0-5)
IntermediateIntermediateIntermediate
8 (5-10)
>21 mm<50 %High
15 (10-20)

Secondary indices of elevated RA pressure include:

  1. Restrictive filling
  2. Tricuspid E/E' >6
  3. Diastolic flow predominance in hepatic vein (HV) i.e. HV systolic filling fraction Vs/(Vs+Vd) <55%

IVC = Inferior vena cava; RA = Right atrium; HV = Hepatic veins