Proximal isovelocity surface area
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Synonyms and related keywords: PISA
Overview
The proximal isovelocity surface area (PISA) technique can be used to estimate the flow across the regurgitant valve together with the Effective Regurgitant Orifice Area (EROA).
The technique is an application of the continuity principle with the underlying assumption being that the flow at the hemispheric first alias proximal surface is equal to the orificial flow at the same time in the cardiac cycle.
In order to measure these indices of regurgitation it is necessary to perform both continuous wave Doppler (CWD) and colour Doppler analyses of representative cardiac cycles.
Vmax (the peak velocity of the regurgitant flow signal) is measured with CWD.
Colour Doppler is then used to measure the radius (RA1) of the first aliased hemispheric shell at a Nyquist limit (Scale Value) typically in the range 30 - 40 cm/sec (VN). [1] [2]
Typical values of PISA radius (at VN of 38 cm/sec) for mitral regurgitation of differing severity are:
- Grade PISA Radius(mm)
- Mild: < 3.5
- Moderate: 3.5 - 7.5
- Moderately Severe: 7.5 - 14.5
- Severe: > 14.5
Typical values of PISA Flow for mitral regurgitation of differing severity are:
- Grade PISA Q
- Mild: < 30 ml/sec
- Moderate: 30 - 130 ml/sec
- Moderately Severe: 130 - 500 ml/sec
- Severe: > 500 ml/sec
Typical values of EROA for mitral regurgitation of differing severity are:
- Grade EROA(mm2)
- Mild: < 20
- Moderate: 20 - 29
- Moderately Severe: 30 - 39
- Severe: > 40
According to Kolev et al, the PISA technique may be particularly appropriate for the estimation of the severity of mitral regurgitation in the patient with an eccentric regurgitant jet.
How to Calculate PISA?
- Shift Aliasing velocity to 40 cm/sec
- Cine to mid systole
- Measure radius (cm)
- Calculate r2/ 2 to get ERO
- To Calculate Volume (cc) ERO x TVI of mitral valve
References
- ↑ Bargiggia GS, Tronconi L, Sahn DJ, Recusani F, Raisaro A, De Servi S, Valdes-Cruz LM, Montemartini C. A new method for quantitation of mitral regurgitation based on color flow Doppler imaging of flow convergence proximal to regurgitant orifice. Circulation. 1991 Oct;84(4):1481-9.
- ↑ Kolev N, Brase R, Wolner E, Zimpfer M. Quantification of mitral regurgitant flow using proximal isovelocity surface area method: a transesophageal echocardiography perioperative study. J Cardiothorac Vasc Anesth. 1998 Feb;12(1):22-6.