ECHONOMY Tools for Echocardiographic Calculations Muhamed Saric, MD, PhD
New York University
CFR stands for coronary flow
reserve and is a measure of total coronary resistance epicardial
Vmax distal to a coronary stenosis is measured by Doppler wire at rest
and after maximal hyperemia (e.g. after adenosine infusion at 140
Doppler wire uses a tip- or side-mounted crystal and pulsed wave (PW)
Doppler technique to measure Vmax.
Vmean is calculated as 1/2 * Vmax
Vmean is a measure of
total coronary resistance if one assumes that the cross-sectional area of
coronary vessels does not change from rest to maximal hyperemia.
Vmean at rest
Vmean at maximal hyperemia
The more severe the coronary stenosis, the lower the
increase in hyperemic Vmean.
Absolute for vessel
Relative to reference vessel (e.g. LAD vs. RCA)
V in the CFR formulat refers to Vmean.
Wilson RF, Laughlin DE, Ackell PH,
Chilian WM, Holida MD, Hartley CJ, Armstrong ML, Marcus ML, White CW.
Transluminal, subselective measurement of coronary artery blood flow
velocity and vasodilator reserve in man.
1985 Jul;72(1):82-92.[This article has a nice drawing of
an early Doppler wire with a side-mounted 20 MHz crystal.]
JW, Corl PD, Payne HM, Flynn AE, Goto M, Nassi M, Segal J. Validation of a
Doppler guide wire for intravascular measurement of coronary artery flow
Circulation. 1992 May;85(5):1899-911.
[This article has a nice drawing of
a modern Doppler wire with a tip-mounted 12 MHz crystal.]