Define fractional flow reserve (FFR) and its standard threshold for ischemia.

Define fractional flow reserve (FFR) and its standard threshold for ischemia.

• A. FFR is the ratio of distal coronary pressure to aortic pressure during maximal hyperemia; ischemia is suggested when FFR ≤ 0.80.
• B. Ischemia is suggested when FFR ≤ 0.80.
• C. FFR is the ratio of heart rate to blood pressure during rest.
• D. FFR is the arterial oxygen content divided by venous oxygen content.

Answer: (A)

FFR is the physiologic index of how much a coronary stenosis limits blood flow. It is the ratio of distal coronary pressure to aortic pressure measured during maximal hyperemia, when the small vessels are dilated to their maximum and resistance is minimized. This setup ensures that the pressure drop across the lesion reflects its impact on flow rather than upstream resistance. A value of 0.80 or less is the standard threshold indicating ischemia and suggesting the lesion may benefit from revascularization; values above 0.80 usually indicate non-ischemic physiology. The other options describe unrelated measurements—for example, a ratio of heart rate to blood pressure or arterial to venous oxygen content—so they do not define FFR.

FFR is the physiologic index of how much a coronary stenosis limits blood flow. It is the ratio of distal coronary pressure to aortic pressure measured during maximal hyperemia, when the small vessels are dilated to their maximum and resistance is minimized. This setup ensures that the pressure drop across the lesion reflects its impact on flow rather than upstream resistance. A value of 0.80 or less is the standard threshold indicating ischemia and suggesting the lesion may benefit from revascularization; values above 0.80 usually indicate non-ischemic physiology. The other options describe unrelated measurements—for example, a ratio of heart rate to blood pressure or arterial to venous oxygen content—so they do not define FFR.