Abstract: Aims. To investigate the impact of novel, polymer-jacketed, tapered-tip, low-force guidewires with composite-core, dual-coil design (Fielder XT-R and Fielder XT-A; Asahi Intecc) on antegrade wire escalation (AWE) crossing of coronary chronic total occlusion (CTO) lesions. Methods. From March of 2017 to December 2018, a total of 164 consecutive CTO lesions at a single institution were treated with a primary AWE strategy using either Fielder XT-R or XT-A (XTRA) as the starting wire regardless of lesion characteristics. Success rates, wiring times, and complications were analyzed. Results. The mean Japanese (J)-CTO score was 3.71 ± 1.27, mean PROGRESS-CTO score was 2.46 ± 1.15, and mean PROGRESS-CTO Complications score was 3.9 ± 2.0. Mean CTO length was 25.0 ± 0.5 mm, 48 lesions (29.3%) were previously bypassed, 77 lesions (47.0%) had moderate to severe calcification, and 62 lesions (37.8%) had moderate to severe tortuosity. Antegrade success rates using XTRA wires were 79%, 60%, and 17% of lesions with J-CTO scores of 0-1, 2-3, and 4-5, respectively. In successful antegrade XTRA cases, median wiring times were 6.5 min (interquartile range [IQR], 5.0-11.0 min), 9.0 min (IQR, 4.2-14.0 min), and 12.0 min (IQR, 9.0-15.0 min) for J-CTO scores of 0-1, 2-3, and 4-5, respectively, and differed non-significantly according to J-CTO score (P=.20). Complication rates were low (In-hospital major adverse cardiac event rate, 1.3%) with no wire perforations caused by XTRA wires. Conclusions. Use of Fielder XTRA wires as part of an AWE strategy in CTO percutaneous coronary interventions may facilitate more efficient antegrade lesion crossing and overall procedural success in lesions that have been traditionally challenging to treat using an antegrade-first approach.
J INVASIVE CARDIOL 2020;32(5):161-168.
Key words: chronic occlusions, chronic total occlusions, CTO
The initial approach to chronic total occlusion (CTO) intervention has become dichotomized into the North American hybrid algorithm putting less emphasis on soft tissue tracking and antegrade wire escalation (AWE) vs the Asia-Pacific algorithm that strongly favors an antegrade-first philosophy.1,2 As the limitations of early CTO wires (non-tapered tips, stiffness, and lack of steerability) pushed operators to alternative approaches, recent advances in wire technology, as embodied by the composite-core design of the Fielder XT-R and XT-A (XTRA) wires (Asahi Intecc), have made the antegrade approach more efficient, safe, and feasible.3,4 Both the Euro CTO Club and the Asia-Pacific CTO Club recommend the Fielder XT-R wire as the initial choice for antegrade CTO wiring.1,3 Following the availability of XTRA wires in the United States, our center migrated toward an Asia-Pacific approach to CTO interventions. In this report, we describe our initial experience in terms of procedural outcomes, efficiency, and safety using the XTRA wires in a North American population employing an AWE primary crossing strategy irrespective of angiographic lesion characteristics.
This was an investigator-initiated retrospective study with no formal industry funding. A total of 155 unique patients and 164 unique CTO lesions were included in the analysis. The cohort represents all CTO procedures performed by dedicated CTO operators at the Cleveland Clinic in Cleveland, Ohio from March, 2017 to December, 2018. During this time, the institutional practice was to begin all CTO cases antegrade (regardless of lesion characteristics) by approaching the CTO with a workhorse wire and microcatheter, then exchanging for a Fielder XT-R or XT-A for initial lesion engagement. Therefore, this cohort represents a non-selected series of consecutive CTO patients treated during this period. The study was approved by the institutional review board of the Cleveland Clinic.
Definitions. Coronary CTO was defined as a coronary lesion with Thrombolysis in Myocardial Infarction (TIMI) flow grade 0 of at least 3-month duration as estimated by the primary operator based on clinical history and angiographic appearance. Calcification was defined as mild (minimal spots on angiography), moderate (≤50% of reference lesion diameter), or severe (≥50% of reference lesion diameter). Tortuosity was defined as straight (<70°, 1 bend), mild (>70°, 1 bend), moderate (2 bends >70° or 1 bend >90°), or severe (2 bends >90° or 1 bend >120°). Tapered stump was defined as a funnel-shaped origin of the proximal lesion cap. Interventional collaterals were defined as collateral vessels deemed amenable to crossing with a guidewire and microcatheter. Good distal landing zone was defined as a distal vessel ≥2.0 mm in diameter without diffuse disease. Good distal opacification was defined as similar to the proximal vessel and faint distal opacification as less than the proximal vessel. Wiring time was defined as time from initial workhorse wire insertion into the CTO vessel to the time of crossing the lesion into the distal true lumen. If multiple CTO lesions were attempted during a single procedure, only the first CTO lesion for wiring time was counted. The Multicenter CTO Registry in Japan (J-CTO) score was calculated as described by Morino et al.5 The recommended primary crossing strategy per the hybrid algorithm was determined using the flow chart created by Michael et al.6 A lesion had to satisfy all three retrograde criteria to be classified as recommended for a primary retrograde approach. Lesions not meeting these criteria and with length ≥20 mm were classified as recommended for a primary antegrade dissection and re-entry (ADR) approach. All other lesions were classified as recommended for a primary AWE approach. Technical success was defined as successful CTO recanalization with achievement of <30% residual stenosis and TIMI 3 flow. In-hospital major adverse cardiac event (MACE) rate was defined as a composite of death, myocardial infarction (MI), target-vessel revascularization, tamponade requiring pericardiocentesis or surgery, and stroke. Acute MI was defined using the fourth universal definition of MI (type 4a MI).7 A small hematoma was defined as <5 cm, and a large hematoma as ≥5 cm.
Statistical analysis. Categorical variables are expressed as number and percentage, and continuous variables as mean ± standard deviation or median with interquartile range (IQR) for non-normally distributed variables. Wiring time trends per J-CTO score were compared using a Spearman’s rank correlation test. Wiring times by hybrid algorithm proposed strategy were compared using the Kruskal-Wallis test. Success rates were compared using a Chi-square test. All statistical analyses were performed with R version 3.4.1 in R-studio environment, version 1.1.463 (R Foundation for Statistical Computing). A 2-sided P-value ≤.05 was considered to indicate statistical significance.
Patient clinical and angiographic characteristics. A total of 155 patients and 164 CTO lesions treated with a primary AWE strategy using XTRA were analyzed. Baseline clinical characteristics are summarized in Table 1. The mean age was 64 ± 9.6 years, 137 (83.5%) were male, 61 (37.2%) had prior coronary artery bypass grafting, and 75 (45.7%) had diabetes. The majority of procedures were performed for symptom relief (69.5%) and 58.8% of patients had Canadian Cardiovascular Society class ≥3 angina. The average ejection fraction was 51.4 ± 13.4%.
Angiographic characteristics are shown in Table 2. Fifty-one lesions (31.1%) were prior failures, 26 (15.9%) were in-stent restenoses, and 48 (29.3%) were previously bypassed vessels. The majority of lesions (41.1%) were in the right coronary artery. Mean CTO length was 25.0 ± 14.0 mm and mean vessel diameter was 2.4 ± 0.5 mm. Sixty-four lesions (39.0%) had an ambiguous proximal cap, 100 (61.0%) had a tapered stump, 77 (47.0%) had moderate to severe calcification, and 62 (37.8%) had moderate to severe tortuosity. The mean J-CTO score was 3.71 ± 1.27, mean PROGRESS-CTO score was 2.46 ± 1.15, and mean PROGRESS-CTO Complications score was 3.9 ± 2.0.
Procedural details. Procedural strategy and technical success are summarized in Table 3. An initial AWE crossing strategy was employed in all cases. Overall technical success rate was 84.1%, with 67.7% of lesions crossed antegrade, 12.8% crossed retrograde, and 3.7% crossed using ADR. The Fielder XT-R was used in 107 cases (52.2%) and Fielder XT-A was used in 98 cases (59.8%). One hundred cases (61.0%) were performed using biradial access. The mean number of guidewires used was 4.2 ± 2.1, the mean number of microcatheters used was 1.5 ± 0.8, and the mean total stent length was 53.2 ± 31.8 mm.
Success rates. Technical success rates stratified by J-CTO score and wire/strategy employed are depicted in Figure 1. As all cases were started using XTRA wires, the “any wire antegrade success” column denotes the use of XTRA plus any additional wires as part of an antegrade strategy. The “any wire/strategy” column denotes cases started antegrade with XTRA and eventually crossed using any wire or advanced strategy (retrograde, ADR). Antegrade success rates using XTRA were 79% for J-CTO score 0-1, 60% for J-CTO score 2-3, and 17% for J-CTO score 4-5 (P<.001); success rates using any antegrade wire were 89% for J-CTO score 0-1, 77% for J-CTO score 2-3, and 37% for J-CTO score 4-5 (P<.001); success rates using any strategy/wire were 100% for J-CTO score 0-1, 87% for J-CTO score 2-3, and 70% for J-CTO score 4-5 (P<.01). Stratifying by proposed hybrid algorithm strategy (Figure 2), success rates for antegrade wiring with XTRA were 74% for a proposed antegrade strategy, 44% for a proposed ADR strategy, and 24% for a proposed retrograde strategy (P<.001); success rates for any wire antegrade were 88% for a proposed antegrade strategy, 59% for a proposed ADR strategy, and 39% for a proposed retrograde strategy (P<.001); success rates for any wire/strategy were 91% for a proposed antegrade strategy, 82% for a proposed ADR strategy, and 76% for a proposed retrograde strategy (P=.25).
Evaluation of success rates in selective subgroups deemed to be clinically relevant is shown in Figure 3. Success rates were significantly lower in lesions with moderate/severe calcification, moderate/severe tortuosity, lesion length ≥20 mm, a non-tapered stump, an ambiguous cap, and with previous bypass grafts. Success rates were lower in left circumflex lesions (40% for left circumflex vs 57% for left anterior descending and 55% for right coronary artery), although the difference did not reach statistical significance (P=.18).
Wiring times. Wiring times in successful cases are depicted in Figures 4 and 5 and Tables 4 and 5. Median wiring time for XTRA successful antegrade crossing was 6.5 min (IQR, 5.0-11.0 min) for J-CTO 0-1, 9.0 min (IQR, 4.0-14.0 min) for J-CTO 2-3, and 12.0 min (IQR, 9.0-15.0 min) for J-CTO 4-5 (Ptrend=.20); median time for any wire successful antegrade crossing was 22.0 min (IQR, 19.5-24.5 min) for J-CTO 0-1, 29.0 min (IQR, 20.5-63.2 min) for J-CTO 2-3, and 18.0 min (IQR, 15.0-26.0 min) for J-CTO 4-5 (Ptrend=.06); median time for any wire/strategy successful crossing was 45.0 min (IQR, 37.5-78.5 min) for J-CTO 0-1, 98.0 min (IQR, 46.0-108.0 min) for J-CTO 2-3, and 68.0 min (IQR, 47.0-111.5 min) for J-CTO 4-5 (Ptrend<.001). When stratifying by the proposed hybrid algorithm approach, the median wire crossing times for XTRA successful antegrade crossing were 8.0 min (IQR, 4.5-13.5 min) for proposed antegrade cases, 9.0 min (IQR, 5.0-11.0 min) for proposed ADR cases, and 15.0 min (IQR, 14.8-16.0 min) (P=.10) for proposed retrograde cases; median times for any wire successful antegrade crossing were 22.0 min (IQR, 17.5-31.0 min) for proposed antegrade cases, 46.0 min (IQR, 27.0-79.0 min) for proposed ADR cases, and 14.0 min (IQR, 13.5-41.5 min) (P=.12) for proposed retrograde cases; median times for any wire/strategy successful crossing were 69.5 min (IQR, 47.0-110.2 min) for proposed antegrade cases, 34.0 min (IQR, 32.0-39.5 min) for proposed ADR cases, and 108.0 min (IQR, 80.0-110.0 min) (P<.01) for proposed retrograde cases.
Procedural complications. Table 6 summarizes in-hospital complications. Overall MACE rates were low, at 1.3%. There were 7 total perforations, two of which were wire perforations of the CTO vessels with non-XTRA wires. There were no perforations directly related to use of XTRA wire. There were no in-hospital deaths.
In the present study, we report our initial clinical experience with novel (to the United States), dual-coil, composite-core guidewires (Fielder XT-R and Fielder XT-A) with design characteristics optimized for AWE-CTO crossing. The major findings of our paper are: (1) the Fielder XTRA wires are able to achieve high rates of antegrade success in low-complexity lesions; (2) when able to cross antegrade, the Fielder XTRA wires maintain low wiring times despite lesion complexity; (3) the Fielder XTRA wires do not perform as well in traditionally challenging antegrade subsets including moderate/severe calcification, moderate/severe tortuosity, lesions ≥20 mm, non-tapered stumps, ambiguous caps, and bypassed vessels; and (4) the Fielder XTRA wires have low complication rates when used as part of an antegrade approach.
Our results show that both the J-CTO score and hybrid algorithm are good predictors of procedural success when attempting to wire a CTO antegrade using the XTRA wires. XTRA wires showed good performance up to a J-CTO score of 3, achieving 79% and 60% success rates for J-CTO scores of 0-1 and 2-3, respectively, without the need for an additional wire. At higher J-CTO scores (4-5), the XTRA wires have limited ability to cross on their own (17% success rate), although they may facilitate the AWE approach with the addition of higher-force wires as needed (37% overall antegrade success when starting with XTRA). When the hybrid algorithm recommended starting antegrade, the XTRA crossed on its own 74% of the time, but this number decreased to 44% when ADR was recommended and 24% when retrograde was recommended. Hence, the initial limitations of antegrade wiring that led to the development of the hybrid algorithm, as a general trend, also apply to the XTRA wires. Comparing the performance of the XTRA wires with other reports is difficult, as most studies do not break down the specific wire that crossed the lesion. For example, in the RECHARGE registry, 94% of cases with a J-CTO score ≤1 were started with an AWE approach, with 86% achieving antegrade success. In RECHARGE lesions with a J-CTO score ≥2, 74% were started with AWE and 50% achieved success. Overall, our results appear similar, although it is not clear how many of the cases in the RECHARGE registry required the use of a high-force, stiff wire. When RECHARGE was broken down by hybrid algorithm strategy, 77% of cases were started antegrade with only 62% achieving antegrade success.8 Our results compare very favorably with these findings regardless of the inclusion of the other wires used in RECHARGE, as we were able to achieve antegrade success with the XTRA alone in 74% of cases recommended for AWE by the hybrid algorithm. Our results also compare favorably with a recent report from the PROGRESS registry that showed AWE success rates of 50.6% and 31.9% in lesions with J-CTO score 2-3 vs our success rates of 60% with XTRA alone for J-CTO score 2-3 and overall antegrade success rate of 77% with use of any wire. Furthermore, in PROGRESS, only 53.4% of cases recommended for AWE by the hybrid algorithm ultimately achieved antegrade success.9 Our results are also supported by those presented by Galassi et al,10 who compared success rates by J-CTO score in two different eras (2005-2009 vs 2010-2014). In this study,10 during the 2005-2009 era, a soft (<1 g) wire was used to successfully cross the CTO lesion in 51.6%, 39.6%, 32.8%, and 32.3% for J-CTO scores of 0, 1, 2, and ≥3, respectively, as compared with 94.4%, 86%, 76%, and 61.5%, respectively, for the same J-CTO scores in the 2010-2014 era. As XTRA became available in Europe in 2010, these results may at least partially reflect the impact of these wires, although specifics regarding wire use and crossing strategy were not reported.10 Our study is the first to specifically comment on the performance of the XTRA wires.
Selective subgroup analysis showed the XTRA wires were less successful in calcified lesions, tortuous lesions, lesions ≥20 mm, non-tapered stumps, ambiguous caps, and bypassed vessels. There was a trend toward lower success rates in left circumflex lesions that did not reach statistical significance. These findings are similar to previously reported correlates of success in CTO percutaneous coronary interventions. In the PROGRESS registry, calcification, tortuosity, and proximal cap ambiguity were also associated with lower success rates using any CTO approach.9 A report by Suzuki et al11 analyzed the results of expert Japanese operators employing a primary antegrade approach and found severe calcification and tortuosity of the CTO lesion to be the only multivariate predictors of failure. Alessandrino et al12 developed a predictive score for CTO wiring success based on a database of procedures performed at two centers in France from 2004-2013. Although any CTO crossing technique could be used, only 9.3% employed a retrograde approach, implying a preference toward antegrade wiring. Independent predictors of failure in this study were lesion calcification, previous coronary artery bypass grafting, length ≥20 mm, prior MI, blunt stump, and non-left anterior descending coronary artery lesion.12
One of the most intriguing findings of our study is that in lesions where the XTRA was able to cross antegrade, wiring times were low and not significantly impacted by J-CTO score or the recommended hybrid algorithm strategy. In the original derivation of the J-CTO score by Morino et al,5 successful antegrade guidewire crossing within 30 min was achieved in 87.7%, 67.1%, 42.4%, and 10.0% for J-CTO scores of 0, 1, 2, and ≥3, respectively. This compares favorably with our median wiring times of 6.5 min, 9.0 min, and 12.0 min for J-CTO scores of 0-1, 2-3, and 4-5, respectively. These results are not directly comparable with the study by Morino et al, as their results represented use of any antegrade wire, including high-force, stiff wires that were likely to be used in more complex cases, as opposed to those able to be crossed in our study with the XTRA wires. However, in our J-CTO 2-3 category, we achieved 60% success using XTRA with a median wiring time of 9 min, which does represent a direct improvement in outcome when compared with the Morino study that showed wiring time <30 min in only 42.4% of patients with J-CTO score of 2 (J-CTO scores 3-5 were combined, so comparison with a score of 3 is not possible). In addition, even when allowing any antegrade wire, we were able to achieve success in 77% of patients with J-CTO score of 2-3 with a median wiring time of 29 min, providing some support to the notion that the XTRA may facilitate antegrade wiring with additional wires. Notably, Morino’s study occurred prior to the development of XTRA; hence, it is possible our improved wiring times are at least partially due to this new technology. In addition, in a 2014 study by Michael et al,6 the mean time used per crossing approach was 32 ± 23 min. While this number represents any crossing strategy, it does provide some frame of reference for the significance of our results.
Lastly, use of XTRA wires was associated with low complication rates. We report only 4 wire perforations, none of which were related to use of XTRA wires and only 2 of which were wire perforations of the CTO vessel (the other 2 wire perforations occurred during collateral crossing). These results compare favorably with historical cohorts. In a 2010 report by expert Japanese operators,13 there was a 0.2% rate of perforation/contrast staining in the CTO artery. The 2018 update of the PROGRESS registry reported a 1.16% perforation rate in antegrade procedures.9 Notably, rates of perforation in this report were 5.22% with the ADR approach and 7.52% with a retrograde approach, further supporting the potential safety advantage of enhancing the success of antegrade wiring.
Study limitations. Our study is limited by the lack of a direct comparison with other potential starting wires performed during the same time period. Furthermore, our results represent the experience of a single institution during a particular time period. Whether or not these results are applicable to all CTO operators, each with their own skill set, cannot be determined by this report. Lastly, we do not have information on how or why an operator chose to persist with the XTRA wire or move to a different wire, making the mechanism of antegrade wire failure unclear.
We provide our initial experience with the Fielder XT-R and XT-A wires in a contemporary population of unselected CTO patients treated at a single center. We believe our results show excellent performance for the XTRA wires in both procedural success and wiring times, with relative improvements as compared with historical reports throughout the spectrum of lesion complexity. We suggest operators consider starting with these wires as part of an initial antegrade wiring approach and speculate that technological advancements such as the XTRA wires may change the spectrum of lesion recommended for an antegrade-first approach.
From the Department of Cardiovascular Medicine, Cleveland Clinic, Cleveland, Ohio.
Disclosure: The authors have completed and returned the ICMJE Form for Disclosure of Potential Conflicts of Interest. Dr Khatri reports an institutional research grant from Asahi Intecc and honoraria/consulting fees from Abbott Vascular and Boston Scientific. Dr Ellis reports consultant income from Abbott Vascular, Boston Scientific, and Medtronic. The remaining authors report no conflicts of interest regarding the content herein.
Manuscript submitted December 18, 2019 and accepted given December 26, 2019.
Address for correspondence: Dr Jeffrey Rossi, Cleveland Clinic, 9500 Euclid Avenue, J2-3, Cleveland, OH 44195. Email: firstname.lastname@example.org
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