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January 2011
Crossing CTOs With the Wildcat Catheter
Experiences using a new option for crossing difficult chronic total occlusions.
An increasing number of vascular specialists are employing a percutaneous intervention-first policy for the treatment of infrainguinal occlusive disease, particularly in patients at high risk for surgical procedures. This approach is based on recent reports of reduced morbidity and mortality with an intraluminal or subintimal endovascular approach.1,2 The BASIL trial3 substantiated this preference as well. This multicenter, randomized trial demonstrated essentially no difference in long-term outcomes between percutaneous and surgical revascularization in patients suitable for either form of treatment. Many patients prefer endovascular treatment because of its reduced cost, shorter hospital stay, and reduced procedural morbidity. However, if the patient's arterial occlusion cannot be crossed by percutaneous techniques, the patient will necessarily be relegated to a surgical procedure or, worse, amputation, depending on the arterial anatomy and patient comorbidities.
Crossing chronic total occlusions (CTOs) can be especially challenging if the proximal cap of the occluded arterial segment cannot be engaged or crossed with standard interventional technique. The medical device industry is attempting to address this problem with different types of devices. The corporate rationale behind these efforts is to improve crossing rates that then allow for the delivery of the therapeutic devices (angioplasty balloon, atherectomy catheters, cryoplasty, laser, etc.) to the target lesion.
The recent introduction of the Wildcat (Avinger, Redwood City, CA) as a support catheter has allowed our interventional practice to gain experience with this novel device. To date, 111 cases with the Wildcat (model W-400, 0.035-inch guidewire compatible) have been performed on difficult CTOs at our institution. The following cases demonstrate the utility of this catheter in clinical practice.
CASE 1
An 84-year-old man presented with severe rest pain of
the left foot for the past 3 months. Physical examination
revealed a femoral pulse but none distally. Vascular laboratory
data demonstrated an ankle-brachial index of 0.3 and
markedly attenuated ankle waveforms. A duplex scan
revealed a patent superficial femoral artery (SFA) and
popliteal artery occlusion.
He harbored diffuse coronary artery disease not amenable to percutaneous intervention. Angiography revealed a patent SFA and proximal popliteal artery. There was a distal popliteal CTO and severe tibial disease (Figure 1).
Attempts to cross the popliteal occlusion were initially unsuccessful. Multiple wire and support catheter combinations were tried. Excellent support and pushability were provided by a long sheath passed down just proximal to the occluded popliteal segment. Nonetheless, all manner of different caliber wires and supports were used to no avail. Subintimal angioplasty was then attempted without being able to penetrate the tough fibrous cap.
Exchange for the Wildcat catheter ultimately allowed for lesion crossing while maintaining the true lumen (Figure 2). A 6-mm SpiderFX embolic protection device (ev3 Inc., Plymouth, MN) was deployed to protect the disadvantaged tibial outflow. Atherectomy of the popliteal segment was performed with a SilverHawk device (ev3 Inc.). Improved tibial imaging at this point revealed occlusions of the anterior and posterior tibial arteries (Figure 3). The peroneal artery was occluded in the midportion. This was recanalized with a 2.5- X 150-mm NanoCross balloon (ev3 Inc.).
There was marked improvement in flow to the foot (Figure 4). The patient experienced immediate on-table resolution of his rest pain. Angio-Seal (St. Jude Medical, St. Paul, MN) closure of the arteriotomy was performed. There was no debris in the embolic protection filter.
The patient was discharged home 2.5 hours after the procedure on an antiplatelet regimen. At 1-week followup, his rest pain remained resolved. Color-flow duplex imaging revealed popliteal and peroneal patency. The patient continued to be ambulatory in his assisted living facility.
This case describes the first use of the Wildcat at our institution, allowing for successful limb salvage in a high-risk patient.
CASE 2
An 82-year-old man presented with progressive claudication
in his left lower extremity. He had been followed for the
past 2 years for stable claudication. Recently, his ambulation
distance fell to 50 to 75 feet, and his foot became numb if
he walked farther. Noninvasive vascular laboratory examination
revealed an ankle-brachial index of 0.55, and an SFA
occlusion was demonstrated by duplex exam. He had a
strongly palpable femoral pulse but no pulse distally.
Angiography documented an SFA occlusion (Figures 5 and 6). There was three-vessel tibial runoff. A Wildcat catheter was used to engage the CTO and subsequently cross through the true lumen (Figures 7 and 8). Atherectomy was accomplished with the TurboHawk device (ev3 Inc.) using the SpiderFX for embolic protection (Figure 9). The majority of patients with critical limb ischemia undergoing intervention at our institution have a filter placed prophylactically to prevent potential distal emboli and fully preserve distal runoff vessels. No debris capture was noted in this case. The procedure restored palpable pulses and resolved his disabling claudication.
DISCUSSION
The Wildcat was originally
manufactured as a
support catheter in a
0.035-inch caliber system.
The catheter is hydrophilic
coated and has excellent
pushability and trackability.
It is approved for use as a
standard support catheter.
In addition, it has a rotatable
tip that is manually
activated by turning the
device handle to which it is
connected (Figure 10). The
tip has both passive and
active configurations
(Figures 11 and 12). The active configuration is a more
aggressive tip profile that occurs when the “wedges” are
exposed out of the catheter tip by sliding the hand control
to advance them. If standard interventional technique does
not allow for wire and support passage, the Wildcat tip is
delivered to the proximal CTO cap. It is then used (with the
crossing wire retracted a short distance into the tip) to initiate
channeling through the proximal cap and CTO.
The tip is rotated in the passive mode first, and if the cap is not traversed, the active wedge mode is configured. The tip can be rotated clockwise, counterclockwise, or a combination of the two until the proximal cap is traversed and channeling is initiated.
At our institution, there has been no increase in the vessel complication rate with use of the Wildcat. The author has had no cases of perforation or embolization. It is recommended, however, that if the Wildcat is felt to be in a subintimal plane, the wedges should be in the retracted position (remain in “passive mode”). This should prevent engaging of the thin outer medial/adventitial layer, thereby preventing potential perforation.
Crossing times have been noticeably reduced in difficult CTOs with the Wildcat; however, the lesions most difficult to treat continue to be those that are highly calcified. The “active mode” configuration (with wedges out) seems especially suited to calcified lesions and can allow for channeling through densely calcified sections.
Another advantage of the Wildcat is that the stiffer catheter design and tip deflection allow for directing of the catheter away from large collaterals just proximal or at the CTO and back toward the occluded true lumen. This is in contradistinction to what typically occurs with catheter/guidewire combinations that routinely deflect into these proximal collateral vessels away from the intended target.
Generally, the Wildcat remains in an intraluminal rather than a subintimal plane with easier reentry into the true lumen distally. Although comparative data between intraluminal and subintimal lesion crossing are limited, there are theoretical advantages to remaining within the true lumen. These include improved crossing success rates, easier reentry at the distal extent of the lesion, decrease in procedural complications, and improved procedural patency.
FUTURE PROSPECTS
More recently, a 0.014-inch Wildcat catheter system has
been introduced. This low-profile device appears to have
applicability in CTOs in tibial vessels as well as those in the
SFA with a tight luminal or subintimal space. Unlike the
110-cm catheter length on the 0.035-inch system, the
0.014-inch catheter length is 140 cm to allow for access
of the distal tibial arteries from a contralateral femoral
approach. In addition, the wedges on the 0.014-inch system
are not retractable, remaining fixed and exposed (Figure 13).
A handheld motor drive unit will be an optional attachment
in the near future; design platforms are currently
undergoing testing.
The catheter has also been combined with optical coherence tomography visualization, which employs nearinfrared light to obtain high-resolution (< 10 µm) images. The first-in-man imaging occurred recently in Europe and was successful in demonstrating intraluminal and subintimal catheter positions. Improved vessel-wall imaging may allow for more precise therapeutic device delivery and successful interventions in the future.
Although currently approved as a procedural support catheter, the CONNECT (Chronic Total Occlusion Crossing With the Wildcat Catheter) trial is assessing the safety and efficacy of crossing superficial femoral and popliteal artery occlusions. This company-sponsored trial began in late 2010, and its current enrollment is already greater than 50% of the completion target.
CONCLUSION
Early experience with the Wildcat catheter reveals
utility in crossing difficult arterial occlusions. Further
refinements in crossing catheters throughout the industry
continue to address the need for crossing difficult
CTOs.
John P. Pigott, MD, is the Associate Director of Endovascular Surgery at Jobst Vascular Institute in Toledo, Ohio. He has disclosed that he is a paid consultant to and receives grant/research funding from ev3 Inc. and Covidien, and that he is an owner of or shareholder in Avinger. Dr. Pigott may be reached at (419) 291-2080; marilyn.gravett@promedica.org.
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