NON-INVASIVE FFR USING CCTA

For many years, I have been criticising the extensive use of CCTA, in the screening for healthy males, for CAD. With the 16 slice MSCT and the 64 Slice MSCT, I felt that the diagnostic accuracy was not quite good enough, except to exclude CAD ( which is what I use it for ), couple with the obvious hazard of extensive radiation ( A CCTA of the coronary system gives the equivalent of 500 CXR radiation ), with the old 64 slice MSCT.
On Tuesday, I had a visit from the boss of a CCTA machine maker who shared with me that nowadays, they have 640 slice MSCT ( available in Malaysia ) where you can scan the whole coronary tree in one heart beat, thereby drastically reducing radiation to the patient. The diagnostic accuracy, he claims, has also increase. Well, the first part ( less radiation with the 640 machine), I believe but the second part, I took it with a pinch of salt, because, I reason that with computer physical reconstruction, you can never accurately enough make a 2D coronary circulation into a 3D image coronary circulation image. There must be some tradeoff, and loss of data, with some computer assumptions.
Well, in a way, I am right, but in a way, I stand to be corrected. As I was researching and reading into this issue of diagnostic accuracy of even invasive coronary angiograms, I came across the extensive work of the Americans and also the Koreans, who were working very hard to define " a significant stenosis". Not all stenosis that you see on the invasive angiogram is significant. Some stenosis, which appears terrible, when evaluated functionally, is actually insignificant. When I was in Beijing, Dr SJ Park ( my vintage, whom I have known for along time ), showed his experience in using FFR to discriminate between lesions requiring PCI and lesion which did not require PCI. He showed invasive angiogram pictures of 70-80% stenosis, which I would have thought were obviously significant, turned out to be insignificant on FFR, and when left alone, after follow-up, the patient became well, with no clinical events.
The point is that we may have to physiologically evaluate coronary stenosis, in order to know which is causing problems, and event relevant and which is not.
Well, the Koreans have gone even better. In March, at the ACC, I saw a paper presented by the Koreans, which studied the non-invasive measurement of FFR on CCTA. When I had lunch with the CCTA machine boss, I brought up the subject, that this will surely increase the accuracy of CCTA in the non-invasive evaluation of a subject for CAD. At that time, our discussion was centered on getting more evidence, to see if the initial Korean experience is true, and to see if others across the world will have a similar experience.
Well, it is, looks like.
I have just found a paper presented at the May meeting of EuroPCR, by the Latvians. They studied 20 healthy subjects who were underwent CCTA non-invasive FFR evaluation and also invasive angiogram and FFR evaluation. The correlation is very good.





The Koreans have also got almost similar numbers. It looks like, soon with the 640 slice MSCT and non-invasive FFR on CCTA, we will have a modality to screen normal healthy subjects, with little radiation, and also adequate accuracy. That should see much less invasive angiograms, and also much less PCIs and stents. This is also the present Korean experience. With the greater use of FFR in the angiographic suite, they have seen much less PCIs and stents.
The saying amongst us if that, if you see a lesion on the invasive angiogram, and you wish to stent ( like all good US interventionist ) use the intravascular ultrasound. If you do not wish to stent ( like the present Korean interventionist ) use FFR.
Between the two, I am sure there is a lesson for us. I seriously hope that the local boys will work with the non-invasive FFR physiology and bring this useful modality to Malaysia for our patients.
I shall post later, on the physiology of non-invasive FFR. Quite a good piece of work.