Intravascular ultrasound findings in the multicenter, randomized, double-blind RAVEL (RAndomized study with the sirolimus-eluting VElocity balloon-expandable stent in the treatment of patients with de novo native coronary artery Lesions) trial

Localized Hypersensitivity and Late Coronary Thrombosis Secondary to a Sirolimus-Eluting Stent

Background— The US Food and Drug Administration recently issued a warning of subacute thrombosis and hypersensitivity reactions to sirolimus-eluting stents (Cypher). The cause and incidence of these events have not been determined.

Methods and Results— We present findings of a 58-year-old man who died of late stent thrombosis 18 months after receiving 2 Cypher stents for unstable angina. Although angiographic and intravascular ultrasound results at 8 months demonstrated the absence of neointimal formation, vessel enlargement was present. An autopsy showed aneurysmal dilation of the stented arterial segments with a severe localized hypersensitivity reaction consisting predominantly of T lymphocytes and eosinophils.

Conclusions— The known pharmacokinetic elution profile of Cypher stents and the presence of polymer fragments surrounded by giant cells and eosinophils suggest that a reaction to the polymer may have caused late stent thrombosis. Careful long-term follow-up of patients with vessel enlargement after Cypher stent placement is recommended.

Antiproliferative coatings for the treatment of coronary heart disease:. what are the targets and which are the tools?

Since the advent of percutaneous coronary intervention (PCI) for stenosing coronary disease, restenosis has remained a clinical problem. Despite the emergence and evolution of coronary stents, the rate of restenosis following PCI is still 10-20%, and above 50% in high risk subgroups. With increased understanding of the pathophysiology of this process, a number of potential therapeutic targets have been identified, allowing the development of novel therapies against restenosis, which can now be delivered locally using stent platforms. Some of the reported clinical trial data utilizing drug-eluting stents (DES) have produced such profound reductions in clinical and angiographic restenosis that we have been tempted to believe we are on the brink of eradicating this process completely. As the initial excitement subsides, however, there is a need to decide whether these tools will remain effective in real-world interventional practice. In this article we review the pathophysiology of the restenotic process, and the biological targets of the DES therapies currently available in clinical practice. We attempt to define clinical target populations for DES therapy, and assess the impact on outcomes thus far. We consider the advantages that newly emergent stent coatings might offer, and whether targeting specific patient subgroups with unique antiproliferative agents may provide the best chance of limiting restenosis in high risk subgroups. Finally, we consider future strategies to prevent restenosis, with a movement away from the antiproliferative approach, and toward accelerating endothelialization.

Paradigm shifts in cardiovascular medicine

Cardiovascular medicine is changing rapidly with the development, testing, and introduction of new diagnostic and therapeutic methods. New interventional techniques such as the use of drug-eluting stents have important implications for the care of individual patients and the delivery and economics of health care in general. Drug-eluting stents have been shown to improve outcomes among patients undergoing percutaneous coronary intervention by significantly reducing restenosis rates. Two randomized trials have documented that per 100 patients treated with the sirolimus drug-eluting stent, 12.5 to 13.6 patients avoided the need for subsequent target lesion revascularization, when compared with patients treated with conventional stents. The economic effect of the introduction of these stents, which are projected to be two to three times as expensive as conventional stents, is complex and depends on which segment of health care is considered. These stents will be favorably received by patients, physicians, employers, and society as well as payers. However, hospitals may be adversely affected by having increased procedural costs for the stents, along with fewer procedures for evaluation and treatment of restenosis and probably decreased surgical volumes. Drug-eluting stents are only the first of many new technologic advances that will affect cardiovascular care. These procedures have many features in common, including: 1). replacement of major surgical procedures with less invasive approaches; and 2). redistribution of costs, with a decrease in hospital profits but potentially lower costs of health care delivery for society as a whole.

Requirements for quantitative analysis of intimal reaction in arteries treated with intraluminal stents

PURPOSE

To assess the reliability of quantitative histomorphometry measurements for the intimal reaction that occurs after intraluminal stenting in an animal model.

METHODS

Two self-expanding intravascular stents, a biodegradable poly-D/L-lactic acid (PLA) stent and a stainless steel Wallstent, were implanted in the common iliac arteries of a beagle dog. After 45 days, the histomorphometry of the stented iliac artery segments was quantitatively measured. The relative standard error (RSE) of the estimate was calculated, and the reliability of measurements for maximal (LDmax) and minimal (LDmin) luminal diameters and internal (IELT) and external (EELT) elastic lamina thicknesses was assessed.

RESULTS

The PLA stent required more measurements of variables from a single slide to ensure reliable (RSE<10%) results (1 for LDmax, 1 for LDmin, 8 for IELT, and 4 for EELT) compared to the Wallstent (1 for LDmax, 1 for LDmin, 2 for IELT, and 2 for EELT 2). The measured results were reliable for both stent materials when variables were measured from 2 slides of each segment (proximal/central/distal) of the stent.

CONCLUSIONS

We conclude that these preliminary measurements to estimate the reliability of quantitative histomorphometry measurements should be made and reported before final results are given.

Treating Intractable Venous Stenosis: Present and Future Therapy

The widespread use of percutaneous angioplasty for venous stenoses has lengthened the functional life span of hemodialysis access, while preserving precious venous capital. A subset of dialysis patients with dysfunctional access sites will harbor stenoses which are intractable, in that they fail to respond to conventional balloon angioplasty or recur in the weeks following angioplasty. This editorial discusses various endovascular approaches to the management of intractable venous stenosis as well as promising future therapies.

Late neointimal tissue growth behind the stent after intravascular γ-radiation

PURPOSE

To determine the nature of the changes of the vascular wall after intravascular brachytherapy in stented arteries leading to incomplete stent apposition.

METHODS AND MATERIALS

Stents were implanted in the infrarenal aortas of rabbits, and gamma-intravascular brachytherapy (18 Gy) or a sham radiation procedure was immediately implemented. The arteries were harvested at 6 months for histologic analyses.

RESULTS

The external elastic lamina area, as well as the vascular wall area behind the stent, were significantly greater in irradiated vs. control arteries (8.94 +/- 0.68 mm2 vs. 6.87 +/- 0.40 mm2 [p <0.001] and 1.56 +/- 0.13 mm2 vs. 0.72 +/- 0.07 mm2 [p <0.001], respectively). The ratio of the intimal area behind the stent related to the total intimal area was greater in the irradiated segments (control vs. irradiated: 9.0% +/- 5.9% vs. 55.3% +/- 15.5%, p <0.05). Neointimal growth of the irradiated vessels outside the stent was characterized by marked fibrin depositions and an inflammatory response around the stent struts.

CONCLUSION

Our study revealed the presence of a neointimal layer specifically located behind the stent, which represented the result of an unhealed fibrin-rich tissue growth process 6 months after intravascular brachytherapy.

Kissing sirolimus-eluting stents for the treatment of left main coronary artery stenosis

We present a case of kissing drug-eluting stent deployment in the left main coronary artery in a 43-year-old male with failed previous bypass grafting. We discuss the technique used for stent deployment and the rationale for using this technique in the drug-eluting stent era.

Predictors of Restenosis After Implantation of 2.5 mm Stents in Small Coronary Arteries

BACKGROUND

The results of stent implantation for small coronary disease have been inconclusive. The purpose of the present study was to evaluate the factors in predicting the risk of angiographic restenosis after 2.5-mm stent implantation for small coronary arteries.

METHODS AND RESULTS

The study group comprised 134 consecutive patients who had a reference small coronary artery with diameter from 1.8 mm to 2.5 mm on quantitative coronary angiography and who had been successfully treated by stent implantation with a 2.5-mm stent. Of the 134 patients, 55 had angiographic restenosis (41%). The rate of target lesion revascularization was 32%. Diabetes mellitus, acute coronary syndrome, lesion length, bifurcation lesion, lower left ventricular ejection fraction (LVEF), stent strut, stent/artery ratio, and stent length were identified as predictors of restenosis by univariate analysis. Subsequent multivariate analysis revealed that lower LVEF (odds ratio (OR) 3.37, p=0.01), bifurcation lesion (OR 2.47, p=0.04), thicker stent strut (OR 2.30, p=0.04), and longer stent length (OR 1.05, p=0.02) were significant predictors of restenosis.

CONCLUSIONS

Two pre-interventional factors (reduced left ventricular function and bifurcated lesion) and 2 procedure-related factors (thickness of stent strut and total stent length) were identified as predictors of restenosis. These factors should be taken into account when deciding on the percutaneous coronary intervention strategy for small coronary artery disease.

Retroinfusion-supported stenting in high-risk patients for percutaneous intervention and bypass surgery: Results of the prospective randomized myoprotect I study

The objective of this study was to assess event-free survival and total treatment costs of retroinfusion-supported stenting in high-risk patients compared to bypass surgery. An increasing number of patients with main-stem and main-stem-equivalent stenosis are treated by stent implantation, which appears to be safe in the short-term follow-up. However, there is a lack of randomized studies comparing conventional bypass surgery with stent implantation, particularly in patients with high risk for both treatments. We here report on the 1-year results of a prospective randomized single-center study in patients with symptomatic main-stem and main-stem-equivalent lesions with substantially increased risk for bypass surgery. Patients where randomized to undergo either percutaneous transluminal coronary angioplasty/stent procedure (n = 23) or bypass surgery (n = 21). Patients randomized to stent implantation were supported by selective pressure-regulated retroinfusion of the anterior cardiac vein during ischemia. Patients of the stent group and the bypass group did not differ in baseline characteristics, including Parsonnet score and quality-of-life score. Twenty-eight-day mortality and 1-year mortality rate as well as quality-of-life scores were similar in both groups. Event-free survival after 1 year was higher in the bypass group (71.4% vs. 52.3%; P = 0.02) due to a lower target lesion revascularization rate. With regard to total treatment costs, however, the stent group compared favorably to the bypass group (9,346 +/- 807 vs. 26,874 +/- 3,985 euro), predominantly as a result of a shorter intensive care and hospital stay. In this first randomized study in high-risk patients for stent implantation and bypass surgery, patients with retroinfusion-supported stent implantation had a similar 1-year outcome and quality of life compared to patients with bypass surgery. Though in the stent group event-free survival was lower and target lesion revascularization rate was higher, retroinfusion-supported stent implantation was associated with substantially lower costs and might be considered as an alternative treatment option in this selected group of high-risk patients.

Usefulness of residual percent plaque area after percutaneous coronary intervention in predicting peristent positive remodeling

The aim of this study was to determine whether a stented coronary artery might be positively remodeled, which factors predict this phenomenon, and whether positive remodeling has an association with late outcome. The study population consisted of 230 lesions in 230 patients who received bare-metal stents. We performed intravascular ultrasound analyses before and after the procedure and at follow-up. An artery was defined as positively remodeled if the ratio of follow-up to postvessel area was > or =1.1. The following indexes were calculated and defined: (1) late loss = postluminal area - follow-up luminal area; (2) percent plaque area = ([vessel area - luminal area]/vessel area x 100), (3) Delta% plaque area = follow-up percent plaque area - postprocedure percent plaque area. Although late loss in the positively remodeled group was significantly smaller than that in the nonremodeled group (p<0.05), d% plaque area in the former group was significantly larger than that in the latter group (p<0.05). The rate of restenosis in the positive remodeling group (16.4%) was significantly lower than that in the nonremodeling group (28.2%) (p<0.05). In multivariate analysis, postprocedure percent plaque area was the only powerful independent predictor for peristent positive remodeling and was inversely associated with this phenomenon in both groups (odds ratio 0.944, 95% confidence interval 0.914 to 0.975, p=0.0004). This study indicates that postprocedure percent plaque area could predict the occurrence of peristent positive remodeling at follow-up and that this phenomenon might influence late outcome.

Long-Term Follow-Up of Incomplete Stent Apposition in Patients Who Received Sirolimus-Eluting Stent for De Novo Coronary Lesions

Background— Incomplete stent apposition (ISA) has been previously documented after sirolimus-eluting stent (SES) implantation. The aim of this study was to investigate the long-term intravascular ultrasound (IVUS) findings of ISA in patients who received SES.

Methods and Results— A total of 13 patients who received SES and showed ISA at follow-up IVUS (follow-up I) were investigated. IVUS was performed on all of these patients 12 months later (follow-up II). Quantitative ISA area measurement was also performed at follow-up I and II. No vascular remodeling was observed in the vessel segment with ISA; external elastic membrane area was 19.4±6.6 versus 19.5±6.4 mm 2 at follow-up I and II, respectively. There was also no significant change in external elastic membrane area between vessel segment with ISA and without ISA (+1.5% versus −3.0%, respectively; P =0.27) at late follow-up. The ISA area, either including (2.5±1.7 versus 3.8±6.3 mm 2 ; P =NS) or excluding (2.5±1.8 versus 2.4±1.7 mm 2 ; P =NS) a single patient with aneurysm formation, was not significantly different between follow-up I and II. One patient manifested a coronary aneurysm in the stented segment at late follow-up that was probably present at the initial follow-up but masked by thrombus. It was successfully treated with a covered stent. All patients were asymptomatic, and no patient experienced late thrombotic occlusion.

Conclusions— Vessel dimensions and area of ISA did not change over time, except for 1 coronary aneurysm that became apparent. ISA after implantation of a SES was not associated with adverse events at late follow-up.

Usefulness of shear stress pattern in predicting neointima distribution in sirolimus-eluting stents in coronary arteries

The true 3-dimensional neointimal thickness distribution in sirolimus-eluting stents was investigated in relation to the shear stress distribution, which was obtained from computational fluid dynamics calculations. Small pits were observed between the stent struts in all patients, and a significant inverse relation between neointimal thickness and shear stress was found, indicating that deeper pits were present in the outside curve of the stented segments.

Cost-effectiveness of bypass surgery versus stenting in patients with multivessel coronary artery disease

PURPOSE

To compare the cost-effectiveness of surgical and angioplasty-based coronary artery revascularization techniques, in particular, angioplasty with primary stenting.

METHODS

We used data from the Study of Economics and Quality of Life, a substudy of the Bypass Angioplasty Revascularization Investigation (BARI), to measure the outcomes and costs of angioplasty and bypass surgery in patients with multivessel coronary artery disease who had not undergone prior coronary artery revascularization. Using a Markov decision model, we updated the outcomes and costs to reflect technology changes since the time of enrollment in BARI, and projected the lifetime costs and quality-adjusted life-years (QALYs) for the two procedures from the time of initial treatment through death. We accounted for the effects of improved procedural safety and efficiency, and prolonged therapeutic effects of both surgery and stenting. This study was conducted from a societal perspective.

RESULTS

Surgical revascularization was less costly and resulted in better outcomes than catheter-based intervention including stenting. It remained the preferred strategy after adjusting the stent outcomes to eliminate the costs and events associated with target lesion restenosis. Among angioplasty-based strategies, primary stent use cost an additional 189,000 US dollars per QALY gained compared with a strategy that reserved stent use for treatment of suboptimal balloon angioplasty results.

CONCLUSION

Bypass surgery results in better outcomes than angioplasty in patients with multivessel disease, and at a lower cost.

Impact of preinterventional arterial remodeling on neointimal hyperplasia after implantation of (non-polymer-encapsulated) paclitaxel-coated stents: a serial volumetric intravascular ultrasound analysis from the ASian Paclitaxel-Eluting Stent Clinical Trial (ASPECT)

BACKGROUND

This study used serial volumetric intravascular ultrasound (IVUS) to evaluate the effect of preinterventional arterial remodeling on in-stent intimal hyperplasia (IH) after implantation of non-polymer-encapsulated paclitaxel-coated stents.

METHODS AND RESULTS

Patients were randomized to placebo or one of two doses of paclitaxel (low dose, 1.28 microg/mm2; high dose, 3.10 microg/mm2). Complete preinterventional, post-stent implantation, and follow-up IVUS were available in 18 low-dose and 21 high-dose patients. IH volumes were similar in low-dose and high-dose patients: 17.6+/-15.1 mm3 in low-dose patients and 13.1+/-13.3 mm3 in high-dose patients (P=0.3). Therefore, IVUS findings in low- and high-dose patients were combined. Preinterventional remodeling was assessed by comparing lesion site to proximal and distal reference arterial area: positive remodeling (lesion>proximal reference, n=13), intermediate remodeling (distal reference<lesion<proximal reference, n=13), and negative remodeling (lesion<distal reference, n=13). During follow-up, there was a decrease in lumen volume in positive remodeling lesions (from 106+/-30 to 90+/-27 mm3; P=0.0067) and in intermediate remodeling lesions (from 97+/-28 to 76+/-31 mm3; P=0.0004), but not in negative remodeling lesions (99+/-27 versus 92+/-32 mm3; P=0.15). The follow-up IH volume was lower in negative remodeling lesions (5+/-7 mm3) compared with positive remodeling (20+/-14 mm3; P=0.0051) and intermediate remodeling lesions (20+/-15 mm3; P=0.0043); however, IH volume was virtually identical in positive and intermediate remodeling lesions. Multivariate linear regression analysis determined that remodeling and inflation pressure were independent predictors of IH volume; variables tested in the model included diabetes, acute coronary syndromes, dose, remodeling, and preinterventional plaque burden.

CONCLUSIONS

Preinterventional arterial remodeling, especially negative remodeling, influences neointimal hyperplasia suppression after implantation of non-polymer-encapsulated paclitaxel-coated stents.

Coronary stenting for a muscular bridge in a patient with hypertrophic obstructive cardiomyopathy

A young woman with hypertrophic cardiomyopathy presented with intractable chest pain due to a myocardial bridge over the left anterior descending artery, producing severe compression during systole. Percutaneous intracoronary stenting was performed. The patient, however, developed severe and diffuse restenosis within 30 days of the procedure. Myotomy may provide a more effective treatment option for such patients with symptomatic myocardial bridging.

The role of inflammation in vascular injury and repair

Inflammation plays a critical role in the vascular response to injury. In particular, mechanical injury using techniques such as balloon angioplasty and stenting results in complex inflammatory reactions which influence proliferation of vessel wall constituents such as endothelial cells, smooth muscle cells, and extracellular matrix proteins. Inflammatory cells are recruited to the injured vessel wall initially as a reparative mechanism; however, these same inflammatory processes are also pivotal in the development of restenotic lesions. Leukocytes serve as the primary inflammatory cells but we now know that platelets produce a number of important inflammatory mediators. This review describes the mechanisms that regulate endothelial cell migration, smooth muscle cell activation, and extracellular matrix protein production, all of which are key components in the inflammatory response to vascular injury.

Drug-eluting stents for cardiovascular disorders

Drug-eluting stents have emerged in recent years as a very promising therapy for prevention of restenosis after coronary implantation. Early randomized, clinical trials have suggested that stents eluting drugs, such as paclitaxel or sirolimus, released from polymeric and nonpolymeric coatings, are able to reduce restenosis in simple de novo lesions by more than 80% in comparison with bare metal stents. If restenosis can be indeed minimized globally by drug-eluting stents, coronary revascularization may expand to patients and lesions currently not considered for percutaneous intervention because of excessive recurrence, and may open possibilities for other stent-based endovascular treatments of atherosclerosis.

Impact of intravascular ultrasound-guided stenting on long-term clinical outcome: a meta-analysis of available studies comparing intravascular ultrasound-guided and angiographically guided stenting

To date, only a few studies have compared the clinical efficacy of intracoronary ultrasound (IVUS)-guided to angiographically guided stenting. Furthermore, it is not yet known whether the lower restenosis rate shown with the former strategy would translate into a substantial clinical advantage. Therefore, the aim of the present investigation was to improve the level of evidence of these studies by means of a formal meta-analysis. Nine studies were considered suitable for analysis. Odds ratios (ORs) were calculated for 6-month clinical follow-up. Primary endpoint was a composite of death and nonfatal myocardial infarction (MI), as considered in every single study. Secondary endpoints were major adverse cardiac events (MACEs), according to single study definition, the individual cardiac events, as well as several pre- and postprocedure and follow-up angiographic parameters. Overall, 2,972 patients were included. At 6 months, the OR for death and nonfatal MI was 1.13 (95% CI = 0.79-1.61; P = 0.5) for patients with IVUS-guided stenting. However, patients with IVUS-guided stenting had less target vessel revascularizations (OR = 0.62; 95% CI = 0.49-0.78; P = 0.00003) and MACEs (OR = 0.79; 95% CI = 0.64-0.98; P = 0.03) compared to angiographically guided stenting. In addition, subjects treated with IVUS-guided stenting had significantly less binary restenosis (OR = 0.75; 95% CI = 0.60-0.94; P = 0.01). The present meta-analysis demonstrates that IVUS-guided stenting implantation has a neutral effect on long-term death and nonfatal MI compared to an angiographic optimization. However, IVUS-guided stenting significantly lowers 6-month angiographic restenosis and target vessel revascularizations. Whether these benefits could be very helpful when dealing with lesions at high risk for restenosis is still an issue.

Regional remodeling as the cause of late stent malapposition

BACKGROUND

Late stent malapposition (LSM) is only detected if intravascular ultrasound (IVUS) is performed at implantation and follow-up. We used a novel "regional" IVUS analysis to assess the mechanism of LSM.

METHODS AND RESULTS

Corresponding image slices on postimplantation and follow-up IVUS studies of 11 malapposed stents were identified and electronically rotated until they were aligned. The geometric center of the stent was identified, and the angle of late malapposition measured. Radii were drawn from this center through the transition points between complete apposition and LSM. These two circumferences were divided into equal arcs, and radii were drawn to the external elastic membrane (EEM). Measurements included EEM radius and circumference, plaque and media (P&M=EEM minus stent radius) thickness and area, and stent-intima separation. Mean baseline EEM radius and P&M thickness were similar in apposed and malapposed circumferences. At follow-up, mean EEM radius increase within the malapposed circumference (0.57+/-0.34 mm) was larger than within the apposed circumference (0.16+/-0.18 mm; P=0.0004). DeltaEEM for each malapposed radius was greater than for each apposed radius (P<0.05 for all comparisons). Stent-intima separation correlated with EEM radius increase within the malapposed circumference (r=0.83, P=0.0013). At follow-up, the mean P&M thickness decreased in the malapposed circumference (-0.31+/-0.22 mm; P<0.0001). However, the decrease in P&M thickness in the malapposed circumference occurred because the same P&M area was distributed over a larger circumference (4.1+/-1.6 mm to 5.4+/-3.0 mm; P=0.05), the result of positive remodeling.

CONCLUSIONS

The main cause of LSM is a regional increase in EEM (regional positive remodeling).

[Drug-eluting stents in complex lesions]

Interventional cardiology has evolved tremendously over the past two years with the advent of drug-eluting stents. The RAVEL trial was the first randomized study conducted with sirolimus-eluting stents in a selected population of patients in whom a 0% rate of binary restenosis was achieved. The objective of the SIRIUS trial conducted in a more complex patient population was to test the efficacy of the sirolimus-eluting stent in high-risk settings such as coronary bifurcation lesions.

Evaluation of coronary remodeling after sirolimus-eluting stent implantation by serial three-dimensional intravascular ultrasound

This study evaluates the response of the coronary vessel wall to implantation of the sirolimus-eluting stent (SES), Bx-VELOCITY, by using serial intravascular ultrasound. SESs have a major impact on the inhibition of in-stent neointimal hyperplasia. However, changes in the vessel wall and behind stent struts in animal models and humans have not been evaluated after SES implantation. Thirty-four patients who received a SES (n = 24) or a Bx-VELOCITY bare stent (BS) (n = 10) for single de novo coronary lesions and had serial motorized pullback 3-dimensional intravascular ultrasound were included. Stent, lumen, and vessel volumes were similar in the 2 groups at baseline. At follow-up, significantly larger lumen and lower neointimal hyperplasia volumes (0.7 vs 33 mm(3), p = 0.001) were seen in the SES group compared with the BS group. There was no significant difference between SES and BS in either the vessel volume (+2.4% vs +0.7%, p = NS) or the plaque behind stent volume change (+3.4% vs +2.5%, p = NS) from after the procedure to late follow-up. The stent edges also showed no significant difference between postprocedural and follow-up measurements, either in patients receiving SESs or BSs. No stented or edge segment required redilatation in the SES group, whereas 2 patients underwent repeat percutaneous coronary angioplasty in the BS group. In the SES group, 1 patient (4%) showed late acquired incomplete stent apposition. Thus, the SES is effective in inhibiting neointimal hyperplasia without affecting vessel volume and plaque behind the stent.

Automated three-dimensional assessment of coronary artery anatomy with intravascular ultrasound scanning

BACKGROUND

Angiography allows the definition of advanced, severe stages of coronary artery disease, but early atherosclerotic lesions, which do not lead to luminal stenosis, are not identified reliably. In contrast, intravascular ultrasound scanning allows the precise characterization and quantification of a wide range of atherosclerotic lesions, independent of the severity of luminal stenosis.

METHODS

Three-dimensional (3-D) reconstruction of entire coronary segments is possible with the integration of sequential 2-dimensional tomographic images and allows volumetric analysis of coronary arteries.

RESULTS

Automated systems able to recognize lumen and vessel borders and to display 3-D images are becoming available.

CONCLUSION

These systems have the potential for on-line 3-D image reconstruction for clinical decision-making and fast routine volumetric analysis in research studies. This review describes 3-D intravascular ultrasound scanning acquisition, analysis, and processing, and the associated technical challenges.

Paclitaxel coating reduces in-stent intimal hyperplasia in human coronary arteries: a serial volumetric intravascular ultrasound analysis from the Asian Paclitaxel-Eluting Stent Clinical Trial (ASPECT)

BACKGROUND

The aim of this study was to use serial volumetric intravascular ultrasound (IVUS) to evaluate the effect of a paclitaxel coating on in-stent intimal hyperplasia (IH).

METHODS AND RESULTS

Patients were randomized to placebo (bare metal stents) or 1 of 2 doses of paclitaxel (low dose: 1.28 microg/mm2; high dose: 3.10 microg/mm2). Complete post-stent implantation and follow-up IVUS were available in 81 patients, including 25 control patients and in 28 receiving a low-dose and 28 receiving a high dose. Volumetric analysis of the stented segment and of both reference segments was performed. Baseline stent measurements and both reference measurements were similar among the groups. With increasing doses, there was a stepwise reduction in IH accumulation within the stented segment (31+/-22 mm3 in control, 18+/-15 mm3 in low dose, and 13+/-14 mm3 in high dose, P<0.001). Post hoc analysis showed less IH accumulation when low- and high-dose patients were compared with control (P=0.009 and P<0.001, respectively), but not when low-dose patients were compared with high-dose patients (P=0.2). Focal late malapposition was seen in 1 high-dose patient. With increasing doses, there was no significant change in the reference segments.

CONCLUSIONS

Paclitaxel-coated stents are effective in reducing in-stent neointimal tissue proliferation in humans. They are not associated with edge restenosis or significant late malapposition.

Drug eluting stents: are human and animal studies comparable?

Animal models of stenting probably predict human responses as the stages of healing are remarkably similar. What is characteristically different is the temporal response to healing, which is substantially prolonged in humans. The prevention of restenosis in recent clinical trials of drug eluting stents may represent a near absent or incomplete phase of intimal healing. Continued long term follow up of patients with drug eluting stents for major adverse cardiac events and angiographic restenosis is therefore imperative.

Background incidence of late malapposition after bare-metal stent implantation

BACKGROUND

Late stent malapposition has been reported to be an abnormal finding after vascular brachytherapy and, possibly, implantation of drug-eluting stents. It can only be detected if intravascular ultrasound (IVUS) is performed at follow-up. However, the "background" frequency of late stent malapposition after bare-metal stent implantation is not known.

METHODS AND RESULTS

We studied 206 patients with native artery lesions who had tubular-slotted bare-metal stent implantation and who had IVUS performed at index and after 6+/-3 months of follow-up. There were 9 patients (4.4%) with late malapposition, which is separation of at least 1 stent strut from the arterial wall intima that does not overlap a side-branch, with evidence of blood flow (speckling) behind the strut, and where the immediate postimplantation IVUS revealed complete apposition of the stent to the vessel wall. The location of late malapposition was the stent edge in 8 of 9 patients. The maximum area, length, volume, and arc of late malapposition measured 3.1+/-2.4 mm(2), 3.3+/-2.2 mm, 21+/-27 mm(3), and 110+/-61 degrees, respectively. There was an increase in external elastic membrane (EEM) area (20.7+/-4.9 to 26.9+/-4.2 mm, P=0.0021) and plaque area (10.1+/-3.7 to 14.8+/-3.6 mm, P=0.0022); however, the increase in EEM was greater than the increase in plaque. The area of late malapposition correlated directly with the increase in EEM area (r=0.75, P=0.0205).

CONCLUSION

Late malapposition occurs in 4% to 5% of slotted-tube bare-metal stents, usually at stent edges. The main cause is positive remodeling out of proportion to the increase in peri-stent intimal hyperplasia.

Drug-eluting stents: from bench to bed

The introduction of stents to clinical practice in 1987 was the major breakthrough in the field of percutaneous coronary intervention (PCI). The use of stenting has drastically improved the outcomes of traditional PCI. First stents were approved for bailout and treatment of dissections, reducing dramatically the need for emergent coronary artery bypass grafting (CABG) as a result of vessel closure during PCI. Later stents were proven to reduce the restenosis rate of PCI from 30%-40% with balloon angioplasty to 15%-20% with stents, primarily by eliminating elastic recoil and vascular remodeling as shown by intravascular ultrasound (IVUS) studies. These outcomes have led to a wide acceptance of stenting as the strategy of choice for more than 80% of all PCI procedures performed. The current review focuses on the following topics: (1) strategies in drug selection to reduce neointimal proliferation, (2) stent designs and polymer selection as a platform for drug-eluting stents, (3) review of major preclinical and clinical experimental work performed in the field, and (4) a discussion of the potential and limitations of the technology.

Influence of Class I interferons on performance of vascular cells on stent material in vitro

PURPOSE

Numerous reports suggest that Class 1 interferons (IFNs), particularly IFN-gamma, inhibit migration and proliferation of different types of human cells. The objective of the present study was to determine the effect of Class I IFNs on viability and growth characteristics of human aortic endothelial cells (ECs), smooth muscle cells (SMC) and fibroblasts (FBs) in vitro.

METHODS

Stainless-steel (316-l) disks were coated with fibrin meshwork containing IFN-gamma or IFN-alpha. The discs and IFN embedded meshwork were incubated with human EC, SMC and FB, and then cultured, whereas control cells were seeded onto uncoated surfaces or plain fibrin meshwork. Concentrations of recombinant IFN varied from 5 to 20 ng/cm(2). Assessment of effect on cell viability, growth and attachment was performed utilizing Alamar Blue (AB) assay. Cell morphology was assessed by scanning electron microscopy (SEM).

RESULTS

We have now shown inhibitory capacity of IFN-gamma on all three types of unstimulated cells. The growth-inhibitory effect was maximal with SMC, while it was minimal with FB and EC. IFN-gamma abrogated mitogenic responses of SMC but not EC and partially FB to VEGF and FGF stimulation. IFN-alpha was able to inhibit EC growth and, to a lesser extent, FB, and did influence growth rates of SMC. Biochemical analysis of lactate dehydrogenase activity suggested that IFN was not toxic to vascular cells. We also measured the expression of cell adhesive molecules: P- and E-selections, PECAM and ICAM-1. These molecules were upregulated by IFN in EC. Media derived from quiescent human SMC displayed low immunoreactive elastase activity, while conditional media after IFN-gamma treatment but not IFN-alpha treatment had approximately a threefold greater activity.

CONCLUSION

These data suggest that IFN-gamma significantly inhibits SMC growth in the absence of significant endothelial toxicity and is dose-dependent; however, animal experiments are needed to further explore the antirestenotic effects of IFNs.