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.     

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 (12–14 atm) 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.     

Quantitative changes in reference segments during IVUS-guided stent implantation: Impact on the criteria for optimal stent expansion

Intravascular ultrasound is an established method to optimize stent implantation. Stent expansion is estimated from the relation between minimal in-stent cross-sectional area and reference lumen area. We analyzed the periprocedural lumen increment in the reference segments and its impact on intravascular ultrasound (IVUS) criteria for optimized stenting. Seventy-five consecutive patients were studied with a 2.9 Fr, 30-MHz system and motorized pullback (0.5 mm/sec). Lumen area was measured by planimetry; absolute and relative differences in area (Δ area) were calculated. Lumen area increment for reference segments proximal and distal to the stent was 6.4% ± 10.3% and 6.1% ± 10.8%; 49/75 patients fulfilled all IVUS criteria for optimal stent expansion at the final IVUS assessment, and 10/75 patients met all the IVUS criteria in relation to the first measurement of reference lumen area, but not in relation to the final measurement of reference lumen area. During high-pressure dilatation within the stent, reference lumen increment is visible. If reference lumen planimetry is not repeated after additional high-pressure balloon inflation, the final relative stent expansion may be overestimated. Cathet. Cardiovasc. Intervent. 47:434–440, 1999. © 1999 Wiley-Liss, Inc.     

Effect of balloon inflation time on expansion of sirolimus-eluting stent

There is little information about the relationship between balloon inflation time and sirolimus-eluting stent (SES) expansion. In this randomized intravascular ultrasound (IVUS) study, 92 de novo lesions in native coronary arteries that underwent SES implantation were enrolled. Sirolimus-eluting stent was implanted using an inflation pressure of 14 atm. Stent balloon was gradually inflated until 14 atm in 10 s. In the short inflation group, it was deflated immediately after an image of the balloon inflated at 14 atm was taken. Stent balloon inflation lasted 60 s in the long inflation group. Intravascular ultrasound was then performed. The long balloon inflation resulted in a larger stent cross-sectional area (4.9 ± 1.6 mm² vs 4.3 ± 1.4 mm², P < 0.05) and expansion (71% ± 13% vs 60% ± 13%, P < 0.001) compared to the short balloon inflation, although stent expansion was relatively low in both groups. The relatively longer balloon inflation time using an inflation pressure of 14 atm results in better SES expansion. However, in the majority of lesions, adequate stent expansion is not achieved even using long balloon inflation, if it is inflated at 14 atm.     

Angiography-guided routine coronary stent implantation results in suboptimal dilatation

The resistance of the atherosclerotic lesion counteracts the expansion of the stent, resulting in suboptimal stent expansion. Intravascular ultrasound provides more precise information on stent expansion than coronary angiography but adds cost and time to the percutaneous transluminal coronary angiography procedure. The aim of this study was to evaluate the need for intravascular ultrasound at routine angiography-guided high pressure stent implantation by comparing stent expansion with predefined intracoronary ultrasound criteria for optimal stent implantation. In 32 patients, 48 stents (35 NIR, 12 AVE, and 1 Cordis) were implanted in A, B, and C stenoses using a high-pressure inflation technique until an optimal result was achieved according to angiography. Stent expansion was then evaluated by intravascular ultrasound as minimal lumen diameter, minimal lumen area, proximal and distal stent area, and a minimal lumen area symmetry index. These variables were then compared with the nominal stent size in vitro. Finally the stents were also evaluated with respect to the MUSIC criteria, ie, strict criteria regarding symmetry, apposition, and vessel geometry according to intravascular ultrasound after stent expansion. Forty-five stents could be completely analyzed. The mean balloon inflation pressure was 12.8 (range, 10-17) atm. The nominal stent size was not achieved in any patient. Minimal lumen diameter attained 77% and minimal lumen area 78% of expected nominal values (p<0.0001), distal stent area 88% (p < 0.001), and proximal stent area 92% (ns). Application of the MUSIC criteria showed that almost all stents (96%) had good stent apposition and symmetry index. Optimal proximal stent entrance was found in 70%. Optimal minimal lumen area in comparison to the reference areas was present in 41%. This lead to fulfilling of all MUSIC criteria in 47% of the stents. If nominal stent size had been achieved, symmetry index and apposition would have been fulfilled in all cases and optimal minimal lumen area increased to 75%. Acceptable proximal entrance however would have decreased to 55% and the fulfillment of all MUSIC criteria would increase only to 52%. In routine angiography-guided stent implantation in stenoses with a wide range of severities using modern stents and high pressure inflation technique to reach a visually optimal result, the nominal stent size was never achieved mainly due to residual intrastent stenosis. If nominal stent size had been achieved, the results would have improved only marginally and would still be suboptimal in almost half of the stents. These results highlight the shortcoming of angiography and the need for intravascular ultrasound in choosing correct stent size.     

Angiographic and intravascular ultrasound follow up of paclitaxel‐ and sirolimus‐eluting stent after poststent high‐pressure balloon dilation: From the poststent optimal stent expansion trial

Objectives : The aims of this study were to identify the efficacy of optimal stent expansion (OSE) according to the Multicenter Ultrasound Stenting in Coronaries Study (MUSIC Study) criteria in drug‐eluting stent (DES) and compare paclitaxel‐eluting stent (PES) to sirolimus‐eluting stent (SES). Background : Although poststent high‐pressure balloon dilatation is proposed after bare metal stent implantation according to OSE, defined by the criteria of the MUSIC Study, very little data are available in DES. Methods : Two hundred fifty patients (M:F = 149:101; age, 61.5 ± 9.2 years) who underwent 9‐month follow‐up angiography in the Poststent Optimal Stent Expansion Trial (POET) were included in this study. We assessed angiographic in‐stent restenosis (ISR) and neointima volume (NV) using IVUS at 9 months. Results : At 9‐month follow up, there were no significant differences in ISR and NV index (NV/stent length, mm²) between patients with and without OSE. However, the rate of ISR and NV index were higher in PES [ISR: 18 (13.7%) and 4 (3.4%), P = 0.004; NV index: 1.02 ± 0.99 mm² and 0.21 ± 0.37, P < 0.001 in PES and SES]. Conclusions : OSE according to the MUSIC Study criteria was not related to ISR and NV in the DES era but PES had a significantly higher ISR rate and NV than SES after poststent high‐pressure balloon dilatation. © 2010 Wiley‐Liss, Inc.     

Discrepancy between morphologic and functional criteria of optimal stent deployment using intravascular ultrasound and pressure derived myocardial fractional flow reserve

BACKGROUND: Pressure derived myocardial FFR, a functional index of epicardial stenosis has been proposed for the assessment of optimal stent deployment. The following study evaluated the potential of serial fractional flow reserve (FFR) measurements in comparison to the ‘gold standard’ intravascular ultrasound (IVUS) for optimal stent deployment and its long‐term outcome. METHODS: 35 patients with a single de novo lesion underwent PTCA followed by stent implantation with an initial inflation pressure of 12 atm. If optimal stent expansion using IVUS‐criteria were not fulfilled, re‐dilatation at 16 atm as well as additional inflations with larger balloon sizes were performed to reach the procedural end‐point. IVUS and FFR were performed after each dilatation (n?=?136). Angiography was repeated after 6 months. RESULTS: In 30 pts who fulfilled IVUS criteria, mean lumen area (2.9±1.3?mm²) increased after PTCA and stent implantation to 10.0±3.0?mm². In six pts, optimum stent deployment according to a value of FFR?0.94 was not reached. Four of six pts reached the IVUS criteria at 12 atm and two pts at 16 atm, respectively. Positive and negative predictive values of FFR were 26 and 64%. Three of the 30 pts (10%) revealed a restenosis at three months follow‐up. One of these restenosis was seen in a patient with a post‐procedural FFR<0.94. CONCLUSIONS: FFR was not valid to predict optimal stent expansion according to IVUS criteria but could delineate under‐expanded stents despite a reasonable angiographic appearance. Morphologic (IVUS) and functional criteria (FFR) for optimal stent deployment revealed a comparably low restenosis rate.     

Should every eligible lesion undergo direct stenting?

Although significant coronary artery (CA) calcification is believed to affect stent deployment, the exact impact on stent deployment after high-pressure balloon inflations is unknown. Intracoronary intravascular examination (ICUS) was performed in 27 moderate-severe calcified CA lesions before and after stent implantation. In case of unsatisfactory results (in-stent area < 90%, minimal in-stent diameter/maximal in-stent diameter < 0.8), further inflations up to 20 atm guided by ICUS were applied. Initially, stent expansion was adequate in 10 stents (37%) and symmetric in 19 (70%). After inflation at 20 atm, stents with adequate expansion increased to 16 (59%, P = 0.0036), but stents with symmetry decreased to 13 (48%, P = 0.0045). Stent expansion was inversely correlated to the arc of calcium (r = -0.8, P < 0.0001). There were five patients with clinical restenosis at 6 months (18%). Increases in stent lumen area with high-pressure balloon inflations in moderate-severe calcified CA lesions are at the expense of symmetry. This may affect clinical restenosis.     

Role of intracoronary ultrasound after high-pressure stent implantation

BACKGROUND: Poststent high-pressure balloon inflation has been shown to improve clinical outcomes. However, it is unknown whether intracoronary ultrasound (ICUS) provides additional clinical guidance after initial high-pressure balloon inflation is used during stent placement. Thus the purpose of this study was to determine if stent deployment techniques are improved with ICUS imaging despite an optimal angiographic result achieved with high-pressure balloon inflation. METHODS AND RESULTS: Prospective data were collected on 96 consecutive patients in whom 151 stents were deployed. Stents and high-pressure balloons were angiographically sized 1:1 by visual estimation. High-pressure (> or =12 atm in all cases) balloon inflations were continued until angiographic completion (<10% residual stenosis), after which index ICUS imaging was performed. Stent apposition, symmetry, and lumen dimensions were evaluated. An optimal ICUS result was defined as full apposition of the stent, symmetry ratio > or =0.80, and acute gain > or =0.80 of the reference lumen area. If inadequate ICUS results were found, further dilations with higher pressures or larger balloons and subsequent stent reevaluation with ICUS were performed. Sixty-nine (46%) stents required additional balloon inflations. Of these stents, 35 (23%) had initial acute gains that were <80% of the reference lumen area. Forty-six (30%) stents were found to have unapposed struts and 24 (16%) had a symmetry ratio <0.80. In patients requiring additional inflations, minimum stent area increased from 7.6 +/- 2.2 mm(2) to 9.2 +/- 2.4 mm(2) (P <.0001). Similarly, complete stent apposition improved from 33% to 68% of total stents (P <.0001). After initial ICUS, higher-pressure dilations were performed in 40 patients, whereas larger balloons greater than or equal to ICUS reference vessel diameter were used in 33 patients. Follow-up was obtained in 95 (99%) patients. The overall major adverse cardiac event rate at 6 months was 9.3%, which consisted of 8 target vessel revascularizations and 1 abrupt closure requiring repeat intervention. CONCLUSIONS: Even when poststent high-pressure balloon inflation achieves an optimal angiographic result, ICUS assists in optimizing acute gain, symmetry, and apposition of intracoronary stents in approximately 50% of patients. Moreover, ICUS guidance is associated with low rates for target vessel revascularization and major adverse cardiac events at 6-month follow-up.     

Percutaneous transradial coronary palmaz-schatz stent implantation,guided by intravascular ultrasound

Intravascular ultrasound (IVUS) allows accurate assessment of stent deployment, its use being confined to the use of 8 French (F) guiding catheters. We evaluated the feasibility of combining transradial artery Palmaz-Schatz stent implantation through 6F guiding catheters with IVUS for assessment of stent diameter after delivery at moderate inflation pressures (10-12 atmospheres [atm]) with compliant balloons and after high pressure dilatations with balloons of intermediate compliance. In 8 consecutive patients, 12 stents were delivered with Scimed® Express^TM balloon catheters at 10-12 atm followed by IVUS (EndoSonics® CathScanner; Visions® FX 3.5F 20 MHz transducer). An ultrasound study was repeated after high pressure dilatations (16-20 atm) with Schneider® Magical Speedy^TM balloon catheters. The balloon diameters were derived from manufacturer provided specifications. In all patients the transducer could easily be advanced through the guiding catheters. Reference diameter of the stented segment was 3.7 ± 0.5 mm (2.7-4.5) and the diameter of Scimed® Express^TM balloons during inflation was 4.0 ± 0.3 mm (3.6-4.7). Stent diameter was 3.0 ± 0.1 mm (2.8-3.2) (P < 0.001 compared to the reference and the balloon diameter). The diameter of the Schneide® Magical Speedy^TM balloons at secondary dilatations with 16 ± 3 atm (14-20) was 4.1 ± 0.4 mm (3.3-4.5) (P = 0.50 compared to the initial balloon diameter). Final stent diameter was 3.3 ± 0.4 mm (2.9-4.1) (P = 0.02 compared to the initial stent diameter). All stents were symmetrically deployed and well apposed. No damage to vessel or stents was detected after passage of the transducer. Thus ultrasound guided stenting via 6F guiding catheters is feasible, and high pressure dilatations with balloons of intermediate compliance results in better stent expansion than after 10-12 atm inflations with compliant balloon catheters.     

Effects of increasing balloon pressure on mechanism and results of balloon angioplasty for treatment of restenosis after Palmaz-Schatz stent implantation: An angiographic and intravascular ultrasound study

Repeat balloon angioplasty is a widely used therapeutic option for in-stent restenosis, but the optimal balloon inflation pressure has not yet been determined. We used angiography and intravascular ultrasound imaging to assess the mechanism and results of lumen enlargement at various inflation pressures. Thirteen consecutive patients with restenosis post–Palmaz-Schatz stent implantation were submitted to a four-step balloon angioplasty using increasing balloon pressure of 2, 4, 8, and >12 atm. As a global result, the lumen size was only 80% of that observed at stent implantation. Significant changes in angiographic minimal lumen diameter, minimal lumen cross-sectional area, and lumen volume were observed after each step except after the highest-pressure inflation. At low inflation pressure (<8 atm), the decrease in neointimal tissue and the stent over expansion explained the lumen enlargement, whereas after further high inflation pressure (>8 atm), only additional stent over expansion was observed. These results suggest that only moderate balloon inflation pressure (up to 12 atm) is needed for angioplasty of post–Palmaz-Schatz stent restenotic lesions. Cathet. Cardiovasc. Intervent. 46:314–321, 1999. © 1999 Wiley-Liss, Inc.     

Impact of a prolonged delivery inflation time for optimal drug‐eluting stent expansion

Purpose: We examined the importance of prolonged inflation time for optimal sirolimus‐eluting stent (SES) or paclitaxel‐eluting stent (PES) expansion. Methods: Eighty‐one de novo lesions deployed single SES or PES between April 2007 and March 2008 were divided into four groups; group 1: 21 SES deployed at 20 atm × 60 sec, group 2: 20 SES deployed with 2‐step inflation at 20 atm × 60 sec following 20 atm × 20 sec, group 3: 20 PES deployed same as group 1, group 4: 20 PES deployed same as group 2. The minimal lumen diameter (MLD) and stent expansion ratio (SER; stent cross‐ sectional area at lesion/balloon cross‐sectional area which was calculated according to the compliance chart at the same atmosphere as stent deployment) were compared between group 1 and group 2 in SES, between group 3 and group 4 in PES. Results: The MLD of post 60 sec was significantly higher than that of post 20sec (2.84 ± 0.28 mm in group 1, 2.76 ± 0.33 mm in group 2 vs. 2.54 ± 0.33 mm in group 2; P = 0.003, 0.045, respectively and 2.94 ± 0.28 mm in group 3, 3.00 ± 0.34 mm in group 4 vs. 2.69 ± 0.35 mm in group 4; P = 0.022, 0.007, respectively). The SER of post 60 sec was significantly higher than that of post 20 sec (79.3% ± 8.5% in group 1, 80.8% ± 7.8% in group 2 vs. 71.1% ± 10.2% in group 2; P = 0.014, 0.011, respectively and 81.1% ± 7.9% in group 3, 84.3% ± 9.9% in group 4 vs. 72.6% ± 10.5% in group 4, P = 0.011, 0.001, respectively). Conclusion: The prolonged delivery inflation for 60 sec may result in a more optimal stent expansion. It is therefore considered to be a useful method for deploying drug‐eluting stent. © 2008 Wiley‐Liss, Inc.     

Vascular response to sirolimus-eluting stents delivered with a nonaggressive implantation technique: comparison of intravascular ultrasound results from the multicenter, randomized E-SIRIUS, and SIRIUS trials.

BACKGROUND: The effectiveness of SES to reduce the risk of restenosis was initially demonstrated in short lesions using stent implantation with routine pre-dilatation and post-dilatation. This intravascular ultrasound (IVUS) substudy of the E-SIRIUS trial sought to evaluate local arterial responses to sirolimus-eluting stents (SES) delivered with a stent implantation technique allowing direct stenting and only selectively applying high-pressure post-dilatation. METHODS AND RESULTS: IVUS was performed immediately after intervention and at 8-month follow-up in 51 patients randomised to either bare-metal stents (BMS; Bx-Velocitytrade mark; N=20) or SES (Cyphertrade mark N=31). Direct stenting was allowed (24%) and post-dilation was performed only selectively (32%). Lumen dimensions, intimal hyperplasia and vessel remodeling were compared between SES and BMS. Subsequently, results of SES in the E-SIRIUS IVUS substudy (N=31) were compared to those of SES in the IVUS substudy of the SIRIUS trial (N=137). SES in SIRIUS IVUS substudy were delivered with 100% pre-dilatation and 77% post-dilatation. Baseline stent and reference segment measurements were similar between BMS and SES in E-SIRIUS IVUS patients. Using SES there was a 96% reduction in intimal hyperplasia volume within the stented segment (1.8+/-4.9 vs 50.6+/-39.7 mm3, P<0.001) and a significantly larger minimal lumen cross sectional area at 8-month follow-up (4.5+/-1.1 vs 2.3+/-0.9 mm2, P<0.001). No vessel remodeling was observed with the use of SES. The applied stent implantation technique resulted in a minimal stent/reference vessel area ratio of 0.75+/-0.17 in E-SIRIUS SES as compared to 0.84+/-0.23 in SIRIUS SES (P=0.046). Mean intimal hyperplasia cross-sectional area at follow-up was 0.1+/-0.2 mm2 in the SES group of E-SIRIUS and 0.5+/-0.8 mm2 in the SES group of SIRIUS (P=0.003). CONCLUSIONS: An implantation technique of SES which includes direct stenting and minimizes the use of high-pressure post-dilatation results in less optimal stent expansion. However, follow-up results compare very favourable to those of BMS and are characterised by even less intimal hyperplasia than after a more forceful implantation of SES.     

Intravascular ultrasound observations during iliac stent deployment.

BACKGROUND: To evaluate the role of intravascular ultrasound (IVUS) during iliac stent deployment, with comparison of four major types of iliac stents. METHODS: Thirty-eight iliac arteries of 37 patients were observed with intravascular ultrasound after implantation of various stents including Palmaz stents in 10, Memotherm stents in 11, Wallstent in 10, and Strecker stents in 7. Quantitative measurements on ultrasound included the ratio of the short-axial to the long-axial diameters of the stent (symmetry index), the ratio of stent cross-sectional area to that of the reference lumen (expansion index), and stent-to-wall apposition. RESULTS: Intravascular ultrasound revealed significant differences among four major types of iliac stent, in spite of satisfactory angiographic appearances in all patients. It demonstrated significant deformity of the Strecker stent (symmetry index of 0.76-0.09) compared with other stents. The Memotherm stent and the Palmaz stent were superior to other stents in terms of degree of expansion (mean expansion index of 0.87 and 0.82 respectively). Stent cross-sectional area greater than 80% of the reference lumen could be sufficient for iliac stent deployment. The Palmaz stent was superior to other stents in terms of stent-to-wall apposition. CONCLUSIONS: Intravascular ultrasound can provide precise and useful cross-sectional morphological and quantitative information in terms of stent configuration, degree of stent expansion, and stent-to-wall apposition.     

Additional luminal area gain by intravascular ultrasound guidance after coronary stent implantation with high inflation pressure

Aims: Studies by intravascular ultrasound demonstrated inadequate expansion in a large number of stents, which lead to the increase of inflation pressures for stenting. The present study examined whether routine use of high-pressure inflation would be sufficient for an optimum stent expansion without sonographic guidance. Methods and results: Two types of single coronary stents (Palmaz-Schatz in 54, and Wiktor in 25) were implanted with inflation pressures of 16–20 atm in 79 nonocclusive coronary lesions. IVUS before stenting was used in 78% to select the adequate stent size. Intravascular ultrasound after stenting was used to assess the minimum stent area and diameter, the reference areas, and the strut apposition to the vessel wall. The difference between the area of the expanding balloon and the stent area was calculated as the luminal deficit of the stent. Completeness of stent expansion required full strut apposition and lesion coverage, and a minimum stent area that was larger than the distal reference, and larger than 60% of the proximal reference. Intravascular ultrasound before stenting lead to an increase of the stent size in 47%. After high-pressure expansion, even with the optimized balloon size, 8% of stents had struts protruding into the lumen. The stent area (6.87 ± 1.93 mm²) was significantly smaller than both the proximal (9.59 ± 2.91 mm²; p<0.001) and distal reference area (8.23 ± 3.03 mm²; p<0.001). The criteria for complete expansion were met in 48%. The expansion with a larger high-pressure balloon in 28 stents lead to an increase of the stent area by 19% (8.19 ± 2.24; p<0.001), and full stent apposition in all cases. The criteria of stent expansion were met in 82%. A wide range of the luminal deficit upto 48% was observed, which was not related to sonographic lesion characteristics, except in lesions with complete circumferential calcifications. The different stent designs were characterized by a slightly lower luminal deficit in slotted-tube stents (23 ± 13% vs. 28 ± 12%; p=0.11) and a better index of stent symmetry as compared with the coil stent (0.87 ± 0.08 vs. 0.82 ± 0.09; p<0.05). Conclusion: Routine use of high-pressure stent expansion did not lead to a sufficient stent expansion, even when the initial stent size had been guided by intravascular ultrasound. Further stent dilatation with larger balloons under ultrasound guidance would be required to optimize the luminal area gain.     

Intravascular ultrasound-guided stenting in long lesions: an insight into possible mechanisms of restenosis and comparison of angiographic and intravascular ultrasound data from the MUSIC and RENEWAL trials

The high restenosis rates in long stents may be related to suboptimal stent deployment. In an attempt to understand the potential components associated with restenosis in long stents, this study compares angiographic and intravascular ultrasound (IVUS) data from the MUSIC and RENEWAL studies where IVUS was used to optimize stent deployment in short (< 15 mm) and long (> 20 mm) coronary lesions, respectively. The RENEWAL study, a randomized trial, compared the NIR stent and Wallstent in long (> 20 mm) coronary lesions and used on-line visual IVUS criteria to optimize stent expansion. Detailed analysis of IVUS data was performed off line. Angiographic and IVUS data from this study was compared to that from the MUSIC study. Initial stent deployment was deemed optimal by the operator after visual angiographic and IVUS assessment in 50 of 70 lesions. In the remaining 20 lesions further balloon inflations were required to optimize stent apposition that led to an average gain in minimal in-stent luminal area (MISA) of 15.9% (P < 0.01). Off-line IVUS data analysis showed that the number reaching "MUSIC criteria" for optimal stent deployment preredilatation was 8 (11.4%) of 70 and 14 (20%) of 70 postredilatation. The ratio of MISA/MRAprox (mean proximal reference area) was 0.69 in RENEWAL. At 6-month follow-up, the angiographic restenosis rate in RENEWAL was 36% and target lesion revascularization (TLR) rate was 7.8%, compared with MUSIC's 9.7% and 4.5%, respectively. In conclusion, angiographic assessment of stent deployment in long lesions is limited. On-line visual IVUS with further balloon inflations to improve stent apposition led to a significant gain in MISA, but the MISA/MRAprox ratio remained suboptimal. Therefore, suboptimal stent deployment due to constraint by lesion resistance may be an important mechanism underlying the high restenosis rates in long stents.     

Duration of balloon inflation for optimal stent deployment: Five Seconds Is Not Enough

Objectives: To assess the effect of the duration of stent inflation on stent expansion using digital stent enhancement (DSE). Background: Optimal stent expansion and apposition to the vessel wall are of critical importance to optimize the results of percutaneous coronary intervention (PCI). However, it is not known if stent inflation duration impacts on stent expansion. Methods: We performed a prospective cohort study in patients undergoing PCI. Quantitative coronary angiography and DSE data were analyzed. DSE was performed at 5, 15, and 25 sec during stent implantation, after target balloon inflation pressure was achieved. Results: One hundred and four consecutive patients (150 lesions) were enrolled. The mean age was 66.9 ± 11.1 years. Complex lesions (ACC/AHA B2/C) occurred in 26.9%. Stents used: Cypher Select (54.1%), Xience V (30.6%), and Taxus Liberté (15.3%). The minimal stent diameter increased significantly with the duration of stent inflation: 2.60 ± 0.51, 2.76 ± 0.51, and 2.82 ± 0.52 mm at 5, 15, and 25 sec (P < 0.0001). Similarly, maximal stent diameter increased with the duration of stent inflation: 3.21 ± 0.51, 3.32 ± 0.52, and 3.36 ± 0.54 mm (P < 0.0001). The average stent diameter also increased with longer stent inflation (P < 0.0001). Using MUSIC criteria 24.0, 53.3, and 68.0% of stents were appropriately expanded at 5, 15, and 25 sec (P < 0.0001).Conclusions: The duration of stent balloon inflation has a significant impact on stent expansion. Stent deployment for >25 sec is recommended. © 2012 Wiley Periodicals, Inc.     

Standardized angiographically guided over-dilatation of stents using high pressure technique optimize results without increasing risks

BACKGROUND: Routine angio-guided stent deployment results in a relatively high restenosis rate, which is mostly due to stent sub-expansion. Several different intravascular ultrasound (IVUS) criteria for optimal stent deployment have been proposed. A minimal in-stent restenosis and a minimal in-stent lumen area of > or = 9 mm2 have been associated with low rates of restenosis and target lesion revascularization (TLR) at 6 months. The role of high-pressure stent deployment and/or upsizing the post-dilatation balloon has not yet been clarified. The aim of this study was to evaluate the possibility of achieving accepted IVUS criteria safely without IVUS guidance with the combination of high-pressure deployment and post-dilatation with a 0.25 mm oversized balloon. METHODS: Thirty-four stents (26 NIR, 3 AVE GFX, 3 ACS GFX, 1 Bard, 1 Jostent) were implanted in 30 patients until optimal angiographical results were obtained (< 10% residual stenosis visually). Forty percent of the patients had unstable angina pectoris, forty-four percent had complex lesions (B2 and C) and 29% were occlusions. Mean inflation pressure was 12.6 +/- 1.6 atm, mean stent diameter was 3.2+/- 0.4 mm and mean stent length was 15.1+/- 5.4 mm. Post-dilatation was performed with the same stent using a short (compared to the angiographic reference segment), 0.25 mm oversized Scimed Maxxum Energy 3.5 +/- 0.4 mm balloon using high pressure (16.1 +/- 1.7 atm) followed by an off-line IVUS examination of the stents. There was clinical follow-up for 1 year. Results in patients with single-vessel disease were compared with those of non-randomized controls, who were stented with high pressure but without over-dilatation. RESULTS: No stent achieved the nominal diameter, in spite of over-dilatation. Mean minimal stent diameter (MLD) according to IVUS was 2.9 +/- 0.4 mm (92% of the angiographic reference diameter). Mean minimal lumen area (MLA) was 7.7 +/- 2.2 mm2. An in-stent MLA > or = 90% of the distal reference segment (AVID criteria) and an MLA > or = 100% or > or = 90% of the smallest/average reference segment (MUSIC criteria) was found in 67% and 57%, respectively. MLA > or = 9 mm2 was achieved in 38%. All stents had good apposition and obtained a symmetry index > or = 0.7 mm. No acute perforations, dissections or other serious complications occurred during the over-dilatation. At 1 year, five patients had re-angina leading to a new coronary angiography; only 1 patient had a significant in-stent restenosis requiring re-PTCA. Compared to non-overdilated historical controls, the standardized over-dilatation seemed to give a larger MLD (3.0 +/- 0.4 mm vs. 2.7 +/- 0.4 mm; p = 0.03), more patients who fulfilled AVID criteria (70% vs. 32%; p = 0.048) and more stents with MLA > or = 9 mm2 (46% vs. 11%; p = 0.02). CONCLUSION: A standardized 0.25 mm over-dilatation of stents never achieved nominal stent size, but did improve lumen gain and was associated with low target vessel revascularization without adding complications to the routine stenting procedure.     

Incomplete expansion of Palmaz-Schatz stents despite high-pressure implantation technique: impact on target lesion revascularization.

Improved expansion of stents using high-pressure implantation technique with subsequent antiplatelet therapy has improved patient outcome regarding the incidence of subacute stent thrombosis, bleeding complications and restenosis. Whether high-pressure implantation per se guarantees adequate stent expansion remains unclear. The aim of the study was to determine (1) stent expansion after high-pressure implantation technique and (2) whether stent expansion influences rate of target lesion revascularization within 6 months of follow-up. One hundred Palmaz-Schatz stents were implanted in 98 lesions (91 native vessels, 7 graft vessels) of 94 patients using high-pressure implantation technique (balloon pressure 12-20 atm). Stent expansion was investigated using intravascular ultrasound imaging (IVUS). Clinical follow-up of the patients was performed for 6 months. After implantation, stent/mean reference ratio was 0.81 +/- 0.16. Noncompliant balloons used for implantation were chosen by angiographic criteria. Mean balloon/reference ratio was 1.08 +/- 0.22; therefore balloons were not undersized. Additional balloon dilataion using higher pressures and/or larger balloons based on IVUS criteria and subsequent IVUS measurements was performed in 52 patients (55%); in these patients, stent expansion improved from 79 +/- 16 to 91 +/- 15% (mean +/- SD) of average reference areas (p < 0.002). Within the 6 months' clinical follow-up, target lesion revascularization was performed in 19 patients (20%). The only prognostic factors for the development of in-stent restenosis requiring target lesion revascularization were the vessel size (p < 0.05) and the extent of plaque distal to the stents (p < 0.05). Implantation of Palmaz-Schatz stents using high-pressure technique does not guarantee adequate stent expansion. Additional dilatation with higher pressures and/or larger balloons improves stent expansion. The size of the stented vessel and the extent of plaque at the distal stent end (residual outflow stenosis) but not the degree of stent expansion were predictors for target lesion revascularization within 6 months' follow-up.     

The ESSEX (European Scimed Stent Experience) study.

The aim of the study was to assess the safety and feasibility of implantation of the Scimed Radius stent. Secondary objectives were to assess the result of stent placement by quantitative coronary angiography (QCA) and intravascular ultrasound (IVUS). The ESSEX study was a prospective, multicenter, observational study in which candidates for a single elective stent implantation, in a de novo or restenotic lesion, reference diameter 2.75-4.00 mm and target lesion < 14 mm in length, were enrolled. QCA at baseline, postprocedure, and 6-month follow-up was performed. IVUS was used to assess optimal stent implantation. One hundred and three patients were enrolled. Forty-four percent of the patients had unstable angina. Stent implantation was technically successful in all patients. Additional stents were implanted in 17 patients for procedural dissection (16) and spasm (1). Ninety-seven percent of patients were event-free at 1 month and 76% at 6-month follow-up. Angiographic restenosis rates for de novo lesions and for all patients were 19% and 21%, respectively. Clinical events occurred at 1- and 6-month follow-up in 2.9% and 24.3% of patients, respectively. No patients suffered subacute thrombosis. Retrospective analysis of peak balloon inflation pressure (< or = 12 and > 12 atm) as a determinant of clinical, QCA, and IVUS outcomes suggested no benefit or detrimental effect from optimization with high-pressure balloon inflation. Implantation of the self-expanding Radius stent is safe and efficacious. Based on registry data, clinical, angiographic, and IVUS, data comparable with modern balloon-expandable stents were obtained.