Stent Expansion Index Research Articles

Computed tomography for prediction of stent underexpansion after percutaneous recanalization of calcified coronary chronic total occlusions

Abstract Background Coronary calcifications are the leading cause of stent underexpansion after percutaneous coronary intervention (PCI) and are commonly encountered in chronic total occlusions (CTO). Coronary computed tomography angiography (CCTA) is uniquely suited for pre-procedural assessment of coronary calcifications. Recently quantitative CCTA, providing exact volumes of each plaque component, has shown additional value in future risk assessment compared with conventional qualitative CCTA. Purpose The aim of this study was to evaluate whether CCTA predicts intravascular ultrasound (IVUS)-defined suboptimal stent expansion following percutaneous recanalization of calcified CTO lesions. Methods We retrospectively identified consecutive patients with a CCTA performed within 6-months prior to successful PCI of a calcified CTO (defined as calcification within the target lesion on CCTA). All patients had final IVUS of implanted stents (Figure 1). Patients requiring atherectomy were excluded. The primary outcome was IVUS-derived stent expansion index (SEI), defined as stent area divided by vessel area (both measured at the site of maximum calcium). SEI<0.4 indicated suboptimal stent expansion. The site of maximum calcium was a cross-section with greatest calcium arc on pre-stent IVUS within the target lesion. CCTA calcium analysis was performed by a researcher blinded to the IVUS and angiography results. Measurements included total-, vessel-, and lesion-specific calcium score (CAC), total calcium length, maximum calcium thickness and maximum CT calcium attenuation at the target lesion defined as occlusion site and adjacent severely diseased segments. Calcium quantification was performed using a semi-automated software to obtain volumes and burdens of calcified and non-calcified plaque components within the target lesion. Results The cohort included 43 patients (age 64.9±10.0 years, 88% males) with 43 CTO lesions. Mean final stent area at maximum calcium by IVUS was 8.2±2.1mm². Mean SEI was 0.47±0.1, and suboptimal SEI of <0.4 was found in 10 (23.3%) lesions. Lesions with suboptimal stent expansion (SEI<0.4) were characterized by numerically higher total-, vessel- and lesion-specific CAC, higher maximum calcium attenuation, greater calcium length and remodeling index compared with patients with optimal stent expansion (Table 1). However, only calcified plaque volume (105 [IQR 27-271] vs. 29 [4-96]mm³, P=0.02) and calcified plaque burden (16 [7-24] vs. 6 [1-10]%, P=0.03) were significantly greater in lesions with suboptimal stent expansion compared with lesions with optimal stent expansion, respectively. Calcified plaque volume ≥51 mm³ within the target lesion predicted suboptimal stent expansion with 70% sensitivity and 62.5% specificity (AUC 0.74). Conclusion CCTA-derived calcium volume identifies CTO lesions at greater risk of stent underexpansion. Such lesions require more aggressive plaque modification prior to stent implantation.

Volumetric Stent Expansion Index to Assess Tapering Lesions Using Intravascular Ultrasound and Its Clinical Outcomes.

This study aimed to assess the clinical significance of generating a volumetric stent expansion index for tapering lesions through intravascular ultrasound (IVUS). Previous IVUS studies have used minimal stent area (MSA) to predict adverse outcomes. A total of 251 tapering lesions were treated in this study via IVUS guidance in 232 patients. Eight stent expansion indices were evaluated to determine the association of these indices with device-oriented clinical endpoints (DoCEs) after two-year follow-ups. These were the ILUMIEN III and IV standards, the ULTIMATE (Intravascular Ultrasound Guided Drug Eluting Stents Implantation in "All-Comers" Coronary Lesions) standard, the IVUS-XPL (Impact of Intravascular Ultrasound Guidance on the Outcomes of Xience Prime Stents in Long Lesions) standard, the minimal volumetric expansion index (MVEI) using the Huo-Kassab or linear model, the MSA/vessel area at the MSA cross-section, the traditional stent expansion (MSA/mean proximal and distal reference lumen cross-sectional area), and MSA. The MVEI was the only stent expansion index that correlated significantly with the two-year DoCEs (hazard ratio [HR], 1.91; 95% confidence interval [CI]: 1.16-3.96; p = 0.028). In the ROC analysis, the area under the curve for the MVEI was 0.71 (p = 0.002), with an optimal cut-off value of 62.2 for predicting the DoCEs. This is the first study to use IVUS for tapering lesions and demonstrate that the MVEI is an independent predictor of two-year DoCEs.

Preprocedural physiological assessment of coronary disease patterns to predict haemodynamic outcomes post-PCI.

Even with intracoronary imaging-guided stent optimisation, suboptimal haemodynamic outcomes post-percutaneous coronary intervention (PCI) can be related to residual lesions in non-stented segments. Preprocedural assessment of pathophysiological coronary artery disease (CAD) patterns could help predict the physiological response to PCI. The aim of this study was to assess the relationship between preprocedural pathophysiological haemodynamic patterns and intracoronary imaging findings, as well as their association with physiological outcomes immediately post-PCI. Data from 206 patients with chronic coronary syndrome enrolled in the ASET-JAPAN study were analysed. Pathophysiological CAD patterns were characterised using Murray law-based quantitative flow ratio (μQFR)-derived indices acquired from pre-PCI angiograms. The diffuseness of CAD was defined by the pullback pressure gradient (PPG) index. Intracoronary imaging in stented segments after stent optimisation was also analysed. In the multivariable analysis, diffuse disease - defined by the pre-PCI μQFR-PPG index - was an independent factor for predicting a post-PCI μQFR <0.91 (per 0.1 decrease of PPG index, odds ratio 1.57, 95% confidence interval: 1.07-2.34; p=0.022), whereas the stent expansion index (EI) was not associated with a suboptimal post-PCI μQFR. Among vessels with an EI ≥80% and post-PCI μQFR <0.91, 84.0% of those vessels had a diffuse pattern preprocedure. There was no significant difference in EI between vessels with diffuse disease and those with focal disease. The average plaque burden in the stented segment was significantly larger in vessels with a preprocedural diffuse CAD pattern. A physiological diffuse pattern preprocedure was an independent factor in predicting unfavourable immediate haemodynamic outcomes post-PCI, even after stent optimisation using intracoronary imaging. Preprocedural assessment of CAD patterns could identify patients who are likely to exhibit superior immediate haemodynamic outcomes following PCI.

Predictors of residual lipid content detected by near-infrared spectroscopy after elective stenting in patients with chronic coronary syndrome

Abstract Backgrounds Residual lipid-rich plaque (LRP) in stented segments assessed by near-infrared spectroscopy (NIRS) immediately after percutaneous coronary intervention (PCI) is reportedly associated with target lesion failure. However, morphological determinants of residual LRP after elective PCI remains unknown. Purpose This single-center observational study aimed to explore morphological and procedural predictors of residual LRP after electing PCI. Methods We investigated 340 consecutive patients who underwent elective NIRS-intravascular ultrasound-guided PCI for de novo coronary lesions. Lesions requiring balloon dilatation or debulking before NIRS imaging, requiring ≥2 remote stent deployment in the vessel, being treated with drug-coated balloon, and having insufficient NIRS imaging were excluded. Maximum lipid core burden index in 4mm (maxLCBI4mm) in culprit segment both before and after PCI was assessed by NIRS. Residual LRP was defined as post-PCI maxLCBI4mm in stented lesions &amp;gt;200. Baseline clinical and morphological findings were compared between lesions with versus without residual LRP. Multivariable logistic regression analysis was performed to determine predictors of residual LRP. Results A total of 236 de novo lesions in 223 patients were included in the final dataset. After PCI, residual LRP was observed in 69 (29%) lesions. Patients with residual LRP tended to be older than those without residual LRP. Pre-PCI maxLCBI4mm in culprit lesions, plaque burden, and remodeling index were greater in lesions with residual LRP. Post-PCI minimum stent area and expansion index tended to be smaller in lesions with residual LRP. In a multivariable analysis, pre-PCI maxLCBI4mm (per 10, adjusted odds ratio [OR]:1.04; 95% confidence interval [CI]: 1.02 to 1.05; p&amp;lt;0.01) and stent expansion index (per 10%, adjusted OR: 0.80; 95%CI: 0.64 to 0.99; p=0.047) were independently predictive of residual LRP. Conclusions In patients undergoing elective PCI, greater pre-PCI maxLCBI4mm and smaller stent expansion were associated with post-PCI residual LRP.

Prediction of stent under-expansion in calcified coronary arteries using machine learning on intravascular optical coherence tomography images

It can be difficult/impossible to fully expand a coronary artery stent in a heavily calcified coronary artery lesion. Under-expanded stents are linked to later complications. Here we used machine/deep learning to analyze calcifications in pre-stent intravascular optical coherence tomography (IVOCT) images and predicted the success of vessel expansion. Pre- and post-stent IVOCT image data were obtained from 110 coronary lesions. Lumen and calcifications in pre-stent images were segmented using deep learning, and lesion features were extracted. We analyzed stent expansion along the lesion, enabling frame, segmental, and whole-lesion analyses. We trained regression models to predict the post-stent lumen area and then computed the stent expansion index (SEI). Best performance (root-mean-square-error = 0.04 ± 0.02 mm2, r = 0.94 ± 0.04, p < 0.0001) was achieved when we used features from both lumen and calcification to train a Gaussian regression model for segmental analysis of 31 frames in length. Stents with minimum SEI > 80% were classified as “well-expanded;” others were “under-expanded.” Under-expansion classification results (e.g., AUC = 0.85 ± 0.02) were significantly improved over a previous, simple calculation, as well as other machine learning solutions. Promising results suggest that such methods can identify lesions at risk of under-expansion that would be candidates for intervention lesion preparation (e.g., atherectomy).

TCT-600 Evaluation of the Stent Parameters Post-PCI (Minimum Stent Area, Stent Expansion Index, and Stent Gradient) and its Relation to Post-PCI Physiological Outcomes Assessed by Intravascular Imaging-Based Ultrasonic Flow Ratio and Optical Flow Ratio: Insights From the ASET JAPAN Trial

TCT-600 Evaluation of the Stent Parameters Post-PCI (Minimum Stent Area, Stent Expansion Index, and Stent Gradient) and its Relation to Post-PCI Physiological Outcomes Assessed by Intravascular Imaging-Based Ultrasonic Flow Ratio and Optical Flow Ratio: Insights From the ASET JAPAN Trial

Impact of Stent Expansion Index on Stent Failure After Left Main Stenting

Impact of the stent expansion index (EXPI) in percutaneous coronary intervention (PCI) for unprotected left main distal bifurcation lesions (ULMD) has been not completely understood especially in current-generation drug-eluting stent (cDES) era. We evaluated the impact of EXPI on clinical outcomes after PCI with cDES for ULMD. We identified 342 patients treated with cDES for ULMD and postintervention intravascular ultrasound between January 2010 and December 2019. In this study, the ratio of minimum stent area (MSA) to reference vessel area at the MSA site was adopted to assess the stent expansion. We defined the patients with the first and second tertile as low-intermediate EXPI group and those with the third tertile as high EXPI group and compared the clinical outcomes between both groups. The primary end point was target lesion failure (TLF). TLF was defined as a composite of cardiac death, target lesion revascularization (TLR) ,and myocardial infarction. The MSA was located in the ostium of left anterior descending coronary artery in most cases (318 of 342 patients; 93.0%). There were no significant differences between both groups in the baseline clinical, lesion, and procedural characteristics. The high EXPI group had lower TLF rate than the low-intermediate EXPI group (10.2% vs 19.9%, log-rank p=0.033). In conclusion, this is the first report that the higher ratio of MSA to reference vessel area at the MSA site, which was defined as stent EXPI, was associated with more favorable clinical outcomes after PCI for ULMD.

Stent Optimization Using Optical Coherence Tomography and Its Prognostic Implications After Percutaneous Coronary Intervention.

BackgroundStent underexpansion has been known to be associated with worse outcomes. We sought to define optical coherence tomography assessed optimal stent expansion index (SEI), which associates with lower incidence of follow‐up major adverse cardiac events (MACEs).Methods and ResultsA total of 315 patients (involving 370 lesions) who underwent optical coherence tomography–aided coronary stenting were retrospectively included. SEI was calculated separately for equal halves of each stented segment using minimum stent area/mean reference lumen area ([proximal reference area+distal reference area]/2). The smaller of the 2 was considered to be the SEI of that case. Follow‐up MACE was defined as a composite of all‐cause death, myocardial infarction, stent thrombosis, and target lesion revascularization. Average minimum stent area was 6.02 (interquartile range, 4.65–7.92) mm2, while SEI was 0.79 (interquartile range, 0.71–0.86). Forty‐seven (12.7%) incidences of MACE were recorded for 370 included lesions during a median follow‐up duration of 557 (interquartile range, 323–1103) days. Receiver operating characteristic curve analysis identified 0.85 as the best SEI cutoff (<0.85) to predict follow‐up MACE (area under the curve, 0.60; sensitivity, 0.85; specificity, 0.34). MACE was observed in 40 of 260 (15.4%) lesions with SEI <0.85 and in 7 of 110 (6.4%) lesions with SEI ≥0.85 (P=0.02). Least absolute shrinkage and selection operator regression identified SEI <0.85 (odds ratio, 3.55; 95% CI, 1.40–9.05; P<0.01) and coronary calcification (odds ratio, 2.47; 95% CI, 1.00–6.10; P=0.05) as independent predictors of follow‐up MACE.ConclusionsThe present study identified SEI <0.85, associated with increased incidence of MACE, as the optimal cutoff in daily practice. Along with suboptimal SEI (<0.85), coronary calcification was also found to be a significant predictor of follow‐up MACE.

Assessment of stent optimization in clinical practice using optical coherence tomography: a multicentric observational study

Abstract Background Stent under-expansion obtained at the time of percutaneous coronary intervention (PCI) has been shown to be associated with worse outcomes. Purpose We sought to define OCT assessed optimal stent expansion index which associates with lower incidence of major adverse cardiac events (MACE) during follow-up in a sample of patients stented at five high volume centers of central Europe. Methods We analyzed 370 lesions stented during the period between 2012 and 2018, with their final procedural results imaged using optical coherence tomography (OCT). QIvus Research Edition v3.1 (Medis, Leiden, NL) was used for OCT analysis. The stented segment was split in two equal halves. Stent expansion index (SEI) was calculated for both halves separately by dividing minimum stent area by the mean reference lumen area [(proximal reference area + distal reference area)/2]. Smallest of the two prevailed as the SEI of that case. MACE during post-PCI follow-up was defined as composite of all-cause death, myocardial infarction, stent thrombosis and target lesion revascularization. Data is expressed as mean±SD or median (Interquartile range). Incidence of subsequent MACE is expressed as crude rates (%). Results A total of 316 cases (370 lesions), aged 64.6±11.7 years were included for OCT analysis. Of them, 78.8% were males, 22.8% were diabetics, 75.9% were hypertensives while 35.1% had family history of coronary artery disease. 38.0% of the cases had acute coronary syndrome at presentation. 62.4% of treated lesions were complex (Type B2/C). A mean of 1.11±0.34 stents/scaffolds were implanted per treated lesion. Analyzed segment length was 20.4 (15.17, 27.0) mm. Minimal stent area (MSA) in the overall stented segment was 6.02 mm2 (4.65, 7.93). Median stent expansion index (minimum) was 0.79 (0.71, 0.86). Median follow-up duration was 557 days (326, 1,096). 47 lesions (12.7%) suffered MACE during follow-up. Receiver operating characteristic (ROC) curve analysis using Youden's rule identified 0.84 as SEI cut-off powered to predict post-PCI MACE (AUC= 0.60, sensitivity= 0.85, specificity= 0.34). MACE was observed in 38/249 (15.3%) of lesions with SEI≤0.84 and in 9/121 (7.4%) of lesions with SEI&amp;gt;0.84 (p=0.03). Univariate regression analysis of MACE revealed significant association with SEI≤0.84 (OR=2.2, 95% CI=1.1–4.8, p=0.04) Adaptive Lasso regression identified SEI≤0.84 (OR=4.1, 95% CI=1.3–12.6, p=0.02) and coronary calcification at baseline (OR=2.7, 95% CI=1.1–6.6, p=0.03) as independent predictors of MACE during follow-up. Kaplan-meier curve for MACE free survival with optimal SEI (n=121) and sub-optimal SEI (n=249) subgroups using SEI cut-off of 0.84, however showed modest separation (p=0.11). Conclusions The present study identified SEI&amp;gt;0.84 associated with lower incidence of MACE as optimal cut-off in daily practice. Along with SEI of ≤0.84, coronary calcification was also significantly associated with MACE during post PCI follow-up. Funding Acknowledgement Type of funding sources: None.

Super high-pressure balloon versus scoring balloon to prepare severely calcified coronary lesions: the ISAR-CALC randomised trial.

The comparative efficacy of balloon-based techniques to prepare severely calcified coronary lesions before stenting remains poorly studied. We sought to compare stent expansion following preparation of severely calcified coronary lesions with either a super high-pressure balloon or a scoring balloon. In this randomised, open-label trial, patients with severely calcified coronary lesions were enrolled at five centres in Germany and Switzerland. After unsuccessful lesion preparation with a standard non-compliant balloon (<30% reduction of baseline diameter stenosis), participants were randomised to predilation with either a super high-pressure balloon or a scoring balloon before drug-eluting stent (DES) implantation. The primary endpoint of the study was stent expansion index as assessed by optical coherence tomography (OCT). The key secondary endpoints included angiographic, strategy and procedural success. OCT data after DES implantation were available for 70 out of 74 patients (94.6%) enrolled. Lesion preparation with a super high-pressure balloon versus a scoring balloon led to a comparable stent expansion index (0.72±0.12 vs 0.68±0.13; p=0.22). Compared with the scoring balloon, the super high-pressure balloon increased the minimum lumen diameter (2.83±0.34 mm vs 2.65±0.36 mm; p=0.03) and reduced the diameter stenosis (11.6±4.8% vs 14.4±5.6%; p=0.02) without difference in terms of angiographic success (100% vs 97.3%; p>0.99). Strategy success (91.9% vs 83.8%; p=0.48) and procedural success (100% vs 89.2%; p=0.12) were numerically more frequent with the super high-pressure balloon versus the scoring balloon. In patients with severely calcified coronary artery lesions, preparation with a super high-pressure balloon versus a scoring balloon was associated with comparable stent expansion on intravascular imaging and a trend towards improved angiographic performance. Visual summary. A ComparIson of Strategies to PrepAre SeveRely CALCified Coronary Lesions: the ISAR-CALC randomised trial.

Effect of lipoprotein α on coronary stents expansion and its risk factors.

To analyze the effect of hyperlipoproteinemia (α) on immediate expansion after coronary stent implantation guided by intravascular ultrasound (IVUS). A total of 160 patients (175 lesions) with coronary heart disease diagnosed by coronary artery angiography, who were performed percutaneous intervention guided by IVUS in the Department of Cardiology, Third Xiangya Hospital, Central South University, were enrolled retrospectively.According to the concentration of lipoproteina, the patients were divided into 2 groups: a hyperlipoproteinemia (α) group and a control group. Cardiac ejection fraction was measured with echocardiography. Logistic regression was used to analyze the influential factors for hyperlipoproteinemia (α). The target vessel was examined by IVUS to analyze the immediate expansion effect of hyperlipoproteinemia (α) after stent implantation. The mean stent expansion index, lesion length, stent number, stent symmetry index and posterior balloon diameter were (94.73±18.9)%, (52.92±29.1) mm, (2.11±0.85), (83.62±13.07)%, and (9.46±2.00) mm in the hyperlipoproteinemia (α) group, respectively. Compared with the control group, there were significantly difference (all P<0.05). Multivariable regression analysis showed that the decreased creatinine clearance rate was an independent risk factor for hyperlipoproteinemia (α) (P<0.05). Hyperlipoproteinemia (α) appears to be a predictor of stent underexpansion, and the decreased creatinine clearance rate is an independent risk factor for hyperlipoproteinemia (α).

Impact of optical coherence tomography findings on clinical outcomes in ST-segment elevation myocardial infarction patients: a MATRIX (Minimizing Adverse Hemorrhagic Events by Trans-radial Access Site and angioX) OCT sub-study.

To investigate the association of the degree of stent expansion, as assessed by optical coherence tomography (OCT), following stent implantation, and clinical outcomes in ST-segment elevation myocardial infarction (STEMI) patients. STEMI patients from the MATRIX (Minimizing Adverse Haemorrhagic Events by TRansradial Access Site and angioX) OCT study were selected; Clinical outcomes were collected through 1year. Stent expansion index is a minimum stent area (MSA) divided by average lumen area (average of proximal and distal reference lumen area). The following variables were measured: MSA (< 4.5mm2), dissection (> 200µm in width and < 5mm from stent segment), malapposition (> 200µm distance of stent from vessel wall), a thrombus (area > 5% of lumen area) were compared. A total of 151 patients were included; after excluding patients with suboptimal OCT quality, the population with available OCT was classified into 2 groups: under-expanded < 90% (N = 72, 51%) and well-expanded ≥ 90% (N = 67, 49%). In the well-expanded group, a significant number of the proximal vessels had a lumen area < 4.5mm2 (16.1%, p < 0.001) and a greater thrombus burden within stent (56.7%, p = 0.042). The overall 30day and 1year major adverse cardiovascular event (MACE) rates were 5% and 6.1%, respectively. Irrespective of the degree of stent expansion, the OCT findings, in STEMI patients, and the MACE at 30days and one year follow up was low; further, well-expanded stents led to a more significant residual thrombotic burden within the stent but seemed to have insignificant clinical impact. Acknowledged stent optimization criteria, traditionally related to worse outcomes in stable patients, do not seem to be associated with worse outcomes in this STEMI population.

Performing percutaneous coronary interventions with predilatation using non-compliant balloons at high-pressure versus conventional semi-compliant balloons: insights from two randomised studies using optical coherence tomography

IntroductionStent underexpansion is a predictor of in-stent-restenosis and stent thrombosis. Semi-compliant balloons (SCBs) are generally used for lesion preparation. It remains unknown whether routine predilatation using non-compliant balloons (NCBs) improves...

Optical frequency-domain imaging findings to predict good stent expansion after rotational atherectomy for severely calcified coronary lesions.

We aimed to evaluate the optical frequency-domain imaging (OFDI) findings after rotational atherectomy (RA) that predict good stent expansion for severely calcified coronary lesions. Fifty consecutive calcified lesions were subjected to RA under OFDI guidance. We performed OFDI just after RA and stenting. We measured the morphology of calcium after RA, and assessed how these factors influence stent expansion. The stent expansion index was defined as the minimum stent area divided by the average of the proximal and distal reference lumen areas. Minimum thickness of calcification in the intima after RA showed a significant negative correlation with stent expansion (r = - 0.53, P < 0.001), while calcium arc, length, and maximum thickness of calcification in the intima did not. Dissection after RA occurred in 22 lesions (44%), and the stent expansion index was significantly better in dissected lesions than in lesions without dissection (0.96 ± 0.08 vs. 0.82 ± 0.19, P = 0.002). Multiple regression analysis showed that the minimum thickness of calcification in the intima (standardized coefficient: - 0.451, P < 0.001) and dissection formation (standardized coefficient: 0.316, P = 0.011) were predictors of good stent expansion. Minimum of thickness of calcification in the intima and dissection formation were positively associated with good stent expansion after RA. In the clinical setting, achieving these two endpoints should be the aim of RA to ensure good stent expansion.

Optical Coherence Tomography Findings in Patients With Coronary Stent Thrombosis: A Report of the PRESTIGE Consortium (Prevention of Late Stent Thrombosis by an Interdisciplinary Global European Effort).

Stent thrombosis (ST) is a serious complication following coronary stenting. Intravascular optical coherence tomography (OCT) may provide insights into mechanistic processes leading to ST. We performed a prospective, multicenter study to evaluate OCT findings in patients with ST. Consecutive patients presenting with ST were prospectively enrolled in a registry by using a centralized telephone registration system. After angiographic confirmation of ST, OCT imaging of the culprit vessel was performed with frequency domain OCT. Clinical data were collected according to a standardized protocol. OCT acquisitions were analyzed at a core laboratory. Dominant and contributing findings were adjudicated by an imaging adjudication committee. Two hundred thirty-one patients presenting with ST underwent OCT imaging; 14 (6.1%) had image quality precluding further analysis. Of the remaining patients, 62 (28.6%) and 155 (71.4%) presented with early and late/very late ST, respectively. The underlying stent type was a new-generation drug-eluting stent in 50.3%. Mean reference vessel diameter was 2.9±0.6 mm and mean reference vessel area was 6.8±2.6 mm2. Stent underexpansion (stent expansion index <0.8) was observed in 44.4% of patients. The predicted average probability (95% confidence interval) that any frame had uncovered (or thrombus-covered) struts was 99.3% (96.1-99.9), 96.6% (92.4-98.5), 34.3% (15.0-60.7), and 9.6% (6.2-14.5) and malapposed struts was 21.8% (8.4-45.6), 8.5% (4.6-15.3), 6.7% (2.5-16.3), and 2.0% (1.2-3.3) for acute, subacute, late, and very late ST, respectively. The most common dominant finding adjudicated for acute ST was uncovered struts (66.7% of cases); for subacute ST, the most common dominant finding was uncovered struts (61.7%) and underexpansion (25.5%); for late ST, the most common dominant finding was uncovered struts (33.3%) and severe restenosis (19.1%); and for very late ST, the most common dominant finding was neoatherosclerosis (31.3%) and uncovered struts (20.2%). In patients presenting very late ST, uncovered stent struts were a common dominant finding in drug-eluting stents, and neoatherosclerosis was a common dominant finding in bare metal stents. In patients with ST, uncovered and malapposed struts were frequently observed with the incidence of both decreasing with longer time intervals between stent implantation and presentation. The most frequent dominant observation varied according to time intervals from index stenting: uncovered struts and underexpansion in acute/subacute ST and neoatherosclerosis and uncovered struts in late/very late ST.

IVUS-guided treatment strategies for definite late and very late stent thrombosis.

Our aim was to describe the intravascular ultrasound (IVUS) findings of patients with late stent thrombosis (ST) undergoing percutaneous intervention, and to compare the pre- and post-intervention IVUS findings of patients treated with balloon angioplasty (BA) vs. additional stent implantation (ASI). A total of 117 patients with late ST imaged with IVUS were included (51.2% had drug-eluting stent ST). Treatment was left to the operator's discretion: BA was performed in 53.8% and ASI in 46.2%. Pre-intervention, incomplete stent apposition (ISA) was observed in 69.8% vs. 63.0% (p=0.43), underexpansion in 33.3% vs. 18.5% (p=0.07) and restenosis in 15.9% vs. 27.8% (p=0.12), respectively. Post-intervention, persistent ISA was observed in 37.2% vs. 60.9% (p=0.03) and malapposition volume decreased by 43.6% vs. 2.6% (p=0.03). Persistent underexpansion was observed in 9.3% vs. 17.4% (p=0.26); however, the stent expansion index was largely increased with BA (from 0.75 to 0.88) compared to ASI (from 0.80 to 0.82); p=0.046. At two years, recurrent ST was observed in one (1.7%) vs. four (7.7%) patients, respectively; p=0.09. Non-optimal IVUS criteria of stent implantation are often observed in patients with late ST. Treatment of late ST with BA leads to a larger reduction of malapposition and underexpansion with respect to ASI and is associated with favourable outcomes.

Calcified plaque rupture and very late stent thrombosis after bare-metal stent implantation

Very late stent thrombosis (>1year: VLST) is a major concern in the drug-eluting stent (DES) era. VLST occurs not only in patients implanted with DESs but also in those implanted with bare-metal stents (BMSs). We examined intravascular ultrasound (IVUS) findings in patients with VLST after BMS implantation. Five consecutive patients presented with VLST as ST elevation myocardial infarction. VLST occurred at a mean of 9.5years after BMS implantation. In the IVUS findings, the minimum stent area was 7.8±1.2mm(2). None of the patients had incomplete stent apposition or stent underexpansion, which was defined as a stent expansion index of <0.8. The mean stent expansion index was 1.01. Calcium deposits in the previous stented segment were observed in 4 patients (80%), and a total of 14 calcium deposits were observed in all patients. The calcification pattern was superficial (78.5%) and spotty (57.1%) within a calcium arc of <90°. The mean calcium arc was 72.5°±88.5°. A ruptured plaque with an intraluminal flap was detected in all cases. According to the IVUS findings of ruptured plaque and calcium deposits, VLST after BMS might be caused by a thrombus formation subsequent to a calcified atherosclerotic plaque rupture.

Abstract 2566: Intravascular Ultrasound Guidance may Modify Neointimal Coverage Following Sirolimus-Eluting Stent Implantation

Background: Although sirolimus-eluting stent (SES) has significantly reduced in-stent restenosis, insufficient neointimal coverage may result in adverse outcomes. Intravascular ultrasound (IVUS) guided percutaneous coronary intervention improves the patency of bare-metal stents at follow-up. IVUS guidance at the time of SES implantation may also optimize neointimal coverage following stenting. Methods: We evaluated 55 SES implanted lesions using both angioscopy and IVUS at follow-up (12±7 months). The lesions were divided into two groups: IVUS guided implantation (group I, n=40); angiography alone (group A, n=15). Neointimal coverage was classified into 4 grades by angioscopy: no coverage ( G0 ); struts bulged into the lumen, but were covered and still translucently visible ( G1 ); struts were visible, but not clear ( G2 ); and struts were embedded and invisible ( G3 ). Minimal stent area (MSA), external elastic membrane (EEM), lumen cross-sectional area (CSA) and plaque burden were measured by IVUS at follow up. Both proximal and distal references were used. Stent expansion was assessed by stent expansion index (SEI) = MSA/reference EEM CSA. Results: Lesion and procedural characteristics were similar between the groups both at stent implantation and at follow-up. Although the post-procedural quantitative angiographic data were not different between the groups, distribution of the angioscopic grades of neointimal coverage at follow-up were significantly different (group A = 1.0±0.5 grades versus group I = 1.5±0.6 grades, p=0.01). IVUS measurements at follow up showed larger plaque burden at the proximal reference sites (54±12% versus 46±9%, p=0.02) and smaller SEI (0.35±0.09 versus 0.46±0.10, p=0.001) in group A than in group I. Conclusions: IVUS guidance at the time of SES implantation may modify angioscopic grades of the neointimal coverage, possibly optimizing neointimal coverage and preventing thrombosis.

Abstract 2777: Optimal Expansion of the Stent is a Major Contributor to the Neointimal Coverage Following Sirolimus-eluting Stent Implantation: A Combined Study of Angioscopy and Intravascular Ultrasound

Background: Although sirolimus-eluting stent (SES) has significantly reduced in-stent restenosis by inhibiting neointimal hyperplasia, insufficient neointimal coverage after stenting may result in adverse outcomes. Determinants of neointimal coverage following SES, however, are poorly understood. Methods: We evaluated 28 SES lesions using both angioscopy and intravascular ultrasound (IVUS). Degree of neointimal coverage was judged by angioscopy at follow-up (11 ± 6 months): complete/incomplete coverage, based on whether the stent struts were embedded by the neointima. Minimal stent area (MSA), external elastic membrane (EEM), lumen cross-sectional area (CSA) and plaque burden (EEM minus lumen/EEM CSA) were measured by IVUS at stent implantation. Both proximal and distal references were used. Stent expansion was assessed by stent expansion index (SEI) as MSA/reference EEM CSA. Under-expansion was defined as SEI &lt; 0.4. Incomplete apposition was defined as the lack of contact between any strut and the underlying vessel wall. Results: Complete coverage was identified in 10 (36%), and incomplete coverage in 18 (64%). Time from the stenting to angioscopy (10 ± 5 versus 11 ± 7 months, p=0.8) as well as the lesion and procedural characteristics was similar between the complete/incomplete coverage groups. IVUS parameters were also similar, except for the final MSA (7.0±1.8mm 2 in complete versus 5.3±1.9mm 2 in incomplete , p=0.02) and lumen CSA at the distal reference site (6.1±1.4mm 2 in complete versus 4.9 ±1.2mm 2 in incomplete , p= 0.02). The frequency of incomplete apposition was similar between the groups (20% in complete versus 39% in incomplete , P= 0.4); however, SEI was significantly larger in the complete coverage than in the incomplete coverage group (0.52 ± 0.11 versus 0.39 ± 0.09, p=0.002). Stent under-expansion was identified only in 2 (20%) of the complete coverage, as compared to 67% of the incomplete coverage group (P=0.046). By multivariate logistic regression analysis, large SEI was strongly associated with complete neointimal coverage (P=0.04). Conclusion: Optimal expansion of the stent is a major contributor to the complete neointimal coverage following sirolimus-eluting stent implantation.