CIT international vision | How can intracavitary imaging promote the more accurate & efficient development of coronary intervention?

Editor's note: Recently, the 19th China Interventional Cardiology Conference (CIT 2021 Online) was successfully held online. As an indispensable part of interventional therapy, intracoronary imaging and physiology technology was also one of the key topics discussed at the conference. On this occasion, our magazine invited Prof.Gary S. Mintz, an internationally renowned imaging and interventional expert and chief medical officer of American Cardiology Research Foundation, to make an exclusive interview on related issues such as "the latest research progress of intracavitary imaging and physiology".

《International Circulation》: Precise coronary interventional therapy under the guidance of intracavitary imaging and physiology is a hot topic in the world. Would you please share us about the latest evidence-based medicine developments?

Professor Gary S. Mintz: There's just a lot of accumulating data, and that data is very consistent. When treating a non-left main lesion you should use physiology to decide whether or not the lesion is severe enough to treat. And you should optimize the result with intravascular imaging—either IVUS or OCT. when treating left main lesions, you can use imaging or physiology to decide whether or not to treat. But again, you should optimize the result with either IVUS or OCT.

I will share with you maybe just a couple of data points. The two largest IVUS studies— randomized studies—were IVUS-XPL, in Korea, and ULTIMATE, in China. I worked with both investigators to merge the patient level data. And with IVUS guidance, mortality was reduced by 50 percent consistently over time, which simply means that your patients will live longer if you do IVUS guidance when stenting lesions that are at least 1/8 mm or longer.

In terms of left main intervention, there was a report from the UK. This is a National Society registry showing that IVUS guidance left main intervention reduces mortality by 34 percent, and especially in the hands of interventionalists—who do the most left main PCI procedures—because they know how to use the data. So, we have randomized trials, meta-analyses, registries.

《International Circulation》: Coronary artery calcification is common in patients with coronary heart disease and is related to cardiovascular events and mortality. What is your opinion about the appropriate imaging tools should be selected to optimize the treatment of calcified lesions?

Professor Gary S. Mintz: coronary calcification is probably microscopically present in every body. That reaches the threshold when it impacts on PCI procedures. And we've known that for years. What we haven't done is developed algorithms or scoring systems to say when you must use some kind of plaque modification devices. And I won't get into which plaque modification device, but we published the first scoring system, which is an OCT scoring system showing what we call the Rule of 5 or 50 percent: more than half the circumference, more than 5 mm in length, and more than a half a mm thick will predictably limit stent expansion.

And so we now have an equivalent IVUS scoring system that includes circumferential calcium, more than 5 mm of calcium that's at least 270 degrees (or 3 quadrants), the presence of a calcified nodule, and vessel size. And when you have that combination, again—any two of those—predictably, you get stent under expansion. This issue of calcified nodules is becoming increasingly important and, perhaps, increasingly prevalent as our patients get older. Patients who have lesions—whether they are stable or unstable lesions—with calcified nodules do not do well after PCI, and we don't have a great strategy.

《International Circulation》: Coronary chronic total occlusion（CTO）has always been a difficult question in interventional therapy. How do you think that intravascular ultrasound (IVUS) should be used to improve the success rate of complex CTO interventional procedures?

Professor Gary S. Mintz: Well, there are many ways that you can use IVUS. As typical of most procedures, IVUS can help throughout the procedure. So, in terms of CTO, specifically, it can help you to identify the proximal fibrous cap, which is often ambiguous, both in terms of its axial location as well as circumferential location. It can tell you whether or not you have crossed the CTO—particularly, antegrade—and has stayed in the true lumen distally. Because if you stent into a false lumen, you don't get myocardial perfusion and the patients don't do well. It can assess the complications, perforation, dissections, intra- and extra-mural hematomas, and it can tell you whether you have properly implanted and sized and expanded the stent and got a good result from the stent part (which is, obviously, the end of the procedure). So, it can help throughout the procedure.

And we have data. We have randomized trial data that IVUS guidance reduces events at 1 year of follow up by 75-80 percent. So, it can help at many, many, many steps of the procedure. And it depends a little bit on what your procedure is. For example, if you decide to do a retrograde procedure—as opposed to an antegrade procedure— it can help to identify the retrograde wire in the false lumen and where you should connect the two by aggressive dilation. And then you can prove that you have entered the true lumen after aggressive dilation.