What Is Fractional Flow Reserve (FFR)?

A Fractional Flow Reserve Study (FFR) is where the effect of a coronary artery narrowing (stenosis) is assessed, by measuring the effect on the pressure in the artery before and after the narrowing.

The principle is that if the pressure is lower beyond the narrowing, then the flow must be reduced (such as when one stands on a garden hose).  If the pressure is the same beyond and before the narrowing, then there can be no significant restriction to the flow.

Other ways of assessing the nature and significance of a coronary artery stenosis is through Intravascular Ultrasound (IVUS) and Optical Coherence Tomography (OCT).