Five Questions With John B. Simpson, MD
Dr. Simpson sheds light on some of the benefits of plaque excision, an innovative alternative to PTA and stenting.
The FoxHollow SilverHawk System you helped develop was recently cleared by the FDA. How does it work? The platform excises large volumes of plaque in femoral-popliteal and tibial-peroneal vessels ranging from 2 mm to 6 mm in diameter. The procedure itself is pretty straightforward. The operator positions the catheter at the desired treatment area, activates the cutter, and advances it through the length of the lesion. As plaque is removed from the lumen, it is captured in the catheter’s distal nose cone. Because the cutter is apposed to the vessel wall mechanically, it achieves significant luminal gain without creating the barotrauma associated with stenting and PTA.
How will plaque excision change the way lower-extremity disease is treated? There is general consensus that plaque excision is most valuable in those vessels with the largest plaque burden. Studies have confirmed high recurrence rates with SFA stenting and extensive dissections after PTA of long SFA lesions. Neither procedure addresses residual plaque burden, and both rely heavily on barotrauma for immediate angiographic improvement. PTA of SFA lesions with extensive plaque over a long segment is often associated with some of the most striking angiographic dissections we see in peripheral vessels. The dissections, thought by most to be required for PTA to improve luminal diameter, are caused by barotrauma. We can now perform extensive plaque excision in long lesions without barotrauma. Consequently, I expect to see better results as well as avoiding the cost and time required to deploy multiple stents.
What role do you think coronary plaque excision will play in today’s drug-eluting stent (DES) world? There is still a large number of patients with complex ostial, bifurcation, and in-stent restenosis lesions for whom treatment with DESs has been disappointing. Also, the economic impact of multiple DESs may make long-lesion treatment impractical. DESs face the same problem of plaque shift at ostial and bifurcation lesions as do bare-metal stents, and the role of DESs used to treat in-stent restenosis is not yet proven. If there is one area in which late thrombosis can certainly be a problem, it is this one. Even with modern antiplatelet therapy, it may be asking too much of Plavix and ASA to coerce the clotting system into ignoring two layers of stainless steel with dying cells between them. For in-stent restenosis, I predict that plaque excision will have a much more predictable long-term outcome with a much lower risk of subacute or late thrombosis when compared to DESs.
Given the amount of tissue this technique can capture, are there opportunities to analyze the plaque removed? The opportunities for characterizing the biological events associated with atherogenesis and restenosis suddenly expand dramatically. Isolation of RNA and DNA, which is problematic for small-biopsy–like specimens, is no longer a concern. In-stent restenosis lesions in the SFA can yield 300 mg to 400 mg of very consistent intimal proliferative tissue. Extraction of messenger RNA for these specimens will likely provide valuable information on gene expression and will require little if any amplification because of the amounts of message obtained. The same opportunities exist for de novo lesions, although the tissue’s heterogeneity will make the data interpretation more complex.
Where do you see this technology in the future? There are so many things we will do to improve the SilverHawk. My dream has always been to add visualization to the device. It will be like putting headlights on a car for the first time. We have experimented with IVUS, optical coherence tomography, and angioscopy. It is still unclear which will win the race. With imaging integrated, there will be few excuses for saying that rather than removing plaque, I will just stent it. You can stent it at anytime. My goal is to make sure that inserting a foreign body is not the first choice.