fractional flow reserve

Fractional flow reserve answers a deceptively hard question: does a narrowing that the eye sees on an angiogram actually starve the muscle of blood? A narrowing may look impressive yet not limit flow, or look modest yet choke it. FFR settles the matter by measuring the pressure drop across the lesion — like checking the water pressure on both sides of a partly closed valve to learn whether it truly throttles the supply.

A very thin wire with a pressure sensor at its tip is passed across the narrowing during catheterization. The arteries are then maximally dilated, usually with adenosine, so that flow is pushed to its peak. FFR is the pressure measured beyond the narrowing divided by the pressure before it: a ratio of 1.0 means no meaningful obstruction, and lower values mean a bigger pressure loss. By convention, a value at or below about 0.80 marks a narrowing significant enough that opening it is likely to help, while higher values support leaving it alone and treating with medication.

Guiding stenting by FFR rather than by appearance alone improves outcomes and avoids stenting harmless narrowings, so it has become a standard tool for intermediate lesions. Pressure-derived indices that do not require a vasodilator drug now offer a similar judgment. The numbers must still be read with care for technical pitfalls and within the whole clinical picture, not in isolation.