Three-year follow-up after implantation of metallic coronary-artery stents

Impact of In-Stent Minimal Lumen Area at 9 Months Poststent Implantation on 3-Year Target Lesion Revascularization–Free Survival

Background— Intravascular ultrasound (IVUS) is used to assess intermediate lesions in native coronary arteries; minimum lumen area (MLA) <4.0 mm 2 is accepted as a cutoff for a significant stenosis. We evaluated the IVUS in-stent MLA at 9-month follow-up that best predicted subsequent target lesion revascularization (TLR)–free survival in patients from the TAXUS IV, V, and VI studies.

Methods and Results— In the combined TAXUS IV, V, and VI randomized trials, 9-month IVUS was available in 635 patients (331 treated with paclitaxel-eluting stents [PES] and 304 treated with bare-metal stents [BMS]) who did not require TLR in the first 9 months postintervention and who were followed for 3 years. The in-stent MLA that best predicted 3-year TLR-free survival was determined. At 9-months follow-up, IVUS-measured in-stent MLA was 5.7�2.3 mm 2 in the PES group and 4.8�2.3 mm 2 in the BMS group. Between 9 months and 3 years, TLR was required in 4.9% of patients who were treated with PES and 6.7% of patients who were treated with BMS. Multivariate analysis identified MLA at 9 months as a significant predictor of late TLR (hazard ratio, 0.63 [0.43–0.93]; P =0.02). The ability of MLA to predict late TLR was further assessed using receiver operating characteristic analysis. MLA was found to be an acceptable discriminator for both PES (c=0.7448) and BMS (c=0.7329). Finally, the optimal thresholds of MLA that best predicted subsequent TLR-free survival were determined to be 4.2 mm 2 for PES and 4.0 mm 2 for BMS.

Conclusion— In the combined IVUS analysis of TAXUS IV, V, and VI, patients who did not require TLR within the first 9 months had a high subsequent TLR-free survival rate whether treated with PES or BMS. MLA measured by IVUS at 9 months predicted subsequent TLR with a cutoff similar to intermediate, de novo lesions in native coronary arteries.

Drug release kinetics from stent device-based delivery systems

In an effort to overcome the limitations of balloon-expandible intravascular metal stent-induced neointimal formation, drug-coated stent devices have been developed. The stent platform allows the local delivery of drugs to an injury site, thereby reducing the amount of drug exposure to the systemic circulation and other organs. The drug carrier matrix allows the release of the drug in a diffusion-controlled manner over an extended time period after the stent implant. The drugs are chosen such that the complex cascade of events that occurs after stent implantation that leads to smooth muscle cell proliferation and migration towards the intima are inhibited. The success of an antirestenotic drug therapy from a drug-coated stent is dependent, at least partially, on the extent of drug elution from the stent, the duration and rate of release, and accumulation of drug in the arterial wall in such a way that it covers the initiation and progression of vessel wall remodeling. The local vascular drug concentrations achieved are directly correlated with the biological effects and local vascular toxicity, and there is therefore a challenge in finding an optimum dose of drug to be delivered to tissues (ie, one that has the desired therapeutic effect without local adverse effects). There is increased focus on optimization of various factors that affect drug release from the stent system, including the physicochemical properties of the drugs, carrier vehicle formulation, and profile of elution kinetics. This review highlights the various factors involved in drug release kinetics, local vascular toxicity, carrier vehicle matrix, tissue deposition, and distribution through the arterial wall from stent-based drug delivery systems.

Approaches for prevention of restenosis

Coronary artery disease is characterized by a narrowing (stenosis) of the arteries that supply blood to the tissue of the heart. Continued restriction of blood flow manifests itself as angina and ultimately myocardial infarction (heart attack) for the patient. Heart bypass was once the only treatment for this condition, but over the years percutaneous coronary intervention (PCI) has become an increasingly attractive alternative to medical therapy and surgical revascularization for the treatment of coronary artery disease. A vascular stent is a medical device designed to serve as a temporary or permanent internal scaffold, to maintain or increase the lumen of a blood vessel. Metallic coronary stents were first introduced to prevent arterial dissections and to eliminate vessel recoil and intimal hyperplasia associated with PCI. Further advancement in the treatment of coronary artery disease is the development of drug-eluting stents that dramatically reduce the incidence of in-stent restenosis to less than 5%. Local drug delivery offers the advantages of allowing a relatively high local concentration of drug at the treatment site while minimizing systemic toxic effect. This review describes approaches for prevention of restenosis. It focuses on drugs for prevention of restenosis, bare metal stents, and drug-eluting stents. It also describes recent advances in bioresorbable stents. One of the chapters is dedicated to our novel composite bioresorbable drug-eluting fibers, designed to be used as basic elements in drug-eluting stents.

Percutaneous coronary intervention versus coronary artery bypass graft surgery for the treatment of unprotected left main coronary artery stenosis: in-hospital and one year outcome after emergent and elective treatments

This study attempts to compare the risks and benefits of provisional stenting with drug eluting stents and bypass surgery for left main coronary artery (LMCA) stenosis. Recent improvements in interventional technologies have increased interest in percutaneous treatment of LMCA stenosis. However, application of percutaneous techniques to LMCA has been sporadic and controversial. In-hospital and one year outcomes of coronary artery bypass graft (CABG) and percutaneous coronary intervention (PCI) cases were compared. From September, 2003 to June, 2005, a total of 59 consecutive patients with de novo unprotected LMCA stenosis were treated with either CABG or PCI. Twenty patients received non-intravascular ultrasound-guided PCI with a stent in the LMCA. Thirty-nine patients underwent CABG. At 30-day follow-up, the major adverse cardiac and cerebrovascular event (MACE) rates of mortality, myocardial infarction, cerebral vascular accident, and target vessel revascularization were 25.6% in the CABG group and 5% in the PCI group (P=0.054). At one year follow-up, the MACE rates were 33.3% in the CABG group and 5% in the PCI group. One year MACE for the CABG group significantly differed from that of the PCI group (P=0.015). The odds ratio (OR) of one year MACE-free survival was 0.75 (P<0.001) in the CABG group versus the PCI group. Further analysis demonstrated there was a significant difference in in-hospital MACE and one year MACE between the elective CABG group and elective PCI group (P=0.045). However, there was no significant difference between the emergent CABG group and emergent PCI group (P=1.000 for in-hospital MACE; P=0.486 for one year MACE). PCI on unprotected LM offers an alternative option in patients with high surgical risk and appropriate lesion morphology.

Comparison of coronary artery stenting outcomes in the eras before and after the introduction of drug-eluting stents

BACKGROUND

Few studies have compared medium-term outcomes for drug-eluting stents (DES) and bare metal stents, and most are relatively small randomized controlled trials. Furthermore, since the introduction of DES, there has been increased use and duration of use of clopidogrel, statins, and other evidence-based therapies. The purpose of the present study was to compare outcomes for patients who underwent stenting in the eras before and after the introduction of DES.

METHODS AND RESULTS

New York state patients undergoing stenting in all nonfederal hospitals in the state were studied. Patients were excluded if they had a previous revascularization. Risk factors that were significant predictors of adverse outcomes were used to adjust adverse outcome rates. The study included 11,436 patients who received stents between October 1, 2002, and March 31, 2003, and 12,926 patients who underwent stenting between October 1, 2003, and March 31, 2004. Death rates, the combined end point of death and myocardial infarction (MI), nonfatal MI requiring readmission, target vessel revascularization, and target lesion revascularization were compared at 2 years. Patients in the DES era had significantly better risk-adjusted outcomes for death/MI (adjusted hazard ratio, 0.90; 95% confidence interval, 0.83 to 0.97), 9.9% versus 10.8%; nonfatal MI requiring readmission (adjusted hazard ratio, 0.86; 95% confidence interval, 0.76 to 0.97); target vessel revascularization (adjusted hazard ratio, 0.60; 95% confidence interval, 0.56 to 0.64), 11.2% versus 17.9%; and target lesion revascularization (hazard ratio, 0.55; 95% confidence interval, 0.51 to 0.59), 8.4% versus 14.7%.

CONCLUSIONS

Patients in the DES era experienced lower rates of death/MI, nonfatal MI, target vessel revascularization, and target lesion revascularization, but there were no differences in the rates of death. These improvements are likely a result of increased use of clopidogrel, statins, and dual antiplatelet therapy, in addition to the introduction of DES.

Effect of cilostazol on in-stent neointimal hyperplasia after coronary artery stenting: a quantative coronary angiography and volumetric intravascular ultrasound study

BACKGROUND

This study was designed to investigate the efficacy of cilostazol on the prevention of in-stent neointimal hyperplasia as measured by both quantitative coronary angiography (CAG) and volumetric intravascular ultrasound (IVUS).

METHODS AND RESULTS

Fifty-nine patients (39 men, age 62 years) undergoing elective coronary stenting were randomly assigned to receive aspirin plus clopidogrel or ticlopidine (Group I, n=28, 30 lesions) or aspirin plus clopidogrel or ticlopidine plus cilostazol (Group II, n=31, 35 lesions). CAG and IVUS were performed and repeated at 6 months to assess the primary endpoints of minimal luminal diameter (MLD) and in-stent neointimal hyperplasia volume. Follow-up CAG was performed on all patients and follow-up IVUS study was available for 50 lesions in 48 patients (24 lesions in Group I, 26 in Group II). There were no significant differences in the baseline angiographic data between the 2 groups. At 6 months follow-up, in-stent MLD was 1.90+/-0.76 mm in Group I and 2.41+/-0.85 mm in Group II (p=0.006). Volumetric IVUS at 6 months demonstrated that in-stent intimal hyperplasia volume per stent length was 2.2+/-1.4 mm3/mm in Group I and 1.0+/-0.5 mm3/mm in Group II (p=0.001).

CONCLUSIONS

Triple antiplatelet therapy including cilostazol seems to be more effective at preventing in-stent neointimal hyperplasia than a dual antiplatelet regimen.

Drug-eluting stent safety

Drug-eluting stents (DESs) held the promise of mitigating, if not abolishing, in-stent restenosis. This led to early adoption and high penetration of DES use in percutaneous coronary intervention (PCI). Outcomes have not demonstrated an improvement in the hard end points of death and myocardial infarction with these devices, but repeat procedures for in-stent restenosis have decreased. The problem of stent thrombosis, a major obstacle that arose early in coronary stent development, has raised new contemporary concerns about the safety of DESs. The risk for stent thrombosis after bare metal stent placement appears to diminish with time, while very late stent thrombosis (>1 year after index PCI) occurs in small but measurable numbers after DES placement at a rate that continues to increase. Late-acquired incomplete stent apposition and abnormal endothelial function have also been reported. Restenosis, although significantly lessened, does occur after DES PCI. This report reviews DES safety issues that have been described.

The significance of preclinical evaluation of sirolimus-, paclitaxel-, and zotarolimus-eluting stents

Comparative preclinical histologic studies remain the most effective method for assessing the healing characteristics of vascular stents. The 2 most commonly used animal models to assess vascular responses to stent implantation are the porcine coronary artery and the rabbit iliac artery. Neither model alone is comparable to the human response to the implantation of a drug-eluting stent (DES). In the rabbit model at 28 days, the pathologies of the zotarolimus-eluting stent (ZES), the paclitaxel-eluting stent (PES), the sirolimus-eluting stent (SES), and a bare metal stent (BMS) were assessed. There was less inflammation with the ZES than with the SES or PES, and there were uncovered struts with the SES and PES but not with the ZES and BMS. In the pig model at 30, 90, and 180 days, the pathologies of the ZES, SES, and BMS were assessed. At 30 days, the thickness of neointima and the grade of inflammation were less with the SES than with the ZES and BMS, but at 90 and 180 days, the measures increased for the SES and were greater than those with the ZES and BMS, whereas the measures for the ZES and BMS did not change over time. In the rabbit model, the endothelialization of overlapping the SES, PES, and ZES was assessed. There was significantly greater endothelialization in the area above stent struts in the overlapping segment for the ZES than for the SES (p = 0.028). The level of endothelialization for the PES was less than that for the ZES, but the difference was not significant. Because arterial healing is multifactorial, it is extremely important that the next generation of DESs undergo preclinical testing in pig and rabbit models to examine endothelialization, inflammation, release kinetics, and neointimal reduction to establish the safety of these devices in humans.

Differences in utilization of drug-eluting stents by race and payer

Numerous disparities in access to health care by race and gender have been identified in the literature. This study examines differences in the use of drug-eluting stents (DES) versus bare-metal stents (BMS) by race, payer, and income level. Data from New York State's Percutaneous Coronary Intervention Reporting System from July 2003 to December 2004 were used to examine use of DES (20,165 patients) relative to BMS (4,547 patients) by race, payer, and annual income level, controlling for a variety of patient and hospital characteristics. African-Americans were found to be less likely to receive DES than other races between July 2003 and March 2004 (adjusted odds ratio [OR] 0.56, 95% confidence interval [CI] 0.50 to 0.65) and between April 2004 and December 2004 (adjusted OR 0.74, 95% CI 0.61 to 0.90). These disparities were reduced (respective adjusted ORs 0.67, 95% CI 0.58 to 0.77 and 0.81, 95% CI 0.66 to 0.91) when controlling for admitting hospital and hospital volume, but were still significant. Medicaid/self-pay patients, and patients living in zip codes with median annual incomes between $20,000 and $30,000 were also less likely to receive DES in the first time period (adjusted respective ORs 0.80, 95% CI 0.68 to 0.93) and 0.85, 95% CI 0.75 to 0.96). In conclusion, African-Americans and low income groups receive DES less frequently than their counterparts compared with BMS. This is related to the hospitals where they are admitted, but not entirely.

Applying drug-eluting stents in clinical practice

The use of percutaneous coronary interventions has resulted in significant improvement in patient care; however, the risk for restenosis remains a major limitation. Drug-eluting stents represent an impressive breakthrough in the evolution of interventional cardiology, but it is important to understand the limits to their added benefit. Safety of the procedure must continue to be the first consideration, and technique must not be compromised to accommodate new technology.

A comparison of mortality, myocardial infarction, and repeated revascularization for sirolimus-eluting and paclitaxel-eluting coronary stents

BACKGROUND

Drug-eluting stents are now used in most percutaneous coronary interventions. There are only 2 approved devices: sirolimus-eluting stents (SES) and paclitaxel-eluting stents (PES). Only a few population-based studies have compared their patient outcomes.

METHODS

All New York State patients undergoing SES or PES in nonfederal hospitals in the state between April 1 and December 31, 2004, except those with a previous revascularization, left main coronary artery disease, or a recent myocardial infarction (MI) or shock (4867 patients with PES and 6914 with SES) were followed up through the end of 2005. We compared SES and PES with respect to inhospital and 18-month mortality, 18-month mortality/MI, and subsequent target vessel and target lesion revascularization (TVR and TLR) after adjusting for differences in patient risk factors.

RESULTS

By 18 months after receiving a PES, 4.0% of the patients died compared with 4.1% for SES patients, 5.9% of PES patients experienced mortality/MI compared with 6.3% of SES patients, 6.8% of the PES patients had a subsequent TVR within 18 months compared with 7.8% for SES patients, and 4.5% of the PES patients had a subsequent TLR within 18 months compared with 5.3% for SES patients. The respective adjusted hazards ratios (PES/SES) for these adverse outcomes were 1.02 (95% CI 0.82-1.26, P = .86), 0.94 (95% CI 0.78-1.13, P = .52), 0.89 (95% CI 0.75-1.06, P = .20), and 0.86 (95% CI 0.70-1.05, P = .14).

CONCLUSIONS

Patients receiving PES and SES do not have significantly different 18-month mortality, mortality/MI, subsequent TVR, or subsequent TLR rates.

Serial Angioscopic Evidence of Incomplete Neointimal Coverage After Sirolimus-Eluting Stent Implantation

Background— The time course of neointimal formation after stent implantation has not been studied extensively by angioscopy in the drug-eluting stent era.

Methods and Results— Serial angioscopic findings at first follow-up (3.6±1.1 months), second follow-up (10.5±1.6 months), and third follow-up (21.2±2.2 months) after stent implantation were compared between sirolimus-eluting stents (SES, n=17) and bare-metal stents (BMS, n=11). Neointimal coverage, thrombus, and presence of yellow plaques underneath the stents were assessed. Neointimal coverage was graded as follows: grade 0, stent struts were fully visible; grade 1, struts bulged into the lumen, although they were covered; grade 2, struts were embedded by the neointima but were seen translucently; or grade 3, struts were fully embedded and invisible. Neointimal coverage was remarkably different between SES and BMS at each follow-up point. Neointimal coverage grade was 1.1±0.5 in SES versus 2.9±0.3 in BMS at the first follow-up ( P <0.0001), 1.1±0.5 in SES versus 3.0±0.0 in BMS ( P <0.0001) at the second follow-up, and 1.3±0.5 in SES versus 3.0±0.0 in BMS at the third follow-up ( P =0.0009). No significant serial changes in coverage grade were noted in the BMS group, whereas coverage grade slightly but significantly increased at the third follow-up in the SES group ( P <0.05). Thrombi were detected in 4 SES: a red thrombus was seen from the first to the third follow-up in 2; another was detected only at the third follow-up; and the fourth was seen at the first follow-up but disappeared at the second follow-up, associated with a new white thrombus despite dual antiplatelet therapy. Yellow plaques had disappeared by the time of the second follow-up in BMS. In contrast, yellow plaques were exposed in 71% of SES at the first follow-up and remained exposed until the third follow-up. Neointimal coverage grades correlated with thrombi ( P =0.002) and with yellow plaques ( P <0.0001).

Conclusions— Serial angioscopic findings up to 2 years after SES implantation were markedly different from those after BMS. Neointimal coverage was completed by 3 to 6 months in BMS. In contrast, SES demonstrated the presence of thrombi and yellow plaques even as much as 2 years after implantation.

Clinical in-stent restenosis with bare metal stents: is it truly a benign phenomenon?

OBJECTIVE

In-stent restenosis (ISR) remains an important problem following percutaneous coronary intervention (PCI). Although it is generally believed that patients with ISR present with stable angina, this has not been well characterized. The aim of this study was to define the incidence, predictors, timing and clinical presentation of patients with ISR requiring repeat catheterization.

DESIGN

Using a multiregion prospective database which captures all patients undergoing cardiac catheterization and revascularization in the Province of Alberta, Canada, consecutive bare metal stent (BMS) implantations from January 1, 1998 to December 31, 2002 were analyzed. All patients with a repeat angiogram within one year of the index PCI were reviewed for evidence of clinical-ISR (CISR), defined as ISR as the cause for clinical presentation at angiography.

RESULTS

Of the 12,492 consecutive PCI patients reviewed, 2521 had repeat angiography and 744 patients (6.0%) had CISR by study definition. The mean time to repeat angiography in CISR patients was 5.4+/-2.7 months and multivariate analysis identified female gender, diabetes mellitus, and prior PCI as predictors. The majority of patients presented with an acute coronary syndrome: 52.2% unstable angina/non-ST elevation myocardial infarction and 18.5% ST elevation myocardial infarction. Only 25.3% presented with stable exertional angina.

CONCLUSION

Although the incidence of CISR within one year after BMS was relatively low, the recurrent clinical event in the majority of cases was a high-risk coronary syndrome. Thus, careful consideration of the risks of ISR to a specific patient against the cost implications of novel and expensive means to decrease its occurrence is required.

Rapidly Self-Expandable Polymeric Stents with a Shape-Memory Property

A novel biodegradable stent, made of chitosan films cross-linked with an epoxy compound, with a shape-memory property was developed. To reduce their crystallinity, glycerol and poly(ethylene oxide) were blended in the chitosan films. The mechanical properties of the prepared stent were studied using a commercially available metallic stent as a control. After blending, the ductility of the chitosan films was improved, and the compressive strength of the stent was significantly enhanced. The metallic stent could tolerate elastic deformations of 10% before becoming irreversibly deformed, while the polymeric stent was able to withstand deformations up to 30% and still regain its original configuration. The developed stent could rapidly expand ( approximately 150 s) from its crimped (temporary) to fully expanded (permanent) states stimulated by hydration, which is advantageous considering avoiding its migration during in vivo deployment. In the preliminary animal study, the implanted stent was found to be intact, and no thrombus formation was seen in the stent-implanted vessel. This degradable stent can be an attractive alternative to metallic stents and may serve as a useful vehicle for local drug delivery.

Neointimal progression and luminal narrowing in sirolimus-eluting stent treatment for bare metal in-stent restenosis: a quantitative intravascular ultrasound analysis

BACKGROUND

Recurrent restenosis may occur after drug-eluting stent implantation for in-stent restenosis (ISR) of bare metal stents (BMSs), especially in areas involving drug-eluting stent gaps.

METHODS

To investigate the details of neointimal progression and luminal narrowing after the treatment of ISR using sirolimus-eluting stents (SESs), serial intravascular ultrasound analysis was performed in 65 patients with ISR at postintervention and at 6-month follow-up. The total stented segment was categorized into 3 compartments: new SES (N), new SES and old BMS overlap (N/O), and old BMS (O). In each of the 190 compartments, serial intravascular ultrasound parameters were analyzed at the cross section of the maximum change in neointimal area (delta neointimal area) from postintervention to follow-up or the minimum lumen area at follow-up if delta neointimal area was 0. Minimum lumen area in each compartment was also investigated serially.

RESULTS

At postintervention, lumen area was the smallest in compartment N/O (N 5.8 +/- 1.5, N/O 5.1 +/- 1.3, O 6.0 +/- 1.4 mm2, P = .005). Not only the average of maximum delta neointimal area (N 0.2 +/- 0.4, N/O 0.2 +/- 0.4, O 0.8 +/- 1.0 mm2, P < .0001) but also the frequency of minimum lumen area decreasing from > or = 4.0 mm2 at postintervention to < 4.0 mm2 at follow-up (N 4.0%, N/O 5.1%, O 23.5%, P = .012) was the largest in compartment O.

CONCLUSIONS

Neointimal progression and consequent luminal narrowing tend to occur where BMS is uncovered with SES in treatment of ISR, even in the absence of an obvious stenosis at postintervention.

Late restenosis following sirolimus-eluting stent implantation

Despite encouraging results from randomized trials, concerns exist about long-term results of sirolimus-eluting stent implantation. We sought to determine whether in-stent restenosis occurring >1 year ("late") after sirolimus-eluting stent implantation is a real clinical entity. We analyzed data on all sirolimus-eluting stents implanted in our institution before March 2003. During the study period 928 lesions in 433 patients were treated. Angiographic follow-up was performed in 306 patients (70.6%) with 679 lesions (73.2%). Angiography after 1 year was performed only in symptomatic patients. We considered restenosis "early" if it occurred during the first year and late if after 1 year. Late restenosis required demonstration of a widely patent stent at 6 to 9 months, with repeat angiography after 1 year demonstrating restenosis. Restenosis occurred in 160 lesions overall (23.5%). Of the 31 (4.6%) that were documented after 1 year, 13 were excluded from analysis due to absence of 6- to 9-month angiography; the remaining 18 (2.6%, 1.7 to 4.2) fulfilled our criteria for late restenosis (median time of documentation 607 days, interquartile range 511 to 923). In conclusion, late restenosis is an infrequent but real entity; its existence implies we should not discount the possibility of restenosis as the cause of symptoms that develop >1 year after sirolimus-eluting stent implantation.

Release profiles in drug-eluting stents: issues and uncertainties

This review presents the current data on drug release from drug-eluting stents and the effects of the release profiles on animal and human data for coronary stenosis. Data for the two most important drugs, sirolimus (rapamycin) and paclitaxel, are presented, the polymers used are described and the observed release profiles are discussed for various polymer carriers. The current literature on the tissue compatibility of the polymers commonly used in drug-eluting stents is also discussed. The range of release rates from stents studied to date is limited for sirolimus, but somewhat broader for paclitaxel. Animal and human data comparing the different release profiles are limited to about 6 months for animals and 2-4 years for humans. From the data available, it appears that for both sirolimus and paclitaxel, a slow-releasing drug-eluting stent leads to slightly more favorable angiographic outcomes than more rapid release. Most of the complications arising from the use of drug-eluting stents are attributed to incomplete healing; one possible clinical consequence of this delay in healing is that anti-platelet therapy needs to be maintained over a much longer period than is the case for bare metal stents.

Primary stent therapy for symptomatic intracranial atherosclerotic stenosis: 1-year follow-up angiographic and midterm clinical outcomes

OBJECT

The aim of this study was to report 1-year angiographic follow-up results and midterm clinical outcomes in patients with symptomatic intracranial atherosclerotic lesions treated with stent placement.

METHODS

Ten patients with ischemic symptoms referable to stenotic intracranial atherosclerotic arteries, with greater than 60% stenosis, underwent elective surgery in which a primary stent was placed. All patients underwent pretreatment (> or =1 week) combination oral antiplatelet (clopidogrel and aspirin) therapy and long-term (6-month) combination oral antiplatelet (clopidogrel and aspirin) therapy after stents were placed. The procedure involved selecting stents of the same size as the diameter of the target vessel and slowly inflating the balloon to its nominal pressure. One-year angiography and midterm clinical follow-up data were obtained. The stents were successfully placed in all patients without any perioperative complication. The mean preoperative stenosis rate of 81% decreased to 4% after the stent was placed. Nine patients who underwent follow-up angiography (one patient refused) at a mean of 12.3 months (range 10-19 months) had no changes in luminal diameter compared with the immediate postoperative luminal diameter. Luminal narrowing increased, from 15 to 38%, in one case in which there was comparatively greater residual stenosis (15%). No patient suffered new ischemic symptoms during a mean clinical follow-up period of 21 months (range 12-36 months).

CONCLUSIONS

Elective stent surgery can provide good angiographic and clinical midterm outcomes in patients with symptomatic intracranial atherosclerotic stenosis, and the procedure is associated with a high degree of technical success. Reassessment of these promising results is needed in a larger population and in a randomized prospective comparison study.

Five-year outcomes after stenting of unprotected left main coronary artery stenosis in patients with normal left ventricular function

BACKGROUND

We analyzed the long-term (5-year) outcome of patients treated with stenting for unprotected left main coronary artery (LMCA) stenosis.

METHODS

Between January 1995 and September 2001, 187 consecutive patients with unprotected LMCA stenosis and normal left ventricular function underwent elective stenting. Patients were examined or interviewed after 1, 3 and 6 months, and every 4 months thereafter for the occurrence of major adverse cardiac events (MACE), including death, myocardial infarction (MI) and target lesion revascularization (TLR).

RESULTS

The procedural success rate was 99.5%. During hospitalization, there were no deaths and only one stent thrombosis. Six-month angiography in 162 patients (follow-up rate, 86.6%) showed a restenosis rate of 33.3%. During 5-year follow-up, there were 13 deaths (6 cardiac, 7 noncardiac) and 2 nonfatal MI. TLRs were required in 36 (20.9%) patients and new lesion revascularizations were required in 13 (5.0%) patients. At 1, 3 and 5 years, the cumulative probabilities for freedom from MACE were 79.9+/-1.8%, 77.5+/-2.5% and 77.5+/-2.5%, respectively.

CONCLUSION

The initial favorable outcomes of patients with normal left ventricular function after stenting of unprotected LMCA stenosis were sustained for up to 5 years.

Long-Term Outcome of First-Generation Metallic Coronary Stent Implantation in Patients With Coronary Artery Disease Observational Study Over a Decade

BACKGROUND

In the era of drug-eluting stents, percutaneous coronary intervention (PCI) has been considered an established therapeutic modality for patients with coronary artery disease (CAD). However, little is known about the long-term prognosis.

METHODS AND RESULTS

Using data obtained from a single-center registry for cases of first-generation bare metallic stent (BMS) implantation, a 10-year follow-up study in patients with CAD was performed. Data for 125 serial patients (aged 62+/-9 years, 104 males) in whom a BMS was successfully implanted was analyzed. Cardiac death (n=16 [12.8%]), including sudden cardiac death (n=9 [7.2%]), non-cardiac death (n=17 [13.6%]) and non-fatal acute myocardial infarction (n=16 [12.8%]) were documented. At 10 years, cumulative probabilities of target and non-target lesion revascularization were 20.5% and 41.5%, respectively, and only 39.2% of the patients were free from cardiac events (cardiac death/myocardial infarction/unplanned revascularization). Age and left ventricular ejection fraction (LVEF) were significant predictors of total death, and LVEF and the use of diuretics were predictors of cardiac events.

CONCLUSIONS

Stabilization of the initial stented site was relatively good and the majority of cardiac events might have originated in non-target lesions. Prevention of systemic arteriosclerosis progression is important for patients with CAD, even after successful PCI.

Comparison of the incidence of acute coronary event after balloon angioplasty vs. stenting in native coronary arteries

OBJECTIVES

We sought to determine the incidence of acute coronary events after coronary stenting in comparison to that after plain old balloon angioplasty (POBA).

BACKGROUND

Although coronary stenting is proven to be effective in reducing the incidence of restenosis, the long-term outcome in terms of acute coronary events has not been clarified.

METHODS

Study subjects were 1,507 patients with 2,780 native coronary artery lesions treated by POBA (n=1,400) or stenting (n=1,380). Lesion stabilization, which was defined as freedom from restenosis confirmed by follow-up angiography 3 months after POBA and 6 months after stenting, was achieved in all subjects. All patients were clinically monitored for symptoms for at least 1 year after angioplasty, and the incidence of angiographically confirmed acute coronary event was compared between groups.

RESULTS

The clinical follow-up period was significantly longer in the POBA group than in the stent group (8.4 +/- 5.0 years vs. 5.9 +/- 3.0 years, p<0.0001). Acute coronary events occurred in association with 32 lesions (1.2% overall); the incidence was 1.1% (15 of 1,400) after POBA and 1.2% (17 of 1,380) after stenting. Freedom from acute coronary events related to the treated lesions was similar between the two groups. (p=0.0518 by log-rank test).

CONCLUSION

In terms of acute coronary events, the long-term clinical outcome of stenting is equivalent to that of POBA.

Novel composite fiber structures to provide drug/protein delivery for medical implants and tissue regeneration

A novel class of bioresorbable composite (core/shell) fiber structures loaded with bioactive agents was developed and studied. These unique polymeric structures are designed to combine good mechanical properties with a desired controlled release profile, in order to serve as scaffolds for tissue regeneration applications and as basic elements of medical implants. These core/shell fiber structures were formed by "coating" core polymer fibers with drug/protein-containing poly(dl-lactic-co-glycolic acid) porous structures. The shell preparation ("coating") was performed by the freeze-drying of water-in-oil emulsions. Both water soluble and water insoluble agents can be incorporated in these structures and their activity is preserved, since the fiber fabrication requires neither high temperatures nor harsh solvents in the vicinity of the bioactive agents. Examples for release profiles of protein (horseradish peroxidase) and drug (paclitaxel) are presented. We have demonstrated that appropriate selection of the emulsion's parameters can yield a variety of new core/shell fiber structures with desirable drug/protein release behavior. This will lead to the engineering of new implants and scaffolds, and will advance the field of tissue regeneration and medical implants.

Comparison of direct stenting versus conventional stent implantation on blood flow in patients with ST-segment elevation myocardial infarction

As compared with balloon angioplasty, stent implantation in treatment of acute myocardial infarction (AMI) reduces abrupt vessel closure, restenosis, and reocclusion rate. However, a few studies have demonstrated the safety and feasibility of direct stenting compared to conventional stent implantation technique. This study was designed to compare possible advantages of direct stenting with conventional stent implantation on immediate coronary blood flow and short-term clinical benefits in patients with AMI. Fifty patients with AMI who underwent mechanical revascularization were eligible for the study. The patients were randomly assigned to undergo either direct stenting (n = 25) or conventional stent implantation (n = 25). Before and after the procedure thrombolysis in myocardial infarction (TIMI) flow and postprocedural corrected TIMI frame count (cTFC) of the infarct-related artery were measured. There was no difference in TIMI flow distribution at baseline between the 2 groups. TIMI 3 flow rate significantly increased after procedure in both groups compared to baseline (p < 0.05). Postprocedural cTFC was found significantly lower in the direct stent arm compared to conventional stenting (p < 0.001). Both during and after the procedure the complication rate and procedural time were lower in the direct stenting arm. Direct stenting provides better immediate coronary blood flow and is a safe and feasible method compared with conventional stenting in patients with AMI. Improvement in coronary blood flow measured by the corrected TIMI frame count method may suggests a significant reduction of microvascular injury.

DRUG-ELUTING BIORESORBABLE STENTS FOR VARIOUS APPLICATIONS

A stent is a medical device designed to serve as a temporary or permanent internal scaffold to maintain or increase the lumen of a body conduit. Metallic coronary stents were first introduced to prevent arterial dissections and to eliminate vessel recoil and intimal hyperplasia associated with percutaneous transluminal coronary angioplasty. The stent application range has expanded as more experience was gained, and encouraging results have been obtained in the treatment of vascular diseases. Stents are currently used for support of additional body conduits, including the urethra, trachea, and esophagus. The rationale for bioresorbable stents is the support of a body conduit only during its healing process. The stent mass and strength decrease with time, and the mechanical load is gradually transferred to the surrounding tissue. Bioresorbable stents also enable longer term delivery of drugs to the conduit wall from an internal reservoir and abolish the need for a second surgery to remove the device. The present review describes recent advances in bioresorbable stents, focusing on drug-eluting bioresorbable stents for various applications. Controlled release of an active agent from a stent can be used to enhance healing of the surrounding tissues, to increase the implant's biocompatibility, as well as to help cure certain diseases. Because a lot of research in this field has been done by us, examples for these functions are described based mainly on developments in our laboratories.

Usefulness of 16-slice multislice spiral computed tomography for follow-up study of coronary stent implantation

BACKGROUND

Although multislice spiral computed tomography (MSCT) is a promising technique for non-invasive coronary angiography, its usefulness in patients with stent implantation remains unclear. The aim of the present study was to compare the usefulness of MSCT with that of invasive coronary angiography for evaluating coronary stent patency.

METHODS AND RESULTS

Thirty-one patients were enrolled after coronary stent implantation. Sixteen-slice MSCT scans were performed (39.0+/-21.8 days) before follow-up coronary angiography. After assigning an image score based on luminal visibility (1= poor, 2= fair, 3= good), factors determing image quality were analyzed. Among 42 implanted stents, 33 (78%) were assigned an image score of 3, 2 (5%) a score of 2, and 7 (17%) a score of 1. Image scores among stents with diameters >or=3.5 mm were significantly (p<0.05) higher than among smaller stents (<or=3.0 mm). Stent strut thickness did not affect image quality, but coronary calcification significantly (p<0.01) hampered the image quality. After excluding 7 stents with image scores of 1, the sensitivity, specificity, positive and negative predictive values of MSCT to identify patent stents were 83%, 90%, 63% and 96%, respectively.

CONCLUSIONS

MSCT can provide useful and valuable clinical information for assessing stent patency during the follow-up period when patients are treated with relatively large diameter coronary stents.

Histopathological findings of new in-stent lesions developed beyond five years

We analyzed 14 cases of new lesions inside implanted bare-metal stents. In every case, there was no angiographic restenosis within 3 years, but a new lesion was observed inside a stented segment at long-term follow-up (>5 years). Fourteen cases were evaluated: 9 with Wiktor stents, 2 with Palmaz-Schatz stents, and 3 with ACS Multilink stents. The interval from stent implantation to follow-up angiography was 63-147 months (89 +/- 23). Thirteen lesions were treated by percutaneous coronary intervention (PCI) and stenotic tissue was obtained by directional coronary atherectomy (DCA) in 10 cases. All retrieved samples were composed of newly developed atherosclerosis facing the healed neointimal layer, and four samples showed histopathological findings of acute coronary syndrome. Stent struts were retrieved in four cases and no inflammation was observed surrounding them. Qualitative and quantitative analysis of stent struts was performed in two cases that showed no metal corrosion. These findings suggest that new atherosclerotic progression occurred inside the implanted stent without peristrut inflammation.

Sustained increased risk of adverse cardiac events over 5 years after implantation of gold-coated coronary stents

OBJECTIVE

To study the 5-year outcome of patients treated with gold-coated stent placement.

BACKGROUND

We have previously shown in the setting of a randomized trial that gold-coated stents are associated with worse mid-term outcome, mainly because of an increased risk of restenosis, compared to uncoated stents. The long-term outcome and, in particular, mortality risk after implantation of gold-coated stents are not known.

METHODS

A total of 731 patients with symptoms or signs of ischemia received randomly either a gold-coated (n = 367) or an uncoated steel stent (n = 364) of identical design. Patients were clinically followed-up at 1 and 5 years. The primary endpoint of the study was the composite of major cardiac events (death, myocardial infarction, or target vessel revascularization (TVR)). The incidence of death was a secondary endpoint.

RESULTS

Five-year follow-up was available in 97.5% of the patients. The composite of death, myocardial infarction, or TVR occurred in 51% of the patients treated with gold-coated stents and 40% of the patients treated with uncoated stents (P = 0.005). Of note, there was a marked increase in the absolute difference in mortality between patients in the gold-coated and uncoated stent groups, from 1.6% at 1 year to 4.9% after 5-year follow-up (P = 0.09). A multivariate analysis showed that gold-coated stent implantation was independently associated with 5-year mortality (hazard ratio, 1.46; 95% confidence interval, 1.02-2.09; P = 0.04).

CONCLUSIONS

Gold-coated stents are associated with a sustained increased overall risk for major cardiac events, and notably, they may increase the long-term mortality risk.

Predictors of Sub-Acute Stent Thrombosis in Acute Myocardial Infarction Patients Following Primary Coronary Stenting With Bare Metal Stent

BACKGROUND

The aim of the present study was to identify the relationship between sub-acute stent thrombosis (SAT) and acute-phase inflammatory reactants, such as high-sensitivity C-reactive protein (hs-CRP) and serum amyloid-A protein (SAA), in patients with acute myocardial infarction (AMI) successfully treated with primary coronary stenting.

METHODS AND RESULTS

The 381 consecutive AMI subjects were reperfused by primary coronary stenting within 24 h of onset. SAT was confirmed angiographically in 10 patients (2.6%). There were no significant differences between the patients with or without SAT in terms of patient characteristics, Killip classification on admission, or stent diameter, nor were there significant differences between the 2 groups in terms of left ventricular function soon after stenting (left ventricular ejection fraction) or end-diastolic volume index. The plasma levels of both hs-CRP and SAA were significantly higher in the SAT patients than in the others (hs-CRP: 6.7+/-6.7 mg/dl vs 3.3+/-3.8 mg/dl, p=0.007; SAA: 699+/-812 mug/dl vs 208+/-273 mug/dl, p<0.0001). Multivariate analysis identified SAA as an independent predictor of SAT (risk ratio: 4.9, 95% confidence interval: 1.7-14.9, p<0.05).

CONCLUSION

In patients with AMI who are treated with primary coronary stenting, inflammation may be closely related to SAT, for which SAA is a useful predictor.

Peristent remodeling and neointimal suppression 2 years after polymer-based, paclitaxel-eluting stent implantation: insights from serial intravascular ultrasound analysis in the TAXUS II study

BACKGROUND

The purpose of this study was to evaluate long-term vascular responses as long as 2 years after implantation of polymer-based, paclitaxel-eluting stents in contrast to uncoated stents.

METHODS AND RESULTS

TAXUS II is a randomized, double-blind trial comparing slow-release (SR) and moderate-release (MR) TAXUS stents with bare-metal control stents (BMSs). One hundred sixty-one event-free patients (SR, 43; MR, 41; and BMS, 77) underwent serial intravascular ultrasound (IVUS) analysis after the procedure and at 6 months and 2 years. At 2 years, neointimal responses continued to be significantly suppressed in the SR and MR groups when compared with the BMS group (BMS, 1.49+/-1.12 mm2; SR, 0.94+/-0.76 mm2 [P=0.004]; and MR, 1.06+/-0.90 mm2 [P=0.02]). Between 6 months and 2 years, the BMS group showed compaction of the neointima (Delta, -0.22+/-1.05 mm2 [P=0.08]). In contrast, both the SR and MR groups exhibited an increase (Delta SR, 0.30+/-0.76 mm2 (P=0.01); MR, 0.41+/-0.94 mm2 [P=0.009]). Between 6 months and 2 years, the initial increase in plaque outside the stent regressed in the BMS and SR groups to levels comparable to those after the procedure, whereas expansive remodeling partially regressed in the MR group (Delta between after the procedure and 2 years BMS, -0.34+/-1.28 mm2 [P=0.05]; SR, -0.02+/-1.40 mm2 [P=0.93]; MR, 0.32+/-1.56 mm2 [P=0.27]).

CONCLUSIONS

The 2-year follow-up demonstrates that neointimal suppression was dose independent and that this effect was still sustained at 2 years. However, the increase in area outside the stent seen at 6 months regressed to different extents in a dose-dependent manner at 2 years.

Brachytherapy with gamma radiation of a coronary artery for in-stent restenosis may induce the regression of in-stent restenosis of an adjacent coronary artery without angioplasty. First case report and review of the literature

Here, we present a case of a 63-year-old male who presented with in-stent restenosis of two coronary arteries simultaneously (mid circumflex and proximal ramus). After the brachytherapy of the circumflex artery for in-stent restenosis, the patient refused the staged procedure for the ramus in-stent restenosis. After approximately 2 years, the patient underwent coronary angiography for recurrent chest pain. Surprisingly, the proximal ramus stent showed marked regression of in-stent restenosis. We hypothesized that the gamma brachytherapy of the circumflex artery could have induced the regression of in-stent restenosis of the adjacent ramus artery due to the deep tissue penetration of gamma radiation. Based on our observation, we believe that in the treatment of in-stent restenosis of a coronary artery, the initial balloon angioplasty may not be as important as the radiation itself. This observation warrants further study to evaluate the effect of external or internal radiation on in-stent restenosis without balloon angioplasty. If our hypothesis is confirmed, the treatment of in-stent restenosis with external radiation could substantially simplify the treatment of this disease. This case report follows a brief review of the literature.

Middle cerebral artery stenosis: endovascular and surgical options

Atherosclerotic middle cerebral artery stenosis is a rare but potentially devastating cause of cerebral ischemia and stroke. While medical management remains the mainstay for stroke prevention, surgical and/or endovascular intervention is indicated in selected patients. This article reviews the role of surgery and endovascular techniques in the treatment of middle cerebral artery stenosis based on its natural history, pathophysiology, and prognosis when treated medically.

A Cost-Effectiveness Analysis of a Hypothetical Catheter-Based Strategy for the Detection and Treatment of Vulnerable Coronary Plaques with Drug-Eluting Stents

AIM

Extensive efforts are underway to develop methods for the detection and treatment of vulnerable/high-risk coronary artery plaques. We utilized decision analysis to evaluate the hypothetical clinical benefits and cost-effectiveness of a catheter-based strategy.

METHODS AND RESULTS

Currently, stenotic coronary plaques are treated without regard to vulnerability. In a new strategy, vulnerable coronary plaques are detected with a catheter-based test and treated with a drug-eluting stent, regardless of degree of stenosis. A Markov-decision model was developed to compare the new strategy with current practice. Monte Carlo simulations were performed from a societal perspective, costs were converted to year 2003 U.S. dollars, and future costs and outcomes were discounted at 3%. Sensitivity analyses were performed to evaluate the effect of assumptions on variables such as the prevalence of vulnerable plaques and treatment effect. In 60-year-old male patients with coronary stenoses the new strategy would be less expensive and more effective than current practice (37,045 dollars vs 38,257 dollars and 10.23 vs 9.86 quality-adjusted life years (QALYs), respectively). The benefits of the new strategy were robust in sensitivity analyses (e.g., if the prevalence of vulnerable plaques in this patient group was 50% or more and the sensitivity and specificity of the new test were at least 0.80).

CONCLUSION

In selected patients with coronary artery stenosis, the detection of vulnerable plaques with a catheter-based test followed by their treatment with a drug-eluting stent could be a less expensive and more effective strategy than current practice. If applied to 1 million such patients in the United States undergoing catheterization, the new strategy would add 370,000 QALYs and save 1.2 billion dollars per year.

Coronary artery stents: identification and evaluation

First introduced in the 1980s, the coronary stent has been used to reduce the rate of arterial restenosis. Coronary stent implantation is currently a common procedure performed by interventional cardiologists, and the market for development and design is constantly expanding and evolving. This article was designed to assist pathologists in the accurate identification of coronary stents that are currently available, in addition to some that are no longer being implanted. The stents reviewed here were chosen based on frequency of use and/or occurrence in the literature. Some of the newer models have yet to undergo extensive clinical testing. The summaries accompanying each stent include concise physical descriptions and documented complications, intended to serve as a guide for the investigating pathologist.

Outcome of patients with prior percutaneous revascularization undergoing repeat coronary intervention (from the PRESTO Trial)

Patients with previous percutaneous coronary intervention (PCI) are often excluded from clinical trials. As a result, limited data are available on the long-term outcome of such patients undergoing repeat PCI. In this study, we assessed the impact of previous PCI on outcomes in patients undergoing repeat PCI. We compared the baseline features and outcomes of 7,056 patients without previous PCI (group I) with those of 1,281 patients with previous PCI of the original target lesion (group II) and 1,408 patients with previous PCI of a nontarget lesion (group III) undergoing PCI in the Prevention of Restenosis with Tranilast and its Outcomes (PRESTO) trial. Compared with patients in group I, patients in groups II and III were more likely to have diabetes (25% and 24% vs 21%, p <0.02), previous myocardial infarction (51% and 56% vs 29%, p <0.001), and ostial lesions (10% and 7% vs 5%, p <0.001), and less likely to have, as their indication for PCI, myocardial infarction (2% and 7% vs 17%, p <0.001). At 1 month, major adverse cardiac events, including death, myocardial infarction, and repeat revascularization, were low and similar in all 3 groups. Compared with patients in group I, the risk of major adverse cardiac events at 9 months was significantly increased for patients in groups II (34.1% vs 18.6%, relative risk [RR] 2.03, adjusted RR 1.78, 95% confidence interval 1.58 to 2.01) and III (23.9% vs 18.6%, RR 1.30, adjusted RR 1.16, 95% confidence interval 1.02 to 1.33). The increased risk of major adverse cardiac events was entirely due to higher rates of repeat revascularization. In conclusion, despite similar short-term outcomes, patients with previous PCI undergoing PCI of either target or nontarget lesions had lower event-free survival at 9 months of follow-up.

Sirolimus-eluting and paclitaxel-eluting stents for coronary revascularization

BACKGROUND

Sirolimus-eluting stents and paclitaxel-eluting stents, as compared with bare-metal stents, reduce the risk of restenosis. It is unclear whether there are differences in safety and efficacy between the two types of drug-eluting stents.

METHODS

We conducted a randomized, controlled, single-blind trial comparing sirolimus-eluting stents with paclitaxel-eluting stents in 1012 patients undergoing percutaneous coronary intervention. The primary end point was a composite of major adverse cardiac events (death from cardiac causes, myocardial infarction, and ischemia-driven revascularization of the target lesion) by nine months. Follow-up angiography was completed in 540 of 1012 patients (53.4 percent).

RESULTS

The two groups had similar baseline clinical and angiographic characteristics. The rate of major adverse cardiac events at nine months was 6.2 percent in the sirolimus-stent group and 10.8 percent in the paclitaxel-stent group (hazard ratio, 0.56; 95 percent confidence interval, 0.36 to 0.86; P=0.009). The difference was driven by a lower rate of target-lesion revascularization in the sirolimus-stent group than in the paclitaxel-stent group (4.8 percent vs. 8.3 percent; hazard ratio, 0.56; 95 percent confidence interval, 0.34 to 0.93; P=0.03). Rates of death from cardiac causes were 0.6 percent in the sirolimus-stent group and 1.6 percent in the paclitaxel-stent group (P=0.15); the rates of myocardial infarction were 2.8 percent and 3.5 percent, respectively (P=0.49); and the rates of angiographic restenosis were 6.6 percent and 11.7 percent, respectively (P=0.02).

CONCLUSIONS

As compared with paclitaxel-eluting stents, the use of sirolimus-eluting stents results in fewer major adverse cardiac events, primarily by decreasing the rates of clinical and angiographic restenosis.

Two-year-plus follow-up of a paclitaxel-eluting stent in de novo coronary narrowings (TAXUS I)

Early results with polymer-based paclitaxel-eluting stents have shown significant improvements in the clinical and angiographic parameters of restenosis, as well as excellent safety outcomes. However, the duration of these beneficial effects is unknown. Therefore, the clinical outcomes of the TAXUS I study population were evaluated at 2- and 3-year follow-up. In TAXUS I, 61 patients with single, focal coronary lesions were randomly assigned to receive either a paclitaxel-eluting TAXUS stent (n = 31) or a bare metal control stent (n = 30). Low rates of composite major adverse cardiac events (MACEs) reported at 1-year follow-up (3.2% TAXUS vs 10.0% control) were maintained at 2 and 3 years, with no additional MACEs in either treatment group 1 year after implantation. The single target vessel revascularization in the TAXUS group was remote from the target lesion in contrast to 3 target lesion revascularizations in the control group.