Virtual Histologic Guidance of Percutaneous Peripheral Atherectomy: The Evolution of a New Paradigm?

Percutaneous atherectomy has an evolving history with respect to peripheral arterial disease treatment. Although conceptually the idea of reducing plaque volume, and not merely “cracking” a plaque with angioplasty, makes sense, initial studies with first generation atherectomy devices did not show any benefit when compared with angioplasty alone.¹ Since then a number of percutaneous atherectomy devices have been developed with various theoretical benefits. The current generation include the Diamond back 360 (Cardiovascular Systems, St.Paul, Minnesota), Jet stream G2 (Pathway Medical, Redmond, Washington), and SilverHawk devices (ev3, Plymouth, Minnesota). Additionally, current approaches to percutaneous atherectomy include rotational atherectomy (rotablation) for peripheral vessels (Boston Scientific Corporation, Natick, Massachusetts)², cutting balloon (Boston Scientific Corp.; Angioscore, Fremont, California) and excimer laser atherectomy (Spectranetics, Colorado Springs, Colorado).³

Recent data suggest some efficacy with the current generation of devices. For example, Silverhawk atherectomy in 131 femoropopliteal lesions resulted in 12-month primary patency of 84% in de novo lesions and 54% in restenotic lesions with secondary 12-month patency of 100% and 93%, respectively.⁴ Jet Stream aspiration thrombectomy in 172 patients resulted in a 12-month target lesion revascularization of 26%.⁵ Similar data are available for other atherectomy devices mostly characterized by small sample size and lack of randomized, controlled, and adequately powered studies with suggestion of benefits compared with historical controls.

Virtual histology is designed to improve upon intravascular ultrasound imaging (IVUS). A color coded image is created from reflected IVUS signals on the arterial wall to create a virtual histologic map of plaque composition.⁶ This technology is currently being utilized in both the coronary and peripheral circulation and complements other plaque imaging technologies such as optical coherence tomography (St. Jude Medical, St. Paul, Minnesota) and near infrared spectroscopy (InfraReDx, Burlington, Massachusetts). Some initial studies have reported utilizing virtual histology to characterize plaque volume and composition changes with peripheral intervention and atherectomy.^6,7

In the current issue of the Journal, Singh et al⁸ report their experience with the Jetstream aspiration thrombectomy device and assessment of tissue removal using virtual histology with intravascular ultrasound.⁸ While the results reflect the experience of a very small cohort, the study itself represents the evolution of a new paradigm in peripheral intervention: the assessment of lesion specific characteristics to guide percutaneous outcomes. With the results of this study the authors report that the majority of vascular plaque is fibrotic in nature, and that atherectomy could achieve a decrease in fibrotic plaque volume of 17.4% with a 58% decrease in overall plaque volume. The study also confirmed that the necrotic core in atherosclerotic plaque is largely unaffected, as previously reported.⁷ Interestingly, they also report that overall burden of calcium is not affected by atherectomy. Further, this study lends credence to the fact that the Jetstream device truly performs atherectomy of the vessel, and does not merely “Dotter” it.

The concept of using intravascular ultrasound, virtual histology, and other imaging modalities to guide interventions is not novel and has been extensively used in the coronary circulation and makes sense clinically as a tool for peripheral intervention. In addition, non-invasive duplex ultrasound, CT, and MRI may also be used to characterize accessible peripheral vessels (presence of calcium, thrombus, soft plaque) and guide the choice of treatment modality. Adequate imaging is essential for peripheral interventions and aids in the choice among the multitude of devices available including the various atherectomy devices, angioplasty, and stenting. Virtual histology and other plaque characterization technologies will increasingly be used to assess peripheral lesions.

Atherectomy, however, is necessary only for lesions in areas that are not amenable to stenting [such as common femoral artery (Figure 1), bifurcations, contraindications to vascular surgery], and can only be universally recommended after well-designed, adequately powered, randomized, controlled trials are carried out to demonstrate its efficacy, safety, and cost-effectiveness. Furthermore, the true mechanism of plaque removal with the various atherectomy devices needs to be better elucidated through larger trials. Although both the Jetstream and Diamondback devices are supposed to perform atherectomy and plaque removal, a recent study of 1029 patients reported that both JetStream and Diamondback 360 devices have a higher rate of distal embolization.⁹ Unless these studies are performed or if its effectiveness is not proven superior to angioplasty/stenting, peripheral atherectomy will be relegated to “niche” applications as it did in the coronary circulation. The need for larger sheath size, distal embolization, time requirements, and cost limit its use unless its superiority is proven beyond doubt. It is surprising that tens of thousands of atherectomy procedures are performed annually with little data to support their use over angioplasty/stenting.

Finally, direct comparisons to endarterectomy and surgical bypass are needed to determine the preferred treatment strategy for specific patient and lesion subsets, as are well-designed trials comparing interventions to medical therapy, exercise, and risk factor modifications. The same scientific rigor that is applied to coronary interventions should be used for peripheral vascular disease treatment to elevate it from a field of small series, anecdotes, and personal experience to data driven therapeutic options that would provide the most efficacious and cost-effective treatment for patients.

References

1. Tielbeek AV, Vroegindeweij D, Buth J, Landman GH. Comparison of balloon angioplasty and Simpson atherectomy for lesions in the femoropopliteal artery: Angiographic and clinical results of a prospective randomized trial. J Vasc Interv Radiol 1996;7(6):837–844.
2. Henry M, Amor M, Ethevenot G, Henry I, Allaoui M. Percutaneous peripheral atherectomy using the Rotablator: A single-center experience. J Endovasc Surg 1995;2(1):51–66. 
3. Serino F, Cao Y, Renzi C, Mascellari L, Toscanella F, Raskovic D, et al. Excimer laser ablation in the treatment of total chronic obstructions in critical limb ischaemia in diabetic patients. Sustained efficacy of plaque recanalisation in mid-term results. Eur J Vasc Endovasc Surg 2010;39(2):234–238.
4. Zeller T, Rastan A, Sixt S, Schwarzwälder U, Schwarz T, Frank U, et al. Long-term results after directional atherectomy of femoro-popliteal lesions. J Am Coll Cardiol 2006;48(8):1573–1578.
5. Sixt S, Rastan A, Scheinert D, Krankenberg H, Steinkamp H, Schmidt A, et al. The 1-year clinical impact of rotational aspiration atherectomy of infrainguinal lesions. Angiology 2011;May 8 [Epub ahead of print].
6. Diethrich EB, Irshad K, Reid DB. Virtual histology and color flow intravascular ultrasound in peripheral interventions. Semin Vasc Surg 2006;19(3):155–162.
7. Aboufakher R, Torey J, Szpunar S, Davis T. Peripheral plaque volume changes pre- and post-rotational atherectomy followed by directional plaque excision: Assessment by intravascular ultrasound and virtual histology. J Invasive Cardiol 2009;21(10):501–505.
8. Singh T, Koul D, Szpunar S, Torey J, Dhabuwala J, Saigh L, Pires LA, Davis T.  Tissue Removal by Ultrasound Evaluation (TRUE STUDY). The Jetstream G2 System Post Market Peripheral Vascular IVUS Study. J Invasive Cardiol 2011;23:269–273.
9. Shrikhande GV, Khan SZ, Hussain HG, Dayal R, McKinsey JF, Morrissey N. Lesion types and device characteristics that predict distal embolization during percutaneous lower extremity interventions. J Vasc Surg 2011 Feb;53(2):347–352.

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From the Division of Cardiology, Interventional Cardiology Section, BIDMC/Harvard Medical School, Boston, Massachusetts.
The authors report no conflicts of interest regarding the content herein.
Address for correspondence: Roger J. Laham, MD, BIDMC/Harvard Medical School, 330 Brookline Avenue, Boston, MA 02215. Email: rlaham@bidmc.harvard.edu