Three-dimensional intravascular ultrasonic volumetric quantification of stent recoil and neointimal formation of two new generation tubular stents

Low Cycle Fatigue Study of AISI 316L Cardiovascular Stent for Two Different Designs

The main originality of this work consists in investigating low cycle fatigue of AISI 316L cardiovascular stents under hypertensive loading. For this purpose, two geometries of stents are expanded to various diameters and subjected to hypertensive blood pressure. Based on a combination between the fatigue parameter of Jiang-Sehitoglu and the relationship of Coffin-Manson, a numerical model for the prediction of the number of cycles to crack failure is developed. The stent is found to exhibit a fatigue life reduction with the increase of the expansion diameter due to ratchetting strain. In addition, the location of the failure is independent on the design. However, the U-shape strut permits a better distribution of pressure over the stent strut resulting in a longer fatigue life as compared to the Ω-shape.

Coronary Stent Failure: Fracture, Compression, Recoil, and Prolapse

Current-generation coronary drug-eluting stents are associated with low rates of restenosis and target lesion revascularization. However, several mechanisms of stent failure remain clinically important. Stent fracture may occur in areas of excessive torsion or angulation. Longitudinal stent deformation is related to axial stent compression owing to extrinsic forces or secondary devices that disrupt stent architecture. Stent recoil occurs when a stent does not deploy at its optimal cross-sectional area. Tissue prolapse between stent struts may also predispose patients to adverse outcomes. Prevention, recognition, and treatment of these stent failures are necessary to optimize patient outcomes after percutaneous coronary interventions.

Serial greyscale and radiofrequency intravascular ultrasound assessment of plaque modification and vessel geometry at proximal and distal edges of bare metal and first-generation drug-eluting stents

BACKGROUND

Little is known about the correlation between modifications in plaque composition at stent edges and the changes in vessel geometry. This study sought to evaluate, by serial greyscale intravascular ultrasound (IVUS) and Virtual Histology intravascular ultrasound (VH-IVUS), the modifications in plaque composition at the edges of drug-eluting and bare metal stents and the correlation of these findings with changes in the measurements of vessel, lumen and plaque area at those segments.

METHODS AND RESULTS

Single-centre, prospective and randomised (1:1) evaluation of 40 patients with acute coronary syndrome treated with bare metal (Driver; Medtronic, Santa Clara, CA, USA; n=20 patients) or drug-eluting stents (Cypher; Cordis, Miami Lakes, FL, USA; n=20 patients). IVUS and VH-IVUS assessments were done post-procedure and at nine months. Primary endpoint included the modification in vessel, lumen and plaque area and in the composition of the plaque in the mean time between the baseline and follow-up procedure. At the proximal edge of the vessel treated with the Cypher stent, a trend toward positive vessel remodelling (D=+0.6 mm², p=0.06) was observed while at the distal edge, less plaque growth (D=+0.2 mm² vs. D=+1.1 mm², p<0.001), resulted in a larger lumen area at follow-up. By VH, there was a marked reduction in the percentage of fibrotic tissue and necrotic core at the edges of both stents and a positive correlation was seen between increase in percentage of fibro-fatty component and increase in plaque area (r=0.78, p=0.01).

CONCLUSION

Patients treated with drug-eluting stents (DES) experienced less plaque growth, especially at the distal edge of the stents. Modifications in plaque composition, with increase in fibrofatty tissue component, may partially explain these findings.

Comparison of in vivo eccentricity and symmetry indices between metallic stents and bioresorbable vascular scaffolds: insights from the ABSORB and SPIRIT trials

OBJECTIVE

To compare the geometrical parameters of a bioresorbable vascular scaffold (BVS) with a standard metallic stent.

BACKGROUND

The introduction of polymeric bioresorbable materials in the design of novel coronary scaffolds may affect some geometrical parameters, such as eccentricity and symmetry indices, previously introduced as IVUS criteria for optimal metallic stent deployment.

METHODS

From ABSORB Cohort A, ABSORB Cohort B, SPIRIT I, and SPIRIT II, all patients implanted with BVS 1.0, BVS 1.1, or XIENCE V, respectively and intravascular ultrasound analyses post-implantation were selected. The eccentricity index was calculated frame by frame and expressed as an average per device (minimum diameter/maximum diameter). The symmetry index of the device was reported as ([maximum diameter - minimum diameter]/maximum diameter). Six months major adverse cardiac events (MACE) were analyzed.

RESULTS

A total of 242 patients were selected (BVS 1.0: n = 28, BVS 1.1: n = 94, XIENCE V: n = 120). The BVS exhibited a significantly lower eccentricity index (BVS 1.0: 0.83 ± 0.09; BVS 1.1: 0.85 ± 0.08; XIENCE V: 0.90 ± 0.06; P < 0.01) and a significantly higher symmetry index (BVS 1.0: 0.30 ± 0.07; BVS 1.1: 0.31 ± 0.06, XIENCE V 0.26 ± 0.07; P < 0.01) as compared to the XIENCE V. An inverse correlation was found between the symmetry and eccentricity indices for both (BVS r = -0.69, P < 0.01; XIENCE V r = -0.61, P < 0.01). No differences in MACE were detected between the groups according to their geometrical parameters.

CONCLUSIONS

The introduction of a new polymeric material in the design of BVS resulted in a lower eccentricity index and a higher symmetry index as compared to metallic stents, without detectable impact in MACE, at 6 months.

Stents: material, surface texture and design, in theory and practice

Intravascular stenting has become standard practice in cardiology and interventional radiology. As part of their daily routine, interventional therapists have to choose from more than 50 different coronary stents for the optimal treatment of patients. Striking advances in biomedical engineering have triggered the production of numerous new and improved stent models, whose theoretical benefits have not yet been confirmed by large-scale clinical trials. Selecting appropriate stents for individual patients is frequently subject to the personal and, therefore, subjective experience of the interventional therapist. This paper reviews different stent materials and designs used in current trials and clinical practice. The theoretical benefits of individual parameters are discussed and correlated with up-to-date clinical results, particularly with a view to considering their favourable impact on intervention outcomes.

Single-center randomized evaluation of paclitaxel-eluting versus conventional stent in acute myocardial infarction (SELECTION)

OBJECTIVES

To evaluate the superiority of the paclitaxel-eluting stent (PES) in reducing neointimal hyperplasia (NIH) over its corresponding bare metal stent (BMS) during primary percutaneous coronary intervention (PCI).

BACKGROUND

Primary PCI with stent implantation is the repercussion strategy of choice for ST-elevation myocardial infarction (STEMI); nonetheless restenosis rate is still high. Drug-eluting stents have been proven to reduce restenosis rate in many settings, but their use during primary PCI is still controversial.

METHODS

Consecutive patients with STEMI <12 hours were randomized to receive PES or BMS. The primary end-point was the percentage of the stent volume obstructed by neointimal proliferation (NIH) measured by intravascular ultrasound (IVUS) at a 7-month angiographic follow-up. Secondary end-points were binary restenosis rate and major adverse cardiac events (MACE, i.e., death, nonfatal myocardial infarction, and target lesion revascularization).

RESULTS

Eighty patients with STEMI were randomized into the PES or BMS group. Patients were well matched for baseline characteristics and the index procedure was always successful. In-hospital and 1-month MACE were 2.5% per group. NIH at 7 months was 4.6% versus 20% (P< 0.01), late lumen loss 0.1 versus 1.01 mm (P = 0.01). MACE were 7.5% versus 42.5% (P = 0.001) with no difference in death and recurrent myocardial infarction rates. Late-acquired incomplete stent apposition (ISA) rate was 5.1% versus 2.7% (P = 0.65). One subacute stent thrombosis was reported in each group.

CONCLUSIONS

PES was superior to its corresponding BMS in reducing NIH in the STEMI setting without any increase in early and long-term clinical adverse events.

Relocation of minimal luminal diameter after bare metal and drug-eluting stent implantation: Incidence and impact on angiographic late loss

Late loss (LL) has been a fundamental angiographic end-point in drug-eluting stents (DES) clinical trials. However, calculation of LL may be affected by a mismatch between post-procedure (PO) and follow-up (FU) sites of the minimal lumen diameter (MLD). Our aims were to investigate the incidence and methodological implications of the relocation of MLD after bare metal (BMS), sirolimus-eluting (SES), and paclitaxel-eluting (PES) stent implantation. Data from DIABETES I and II trials, which involved diabetic patients treated with BMS, SES, and PES, were analyzed. Angiographic data with matched projections between PO and 9-month angiographic FU were included. In-stent, in-lesion, and in-segment analyses included conventional and customized sub-segmental (5-mm/subsegment) methodology. MLD relocation was considered when the sites of MLD shifted a distance >> the intrinsic variability of the method. Conventional LL, site matched LL, maximal LL (MaxLL), and average LL (AvgLL) were calculated. Relationships between various LL and 1-year target lesion revascularization (TLR) were investigated. Post MLD was located distally, outside the stent, in > or =65% of the analyses. At FU, MLD relocation occurred in 70.5% (BMS), 40% (SES), and 35% (PES). MLD shifted > or =11 mm on average, mainly towards the stented segment. MLD relocation still occurred in 42.8% (BMS), 33.7% (SES), and 36.4% (PES), when analysis was restricted to in-stent segment. Among LL measurements, MaxLL showed the best association with TLR rates. Relocation of the MLD is a frequent phenomenon after both BMS and DES, and should be taken into account when calculating LL. Comprehensive LL analyses, including MaxLL and AvgLL, provides a better appraisal of the biological and clinical effectiveness of DES.

Impact of stent design on clinical outcome after coronary stent implantation

Coronary stents have considerably improved both immediate and late results after coronary angioplasty, by limiting elastic recoil and vascular remodeling, but their use does not eliminate restenosis, caused mainly by neointimal hyperplasia. Stents are now implanted in over 70% of percutaneous coronary interventions. More than 50 coronary stents have already been approved in Europe and over 20 stents are commercially available in the USA, raising the question: which device is best suitable for which lesion? Several in vitro experiments revealed significant differences in expansion characteristics of coronary stents, related to the strut design and metallic composition. Animal studies were performed to determine the influence of stent design on the patterns and extent of neointimal hyperplasia. However, the clinical results of randomized trials comparing stent types in humans have not always reflected laboratory findings. This article is a critical overview of experimental and clinical data concerning the impact of stent design on the early and late clinical outcome after coronary stent implantation.

Intravascular ultrasound characterization of the "black hole" phenomenon after drug-eluting stent implantation

An intraluminal echolucent tissue, dubbed "black hole," has been identified by intravascular ultrasonography after intracoronary brachytherapy. This study reports the characteristics and incidence of the black hole in patients treated with drug-eluting stent implantation using a sirolimus-eluting stent (SES). We included intravascular ultrasound data from the Compassionate Use of Sirolimus-Eluting Stent (SECURE, n = 61 lesions) registry, a study involving patients in whom previous brachytherapy had failed, and the DIABETES trial (n = 165 lesions), a multicenter, randomized study comparing SES versus bare metal stents in diabetic patients. Intravascular ultrasound follow-up was scheduled at 8 months (SECURE trial, post-brachytherapy population) and 9 months (DIABETES trial). In the SECURE population, a black hole was observed in 10 patients (19.6%). Seven black hole segments had significant intimal hyperplasia (> 10%). A black hole accounted for 27% of total intraluminal tissue. In the DIABETES trial, 2 patients (2.5%) in the SES group and none in the bare metal stent group showed echolucent intimal hyperplasia. In conclusion, a black hole occurred frequently after implantation of a SES in patients in whom intracoronary brachytherapy had previously failed. Black holes were also identified in a nonirradiated population, although the incidence was lower than in the post-brachytherapy patients. Bare metal stents were not associated with this phenomenon.

Efficacy and safety of oral sirolimus to inhibit in-stent intimal hyperplasia

Sirolimus systemic administration has shown marked inhibition of neointimal hyperplasia (NIH) after balloon angioplasty in porcine models. In this pilot study, we tested the hypothesis that oral sirolimus is safe and effective to inhibit in-stent NIH and therefore to prevent and treat in-stent restenosis (ISR). Twelve patients (18 lesions) with high risk for ISR, including 8 ISR lesions, were admitted. One day before the procedure, patients were given a 15 mg loading dose of oral sirolimus, followed by 5 mg daily for 28 days, with weekly whole blood level measurements. The daily dose was adjusted to keep the concentration at 10-15 ng/ml. Sirolimus was well tolerated by all patients but one, who died at the end of the third week of treatment. The 4- and 8-month follow-up revealed an angiographic late loss of 0.40 +/- 0.24 and 0.67 +/- 0.45 mm (P < 0.01), respectively. At the same time points, the intravascular ultrasound in in-stent relative volumetric obstruction was 14.4% +/- 9.1% and 23.2% +/- 10.1% (P < 0.01), respectively. At 24-month clinical follow-up, adverse events were one (8.3%) death, two (11.1%) target lesion, and four (22.2%) target vessel revascularizations. In conclusion, in this small group of high-risk ISR patients, oral sirolimus inhibited NIH and therefore may be an effective strategy for the prevention and treatment of ISR.

Determinants of Stent Expansion in Curved Stenotic Lesions: An In Vitro Experimental Study

PURPOSE

This study compared the expansion parameters of four different new-generation balloon-expandable stents in a curved stenotic phantom model.

MATERIALS AND METHODS

Five stents for each length and type, each with a 3.5-mm diameter (AVE, 12 mm and 18 mm; Penta, 13 mm and 18 mm; BX-Sonic, 13 mm and 18 mm; and Jostent Flex Master, 12 mm and 16 mm), were implanted in curved silicon models 3.25 mm in diameter with 58% concentric elastic stenoses. The forces exerted on the inner curvature were continuously registered. Minimal luminal diameter (MLD) and reference luminal diameter (RLD) of the stents, inflated balloon diameter at both ends of the stents during inflation (BD(ref)), and balloon diameter at the stenotic site during inflation (BD(min)) were determined by magnification radiography.

RESULTS

The Penta and AVE stents presented greater RLD (Penta, 3.78 mm +/- 0.08; AVE, 3.75 mm +/- 0.13; BX-Sonic, 3.47 mm +/- 0.06; Jostent, 3.28 mm +/- 0.06) and MLD values (Penta, 2.94 mm +/- 0.18; AVE, 3.05 mm +/- 0.19; BX-Sonic, 2.68 mm +/- 0.06; Jostent, 2.53 mm +/- 0.09) than the BX-Sonic and Jostent stents. Displacement forces after stent placement were greater for AVE (0.034 N +/- 0.015) and Penta stents (0.023 N +/- 0.017) than for BX-Sonic (0.013 N +/- 0.007) and Jostent stents (0.009 N +/- 0.007; P <.05). BD(min) was correlated in a linear fashion with MLD (r = 0.84; P <.001), as was BD(ref) with RLD (r = 0.92; P <.001), for all stents.

CONCLUSIONS

Inflated balloon diameter was the main determinant of stent expansion. The AVE and Penta stents gained larger MLD values than the BX-Sonic and Jostent stents, but they excessively dilated the nonstenotic region of the model.

First human experience with the 17-beta-estradiol–eluting stent

OBJECTIVES

The purpose of the study was to examine the safety and efficacy of 17-beta-estradiol-eluting stent implantation on coronary de novo lesions.

BACKGROUND

Recent animal data indicate that local delivery of 17-beta-estradiol promotes re-endothelialization, inhibits cell migration and proliferation, and prevents restenosis.

METHODS

A total of 30 consecutive patients underwent 17-beta-estradiol-eluting BiodVysio (Biocompatibles Ltd., London, United Kingdom) stent implantation for the treatment of coronary de novo lesions. Clinical, angiographic, and intravascular ultrasound (IVUS) analysis was performed at six-month follow-up.

RESULTS

All stents were successfully deployed and patients were discharged home without clinical events. A total of two patients exceeded 50% intra-stent narrowing by angiography, whereas no patients experienced edge restenosis. One patient had focal intra-stent restenosis (60% diameter stenosis) with no symptoms and negative stress test, whereas the other patient had diffuse restenosis, requiring target vessel revascularization. No other patient experienced any major adverse cardiac event. Follow-up IVUS revealed a neointimal hyperplasia volume of 32.3 +/- 16.4 mm(3), whereas the stent volume was 143.7 +/- 43.7 mm(3), resulting in a neointimal volume obstruction of 23.5 +/- 12.5%. None of the patients had > or =50% volume obstruction by IVUS.

CONCLUSIONS

Implantation of 17-beta-estradiol-eluted BiodVysio stents appears feasible and safe, showing low rates of binary restenosis and revascularization. These results warrant further confirmation with a large, randomized multicenter trial.

Randomized study to assess the effectiveness of slow- and moderate-release polymer-based paclitaxel-eluting stents for coronary artery lesions

BACKGROUND

Early clinical studies demonstrated the feasibility of local paclitaxel delivery in reducing restenosis after treatment of de novo coronary lesions in small patient populations.

METHODS AND RESULTS

We conducted a randomized, double-blind trial of 536 patients at 38 medical centers evaluating slow-release (SR) and moderate-release (MR) formulations of a polymer-based paclitaxel-eluting stent (TAXUS) for revascularization of single, primary lesions in native coronary arteries. Cohort I compared TAXUS-SR with control stents, and Cohort II compared TAXUS-MR with a second control group. The primary end point was 6-month percent in-stent net volume obstruction measured by intravascular ultrasound. Secondary end points were 6-month angiographic restenosis and 6- and 12-month incidence of major adverse cardiac events, a composite of cardiac death, myocardial infarction, and repeat revascularization. At 6 months, percent net volume obstruction within the stent was significantly lower for TAXUS stents (7.9% SR and 7.8% MR) than for respective controls (23.2% and 20.5%; P<0.0001 for both). This corresponded with a reduction in angiographic restenosis from 17.9% to 2.3% in the SR cohort (P<0.0001) and from 20.2% to 4.7% in the MR cohort (P=0.0002). The incidence of major adverse cardiac events at 12 months was significantly lower (P=0.0192) in the TAXUS-SR (10.9%) and TAXUS-MR (9.9%) groups than in controls (22.0% and 21.4%, respectively), predominantly because of a significant reduction in repeat revascularization of the target lesion in TAXUS-treated patients.

CONCLUSIONS

Compared with a bare metal stent, paclitaxel-eluting stents reduced in-stent neointimal formation and restenosis and improved 12-month clinical outcome of patients with single de novo coronary lesions.

Preintervention arterial remodeling affects vessel stretch and plaque extrusion during coronary stent deployment as demonstrated by three-dimensional intravascular ultrasound

The mechanisms of lumen enlargement during stent implantation may be significantly affected by arterial remodeling. To assess effects of lesion remodeling, we performed 3-dimensional intravascular ultrasound (IVUS) analyses in 55 coronary lesions before and after deployment of balloon-expandable stents. Standard quantitative analysis was performed, and arterial remodeling was assessed by the remodeling index (target site divided by mean of proximal and distal reference segment vessel areas), which classified lesions into group A (remodeling index < or =1, negative or intermediate remodeling, n = 40) or group B (remodeling index >1, positive remodeling, n = 15) lesions. Characteristics of the 55 patients and the interventional procedures were similar in the 2 groups. IVUS demonstrated that stenting resulted in increased lumen and vessel dimensions and in a reduced plaque size (p < or =0.001 each) in both group A and group B lesions. The extent of lumen increase inside the stents was almost identical, but resulted from different mechanisms: (1) vessel stretch was greater in group A (p <0.002 at minimum lumen site); (2) plaque compression (or embolization) tended to be greater in group B (p = 0.05, along entire stented segment); (3) plaque redistribution within the stent was observed in both groups (p <0.005 both); and (4) significant (p <0.01) plaque extrusion into the distal reference segment was found in group B only. Thus, the remodeling pattern of coronary lesions has a significant impact on the mechanisms of lumen enlargement during stent deployment. Lesions with positive remodeling show more plaque extrusion into the distal reference and less stent-induced vessel stretch than those with negative remodeling.

Impact of moderate lesion calcium on mechanisms of coronary stenting as assessed with three-dimensional intravascular ultrasound in vivo

Axial plaque redistribution is an important mechanism of lumen enlargement after stenting of noncalcified lesions. To assess effects of lesion calcification on mechanisms of coronary stenting, we analyzed 55 lesions with noncircumferential calcification with 3-dimensional intravascular ultrasound (IVUS) (standard qualitative and quantitative analyses) before and after implantation of balloon-expandable stents. Thirty-two plaques (58%) showed arcs of calcium <120 degrees of vessel circumference (group A), whereas 23 lesions (42%) contained arcs of calcium > or =120 degrees of vessel circumference (group B). In the entire cohort of 55 lesions, as well as groups A and B, which were studied separately, both single-slice IVUS analysis (performed at minimum lumen site before intervention) and mean stented segment IVUS analysis showed an increase in lumen and vessel area and a decrease in plaque area (p <0.001). The magnitude of lumen and vessel increase and of plaque decrease was similar in both groups. Group A lesions showed significant plaque extrusion into the distal reference segment that was not observed in group B (increase in plaque area of 1.3 +/- 1.9 vs 0.1 +/- 2.0 mm(2), p <0.04). Stenting did not alter plaque area of the proximal reference segment in either group. In addition, there was an increase in vessel area of the distal reference of both groups, indicating that stent-induced vessel expansion observed within the lesion also affected the distal reference. Thus, longitudinal plaque redistribution and vessel expansion contribute to increased lumen dimensions during stenting of lesions with varying amounts of calcium; however, marked plaque extrusion was found only in lesions with a calcium arc of <120 degrees.

Neointima in coronary stent does not increase during over 1-year in non-restenosed lesion at 6 months follow-up: serial volumetric intravascular ultrasound study

The long-term outcomes of coronary artery stenting have been determined by coronary angiography only with has the limitation of determining stent expansion and neointimal proliferation at long-term follow-up. Volumetric intravascular analysis has the potential to evaluate the morphology and distribution of neointima longitudinally after coronary artery stenting. We used three-dimensional intravascular ultrasound (3-D IVUS) to evaluate serial changes in stent and neointimal volumes for over 1-year in 9 patients who did not exhibit angiographic restenosis at 6-month follow-up. Volumetric analysis by a validated Netra 3-D IVUS system was performed pre- and post-intervention, at 6-month follow-up (FU1), and at over one-year follow-up (FU2). Lumen volume in the stented lesions increased significantly after intervention, and the increase persisted until FU2. There were no significant changes in stent volume between just after stent implantation and at FU2. Neointimal volume within the stents did not change from FUI to FU2 (FU1; 38.4 +/- 9.0 mm3 vs FU2; 33.8 +/- 10.3 mm3). In 33% (3/9) of all lesions, neointimal volume increased between from 6-months to over 1-year after stent implantation. Neointimal distribution after stenting seemed to be almost equal and unrelated to the plaque burden at pre-intervention. Neointimal volume within the stents did not increase and stent volume did not change over the 1st-year in patients who did not exhibit angiographic restenosis at 6-months.

The contribution of "mechanical" problems to in-stent restenosis: An intravascular ultrasonographic analysis of 1090 consecutive in-stent restenosis lesions

OBJECTIVES

Serial intravascular ultrasonographic (IVUS) studies have shown that in-stent restenosis is the result of intimal hyperplasia (IH). However, routine preintervention IVUS imaging has suggested that many restenotic stents were inadequately deployed. The purpose of this IVUS study was to determine the incidence of mechanical problems contributing to in-stent restenosis (ISR).

METHODS

Between April 1994 and June 2000, 1090 patients with ISR were treated at the Washington Hospital Center. All underwent preintervention IVUS imaging. IVUS measurements included proximal and distal reference lumen areas and diameters; stent, minimum lumen, and IH (stent minus lumen) areas; and IH burden (IH/stent area).

RESULTS

In 49 ISR lesions (4.5%), there were morphologic findings that contributed to the restenosis. These were termed mechanical complications. Examples include (1) missing the lesion (eg, an aorto-ostial stenosis), (2) stent "crush," and (3) having the stent stripped off the balloon during the implantation procedure. Excluding mechanical complications, stent underexpansion was common. In 20% of the ISR cases the stents had a cross-sectional area (CSA) at the site of the lesion <80% of the average reference lumen area. Twenty percent of lesions had a minimum stent area <5.0 mm(2) and an additional 18% had a minimum stent area of 5.0 to 6.0 mm(2). Twenty-four percent of lesions had an IH burden <60%.

CONCLUSION

Mechanical problems related to stent deployment procedures contribute to a significant minority of ISR lesions (approximately 25%).

Sustained suppression of neointimal proliferation by sirolimus-eluting stents: one-year angiographic and intravascular ultrasound follow-up

BACKGROUND

We have previously reported a virtual absence of neointimal hyperplasia 4 months after implantation of sirolimus-eluting stents. The aim of the present investigation was to determine whether these results are sustained over a period of 1 year.

METHODS AND RESULTS

Forty-five patients with de novo coronary disease were successfully treated with the implantation of a single sirolimus-eluting Bx VELOCITY stent in São Paulo, Brazil (n=30, 15 fast release [group I, GI] and 15 slow release [GII]) and Rotterdam, The Netherlands (15 slow release, GIII). Angiographic and volumetric intravascular ultrasound (IVUS) follow-up was obtained at 4 and 12 months (GI and GII) and 6 months (GIII). In-stent minimal lumen diameter and percent diameter stenosis remained essentially unchanged in all groups (at 12 months, GI and GII; at 6 months, GIII). Follow-up in-lesion minimal lumen diameter was 2.28 mm (GIII), 2.32 mm (GI), and 2.48 mm (GII). No patient approached the >/=50% diameter stenosis at 1 year by angiography or IVUS assessment, and no edge restenosis was observed. Neointimal hyperplasia, as detected by IVUS, was virtually absent at 6 months (2+/-5% obstruction volume, GIII) and at 12 months (GI=2+/-5% and GII=2+/-3%).

CONCLUSIONS

This study demonstrates a sustained suppression of neointimal proliferation by sirolimus-eluting Bx VELOCITY stents 1 year after implantation.

Extent and distribution of in-stent intimal hyperplasia and edge effect in a non-radiation stent population

Intimal hyperplasia within the body of the stent is the primary mechanism for in-stent restenosis; however, stent edge restenosis has been described after brachytherapy. Our current understanding about the magnitude of in vivo intimal hyperplasia and edge restenosis is limited to data obtained primarily from select, symptomatic patients requiring repeat angiography. The purpose of this study was to determine the extent and distribution of intimal hyperplasia both within the stent and along the stent edge in relatively nonselect, asymptomatic patients scheduled for 6-month intravascular ultrasound (IVUS) as part of a multicenter trial: Heparin Infusion Prior to Stenting. Planar IVUS measurements 1 mm apart were obtained throughout the stent and over a length of 10 mm proximal and distal to the stent at index and follow-up. Of the 179 patients enrolled, 140 returned for repeat angiography and IVUS at 6.4 +/- 1.9 months and had IVUS images adequate for analysis. Patients had 1.2 +/- 0.6 Palmaz-Schatz stents per vessel. There was a wide individual variation of intimal hyperplasia distribution within the stent and no mean predilection for any location. At 6 months, intimal hyperplasia occupied 29.3 +/- 16.2% of the stent volume on average. Lumen loss within 2 mm of the stent edge was due primarily to intimal proliferation. Beyond 2 mm, negative remodeling contributed more to lumen loss. Gender, age, vessel location, index plaque burden, hypercholesterolemia, diabetes, and tobacco did not predict luminal narrowing at the stent edges, but diabetes, unstable angina at presentation, and lesion length were predictive of in-stent intimal hyperplasia. In a non-radiation stent population, 29% of the stent volume is filled with intimal hyperplasia at 6 months. Lumen loss at the stent edge is due primarily to intimal proliferation.

Why and how to avoid stenting during brachytherapy

Intracoronary radiation is a promising therapy to reduce restenosis after percutaneous coronary intervention. It may be anticipated that radiation and intracoronary stents - the current standard coronary revascularization procedure - have a synergic antirestenosis effect. However, this potential benefit has not been proven in the clinical scenario. Indeed, this combined approach (stenting plus brachytherapy) may even be harmful. Delayed endothelialization and late stent malapposition are important drawbacks of implanting a metallic prosthesis in the setting of radiation therapy. Owing to the relatively high frequency of late thrombosis after stenting irradiated coronary arteries, the Food and Drug Administration required that the labeling of both gamma- and beta-radiation devices recently approved for clinical use explicitly advise avoidance of the placement of new stents. The pathophysiologic aspects as well as the clinical implications of the implantation of a new stent in association with radiation delivered by radioactive stents or catheter-based systems are discussed in this paper.

Acute stent recoil: in vivo evaluation of different stent designs

This study sought to investigate the degree of acute recoil of four different stents by means of quantitative coronary angiography. Four hundred and six patients underwent stent implantation for single discrete coronary artery lesion: 105 received a 16 mm Paragon stent, 112 an 18 mm Multilink Duet, 97 a 16 mm NIR Primo stent, and 92 a 15 or 18 mm NIR Royal Advance. Elastic recoil was defined as the difference between mean balloon cross-sectional area (CSA) at the highest pressure and mean CSA after PTCA. The mean stent recoil was 13% +/- 10% CSA (P < 0.001), being statistically greater for the nitinol Paragon stent (21% +/- 11%), intermediate for the multicellular Multilink Duet stent (14% +/- 7%), and minimum for the NIR family (9% +/- 6% and 8% +/- 7%, respectively). The recoil was not homogeneously distributed along the stent length but was lower at the two ends (11% +/- 12% and 13% +/- 11%) and highest in the central part (15% +/- 12%)(P < 0.001). Thus, acute recoil is a significant phenomenon regardless of the mechanical properties and design of new-generation tubular stents.

Lack of neointimal proliferation after implantation of sirolimus-coated stents in human coronary arteries: a quantitative coronary angiography and three-dimensional intravascular ultrasound study

BACKGROUND

Restenosis remains an important limitation of interventional cardiology. Therefore, we aimed to determine the safety and efficacy of sirolimus (a cell-cycle inhibitor)-coated BX Velocity stents.

METHODS AND RESULTS

Thirty patients with angina pectoris were electively treated with 2 different formulations of sirolimus-coated stents (slow release [SR], n=15, and fast release [FR], n=15). All stents were successfully delivered, and patients were discharged without clinical complications. Independent core laboratories analyzed angiographic and 3D volumetric intravascular ultrasound data (immediately after procedure and at 4-month follow-up). Eight-month clinical follow-up was obtained for all patients. There was minimal neointimal hyperplasia in both groups (11.0+/-3.0% in the SR group and 10.4+/-3.0% in the FR group, P:=NS) by ultrasound and quantitative coronary angiography (in-stent late loss, 0.09+/-0.3 mm [SR] and -0.02+/-0.3 mm [FR]; in-lesion late loss, 0.16+/-0.3 mm [SR] and -0.1+/-0.3 mm [FR]). No in-stent or edge restenosis (diameter stenosis >or=50%) was observed. No major clinical events (stent thrombosis, repeat revascularization, myocardial infarction, or death) had occurred by 8 months.

CONCLUSIONS

The implantation of sirolimus-coated BX Velocity stents is feasible and safe and elicits minimal neointimal proliferation. Additional placebo-controlled trials are required to confirm these promising results.