Case Commentary: An Interview With Professor James C. Spratt, BSc, MB ChB, MD

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Read the case study from Dr. Kalaivani Mahadevan, MD.

Professor Spratt, can you share your main takeaway from Dr. Mahadevan’s case?

This was a high stress case that underlined a major advantage of intravascular lithotripsy (IVL), which is that it is very safe and easy therapy to use. The learning curve with IVL is not steep. You can use IVL in a in a high-risk environment without having to learn on the spot or worrying about getting everything perfect for a new technique that you have only just read about. After a case, we ask, have I treated this patient safely? Have I treated this patient adequately? Here, IVL was the right technology for the right patient. The key fundamentals were correctly assessed: imaging was done in a systematic fashion with the goals of the case in mind and wasn’t overcomplicated. From a patient perspective, if you were on that table, do you want somebody treating you with a technology that is difficult to use, and the physician might not get it right? Or do you want somebody to treat you with something that is easy to use, and they can’t get it wrong? When patients come into the cath lab very unwell, you don’t want to make things more complicated. You want to keep it as easy as possible.

You mentioned safety as one important aspect of IVL treatment. What are the other benefits you consider when using IVL to modify coronary calcium?

We use IVL to modify coronary calcium with the goal of changing vascular compliance. When the calcium reaches a certain volume, the confluence of the calcium is what makes it important for vascular compliance. It’s like a lake which freezes over in winter. At the start, when the lake is starting to freeze, there are bits of ice floating about in the lake. Each chunk of ice is still as stiff as the whole lake would be if it was frozen, but you don’t walk on it, because the total compliance of the lake is still very low because of the water. When calcium becomes confluent, it forms plates, just like the ice in a lake, and that is when it adversely affects vascular compliance. When IVL fractures the calcium into little pieces, it doesn’t change the compliance of each piece, but it does change the compliance of the artery.

We use IVL to fracture calcium, not only to improve vascular compliance, but also because the fractures lessen the volume of the calcium. The analogy is the jar full of stones. Is the jar full? It looks full, but you can add some pebbles and it fills up jar even more. Then you can add sand. So, if we fracture calcium from a single large piece into, say, 20 little pieces, then it will take up less volume. That is important because to be able to fully expand a stent, it requires reducing the volume of the plaque as well as improving vascular compliance.

Can you share some of your experience with the use of the C²⁺?

The C²⁺ offers 40 extra pulses, so 50% more energy, but otherwise it is the same as the original C² catheter. Previously, we tended to focus on a very tight lesion and use up all of our pulses there. We now know how important it is to treat the entire vessel where you plan to implant a stent. With the additional pulses of the C²⁺, we have been able to target noncritical calcium that would still affect stent expansion and therefore treat longer lesions.

What is your process when determining which modality is most appropriate for calcium modification?

We use intravascular imaging to characterize the morphology of the calcium and then we have an algorithm that helps us determine the treatment (Figure).

What do you recommend for an operator who may be considering the use of IVL for coronary calcium modification?

Learn the basics of plaque biology: why calcium matters and how you can treat it successfully with IVL. Understand the basics of acoustic therapy with IVL and how to optimize its efficacy. 

Read the case study from Dr. Kalaivani Mahadevan, MD.

Disclosure: Professor James Spratt reports he is a consultant for Shockwave Medical.

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