# Fractional Flow Reserve Calculator (FFR) Compute FFR = Pd / Pa (at maximal hyperemia). >0.80 non-ischemic; ≤0.80 PCI indicated. Derived from Pijls 1996, FAME, FAME 2, ESC/EACTS 2018, ACC/AHA 2021, StatPearls. Not medical advice. > Canonical page: https://elysiatools.com/en/tools/fractional-flow-reserve - **Category:** Health - **Keywords:** fractional flow reserve, ffr, coronary pressure, pd pa ratio, coronary stenosis, myocardial ischemia, pci, hyperemia, adenosine, ifr, interventional cardiology, cardiology ## Overview The Fractional Flow Reserve Calculator computes FFR from distal coronary pressure (Pd) and aortic pressure (Pa) measured at maximal hyperemia using FFR = Pd / Pa. Results include the pressure gradient, FFR value, percentage, and a non-ischemic or ischemic category. This tool is for reference only and is not medical advice. ## Inputs - **Distal Coronary Pressure Pd (mmHg)** (number): Distal coronary pressure (mmHg) measured with a pressure wire across the stenosis at maximal hyperemia. - **Aortic Pressure Pa (mmHg)** (number): Aortic pressure (mmHg) at the guiding catheter, same instant as Pd, at maximal hyperemia. - **Decimal Places** (number) ## When to use - Calculate FFR from paired Pd and Pa measurements recorded at maximal hyperemia. - Review the hemodynamic significance of a coronary stenosis using the 0.80 threshold. - Check the pressure gradient and rounded FFR result for clinical documentation or discussion. ## How it works - Enter distal coronary pressure Pd in mmHg from a pressure wire measurement. - Enter aortic pressure Pa in mmHg measured at the same time and during maximal hyperemia. - The calculator divides Pd by Pa and calculates the pressure gradient as Pa − Pd. - The result is labeled non-ischemic when FFR is above 0.80 or ischemic when FFR is 0.80 or lower, using the selected decimal places. ## Use cases - Interventional cardiology teams can verify FFR calculations from pressure-wire measurements. - Clinicians can review whether a measured FFR falls above or below the 0.80 reference threshold. - Medical educators and trainees can demonstrate how Pd and Pa produce an FFR value and pressure gradient. ## Frequently asked questions ### What is the FFR formula? FFR is calculated as Pd divided by Pa, where Pd is distal coronary pressure and Pa is aortic pressure. ### What inputs does the calculator require? It requires Pd and Pa values in mmHg measured at the same time during maximal hyperemia. ### How is the FFR result categorized? FFR above 0.80 is categorized as non-ischemic; FFR of 0.80 or lower is categorized as ischemic. ### Can I control the displayed precision? Yes. You can select the number of decimal places from 0 to 8; the default is 3. ### Is this calculator medical advice? No. It provides a mathematical FFR calculation and should not replace clinical assessment or professional medical judgment. ## Related tools - [Transfection Efficiency Calculator (GFP Positive Rate)](https://elysiatools.com/en/tools/transfection-efficiency): GFP reporter transfection scoring: efficiency = GFP+ / total × 100 with a Wilson 95% CI in single mode and per-replicate mean ± SD in replicate mode. 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