Infrainguinal CTO Recanalization Assessed by Intravascular Ultrasound: Results of the CENTRAL Study

Abstract: Objectives. CENTRAL was a prospective, multicenter, 100 patient study designed to evaluate the ability of a recanalization catheter system to cross chronic total occlusions (CTOs) of the superficial femoral artery while staying within the central vessel lumen. Methods. The primary endpoint was the successful crossing of a CTO (≥90% of the length) with the recanalization catheter in the central lumen of the superficial femoral artery in at least one-half of the studied patient population, confirmed by intravascular ultrasound. Secondary endpoints included standardized anatomic damage assessment (the TAPE method) and an assessment of the relationship between the percent of CTO crossing and TAPE scores to the rate of target-lesion revascularization (TLR) at 30 days and 6 months. Results. The mean age of the occlusions was 16.6 ± 22.28 months (range, 1-120 months), the average occlusion length reported by the sites was 132.1 ± 87.69 mm (range, 4-300 mm), and a majority of lesions were moderately (42.0%) or severely (32.0%) calcified. In 43/85 (50.6%) of the evaluable intravascular ultrasound images, the recanalization catheter successfully navigated the central lumen of the CTO (ie, ≥90% luminal crossing) with >50% luminal crossing in 64/85 (75.3%) of cases. The 6-month TLR rate was significantly lower in patients where the CTO was crossed ≥90% in the central vessel lumen (4.7%) compared with crossings <90% (20.6%; P=.04). The 6-month TLR rate was 3.5% in patients with a favorable TAPE score of 0-4 and 36.8% with an unfavorable TAPE score of 5-8 (P<.001). Conclusion. Use of a recanalization catheter in complex superficial femoral artery CTO crossings achieved intraluminal crossings in >50% of cases and decreased anatomic damage, which appeared to offer a significant advantage in 6-month TLR rates. 

J INVASIVE CARDIOL 2016;28(11):430-439. Epub 2016 October 15.

Key words: peripheral vascular disease, PVD, critical limb ischemia, CLI, intravascular ultrasound, IVUS

Critical limb ischemia (CLI) is associated with high rates of limb loss due to amputation; 25% of all diagnosed patients require major amputations within 6 months of presentation (250,000 patients per year in the United States and Europe alone), with mortality rates exceeding 25% at 1 year and greater than 50% at 5 years from the time of diagnosis.^1-3 CLI often presents as the result of a chronic total occlusion (CTO); the presence of a CTO can lead to lower revascularization rates.^4-6

Endovascular methods offer a less invasive approach for CLI patients while providing favorable morbidity and mortality rates; surgical alternatives may be too risky in patients with significant comorbidities.^7-9 Subintimal angioplasty (SA), also known as the percutaneous intentional extraluminal recanalization (PIER) approach, was first described by Bolia et al¹⁰ and is a favored minimally invasive approach to address infrainguinal CTOs. PIER, however, has a failure rate of 10%-20%, primarily due to the inability to access the distal vessel from the subintimal tract.¹¹ An additional limitation of PIER is the dependence on operator experience, with perforations reported in up to 9.5% of PIER attempts.¹²

While PIER crossing rates have improved with the advent of reentry catheters, true-lumen crossing catheters offer an alternative to PIER crossings by facilitating the crossing of CTOs purely through the former lumen of the occluded vessel. Multiple studies have demonstrated an initial success rate similar to PIER, with a substantially reduced risk of perforation or complications associated with PIER.^13,14 However, the lack of uniform performance criteria for true-lumen crossing devices means there is no proof that the crossing did not simply traverse the subintimal tract in a similar fashion to a PIER crossing. There is also no proof that a “clean” true-lumen crossing offers benefit in reducing target-lesion revascularization (TLR) rates compared with a PIER approach, which can be performed with less expensive catheters and less capital investment. 

This study was conducted as a prospective registry designed to evaluate the ability of a true-lumen recanalization system to successfully cross chronic superficial femoral artery (SFA) total occlusions in the central lumen of the artery with confirmation by intravascular ultrasound (IVUS). A secondary goal was to compare 1-month and 6-month TLR rates to determine if true-lumen crossings reduced reintervention rates compared with crossings featuring less favorable anatomic sequelae.

Methods

Patient population. Between February 2010 and July 2012, eight centers in the United States enrolled 100 patients with documented, chronically occluded infrainguinal arteries in the prospective CENTRAL (Crosser ENters The Right Arterial Lumen) study. Patients with a totally occluded SFA (100% narrowing of the artery with no angiographically detectable antegrade blood flow) were eligible for inclusion if the operator assessed that the lesion was at least 30 days old, the lesion was ≤30 cm in length, the vessel was ≥3.0 mm in diameter, and the patient was considered an acceptable candidate for percutaneous transluminal angioplasty (PTA), peripheral artery bypass surgery, or peripheral artery stent implantation. 

The trial was sponsored by Bard Peripheral Vascular, and was conducted under a protocol approved by the institutional review board or ethics committee at each study site. All procedures were conducted in accordance with the guidelines of good clinical practice, the Health Insurance Portability and Accountability Act, and applicable state and federal regulations. 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 (JT) and principal investigator (TD) prepared the manuscript, and all authors reviewed the manuscript to verify accuracy and completeness. The CENTRAL trial was registered prior to the start of patient enrollment at www.clinicaltrials.gov (NCT01205386).

Characteristics of the recanalization system. The CROSSER CTO recanalization system (Bard Peripheral Vascular) was described in detail in previous publications and is summarized here.^12,14 The system consisted of a reusable electronic generator, foot switch, high-frequency transducer, and a single-use 0.014˝ or 0.018˝ guidewire compatible catheter. The catheter was attached to the transducer hand-piece; when activated, vibrational energy was transmitted to the tip of the catheter creating a mechanical impact and cavitation that aided in breaking down occlusive material in the artery and in tunneling through the CTO. 

Patient demographics. Demographic and medical risk factors are reported in Table 1. Sixty-four out of 100 patients (64.0%) were male, with a mean age of 70.3 ± 9.97 years (range, 48.9-90.1 years). The majority of patients had medical histories significant for hyperlipidemia (92.0%) and hypertension (84.0%) requiring treatment, cigarette smoking (74.0%), coronary artery disease (55.0%), and diabetes (55.0%). Forty-four patients (44.0%) were classified with symptoms of ischemic rest pain or critical limb ischemia (CLI) with tissue loss (Rutherford category 4-6), 37.0% suffered from severe, lifestyle-limiting claudication (Rutherford category 3), and the remaining 19 patients (19.0%) were classified as Rutherford 0-2. Of the 89 patients where baseline ankle-brachial index (ABI) was evaluable, 75 patients (84.3%) had moderate to severe peripheral vascular disease (PVD), indicated by an ABI of <0.7. 

CTO procedure. Following access (100% femoral), the recanalization catheter was delivered through a standard guide catheter over a guidewire to the occlusion site (61.0% antegrade and 28.0% retrograde). Once in position, the operator retracted the guidewire into the catheter lumen at least 1 mm from the catheter tip and activated the system by stepping on the foot switch. Each recanalization catheter could be activated for a total of 5 minutes, at which point it could be replaced with another catheter if progress was being made. If the CTO was not crossed after three catheters were used, or 15 minutes of generator activation time (measured by a counter on the control panel), the patient was managed per the operator’s standard of care. As the recanalization catheter progressed through the lesion, the operator could stop the generator at any time and advance the guidewire distally to probe the occlusion. Once a wire reached the central lumen distal to the lesion, the catheter was removed, leaving the guidewire in place for delivery of an IVUS catheter to assess the crossing. After IVUS evaluation, subsequent therapies were used to treat the lesion at the operator’s discretion.

Procedural evaluations. Clinical coordinators and investigators at each study site collected procedural data for all patients enrolled in the study on protocol-approved case report forms. Data consisted of the activation time, time of catheter use, contrast use, procedure time, and hospital length of stay. The study was monitored by Clinical Consulting (San Diego, CA) and the sponsor. IVUS studies following successful crossing were performed at the study sites, and images were submitted to the Fontbonne Auxillary IVUS Core Laboratory (Detroit, MI) for review and analysis. Initially, follow-up of 30 days was considered sufficient to capture adverse events associated with the procedure. Follow-up was later increased to 6 months (protocol amendment) to permit the collection of additional follow-up data.

Endpoints. The primary endpoint was defined as successful navigation of the recanalization catheter through the CTO and into the central lumen of the artery as confirmed by the core lab’s assessment of the IVUS images taken after recanalization. The primary endpoint was graded by the percentage of the central lumen crossed, and categorized into four tiers: tier 1 was ≥90%; tier 2 was 75%-89%; tier 3 was 50%-74%; and tier 4 was <50% of the total crossing within the central lumen. Patients with missing primary endpoint data were excluded from this proportional-based analysis. Secondary endpoints included technical success (the ability to cross the CTO in the central vessel lumen with the recanalization catheter and/or any conventional guidewire after use of the catheter); procedural success (technical success plus a residual stenosis <50% with improved flow verified angiographically at the end of the procedure); and clinical success (freedom from limb loss and repeat revascularization from index hospitalization through 6 months). Technical success was determined by IVUS imaging following CTO crossing; the IVUS core lab analyzed technical and procedural success as a proportion of the evaluable IVUS images. Patients with missing data were excluded from the analyses. Each endpoint was calculated as a proportion of patients experiencing each outcome with the exact two-sided 95% confidence intervals (CIs) around the proportion. Adverse events were collected at the time of the index procedure, between the procedure and discharge, and at follow-up out to 6 months. 

IVUS analysis. IVUS analysis consisted of reviewing all evaluable images of CTO crossings submitted by the study sites to the independent IVUS core lab (Figure 1). Nineteen of the IVUS studies were conducted using the Atlantis 0.014˝ catheter (Boston Scientific) and 67 using the Eagle Eye Gold 0.014˝ catheter (Philips Volcano). 

IVUS analysis was two pronged. First, the percentage of luminal crossing was determined by two experienced IVUS readers from two separate readings. Investigators were encouraged to perform IVUS catheter pullback through the total occlusion at a steady rate to provide the best opportunity to calculate the overall percentage of central lumen crossing. The two readers reviewed all discrepancies and submitted a consensus measurement. 

A second analysis of the crossings was performed by both core lab readers using the TAPE anatomic damage scale (tears, axial orientation, collateral preservation, reference segment extension).¹⁵ All four criteria were graded on a scale of 0-2 for a potential overall score of 0-8 (Table 2). Evidence of dissection was examined and tears were categorized by location – proximal to the CTO cap, within the lesion, and distal to the CTO (≤5 cm from the distal end of the lesion). No evidence of dissection resulted in a score of “T0” while any evidence of dissection resulted in a score of “T1” (Figure 2). Evidence of extravascular or intramural hematoma received a score of “T2” (Figure 3). Axial orientation was based on the position of the IVUS catheter within or outside of the border of the internal elastic lamina (IEL) throughout the crossing (Figure 4). If the IVUS catheter remained within the border of the IEL, then the crossing was considered in the central lumen and was given a score of “A0”; if the IVUS catheter deflected between the IEL and the external elastic lamina (EEL), it was given a score of “A1”; and if the IVUS catheter deflected outside of the EEL, it was deemed an adventitial or periadventitial deflection and given a score of “A2.” Collateral preservation was based on the collateral circulation proximal to, within, and distal to the total occlusion (Figure 5).¹⁶ No loss of collateral circulation yielded a score of “P0”; if a collateral vessel connected with an alternate lumen within the treatment segment alone, the result was a score of “P1”; and a collateral vessel connected to an alternate lumen in a reference segment was scored as “P2.” Finally, the core lab assessed the distal and proximal reference segments for extension of the treatment segment during the crossing attempt (Figure 6). If there was immediate entrance and exit of the catheter and guidewire from the total occlusion, the patient was given a score of “E0”; if either reference segment showed evidence of extension, the patient was given a score of “E1”; and if both reference segments showed evidence of extension, it was given a score of “E2.” The total TAPE score was computed by adding each component with the score listed after the respective component letter. For instance, a pristine crossing had a score of 0 (T0A0P0E0 = 0). A patient with a hematoma, deflection outside of the IEL, distal reference extension, and loss of a reference collateral had a total TAPE score of 6 (T2A1P2E1 = 6). In Figure 5, examples C and D both showed orientation outside of the IEL (A1), reference segment extension (E1), and reference collateral loss (P2), resulting in a TAPE score of 4. As with the first analysis of crossing success, TAPE score discrepancies were resolved between the two readers and a consensus measurement was submitted.

Finally, in addition to the two protocol-specified IVUS analyses, an additional post hoc analysis was completed by the core lab comparing the crossing results and TAPE scores to 1-month and 6-month TLR rates to determine whether performing central crossings offered advantages over incomplete luminal crossings, and whether favorable TAPE scores offered advantages over unfavorable TAPE scores. 

Statistical methods. The intention-to-treat (ITT) population was defined as all patients who met the protocol eligibility criteria (based on clinician determination) in which the operator attempted to use the recanalization catheter to cross a CTO. Descriptive categorical data were expressed as rates or proportions, and continuous variables were presented as means ± standard deviations. Binary variables were compared using chi-square or Fisher’s exact test, as appropriate, and continuous variables were compared using the Student’s 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% CI of the percentage was used. Analyses of the secondary endpoints consisted of the proportion of patients 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

Occlusion characteristics and procedural data. Angiographic occlusion characteristics reported by the sites are summarized in Table 3. The mean occlusion age was 16.6 ± 22.28 months (range, 1-120 months), mean occlusion length was 132.1 ± 87.69 mm (range, 4-300 mm), and the majority of patients had moderately (42.0%) or severely (32.0%) calcified lesions. Seventeen percent of patients underwent prior percutaneous treatment at the site of the target occlusion, and 10 patients reported a previous attempt(s) to cross the target occlusion. Procedural data are summarized in Table 4. A total of 121 Crosser catheters were used in the study, with a mean of 1.2 catheters per patient (range, 1-3 catheters). The mean time between the introduction of the recanalization catheter into the patient and subsequent removal was 14.0 ± 15.6 minutes, with a mean time of recanalization system activation of 3.0 ± 2.6 minutes. 

A variety of subsequent therapies were performed after successful crossing of the CTO: 4 patients received PTA only (4%), 72 patients (72.0%) underwent atherectomy, and 34 patients (34.0%) received stents (mean total stent length, 196.8 ± 89.2 mm). The mean total procedure time was 95.7 ± 48.37 minutes (range, 21-425 minutes; median, 92.5 minutes). The longest procedure time (425 minutes) appeared to be an outlier in the dataset. When it was excluded from the analysis, mean total procedure time decreased to 92.4 ± 35.3 minutes (range, 21-220 minutes). The mean total fluoroscopy time reported was 35.3 ± 18.03 minutes (range, 10-120 minutes).

IVUS findings. IVUS images from 86 patients were sent to the IVUS core lab for postprocedure evaluation, 85 of which could be evaluated to assess the primary endpoint (≥90% central crossing of the CTO). Slightly more than one-half of the evaluable cases (43/85; 50.6%) showed successful navigation (≥90%) of the CTO within the central lumen and 64/85 patients (75.3%) had a >50% central lumen crossing (Table 5). All 86 images submitted to the core lab could be evaluated for secondary endpoint data. Technical success was achieved in 78/86 patients (90.7%), meaning the CTO was crossed with the Crosser catheter and/or any conventional guidewire into the central lumen of the distal artery and was confirmed by IVUS examination. All but 2 patients (76/86) who achieved technical success also achieved procedural success (88.7%), demonstrating a residual stenosis of <50% and improved flow verified angiographically at the conclusion of the procedure. TAPE scores were measured for the 77 IVUS loops where the CTO was crossed (Table 6). Twenty-eight patients had a TAPE score of 0, while 58 patients had a TAPE score of ≤4. 

Follow-up. At 30 days and 6 months, patients were evaluated to reassess symptoms, calculate ABI (30 days only), and record any rehospitalizations following the index procedure. At baseline, 37% of patients had symptoms of severe lifestyle limiting claudication (Rutherford 3) and 44% suffered from critical limb ischemia (Rutherford 4-6). By 30-day follow-up, 38% of patients were classified as asymptomatic (Rutherford 0) and 17% had mild claudication (Rutherford 1). At 6-month follow-up, 66.7% of patients were classified as Rutherford 1 or less.

 ABI data were recorded at baseline and at 30-day follow-up for both target and non-target limbs. At baseline, 75/89 patients (84.3%) who received ABI exams were classified with moderate or severe PVD (ABI <0.70 in the target limb) while only 3/89 patients (3.4%) had a normal ABI. At 30-day follow-up, most patients (53/86; 61.6%) had ABI measurements that were ≥0.7 (normal or mild PVD). 

Clinical success was based on site-reported data and included evaluations of all 100 patients. Clinical success, defined as freedom from limb loss and repeat revascularization (bypass surgery or PTA) from index hospitalization through 30 days, occurred in 90/100 (90.0%), while the cumulative clinical success rate at 6 months was 53.0%. The clinical success rate was driven by repeat revascularization somewhere in the target limb, not limb loss. At 6 months, only 1 patient with CLI experienced limb loss (a below-the-knee amputation followed by a subsequent above-the-knee amputation). Although the amputations occurred in the same limb as the target CTO, the events did not involve the study lesion or vessel and were not considered related to the index procedure. Additional toe amputations were reported in 2 patients, but were not considered limb loss in the calculation of clinical success. 

The overall TLR rate was 1.3% (1/77) at 30 days and 11.7% (9/77) at 6 months. Of the 43 patients where the CTO was successfully crossed (≥90%) in the central lumen, the 6-month TLR rate was 4.7%. However, in the group where the CTO was crossed <50% in the central vessel central lumen, the 6-month TLR rate was 23.1%. When comparing the ≥90% crossing group with all crossings <90%, the 6-month TLR rates were 4.7% and 20.6%, respectively (P=.04). The TLR rate at 6 months for the group with a TAPE score of ≤4 was 3.5%, vs 36.8% for the group with a TAPE score of ≥5 (P<.001). Individual assessment of each parameter in TAPE is examined in Table 7. The presence of hematoma (T2), showed the greatest overall risk for TLR at 36.8%, vs a T0 with a TLR rate of 4.4%. Extension of both references (E2) showed the second largest impact, with a 6-month TLR rate of 33.3%, vs a 5.9% TLR rate for the group with an E0 score. Of note, collateral preservation demonstrated the smallest difference in TLR rates, but 6-month TLR rates were still increased roughly four-fold in the P1/2 vs P0 groups.

Adverse events. Adverse events are summarized in Table 8. The most frequently reported prespecified events occurring at the time of the procedure were perforations (5/100; 5.0%), while the most common postprocedure/discharge event was prolonged hospitalization (5/100; 5.0%). Repeat hospitalizations and percutaneous revascularization of the target limb were the most frequently reported pre-populated adverse events occurring in the post-discharge follow-up period. Two patient deaths were reported during the course of this study. Neither death was reported as related to the study procedure or device. 

Angiographic perforations were assessed by the individual operator. Two of 5 perforations were reported as type 2, with blush of contrast; 1 patient with a type 2 perforation was treated with balloon tamponade, while the other received a repeat angiogram but the contrast blush resolved without additional intervention. One patient had a clinically-significant perforation classified as type IV (dye extravasation) that required 1 unit of blood. The event was identified post procedure on a repeat angiogram after the patient reported severe leg pain, and was classified by the operator as related to the CTO and the device. Data were not reported for the other 2 perforations. 

Discussion

CTOs represent the most extreme manifestation of PVD and are major contributors to subsequent CLI. Endovascular approaches to treat CTOs offer advantages of shorter hospital stays, reduced short-term costs, lower major adverse event rates, and long-term limb salvage rates.^17,18 Endovascular approaches to crossing CTOs encompass multiple strategies, including intentional subintimal crossing and subsequent angioplasty (SA or PIER approach), use of wires and reentry devices, and transluminal crossings with ancillary recanalization catheters (ie, the Crosser catheter). The practice of intentionally crossing a CTO by working a wire subintimally has been associated with high restenosis rates,^8,14,19-21 poor long-term patency rates,¹⁷ and an overall complication rate ranging between 6%-17%.^22-26 

Whether transluminal crossings with recanalization catheters actually traverse the CTO in an intraluminal path rather than simply following the identical path of an SA/PIER approach has remained unclear. There has also been a lack of evidence as to whether a “cleaner” crossing with a recanalization catheter benefits long-term patency rates compared with a SA/PIER crossing. This is important because of the level of technical expertise and/or financial constraints these new devices demand. 

Results of the current study demonstrated that the Crosser CTO recanalization catheter was successful in crossing complex SFA-CTOs in lesions that were similar in terms of mean age of occlusion, length of occlusion, and calcification to previous single and multicenter studies.^14,27,28 Eighty-six patients (86.0%) enrolled had endpoint data that could be evaluated by the core lab (the other 14 lesions were not crossed).Technical success was achieved in 78/86 patients; that is, the CTO was crossed with the recanalization catheter and/or a conventional guidewire into the central lumen of the distal artery. In addition, 88.4% of patients also achieved procedural success demonstrating a residual stenosis of <50% and improved flow verified angiographically at the conclusion of the procedure. 

In 43/85 evaluable cases (50.6%), the CTO was crossed ≥90% within the central lumen and in 64/85 (75.3%), the lesion was crossed >50% in the central lumen. The impact of a pristine crossing was impressive when comparing 6-month TLR rates; patients with ≥90% axial crossing had a significantly lower TLR rate (4.7%) than patients where the lesion was crossed within the lumen <90% (20.6%; P=.04). Equally impressive was the impact of anatomic sequelae during crossing, as reflected by the TAPE score. The 6-month TLR rate was 3.5% for a favorable TAPE score of 0-4 and 36.8% for an unfavorable TAPE score of 5-8 (P<.001). Improvements in baseline ABI and Rutherford class at 6 months for the entire study were also noted.

A recent study has shown that routine IVUS use in lower-extremity peripheral intervention independently predicted reduced postprocedural complications (P=.04), amputation rates (P<.001), and renal complications (P=.01), with non-significant impact on hospitalization costs.²⁹ The use of IVUS was valuable in this study because it accurately assessed not only the axial orientation of the crossing but also the major anatomic sequelae commonly associated with CTO crossings and the extent of calcification within the diseased segment. Collateral preservation, especially collaterals feeding the distal reconstituted segment, is an important but challenging parameter to assess angiographically.^30,31 In contrast, IVUS can reliably identify collateral loss, hematoma formation, and subintimal propagation beyond the distal cap, which can limit future surgical options. ^16,32

Study limitations. This study was limited by its modest sample size, non-randomized design with no concurrent control, and short-term follow-up to 6 months. However, the 6-month TLR rate of 4.7% (freedom from TLR = 95.3%) in patients where the CTO was crossed >90% in the CENTRAL trial compared favorably with 6-month TLR rates in the prospective, randomized RESILIENT and DEBELLUM trials.^33,34 In the RESILIENT trial of bare-metal stent implantation vs PTA, the stent intention-to-treat group had a freedom from TLR rate of 98.5% at 6 months. Additionally, in the DEBELLUM trial of drug-coated balloon vs conventional angioplasty, 6-month TLR rate was 6.1% in the drug-coated balloon group. Furthermore, the average lesion length (132 mm) of the CENTRAL trial was roughly double the length of RESILIENT or DEBELLUM lesions. Lastly, when compared with other crossing devices and techniques such as the TruePath device, the Crosser TLR rate of 4.7% was less than the reported 6-month TLR rate of 8.0% in the XLPAD registry.³⁵ No definitive conclusions can be drawn regarding the safety or effectiveness of the Crosser device in comparison with other commercially available devices. 

Conclusion

Use of the Crosser recanalization catheter in complex SFA-CTO crossings demonstrated that the device achieved IVUS-confirmed intraluminal crossings and decreased anatomic damage, which appeared to offer a significant advantage in 6-month TLR rates. Extrapolating intraluminal crossing percentages and TAPE scores with long-term clinical outcomes has the potential to highlight the safest and most effective CTO interventional strategies in future studies.

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From ¹St. John Hospital and Medical Center, Detroit, Michigan; ²Ohio Heart Health Center, Cincinnati, Ohio; and ³Metro Health Hospital, Wyoming, Michigan.

Funding: This study was funded by Bard Peripheral Vascular. 

Disclosure: The authors have completed and returned the ICMJE Form for Disclosure of Potential Conflicts of Interest. Dr Torey reports institutional compensation for Core Lab analysis and personal compensation for manuscript formation from Bard; consultant and educator fees from Philips Volcano. Dr Lalonde reports grant funds for performing core lab work from Bard Vascular. Dr Davis reports training programs for Bard Vascular and Spectranetics; training programs and advisory panel for Avinger, Medtronic, and Volcano; training programs, live case presentations, and speaking fees from CSI. Dr Mustapha reports consultant fees for Bard Vascular and Philips Volcano. The remaining authors report no conflicts of interest regarding the content herein.

Manuscript submitted February 29, 2016, provisional acceptance given May 3, 2016, final version accepted July 25, 2016.

Address for correspondence: James Torey, PA-C, St. John Hospital and Medical Center, 22101 Moross Road, Detroit, MI 48236. Email: toreyj01@yahoo.com