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February 11, 2010 -- 8:00pm EST

IVUS vs. FFR -- Boston Style
Earlier today I was doing research for an article about stents for our site, Angioplasty.Org. I Googled "Fractional Flow Reserve FFR" and the sponsored link at the top of the page, titled "IVUS vs. FFR", caught my eye -- mainly because IVUS and FFR are two completely different modalities and doing a "versus" with them is oh so apples and oranges. Anyway, I was curious and clicked through to advertiser Boston Scientific's web page about how IVUS is so much better (10 times better even) than FFR.

So what's wrong with this picture?

Well...FFR measures intracoronary blood pressure across a blockage. A blockage may look significant on an angiogram, but 1/3 of the time (according to the FAME study) it isn't "flow-limiting"-- and probably doesn't need to be opened up and stented. Working this way is called FFR-guided PCI (i.e. angioplasty and stenting). It improves outcomes and saves money. In fact the recently issued AHA/ACC/SCAI Guidelines Update just raised the level of evidence for use of FFR to "A", stating that FFR "can be useful to determine whether PCI of a specific coronary lesion is warranted."

IVUS (IntraVascular UltraSound) is an imaging modality and it doesn't measure blood pressures. It allows the cardiologist to see (and measure quite accurately) the diameter of the artery, the size of the blockage, the length of the diseased portion. In newer sophisticated systems, something called Virtual Histology™ can even differentiate the type of plaque, including so-called "vulnerable plaque" that may be more prone to causing a heart attack. IVUS is a great tool, kind of like having a ruler inside the artery, but the revelations of the FAME study could not have been made using IVUS.

In fact the two tools can work very well together: FFR-guided PCI refines the decision-making process of whether or not to stent; IVUS refines the mechanical stenting process of placing and inflating the device optimally. Ideally, both can be used to improve the outcomes of PCI procedures. It's not either/or: IVUS helps you do a better job when you stent people; FFR helps you avoid stenting people unnecessarily.

So why is Boston Scientific demeaning the value of Fractional Flow Reserve? Possibly because there are only two manufacturers of this technology, and they're not one of them. St. Jude is one, as a result of their acquisition of Swedish firm Radi; Volcano is the other. Volcano is also Boston Scientific's only competitor in the IVUS field -- and they offer a system that integrates both FFR and IVUS.

The ad suddenly made sense.

As for my search for information on FFR, I ran into a familiar situation. The first two hits were articles I had already written on the subject!

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