Qp/Qs (RVOT vs LVOT)

Qp ≈ RVOT area × RVOT VTI. Qs ≈ LVOT area × LVOT VTI. Qp/Qs = Qp / Qs.

Inputs

LVOT diameter

LVOT VTI

RVOT diameter

RVOT VTI

Tip: Make sure LVOT and RVOT sampling are consistent (location, angle/alignment, beat averaging in AF).

LVOT area

π × (d/2)²

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Qs (systemic SV)

LVOT area × LVOT VTI

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RVOT area

π × (d/2)²

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Qp (pulmonary SV)

RVOT area × RVOT VTI

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Qp/Qs

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Rule-of-thumb cutoffs vary by context. Many labs treat Qp/Qs ≥ 1.5 as a meaningful L→R shunt, but always interpret with the full echo picture.