How do FFR and iFR differ in assessing coronary stenosis?

How do FFR and iFR differ in assessing coronary stenosis?

• A. FFR requires hyperemia-induced pressure measurements; iFR uses resting measurements avoiding vasodilators.
• B. FFR uses resting measurements; iFR requires hyperemia.
• C. Both measure clot burden.
• D. FFR is only imaging; iFR is only angiography.

Answer: (B)

Both FFR and iFR are invasive tests that use pressure measurements to judge whether a coronary narrowing is causing a meaningful drop in blood flow. The key difference is how they achieve a consistent state to reveal that drop. FFR uses pharmacologic hyperemia to maximize blood flow through the coronary bed; during this maximal vasodilation, the pressure drop across the lesion reflects its true impact on flow when demand is high. The value is the distal pressure divided by the aortic pressure during hyperemia. iFR, on the other hand, relies on resting conditions and a specific wave-free period in diastole when microvascular resistance is naturally low and stable, so no vasodilator is given; the ratio is calculated from resting distal to aortic pressures at that moment. Therefore, the idea that the test with hyperemia is iFR and the resting test is FFR is not correct. The other statements are not accurate because these tests do not measure clot burden, and they are not purely imaging or angiography; they are pressure-based physiological measurements.

Both FFR and iFR are invasive tests that use pressure measurements to judge whether a coronary narrowing is causing a meaningful drop in blood flow. The key difference is how they achieve a consistent state to reveal that drop. FFR uses pharmacologic hyperemia to maximize blood flow through the coronary bed; during this maximal vasodilation, the pressure drop across the lesion reflects its true impact on flow when demand is high. The value is the distal pressure divided by the aortic pressure during hyperemia. iFR, on the other hand, relies on resting conditions and a specific wave-free period in diastole when microvascular resistance is naturally low and stable, so no vasodilator is given; the ratio is calculated from resting distal to aortic pressures at that moment.

Therefore, the idea that the test with hyperemia is iFR and the resting test is FFR is not correct. The other statements are not accurate because these tests do not measure clot burden, and they are not purely imaging or angiography; they are pressure-based physiological measurements.