Recanalization of Infrainguinal Chronic Total Occlusions With the Crosser System: Results of the PATRIOT Trial

Abstract: Purpose. To evaluate the angiographic and functional outcomes of the Crosser chronic total occlusion (CTO) recanalization system used to facilitate crossing of infrainguinal occlusions resistant to conventional guidewire techniques. Methods. Eighty-five patients with a previous or concurrent failed attempt to cross a CTO using conventional guidewire techniques were enrolled at eight United States centers. Occlusions were at least 30 days old and ≤30 cm in length. Primary endpoints included advancement of the recanalization system into or through the occlusion gaining guidewire access in the distal vessel beyond the lesion, and 30-day freedom from clinical perforation requiring treatment. Results. The average age of occlusion was 16 months, the mean occlusion length was 117.5 ± 84.0 mm, 55.7% had unfavorable morphology for crossing, and 75% were moderately to severely calcified. Superficial femoral artery (SFA) occlusions were most commonly treated (61.2%), followed by popliteal artery (20%), and tibioperoneal (16.5%) occlusions. The CTO was crossed and the guidewire successfully advanced into the distal true lumen in 83.5% of cases. Following adjunctive therapy, 81.2% achieved a satisfactory angiographic result (≤50% residual stenosis). At 30 days post procedure, 98.8% of patients were free from clinical perforation. Conclusion. Use of the Crosser CTO recanalization system facilitated crossing of guidewire-resistant, chronic, infrainguinal occlusions with minimal risk of clinically significant vessel perforation. 

J INVASIVE CARDIOL 2014;26(10):497-504

Key words: chronic total occlusion (CTO), mechanical recanalization system, infrainguinal occlusion, peripheral artery disease (PAD), critical limb ischemia

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Peripheral artery chronic total occlusions (CTOs) are commonly encountered during the evaluation and management of patients with symptomatic peripheral artery disease (PAD).^1-3 Superficial femoral artery (SFA) CTOs are present in up to 50% of patients who present with intermittent claudication.⁴ Infrapopliteal CTOs are found in the majority of patients presenting with critical limb ischemia (CLI).^5-7 CTO recanalization procedures are often technically challenging and associated with increased contrast use, increased radiation exposure for the operator and patient, and increased potential for complications. Factors that affect the likelihood of successful CTO crossing include the duration of the occlusion, lesion length and morphology, calcification, presence of collaterals (especially near the proximal cap), and distal flow.⁸ Failure to successfully cross the occluded segment with a guidewire is most often due to subintimal trapping of the wire with inability to reenter the distal true lumen. 

A variety of recanalization techniques have been employed for peripheral artery CTOs. For femoropopliteal CTOs, a deliberate subintimal technique with a looped hydrophilic guidewire is a common approach. While this technique is often successful, it can be difficult to navigate the guidewire back into the vessel lumen after crossing the CTO, especially when treating diffusely diseased or calcified vessels.^9-11 Although revascularization success rates have improved with the introduction of reentry catheters, a reliable device for crossing occlusions via an intraluminal approach has been absent. We report the results of a prospective, multicenter trial that evaluated the angiographic and functional outcomes of a recanalization system designed to aid crossing of infrainguinal occlusions.

Methods

Patient population. Between November 2006 and August 2007, eight centers in the United States enrolled 85 patients (52 men; mean age, 72 ± 10.6 years) with documented, chronically occluded infrainguinal arteries in the prospective PATRIOT (Peripheral Approach To Recanalization In Occluded Totals using the Crosser System) study. Patients were eligible for inclusion if a concurrent, conventional guidewire attempt to cross the occlusion or a previous attempt failed. Occlusions were defined as 100% blockage of the artery with no angiographically detectable antegrade blood flow; they were at least 30 days old, ≤30 cm in length, and had a reference vessel diameter ≥2.0 mm proximal to the occlusive lesion. The trial was conducted under a Food and Drug Administration (FDA)-approved clinical protocol, approved by the institutional review board or ethics committee at each study site, and conducted in accordance with Good Clinical Practice (GCP) guidelines. Patients were informed prior to treatment of the risks and benefits of participating in the study and gave written informed consent to participate. The first author (JL) and principal investigator (JJ) prepared the manuscript, and all authors reviewed the manuscript to verify accuracy and completeness.

Characteristics of the recanalization system. The Crosser CTO recanalization system (Bard Peripheral Vascular) includes an electric generator, an attached high-frequency transducer, and a single-use 0.014˝ or 0.018˝ guidewire-compatible catheter.¹² The generator is connected to a standard wall outlet, and a footswitch initiates the delivery of high-frequency current to the transducer (Figure 1). When activated, piezoelectric crystals in the transducer generate vibrational energy (frequency, 20.5 ± 0.5 kHz) through a Nitinol core wire to the titanium catheter tip resulting in a small, 20 micron (0.001˝), rapid longitudinal tip displacement (Figure 2). The mechanical impact and cavitational effects created at the recanalization catheter tip are designed to remove or reduce occlusive material from the artery, and thereby create a channel for catheter advancement through the CTO.¹² The 0.014˝ system is introduced through a 5 Fr sheath or 6 Fr guide catheter, while the 0.018˝ system uses a 6 Fr sheath or 7 Fr guide catheter.

CTO procedure. Following access (98.8% femoral; 1.2% brachial), the recanalization catheter was loaded on a standard 0.014˝ or 0.018˝ guidewire, through a sheath (or a guide catheter when additional support was needed), and advanced to the target lesion. The guidewire was withdrawn at least 1 mm into the catheter guidewire lumen prior to engaging the proximal cap of the occlusion. A continuous saline infusion was initiated through the irrigation port on the proximal end of the recanalization catheter. Intermittently, as the catheter was activated and advanced through the occlusion, the operator could stop and advance the guidewire distally to probe the occlusion. Each recanalization catheter could be activated for a total duration of 5 minutes. After 5 minutes of activation time, progress through the occlusion was assessed. If progress was being made, then another catheter could be used (up to a total of 3 catheters). If progress was not made through the lesion after 15 minutes of total activation time, the patient was managed per the operator’s standard of care. If the occlusion was successfully crossed, the recanalization catheter was removed while maintaining guidewire position for delivery of therapeutic devices such as balloons, stents, or other debulking devices (Figure 3). The decision as to which therapeutic device to use was left to the discretion of the operator. Completion angiograms were taken following the procedure, and were analyzed by an independent core laboratory (Brigham and Woman’s Hospital Angiographic Core Lab, Boston, Massachusetts).

Procedural evaluations. Clinical coordinators and investigators at each study site collected procedural data for all patients enrolled in the study. Data consisted of the recanalization system activation time, time of catheter use (defined as introduction of the recanalization catheter until the occlusion was crossed), contrast use, overall procedure time, and hospital length of stay. Since the recanalization system was intended to remove/reduce occlusive material and create a channel through the CTO for the delivery of other therapeutic devices, follow-up of 30 days was deemed appropriate to track adverse events specific to the recanalization system.

Endpoints. The primary safety endpoint was freedom from a clinical perforation requiring medical treatment from the time of the procedure through 30 days. The primary procedural efficacy measure was defined as the successful advancement of the recanalization catheter into or through a total occlusion in a native infrainguinal artery and achievement of luminal guidewire placement in the distal vessel. Both primary endpoints were verified by angiography and analyzed by the angiographic core lab. Secondary endpoints included technical success (the ability to facilitate crossing a CTO into the distal lumen with the recanalization catheter and/or a conventional guidewire), procedural success (technical success plus a residual stenosis <50% and improved angiographic flow at the end of the procedure), and clinical success (procedural success plus freedom from limb loss and repeat revascularization through 30 days).

Complications related to the index procedure and occurring within 30 days of the procedure were noted. Perforations were categorized angiographically as Type 1-4 (wire exit to extravasation) as well as clinically (requiring treatment). Angiographic perforation types were defined as follows by the core lab:^13,14 Type 1 was a “wire exit” perforation with extraluminal position of the wire and no evidence of extraluminal contrast; Type 2 was a “blush” perforation with radioopacification of dye outside the vessel that was faint and as dense as the surrounding tissue; Type 3 was a “staining” perforation with radioopacification of dye that persisted outside of the vessel and was denser than the background tissue; and Type 4 was an “extravasation” perforation with free flow of contrast into the extravascular space. Angiographic perforations were assessed by both the individual operator and the angiographic core lab. Severity was determined by the core lab unless documentation on cine was not available; then, the operator’s determination took precedence. All clinical events including perforation, hemorrhage, and blood transfusion were reviewed and categorized by an independent Clinical Events Committee (CEC), and adverse event rates were reviewed and specific events were adjudicated by a Data Safety Monitoring Board (DSMB).

Statistical methods. All data were analyzed on an intention-to-treat basis. Descriptive categorical data were expressed as rates or proportions, and continuous variables were presented as mean ± standard deviation. Binary variables were compared using chi-square or Fisher’s exact test, as appropriate, and continuous variables were compared using the Student t-test. The primary efficacy endpoint was presented as the number and percentage of patients who met the definition described above. An exact, one-sided, 95% confidence interval (CI) of the percentage was used. Analyses of the secondary endpoints consisted of the proportion of subjects experiencing each outcome, and calculation of exact, two-sided, 95% CIs around the proportion. A stepwise logistic regression was used to determine any variables associated with technical success or failure. All analyses were performed using SAS version 8.0. A two-sided P-value ≤.05 was considered significant.

Results

Patient demographics and occlusion characteristics. Patients at baseline exhibited characteristics typical of PAD (Table 1). The majority were male (61.2%), mean age was 73 years, 49.4% were diabetic, 81.2% had a history of hyperlipidemia, 87.1% were hypertensive, and 54.1% had a history of smoking. Most patients (42.4%) were classified as severe claudicants (Rutherford category 3); 18.9% had ulcers or tissue loss (Rutherford category 5 or 6). In addition to physical examination, patient symptoms were also assessed using ankle-brachial index (ABI) measures and with a quality-of-life questionnaire (Peripheral Artery Questionnaire; PAQ). At baseline, of the patients in which ABI values could be obtained (30.6% of patients had non-compressible arteries), 40 patients (67.8%) had an ABI of <0.7. Baseline PAQ was collected on 82 of 85 patients (96.5%). 

Occlusion characteristics are summarized in Table 2. The presence and chronic nature of vessel occlusion was determined by date of symptom onset, prior bypass surgery of the target vessel, non-invasive study, or invasive imaging. The average period of vessel occlusion was 16.0 ± 23.0 months (maximum, 142 months). The mean length of occlusion determined by the core lab was 117.5 ± 84.0 mm (investigator reported, 129.6 ± 78.7 mm); 55.7% had unfavorable morphology for crossing (blunt or eccentric proximal cap) and 54.8% were severely calcified. The superficial femoral artery was the most commonly treated vessel (61.2%), with 20% of the treated occlusions in the popliteal artery, and 16.5% in the distal run-off vessels (eg, in the tibioperoneal trunk, anterior tibial, posterior tibial, and peroneal arteries). A prior procedure with a conventional guidewire was documented in 21.2% of patients. In those cases, guidewire attempts to cross the CTO resulted in an average use of 39.1 minutes of fluoroscopy time. The remaining patients had failed crossing attempts at the time of the index procedure, resulting in an average fluoroscopy time of 3.8 minutes. 

The primary safety endpoint, freedom from clinical perforation at 30 days, was achieved in 84 of 85 patients (98.8%)(Table 3). There was 1 clinically-significant perforation that was adjudicated by the DSMB as not associated with the use of the recanalization system. Primary clinical efficacy was achieved in 71 of 85 cases (83.5%), defined as the advancement of the recanalization catheter into or through a total occlusion and achievement of successful guidewire passage into the distal true lumen of the target artery. Following crossing of the CTO, the operator reported that the vessel was treated with a satisfactory angiographic result (<50% residual stenosis) in 69 of 85 patients (site reported procedural success rate, 81.2%). The core lab reported a 75.3% assessed procedural success rate after assessing films. Angiographic (non-clinically significant) perforation (Types 1-4) occurred in 14 of 85 cases (16.4%); 5 cases (5.9%) were determined by the core lab to be related to the recanalization catheter and the rest related to therapy post catheter use. We also performed a multivariate analysis to identify the angiographic and demographic variables that were determinants of success or failure. Age of occlusion was associated with a slightly lower success rate, but length of occlusion or location of occlusion were not found to be determinants of success.

Procedure duration and intervention. The average total procedure time in the PATRIOT study was 102 minutes for both technically successful and unsuccessful cases, with an average of 36.2 minutes of fluoroscopy time (Table 4). A mean of 1.2 Crosser catheters were used per case, and were activated for an average of 2 minutes and 6 seconds per procedure. The total clock time associated with Crosser catheter use, defined as the time from introduction of the catheter until the occlusion was crossed, averaged 14.3 ± 12.2 minutes. Length of hospital stay following intervention averaged 1.6 days. Excluding patients requiring surgical procedures following failed crossing attempts, the mean length of stay in the hospital was 0.8 days. Postprocedure complications included access-site hematoma in 5 patients (5.9%) and contrast reaction in 3 patients (3.5%).

After successful crossing of the CTO, a variety of therapies were used (Table 4); 4.7% were treated with angioplasty only and 51.8% were treated with Nitinol self-expanding stents. Laser atherectomy, directional atherectomy, and cryoplasty were also performed alone or in conjunction with stent placement above the knee. Only 1 stent was used below the knee for a flow-limiting dissection. 

Follow-up. Patients were followed after the procedure through 30 days, when an office evaluation reassessed symptoms, calculated ABI, and recorded any rehospitalizations following the index procedure. At 30-day follow-up exam, 49.2% of cases had an ABI of ≥0.9, and 62.7% of cases had an increase in ABI of >0.10. PAQ scores improved significantly from baseline to 30 days (32.0 ± 30.4 points in the technically successful group). Complications through the 30-day follow-up in all unsuccessful index procedures (14 patients) included 2 cases (14.2%) with below-the-knee (BTK) amputations and 1 case (7.2%) with surgical revascularization. Both amputations occurred in critical limb ischemia patients (Rutherford class 5). In the successful cases (total, 71 cases), only 1 case (1.4%) required repeat PTA for a popliteal artery restenosis. No other significant events were noted (Table 5).

Discussion

Treatment of patients with infrainguinal chronic total occlusions is challenging, with a significantly lower rate of procedural success than for the treatment of stenotic lesions.^1,8,15 In the current study, we demonstrated that the Crosser CTO recanalization system facilitated recanalization of guidewire-resistant, chronic, infrainguinal arterial occlusions in 83.5% of cases. This favorable outcome was achieved despite the inclusion of very long occlusions (mean occlusion length, 117.5 ± 84.0 mm) with a high prevalence of moderate to severe calcification (75% of cases). The device was found to be safe, with 98.8% of patients free from clinically significant perforation at 30 days. 

These finding are consistent with previous single-center experiences that demonstrated 75%-77% effectiveness in aiding guidewire crossing of peripheral vascular chronic occlusions, with an average crossing time of <5 minutes using the Crosser CTO recanalization system.^16,17 In addition, in a prospective, multicenter trial, Tiroch and colleagues demonstrated the safety and effectiveness of the recanalization system in aiding guidewire crossing in coronary artery occlusions (60.8%).¹⁸ 

Despite the inclusion of long, calcified occlusions, there was a low risk of complications associated with the use of this device. In a single case, clinically significant perforation occurred following delivery of the guidewire and subsequent multiple passes with a directional atherectomy catheter distal to the successfully crossed SFA occlusion. Prolonged balloon inflation was performed to seal the perforation with a good angiographic result. Although 49.5% of patients presented with critical limb ischemia (Rutherford class 4-6) only 2 patients required major amputation after the crossing procedure failed. 

There is no consensus regarding the optimal approach to infrainguinal CTOs. In many centers, a deliberate subintimal approach with a looped guidewire is the preferred strategy.^9,10 While satisfactory results can be achieved by skilled operators with a subintimal approach, success rates tend to drop when the lesion is significantly calcified or there is diffuse disease in the distal target vessel.¹¹ Difficulty reentering the true lumen distally may propagate dissection and extend the length of segment that needs to be treated, possibly limiting options for future surgical revascularization. The use of reentry devices has increased the likelihood of a more controlled and precise reentry into the lumen, with less risk of damage to the distal target vessel lumen, after subintimal guidewire passage.^19-23 Alternative access techniques, such as a retrograde popliteal or pedal approach, can also be attempted for occlusions with unfavorable anatomy.^24-29 These techniques, however, require a high degree of operator experience and can increase procedure time, expose the patient and operator to high levels of radiation, and increase the patient’s overall dose of contrast. 

Study limitations. This study was limited by its modest sample size, non-randomized design with no concurrent control, and short-term follow-up. No definitive conclusions can be drawn regarding the safety or effectiveness of the recanalization system compared to other commercially available devices. The study met its procedural endpoints, but follow-up angiography and intravascular ultrasound were not performed to confirm central lumen crossing with the recanalization catheter. There are theoretical and practical advantages to remaining in the vessel lumen during guidewire and catheter passage through a total occlusion. Central lumen crossing of a CTO allows the use of adjunctive therapies with less risk of perforation and dissection in the distal target vessel than with subintimal crossing techniques. Subintimal recanalization may also lead to loss of important collateral vessels within or just beyond the CTO. 

Conclusion 

In the current study, we demonstrated that the Crosser CTO recanalization system was safe and effective for crossing guidewire-resistant femoropopliteal and infrapopliteal occlusions. Vibrational energy delivered to the tip of the recanalization catheter facilitated penetration of the cap of the CTO as well as removal or reduction of occlusive material so that the catheter and/or guidewire could pass through the remainder of the occlusion. Additional study is required to further define the role of this promising CTO technology for the treatment of patients with complex peripheral arterial occlusive disease.  

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From the ¹UC Davis Medical Center, Sacramento, California; ²El Camino Hospital, Mountain View, California; ³Providence St. Vencent’s Hospital, Portland, Oregon; 

⁴Swedish Medical Center, Seattle, Washington; ⁵St. Joseph’s Hospital, Syracuse, New York; ⁶Methodist Hospital, Houston, Texas; ⁷Christ Hospital, Cincinnati, Ohio; and ⁸Presbyterian Hospital, Dallas, Texas.

Funding: The study was sponsored by Bard Peripheral Vascular, Tempe, Arizona.

Disclosure: The authors have completed and returned the ICMJE Form for Disclosure of Potential Conflicts of Interest. Dr Laird reports consultant fees for Bard Peripheral Vascular; consultant/advisory board member for Abbott Vascular, Boston Scientific, Covidien, and Medtronic; and research support from WL Gore. The remaining authors report no conflicts of interest.

Manuscript submitted June 27, 2014, provisional acceptance given July 17, 2014, final version accepted August 7, 2014.

Address for correspondence: John R. Laird, MD, FACC, FACP, FSCAI, UC Davis Medical Center, UC Davis Vascular Center, 4860 Y St, Suite 3400, Sacramento, CA 95817. Email: john.laird@ucdmc.ucdavis.edu