In-stent restenosis (ISR) after stent implantation remains a frequent problem in coronary interventional therapy. Although drug-eluting stents (DES) significantly reduce the rates of restenosis and target lesion revascularization (TLR) [1,2], the increasing use of DES in complex patients and lesions with high restenotic potentials has resulted in double-digit restenosis rates [3,4].

The best treatment strategy for ISR has not been established and its identification remains challenging, although several treatment options, such as, conventional balloon angioplasty (BA), intracoronary brachytherapy, and the implantation of an additional stent are available. In recent years, the local delivery of an antiproliferative drug from drug-eluting balloons (DEB) has emerged as a potential alternative for the treatment of ISR. However, although previous clinical trials had reported DEB might be safe and effective for the treatment of ISR [5-8], its role in the management of ISR has not been comprehensively established. Therefore, the aim of the study was to assess the safety and efficacy of DEB as compared with conventional BA or the implantation of a second DES for the treatment of ISR.

The retrospective study was performed using the Gachon University Gil Medical Center percutaneous coronary intervention (PCI) database. Patients who underwent PCI in ISR lesions were selected and constituted the eligible 177 patients (188 lesions) between January 2006 and May 2012. Inclusion criteria were an ISR in bare-metal or DES, reference vessel diameter of 2.5 to 3.5 mm, and lesion length < 30 mm. Exclusion criteria were thrombus within the target vessel, clinically significant calcification of the target lesion, bifurcation lesion, total coronary artery occlusion, contraindication to dual antiplatelet therapy. The patients were divided into three treatment modality groups, as follows; the BA group (n = 65, 36.7%), members of which were treated by conventional BA using an uncoated balloon catheter, the DES group (n = 54, 30.5%), members were implanted with a second DES, and the DEB group (n = 58, 32.8%), treated by BA using a DEB. The treatment modality for ISR was decided by the interventional cardiologist. All ISR lesions were predilated with an uncoated balloon catheter according to the size of the restenotic stent. In the DEB group, a paclitaxel-eluting balloon was used (SeQuent Please balloon catheter, B. Braun Melsungen, Berlin, Germany) and the diameter of DEB had to be at least the diameter of the pre-dilatation balloon. Patients received heparin to an activated clotting time of 200 to 250 seconds. Dual antiplatelet therapy with acetylsalicylic acid 100 mg and clopidogrel 75 mg once daily was prescribed for at least 6 months. Clinical and demographic characteristics, angiographic and procedural data, and clinical follow-up outcomes were reviewed from medical records. ISR morphology was classified according to the Mehran classification [9]. The primary end point was defined as the occurrence of a major adverse cardiovascular event (MACEs), which included cardiac death, myocardial infarction (MI), and TLR. Stent thrombosis was defined as described by the Academic Research Consortium as ‘definite’ when acute coronary syndrome was present with angiographic or autopsy evidence of thrombus or occlusion, or as ‘probable’ when unexplained death occurred within 30 days of the procedure or acute MI involving the target vessel occurred without angiographic confirmation [10].

In this study, we evaluated the efficacy and safety of DEB with respect to clinical outcomes for the treatment of ISR as compared with DES and conventional BA. Our results show no significant difference between these three modalities with respect to MACE rate, and suggest DEB can be a feasible and effective option for the treatment of ISR.

The optimal treatment for ISR remains to be determined. Conventional BA for ISR is limited by high rates of repeat restenosis (39% to 45%) [11,12], and BMS implantation has similar results to conventional BA for the treatment of ISR [11]. The implantation of an additional DES, that is, a sirolimus- or paclitaxel-eluting stent, in ISR lesions resulted in rates of restenosis of 14% to 22% [13,14]. However, these stent-in-stent approaches raise concerns about the long-term implications of several stent layers in the native coronary artery wall regarding: (1) an increased risk of late stent thrombosis due to the chronic inflammation of non-resorbable polymers or delayed, incomplete endothelialization; (2) suboptimal stent geometry or insufficient stent expansion, which could cause recurrent restenosis; and (3) limited treatment options in case of recurrent restenosis after second stent implantation [6].

DEB offers a potential alternative for the treatment of ISR, and can provide several advantages as compared with second stent implantation as follows: (1) the homogenous delivery of antiproliferative medication; (2) the temporary release of high concentrations of medication, which can lead to a slight enhancement of long-term healing; (3) the absence of multiple layers of stents and polymers, which can decrease chronic inflammation and late stent thrombosis; and (4) a significant reduction in dual antiplatelet therapy [15,16].

The Treatment of In-Stent Restenosis using Paclitaxel Coated Balloon Catheters (PACCOCATH ISR I and PACCOCATH ISR II) trials demonstrated that patients treated with paclitaxel-coated balloon had better angiographic results (less late luminal loss and binary restenosis) and improved clinical outcomes at 12 months and more long-term follow-up, as compared with patients treated with an uncoated balloon [5,7,17].

In the Paclitaxel-Eluting Balloon Catheter in Coronary Artery Disease (PEPCAD II ISR) study, the use of a paclitaxel-eluting balloon for the treatment of BMS ISR significantly reduced late lumen loss and binary restenosis rate at 6-month angiographic follow-up visits and improved 1-year event-free survival as compared with paclitaxel-eluting stents [18]. In addition, the PEPCAD DES trial showed that treatment of DES ISR with a paclitaxel-coated balloon was significantly associated with lower late lumen loss and with binary restenosis rates and MACEs than conventional BA [8]. Recently, Byrne et al. [19] reported that a paclitaxel-eluting balloon was non-inferior to repeat stenting with a paclitaxel-eluting stent in terms of diameter stenosis, binary restenosis rate, and TLR, and that both treatments were superior to conventional BA for the treatment of DES ISR.

This study has several limitations. First, small number of patients was the major limitation. Second, the lesions with ISR were not classified into DES ISR or BMS ISR lesions according to previous stent type or risk factors, especially such as diabetes, due to the limited number of patients. The limited number of patients and the heterogeneous lesions of ISR might cause no significant results of the efficacy of DES or DEB for the treatment of ISR, compared with conventional BA. Third, it involved retrospective analysis, and thus, follow-up periods varied widely. Fourth, we did not compare angiographic results, such as, late lumen loss or binary restenosis, with respect to clinical outcomes. Therefore, large-scale randomized trials are required to determine the optimal treatment and the role of DEB for coronary ISR lesions.

In conclusion, based on this small, retrospective study, DEB might be feasible and efficacious similarly to BA to DES for the treatment of coronary ISR.