Mixed news for plaque excision device at VIVA

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Given the recent controversy surrounding Foxhollow’s TALON registry and the alleged links the company had to several of the clinicians, industry analysts, JP Morgan, has reported there was mixed news for the company at the recent VIVA (Vascular Interventional Advances) conference, in Las Vegas, NV.

At the VIVA conference in Las Vegas, Dr Krishna Singh and team from Springfield, IL, treated an occlusion above the knee (in the SFA) in a 57-year old diabetic patient with hyperdislipidemia and a history of chronic smoking. Singh treated this patient with FoxHollow’s SilverHawk plaque excision device and using Guidant’s Accunet 2 embolic protection system during the procedure. While FoxHollow does not indicate that embolic protection is required with the SilverHawk, Singh noted significant concern over distal embolization in this procedure and opted to take a conservative approach in this case.

During the case, Singh noted four limitations with the application of the device. The first was the ability to control the torque of the catheter is limited and thus the device is hard to steer through the vasculature. Secondly, there was notable resistance to moving the device forward, as Singh struggled to navigate the device and cited “push-back” while in the artery. Thirdly, the device needed to be pulled out of the body several times to empty the nose cone before the procedure was completed, and finally he noted that the extreme care was required when pulling the device out of the body, as clinicians feared the device damaging the vessel (Singh equated this to “shaving against the grain” and the increased skin sensitivity).

Singh removed a significant amount of plaque from the vessel and was able to clear the occlusion. However, the procedure required the doctor to re-enter the vessel three times before obtaining a clean angiogram, underscoring the length of procedure time, a common concern of physicians at VIVA. Later in the afternoon, results from the IVUS follow-up furthered the efficacy debate.

This follow-up revealed damage to the vessel wall at the bifurcation of the lesion, which Singh described as a “divot in the vessel wall” or what looked to be excision below the atherosclerosis and into the vessel bed and incomplete excision of plaque which left a piece of tissue “hanging” behind in the vessel.

The latter raised particular concern over the potential for distal embolization. In addition to substantial procedure time, Singh also collected a significant amount of debris from the embolic protection device, which sparked debate among both the panelists and physician audience. The conclusion was that an alternative procedure such as a stent would have been more appropriate for this procedure. Atherosclerosis in the SFA is a common cause of PAD, and may imply using the SilverHawk device in the vessel could be limited over the long term.

On a more positive note for SilverHawk, there was a second live case involving a patient with similar baseline characteristics as the previous case with an occlusion in the popliteal artery. The team from Dallas, TX, approached this case with a stent instead of SilverHawk. After placing the stent in the artery, there was little improvement in blood flow given the location of the vessel. In addition, there was almost immediate in-stent restenosis, which the surgeon had noted difficulty bringing under control. As such, the team elected to switch over to a SilverHawk to remove the plaque.

Given the location of the occlusion, this was a more appropriate situation for SilverHawk as confirmed by the panelists moderating the live case. For reference, this panel involved the same group of doctors who moderated the morning SilverHawk case.

The indications of these results suggest that the SilverHawk devicew will ultimately be used in vessels where stents are highly ineffective such as those behind the knee, but more common areas of PAD will still be treated with stents and balloons. It is believed that the device will have a niche within the PAD market but given observed complications during the live case presentation such as length of procedure time and data limitations from the TALON registry, the product will probably be relegated to vessels where stents are highly ineffective (eg, behind the knee) and some diffuse, non-calcified vessels.

Given the live case demonstration and the discussion that followed, it does not appear that SilverHawk will be the standard of care in treating the superficial femoral artery (SFA), but it could be used in some blockages below the knee, an area where Spectranetics has also focused some of its efforts. Industry analysts, JP Morgan said that physicians are initially willing to try SilverHawk given the favorable economics; however, over an extended period of time (3-6 months), these same physicians are gradually reverting back to original treatment options such as stents and balloons and limit SilverHawk to the vessels mentioned previously.

The two most significant physician concerns that emerged from the VIVA confefrence were: (1) the length of time a SilverHawk procedure is significant and (2) the fear of distal embolization. Physicians noted that the time to administer a SilverHawk procedure is at minimum 30 minutes and can take up to two hours. Most physicians cited an average procedure time of about 75-90 minutes. This included physicians who have had a reasonable amount experience with the device (i.e., having used the device at least 3-5 times a month for greater than 6 months). The second issue is perhaps more concerning given that SilverHawk labeling does not require the use of an embolic protection device, but a large number of physicians have observed distal embolization in SilverHawk cases. The key question that then needs to be asked is how clinically relevant is the debris that is being generated by SilverHawk.

While the meeting highlighted several of the challenges with current technology to treat PAD (particularly atherectomy), physicians did seem intrigued about the prospects for cryoplasty. For background, cryoplasty involves the use of nitrous oxide, rather than saline, to inflate balloons and cool it to -10 degrees. This in turn prompts several physical responses that open the artery, potentially causing less scarring than traditional angioplasty. However, at this point, the therapy is largely unproven and is likely too early for prime time. Nevertheless, this group found the longer-term prospects for cryoplasty promising, given the minimally invasive nature of the procedure, reduced time to procedure and positive clinical experiences thus far. At the same time, physicians seemed to be losing interest in the potential for laser technology. This was largely driven by data from the PELA trial (Peripheral Excimer Laser Angioplasty), which demonstrated no difference in reinterventions at one-year when compared to balloon angioplasty at 360 days.

The enthusiasm for cryoplasty was also driven by strong clinical data from the 9-month PVD Big Chill IDE study. This study compared cryoplasty to PTA, which indicated that flow limiting dissections occurred in 7% of the patients in the cryoplasty arm compared to 43% in the PTA arm. In addition, cryoplasty demonstrated 94% procedural success as well as no device-related adverse events. The clinical results were also robust, demonstrating 82.2% primary clinical patency; 17.8% target lesion revascularization (TLR), and ABI improvement from baseline of 80%, and claudification improvement from baseline of 89%. However, despite these positive results the device remains ‘untested’.

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