Peripheral Arterial Vessel Prepping With Intravascular Ultrasound and Atherectomy: An Interventionalist’s Perspective

Abstract

Background. Vessel prepping is an essential component of an optimal strategy in treating infrainguinal peripheral arterial disease. Vessel prepping with atherectomy can be aggressive in certain lesion morphologies, such as severe calcium, total occlusion, or in-stent restenosis, or can target vessel compliance without aggressive debulking. Drug elution is likely to be enhanced by vessel prepping. Optimal vessel prepping requires precise imaging of the vessel size, plaque morphology, and lesion severity/length which cannot be assessed adequately by angiography. Also, intravascular ultrasound provides information post treatment on minimal luminal area gain, residual dissections, geometric miss, and stent apposition and expansion.

Reprinted with permission from J INVASIVE CARDIOL 2021;33(2):E95-E98.

Key words: atherectomy, dissection repair, dissections, intravascular ultrasound, outcome, vessel prepping

Vessel prepping (VP) with atherectomy of the lower extremity arteries prior to definitive treatment is often used by endovascular specialists to improve vessel compliance and reduce barotrauma and subsequent dissections.^1-3 The goal of VP is to reduce the arc of dissection to limit acute/subacute closure and to prevent deeper damage into the media and adventitia, which is associated with a higher rate of restenosis.^4,5 Bailout stenting is also reduced, which is highly desirable in the “no” or “least” stent zones, such as the common femoral, popliteal, distal superficial femoral and infrapopliteal arteries. Shifting from simply improving compliance to aggressive debulking may be important when treating in-stent restenosis (ISR) and severely calcified arteries. In ISR, the hyperplastic tissue has high water content and the gain by angioplasty alone may be later offset by a rehydration mechanism and re-expansion of this tissue. In the case of severe calcified lesions, debulking superficial atherosclerotic calcium may not be sufficient and an aggressive approach to reach the deeper layers may be necessary. The potential benefit, however, of aggressive debulking can be offset by dissections, embolization, perforations, and a potential increase in restenosis despite an initial significant gain in minimal luminal area. Whether operators use atherectomy for changing vessel compliance or for aggressive debulking, drug elution is likely to be enhanced,^6-9 particularly in calcified vessels, ISR, or chronic total occlusions, and this may offset some of the negative effects of vessel injury.

There are several VP devices, including atherectomy and non-atherectomy options. Atherectomy devices include directional with imaging (Pantheris; Avinger) or without imaging (Hawk; Medtronic); rotational such as the Jetstream (Boston Scientific), Rotablator (Boston Scientific), orbital (Cardiovascular Systems, Inc), Phoenix (Philips), and Rotarex (Straub Medical); and the excimer (Philips) or Auryon lasers (Angiodynamics). Non-atherectomy devices mostly target compliance change with no actual debulking. These include scoring balloons (eg, AngioSculpt; Philips), focal force balloons (eg, VascuTrak; BD/Bard), Chocolate balloon (Medtronic), and the Cutting balloon (Boston Scientific). Recently, the Flex VP atherotome (VentureMed Group) and the Lithoplasty balloons (Shockwave) have been introduced. All of these devices are part of the triad of optimal peripheral arterial intervention, which includes VP, antiproliferative therapy, and outflow protection from distal embolization.^10,11

Despite debulking and a trend favoring atherectomy over angioplasty, atherectomy has proven its benefit in reducing angiographic dissections and bailout stenting when compared with percutaneous transluminal angioplasty (PTA), but had no statistically demonstrable effect on target-lesion revascularization (TLR).^1,12 It is unclear why atherectomy has not yielded a strong positive outcome despite an initial significant increase in procedural minimal luminal gain. Insights from intravascular ultrasound (IVUS) may provide some clues that could explain the long-term outcomes of an atherectomy procedure and assist the operator in choosing the appropriate device. Data suggest that aggressive debulking with atherectomy will likely damage the deeper layers of the vessel and generate wider dissection flaps, leading potentially to higher restenosis⁴ and acute/subacute thrombosis rates, respectively. Angiography has clear limitations. It is not able to show the number and severity of dissections, including medial and adventitial injury, the residual narrowing post intervention, severity of calcium, the presence of intraluminal thrombus, plaque morphology, and vessel diameter.

IVUS is helpful in every step of the procedure.^5,13 In the predebulking phase, IVUS shows the true lesion severity, plaque morphology (calcified, fibrocalcified, fibrotic), plaque extension, vessel size, and wire location (intraluminal/subintimal/intramedial), and influences device choice. In the posttreatment evaluation, it demonstrates dissection arc and depth and influences the next step of treatment, such as the need for spot stenting or use of the Tack Endovascular system (Intact Vascular) for dissection repair, or additional balloon inflation (size, length, time of inflation).^14,15 In addition, IVUS post debulking/adjunctive treatment clarifies the true luminal gain and stent apposition/expansion, and identifies area of geometric miss and dissections. At present, only optical coherence tomography (OCT) is available on the Pantheris (Avinger) device to assist in visualizing the vessel during debulking to pre-emptively avoid damage to the adventitia. Figure 1 illustrates the IVUS/atherectomy combined approach to treating infrainguinal arteries. Lesions are divided into calcified/chronic total occlusion, ISR, or less calcified/stenotic but not occluded vessels. We generally pursue an aggressive approach (residual 30%-40%) post atherectomy for total occlusions and severely calcified vessels given the bulky nature of these lesions. We approach non-occluded and mild-to-moderately calcified lesions with a soft debulking approach (residual narrowing of 45%-50% or reducing the plaque by 30%-40%) to alter compliance predominantly and reduce the chance of dissections and stenting.

Recently, IVUS-based classification of dissections (iDissection) was published combining parameters of depth (A = intima, B = media, C = adventitia) and arc (1 = <180°, 2 = ≥180°).¹⁶ Several prospective, core-lab adjudicated studies have shown that on average, the number of dissections seen on angiography versus ultrasound was ~6:1. In addition, 39.1% of dissections involved the media and/or adventitia. Furthermore, the circumference of dissections appeared to be <180° in 87% of cases, but it was a wider arc in 13% of cases.¹⁴ In the iDissection atherectomy study,¹⁴ aggressive debulking (predominantly with the Jetstream device) led to high procedural success at the expense of more dissections. In the JET SCE study,⁹ however, using the same device and techniques, the addition of drug-coated balloons (DCBs) negated many of the negative effects of these dissections; freedom from TLR was significantly higher with atherectomy and adjunctive DCB vs atherectomy with adjunctive PTA at 12 months (94.7% vs 68.0%, respectively; P<.01) and 16 months (94.4% vs 54%, respectively; P<.01). Stenting was performed in 21.3% of the treated vessels. This raises the question of whether repair of these lesions beyond what we see on an angiogram is warranted if many of these angiographic dissections are not flow limiting. Recently, however, a decline in paclitaxel-eluting device use was observed following the published data by Katsanos et al.¹⁷ Katsanos et al noted an association between paclitaxel devices and 5-year mortality increase. Although subsequent studies did not confirm these findings,^18-20 several operators continue to avoid paclitaxel-coated balloons or stents.

Lower patency and higher TLR rates are evident with treatment of the infrainguinal arteries with PTA alone when compared with the use of DCB or drug-eluting stent.²¹ For instance, Jetstream atherectomy shows a higher TLR rate when no adjunctive DCB is used.^9,22 Would repair of IVUS-identified dissections improve patency and lower TLR without the use of DCB? Data from the TOBA II study,²³ which included both DCB-treated and non-DCB treated vessels, showed that repair of angiographic dissections with angioplasty led to an excellent outcome irrespective of DCB use. In fact, Kaplan-Meier patency in the PTA group at 1 year was 89.6%. Would a more targeted and complete dissection repair of higher arc and deeper dissection resulting from aggressive debulking by atherectomy and adjunctive angioplasty and as seen on IVUS lead to a superior outcome? Unfortunately, without a coregistration software (similar to the coronary SyncVision from Philips) that superimposes IVUS to angiographic images in the periphery, a targeted IVUS-based repair of these dissections is unlikely to be adequately tested at present.

One of the key advantages of IVUS over angiography when performing endovascular procedures is optimal vessel sizing,^15,24 which was demonstrated prospectively and with core-lab adjudication in the recent iDissection below-the-knee study.¹⁵ This was also shown in a retrospective study by Pliagas et al²⁴ using digital subtraction angiography vs IVUS. Vessel size was noted to be underestimated by about 25% in the iDissection below-the-knee study,¹⁵ which may have several implications on choice of balloons and other therapies. In order to gain maximum lumen diameter, an adequately sized balloon is needed. Undersized balloons are likely to lead to suboptimal lumen gain. Also, undersized DCBs will likely have an impact on adequate drug transfer into the vessel wall. Finally, the choice of the atherectomy device relies on accurate sizing of the vessel to achieve adequate debulking and optimal lumen gain.

In my opinion, IVUS is poised to be a critical tool in peripheral vascular interventions. Advancing the science of IVUS in peripheral intervention will require the development of an IVUS coregistration software with angiography to facilitate clinical trials in this field and to enhance each operator’s ability to perform targeted therapy confidently. In the interim, the use of IVUS will likely significantly alter the operator’s choice of technique and device selection, particularly with VP in general and specifically with the use of atherectomy.

From the Midwest Cardiovascular Research Foundation, Davenport, Iowa.

Disclosure: The author has completed and returned the ICMJE Form for Disclosure of Potential Conflicts of Interest. Dr Shammas reports educational and research grants and is a trainer for Boston Scientific and Bard.

Final version accepted September 2, 2020.

Address for correspondence: Nicolas W. Shammas, MD, MS, Research Director, Midwest Cardiovascular Research Foundation, 1622 E. Lombard Street, Davenport, IA 52803. Email: shammas@mchsi.com