The present study demonstrated the clinical effectiveness of DCB treatment for patients with FP-CTO diseases. Multivariate analysis demonstrated three independent risk factors: 1) hemodialysis, 2) CLTI, and 3) restenosis lesion. The administration of DAPT was a significant protective factor. To the best of our knowledge, this is the largest population studied regarding the relationship between DCB and FP-CTO in real-world target populations. Compared with previous studies, we report a favorable rate of 12-month primary patency (79.8%) and acceptable bailout stent rate (8.9%); therefore, DCB treatment is an acceptable strategy for FP-CTO (AbuRahma et al., 2019; Tepe et al., 2019; Listro et al., 2019).
Successful DCB treatment requires the achievement of two conflicting factors: 1) adequate luminal gain and less severe dissection. To establish these contradictory factors, the presence of CTO is very challenging. As reported in a previous study, the presence of CTO is significantly associated with the incidence of severe dissection (Fujihara et al., 2017). A large volume of plaques in the CTO may lead to large dissections and significant recoil after balloon angioplasty, causing target lesion failure (or requiring bailout stents). Recent studies have reported acceptable results of DCB treatment for complex FP lesions; however, they had a high rate (21.0–46.5%) of bailout stent (Tepe et al., 2019; Listro et al., 2019; Bausback et al., 2019). Currently, there is no high-level evidence regarding the effectiveness of the “leaving nothing behind” strategy for patients with complex FP lesions. A previous single-center study reported outstanding 12-month primary patency (92.7%) of IVUS-guided DCB treatment for FP-CTO without bailout stent (Hayakawa et al., 2022). They performed all procedures using an IVUS-guided intraluminal approach, and DCB size was decided based on the IVUS findings. Furthermore, only cases with sufficient results regarding lesion preparation (without residual stenosis [> 50%] and severe dissection [NHLBI grade D or higher]) were enrolled in the DCB cohort. Although the level of evidence was insufficient, their important findings suggested that precise procedures and judgment may improve the clinical outcomes of DCB treatment for complex FP lesions. Furthermore, this might also reduce the incidence of bailout stent, maximizing the benefit of the “leaving nothing behind” strategy. In our multicenter study, lesion length (21.9 cm), occlusion length (14.5 cm), and PACCS grade 3 or 4 (33.1%), were more severe than in the IN.PACT global CTO imaging cohort (lesion length: 22.8 cm, CTO length: 11.9 cm, severe calcification: 3.2%). Despite the lesion severity, the bailout stent rate was notably lower (8.9%) than that of the IN.PACT global study (46.5%) (Tepe et al., 2019). The reason for this is unclear; however, we suspect that the high rate of IVUS-guided procedures (77.2%) avoided the need for subintimal crossing and selection of an appropriate device size. As a result, favorable primary patency and lower bailout stent rates were observed. The first randomized controlled trial (RCT) of IUVS-guided FP EVT (mainly DCB treatment) demonstrated the clinical benefit of IVUS (Allan et al., 2022). In future clinical trials, it will be necessary to clarify 1) what IVUS changes in the procedure and 2) how it has affected the outcomes.
This study demonstrated that 1) hemodialysis, 2) CLTI, and 3) restenosis lesions were independent risk factors and that the use of DAPT was a protective factor for 12-month restenosis after DCB treatment for FP-CTO. The clustering of these risk factors was associated with a lower primary patency rate (66.2%). However, when none of these risk factors were present, an outstanding primary patency rate (90.2%) was noted. This might be beneficial in daily clinical practice because it can easily predict the lesion prognosis and stratify the risk, resulting in a better strategy selection. The risk factors identified in our study overlapped with the predictors of restenosis after fluoropolymer-based drug-eluting stent (FP-DES) implantation. Iida et al. reported hemodialysis, CLTI, and history of revascularization were risk factors for restenosis in FP-DES. A smaller reference vessel diameter, CTO, and spot stenting were also risk factors for restenosis (Iida et al., 2022). Hemodialysis, CLTI, and restenosis lesion might be associated with lesion severity, and therefore, might negatively influence durability after DCB treatment.
In this study, the administration of DAPT was demonstrated to be a protective factor for restenosis. It is well known that cilostazol prevents neointimal hyperplasia, resulting in a reduced restenosis rate after EVT for FP lesions (Soga et al., 2018). It is unclear how DAPT reduces restenosis after DCB treatment; however, DAPT might reduce the incidence of thrombosis-related target lesion failure, resulting in a reduction of restenosis. In this study, the effects of DAPT between restenosis and re-occlusion were not evaluated separately. Data on DAPT after EVT are scarce, and it is not clear whether longer DAPT provides more benefit. A previous report showed that DAPT was associated with prolonged survival for patients with critical limb ischemia who underwent arterial revascularization; however, no benefit was shown in patients with claudication (Soden et al., 2016). An RCT of the efficacy of DAPT (aspirin plus clopidogrel) reported reduced peri-interventional platelet activation and a lower revascularization rate than aspirin plus placebo (Tepe et al., 2012). Our study suggests DCB treatment for FP-CTO is reasonable for patients without CLTI, hemodialysis, or a history of target lesion EVT. Furthermore, if the patient has sufficient tolerance to DAPT (equal to non-high bleeding risk), the prolongation of DAPT should be considered.
In this study, previously reported risk factors for restenosis, such as vessel diameter, lesion length, severe calcification, and dissection were not revealed as risks for restenosis. Furthermore, angioplasty with DCB was performed for cases with successful lesion preparation; therefore, DCB may be effective even for those with long lesions, small vessels, or severe calcification if successful lesion preparation (sufficient luminal gain and less dissection) can be obtained.
There is no clear consensus on the definition of successful lesion preparation. Achievement of sufficient luminal gain and less severe dissection are essential. Regarding the definition of “sufficient” luminal gain, Horie et al. proposed a cutoff value of postprocedural IVUS-evaluated minimum luminal area (MLA) of 12.7 mm2 (Horie et al., 2022). Angiographic evaluation is the gold standard for the evaluation of dissection. A previous study showed a significant relationship between non-stented moderate-to-severe (angiographic) dissections after DCB treatment and the incidence of major adverse limb events (Giannopoulos et al., 2021). We evaluated dissections mainly by the NHLBI classification. Only 16% of the subjects had a grade C or more dissection. Therefore, it was difficult to evaluate the dissection pattern and durability. Kozuki et al. reported the presence of IVUS-detected severe dissection (dissection angle > 63°) was significantly associated with 12-month restenosis (Kozuki et al., 2021). In this study, 77.2% of subjects received IVUS-guided DCB treatment, possibly resulting in favorable patency without the need for bailout stent. However, over 20% of patients still received angiographic-guided treatment. Furthermore, there were many cases with missing data of IVUS parameters. Therefore, we could not adequately evaluate the association between clinical outcomes and IVUS parameters (such as post-procedural MLA and dissection angle). Further studies are needed to reveal the clinical benefit of IVUS.
4.1 Limitations
This study had several limitations. The present study was a retrospective, nonrandomized study with a small sample size; therefore, the evidence level is not high. All clinical events were evaluated on-site and there was no independent clinical events committee. The application of DCB treatment was selected based on each operator’s decision without following any pre-established protocol. There may have been selection bias. In the future, a well-designed, large-scale prospective study (with an independent event committee) will be required for equivalent evaluation.