Abstract
The Outback™ Elite re-entry catheter (CORDIS, Cardinal Health, USA) is designed to facilitate placement and positioning of guidewires within the peripheral vasculature and allows for re-entry of a guidewire back into the true lumen of a vessel following a subintimal crossing of an arterial occlusion. The device was first introduced in 2005 and has become widely utilized in a variety of situations involving both arterial and venous interventions. This article aims to share our experiences with the Outback™ device and inform interventionalists of its utility and versatility.
Introduction
The Outback™ re-entry catheter is an established device manufactured by Cordis (Cardinal Health, USA). It was created to facilitate re-entry of a guidewire back into the true lumen of a vessel following subintimal crossing of a chronic arterial occlusion. The device was first introduced in 2005 and incorporates a hollow 22G needle than can be advanced through a side port at the tip for luminal re-entry under fluoroscopic guidance.
The Outback™ catheter is a single-lumen device with a sheathed curved nitinol needle just proximal to the tip. The outer 5.9Fr shaft, compatible with a 6Fr sheath, has 2 distal holes, one at the end and another 5 mm proximal to this on the side. A co-axial inner catheter is connected to a radio-opaque, extendable and directable radiopaque guide tip. The curved needle lies coaxially and straightened in the outer catheter. Initially, the catheter is usually advanced over an 0.014-inch guidewire to the intended re-entry point with the needle retracted. Using 2 fluoroscopy projections orthogonal to one another, the device is rotated until the “L” marker points toward intended lumen re-entry point and the “Ʇ” marker is superimposed on the lumen. The curved needle is then directed into true lumen using the external handle on the device. A compatible 0.014-inch guidewire is then passed through the needle into the lumen of the target vessel. The needle must always retracted before device removal over the wire. The rest of the procedure may then be carried out as normal. In our practice, we mostly use the Hi-Torque Command ES (Abbott) or PT2 Moderate Support (Boston) guidewires, although Cordis provide a more extensive list of compatible guidewires in the instructions for use (IFU).
Prior to the introduction of the Outback™ catheter, the endovascular options for subintimal crossing of chronic total occlusions were limited. These included the standard wire loop technique which is not always successful if the wire does not spontaneously re-enter the vessel lumen. 1 The SAFARI (Subintimal Arterial Flossing with Antegrade-Retrograde Intervention) technique is another alternative, although the distal vessels are often not suitable to puncture in patients with severe peripheral vascular disease. 2 In addition, during SAFARI the retrograde wire may fail to break back into true lumen, thus resulting in 2 separate subintimal channels. There is also a small risk of injury to the distal vessel at the point of retrograde access.
Using our experience with the Outback™ device, we offer advice on how to deploy the device most effectively. This includes its use in the aortoiliac and femoropopliteal segments, the infra-genicular vessels and in chronic venous disease. This article discusses our experience with the wider applications of the device and summarizes its clinical use. Informed consent has been obtained from all patients for publication of the images. Institutional approval was also sought and received for the use of any images.
Tips and Tricks
In order to use the device effectively, both ports need to be flushed at regular intervals. This includes immediately before insertion into the patient and as soon as it is removed (if the operator intends to use it again). We would also advise not to leave the device inside the body for too long, as the wire may dry out and stick to the inner catheter lumen. If the device is required to remain intravascular for a long period of time, it can be removed and flushed prior to re-insertion.
When there is difficulty in delivering the device to its intended destination, for example, due to heavy calcifications, we recommend the following: The use of a long 6-French sheath to provide extra support. Pre-dilation of the tract to 2.5 mm
Another strategy which can be combined with the above or used independently is to advance the catheter over a stiff 0.018-inch guidewire. It is important to note that once this is successful, it is important to exchange back to an 0.014-inch wire prior to needle firing. In cases involving going “up and over” the aortic bifurcation (especially in steep bifurcations), we would advise the use of a 7Fr sheath to track the device.
Thick calcifications at the site on intended re-entry can stop the needle from penetrating back into the vessel, causing the device to retract. During needle firing, if it pushes back against heavy calcium, there are 2 options. Firstly, a second operator should support the device by holding the catheter at the sheath hub. Alternatively, constant gentle forward pressure should be applied during needle advancement. We also maximally magnify the image (with digital zoom if available to reduce radiation exposure) in order to more accurately identify a gap in the calcium or where the deposits are thinner, i.e. more favorable for re-entry (Figure 1). If at this point, there is still difficulty in advancing the needle into true lumen (either due to a high calcium burden or difficulty in rotating the device to the correct position), it may be necessary to fall back on a technique we are terming “modified SAFARI” if a suitable distal vessel is available to puncture. The Outback™ device may be employed in conjunction with the SAFARI technique (also shown in Figure 1).
The Outback catheter has been inserted retrograde into a heavily calcified superficial femoral artery (A-B). By magnifying the image, we identified a gap in the calcium, to allow for the needle to access the vessel lumen (C).
If the Outback™ Catheter becomes stuck on wire after apparently successful re-entry, advancing more wire (if possible) and flushing the side port with a 2 ml syringe should be effective. Otherwise, the catheter and wire should be removed en-bloc (the needle needs to be withdrawn back first) and an attempt made to quickly cross the break-back point with a catheter and wire.
The outback catheter in aortic intervention
Aorto-femoral bypass surgery (with or without femoral endarterectomy) has traditionally has been considered the gold-standard treatment for those patients with aorto-iliac occlusive disease causing life-limiting claudication (that fails to respond to best medical therapy and supervised exercise) or critical limb ischemia. However, recanalization of occluded iliac vessel(s) is an alternative technique to open aortic surgery, especially in patients with multiple co-morbidities. 3 Covered endovascular reconstruction of the aortic bifurcation (CERAB) has been introduced as an alternative treatment with early outcomes comparable to those of surgical treatment. 4 The Outback™ is an effective adjunctive tool for the recanalization of severe iliac or aorto-iliac CTOs following subintimal crossing. 5 We present a case of a CTO of the left common iliac artery (Figure 2) and a CERAB (Figure 3) with use of this device.
A 74 year old patient with an occluded right iliac system presented with right leg CLI. Pigtail angiography from the contralateral access allowed visualization of our re-entry point within the aorta (A-C). After a subintimal tract was established, the aorta was targeted accurately by rotating the Outback™ device to orientate the “L” and “T” shapes of the catheter pointing toward the vessel. A wire was then passed through the needle successfully entering the aorta (D-F).
A 63 year old patient with bilateral rest pain secondary to a chronic aorto-iliac occlusion (A). With angiography from the arm (B-C), the Outback™ was used on both sides to gain access into the aorta after crossing the common iliac arteries subintimally (D-E). Covered aortic and iliac stents were deployed as part of a Covered Endovascular Reconstruction of the Aortic Bifurcation (CERAB) procedure (F).
Use of the outback™ for infragenicular vessels
It has been shown that the Outback™ device is safe to use in infragenicular vessels, with data suggesting good results. 6 In our experience, the Outback can be inserted as far as just above the level of the tibiotalar joint. Usually the hydrophilic coating of the device will allow it to pass through the subintimal tract immediately although, occasionally, pre-dilatation of the tract with a 2 mm balloon may be required. As the distance between the targeted true lumen and the re-entry device will be shorter (along with the smaller diameter of crural vessels), the Outback™ needle does not always have to be fully deployed or can be deployed then partially retracted as necessary. When aiming for a small target vessel, it may be easier to advance the needle “through and through” the target then gradually retract the tip of the needle until it is in the true lumen and the wire passes. Figure 4 demonstrates safe use of the device in crossing an occluded tibioperoneal trunk. Figure 5 demonstrates the utility of the device as a selective catheter in below the knee vessels, selecting and crossing a short segment occlusion of the posterior tibial artery.
A long segment occlusion of the tibioperoneal trunk (A) is crossed subintimally, and the Outback™ used to re-enter the lumen (B). This vessel was subsequently stented (C-D).
In this case, there is an occlusion of the tibioperoneal trunk, which was crossed with a 0.014 wire into the peroneal artery. This tract is ballooned, leaving a short segment flush occlusion at the origin of the posterior tibial (PT) artery. The Outback catheter was used to direct a 0.014 wire into the PT origin, allowing for wire access and subsequent deployment of kissing balloons.
Re-establishing access from an extraluminal space
Percutaneous intentional extraluminal reconstruction is a useful percutaneous technique for limb salvage in patients with chronic critical limb ischemia (5). The Outback™ device can aid in this task as shown in Figure 6.
The Outback™ was deployed in a the mid/distal posterior tibial artery (A-B). It was not possible to maintain a subintimal tract and an extraluminal channel was formed (C). Luminal access was re-obtained with the device and then a covered stent then deployed (D-E).
Balloon puncture using the outback
When direct luminal re-entry with the Outback™ device is not possible, re-entry by puncture of an inflated target balloon may be attempted. 7 This technique can be used in arteries or veins. A target balloon is inserted from a distal access point (e.g. a tibial vessel in SAFARI) and advanced retrograde in the true lumen or subintimal space. The antegrade Outback™ device is positioned alongside the luminal balloon, which is inflated. The Outback™ needle is deployed toward the balloon, with successful balloon puncture confirmed when there is loss of pressure from the manometer as well flow of contrast medium from the inflated balloon seen on fluoroscopy. The 0.014-inch guidewire is advanced into the balloon and coiled, then the balloon catheter removed while the guidewire is simultaneously advanced and held within the balloon lumen during retraction. Once the guidewire is externalized it is clamped to secure. These steps are depicted in Figure 7.
A popliteal artery with an occluded previous bypass (A). The Outback™ was used in an antegrade fashion to puncture a balloon that had been advanced retrogradely (B). The “L” was aligned to the balloon which was then punctured allowing for the device wire to be advanced into the tract occupied by the balloon (C). This allowed for the wire to be snared in order to obtain through-and-through access (D).
Use in the venous system
Chronic iliac or iliocaval venous obstruction can result in the development of post-thrombotic syndrome. Even with the use of sophisticated chronic total occlusion guidewires and support catheters, intraluminal recanalization of a chronically obstructed post-thrombotic veins is occasionally not successful. Re-entry devices are used when guidewire passage back into the true lumen is not possible and the balloon puncture technique described above may be used. 8 We present such a case in Figure 8.
A case of establishing a luminal channel in a hypoplastic inferior vena cava (IVC) (A). Access was obtained from both femoral veins as well as the right internal jugular vein and wires were advanced adjacent to each other within the retroperitoneum using antero-posterior and lateral views (B). Initially we inserted the Outback from below but were unable to advance the device adequately to reach the caval balloon (C). Subsequently, the Outback was inserted from the right jugular access and the balloon from below. Careful orientation was needed to avoid the aorta before balloon puncture was performed (C-D). The final images shows successful ileocaval stenting (E).
Unusual situations
Figures 9 and 10 show uses of the Outback™ device in uncommon situations. Figure 9 shows it use to recanalize a ligated superficial femoral artery following common femoral artery endarterectomy. Figure 10 shows a case where the device is used to directly puncture a PTFE graft.
This patient had a previously ligated superficial femoral artery following a common femoral endarterectomy and patch plasty. Retrograde access was obtained via a high popliteal puncture. And up and over sheath allowed for angiography to be performed in order to obtain a target re-entry point. Once re-entry was achieved, the wire was snared in order to obtain through-and-through access.
A case of an occluded PTFE interposition graft in the CFA. The graft was punctured using the Outback Device via retrograde access and in-line flow re-established. The red arrows show how wire access is obtained to as close to the position of the graft as possible prior to the deployment of the Outback device.
Conclusion
The Outback™ catheter can be used effectively in the aorto-iliac, infra-inguinal and venous vascular segments with a good safety profile. We present a variety of cases in which the Outback can be successfully deployed and have outlined a number of technical points to aid the interventionist when using this versatile device.
Footnotes
Declaration of Conflicting Interests
The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding
The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: Narayanan Thulasidasan & Athanasios Diamantopoulos have received funding from CORDIS, Cardinal health for delivery of educational presentations as well as travel support.
