Cath Lab Digest

Many physicians are exploring device use in the lower extremities, while techniques for successful and appropriate stenting are also being intensely discussed. Where does cryoplasty fit into the current picture?
Peripheral vascular disease, in general, is a relentless and proliferative process. With cryoplasty, whether it be in the fem-pop segment or below the knee, we are trying to achieve both better acute outcomes and long-term outcomes. What we're trying to accomplish is a minimization of the need for stent implants in the legs because they have their own set of problems and simultaneously, we are trying to prolong the patency of these arteries to enhance the results of endovascular interventions.

There are whole host of potential applications for this therapy, and the ones easiest to point to are in areas of the lower extremities where a stent solution is not ideal, such as where there is flexion, at the knee or at the hip. These are arteries that we know have a very bad track record with stenting, especially below the knee. For patients like that, this really offers a breakthrough opportunity for treatment.

In the U.S. pivotal trial, we had lesions that ranged from very focal simple disease to those that were up to about 10 cm in length and included occlusive disease — so not just stenotic disease. With the below-the-knee work, we were dealing with patients who had critical limb ischemia. They had rest pain, ulcerations and early gangrenous changes, which means fairly extensive disease and obviously it’s a higher risk population of patients. Despite that, we were able to achieve about a 95% rate of limb salvage. In critical practice, physicians who have adopted the technology continue to apply it in a wide range of lesions: longer lengths and lesions that are more complex.

What can you tell us about the recently announced final data in the U.S. pivotal trial?
The U.S. pivotal trial was completed in December of 2002. We have previously reported the 9-month target lesion rate in these patients, which was ~17%. At VIVA, the final data were presented by the director of the ultrasound core lab, Dr. Michael Jaff. Dr. Jaff reported a primary patency rate of 76% with a primary assisted patency rate of 94% at the conclusion of the study. Primary patency included the hard endpoints of patients that required re-intervention, with those that were found to have restenosis by duplex ultrasound in the follow-up period. We continue to try to accumulate longer and longer-term data, and we continue to like what we see.

How far out is patency data?
Our first patients treated now are out about 30 months. In November 2004, in the Journal of Vascular Interventional Radiology,¹ we reported on the initial human experience, which had an 18-month angiographic follow-up (abstract below). In that group, the patency of those vessels by angiography at 18 months was 83.6%.

What do diabetic patient results look like?
Obviously, the diabetic is high on the list of concerns because they have a much higher risk of amputation. Interestingly, in the U.S. pivotal trial, when we broke down diabetic versus nondiabetic patients, they performed essentially the same. In contrast with other therapies that we’ve seen reported over the years, where diabetes always makes things behave worse, the early trend with cryoplasty is encouraging. Even though we are not dealing with thousands of patients in terms of the analysis, it does suggest that this therapy may show particular promise in the diabetic patient. Diabetics, in particular, have a much higher rate of stenosing or occluding stents — that small diabetic vessel just doesn’t do well with an implant because the foreign body response is so aggressive. Similarly, in the limb salvage abstract that we presented at TCT, 85% of those patients were diabetic.² The patient cohort was diabetic by a large majority and they ultimately did much better then they would have in the absence of treatment. As a result, we are definitely in favor of diabetics being steered towards this technology.

Are there patients where you would eventually want to do the same treatment again?
That’s a good point. It’s actually one of the nice side stories of this procedure. We are not muddying the waters by putting in a metallic implant, because we're trying to leave the artery in its native state. There’s no handcuffing of options should the disease recur, so there’s certainly no limitation to coming back if needed and performing a second, similar procedure. There would be no limitation to applying any of the other therapies that are available or, for that matter, to offering surgical intervention if it was thought necessary. Based on the trial data that we have to date, the good news is that the frequency of the need for repeat intervention seems to be less than plain old angioplasty or stenting.