Qp/Qs – Pulmonary-Systemic Flow Ratio

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Data Acquisition

Qs Systemic flow

Qp Systemic flow

Reference Values

Normal 1:1
Left to right shunts >1.0
Right to left shunts <1.0


\[Qp = RVOT \hspace{0.2cm} VTI \times \pi \times (\frac{RVOT}{2})^2\]
\[Qs = LVOT \hspace{0.2cm} VTI \times \pi \times (\frac{LVOT}{2})^2\]
\[Qp/Qs \hspace{0.2cm}Ratio = \frac{Qp}{Qs}\]


Qp Pulmonary flow
Qs Systemic flow
LVOT Left ventricular outflow tract
LVOT VTI Left ventricular outflow tract velocity-time integreal
RVOT Right ventricular outflow tract
RVOT VTI Right ventricular outflow tract velocity-time integreal
Qp/Qs Pulmonary-systemic shunt ratio


1. Sanders SP, et al. Measurement of systemic and pulmonary blood flow and Qp/Qs ratio using Doppler and two-dimensional echocardiography. Am J. Cardiol, 51:952, 1983. Abstract


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Developer & Illustrator: Sirikarn Napan, MD, FACC