Prevalence and anatomical factors associated with stent under-expansion in non-severely calcified lesions.

BACKGROUND: Stent underexpansion, typically related to lesion calcification, is the strongest predictor of adverse events after percutaneous coronary intervention (PCI). Although uncommon, underexpansion may also occur in non-severely calcified lesions. AIM: We sought to identify the prevalence and anatomical characteristics of underexpansion in non-severely calcified lesions. METHODS: We included 993 patients who underwent optical coherence tomography-guided PCI of 1051 de novo lesions with maximum calcium arc <180°. Negative remodeling (NR) was the smallest lesion site external elastic lamina diameter that was also smaller than the distal reference. Stent expansion was evaluated using a linear regression model accounting for vessel tapering; underexpansion required both stent expansion <70% and stent area <4.5mm2. RESULTS: Underexpansion was observed in 3.6% of non-heavily calcified lesions (38/1051). Pre-stent maximum calcium arc and thickness were greater in lesions with versus without underexpansion (median 119° vs. 85°, p = 0.002; median 0.95 mm vs. 0.78 mm, p = 0.008). NR was also more common in lesions with underexpansion (44.7% vs. 24.5%, p = 0.007). In the multivariable logistic regression model, larger and thicker eccentric calcium, mid left anterior descending artery (LAD) location, and NR were associated with underexpansion in non-severely calcified lesions. The rate of underexpansion was especially high (30.7%) in lesions exhibiting all three morphologies. Two-year TLF tended to be higher in underexpanded versus non-underexpanded stents (9.7% vs. 3.7%, unadjusted hazard ratio [95% confidence interval] = 3.02 [0.92, 9.58], p = 0.06). CONCLUSION: Although underexpansion in the absence of severe calcium (<180°) is uncommon, mid-LAD lesions with NR and large and thick eccentric calcium were associated with underexpansion.

Optical coherence tomography: evaluating the effects of stent boost subtract imaging on stent underexpansion in STEMI patients.

BACKGROUND: To evaluate the effect of stent boost subtract (SBS) imaging on stent underexpansion during percutaneous coronary intervention (PCI) in patients with acute ST-segment elevation myocardial infarction (STEMI) by optical coherence tomography (OCT). METHODS: One hundred thirty-eight STEMI patients who underwent drug-eluting stent (DES) implantation were prospectively recruited and divided into the SBS group (69 cases) and the CAG group (69 cases) according to whether SBS was used to guide PCI. Finally, OCT was performed on all enrolled patients, and the OCT results were used as the gold standard to evaluate the impact of standard SBS technology on stent underexpansion immediately after DES implantation. RESULTS: SBS identified 51 patients (24%) with stent underexpansion while OCT identified 56 patients (27.2%). SBS has a sensitivity of 80%, a specificity of 96%, a positive predictive value of 88%, and a negative predictive value of 93% for identifying stent underexpansion. CONCLUSION: Compared with OCT, SBS technology is a rapid stent imaging evaluation method that can accurately quantify the stent expansion level and is time-saving and economical.

Successful double-layer metal stents rotational ablation under 2-dimensional and 3-dimensional optical coherence tomography guidance: a case report.

BACKGROUND: Stent ablation with rotational atherectomy has been considered a bail-out strategy for the treatment of severe stent underexpansion. Only a few reports have yet shown rotational ablation for double-layer metal struts. CASE PRESENTATION: We present a case of 80-year-old female patient presented to our hospital because of worsening effort angina. Coronary angiography revealed severe in-stent restenosis in the proximal left anterior descending artery. Optical coherence tomography (OCT) examinations found that severe stenosis occurred at the overlap region with 2-layer underexpanded stents and circumferential calcification beneath them. Under the guidance of 2-dimensional (2D) and 3-dimensional (3D) OCT, we successfully performed percutaneous coronary intervention (PCI) of this lesion after adequate stent ablation, high-pressure balloon dilatation, and subsequent everolimus-eluting stent implantation. The patient recovered well uneventfully and discharged from hospital 7 days later. No restenosis occurred after 12 months. CONCLUSIONS: We report a very rare case of in-stent restenosis due to double-layer underexpanded stents. The entire percutaneous coronary intervention procedure was performed step by step under the guidance of high-resolution OCT. Our findings highlight the specific value of 2D and 3D OCT guidance in double-layer stents rotational ablation.

Optical Coherence Tomography-Based Modeling of Stent Deployment in Heavily Calcified Coronary Lesion.

In this work, a heavily calcified coronary artery model was reconstructed from optical coherence tomography (OCT) images to investigate the impact of calcification characteristics on stenting outcomes. The calcification was quantified at various cross sections in terms of angle, maximum thickness, and area. The stent deployment procedure, including the crimping, expansion, and recoil, was implemented. The influence of calcification characteristics on stent expansion, malapposition, and lesion mechanics was characterized. Results have shown that the minimal lumen area following stenting occurred at the cross section with the greatest calcification angle. The calcification angle constricted the stretchability of the lesion and thus resulted in a small lumen area. The maximum principal strain and von Mises stress distribution patterns in both the fibrotic tissue and artery were consistent with the calcification profiles. The radially projected region of the calcification tends to have less strain and stress. The peak strain and stress of the fibrotic tissue occurred near the interface with the calcification. It is also the region with a high risk of tissue dissection and strut malapposition. In addition, the superficial calcification with a large angle aggregated the malapposition at the middle of the calcification arc. These detailed mechanistic quantifications could be used to provide a fundamental understanding of the role of calcification in stent expansions, as well as to exploit their potential for enhanced pre- and post-stenting strategies.

Impact of Calcium Quantifications on Stent Expansions.

Severely calcified plaque is of great concern when planning and implementing a stenting intervention. In this work, computational models were developed to investigate the influence of calcium characteristics on stenting outcomes. The commonly used clinical measurements of calcium (i.e., the arc angle, maximum thickness, length, and volume) were varied to estimate stenting outcomes in terms of lumen gain, stent underexpansion, strut malapposition, and stress or strain distributions of the stenotic lesion. Results have shown that stenting outcomes were most sensitive to the arc angle of the calcium. A thick calcium with a large arc angle resulted in poor stenting outcomes, such as severe stent underexpansion, D-shaped lumen, increased strut malapposition, and large stresses or strains in the plaque. This was attributed to the circumferential stretch of the tissue. Specifically, the noncalcium component was stretched significantly more than the calcium. The circumferential stretch ratios of calcium and noncalcium component were approximately 1.44 and 2.35, respectively, regardless of calcium characteristics. In addition, the peak stress or strain within the artery and noncalcium component of the plaque occurred at the area adjacent to calcium edges (i.e., the interface between the calcium and the noncalcium component) coincident with the location of peak malapposition. It is worth noting that calcium played a protective role for the artery underneath, which was at the expense of the overstretch and stress concentrations in the other portion of the artery. These detailed mechanistic quantifications could be used to provide a fundamental understanding of the impact of calcium quantifications on stent expansions, as well as to exploit their potential for a better preclinical strategy.

A Case of Stent Under-Expansion due to Calcified Plaque Treated with Shockwave Lithoplasty.

We report the case of a stent under-expansion due to heavily calcified plaque treated with the shockwave lithoplasty system. A 77-year-old woman underwent coronary angiography, and intravascular ultrasound revealed stent under-expansion due to calcified plaque. Shockwave lithoplasty balloon was used to disrupt calcium deposits around the stent, thereby allowing a correct stent expansion with an excellent angiographic and intravascular ultrasound result.

Safety and efficacy of rotational atherectomy for the treatment of undilatable underexpanded stents implanted in calcific lesions.

OBJECTIVES: Coronary stent underexpansion is a known risk factor for in-stent restenosis and stent thrombosis. There are limited options once noncompliant balloons have failed to achieve optimal stent expansion. Excimer Laser Coronary Angioplasty with contrast medium injection is one possibility, but not readily available. Rotational atherectomy is an alternative, and has been described in case reports, but concerns exist regarding safety. METHODS: All consecutive patients undergoing rotational atherectomy for symptomatic in-stent restenosis due to stent underexpansion resistant to noncompliant balloon postdilatation between January 2005 and December 2015 were analysed. RESULTS: A total of 16 patients underwent treatment during the study period and the procedure was successful in 14 cases (87.5%). The mean postprocedural minimal lumen diameter increased by 2.3 ± 0.8 mm and percentage diameter stenosis decreased from 82.17% ± 17.2% to 11.9% ± 9.1%. Intraprocedural complications occurred in two patients (burr entrapment successfully managed percutaneously and periprocedural myocardial infarction). At 1-year follow-up, the incidence of target lesion revascularisation was 13.3% (2 out of 15 patients), and one patient died from noncardiac death. CONCLUSION: In this small series of underexpanded stents, rotational atherectomy was an effective treatment for resistant stent underexpansion with acceptable outcomes. © 2016 Wiley Periodicals, Inc.

Excimer laser in management of underexpansion of a newly deployed coronary stent.

We report the successful management of underexpansion of a newly deployed coronary stent refractory to balloon dilatations. Direct stenting was performed for a lesion in the mid left anterior descending artery (without angiographically apparent heavy coronary calcification). The stent remained underexpanded despite repeated balloon dilatations including with high-pressure inflations. Subsequently, an excimer laser catheter was used in an attempt to vaporize the plaque by the accoustomechanical effect of the rapidly exploding bubbles. The overall angiographic result was good after further balloon dilatation with ordinary pressure and full stent expansion was achieved. Management of underexpansion of a newly deployed stent is a potential indication of laser angioplasty.

3D Stent Reconstruction Using CMCT: A Novel Method to Assess Stent Expansion.

Stent underexpansion in calcified coronary stenosis is an important predictor of major short- and long-term adverse cardiovascular events. In this case, we describe a novel method for assessing stent expansion using 3-dimensional stent reconstruction with C-arm motion compensated computed tomography.

A Systematic Review and Meta-Analysis Including 354 Patients from 13 Studies of Intravascular Lithotripsy for the Treatment of Underexpanded Coronary Stents.

Calcified coronary plaque (CCP) represents a challenging scenario for interventional cardiologists. Stent underexpansion (SU), often associated with CCP, can predispose to stent thrombosis and in-stent restenosis. To date, SU with heavily CCP can be addressed using very high-/high-pressure noncompliant balloons, off-label rotational atherectomy/orbital atherectomy, excimer laser atherectomy, and intravascular lithotripsy (IVL). In this meta-analysis, we investigated the success rate of IVL for the treatment of SU because of CCP. Studies and case-based experiences reporting on the use of IVL strategy for treatment of SU were included. The primary end point was IVL strategy success, defined as the adequate expansion of the underexpanded stent. A metanalysis was performed for the main focuses to calculate the proportions of procedural success rates with corresponding 95% confidence intervals (CIs). Random-effects models weighted by inverse variance were used because of clinical heterogeneity. This meta-analysis included 13 studies with 354 patients. The mean age was 71.3 years (95% CI 64.9 to 73.1), and 77% (95% CI 71.2% to 82.4%) were male. The mean follow-up time was 2.6 months (95% CI 1 to 15.3). Strategy success was seen in 88.7% (95% CI 82.3 to 95.1) of patients. The mean minimal stent area was reported in 6 studies, the pre-IVL value was 3.4 mm2 (95% CI 3 to 3.8), and the post-IVL value was 6.9 mm2 (95% CI 6.5 to 7.4). The mean diameter stenosis (percentage) was reported in 7 studies, the pre-IVL value was 69.4% (95% CI 60.7 to 78.2), and the post-IVL value was 14.6% (95% CI 11.1 to 18). The rate of intraprocedural complications was 1.6% (95% CI 0.3 to 2.9). In conclusion, the "stent-through" IVL plaque modification technique is a safe tool to treat SU caused by CCP, with a high success rate and a very low incidence of complications.

Combination of Laser Atherectomy and Super High-pressure Non-compliant Balloon to Treat Stent Under-expansion in Cases of Failed Interventional Options.

Patients with calcified, fibrotic native coronary vessels with prior suboptimal stenting outcomes are at major risk of stent thrombosis and could face serious consequences if untreated. In cases of multiple layers of under-expanded stents, the risk is multiplied. If conventional balloon post-dilatation is unsuccessful after stent implantation without proper lesion preparation, few interventional options remain. The authors report on a patient with prior numerous right coronary unsuccessful coronary interventions resulting in partially crushed multiple layers of stent material with critical lumen narrowing caused by stent under-expansion. Balloon angioplasty and stent rotational atherectomy (ROTA) had been attempted to overcome stent under-expansion but were unsuccessful. The authors investigated a new combination therapy of laser atherectomy (ELCA) and super high-pressure balloon (OPN non-compliant balloon) to treat single or multiple layers of stent with severe under-expansion due to fibrotic, calcified tissue surrounding the under-expanded stent structure.

Intravascular Lithotripsy for the Treatment of Stent Underexpansion: The Multicenter IVL-DRAGON Registry.

Background: Whereas the efficacy and safety of intravascular lithotripsy (IVL) have been confirmed in de novo calcified coronary lesions, little is known about its utility in treating stent underexpansion. This study aimed to investigate the impact of IVL in treating stent underexpansion. Methods and Results: Consecutive patients with stent underexpansion treated with IVL entered the multicenter IVL-Dragon Registry. The procedural success (primary efficacy endpoint) was defined as a relative stent expansion >80%. Thirty days device-oriented composite endpoint (DOCE) (defined as a composite of cardiac death, target lesion revascularization, or target vessel myocardial infarction) was the secondary endpoint. A total of 62 patients were enrolled. The primary efficacy endpoint was achieved in 72.6% of patients. Both stent underexpansion 58.5% (47.5−69.7) vs. 11.4% (5.8−20.7), p < 0.001, and the stenotic area 82.6% (72.4−90.8) vs. 21.5% (11.1−37.2), p < 0.001, measured by quantitative coronary angiography improved significantly after IVL. Intravascular imaging confirmed increased stent expansion following IVL from 37.5% (16.0−66.0) to 86.0% (69.2−90.7), p < 0.001, by optical coherence tomography and from 57.0% (31.5−77.2) to 89.0% (85.0−92.0), p = 0.002, by intravascular ultrasound. Secondary endpoint occurred in one (1.6%) patient caused by cardiac death. There was no target lesion revascularization or target vessel myocardial infarction during the 30-day follow-up. Conclusions: In this real-life, largest-to-date analysis of IVL use to manage underexpanded stent, IVL proved to be an effective and safe method for facilitating stent expansion and increasing luminal gain.

Bailout Intravascular Lithotripsy for the Treatment of Acutely Underexpanded Stents in Heavily Calcified Coronary Lesions: A Case Series.

Stent underexpansion is a common problem in heavily calcified coronary lesions treated with percutaneous coronary intervention, and has been associated with in-stent restenosis, stent thrombosis and, subsequently, poor clinical outcomes. Adequate preparation of heavily calcified coronary lesions (e.g. using non-compliant balloons, cutting/scoring balloons, rotational/orbital atherectomy or intravascular lithotripsy) prior to stent implantation is essential in preventing stent underexpansion. However, in certain cases the deployed stent may remain underexpanded despite extensive lesion preparation. To date, no consensus exists on how to treat stent underexpansion in this scenario. We present a cases series in which post-stenting intravascular lithotripsy was performed to treat acute stent underexpansion in heavily calcified lesions, describing the technical aspects, angiographic results as well as clinical outcomes at mid-term follow-up.

Intracoronary Lithotripsy in Calcified Coronary Lesions: A Multicenter Observational Study.

OBJECTIVES: The aim of this study was to evaluate the feasibility, effectiveness, and safety of coronary intravascular lithotripsy (IVL; Shockwave Medical) in the treatment of severe coronary artery calcification (CAC) in a real-world setting. BACKGROUND: Severe CAC can be an arduous obstacle in interventional cardiology, often leading to suboptimal results of percutaneous coronary interventions (PCI). Coronary IVL is a novel technique that modulates severe CAC, thereby facilitating stent implantation. METHODS AND RESULTS: In this multicenter observational study, data from 134 IVL procedures in 5 Belgian hospitals were prospectively obtained. Successful delivery of the IVL catheter was achieved in all cases but 1 (99.3%). The primary endpoint was final overall procedural success, which was obtained in 88.1% of cases, an aggregate of 92.6% in de novo lesions and 77.5% in stent underexpansion or in-stent restenosis (ISR). IVL therapy effect was considered successful by the operators in 94% of cases, with 68.7% achieving optimal and 25.3% achieving suboptimal results. The 1-month major adverse cardiovascular event rate was 3%, including 2 cardiovascular deaths (1 in-stent thrombosis and 1 coronary artery perforation). CONCLUSIONS: This real-world experience suggests that Shockwave IVL is a feasible, effective, and safe technique for the treatment of heavily calcified coronary lesions.

Excimer laser technology in percutaneous coronary interventions: Cardiovascular laser society's position paper.

Excimer Laser Coronary Atherectomy (ELCA) is a well-established therapy that emerged for the treatment of peripheral vascular atherosclerosis in the late 1980s, at a time when catheters and materials were rudimentary and associated with the most serious complications. Refinements in catheter technology and the introduction of improved laser techniques have led to their effective use for the treatment of a wide spectrum of complex coronary lesions, such as thrombotic lesions, severe calcific lesions, non-crossable or non-expandable lesions, chronic occlusions, and stent under-expansion. The gradual introduction of high-energy strategies combined with the contrast infusion technique has enabled us to treat an increasing number of complex cases with a low rate of periprocedural complications. Currently, the use of the ELCA has also been demonstrated to be effective in acute coronary syndrome (ACS), especially in the context of large thrombotic lesions.

A novel optical coherence tomography­based calcium scoring system can predict the stent expansion of moderate and severe calcified lesions.

Coronary calcified lesions can exert serious effects on stent expansion. A calcium scoring system, based on optical coherence tomography (OCT), has been previously developed to identify relatively mild calcified lesions that would benefit from plaque modification procedures. Therefore, the present study aimed to establish a novel OCT-based scoring system to predict the stent expansion of moderate and severe calcified lesions. A total of 33 patients who underwent percutaneous coronary intervention (PCI; 34 calcified lesions were observed using coronary angiography) were retrospectively included in the present study. Coronary angiography and OCT images were subsequently reviewed and analyzed. Furthermore, a calcium scoring system was developed based on the results of multivariate analysis before the optimal threshold for the prediction of stent underexpansion in patients with moderate and severe calcified lesions was determined. The mean age of the patients was 67±10 years. The present analysis demonstrated that the final post-PCI median stent expansion was 70.74%, where stent underexpansion (defined as stent expansion <80%) was observed in 23 lesions. The mean maximum calcium arc, length and thickness, which were assessed using OCT, were found to be 230˚, 25.10 mm and 1.18 mm, respectively. A multivariate logistic regression model demonstrated that age and the maximum calcium arc were independent predictors of stent underexpansion. A novel calcium scoring system was thereafter established using the following formula: (0.16 x age) + (0.03 x maximum calcium arc) according to the ß-coefficients in the multivariate analysis, with the optimal cut-off value for the prediction of stent underexpansion being 16.87. Receiver operating characteristic curve analysis demonstrated that this novel scoring system yielded a larger area under the curve value compared with that from a previous study's scoring system. Therefore, in conclusion, since the calcium scoring system of the present study based on age and the maximum calcium arc obtained from OCT was specifically developed in the subjects with moderate and severe calcified lesions, it may be more accurate in predicting the risk of stent underexpansion in these patients.

Structural analysis of regional transcatheter aortic valve underexpansion and its implications for subclinical leaflet thrombosis.

Subclinical leaflet thrombosis has been increasingly recognized following transcatheter aortic valve replacement (TAVR). Determining the risk factors is vital in preventing clinical leaflet thrombosis and ensuring long-term value durability. Clinical data have indicated that regional stent under-expansion of transcatheter aortic valves (TAVs), particularly self-expanding devices, may be associated with an increased risk of subclinical leaflet thrombosis. This study aimed to determine the effects of regional TAV frame under-expansion on leaflet kinematics, leaflet structural characteristics, and explore its impact on the likelihood of leaflet thrombosis. In this study, mild and moderate regional frame under-expansion of a 26-mm CoreValve were examined using experimental testing and computational simulations. The results indicated that regional TAV frame under-expansion impairs leaflet kinematics and reduces the range of motion in leaflets with an angle less than 120°. The reduced range of motion can increase blood stasis on the surface of the TAV leaflets. The results also demonstrated that regional frame under-expansion induced localized high-stress regions in the leaflets close to the fixed boundary edge. The increased mechanical stress can lead to accelerated tissue degeneration. The study improves our understanding of the effects of regional stent under-expansion in TAVR. Post-procedural balloon dilatation of self-expanding TAVs can potentially be advantageous in reducing leaflet distortion and normalizing leaflet stress distribution. Large-scale, prospective, and well-controlled studies are needed to further investigate regional TAV frame under-expansion effects on subclinical leaflet thrombosis and long-term valve durability.

Prediction of Coronary Stent Underexpansion by Pre-Procedural Intravascular Ultrasound-Based Deep Learning.

OBJECTIVES: The aim of this study was to develop pre-procedural intravascular ultrasound (IVUS)-based models for predicting the occurrence of stent underexpansion. BACKGROUND: Although post-stenting IVUS has been used to optimize percutaneous coronary intervention, there are no pre-procedural guidelines to estimate the degree of stent expansion and provide preemptive management before stent deployment. METHODS: A total of 618 coronary lesions in 618 patients undergoing percutaneous coronary intervention were randomized into training and test sets in a 5:1 ratio. Following the coregistration of pre- and post-stenting IVUS images, the pre-procedural images and clinical information (stent diameter, length, and inflation pressure; balloon diameter; and maximal balloon pressure) were used to develop a regression model using a convolutional neural network to predict post-stenting stent area. To separate the frames with from those without the occurrence of underexpansion (stent area <5.5 mm2), binary classification models (XGBoost) were developed. RESULTS: Overall, the frequency of stent underexpansion was 15% (5,209 of 34,736 frames). At the frame level, stent areas predicted by the pre-procedural IVUS-based regression model significantly correlated with those measured on post-stenting IVUS (r = 0.802). To predict stent underexpansion, maximal accuracy of 94% (area under the curve = 0.94) was achieved when the convolutional neural network- and mask image-derived features were used for the classification model. At the lesion level, there were significant correlations between predicted and measured minimal stent area (r = 0.832) and between predicted and measured total stent volume (r = 0.958). CONCLUSIONS: Deep-learning algorithms accurately predicted incomplete stent expansion. A data-driven approach may assist clinicians in making treatment decisions to avoid stent underexpansion as a preventable cause of stent failure.

Bail-out intravascular lithotripsy for severe stent underexpansion during primary angioplasty: a case report.

BACKGROUND: Intravascular lithotripsy is safe and effective for the treatment of de novo coronary artery calcifications. Its bail-out use in acute coronary syndrome and for underexpanded stents, although currently off-label, could be the best option when other conventional techniques fail. CASE SUMMARY: A patient with an inferior ST-segment elevation myocardial infarction underwent a primary percutaneous coronary intervention. Stent underexpansion due to a heavily calcified lesion was refractory to high-pressure balloon dilatations. Complete stent expansion was achieved with intravascular lithotripsy, as evidenced by intravascular ultrasound, and no acute complications occurred. DISCUSSION: Treatment strategies for stent underexpansion due to coronary artery calcifications are still debated. High-pressure non-compliant balloon dilatations are rarely sufficient to gain a complete stent expansion. Rotational and orbital atherectomy are contraindicated in presence of a thrombus. Given the possible risks of stent damages, intravascular lithotripsy is currently not indicated in acutely deployed stents but could be the best bail-out technique for otherwise undilatable stents due to severely calcified plaques.

Pericardial Tamponade Caused by Rotational Atherectomy Ablation Grinding Through a Barrier Stent Protruding From the Diagonal Artery: A Case Report.

Rotational atherectomy (RA) has been described in case reports to be effective in ablating under-expanded stents. We present a case of calcified bifurcation lesion percutaneous coronary intervention (PCI), in which the branch stent protruding into main branch blocked the balloon getting through, and the following RA led to pericardial tamponade. The first stent was deployed from the proximal of left anterior descending artery (LAD) to the proximal of diagonal for an 80-year-old man who suffered from non-ST-elevation myocardial infarction to make a Culotte dual stent PCI. The operator failed to make balloon get through the struts protruding into LAD lumen anyway. After RA drill through the LAD lumen, it showed an excellent angiographic outcome. Stent deployment in LAD was successful, but pericardial tamponade occurred in a short time. After pericardiocentesis was performed under fluoroscopic guidance, the patient was uneventful. After 1 year, the follow-up coronary computed tomography (CT) angiography showed no in-stent restenosis, stent fracture or disrupted struts protruding outside of the vessel's outline of LAD and the first diagonal (D1). This case shows stents' RA could be dangerous in grinding across the stents' lateral hole in an unsymmetrical lumen. Although RA could be a useful remedy in the situation of under-expansion of implanted stents, the debulking should be performed for longitudinal stent ablation and cautiously performed for bifurcation lesion in which the protruding stents from side branch were unsymmetrically blocking the path.