Minimal Stent Cross-sectional Area Research Articles

Abstract 16295: Smaller Stent Area and Eccentric Expansion are Associated With Increased Adverse Events After Drug-eluting Stent Implantation in Hemodialysis Patients

Introduction: Factors for adverse cardiac events after drug-eluting stent (DES) implantation among patients with hemodialysis (HD) remain to be elucidated. Hypothesis: Suboptimal DES implantation is associated with the increased incidence of adverse events in patients with HD. Methods: A total of 109 consecutive patients with HD who underwent optical coherence tomography (OCT)-guided DES implantation were included. The impact of post-stent OCT findings on the incidence of device-oriented clinical endpoints (DoCE) at 1 year was investigated. DoCE included cardiac death, target vessel-related myocardial infarction, target lesion revascularization, and stent thrombosis. Results: There was no significant difference in baseline clinical characteristics and pre-stent lesion characteristics between patients with DoCE (n=15) and those without DoCE (n=94). Significant hazard ratio (HR) for the incidence of DoCE was not observed in the presence of edge dissection, irregular protrusion, or incomplete stent apposition (Panel A). In receiver operating characteristic curve analyses, the best cutoff of minimum stent cross-sectional area (MSA), %stent expansion [MSA / mean reference lumen cross-sectional area х 100], and eccentricity index (minimum stent diameter / maximum stent diameter) at MSA site for detecting DoCE was 3.4 (mm 2 ), 72.0 (%), and 0.71, respectively. Significant HR for the incidence of DoCE was observed in the presence of MSA< 3.4 (HR 3.58, 95% confidence interval [CI] 1.04 - 12.4, p=0.035) and eccentricity index< 0.71 (HR 6.68, 95% CI 1.94 - 23.0, p=0.001) (Panel B). Conclusions: Smaller stent area and eccentric expansion were associated with increased incidence of DoCE after DES implantation in patient with HD, although the presence of other post-stent suboptimal findings were not associated with the incidence of DoCE. The present results suggest the importance of larger stent area and concentric stent expansion in patients with HD.

IntravaScular Lithotripsy for the Management of UndILatable Coronary StEnt: The SMILE Registry

BackgroundIntravascular lithotripsy (IVL) showed to be effective in dilating heavily calcified de novo coronary lesions but little is known about its performance in under-expanded stents management. Aim of this study was to assess the feasibility, effectiveness and safety of IVL for the treatment of stent underexpansion refractory to balloon dilatation. MethodsA multicentre, retrospective cohort analysis was performed in patients undergoing IVL to treat under-expanded stents following non-compliant balloon expansion failure. Primary endpoint was successful IVL dilatation defined as IVL balloon delivery and application at the target site followed by an increase of at least 1 mm2 in minimal stent cross-sectional area (MSA) on intracoronary imaging or an increase of at least 20% in minimal stent diameter (MSD) by quantitative coronary analysis (QCA). ResultsThirty-nine under-expanded stents (34 patients) were included. Two cases (5.1%) of multiple stent layers and one (2.5%) acutely under-expanded stent were treated. The median IVL balloon diameter was 3.1 mm (IQR: 2.5–3.5 mm) while the number of pulses emitted was 56.7 (IQR: 30–80). IVL was successful in 34 cases (87.1%), with significant improvement in MSD (post: 3.23 mm [IQR: 3–3.5 mm] vs. pre: 0.81 mm [IQR: 0.35–1.2], p < 0.00001) and MSA (post: 7.61mm2 [IQR: 6.43–7.79mm2] vs. pre: 3.35 [IQR: 2.8–4 mm2], p < 0.00001). Non-fatal peri-procedural ST-elevation myocardial infarction occurred in one case (2.5%) due to IVL balloon rupture. No cardiac death, target lesion revascularization and stent thrombosis occurred in-hospital and at 30-day follow-up. ConclusionsBailout IVL was feasible, efficacious and safe to improve refractory stent under-expansion.

6109A novel parameter for stent expansion is superior to conventional parameters for predicting adverse events after drug-eluting stent implantation

Abstract Background Among several parameters for stent expansion, which is better for predicting adverse events remains to be elucidated. Purpose To assess the predictive significance of several parameters for stent expansion on the incidence of adverse cardiac events. Methods A total of 183 consecutive patients with de novo lesion treated with drug-eluting stent (DES) under optical coherence tomography (OCT) guidance were enrolled. The stent expansion was retrospectively assessed on the final OCT images after the stent implantation by both conventional and novel parameters. The conventional parameters included the minimum stent cross-sectional area (MSA) and %stent expansion defined as [MSA/mean reference lumen cross-sectional area × 100]. The novel parameter was the minimum expansion index (MEI) calculated by using a novel algorhythm which yields the ideal lumen area in each frame by taking into account vessel tapering. The expansion index was calculated by [actual lumen area/ideal lumen area × 100] in each frame through the stented segment. The MEI was the minimum value of expansion index through the stented segment. The both conventional and novel parameters were compared between cases with and without device-oriented cardiac events (DoCE). Receiver operating characteristics (ROC) curves were constructed to assess the ability of those parameters to predict DoCE. Results The MSA and MEI in the DoCE group (n=12) were significantly smaller than the no DoCE group (n=171) (3.29±0.72 vs. 4.45±1.97 mm2, p&lt;0.001, 66.9±10.6 vs. 78.3±14.8%, p=0.01, respectively), although the %stent expansion was not significantly different between the two groups (62.7±11.9 vs. 70.7±16.3%, p=0.094). In ROC analyses, the area under curve of MEI to predict DoCE was the largest among the parameters (Figure). Conclusion Among several parameters for stent expansion, a novel MEI was better to predict device-oriented cardiac events after DES implantation.

Serial Intravascular Ultrasound Findings After Treatment of Chronic Total Occlusions Using Drug-Eluting Stents

Morphologic changes after chronic total occlusion (CTO) treatment with drug-eluting stents (DESs) have not been assessed in detail. Our aim was to use both baseline and follow-up intravascular ultrasound studies to evaluate the morphologic changes and, especially, the changes in distal vessel size and the effect of subintimal stenting after treatment of CTOs with DES. We analyzed serial follow-up intravascular ultrasound (baseline and follow-up at 9 ± 2 months) after DES implantation into 40 CTOs. Overall, 33 CTOs were treated by the anterograde approach; and 7 were treated by the retrograde approach. Minimum lumen cross-sectional area (CSA) trended toward a decrease from baseline to follow-up (4.8 ± 1.7 vs 4.5 ± 1.7 mm(2), p = 0.10), although the minimum stent CSA (4.8 ± 1.7 vs 4.9 ± 1.7 mm(2), p = 0.26) did not change. The distal reference, but not the proximal reference lumen CSA, increased significantly at follow-up (3.8 ± 2.0 to 5.1 ± 2.3 mm(2), p = 0.0004). Late-acquired stent malapposition was seen in 17 patients (42.5%). In 8 CTOs (20%), a part of the stent was implanted into a subintimal space; in these 8 patients, maximum percent neointimal hyperplasia and minimum lumen area was similar in the subintimal segment compared with the adjacent intraplaque segment. The frequency of late-acquired stent malapposition was similar. In conclusion, after CTO treatment with DES, distal vessel enlargement was detected. Subintimal stenting after recanalization of CTO was not inferior compared with stenting within the plaque in terms of long-term morphologic impact.

Intravascular Ultrasound and Angiographic Predictors of In-Stent Restenosis of Chronic Total Occlusion Lesions.

Despite the benefits of successful percutaneous coronary interventions (PCIs) for chronic total occlusion (CTO) lesions, PCIs of CTO lesions still carry a high rate of adverse events, including in-stent restenosis (ISR). Because previous reports have not specifically investigated the intravascular ultrasound (IVUS) predictors of ISR in CTO lesions, we focused on these predictors. We included 126 patients who underwent successful PCIs, using drug-eluting stents, and post-PCI IVUS of CTO lesions. Patient and lesion characteristics were analyzed to elucidate the ISR predictors. In each lesion, an average of 1.7 ± 0.7 (mean length, 46.4 ± 20.3 mm) stents were used. At 9 months follow-up, 14 (11%) patients demonstrated ISR, and 8 (6.3%) underwent target lesion revascularization. Multivariate logistic regression analysis showed that the independent predictors of ISR were the post-PCI minimal luminal diameter (MLD) and the stent expansion ratio (SER; minimal stent cross-sectional area (CSA) over the nominal CSA of the implanted stent), measured using quantitative coronary angiography (QCA) and IVUS, respectively. A receiver operating characteristic analysis indicated that the best post-PCI MLD and SER cut-off values for predicting ISR were 2.4 mm (area under the curve [AUC], 0.762; 95% confidence interval (CI), 0.639–0.885) and 70% (AUC, 0.714; 95% CI, 0.577–0.852), respectively. Lesions with post-PCI MLD and SER values less than these threshold values were at a higher risk of ISR, with an odds ratio of 23.3 (95% CI, 2.74–198.08), compared with lesions having larger MLD and SER values. Thus, the potential predictors of ISR, after PCI of CTO lesions, are the post-PCI MLD and SER values. The ISR rate was highest in lesions with a post-PCI MLD ≤2.4 mm and an SER ≤70%.

Cutting-balloon angioplasty before drug-eluting stent implantation for the treatment of severely calcified coronary lesions.

BackgroundSeverely calcified coronary lesions respond poorly to balloon angioplasty, resulting in incomplete and asymmetrical stent expansion. Therefore, adequate plaque modification prior to drug-eluting stent (DES) implantation is the key for calcified lesion treatment. This study was to evaluate the safety and efficacy of cutting balloon angioplasty for severely calcified coronary lesions.MethodsNinety-two consecutive patients with severely calcified lesions (defined as calcium arc ≥ 180° calcium length ratio ≥ 0.5) treated with balloon dilatation before DES implantation were randomly divided into two groups based on the balloon type: 45 patients in the conventional balloon angioplasty (BA) group and 47 patients in the cutting balloon angioplasty (CB) group. Seven cases in BA group did not satisfactorily achieve dilatation and were transferred into the CB group. Intravascular ultrasound (IVUS) was performed before balloon dilatation and after stent implantation to obtain qualitative and quantitative lesion characteristics and evaluate the stent, including minimum lumen cross-sectional area (CSA), calcified arc and length, minimum stent CSA, stent apposition, stent symmetry, stent expansion, vessel dissection, and branch vessel jail. In-hospital, 1-month, and 6-month major adverse cardiac events (MACE) were reported.ResultsThere were no statistical differences in clinical characteristics between the two groups, including calcium arc (222.2° ± 22.2° vs. 235.0° ± 22.1°, P = 0.570), calcium length ratio (0.67 ± 0.06 vs. 0.77 ± 0.05, P = 0.130), and minimum lumen CSA before PCI (2.59 ± 0.08 mm2 vs. 2.52 ± 0.08 mm2, P = 0.550). After stent implantation, the final minimum stent CSA (6.26 ± 0.40 mm2 vs. 5.03 ± 0.33 mm2; P = 0.031) and acute lumen gain (3.74 ± 0.38 mm2 vs. 2.44 ± 0.29 mm2, P = 0.015) were significantly larger in the CB group than that of the BA group. There were not statistically differences in stent expansion, stent symmetry, incomplete stent apposition, vessel dissection and branch vessel jail between two groups. The 30-day and 6-month MACE rates were also not different.ConclusionsCutting balloon angioplasty before DES implantation in severely calcified lesions appears to be more efficacies including significantly larger final stent CSA and larger acute lumen gain, without increasing complications during operations and the MACE rate in 6-month.

Excimer Laser LEsion Modification to Expand Non-dilatable sTents: The ELLEMENT Registry

Stent underexpansion is a risk factor for in-stent restenosis and stent thrombosis. Existing techniques to optimize stent expansion are sometimes ineffective. The aim of this study was to evaluate the effectiveness and feasibility of Excimer Laser Coronary Angioplasty (ELCA) in improving stent expansion when high-pressure non-compliant balloon inflation was ineffective. ECLA ablation was performed at high energy during contrast injection and only within the underexpanded stent. The primary endpoint of successful laser dilatation was defined as an increase of at least 1mm(2) in minimal stent cross-sectional area (MSA) on IVUS or an increase of at least 20% in minimal stent diameter (MSD) by QCA, following redilatation with the same non-compliant balloon that had been unsuccessful prior to ELCA. Secondary endpoints were cardiac death, myocardial infarction (MI) and target lesion revascularization. Between June 2009 and November 2011, 28 patients with an underexpanded stent despite high-pressure balloon inflation were included. The mean laser catheter size was 1.2±0.4 (range 0.9-2.0mm) and a mean of 62±12mJ/mm(2) at 62±21hertz were required for optimal expansion. Laser-assisted stent dilatation was successful in 27 cases (96.4%), with an improvement in MSD by QCA (1.6±0.6mm at baseline to 2.6±0.6mm post-procedure) and MSA by IVUS (3.5±1.1mm(2) to 7.1±1.9mm(2)). Periprocedural MI occurred in 7.1%, transient slow-flow in 3.6% and ST elevation in 3.6%. During follow-up, there were no MIs, there was 1 cardiac-death, and TLR occurred in 6.7%. The ELLEMENT study confirms the feasibility of ELCA with contrast injection to improve stent underexpansion in undilatable stented lesions.

Influence of additional ballooning with a dual wire balloon after a rotational atherectomy to expand drug-eluting stent for calcified lesions

Calcified lesions have been known as a cause of stent underexpansion which increases the risk of thrombosis and in-stent restenosis. A dual wire balloon has been introduced to create a focal stress pattern in a localized region of the calcification. We evaluated the combination therapy using a dual wire balloon after rotational atherectomy (RA) for heavily calcified lesions. Of 21 consecutive patients with severe calcified lesions, 10 patients were treated with a dual wire balloon after RA, and 11 patients were treated with RA alone or, RA plus the conventional balloon. Finally, drugeluting stents (DES) were implanted in all cases. Baseline characteristics, lesion characteristics, and postdilatation procedures were not different between two groups. Before implantation of DES, a dual wire balloon enabled adequate dilatation with significantly more cracks than RA (1.8 ± 0.4 cracks vs. 1.2 ± 0.6 cracks, P = 0.02). The minimal stent cross sectional area (CSA) and the stent expansion ratio were similar in both groups. However, the symmetrical expansion was significantly accomplished in patients with a dual wire balloon compared to those without it (mean ratio calculated by dividing the shortest diameter by the longest diameter at the site of the minimal stent CSA was 0.83 ± 0.05 vs. 0.76 ± 0.07, P = 0.02). Moreover, no in-stent restenosis was observed in patients treated with a dual wire balloon at follow-up. In conclusion, by using a dual wire balloon after RA, adequate stent expansion and follow-up results were accomplished. This combination therapy is safety and feasible procedure for the treatment of severe calcified lesions.

ROTATIONAL ATHERECTOMY FOLLOWED BY CUTTING BALLOON PLAQUE MODIFICATION BEFORE DRUG-ELUTING STENT IMPLANTATION IN CALCIFIED CORONARY LESIONS

Results: Thirty patients with 31 severely calcified lesions were identified: 15 patients (with 15 lesions) were included in the ROTACUT group and 15 patients (with 16 lesions) in the control group. There were statistically no differences in the final burr size (1.60 ± 0.18 mm vs. 1.67 ± 0.22 mm, p = 0.332), the maximum (max) balloon diameter before stent implantation (2.93 ± 0.36 mm vs. 2.72 ± 0.42 mm, p = 0.137), the max final balloon diameter (3.33 ± 0.29 mm vs. 3.28 ± 0.44 mm, p = 0.702), and the max final balloon inflation pressure (14.7 ± 2.9 atm vs. 16.4 ± 5.5 atm, p = 0.286). The max balloon inflation pressure before stent implantation was significantly lower in the ROTACUT group (9.7 ± 1.9 atm vs. 14.5 ± 2.9 atm, p < 0.001). Final minimum stent cross-sectional area (CSA) was significantly larger in the ROTACUT group compared to the control group (6.61 ± 1.14 mm2 vs. 5.38 ± 1.89 mm2, p = 0.036).

Assessment of the relation between IVUS measurements and clinical outcome in elderly patients after sirolimus-eluting stent implantation for de novo coronary lesions

This study aimed to evaluate the impact of vascular response assessed by intravascular ultrasound (IVUS) imaging on clinical outcomes in elderly patients (≥ 75 years) undergoing percutaneous coronary intervention (PCI) for de novo lesions with sirolimus-eluting stent (SES) implantation. Repeat coronary angiography with IVUS was performed 1 year after SES-based PCI for de novo lesions in 136 elderly patients (≥ 75 years) and 427 younger counterparts (< 75 years) (219 lesions and 635 lesions, respectively). Major adverse cardiac events (MACE) including cardiac death, non-fatal myocardial infarction, and target lesion revascularization (TLR) during 2-year follow-up were recorded. Despite similar angiographic in-stent restenosis and TLR and IVUS-detected incomplete stent apposition (ISA), absolute intimal hyperplasia and percentage of volumetric obstruction were lower in elderly than in younger patients. At 2-year follow-up, cumulative survival freedom from composite death and myocardial infarction or MACE was significantly reduced in elderly patients, but very late stent thrombosis was similar in the two groups. Cox proportional hazards model identified age, diabetes, left ventricular ejection fraction, lesion length,minimal stent cross-sectional area and plaque progression as independent predictors of non-fatal myocardial infarction or mortality. In elderly patients undergoing SES-based PCI, despite similar TLR, neointimal hyperplasia was significantly lower than in younger patients. IVUS measurements except for minimal stent cross-sectional area did not correlate with stent thrombosis and clinical outcomes at 2 years.

Usefulness of Minimum Stent Cross Sectional Area as a Predictor of Angiographic Restenosis After Primary Percutaneous Coronary Intervention in Acute Myocardial Infarction (from the HORIZONS-AMI Trial IVUS Substudy)

HORIZONS-AMI was a prospective dual-arm randomized trial of different antithrombotic regimens and stent types in patients with ST-segment elevation myocardial infarction. A formal intravascular ultrasound (IVUS) substudy enrolled 464 patients with baseline and 13-month follow-up at 36 centers. Of them, 318 patients with 355 lesions were evaluated for this study. Angiographic restenosis occurred in 45 of 355 lesions (12.7%). Bare-metal stent use (45.5% vs 21.2%, p <0.001) and diabetes mellitus (29.5% vs 10.9%, p <0.001) were more prevalent in patients with versus without restenosis. Postprocedure IVUS minimum lumen area (5.6 mm(2), 5.0 to 6.1, vs 6.7 mm(2), 6.5 to 6.9, p <0.001), minimum stent area (5.7 mm(2), 5.1 to 6.3, vs 6.9 mm(2), 6.6 to 7.1, p <0.001), and reference average lumen area (7.7 mm(2), 6.8 to 8.6, vs 9.7 mm(2), 9.3 to 10.1, p <0.001) were smaller in restenotic versus nonrestenotic lesions. By multivariable analysis, minimum stent area was an independent predictor of angiographic restenosis (odds ratio 0.75, 95% confidence interval 0.61 to 0.93, p = 0.009) in addition to diabetes, bare-metal stent use, and longer stent length. Attenuated plaque behind the stent struts had a trend to predict less binary restenosis (p = 0.07). In conclusion, a smaller IVUS minimum stent area was an independent predictor of angiographic restenosis after primary percutaneous intervention in patients with ST-segment elevation myocardial infarction, similar to patients with stable coronary artery disease.

Effect of intravascular ultrasound-guided adjuvant high-pressure non-compliant balloon post-dilation after drug-eluting stent implantation

Drug-eluting stent (DES) expansion characteristics after aggressive high-pressure post-dilation using a non-compliant (NC) balloon have not been fully investigated. We evaluated 58 patients with native coronary lesions treated with DESs [24 paclitaxel eluting stents (PES) and 34 sirolimus-eluting stents (SES)]. After post-dilation (12-14atm) using a stent-mounted semi-compliant balloon to reduce stent edge injury, adjuvant high-pressure post-dilation using NC balloon was performed within the stents. Stent size, stent length, and NC balloon size were selected based on preinterventional intravascular ultrasound (IVUS) assessment. Stent underexpansion was defined according to criteria of the Multicenter Ultrasound Stenting in Coronaries (MUSIC) study as a minimal stent cross-sectional area <90% of the average reference lumen area. Resultant endpoint was to obtain optimal stent expansion. Serial changes of stent expansion and stent symmetry were calculated in each group. After stent-mounted semi-compliant balloon post-dilation, both stents could not achieve adequate percent stent expansion (PES 73±18% vs. SES 67±9%, p=0.38). After high-pressure post-dilation using an NC balloon, percent stent expansion was 97±14% in PES and 91±13% in SES, respectively (p=0.25). Axial stent symmetry indices also significantly improved in both groups. Although radial stent symmetry indices improved significantly in PES group, those in the SES group had no significant changes. Finally, frequency of stent underexpansion significantly reduced, 87-20% in PES and 92-15% in SES, respectively (p=0.01) without any significant stent edge injury. DES expansion improved safely after adjuvant high-pressure post-dilation using an NC balloon under IVUS guidance.

Defining a new standard for IVUS optimized drug eluting stent implantation: The PRAVIO study

Preliminary Investigation to the Angiographic Versus IVUS Optimization Trial is a single center prospective observational intravascular ultrasound (IVUS) guided stent implantation study assessing new criteria for optimal drug eluting stent (DES) deployment. IVUS assessment of DES often reveals underexpansion and malapposition. Optimal stent deployment is currently poorly defined and previous criteria may not be suitable in long and complex lesions. Optimization was defined as achieving >/or 70% of the cross-sectional area (CSA) of the postdilation balloon. This criterion was applied in 113 complex lesions. The size of this balloon was calculated according to vessel media-to-media diameters at various sites inside the stented segment. The IVUS guided treated lesions were matched according to diabetes, vessel type, reference vessel diameter, minimum lumen diameter (MLD), and lesion length with a group of angiographic treated lesions to compare final MLD achieved. Mean minimum stent CSA according to the postdilation balloon utilized was 4.62 mm(2), 6.26 mm(2), 7.87 mm(2), and 9.87 mm(2) for 2.5 mm, 3.0 mm, 3.5 mm, and 4 mm balloons, respectively. Final MLD (mm) was significantly larger in the IVUS compared to the angiographic-guided group (3.09 +/- 0.50 vs. 2.67 +/- 0.54; P < 0.0001). There were no procedural complications related to IVUS use. We propose new IVUS criteria based on vessel remodeling that results in an increment in the final MLD, compared to angiographic guidance, which is much larger than any previously published study. This criterion seems to be safely achievable. A proposed randomized study (angiographic vs. IVUS optimization trial) has been launched to test these concepts.

Intravascular Ultrasound Assessment of Expansion of the Sirolimus-Eluting (Cypher Select) and Paclitaxel-Eluting (Taxus Express-2) Stent in Patients With Diabetes Mellitus

Patients with diabetes have a higher risk for in-stent restenosis after coronary stent implantation. Drug-eluting stents (DES) are highly effective in reducing in-stent restenosis. Once neointimal hyperplasia is suppressed with DES, the impact of stent underexpansion becomes magnified. The aim of this study was to evaluate DES expansion in patients with diabetes. Ninety-five patients with diabetes were randomized to Cypher Select (n = 48) or Taxus Express-2 (n = 47) stent implantation. Intravascular ultrasound was performed after stent implantation. Stent expansion was defined as the ratio of measured to predicted minimum stent diameter. There was a trend for lower stent expansion in the Cypher Select stent group (0.74 +/- 0.08 vs 0.78 +/- 0.11 in the Taxus Express-2 stent group, p = 0.061). Cypher Select stents achieved a final minimal stent cross-sectional area of 5.5 +/- 1. 8 mm2, compared with 6.4 +/- 1.9 mm2 for Taxus Express-2 stents (p = 0.015). For stents with nominal diameters > or =2.75 mm (Cypher Select n = 40, Taxus Express-2 n = 38), 42.5% of the Cypher Select stents and 10.5% of the Taxus Express-2 stents did not achieve a final minimum stent area of 5 mm2 (p = 0.002). Insulin treatment (relative risk 0.31, 95% confidence interval 0.10 to 0.95, p = 0.041) and stent type (relative risk 0.15, 95% CI 0.04 to 0.53, p = 0.003) were independent predictors of not achieving a minimum stent area >5.0 mm2. In conclusion, an important percentage of DES in patients with diabetes fail to achieve the manufacturers' predicted final minimal stent diameter. Cypher Select stent and insulin treatment were independent predictors of not achieving a minimum stent area >5.0 mm2.

Is Stent Underexpansion the Main Cause of In-Stent Restenosis after Sirolimus-Eluting Stent Implantation?: An Intravascular Ultrasound Study

Background and Objectives:Intravascular ultrasound (IVUS) can be useful for assessing the causes of in-stent restenosis (ISR) after sirolimus-eluting stent (SES) implantation. We used IVUS to evaluate the causes of ISR after SES implantation. Subjects and Methods:SES implantation was performed in 502 patients with 670 coronary lesions. Of these patients, 27 patients had angiographic ISR in 28 lesions. We evaluated the patterns of ISR and we wanted to elucidate the possible mechanism of ISR after SES implantation with using IVUS analysis. Results:The ISR pattern was focal in 26 lesions, and diffuse in 2 lesions, including 1 total occlusion. When analyzing the 21 IVUS-applicable lesions, stent underexpansion [the minimal stent cross-sectional area (CSA) was <5 mm and it was <4.5 mm in the cases of small coronary arteries (reference vessel diameter <2.8 mm)] was observed in 10 lesions (48%). Stent fracture (defined as non-visualization of the struts on IVUS at the restenotic segments) and edge restenosis was identified in the 3 (14%) and 3 lesions (14%), respectively. Except for edge stenosis, stent underexpansion was observed in 55% of the intra-stent restenotic lesions and it was more prominent in the small coronary arteries (7/8 small coronary artery lesions). Stent underexpansion, stent fracture or edge restenosis were not related to the 7 ISR lesions (33%) in which profound intimal hyperplasia within the stent occurred. Conclusion:Our observation of ISR after SES implantation with using IVUS showed that most ISR lesions have mechanical problems, especially stent underexpansion. However, one third of the ISR lesions were associated with profound intimal hyperplasia within the stent. (Korean Circulation J 2007;37:58-63)

Underexpansion of sirolimus‐eluting stents: Incidence and relationship to delivery pressure

We aimed to assess the incidence of underexpansion and the relationship between delivery pressure and expansion with sirolimus-eluting stents. Adequate stent expansion contributes to early and late improved outcomes. In 51 patients (53 lesions) with native coronary artery narrowing, balloon-expandable sirolimus-eluting stents (Cypher) were serially expanded with gradual balloon inflations [14 atm, 20 atm, and in case of minimal stent cross-sectional area (CSA)/reference lumen CSA < 50% at 20 atm, postdilatation with 0.5 mm larger balloon]. Intravascular ultrasound (IVUS) imaging was performed before intervention and after each gradual balloon inflation. Stent expansion (minimal stent CSA/reference lumen CSA) was measured. Stent expansion was 72% +/- 16% after 14 atm balloon inflation, 90% +/- 18% after 20 atm balloon inflation (P < 0.001 vs. 14 atm), and 90% +/- 18% at the end of the procedure (including optional postdilatations with 0.5 mm larger balloon; P = NS vs. 20 atm). Stent expansion addressed by MUSIC criteria (all struts apposed, no tissue protrusion, and final lumen CSA > 80% of the reference or > 90% if minimal lumen CSA was < 9 mm2) was adequate in 15% of the cases after 14 atm balloon inflation, in 60% after 20 atm balloon inflation (P < 0.001 vs. 14 atm), and in 60% at the end of the procedure (P = NS vs. 20 atm). Sirolimus-eluting stent underexpansion is common when deployed at conventional pressures. Increasing balloon delivery pressure or assessing stent expansion with IVUS seems warranted in order to ensure adequate sirolimus-eluting stent deployment.

Incidence of Stent Under-Deployment as a Cause of in-Stent Restenosis in Long Stents

Although stent under-deployment (SU) has been associated with increased risk of in-stent restenosis, little data have been reported on the incidence of SU in patients presenting with clinical in-stent restenosis. In 59 patients referred for vascular brachytherapy and showing angiographic in-stent restenosis, we sought (1) to determine the incidence of SU using standard intravascular ultrasound (IVUS) criteria (2) to evaluate the effects of repeat angioplasty on further stent expansion. Stented length was 32+/-17 mm and diameter stenosis was 75+/-14%. Before re-intervention, the incidence of reduced absolute values of minimal stent cross-sectional area (MSCSA) varied from 69% (< or =8 mm2) to 15% (< or =5 mm2). After re-intervention, the incidence decreased to 24% (< or =8 mm2) (p = 0.0001) and 0% (< or =5 mm2) (p = 0.005). Before re-intervention, SU as assessed by relative criteria varied from 21% (80% mean reference lumen area or 90% minimum distal reference lumen area) to 28% (100% minimum reference lumen area). After re-intervention, the incidence of SU varied from 7% (90% minimum distal reference lumen area) (p = 0.0001 vs. pre) to 24% (55% mean reference EEM area) (p = ns). No change in strut apposition (97% pre vs. 100% post) nor in symmetry index (100% pre vs. post) was noted. From all criteria, the 90 and 100% minimum reference lumen area criteria were the most altered by repeat balloon dilatation, 21% pre vs. 7% post and 28% pre vs. 11% post, respectively. In conclusion, among patients presenting with severe angiographic in-stent restenosis, a significant number showed signs of SU whose incidence varied according to applied criteria. Significant stent re-expansion can be obtained following IVUS-guided repeat angioplasty irrespective of initial SU criteria.

Optimizing stent expansion with new stent delivery systems

OBJECTIVESThe purpose of this study was to assess whether the newer stent delivery systems provide a stented lumen cross-sectional area (CSA) that is equal to the delivery balloon nominal dimensions.BACKGROUNDFirst generation stents were often not adequately expanded with their delivery system and frequently required higher pressure or a larger balloon after deployment. Newer stents were designed to optimize expansion with noncompliant, high-pressure balloons provided as the delivery systems.METHODSIntravascular ultrasound (IVUS) was used to evaluate 38 stents in 32 patients after deployment at 14 to 16 atm with their delivery balloon system. Minimum stent lumen CSA and stent minimum lumen diameter (MLD) were measured by IVUS imaging. The manufacturer’s expected stent diameter was defined as the balloon diameter measured by the company at the maximum pressure used. The manufacturer’s expected stent area was calculated based on the manufacturer’s expected stent diameter.RESULTSThe MLD (2.5 ± 0.5 mm) and minimum stent CSA (6.0 ± 1.7 mm2) by IVUS were significantly smaller than the manufacturer’s expected stent diameter (3.5 ± 0.4 mm) and area (9.5 ± 1.9 mm2) (p < 0.0001, respectively). The mean MLD by IVUS was 72 ± 8% of the expected stent diameter, and the mean minimum stent CSA by IVUS was 62 ± 10% of the expected stent area.CONCLUSIONSDespite moderately high-pressure inflations, the mean minimum stent CSA actually achieved was, on average, only 62% of the manufacturer’s expected stent area. To optimize stent deployment, these IVUS observations should be considered during coronary artery stenting.

Intravascular ultrasound assessment of the mechanisms and results of brachytherapy.

Serial intravascular ultrasound (IVUS) studies have shown that restenosis in nonstented lesions and late lumen loss in reference segments contiguous with both stented and nonstented lesions is a balance between arterial remodeling and neointimal hyperplasia. Conversely, in-stent restenosis (ISR) is neointimal hyperplasia.1,2 The present review focuses on lessons learned from IVUS about mechanisms of brachytherapy in preventing or treating restenosis. Most brachytherapy studies have included IVUS analyses, but to various degrees and with various methodologies. In some studies—eg, the Washington Radiation for In-stent Restenosis (WRIST) trials—serial (postirradiation and follow-up) IVUS was performed in the majority of patients. In other trials, IVUS was usually a site-specific substudy in small numbers of patients (Table 1). These studies assessed only the short-term (typically 6 to 9 months) effects of brachytherapy. View this table: Table 1095275. IVUS Analyses in Various Brachytherapy Trials IVUS should be performed with motorized transducer pullback, and volumetric as well as mean cross-sectional area (CSA) analysis should be reported. Because lesion lengths vary among trials, longer lesions may have larger stent, lumen, and neointimal volumes. Therefore, mean planar analysis (in which measured volumes are normalized for lesion length) may be a preferable way to compare different studies. Understanding lesion effects is more straightforward than understanding edge effects. (1) Edge analysis was not performed in all studies (Table 1). (2) Some studies combined proximal and distal edges and analyzed them together; others analyzed proximal and distal edges separately. (3) Edge analysis requires a larger sample size because of the wider range of possible responses. (4) It may be hard to determine the relationship between the source, the injured segment, and the IVUS images to assess geographical miss. Angiographic guidance may work in stented lesions; even in stented lesions (which are often radiolucent), however, meticulous comparison of IVUS and angiographic studies is necessary. (5) Some studies …

Intravascular Ultrasound Analysis of Factors Associated with Suboptimal Stent Expansion after High Pressure Balloon Inflation

Background:The intracoronary stent implantation is regarded as an effective treatment modality of coronary artery disease. However, inadequate stent expansion was associated with subacute stent thrombosis and late restenosis. The high-pressure inflation stenting reduced the incidence of stent thrombosis and restenosis. Therefore, we intended to evaluate factors associated with suboptimal stent expansion after high-pressure balloon inflation. Method:One hundred and thirty eight patients with 150 lesions were treated with 168 stents of various types. Intravascular ultrasound(IVUS images were obtained after angiographic optimization (<10% of residual stenosis with high-pressure inflation stenting. In a subgroup of 61 selected patients with 61 lesions, IVUS images were obtained before predilation of the lesions. The quantitative off-line measurements of IVUS parameters were performed. An optimal stent expansion was defined by IVUS as minimal stent cross sectional area(CSA of ≥90% of the distal reference lumen CSA. Severe calcifications were defined by IVUS as arc of calcium ≥180° . Results:An optimal stent expansion was achieved in 67% of the 150 lesions. At preintervention, severe calcifications were in 10%(5/51 in optimal stent expansion and in 40%(4/10 in suboptimal stent expansion(p<0.05. At postintervention, minimal stent CSA was 8.0mm 2 in optimal stent