Peripheral arterial disease is a common medical condition that affects millions of people in the United States and all over the world. It can lead to significant morbidity, such as claudication, resting leg pain, ischemic ulcers, gangrene, and limb loss, which in turn can lead to an increased mortality rate.1 Prompt diagnosis and treatment of this condition can lower mortality and amputation rates. Mechanical revascularization of the ischemic limbs can be achieved either by surgical treatment of the diseased segment (eg, femoropopliteal artery bypass surgery) or percutaneous revascularization (eg, angioplasty).

Refinement and improvement of percutaneous revascularization techniques in recent years have made this the preferred approach over more invasive surgical approaches in many cases.2-4 However, there are multiple technical challenges if the disease manifests itself as a chronic total occlusion (CTO) of a major artery, especially if it involves a long segment. A CTO is defined as a lesion that is present for more than 3 months with no angiographic flow.5 Revascularization of a CTO in the ischemic limb by percutaneous transluminal angioplasty is technically challenging and complex, as failure to successfully revascularize the limb may impair pre-existing blood flow to the extremity. Different techniques have been described to achieve angiographic success in CTO recanalization. The technical success rate in peripheral CTOs is variable and depends on lesion characteristics, vessel characteristics, and operator experience.6

Percutaneous transluminal angioplasty techniques for CTOs are based on central lumen crossing (either with a wire or a crossing device) or a percutaneous intentional extravascular revascularization (PIER) approach with or without the use of a reentry catheter.7 The former technique often fails to remain in the true lumen; by the time the wire or the catheter reaches the distal landing zone, interventionists often find that they are far outside of the true lumen and spend considerable time trying to reenter the true lumen. This often has frustrating short- and long-term results.

The PIER approach, initially described by Bolia in 19908 is based on the creation of a subintimal channel with reentry into the distal true lumen. This technique carries a reported failure rate of 10% to 20% due to an inability to reenter the distal true lumen.8 Use of reentry devices improve chances of entry into the distal lumen, but despite angiographic success at the end of the procedure, clinical success is between 50% and 70%, and primary patency is approximately 50% at the end of 1 year.9 It may also create an undilatable neck composed of a very tough fibrous tissue at the reentry point, which can become a nidus of restenosis, stent fracture, and occlusion. There is also increased risk of dissection, perforation, and pseudoaneurysm.10 Other drawbacks include extension of injury into the nondiseased distal reference and loss of collateral vessels both within the lesion and in the proximal and distal reference.11

To overcome these potential shortcomings, we propose the concept of true lumen angioplasty using an intravascular ultrasound (IVUS) reentry catheter to remain in the true lumen. It consists of a technique to reorient the wire so that continued passage through the true lumen takes place at the point of deflection into the subintimal plane. Potential benefits include preservation of collaterals, lowered risk of perforation during atherectomy, and limiting the extension of injury into the proximal and distal references to preserve possible future surgical targets.

DEVICE DESCRIPTION

The Pioneer Plus diagnostic ultrasound transducer and percutaneous catheter (Volcano Corporation, San Diego, CA) is an IVUS-based device used for reentry into the true lumen.12 It utilizes a 27-gauge, IVUS-guided penetration needle located proximal to the imaging element. The device is a dual-lumen monorail catheter that tracks over a 0.014-inch guidewire. The tip of the catheter contains an integrated 64-element, phased-array, 20-MHz IVUS transducer, which works in combination with the family of Volcano IVUS consoles, including s5, s5i, and the new Core systems (integrated or nonintegrated). Based on this technology, the device allows visualization of the vessel morphology and helps to identify blood flow in the true vessel lumen via a color-flow mode (ChromaFlo feature). The second lumen of the catheter contains a curved puncture needle for penetration of the tissue plane separating the true from the false lumen, which allows advancement of a 0.014-inch guidewire into the true vessel lumen. The penetration depth of the needle can be adjusted from 1 mm up to 7 mm and is controlled at the handle bar of the catheter.

METHOD

Initial attempts to cross the CTO are performed using a central lumen crossing catheter. We learned from our experience, and from a multicenter study, that we can expect to cross a wire-resistant CTO in > 80% of lesions. This approach is associated with lowered rates of perforation, restenosis, and repeat revascularization in comparison to the PIER approach.13

During the attempt, if the central lumen crossing catheter deflects laterally or medially, we pass a wire through the central lumen of the device and remove the catheter. The Pioneer Plus catheter is then guided to the point of potential deflection in order to ascertain the orientation of the wire (Figure 1). In rare instances of severe intraluminal calcification, the catheter may be unable to cross, and predilation may be necessary for catheter delivery.

If the wire is found to be within the lumen, the Pioneer Plus catheter is removed, the central lumen crossing device is reinserted, and the procedure is continued. If the wire is observed to be deflecting into the subintimal space, the absolute point of deflection is established for luminal reorientation.

The needle, being proximal to the imaging element, is within the lumen proper and purely eccentric. By reorienting the direction of the wire, continued central lumen crossing can commence. To safely deploy the needle, the correct rotation of the device should be verified with IVUS so that the wire can be seen either entering the total occlusion at a safe distance from the IVUS transducer or, optimally, within a microchannel in the total occlusion (Figure 2).14 To optimize image quality, the range of the image should roughly double the diameter of the vessel. In an average-sized superficial femoral artery, an image view of 14 mm is suitable for most crossings. ChromaFlo should be turned on, and the sensitivity of the ChromaFlo image should be set to 5. The graticules on the image are 1 mm in distance. By counting the graticules to a safe distance from the deflection point, reorientation can be achieved. After the needle is advanced, the operator should be able to observe the wire at a significant distance from the transducer. If the wire is observed within the false lumen that the Pioneer Plus catheter occupies, it should be retracted, and the needle depth should be increased by 2-mm increments until the wire is no longer observed within the false lumen (Figure 3).

After reorientation is confirmed, the Pioneer Plus catheter and its central wire are removed, leaving the reoriented wire within the vessel (Figures 4 and 5). At this point, reinsertion of the central lumen crossing catheter into the true lumen should be attempted in order to continue crossing. This procedure is repeated with each instance of deflection until the wire exits through the center of the true distal cap of the CTO.

DISCUSSION

The Pioneer Plus catheter is currently considered to be a bailout device that is intended for use in achieving distal access in PIER crossings of totally occluded arteries after initial attempts at reaching the distal vessel with wires and support catheters fail. In our experience, the observed anatomic disruption of the superficial femoral artery is considerable, even in the presence of rapid entry into the distal vessel.

Both references in PIER techniques can be considerably affected, with loss of collateral circulation and extension of the treatment site. Lipsitz reported that 47% of all collaterals distal to the total occlusion are lost as a result of PIER crossings.11 These losses could result in acute limb ischemia or a threatened limb in the presence of restenosis. Intralesional collaterals, which are routinely completely lost in PIER approaches, may become the new reference collaterals if the vessel restenoses and the new total occlusion is shorter than the original lesion. Their importance and the need for their preservation can be nearly as critical as those of the reference collaterals.

Coupled with injured references, the implications of restenosis can be grave and may necessitate amputation. Preservation of the distal reference and the distal collaterals does not exclude restenosis; instead, it enables the patient to potentially better tolerate it with an intact collateral system and a preserved distal target, should surgical intervention become necessary.

Methodical crossing using the true lumen angioplasty technique has the potential to be time intensive; however, in our experience, this factor is negligible to favorable in contrast to PIER crossing. Each attempt, on average, takes no more than 90 seconds to 2 minutes. On a difficult crossing, we may reorient the wire three to four times, but the total time for all of the maneuvers has not exceeded 30 minutes in any of our procedures. At our institution, we have attempted 60 reorientations and have been successful in 56 of the cases. Success is defined as crossing the total length of the occlusion through the true lumen for at least 90% of the crossing and sparing of the distal reference vessel. In the four failed cases, we were unable to maintain intraluminal orientation secondary to severe intraluminal calcification, but we were able to achieve conventional reentry into the distal vessel.

Hydrophilic wires are the key component to successful reorientation. The soft tip of the wire easily travels down microchannels or loops back within the vessel if no microchannels are accessible. At our institution, the Regalia XS 1.0 wire (Asahi Intecc USA, Inc., Santa Ana, CA) is used most often, but any hydrophilic 0.014-inch wire is acceptable. For microcatheters, any 0.014- or 0.018-inch–compatible catheter is acceptable; at our institution, we typically use the Quick-Cross Select support catheter (Spectranetics Corporation, Colorado Springs, CO).

A major limitation of this technique is the need for intravascular ultrasound and an interventionist who is familiar with intravascular imaging. Interest in this technique necessitates a moderate level of training to identify axial orientation and the point of deflection, the composition of the plaque, and whether the reoriented wire is adequately deflected from the subintimal tract.

It should be emphasized that by the term “luminal crossing,” we are not aiming for the wire to find a patent channel; instead, we aim to center the second wire into the middle of the plaque. In a small percentage of cases, the wire accessed a microchannel within the otherwise occluded lumen, which facilitated a more rapid crossing, but the ultimate aim of reorientation is simple deflection from the subintimal plane.

Another limitation is the presence of severe intraluminal calcium. The needle (27-gauge) of the Pioneer Plus catheter is often unable to adequately penetrate a dense border. One solution is to add 2 mm on the depth gauge in the presence of significant echodensity. Another option is to scan the length of the deflection to find plaque that is more amenable to puncture. The last option is to place the IVUS transducer at the start of a calcified segment, thereby ensuring that the needle (which is more proximal) is facing softer plaque. The only drawback to this technique is that the interventionist cannot witness the crossing and depth of the reoriented wire, because the calcium attenuates all imaging behind it. It is presumed that if the reoriented wire is not visible by IVUS, it is running behind the calcified plaque and is therefore reoriented.

There are also multiple potential benefits to this technique. Although the morbidity associated with percutaneous revascularization is low, persistent revascularization attempts with guidewires may cause perforation and dissection.12

Reorientation with use of the Pioneer Plus catheter may make these attempts safer and more predictable. Potential benefits extend beyond viability of the distal reference. With the advent of image-guided atherectomy nearly upon us, preserving the options for debulking in a safe and effective manner will become more appealing. Lastly, there are high-risk total occlusions in which a subintimal approach may be undesirable, such as vessels that are retroperitoneal. In our experience, orientation in retroperitoneal vessels has proven to be a safer alternative to conventional PIER crossings.

Haroon L. Chughtai, MD, FACC, is with the Department of Internal Medicine, Division of Cardiology, St. John Hospital and Medical Center in Detroit, Michigan. He has disclosed that he has no financial interests related to this article.

James Torey, PA-C, is with the Department of Internal Medicine, Division of Cardiology, St. John Hospital and Medical Center in Detroit, Michigan. He has disclosed that he has no financial interests related to this article.

Hiroshi Yamasaki, MD, FACC, is with the Department of Internal Medicine, Division of Cardiology, St. John Hospital and Medical Center in Detroit, Michigan. He has disclosed that he has no financial interests related to this article.

Thomas P. Davis, MD, FACC, is with the Department of Internal Medicine, Division of Cardiology, St. John Hospital and Medical Center in Detroit, Michigan. He has disclosed that he has no financial interests related to this article. Dr. Davis may be reached at (313) 343-4612; tpdavis60@aol.com.

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