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Current Postings on This Page (2):
To Nursing Student in Pennsylvania -- The two values are related but not convertible per se. Here's why. The "per cent stenosis" is a visual measure, taken from an angiogram, or possibly from an intravascular ultrasound (IVUS) or optical coherence tomography (OCT) image. (The IVUS image is probably the most accurate of these, because it allows you to see underneath any plaque so you can determine the actual border of the native artery. This border is not visible on an angiogram). However, this is still only a visual assessment: it allows you to state, "there's a 50% stenosis" which means 50% of the arterial diameter at the place where you measured is blocked by plaque.
Fractional flow reserve (FFR) actually measures the physiologic functional flow of the arterial blood pressure, i.e. what percentage of blood flow is actually being allowed through the artery to the heart muscle -- and that's not the same as per cent stenosis because of flow dynamics within the circulation. For example, an angiogram may show a 50% stenosis, but the FFR may be .84, meaning that 84% of the blood flow is going through this narrowing. This was the finding of the FAME trial: a third of the time what was judged a significant stenosis by angiography was actually not significant when judged by FFR. In your example, 68% of the blood flow is getting through -- a significant narrowing that would indicate revascularization would be beneficial. For more detail on these issues, read our 2010 article on an analysis of the FAME data, "To Stent or Not To Stent: Fractional Flow Reserve (FFR) Trumps Angiography in Diagnosing Blockages up to 90%." Angioplasty.Org Staff, Angioplasty.Org, May 4, 2013
Is there a formula that converts FFR to lesion stenosis? If an FFR was done in a cath lab and the FFR was 0.68 what is the % stenosis? Nursing Student, Grantham, Pennsylvania, USA, May 1, 2013