The Crosser® CTO Recanalization Device (Bard Peripheral Vascular, Inc.) is a catheter designed to treat peripheral chronic total occlusions (CTOs) by forming a new canal within a blocked artery to allow subsequent endovascular treatment options such as angioplasty and stenting. With the Crosser® Catheter, a specialized tip transmits high-frequency vibrations directly to the CTO, ablating the plaque. The Crosser® Catheter is designed specifically to work against resistance, particularly in CTO caps and plaque with highly calcified components. In this article, we review how the Crosser® Catheter performs based on our clinical experience and describe our treatment algorithm.

MECHANISM OF ACTION

The Crosser® Catheter uses a combination of mechanical vibration and cavitation to create a channel. Cavitation is a unique feature of ultrasound-based technologies such as the Crosser® Catheter. The Crosser® Catheter will repeatedly apply force to the CTO cap until it finds its way across the lesion:

• Via cavitation and erosion of the CTO cap, and/or
• By direct contact and penetration of the CTO cap as it creates its own new path.

The Crosser® Catheter mechanism of action selectively engages inelastic materials such as plaque. Elastic materials like the vessel wall absorb the impact of the device, thus reducing the risk of perforation. Angiographically, when the Crosser® Catheter comes in contact with a vessel wall, it appears to stand still. Operators should be able to recognize this feature by looking at the Crosser® Catheter in multiple views. If contact with the vessel is confirmed, then the interventionist should use the recommended Usher® or Sidekick® Support Catheter to redirect the Crosser® Catheter device to engage the center of the CTO cap. In our experience, the interventionist can achieve crossing with higher success rates and lower complication rates simply by visualizing the device and ensuring contact between the tip of the Crosser® Catheter and the target lesion.

Using external ultrasound in conjunction with fluoroscopy while crossing a CTO (Figure 1) allows operators to see the tip of the support catheter and its vector direction, which one can then guide away from the vessel wall and direct into the center of the lumen. Once the support catheter is in the center of the CTO cap, the Crosser® Catheter is advanced, brought into contact with the surface of the CTO cap, and activated.

In the subsequent example, the Tibiopedal Arterial Minimally Invasive (TAMI) Retrograde Revascularization technique was used to treat a previously failed conventional antegrade crossing with a wire/catheter approach.1 The previous failure site was at the distal cap. In Figure 2, it becomes clear why the distal cap was difficult to cross. The cap possesses an antegrade convex CTO cap, and the antegrade crossing tools were deflected away from the center of the vessel, leading to a failure to cross. Here the TAMI technique was started via a retrograde access approach in the posterior tibial (PT) artery. Initially, EVUS-guided PT mapping and access in the transverse view were performed. The access wire and sheath were advanced in a longitudinal view followed by sheath placement. Figure 3 shows the retrograde Crosser® Catheter and its support catheter in contact with the retrograde concave CTO cap. With the addition of EVUS, operators have the ability to view the progression of the forward motion of the Crosser® Catheter as it penetrates CTO segments.

The Crosser® Catheter slowly penetrates the distal CTO cap with slight forward motion guided by slight pressure of the operator's hands on the Crosser® Catheter (Figure 3). Gentle forward pressure on the shaft is sufficient to allow the device to move forward through the CTO. This method of slight forward pressure on the device followed by a period of waiting and allowing the Crosser® Catheter to do the work is shown in Figure 4. Under fluoroscopy, the small movements of the Crosser® Catheter tip may not be visible as the catheter tip advances approximately 20 μm. Although the catheter may appear to be standing still, the catheter is still vibrating against the plaque. Hence, we have seen success after letting the device “activate and wait” during times where there was not visible forward movement.

The distal CTO cap was successfully crossed, so the focus shifted to the proximal CTO cap. Both distal and proximal CTO caps were crossed from a single retrograde access. Although EVUS is an extremely viable tool to aid in access and crossing in complex CTO cases, angiography still plays an essential and required role, especially during real-time flow evaluation of long arterial segments. This is shown in Figure 5, which is taken after complete revascularization of the long superficial femoral artery/popliteal CTO.

CATHETER CHARACTERISTICS

The Crosser® Catheter is a straight catheter available in three different configurations: 14S, 14P, and S6. The device is recommended to be used in conjunction with a support catheter for more support, torquability, and steerability. The Sidekick® Support Catheter is used with the 14S and 14P configurations and is available in straight and angled configurations and tapered and untapered versions. The Usher® Support Catheter is available in straight and angled configurations and all versions are tapered to work with the S6 Catheter.

CROSSER® CATHETER 14S AND 14P AND THE SIDEKICK® SUPPORT CATHETER

The Crosser® Catheter 14S and 14P feature a 1.1-mm diameter tip and are 0.014-inch guidewire compatible. The 14P is more flexible than the 14S and in our experience works best in the clinical conditions outlined below. The catheters are 5-F compatible on their own but are recommended to be used with the Sidekick® Support Catheter. The Sidekick® Support Catheter is labeled as 7-F compatible to permit contrast injection around the sheath. In our group’s clinical experience, we have found that the support catheter fits easily through a 6-F Pinnacle™ Destination sheath (Terumo Interventional Systems).

The Sidekick® Support Catheter comes in both angled and straight configurations. Because the Crosser® Catheter does not have an angled tip, it is clinically intuitive to use a combination of an angled Sidekick® Support Catheter and a Crosser® Catheter. This combination provides operators the opportunity to maneuver the Crosser® Catheter within the target vessel when using fluoroscopy alone or when using ultrasound-guidance with fluoroscopy.

One of the unique features of the Sidekick® Support Catheter we have found is its high torqueability, allowing interventionists to direct the Crosser® Catheter in 360º rotations within the lumen as they see fit. Also, the additional support of the Sidekick® Support Catheter is extremely valuable, as it allows the tip of the Crosser® Catheter to change vector directions.

CROSSER® CATHETER S6 AND USHER® SUPPORT CATHETER

The Crosser® Catheter S6 is different from the 14S and 14P in that it has a smaller tip and cross-sectional area of 0.6 mm. It also has greater drill efficiency due to the fact that the same energy delivered from the transducer is now concentrated via a smaller cross-sectional tip area. To accommodate the reduction in cross-sectional area, the wire lumen of the device was eliminated. As such, the S6 should be maneuvered with the aid of its accompanying Usher® Support Catheter.

The Usher® Support Catheter is designed specifically to support the Crosser® Catheter S6. The tapered lumen of the Usher® Support Catheter accommodates the tapered outer shaft of the S6. In our experience, this combination provides the operators with excellent torque of the Crosser® Catheter tip, controlled pushability, and vector redirection of the S6 tip while engaged in a CTO. The use of a support catheter with the Crosser® Catheter S6 has been useful in tortuous and complex CTOs, including severely calcified plaque. The angled tip of the Usher® Support Catheter provides significant value in directing the tip of the S6, maximizing exposure to the surface area of the CTO cap.

CATHETER SELECTION IN OUR PRACTICE

When we use the 14S: The Crosser® Catheter 14S is the workhorse device that can be used in all peripheral CTO segments, from the iliac arteries to, on rare occasions, pedal CTOs. The 14S has a stiffer support shaft than the 14P, allowing for higher pushability than the 14P.

When we use the 14P: Because the Crosser® Catheter 14P is more flexible it is able to track through more tortuous anatomy and we often utilize it in tortuous iliac CTOs or angulated tibial CTOs. It is also very effective in shorter CTOs.

When we use the S6: In comparison to Crosser® Catheter 14S and 14P, the S6 has a smaller tip and cross-sectional area with higher energy per sectional area. We have had a high success rate when using it in severely calcified lesions found in all vessels including the SFA, popliteal, and tibial.

OUR USE OF THE CROSSER® CATHETER

One of the most important and crucial steps in CTO crossing is engaging the CTO cap surface. In our experience, operators tend to aggravate the surface of the CTO cap during the attempt to engage it with a wire and catheter. This aggravation can lead to microdissections, specifically at the junction between the CTO cap surface area and the vessel wall. Whenever there is a dissection created at these junctions, they become a source of areas of lower resistance. This can create paths that other CTO devices will follow, especially when pushed, resulting in subintimal dissection during CTO crossing.

It is our recommendation to approach the CTO cap with a crossing device, rather than the wire, in order to avoid unnecessary aggravation of the CTO cap. In the case of the Crosser® Catheter, we advance a wire just proximal to the CTO cap. The support catheter is then advanced over the wire until just a few millimeters proximal to the CTO cap. Once in place, the Crosser® Catheter is advanced through the support catheter and becomes the first device to touch the surface of the CTO cap. Once contact is made, the operator generates a slight forward pressure on the device, which is usually reflected by seeing the support catheter push back from the CTO cap. Before activation, it is best to stabilize the support catheter and the Crosser® Catheter. The device is now ready for activation.

Upon activation of the device, there is no need to generate more forceful pressure on the Crosser® Catheter other than what was originally initiated. Additional pushing may result in the Crosser® Catheter tip sliding away from the center of the CTO cap onto the side, specifically the junction between the CTO cap and the vessel wall. Additional pressure can create an arc in the catheter shaft, which can be seen under fluoroscopy; this can lead the device away from the center of the cap. When this is seen, it is best to stop the activation of the Crosser® Catheter, pull it back, and readvance the support catheter. Reposition the Crosser® Catheter back on the center of the surface area of the CTO cap and reinitiate slight forward pressure of the Crosser® Catheter so that it is in complete contact with the surface of the CTO cap.

Once visualized, under fluoroscopy with or without ultrasound, activate the Crosser® Catheter and wait. It is best to continue to wait until motion is seen. Occasionally, you will find yourself waiting through multiple 30-second runs until the Crosser® Catheter finally penetrates the CTO cap. When using ultrasound, visualization of microbubbles where cavitation occurs and the constant burrowing of the Crosser® Catheter tip into the CTO cap gives the interventionist confidence that there is actual penetration of the CTO cap even when the Crosser® Catheter does not appear to be in motion under fluoroscopy. In our experience, patient waiting while the device crosses the cap increases the probability of crossing the CTO and lowers the probability of dissections. In our experience, perforation with the Crosser® Catheter is very low and tends to be associated with forceful pushing of the device.

CONCLUSION

In addition to fluoroscopy, EVUS provides direct visualization of the Crosser® Catheter S6, 14P, and 14S, allowing the operator to witness the fascinating science behind the device and its ability to accommodate the type of resistance it meets during the process of CTO cap crossing. Our experience with EVUS visualization of the Crosser® Catheter illustrates the device’s ability to cross challenging lesions and should encourage operators to “activate and wait” more often than before. Using the Crosser® Catheter in the manner described has resulted in our high crossing success rates in CTOs. In addition, the device’s selectivity for inelastic surfaces, such as plaque, coupled with the operator keeping the catheter properly aligned in the vessel has led to a low dissection rates in our practice.

Jihad A. Mustapha, MD, is the Director of Cardiovascular Catheterization Laboratories, Metro Health Hospital, Wyoming, Michigan; and Clinical Assistant Professor of Medicine, Michigan State University CHM and COM, East Lansing, Michigan. Dr. Mustapha has disclosed he is a consultant for Bard Peripheral Vascular, Inc. Dr. Mustapha may be reached at jihad.mustapha@metrogr.org.

The opinions and clinical experiences presented herein are for informational purposes only. The results from this case study may not be predictive for all patients. Individual results may vary depending on a variety of patient specific attributes. The physician has been compensated by Bard Peripheral Vascular, Inc. for the time and effort in preparing this article for Bard’s further use and distribution.

  1. Mustapha JA, Saab F, McGoff T, et al. Tibio-pedal arterial minimally invasive retrograde revascularization in patients with advanced peripheral vascular disease: The TAMI technique, original case series. Cathet Cardiovasc Interv. 2014;83:987-994.