Long-Term Outcomes With Use of the CrossBoss and Stingray Coronary CTO Crossing and Re-Entry Devices

Abstract: Background. The Boston Scientific CrossBoss and Stingray Coronary CTO Crossing and Re-Entry devices (formerly the BridgePoint Medical System) can improve success rates in chronic total occlusion (CTO) percutaneous coronary intervention (PCI), but there are no published data on long-term clinical outcomes. Methods. The acute and long-term outcomes of 170 consecutive patients who underwent CTO PCI at our institution were reviewed, including 60 patients in whom the CrossBoss and Stingray devices were used and 110 patients treated with other crossing strategies. Results. Baseline characteristics were similar between the two cohorts. Patients in whom the CrossBoss/Stingray was utilized had more prior CTO PCI attempts (13.1% vs 1.6%; P=.003), required longer fluoroscopy times (46 ± 22 minutes vs 35 ± 20 minutes; P<.001), higher contrast dose (390 ± 141 mL vs 323 ± 132 mL; P>.99), and more guidewires for lesion crossing (8.0 ± 6.5 vs 4.7 ± 2.3; P<.001), but procedural success (75.8% vs 76.2%; P>.99) and major complication rates (4.8% vs 3.2%; P=.69) were similar. During a median follow-up of 1.81 years, the CrossBoss/Stingray group had no difference in target lesion revascularization (40.9% vs 29.6%; P=.13) and major adverse clinical events (40.3% vs 35.2%; P=.42). Conclusions. Use of the CrossBoss/Stingray devices for CTO PCI is associated with equally high success and equally low complication rates as other techniques, both immediately post procedure and during long-term follow-up, in spite of its use in higher complexity cases.

J INVASIVE CARDIOL 2013;25(11):579-585

Key words: coronary chronic total occlusion, percutaneous coronary intervention, outcomes

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Coronary artery chronic total occlusion (CTO) is commonly encountered in patients with coronary artery disease presenting for angiography.^1-3 Most patients who present with CTO receive medical therapy or are referred for coronary artery bypass graft surgery.^1-3 CTO percutaneous coronary intervention (PCI) is a rapidly evolving alternative therapy with increasing procedural success and decreasing complication rates over time.^4,5 Several techniques have been developed to improve CTO PCI success rates that can be grouped into 3 categories: (1) antegrade wire escalation; (2) antegrade dissection/re-entry; and (3) retrograde.^6,7 The Boston Scientific Coronary CTO Crossing System (formerly the BridgePoint Medical System) was created to facilitate antegrade dissection/re-entry and consists of the CrossBoss catheter and the Stingray re-entry system. In the Facilitated Antegrade Steering Technique in Chronic Total Occlusions Trial (FAST-CTOs), use of the CrossBoss/Stingray system resulted in a high success rate (77%) among 147 patients in whom standard CTO PCI strategies had failed.⁸ This was achieved without increased complications compared to historical controls.⁸ Few studies have reported acute technical success and complication rates after use of the CrossBoss/Stingray devices,^6,8-15 but to date there is no report on subsequent clinical outcomes.⁶ This is of particular interest, as extensive antegrade dissection/re-entry techniques have been associated with high restenosis rates.^16-19 

Methods

Patient population. We retrospectively reviewed the medical records of consecutive patients who underwent CTO PCI between October 2009 (when the CrossBoss/Stingray devices became available at our institution) and December 2011, and obtained clinical follow-up until December 2012. The use of devices and crossing techniques for each patient was at the discretion of the treating interventional cardiologist. Two operators with CTO PCI experience performed all of the procedures. The study was approved by the institutional review board of our institution.

The Coronary CTO Crossing System. The system consists of the CrossBoss catheter and the Stingray balloon and wire (Figure 1).⁶ Briefly, the CrossBoss catheter is a metallic, over-the-wire catheter with a 1 mm blunt distal tip that can advance through the occlusion when the catheter is rotated rapidly using a proximal torque device (“fast spin” technique). The CrossBoss catheter can cross the CTO from true to true lumen in approximately one-third of cases or enter the subintimal space. If the latter occurs, the Stingray balloon and wire can be utilized for controlled re-entry into the distal true lumen. The Stingray re-entry system consists of two components: the Stingray orienting balloon and the Stingray re-entry guidewire. The Stingray balloon has two side exit ports located on diametrically opposite balloon surfaces immediately proximal to two radiopaque markers (yellow bands). The flat shape of the Stingray balloon orients one exit port automatically toward the vessel true lumen upon low pressure inflation (2-4 atm). The Stingray guidewire has a 0.0035˝ distal taper (Figure 1B, image insert) allowing it to re-enter the true vessel lumen through the exit port of the Stingray balloon that is facing the distal true lumen.⁶

Definitions. Coronary CTOs were defined as coronary lesions with Thrombolysis in Myocardial Infarction (TIMI) grade 0 flow for a duration of at least 3 months. Estimation of the occlusion duration was based on first onset of anginal symptoms, prior history of myocardial infarction in the target vessel territory, or comparison with a prior angiogram. Technical success was defined as CTO PCI revascularization with achievement of <30% residual diameter stenosis within the treated segment and restoration of TIMI grade 3 antegrade flow. Procedural success was defined as achievement of technical success with no in-hospital major periprocedural complications. Complications included any of the following adverse events prior to hospital discharge: death from any cause, Q-wave myocardial infarction, recurrent angina requiring urgent repeat target vessel revascularization, stroke, or tamponade requiring further intervention (pericardiocentesis or surgery). 

The primary outcome of interest was target lesion revascularization (TLR), defined as either attempted PCI of the previously stented segment(s) or referral for coronary artery bypass surgery due to target lesion restenosis. The incidence of TLR was evaluated only in patients in whom CTO PCI was successful and was assessed on a per lesion basis. During follow-up, repeat angiography was driven either because of clinical symptoms or because of participation in a research protocol that involved scheduled repeat coronary angiography. The following outcomes for each patient were also evaluated: (1) all-cause mortality; (2) cardiovascular mortality; (3) stroke; (4) definite/probable stent thrombosis, as defined by the Academic Research Consortium (ARC);²⁰(5) myocardial infarction, defined as typical rise and fall of cardiac biomarkers with associated chest pain; and (6) non-target vessel revascularization. Major adverse cardiac events (MACE) were defined as the composite of all-cause mortality, myocardial infarction, any unplanned repeat coronary revascularization, and stroke. For patients with >1 CTO PCI procedure, patients were included in the CrossBoss/Stingray cohort if they were ever treated with either device. We also performed an additional analysis to compare patients who were only treated with the CrossBoss catheter and those in whom the Stingray re-entry system was used. 

Statistical analyses. Continuous variables were presented as means with standard deviations and compared using the t-test or Wilcoxon rank-sum test, as appropriate. Categorical variables were expressed as percentages and compared using the chi-square or the Fisher’s exact test, as appropriate. The incidence of clinical events during follow-up was estimated using the Kaplan-Meier method and compared using the log rank test. All statistical analyses were performed with JMP version 10.0 (SAS Institute). Two-sided P-values of ≤.05 were considered statistically significant.

Results

Patient and lesion characteristics. During the study period, CTO PCI was performed in 170 consecutive patients at our institution, which included 189 CTO PCI attempts (8 patients had treatment of 2 CTO lesions and 11 patients had repeat CTO PCI attempts). The CrossBoss/Stingray system was used in 62 CTO PCI attempts (60 patients) as follows: use of the CrossBoss catheter in 40 cases, use of the Stingray system in 9 cases, and use of both devices in 13 cases (Figure 2). Of the cases in which the CrossBoss was the only device used, 5 were due to in-stent restenosis. 

Clinical, angiographic, and procedural characteristics of the patients are presented in Table 1. Most patients were men with high prevalence of hypertension, hyperlipidemia, and diabetes mellitus. Multivessel coronary artery disease was common, as was prior coronary artery bypass surgery. The right coronary artery was the most frequently targeted CTO vessel in both groups. Patients in whom the CrossBoss/Stingray system was used had similar baseline characteristics compared to patients treated with other strategies, with the exception of hyperlipidemia, which was more common in the CrossBoss/Stingray cohort. Lesion characteristics were also similar in both groups (Table 2). 

Procedural techniques and outcomes. Several important procedural differences were noted between the CrossBoss/Stingray and non-CrossBoss/Stingray groups (Table 1 and Table 2). The CrossBoss/Stingray System was used in cases with more frequent prior failed CTO PCI attempts and more commonly entailed a retrograde attempt and dual arterial access. More coronary guidewires and contrast were utilized in the CrossBoss/Stingray group and procedural/fluoroscopy time was longer, although the mean number of implanted stents was similar. Use of drug-eluting stents was also similar between the two groups, as was the incidence of periprocedural complications (Table 2). 

Clinical follow-up. Complete clinical follow-up was available for 168 of the 170 patients (98.8%). The median follow-up time was 1.81 years (interquartile range, 1.23 to 2.38 years). Follow-up angiography was performed in 73 patients (42.9%), driven either by symptoms (n = 33) or by participation in a research protocol (n = 40). Research protocol driven angiography was not statistically different between the two groups (CrossBoss/Stingray, 20.0% vs other strategies, 26.1%; P=.45). 

There were no statistical differences between the two cohorts with regard to TLR (Figure 3) or any other clinical outcomes (Table 3). Stroke and stent thrombosis were rare. One patient (1.7%) in the CrossBoss/Stingray group had a stroke 1.6 years after the index CTO PCI. No patient developed ARC definite stent thrombosis, whereas 1 patient in the CrossBoss/Stingray group (1.7%) had probable stent thrombosis (sudden cardiac death within 30 days from CTO PCI). The overall incidence of MACE was similar in the 2 groups (Figure 4). Clinical outcomes were similar among patients treated only with the CrossBoss catheter and those in whom the Stingray system was used (Figure 5 and Figure 6). 

Discussion

To the best of our knowledge, this study is the largest described single-center experience with the CrossBoss/Stingray devices and the first to report long-term clinical outcomes. The first key observation was that compared to cases in which the CrossBoss/Stingray system was not used, CTO PCI with the CrossBoss/Stingray system was associated with equally high success rates, in spite of higher case complexity in the latter group. The CrossBoss/Stingray group had higher rates of prior failed CTO PCI, higher fluoroscopy and contrast use, along with greater equipment utilization. The similar success rates in both cohorts reaffirms that the CrossBoss/Stingray devices provide an effective means to traverse some of the more challenging occlusions when other strategies fail.⁸ It is currently unclear what utility these devices may provide as part of a frontline strategy, as they have been predominantly evaluated as a “bail-out” against conventional techniques.^8,14,15 

Our study is reassuring in terms of acute procedural complications, which were similar in both cohorts. Perforation was initially a concern with use of the CrossBoss/Stingray system and was reported in 9.3% of cases in the pivotal clinical study.⁸ Perforation can occur if the CrossBoss catheter is advanced into small side branches, which led to our routine use of orthogonal projections and dual injection during these cases. In our cohort, there were 5 cases of coronary perforation, of which only 1 was in a CrossBoss/Stingray device-treated patient. This occurred during a case of attempted lesion crossing with the CrossBoss catheter, was contained, and did not require pericardiocentesis. Hence, use of the CrossBoss/Stingray devices appears to be safe.

Concerns have also been expressed that dissection/re-entry CTO PCI techniques, such as subintimal tracking and re-entry (STAR) or contrast-guided STAR, may lead to poor long-term outcomes due to high rates of in-stent restenosis.^16-19 By creating a dissection plane, side-branch vessel occlusion will occur, potentially limiting distal outflow and predisposing to high TLR risk. The CrossBoss/Stingray system, unlike the STAR and contrast-guided STAR techniques, aims to minimize the length of subintimal dissection, potentially lowering the risk for in-stent restenosis. Moreover, the device can often traverse the lesion into the distal true lumen without entering a dissection plane. In the FAST-CTO study, this occurred in one-third of cases.⁸ In the present study, we did not observe a significant difference in TLR between the CrossBoss/Stingray group compared to the non-CrossBoss/Stingray group, in spite of the higher case complexity in the latter group. There was also no difference in clinical event rates between patients treated with only the CrossBoss catheter and those treated with the Stingray system. In both patient cohorts, the overall TLR rates were higher than those reported in other studies despite the use of drug-eluting stents.^21-23 This is likely related to the high rates of diabetes, hyperlipidemia, prior coronary artery bypass surgery, as well as diffuse coronary artery disease, as demonstrated by the long mean stent length in this study. 

Study limitations. Our study has important limitations. Although it is the largest CrossBoss/Stingray device study reported to date, the number of patients was relatively low and hence type-II error is possible. Several patients underwent follow-up angiography as part of a research study protocol, which may have increased the overall TLR rates; however, both study groups had similar rates of research protocol driven angiography. The selection of crossing strategy was at the discretion of the operator and was dictated by the clinical needs at the time of PCI and not by a prespecified protocol. We also acknowledge that the CrossBoss/Stingray system consists of two separate devices that could ultimately be studied independently for safety and efficacy and that larger studies with longer-term follow-up are ultimately necessary to define outcomes with the use of these devices. 

Conclusion

In summary, CTO PCI with the CrossBoss/Stingray system is associated with equally high success and equally low complication rates as other techniques, both immediately post procedure and during long-term follow-up, in spite of its use in higher complexity cases. 

References

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From the VA North Texas Healthcare System and University of Texas Southwestern
Medical Center, Dallas, Texas.

Disclosure: The authors have completed and returned the ICMJE Form for Disclosure
of Potential Conflicts of Interest. Dr Banerjee receives research grants from Boston
Scientific and The Medicines Company; consultant/speaker honoraria from Gilead, St
Jude, Cordis, Boehringer Ingelheim, Sanofi, and Medtronic; is a consultant to Covidien;
and has ownership in MDCARE GLOBAL (spouse) and intellectual property
in HygeiaTel. Dr Brilakis reports consulting fees/speaker honoraria from Sanofi, Janssen,
St Jude Medical, Terumo, Asahi Intecc, Abbott Vascular, and Boston Scientific;
research support from Guerbet; spouse is an employee of Medtronic.

Manuscript submitted April 1, 2013, provisional acceptance given May 6, 2013,
final version accepted August 9, 2013.

Address for correspondence: Emmanouil S. Brilakis, MD, PhD, Dallas VA
Medical Center (111A), 4500 South Lancaster Road, Dallas, TX 75216. Email:
esbrilakis@gmail.com