Fractional flow reserve (FFR: ratio of pressures distal and proximal to a stenosis), the commonly used diagnostic parameter for functional assessment of coronary stenosis, has a threshold range of 0.75–0.80 below which clinical intervention is recommended. This range is known as a “gray” zone resulting in uncertainty of diagnosis. An alternate diagnostic parameter, pressure drop coefficient (CDP: ratio of trans-stenotic pressure drop to the proximal dynamic pressure), developed based on fundamental fluid dynamics principles, has been suggested by our group. Pressure drop coefficient has a wide range of 0 ∼ 1000.
In the presence of an additional downstream stenosis, FFR values of an upstream intermediate stenosis (80% area stenosis (AS)) may vary near the “gray” zone due to the reduction in hyperemic flow (flow at maximum arterial vasodilation), , and pressure drop, , leading to the possible misinterpretation of stenosis severity. Hence,...
