Commentary: Novel Crossing Devices vs the Skill of Artisans

Over the past decade, percutaneous endovascular therapy (EVT) has increasingly gained favor over traditional surgical bypass as the first-line approach to manage lower extremity peripheral artery disease. ¹ This shift has largely been dependent not only on the therapy being safe and less invasive but also on reasonable recent evidence that has shown the outcomes of EVT to be equivalent to those of surgical bypass. As the popularity of EVT has continued to rise, so has the development of various tools that have been found to improve the procedure methodology. This synergetic interaction between advances in dedicated materials and refinement of EVT techniques has improved the effectiveness of the therapy and expanded its indication even toward chronic total occlusion (CTO), which is considered to be the most challenging lesion subset. ²

The most significant impediment to successful EVT for CTOs is obviously crossing the lesion itself. The technical failure to cross the occlusion is the primary reason accounting for procedure failure in the majority of unsuccessful cases. ³ The challenging nature of CTOs has led to an ongoing interest in the development of specific guidewires (often with a stiffened and/or hydrophilic tip) and dedicated support catheters that have dramatically improved crossing rates along with a variety of specific recanalization techniques. However, the success rate of EVT for CTOs is still highly variable and heavily dependent on the operator’s advanced skills and expertise. These factors have spawned the development of a host of novel peripheral crossing technologies, and a number of dedicated mechanical crossing devices have been introduced in an attempt to provide a more reliable procedure success rate.^4–6

In this issue of the JEVT, Banerjee et al ⁷ compared the procedure success rates of specialized crossing devices vs a conventional strategy (manipulating a guidewire and microcatheter) in traversing infrainguinal artery CTOs in a contemporary multicenter EVT registry. The main finding of this study was that the crossing devices allowed primary success in intraluminal recanalization in 72.1% of the cases with few complications vs only 51.9% in the wire-catheter arm. This success rate with crossing devices is consistent with previous single-center experiences that demonstrated approximately 70% to 75% effectiveness for crossing devices in aiding operators recanalize peripheral artery CTOs.^4,5,8 The result of this study suggests that an initial CTO crossing device approach should be considered when treating a heavily calcified CTO that seems impossible to penetrate even with a weighted tip guidewire and a support microcatheter.

When conventional intraluminal crossing through a heavily or diffusely calcified vessel seems impossible, the most common alternative strategy for passage beyond the occlusion is subintimal angioplasty.^9–12 This is a deliberate attempt to establish a subintimal tract by intentionally creating a false lumen between the tunica intima and the tunica media, followed by a subsequent re-entry into the true lumen just distal to the occlusion. Since the advent of this subintimal recanalization technique, experienced peripheral interventionists generally achieve a technical success rate over 80% even when treating complex total occlusions in the popliteal and/or infrapopliteal vascular territory. In the study by Banerjee et al, ⁷ the primary success rate in the wire-catheter arm was only 51.9%, which is substantially lower than that given in earlier reports. This is unexpected because the majority of the lesions reported [244/295 (82.8%)] were in relatively larger vessels such as superficial femoral arteries (SFAs), and most lesions [138/244 (56.6%)] were relatively simple (TASC A or B). The reason for this considerably lower success rate in the wire-catheter arm is not sufficiently assessed and discussed in the article. In my opinion, it is likely that the operators did not stick to guidewire manipulation and simply switched to the crossing device approach when this was available.

One of the chief advantages of the crossing devices for peripheral CTOs is that, unlike the manipulation of guidewires, only minimum training is required to operate them. With conventional guidewire and microcatheter techniques, there is a wide variation in success rates that can significantly be attributed to operator expertise and experience. On the other hand, with dedicated crossing devices, a certain level of satisfactory results can be achieved even in the hands of less skilled operators because the methods of operating the devices are generally simple and easy (eg, just push forward slowly). One meaningful finding of this study is that the rate of successful recanalization of the popliteal or infrapopliteal arteries with the crossing devices was similar to that for SFAs, albeit that the number of cases investigated was small. Recanalization of the below-knee vascular territory is generally challenging even for skilled operators because of the smaller vessel size.

It should be noted that, in this study, dedicated “re-entry” devices that are specially designed to aid distal re-entry into the true lumen were required in addition to the crossing devices in ~30% cases to traverse the entire occlusion. Because directional navigation of the crossing devices is potentially impossible, there may have been difficulty in regaining access to the distal true lumen once a large subintimal space was created with the devices. Indeed, the additional use of another crossing device did not improve the procedure success rate at all in the crossing device arm. Furthermore, final procedure failure eventually ended up at almost 10% even when dedicated “crossing” and “re-entry” devices were combined.

When re-entry into the distal true lumen fails, one viable option is the “retrograde approach,” a converse approach from the same distal lumen. The retrograde approach (eg, a popliteal or tibial ¹³ or a transcollateral ¹⁴ approach) has drastically improved the revascularization success of EVT to almost 100%, even in very challenging peripheral CTOs,^13,15,16 and it has been widely adopted by an increasing number of interventionists who treat advanced peripheral artery disease.^2,17 This alternative technique provides a useful solution for traversing CTOs when (1) the antegrade attempt to cross is unsuccessful, (2) the proximal entry of the occlusion is flush with the origin of a bifurcation or collateral artery, or (3) the dense atheromatous plaque or excessive calcification at the distal end of the occlusion precludes the re-entry device from creating a connection into the distal true lumen. However, the retrograde approach requires specific anatomical conditions, such as at least one patent infrapopliteal artery or the presence of a collateral artery appropriate for accessing. Access site complication is also a serious concern. Finally, the retrograde approach, unlike the crossing device method, requires a high degree of skill and is associated with a learning curve.

Currently, the development of dedicated crossing devices and advancement of the operators’ guidewire technique seem to be complementary. Although the authors proclaimed the superiority of novel crossing devices in penetrating peripheral CTOs, a nonnegligible proportion of patients were left with unsuccessful endovascular recanalization. In addition, the initial use of crossing devices did not reduce the procedure time and contrast volume as expected. The overall procedure cost may also be an issue. For the meantime, improvement in the clinical outcome for patients with peripheral artery occlusive disease will likely continue to depend on a comprehensive therapeutic algorithm that carefully melds both operators’ skills and techniques with emerging technologies.