Prof Morton Kern (VA Long Beach Health Care System, Long Beach, CA, US) discusses whether Quantitative flow ratio (QFR) will ever replace fractional-flow reserve (FFR).

Questions:

1. What is QFR and why is it needed?
2. Where is QFR being used and what data supports it?
3. Will QFR replace FFR?
4. How does it compare to resting indices like iFR?
5. What is needed to validate QFR as a serious option?

Filmed on location at CRT 2020.

Interviewer: Rebekah Meola
Videographer: Charlie McClanahan

Transcript Below :

Question 1 : What is QFR and why is it needed?

[Kern]  So QFR is an angiographic method to derive physiology and to compute a fractional flow reserve, which is a measure we do now with invasive pressure wire. And the QFR will tell us what the significance of certain angiographic legions is. And whether they're limiting flow or not. 

Question 2 : Where is QFR being used and what data supports it?

[Kern] Well, QFR right now is on limited release. It's in it's initial phases to come to the United States. Several centres around the country are using it. This angiographic method, I'll just briefly review it for you. It's a quick method to get QFR, to get FFR by two orthogonal angiograms and applying computational fluid dynamics. So this method is used in various centers at the moment for undergoing research and testing. The data shows a fairly good correlation with measured invasive fractional flow reserve. Above 80%, closer to 90, and has the potential to replace some of our invasive FFR measurements. 

Question 3 : Will QFR replace FFR?

[Kern] So, will QFR replace FFR? I think, eventually, yes. And there will be cases in which we learn that it cannot be absolutely accurate and in those cases we'll still be doing some invasive FFR. But this is not going to come in the short term. I think it's got a five year entry window, and maybe not standard of care for a little longer than that. 

Question 4 : How does it compare to resting indices like iFR?

[Kern] So, how does QFR compare to resting indices such as IFR or other non-hyperemic pressure indices? I think the data still is out on that one. I don't recall seeing specific studies in which the calculations have been recalibrated toward resting data. It's all now employing hyperemic measurements. I think future studies will likely show that it's at least similar, perhaps not inferior. I doubt it would be superior, but that data is yet to be generated. 

Question 5 : What is needed to validate QFR as a serious option?

[Kern] So, like every other pressure indices that we've employed, we needed outcome data. And so, not only is equality of the index with our current invasive measurements required, and that's what testing is going on now, but the outcomes employing this in practise, compared to the other alternatives of invasive measurements both during hyperemia and at rest. And if QFR shows equal outcomes, then I think that will certainly go a long way to replace our current methodology.