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Page 12 of 15 Smer et al. Mini-invasive Surg 2020;4:52 I http://dx.doi.org/10.20517/2574-1225.2020.36

Figure 13. A simple example of the generation of flow accel eration can be shown by observing the draining of water from a household
bathtub. Flow acceleration or a localized area of high velocity develops as the large body of water moves toward the “hole” or opening in
the bottom of the tub, through which water flows into the drain. Adjacent to this “hole,” the area of flow accel eration becomes smaller
and tends to take the shape and size of the circular “hole” (vena contracta). Reproduced with permission from Kapur et al. [34]

Figure 14. Schematic depiction of the flow convergence or PISA method for quantitating valvular regurgitation. Va is the velocity at which
aliasing occurs in the flow convergence toward the regurgitant orifice. PISA: proximal isovelocity surface area; EROA: effective regurgitant
orifice area; PkV : peak velocity of the regurgitant jet determined by continuous wave Doppler; Reg flow: regurgitant flow; Reg jet:
Reg
regurgitation jet. Reproduced with permission from Manjunath et al. [4]

2
≥ 60 mL indicates severe MR [Table 2]. However, in secondary MR, EROA ≥ 0.2 cm and/or RVol ≥ 30 mL
[35]
is associated with worse outcomes .
Similar to VC measurement, the PISA method could be misleading if multiple jets or noncircular
regurgitant orifices present. It could be technically challenging to obtain accurate PISA measurements in
cases of eccentric jets. A major problem in quantifying MR severity by the PISA method is the assumption
that the flow convergence is hemispherical in shape, which is not the case in most patients with MR. Thus,
EROA by PISA equation is not recommended in the presence of MV devices including MitraClip, because