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BackTable / VI / Article
Using IVUS to Guide Treatment of Calcified Vessels with Intravascular Lithotripsy
Delaney Aguilar • Updated Jan 16, 2022 • 224 hits
Intravascular ultrasound (IVUS) is a minimally invasive imaging technology for evaluating vessel stenosis and calcification in real time. Other imaging modalities such as CTA and MRI fail to provide the real-time resolution of intravascular ultrasound, require the use of contrast or are susceptible to motion artifact, limiting their utility in select cases. Furthermore, the effects of intravascular can be seen on IVUS, making it an ideal imaging tool in the treatment of calcified vessels.
Dr. Bryan Fisher, a vascular surgeon in Nashville with extensive experience using IVUS and intravascular lithotripsy, shares his approach to imaging calcified vessels before and after treatment. This article features excerpts from the BackTable Podcast. We’ve provided the highlight reel in this article, and you can listen to the full podcast below.
The BackTable Brief
• Medial calcifications on intravascular ultrasound show a thin but bright medial stripe that forms an almost perfect ring. Intimal calcifications show greater echogenicity of the intima without loss of the medial stripe.
• .014 catheter systems and intravascular ultrasound devices provide higher quality resolution than .018 systems and are preferred by Dr. Brian Fisher due to their better visualization and pushability through highly stenotic lesions.
• Post-treatment images with intravascular ultrasound or optical coherence tomography (OCT) offer clear visualization of the cracks in the vessel calcifications created by intravascular lithotripsy, which allow for the remodeling of the vessel and make the vessel more amenable to angioplasty.
Image provided By Dr. Donald Garbett.
Table of Contents
(1) Deciphering Between Calcified Media or Intima on IVUS
(2) .014 vs .018 IVUS in Calcified Vessels
(3) Imaging Intravascular Lithotripsy Results with IVUS
Deciphering Between Calcified Media or Intima on IVUS
Intravascular ultrasound is currently the best tool for the evaluation of calcification within the vessel walls. To the beginner operator though, it can be difficult to assess whether the calcification that is seen is on the media or intima. Dr. Bryan Fisher describes that on intravascular ultrasound, you can distinguish the media with the medial stripe. When the media is calcified the stripe is thinner, more echogenic, and forms an almost ring-like appearance. Calcification of the intima, on the other hand, creates a whiter appearance to the intima itself with the media remaining as a dark stripe.
[Dr. Sabeen Dhand]:
I mean you brought up a good point though, as far as overestimating the calcium and I think people should be aware about that. And then the CT, even if you window it down like a radiologist, there's going to be these blooming artifacts. And so it's really hard to really know what you're seeing until once you put the balloon on and actually get into the vessel. Like put your patients on the fluoroscopy table and you mentioned intravascular ultrasound. Right? And it can really tell you between the two great intimal and medial calcifications.
How do you differentiate between the two on IVUS. Tell us what the difference is.
[Dr. Bryan Fisher]:
Yeah. So again, just being able to identify from an anatomical standpoint, what you typically will see the intima and then that medial stripe. It becomes pretty apparent when the medial stripe is calcified, it tends to have that white appearance. It tends to be a little thinner. And it appears diseased, but it's almost like a perfect ring around there. So in that area where the intima tends to be that whiter appearance, you get the darker media. When that media has that calcified portion, it typically stands out quite a bit.
[Dr. Sabeen Dhand]:
I see. And then does that change the way how you approach a lesion? We know that you are a big fan of intravascular ultrasound when you're doing these cases. So are you actually looking at the location of the calcium, and then treating based on that?
[Dr. Bryan Fisher]:
You have to in my opinion. When it comes to doing definitive treatment of these patients and what you see, it's important to understand what's there and what the pathology is that you're treating. And understanding that if you have medial calcium, the ability to one: deliver drug through into the media is going to be a little more difficult. It makes it more challenging. Atherectomy may or may not have the same effects because you're dealing with that deeper layer. And the truth is though there are some companies that tout some interesting things about being able to treat medial calcium. We know that based on post damaging, it's an extremely difficult area to treat. And so that's why some emerging technology has really been nice and being able to address this
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.014 vs .018 IVUS in Calcified Vessels
Catheter size, and therefore pushability, are important factors for the optimal visualization of vessel architecture via intravascular ultrasound. .014 systems seemed to be the most commonly used as they provide greater resolution. Dr. Bryan Fisher describes using an .014 system, which allows him to run the IVUS retrograde from the tibial arteries while running the therapeutic catheters anterograde in his so-called “Edward Technique.”
[Dr. Bryan Fisher]:
First of all, I'm very price conscious. So I have a dual practice, both being in the hospital and the OBL setting. And I try to be conscious in both settings on what I'm spending and what can I do from the most cost-efficient standpoint while still being able to achieve success. That triaxial system can be really important. However, I'll often just switch, I'll go either .014 workhorse or .018 workhorse wire. And most of the time I'm able to get through those lesions without too much difficulty. If I run into problems, then I typically will go to a more weighted wire with a heavy gram tip and try and work my way through in that manner with the idea that for the most part I want to try and stay true lumen during my course.
There's some other things you can do. I think that the advanced operators can describe when you start turning wires backwards and doing those kinds of things, which again, I would not recommend for the novice interventionalist. However, for those that are experts that I've had the privilege of working with and observing, those are real options and being able to get through these types of lesions. So then in progressing along once I've done my wire escalation strategy, and once I'm able to get through the lesion, which, by the time you add retrograde access, I can get through about 95% of those lesions. Then it's time to switch to an 014 or 018 system, and really start to understand what's going on with that vessel architecture with intravascular ultrasound.
[Dr. Sabeen Dhand]:
Are you normally using an .014 IVUS? Or are you using .018 or it just depends on what your wire is? I've heard different things about what's better and not. We personally use .014 IVUS in our practice.
[Dr. Bryan Fisher]:
Yeah. No, that's a great point. The .014 imaging is much better than the .018 system. Now I understand that there is an .018 system that's come out that's since been introduced to the market that offers some better resolution. I tend to lean towards the .014 system especially in the case where I've gone retrograde from the tibials, I can have a 4-French sheath. Then if I've got single wire control, I can do what I like to refer as the Edward technique, where I have an IVUS catheter coming from below, and I can do my definitive treatment and do diagnostic work from above. Therefore I'm saving a little bit of time in doing the case.
Imaging Intravascular Lithotripsy Results with IVUS
Intravascular lithotripsy is a new and innovative technology which allows for very focal and intermittent pulses of energy to breakdown vessel calcifications. This is a much safer option than the traditional approach of ballooning up to 50 atmospheres, which poses the risk of rupturing the vessel. Another advantage of intravascular lithotripsy is that it is very easy to see cracks within the calcium on IVUS and OCT following treatment.
[Dr. Bryan Fisher]:
It's a really exciting technology that has been modified from what's been done in the urologic world. The ability to use pulses of energy and almost like a shock wave, if you will, to modify those calcified areas. With intravascular lithotripsy, you're delivering these very focal areas of energy that are all the way up to 50 atmospheres, which is an interesting concept. And you thought about trying to take a balloon up to that point, we'd ruptured those vessels all day. That would be probably a bad plan. But this newer technology allows the delivery of energy in an intermittent fashion, but very focal and allows you to modify those areas. And that's been a really exciting newer frontier when it comes to treatment of calcium because we really haven't had anything like it so far in the treatment of lower extremity disease. I've been interested in vascular surgery now for 15 years. And so this is one of the first technologies to really truly come out and address this in a systematic fashion, but then you've kind of got the proof and the imaging afterwards.
[Dr. Sabeen Dhand]:
Yeah. Talk like that's what I wanted to ask you. So what have you seen on IVUS post-shockwave? Do you see any differences? I mean, I know it's a low resolution of the media. When I see a cartoon drawing, I see a bunch of cracks in the media after a shockwave. Do you see anything equivalent to that?
[Dr. Bryan Fisher]:
You do see something in it and it can be quite subtle. But if you can think of a Cheerio where you crack it in a couple of different areas. If you really go through those IVUS images slowly, you can clearly see that there's evidence of true cracks in the calcium. And again, there are lots of claims everyone's made about calcium. And this is really the first company that I've seen that can show the proof and even better. I don't use this technology yet, and I'm looking and trying to incorporate into my practice because of the imaging that you get. But OCT shows those cracks in the calcium brilliantly. And that's been really one of the more exciting aspects of kind of that advanced imaging is seeing the proof in the pudding.
Podcast Contributors
Dr. Bryan Fisher
Doctor Bryan T. Fisher Sr. is a practicing Vascular Surgeon and the Chief of Vascular Surgery at Tristar Centennial Medical Center in Nashville, TN.
Dr. Sabeen Dhand
Dr. Sabeen Dhand is a practicing interventional radiologist with PIH Health in Los Angeles.
Cite This Podcast
BackTable, LLC (Producer). (2021, December 13). Ep. 172 – Treating Above the Knee Calcium [Audio podcast]. Retrieved from https://www.backtable.com
Disclaimer: The Materials available on BackTable.com are for informational and educational purposes only and are not a substitute for the professional judgment of a healthcare professional in diagnosing and treating patients. The opinions expressed by participants of the BackTable Podcast belong solely to the participants, and do not necessarily reflect the views of BackTable.
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