FFR

ECHONOMY
Tools for Echocardiographic Calculations
Muhamed Saric, MD, PhD
New York University

FFR

Definition

FFR stands for fractional flow reserve and is a measure of resistance in the epicardial (conductance) coronary arteries.

Technical Hints

	Pressure wire is advanced into a coronary artery past the stenosis and MPP is measured.
	Pressure wire is then pulled back and MAP measured.
	Pressure measured after induction of maximal hyperemia (with e.g. adenosine, 140 µg/kg/min)
	Pressure gauge is located 3 cm proximal from wire tip.
	Pressure wire is a fiberoptic device that emits light from a control unit and transmits it through along the fiber to the sensor. Pressure-induced elastic movement of the sensor modulates the intensity of reflection. The light signal is then transmitted back through the same optic fiber and detected by a photo diode in the control unit.

Calculator

Mean arterial pressure (MAP)

mm Hg

Mean post-stenosis pressure (MPP)

mm Hg

Answer

FFR

Interpretation

The more severe the coronary stenosis, the larger the pressure drop between MAP and MPP. In severe stenosis, MAP : MAP > 5 : 1. Percutaneous coronary intervention is performed if FFR < 0.75.

	FFR
Normal	> .75
Inducible ischemia	.20 - .75
Resting ischemia	< .20

Formula

Reference

Emanuelsson H, Dohnal M, Lamm C, Tenerz L. Initial experiences with a miniaturized pressure transducer during coronary angioplasty. Cathet Cardiovasc Diagn. 1991 Oct;24(2):137-43.

Lamm C, Dohnal M, Serruys PW, Emanuelsson H. High fidelity translesional pressure gradients during percutaneous transluminal coronary angioplasty: correlation with quantitative coronary angiography. Am Heart J. 1993;126:66-75. [This article has a nice drawing of the pressure wire.]

Pijls NH, De Bruyne B, Peels K, Van Der Voort PH, Bonnier HJ, Bartunek J Koolen JJ, Koolen JJ. Measurement of fractional flow reserve to assess the functional severity of coronary-artery stenoses. N. Engl. J. Med. 1996;334(26):1703–8.