Emergency coronary stenting for dissection during percutaneous transluminal coronary angioplasty: angiographic follow-up after stenting and after repeat angioplasty of the stented segment

Characterization of fracture behavior of human atherosclerotic fibrous caps using a miniature single edge notched tensile test

One well-established cause of ischemic stroke is atherosclerotic plaque rupture in the carotid artery. Rupture occurs when a tear in the fibrous cap exposes highly thrombogenic material in the lipid core. Though some fibrous cap material properties have been measured, such as ultimate tensile strength and stress-strain responses, there has been very little, if any, data published regarding the fracture behavior of atherosclerotic fibrous caps. This study aims to characterize the qualitative and quantitative fracture behavior of human atherosclerotic plaque tissue obtained from carotid endarterectomy samples using two different metrics. Uniaxial tensile experiments along with miniature single edge notched tensile (MSENT) experiments were performed on strips of isolated fibrous cap. Crack tip opening displacement (CTOD) and stress in the un-cracked segment (UCS) were measured at failure in fibrous cap MSENT specimens subjected to uniaxial tensile loading. Both CTOD and the degree of crack blunting, measured as the radius of curvature of the crack tip, increased as tearing propagated through the tissue. Higher initial stress in the UCS is significantly correlated with higher collagen content and lower macrophage content in the fibrous cap (ρ=0.77, P=0.009; ρ=-0.64, P=0.047; respectively). Trends in the data show that higher CTOD is inversely related to collagen content, though the sample size in this study is insufficient to statistically substantiate this relationship. To the authors' knowledge, this is the pioneering study examining the fracture behavior of fibrous caps and the first use of the CTOD metric in vascular tissue.

STATEMENT OF SIGNIFICANCE

A tear in the fibrous cap of atherosclerotic plaque can lead to ischemic stroke or myocardial infarction. While there is some information in the literature regarding quantitative measures of fibrous cap failure, there is little information regarding the behavior of the tissue during failure. This study examines the failure behavior of fibrous caps both qualitatively, by examining how and where the tissue fails, and quantitatively, by measuring (a) crack tip opening displacement (CTOD) in vascular tissue for the first time and (b) uniaxial stress in the un-cracked segment (UCS). This study shows that both metrics should be evaluated when assessing plaque vulnerability.

Clinical outcomes after PCI treatment of very long lesions with the XIENCE V everolimus eluting stent; Pooled analysis from the SPIRIT and XIENCE V USA prospective multicenter trials

BACKGROUND

Lesion length has been an important factor in predicting a worse outcome after percutaneous coronary interventions (PCI); however, the safety and efficacy of second-generation drug eluting stents in very long coronary lesions has not been validated in large scale randomized controlled trials.

METHODS

We performed a patient level pooled analysis of 13,266 patients undergoing planned overlapping stent treatment of very long coronary lesions with the XIENCE V everolimus eluting coronary stent system from 6 trials evaluating the XIENCE V stent (Spirit II, III, IV, V, Spirit Small Vessel and XIENCE V USA). Patients were divided into two cohorts, a very long lesion (VLL) group (lesions ≥35 mm) and a control group (lesions >24 to <35 mm). The primary outcome measures were Target Lesion Failure (TLF), Major Adverse Cardiac Events (MACE), and Academic Research Consortium (ARC) defined definite and probable stent thrombosis at 1 year.

RESULTS

A total of 13,266 patients were included in the pooled analysis of which 2.4% (323 patients with 328 total lesions) had a mean lesion length of 47.1 ± 13.7 mm in the VLL group which were compared to controls comprised of 3.6% of the cohort (482 patients with 500 total lesions) with mean lesion length of 28.1 ± 2.4 mm.There was no significant difference in the rates of TLF between the VVL and control groups (8.9 vs. 10%, P = 0.63), MACE (9.2 vs. 10%, P = 0.74) or stent thrombosis (1.6 vs. 1.5%, P = 0.92) at 1 year.

CONCLUSIONS

In the treatment of very long coronary lesions, the XIENCE V stent appears as safe and effective as percutaneous coronary interventions for long lesions. © 2016 Wiley Periodicals, Inc.

Impact of post-dilatation with a focal expanding balloon for optimization of intracoronary stenting

Optimal stenting frequently requires additional stent post-dilatation following initial stent deployment. Stent post-dilatation using a focal expanding balloon (FB) that grows 0.5 mm larger centrally may achieve a larger final stent lumen with fewer stent edge injuries as compared to use of a conventional unidiameter balloon (UB). In the present prospective study, of 128 stented lesions in 122 patients, 63 lesions had stents dilated with FB (Group F), while 65 lesions had stents dilated with UB (Group U). All balloons for stent post-dilatation were half-sized up to reference diameter by on-line quantitative coronary analysis. There were no differences in the reference diameter, pre-procedural minimal lumen diameter (MLD), balloon/artery ratio, and final balloon pressure between the two groups. Post-procedural MLD in Group F was significantly larger than that in Group U (3.03 +/- 0.43 vs 2.80 +/- 0.47 mm, P < 0.001). Stent edge injury occurred in 4 patients, and stent thrombosis in 2 patients in Group U, but not in Group F. Minimal lumen diameter at 6 months in Group F was significantly larger than that in Group U (2.05 +/- 0.63 vs 1.82 +/- 0.66 mm, P < 0.05), and incidence of restenosis was significantly lower in Group F than Group U (9% vs 22%, P < 0.05). By using a focal expanding balloon for stent optimization, a larger stent lumen can be obtained safely, and subsequent incidence of restenosis can be reduced.

Stent-induced expression and activation of the leukocyte integrin Mac-1 is associated with neointimal thickening and restenosis

BACKGROUND

Increased expression of the beta2 integrin Mac-1 (CD11b/CD18, alphaMbeta2), which is responsible for firm leukocyte adhesion to platelets and fibrinogen at injured vessels, is found in association with neointimal hyperplasia after coronary interventions. The role of Mac-1 in the pathophysiology of restenosis is incompletely defined. To clarify further the role of Mac-1, we determined whether coronary stenting induced activation of Mac-1, which is required for high-affinity receptor-ligand interactions.

METHODS AND RESULTS

Expression of CD11b (alpha-subunit of Mac-1) and binding of 8B2 (monoclonal antibody against an activation-dependent neoepitope of Mac-1) on the surface of polymorphonuclear leukocytes were analyzed in 62 patients undergoing coronary stenting using flow cytometric analysis of whole blood obtained from the coronary sinus and femoral vein. Transcardiac CD11b expression increased significantly at 24 hours and maximally at 48 hours after stenting; 8B2 began to increase at 10 minutes and was maximally increased at 48 hours after stenting. These changes were more prominent in patients with subsequent restenosis. Multiple regression analysis showed that the late lumen loss by quantitative coronary angiographic analysis was independently correlated with the CD11b increase (R=0.42, P<0.01) and the 8B2 increase (R=0.55, P<0.001) 48 hours after the procedure. Mac-1 activation, as assessed by 8B2 binding, was the most powerful predictor of late lumen loss.

CONCLUSIONS

Coronary stenting produced upregulation and early activation of the leukocyte integrin Mac-1, which is associated with late lumen loss and restenosis. These data support a role for inflammation in neointimal thickening and suggest the validity of targeting leukocyte recruitment for preventing clinical restenosis.

Coronary artery brachytherapy

Coronary artery disease is the leading cause of mortality in the West with over 1.2 million angioplasties performed annually. Despite the introduction of stents, restenosis occurs in 30-40% of vessels, which until recently has only been treated effectively by coronary artery bypass surgery. Coronary artery brachytherapy appears to provide an alternative, less invasive remedy. The mechanisms of restenosis and how these are inhibited by radiation are described here. The practicalities of radiation delivery and the history of the development of intravascular radiation as an effective clinical tool are outlined. Finally, the pitfalls of the current technology and the areas in which future research must be targeted for the field to develop are discussed.

Resource utilization, cost, and health status impacts of coronary stent versus "optimal" percutaneous coronary angioplasty: results from the OPUS-I trial

In the OPUS-I trial, primary coronary stent implantation reduced 6-month composite incidence of death, myocardial infarction, cardiac surgery, or target vessel revascularization relative to a strategy of initial PTCA with provisional stenting in patients undergoing single vessel coronary angioplasty. The purpose of this research was to compare the economic and health status impacts of each treatment strategy. Resource utilization data were collected for the 479 patients randomized in OPUS-I. Itemized cost estimates were derived from primary hospital charge data gathered in previous multicenter trials evaluating coronary stents, and adjusted to approximate 1997 Medicare-based costs for a cardiac population. Health status at 6 months was assessed using the Seattle Angina Questionnaire (SAQ). Initial procedure related costs for patients treated with a primary stent strategy were higher than those treated with optimal PTCA/provisional stent ($5,389 vs $4,339, P < 0.001). Costs of initial hospitalization were also higher for patients in the primary stent group ($9,234 vs $8,434, P < 0.01) chiefly because of the cost differences in the index revascularization. Mean 6-month costs were similar in the two groups; however, there was a slight cost advantage associated with primary stenting. Bootstrap replication of 6-month cost data sustained the economic attractiveness of the primary stent strategy. There were no differences in SAQ scores between treatment groups. In patients undergoing single vessel coronary angioplasty, routine stent implantation improves important clinical outcomes at comparable, or even reduced cost, compared to a strategy of initial balloon angioplasty with provisional stenting.

Frequency of abrupt vessel closure and side branch occlusion after percutaneous coronary intervention in a 6.5-year period (1994 to 2000) at a single medical center

The aims of this study were to analyze the contemporary trends in the changing incidence of abrupt vessel closure (AVC) after percutaneous coronary intervention (PCI), to determine the impact of intracoronary stenting and glycoprotein IIb/IIIa inhibitors (GPIs) on complication rates and etiologies, and to determine the incidence of side branch occlusion (SBO) as the etiology of AVC in the stent era, complications occurring during 3,300 consecutive PCIs performed from April 1994 to December 2000 at a single referral institution. In this consecutive patient cohort of PCI cases collected over a 6.5-year period, AVC occurred in 103 of 3,300 cases (3.12%). Linear regression analysis over this time frame documented a steadily decreasing incidence of AVC from 5.9% in 1994 to 1.1% in 2000 (-0.76%/per year, 95% confidence interval -0.99 to 0.52, p <0.05). Analysis using Pearson's correlation showed that the decreasing incidence of AVC was inversely correlated with the increasing percentage of intracoronary stents placed over this time period (r = -0.94, p <0.001). Additionally, GPI use increased from 0% in 1995 to 36.0% in 2000 (p = 0.009). The absolute incidence of SBO of a major branch vessel remained relatively stable over this 6.5-year period. However, SBO appeared to be increasing as the etiology of AVC, and accounted for 9.0% of AVC in 1995 compared with 28.0% of AVC in 2000. This increasing trend of the percentage of SBO as the etiology of AVC appeared to correlate with the increased use of stents (r = 0.85, p = 0.015). Thus, the incidence of AVC steadily decreased over the 6.5-year time period, and was associated with the increased use of stents and GPIs; conversely, SBO accounted for an increasing percentage of AVC over this time period.

Stent placement for non-STRESS/BENESTENT lesions: a critical review

Stenting lesions with favorable characteristics as required for inclusion in the STRESS/BENESTENT trials have yielded superior results to that of PTCA alone. Results for less favorable lesions such as in small vessels, diffuse disease, ostial disease, and saphenous vein grafts are less well established. This review seeks to analyze available data for stent placement in this subset of non-STRESS/BENESTENT lesions.

Optimum percutaneous transluminal coronary angioplasty compared with routine stent strategy trial (OPUS-1): a randomised trial

BACKGROUND

Whether routine implantation of coronary stents is the best strategy to treat flow-limiting coronary stenoses is unclear. An alternative approach is to do balloon angioplasty and provisionally use stents only to treat suboptimum results. We did a multicentre trial to compare the outcomes of patients treated with these strategies.

METHODS

We randomly assigned 479 patients undergoing single-vessel coronary angioplasty routine stent implantation or initial balloon angioplasty and provisional stenting. We followed up patients for 6 months to determine the composite rate of death, myocardial infarction, cardiac surgery, and target-vessel revascularisation.

RESULTS

Stents were implanted in 227 (98.7%) of the patients assigned routine stenting. 93 (37%) patients assigned balloon angioplasty had at least one stent placed because of suboptimum angioplasty results. At 6 months the composite endpoint was significantly lower in the routine stent strategy (14 events, 6.1%) than with the strategy of balloon angioplasty with provisional stenting (37 events, 14.9%, p=0.003). The cost of the initial revascularisation procedure was higher than when a routine stent strategy was used (US$389 vs $339, p<0.001) but at 6 months, average per-patient hospital costs did not differ ($10,206 vs $10,490). Bootstrap replication of 6-month cost data showed continued economic benefit of the routine stent strategy.

INTERPRETATION

Routine stent implantation leads to better acute and long-term clinical outcomes at a cost similar to that of initial balloon angioplasty with provisional stenting.

Longitudinal straightening effect of stents is an additional predictor for major adverse cardiac events. Austrian Wiktor Stent Study Group and European Paragon Stent Investigators

OBJECTIVES

The aim of this study was to perform an investigation of the effects of the longitudinal straightening of coronary arteries by stents and the possible association with major adverse cardiac events (MACE) (primary end point) and angiographic restenosis (secondary end point).

BACKGROUND

Stent deployment straightens a tortuous artery, and any consequent arterial longitudinal stretch may contribute to MACE and stent restenosis severity.

METHODS

Clinical, qualitative and quantitative angiographic data on 404 patients with single stent implantation were subjected to multivariate nominal logistic regression analysis for the prediction of MACE. The predictive accuracy, sensitivity and specificity values and cut-off points of the continuous variables were determined via receiver operating characteristics curves. The longitudinal straightening effect of stents was characterized through the changes in vessel angle (defined by the tangents to the proximal and distal parts of the stenoses/stents).

RESULTS

Follow-up angiography on 354 patients revealed 73 cases of stent restenosis (> or =50% diameter stenosis). Coronary bypass surgery was performed in 4 patients and repeated percutaneous transluminal coronary angioplasty in 56 patients; acute myocardial infarction (AMI) occurred in 2 patients, and 4 patients died during the follow-up. The overall incidence of MACE (death, AMI and revascularization) was 16.3% (66 patients). The best predictive accuracies and sensitivities/specificities of factors indicative of MACE were found for the minimal lumen diameter (MLD) at follow-up (predictive accuracy: 0.9305, sensitivity/specificity: 86.6%), the post-stent MLD (0.773, 77.2%), the percent diameter stenosis (%DS) at follow-up (0.9432, 87.1%), the prestent vessel angulation (0.6797, 68.2%) and the poststent changes in vessel angulation (0.6279, 62.2%). Multivariate nominal logistic regression analysis demonstrated that a poststent MLD < or =2.63 mm (p = 0.0017, odds ratio [OR] = 17.961, 95% confidence interval [CI] = 17.45-20.428), an MLD at follow-up < or =1.7 mm (p = 0.0059, OR = 11.880, 95% CI = 11.490-14.093), a %DS at follow-up > or =42.2% (p = 0.0000, OR = 49.553, 95% CI = 48.024-53.507), a prestent vessel angulation > or =33.5 degrees (p = 0.0477, OR = 5.404, 95% CI = 5.382-7.142) and poststent changes in vessel angulation > or =9.1 degrees (p = 0.0026, OR = 19.161, 95% CI = 18.562-21.750) were significant predictors for MACE. Multiple linear regression revealed that the poststent MLD (multivariate p = 0.0001), the MLD at follow-up (p = 0.0000), the prestent vessel angulation (p = 0.0431) and the changes in vessel angulation after stent implantation (p = 0.0316) were significant independent variables predicting angiographic stent restenosis severity.

CONCLUSIONS

The longitudinal straightening effect of coronary artery stents contributes significantly to the occurrence of MACE and angiographic restenosis, and this finding may have an impact on future stent design.

Pathology of in-stent restenosis

The process of in-stent restenosis parallels wound healing responses. Stent deployment results in early thrombus deposition and acute inflammation, granulation tissue development, and ultimately smooth muscle cell proliferation and extracellular matrix synthesis. The severity of arterial injury during stent placement correlates with increased inflammation and late neointimal growth. These pathological findings provide useful targets for therapies aimed at reducing the incidence of in-stent restenosis.

Clinical and angiographic follow-up after balloon angioplasty with provisional stenting for coronary in-stent restenosis

The objective of this study was to assess the angiographic and clinical outcome of patients with coronary in-stent restenosis treated with balloon angioplasty with provisional stenting. The study included 375 consecutive patients with in-stent restenosis managed with balloon angioplasty alone or combined with stenting. Clinical events were recorded during a 1-year follow-up period and quantitative analysis was performed on 6-month angiographic data. Of the 373 patients (451 lesions) with a successful procedure, 273 were treated with angioplasty alone and 100 with additional stenting. Target lesion revascularization was required in 23.7% of the patients: 20.7% in patients with angioplasty and 31.0% in patients with stenting. Angiographic restenosis rate was 38.9%: 35.8% in the angioplasty group and 47.7% in the stent group. Stenting in small vessels was associated with a much higher restenosis rate than in larger vessels (65.6% vs. 37.5%, respectively; P = 0.01). Thus, repeat balloon angioplasty with provisional stenting for in-stent restenosis is a safe treatment strategy associated with a relatively favorable long-term outcome. However, the long-term results might be improved if additional stenting is avoided especially in small vessels. Cathet. Cardiovasc. Intervent. 48:151-156, 1999.

Early recovery of coronary flow reserve after stent implantation as assessed by positron emission tomography

OBJECTIVES

The aim of this study was to quantitatively evaluate myocardial flow reserve in patients early after coronary stent implantation using positron emission tomography.

BACKGROUND

Delayed restoration of coronary flow reserve after percutaneous transluminal coronary angioplasty (PTCA) has been observed using a variety of techniques. Altered distal vasoregulation as well as residual stenosis have been considered possible explanations for this phenomenon. Although the implantation of stents may influence some of these mechanisms, little data are available characterizing coronary flow reserve early after stent placement.

METHODS

In 14 patients 1.6 +/- 0.6 days after stenting, N-13-ammonia positron emission tomographic studies were performed at rest and during adenosine-induced vasodilation. Myocardial blood flow was quantified using a three-compartment model. Rest and stress flow data, as well as coronary flow reserve of stented vascular territories, were compared with that of remote areas.

RESULTS

The stenosis decreased from 72.1 +/- 7.3% to 3.7 +/- 6.7% after stent implantation. Coronary flow in the stented areas did not differ significantly from that in remote areas either at rest (76.1 +/- 18.5 and 75.7 +/- 17.7 ml/min/100 g, respectively), or during maximal vasodilation (205.5 +/- 59.9 and 179.4 +/- 47.4 ml/min/100 g, respectively). In addition, there was no significant difference in the calculated values of coronary reserve of these two regions (2.74 +/- 0.64 and 2.43 +/- 0.55, respectively).

CONCLUSIONS

The mechanical support of dilated arteries by a stent not only restores the macroscopic integrity of epicardial arteries, but also results, in contrast to conventional PTCA procedures, in early recovery of flow reserve.

Stented segment length as an independent predictor of restenosis

OBJECTIVES

We sought to evaluate the relation between stented segment length and restenosis.

BACKGROUND

Multiple or long coronary stents are now being implanted in long lesions or in tandem lesions. A longer stented segment might result in a higher probability of restenosis. However, there is little information available on the relation between stented segment length and restenosis.

METHODS

Between April 1995 and December 1996, 725 patients with 1,090 lesions underwent stenting. Lesions were divided into three groups according to the length of the stented segment: 1) group I (n = 565): stented segment length < or =20 mm; 2) group II (n = 278): stented segment length >20 but < or =35 mm; and 3) group III (n = 247): stented segment length >35 mm.

RESULTS

There was no significant difference in the incidence of subacute stent thrombosis among the three groups (0.4% in group I, 0.4% in group II, 1.2% in group III; p = NS). The minimal lumen diameter (MLD) after stenting was greater in group I than in group III (3.04 +/- 0.60 mm in group I, 3.01 +/- 0.54 mm in group II, 2.91 +/- 0.58 mm in group III; p < 0.05). At follow up, a smaller MLD was observed in group III as compared with group I and group II (2.04 +/- 0.93 mm in group I, 1.92 +/- 1.00 mm in group II, 1.47 +/- 0.97 mm in group III; p < 0.01). The restenosis rates were 23.9% in group I, 34.6% in group II and 47.2% in group III (p < 0.01). Using multivariate analysis, the longer stented segment, the angiographic reference vessel diameter and the percent diameter stenosis after stenting were independent predictors of restenosis.

CONCLUSIONS

The present study shows that a longer stented segment is an independent predictor of restenosis without an influence on the risk of subacute thrombosis.

Quantitative angiographic analysis of stent restenosis in the Scripps Coronary Radiation to Inhibit Intimal Proliferation Post Stenting (SCRIPPS) Trial

To identify luminal dimension changes occurring within the stent alone and within the stent + margin segment, we reviewed the quantitative angiographic results obtained from the Scripps Coronary Radiation to Inhibit Proliferation Post Stenting (SCRIPPS) trial, a prospective randomized trial assessing the effect of iridium-192 (Ir-192) on the prevention of stent restenosis. Fifty-five patients were randomly assigned to receive Ir-192 or placebo sources after successful intervention. Procedural and 6-month follow-up cineangiograms were quantitatively reviewed in 52 patients to identify changes within the stent and the stent + margin segment. The percent diameter stenosis was lower within the stent than within the stent + margin segment after the procedure (6 +/- 22% vs 21+/- 15%, p <0.0001) and at follow-up (28 +/- 29% vs 42 +/- 21%, p <0.0001). As a result, a lower restenosis rate was found within the stent than within the stent + margin (25% vs 37%, p <0.0001); isolated stent margin restenosis occurred in 11.5% of lesions. Treatment with Ir-192 reduced restenosis within the stent (8% vs 39%; p = 0.010) and within the stent + margin segment (17% vs 54%; p = 0.010); the reduction in restenosis at the margin only (8.3% vs 14.3%, p = 0.503) was not significant. The lowest relative risk for restenosis resulting from Ir-192 occurred within the stent (0.21; 95% confidence interval [CI] 0.05 to 0.86) compared with the stent + margin segment (0.31; 95% CI 0.12 to 0.81) or the stent margin (0.58; 95% CI 0.12 to 2.91). In the SCRIPPS trial, 32% of restenosis occurred at the stent margins. Treatment with Ir-192 reduced restenosis primarily within the stent rather than the margin. Whether extending the treatment length to fully include the stent margins will further reduce restenosis requires further study.

Results of coronary stenting after delayed angioplasty of the culprit vessel in patients with recent myocardial infarction

Little information is available concerning the effect of late coronary stenting in patients with recent myocardial infarction, especially long-term results. We retrospectively reviewed our results of 57 stent placements in 52 consecutive patients who received stents at an infarct-related lesion 24 hr to 30 days after an acute myocardial infarctions (median, 14 days). The average age was 67 years; 90% were male. Two patients who suffered from acute stent thrombosis received revascularization again and two early deaths were due to refractory cardiogenic shock before discharge. Mean patient clinical follow-up was 18.3 +/- 6.5 months. There were 1 subacute stent thrombosis, 1 cardiogenic death, and 10 patients (20.8%) in total suffering from angina class II to IV. Angiographic follow-up was performed in 36 patients (80%) at a mean of 7.5 +/- 3.1 months. Of these 36 patients, only 1 (3% of the total population undergoing follow-up angiography) had reocclusion at follow-up, but restenosis existed in 18 patients (50%). We conclude that there is still relatively high incidence of angiographic recurrence that is often silent in long-term follow-up, though the long-term result of late stenting in recent MI is low incidence of reocclusion.

Effects of a positron-emitting vanadium-48 nitinol stent on experimental restenosis in porcine coronary arteries: an injury-response study

BACKGROUND

The major limitation of coronary stenting is restenosis due to exaggerated neointimal thickening. We evaluated a positron-emitting V48 nitinol stent in a porcine coronary model of restenosis.

METHODS AND RESULTS

Pigs (n = 16) received a control nonradioactive and a V48 stent (1.5 or 10.6 muCi) randomized to the left anterior descending artery (LAD) and right coronary artery (RCA). Histology, morphometric variables, and strut injury scores were evaluated after 32 days. Peristrut fibrinoid deposits were greater in the high-dose group (p < 0.0001). Control stent area stenosis (AS) and mean neointimal thickness (NIT) correlated with injury (r = 0.81 and 0.79, respectively). Higher-dose stents reduced AS by 20% (0.57 +/- 0.13 vs. 0.71 +/- 0.16; p = 0.029) and mean NIT by 35% (0.44 +/- 0.16 vs. 0.71 +/- 0.24mm; p = 0.001) compared with controls. Lower-dose 1.5-muCi stents did not differ from controls. NIT over individual struts was reduced in the high-dose group compared with controls by 0.18 mm for grade 1 injury, 0.31 mm for grade 2, and 0.38 mm for grade 3 (p < 0.02 for all comparisons).

CONCLUSIONS

1.5-muCi V48 nitinol stents did not influence vessel histology or restenotic parameters in pig coronary arteries. In contrast, 10.6-muCi stents created a distinctive histological picture consisting of increased fibrinoid deposits on the neointimal-facing side of the struts without cellular organization. Higher dose radioactive stents significantly reduced AS and mean NIT. The reduction in neointimal thickening was greatest when the depth of strut penetration into the vascular wall was most severe.

Influence of lesion length on restenosis after coronary stent placement

The length of a coronary lesion is a significant predictor of restenosis after balloon angioplasty. The influence of lesion length has not comprehensively been assessed after coronary stent placement. This study includes 2,736 consecutive patients with coronary stent placement. Only patients with recent or chronic occlusions before the intervention were excluded. Patients were divided in 2 groups: 573 patients with long lesions (> or = 15 mm) and 2,163 patients with short lesions (< 15 mm). There were no significant differences between the groups with respect to the procedural success rate and incidence of subacute thrombosis. One-year event-free survival was lower in patients with long lesions (73.3% vs 80.0%, p = 0.001). Six-month angiography was performed in 82.5% of the eligible patients. The incidence of binary restenosis (> or = 50% diameter stenosis) was higher in patients with long lesions (36.9% vs 27.9%, p <0.001). Similarly, patients with long lesions presented more late lumen loss than those with short lesions (1.29 +/- 0.89 vs 1.07 +/- 0.77 mm, p <0.001). Multivariate models for both binary restenosis and late lumen loss demonstrated that lesion length was an independent risk factor for restenosis. The risk was further increased by multiple stent placement and overlapping stents that were also independent risk factors of restenosis. Stented segment length did not show any independent effect. Therefore, long lesions represent an independent risk factor for restenosis after coronary stent placement. The results of this study suggest that a possible way to reduce the risk is to cover the lesion with a minimal number of nonoverlapping stents.

Long-term outcome and determinants of event-free survival in patients treated with balloon angioplasty for in-stent restenosis

Long-term prognosis and predictors of event-free survival were studied in 56 consecutive patients with in-stent restenosis successfully treated with balloon angioplasty. Most patients sustained prolonged clinical benefit, but during follow-up, those with diabetes or with a short time interval (<4 months) from stenting to repeat angioplasty experienced adverse cardiac events more often.

Pathology of bailout coronary stenting in human beings

OBJECTIVES

The aim of this study was to perform detailed postmortem analysis of bailout coronary stenting to gain insights into the mechanism of success or failure of the procedure. Bailout stenting is increasingly used for acute or threatened arterial closure after angioplasty. Few pathologic data from bailout stenting have been reported.

METHODS AND RESULTS

The coronary arteries from 6 cases of bailout stenting were analyzed at autopsy. All stents were placed for extensive coronary dissection or abrupt vessel closure after balloon angioplasty. Twenty stents (11 Palmaz-Schatz and 9 Gianturco-Roubin stents) were placed in 8 coronary arteries, ranging from 1 to 5 stents per artery. After stenting, angiography showed good coronary flow in 3 of 6 cases. All patients died secondary to acute myocardial infarction. Histologically, in all cases, the stents were well opposed to the coronary artery wall, with a focally widely patent lumen by compression of the dissection plane. However, in 4 of 6 cases, there was residual dissection present in the nonstented portion of the arteries proximal, proximal to, and between stents or distal to the stented segment, resulting in focal luminal compression or obstruction. In 2 cases, bailout stenting effectively covered the dissection and prevented luminal compression.

CONCLUSIONS

Bailout stenting for dissection after balloon angioplasty restores lumen patency in the stented segment. Residual dissection in nonstented segments adversely affects outcome and supports the need for continued development of new stents with increased trackability and tapering designs to more effectively treat major coronary dissections.

PlA polymorphism of platelet glycoprotein IIIa and risk of restenosis after coronary stent placement

BACKGROUND

Platelets play a central role in the process of restenosis after percutaneous coronary interventions. A polymorphism of platelet glycoprotein IIIa (PlA) has been associated with a higher risk of coronary thrombosis. We designed this prospective study to test the hypothesis that PlA polymorphism of glycoprotein IIIa is associated with an increased risk for restenosis after coronary stent placement.

METHODS AND RESULTS

The study included 1150 consecutive patients with successful coronary stent placement and 6-month follow-up with coronary angiography. The end point of the study was the incidence of angiographic restenosis (>/=50% diameter stenosis) at follow-up. Of the 1150 patients, 72.5% were homozygous for PlA1, 24.7% were heterozygous (PlA1/A2), and 2.8% were homozygous for PlA2. Patients with the PlA2 allele demonstrated a significantly higher restenosis rate than did those without (47% versus 38%; OR, 1.42; 95% CI, 1.09 to 1.84). The risk was highest in homozygous carriers of PlA2 (53.1% restenosis rate). After adjustment for several clinical and angiographic characteristics, the presence of the PlA2 allele remained a significantly independent risk factor for restenosis (adjusted OR, 1.35; 95% CI, 1.07 to 1.70). The influence of the PlA2 allele on restenosis was stronger in women. Women with PlA2 had a restenosis rate of 52% compared with the 33% incidence among women homozygous for PlA1 (OR, 2.21; 95% CI, 1.27 to 3.85).

CONCLUSIONS

This study showed a significant association between the PlA polymorphism of glycoprotein IIIa and the risk of restenosis after coronary stent placement. The risk was more pronounced in patients homozygous for PlA2 allele and in female patients.

Pathology of acute and chronic coronary stenting in humans

BACKGROUND

Despite the increasing use of stents, few reports have described human coronary artery morphology early and late after stenting.

METHODS AND RESULTS

Histology was performed on 55 stents in 35 coronary vessels (32 native arteries and 3 vein grafts) from 32 patients. The mean duration of stent placement was 39+/-82 days. Fibrin, platelets, and neutrophils were associated with stent struts </=11 days after deployment. In stents implanted for </=3 days, only 3% of struts in contact with fibrous plaque had >20 associated inflammatory cells compared with 44% of struts embedded in a lipid core and 36% of struts in contact with damaged media (P<0.001). Neointimal growth determined late histological success, and increased neointimal growth correlated with increased stent size relative to the proximal reference lumen area. Neointimal thickness was greater for struts associated with medial damage than struts in contact with plaque (P<0.0001) or intact media (P<0.0001). When matched for time since treatment, neointimal cell density in stented arteries was similar to that in unstented arteries that had undergone balloon angioplasty and showed similar proteoglycan deposition.

CONCLUSIONS

Morphology after coronary stenting demonstrates early thrombus formation and acute inflammation followed by neointimal growth. Medial injury and lipid core penetration by struts result in increased inflammation. Neointima increases as the ratio of stent area to reference lumen area increases. Deployment strategies that reduce medial damage and avoid stent oversizing may lower the frequency of in-stent restenosis.

Restenosis rate after intravascular ultrasound-guided coronary stent implantation

This study was designed to test the hypothesis that patients fulfilling intravascular ultrasound (IVUS) criteria for optimal coronary stent implantation show a reduction in the restenosis rate at 6 months. IVUS guidance for stent dilation may be associated with facilitated stent implantation and an increased acute luminal gain, but it has not yet been determined, whether and to what extent this procedure is associated with a reduction in the restenosis rate. IVUS-guided optimization of Palmaz-Schatz stent placement was performed in 125 consecutive patients, 64 of whom fulfilled IVUS-criteria for optimal stent placement. Another 125 patients served as the non-IVUS control group. In 107 patients (86%) of the non-IVUS control group and 105 patients (84%) of the IVUS group, angiographic follow-up was performed. The IVUS group of patients revealed a significantly lower restenosis rate of 20.9% as compared with 29.9% in the control group (P = 0.033). Patients that met IVUS criteria for optimal stent placement had a larger minimal lumen diameter immediately after stent implantation (3.13 +/- 0.44 vs. 2.95 +/- 0.47 mm; P = 0.045) and at 6-month follow-up (2.23 +/- 0.78 vs. 1.87 +/- 0.76 mm; P = 0.019) as well as a significantly lower restenosis rate (13.5% vs. 28.3%; P = 0.038) as compared with patients that did not fulfil these criteria. Our data suggest that patients fulfilling IVUS criteria for optimal stent placement demonstrate a reduced risk for the development of restenosis. Thus, IVUS investigation identifies factors predictive of restenosis after coronary stent placement.

Immediate and long-term outcomes of rotational atherectomy versus balloon angioplasty alone for treatment of diffuse in-stent restenosis

This study was performed to compare the effects of rotational atherectomy (RA) plus balloon angioplasty (BA) with those of BA alone for treatment of diffuse in-stent restenosis. RA+BA or BA alone was performed in a consecutive, prospective (not randomized) manner in 81 patients with 81 diffuse in-stent restenotic lesions (lesion length > 10 mm): 36 patients underwent RA+BA, and 45 patients BA. Clinical recurrence was the primary end point of this study, and was defined as angina associated with objective evidence of myocardial ischemia on stress testing. Mean follow-up duration was 277 +/- 109 days. In the BA group, acute lumen gain after repeat intervention was significantly lower than that of the original stenting procedure (1.94 +/- 0.63 vs 2.37 +/- 0.51 mm, p <0.05). In the RA + BA group, however, acute lumen gain of repeat intervention was similar to that of the original stenting procedure (2.16 +/- 0.52 vs 2.26 +/- 0.66 mm). Clinical recurrence rate at 6 months follow-up was significantly lower in the RA+BA group than in the BA group (25% vs 47%, p <0.05). Clinical events (death, myocardial infarction, repeat intervention) occurred in 6.7% (3 of 45) of patients in the BA group, but in no patient in the RA+BA group during the follow-up period. The long-term angina-free survival rate was significantly higher in the RA+BA group than in the BA group (72% vs 49%, p = 0.02). In conclusion, RA+BA seems to be a more effective therapeutic modality than BA alone for treatment of diffuse in-stent restenosis.

Advantage of stents in the most proximal left anterior descending coronary artery

OBJECTIVES

Balloon angioplasty of the proximal left anterior descending artery is associated with a high rate of restenosis. We hypothesized that the significant reduction in restenosis rates demonstrated by stent implantation in the coronary arteries in general would be especially prominent in the most proximal left anterior descending coronary artery.

METHODS

We reviewed 65 consecutive patients in whom stents were placed in the most proximal left anterior descending artery between March 1990 and July 1995 and compared them with 56 consecutive patients with angioplasty. Minimum luminal diameter was measured angiographically before, after, and 6 months after the intervention. We compared the change in minimum luminal diameter and restenosis rate between the patients with stents and the patients with angioplasty to clarify the response of this important artery to these different procedures.

RESULTS

There was 6-month angiographic follow-up of the treated lesion in 99% of the patients. The postprocedure minimum luminal diameter, acute gain, and minimum luminal diameter at follow-up were greater in arteries treated with stents than in those treated with balloons. Of importance, late loss was not significantly different between the two groups after treatment at this site. Thus the restenosis rate after angioplasty was 52% compared with 20% after stent implantation (p < 0.001).

CONCLUSIONS

Stent implantation in the most proximal left anterior descending artery is associated with an even greater reduction in restenosis rate than implantations elsewhere in the coronary arteries. This enhanced reduction in restenosis appears to be due to an unusually large amount of late loss after angioplasty at this site.

Percutaneous transluminal coronary angioplasty (PTCA) without on-site surgical facilities

BACKGROUND

Numerous publications from European and Canadian centres have documented the feasibility of performing percutaneous transluminal coronary angioplasty (PTCA) without on-site surgical facilities. The absolute need for surgical standby has been changing especially with the introduction of coronary stent for bailout situations. This practice may be applicable in Australian centres especially in the environment of long waiting lists and cost containment.

AIM

To review the safety of performing PTCA by experienced operators in two Melbourne hospitals without on-site surgical facilities.

METHODS

We reviewed data of all patients who had PTCA electively (with low and moderate risks) between July 1996 and January 1997 and in the setting of acute myocardial infarction (AMI) from January 1996 to January 1997. Surgical standby was available as 'next available room' basis in nearby centres. Immediate outcome before discharge was documented and follow up from three to six months in 80% of all surviving patients.

RESULTS

There were 46 elective PTCA and 41 PTCA for AMI. PTCA was successful in 82 (94%) patients. Among the elective cases, seven patients were already inpatients with unstable or postinfarct angina. Thirteen patients had stents deployed with three for acute closure. Abciximab (Reopro) was given to eight patients. Two patients had acute closure in the laboratory which could not be reopened, but did not require emergency coronary artery bypass grafting (CABG). There were four inhospital deaths (three related to AMI and one died of a noncoronary cause).

CONCLUSION

PTCA can be performed electively in a selected group of patients with coronary artery disease and as a primary procedure for AMI without on-site surgical standby.

Six-month angiographic outcome after successful repeat percutaneous intervention for in-stent restenosis

BACKGROUND

In-stent restenosis is an increasing clinical problem. Discordant results have been published regarding the risk of recurrent restenosis after repeat angioplasty for the treatment of in-stent restenosis.

METHODS AND RESULTS

One hundred three consecutive patients (107 vessels) underwent repeat percutaneous intervention for the treatment of in-stent restenosis and were entered in a prospective angiographic follow-up program. Repeat balloon angioplasty was performed at 93 lesions (87%) and additional stenting at 14 lesions (13%). The primary success rate was 98%. Six-month angiographic follow-up was performed in 85% of eligible patients. Restenosis was determined by quantitative angiography. Restenosis defined as a >50% diameter stenosis at follow-up was observed at 22% of lesions. The rate of target-lesion revascularization at 6 months was 17%. Repeat intervention for diffuse in-stent restenosis and severe stenosis before repeat intervention were associated with significantly higher rates of recurrent restenosis.

CONCLUSIONS

The overall restenosis rate after repeat intervention for in-stent restenosis is low. The subgroup of patients with diffuse and/or severe in-stent restenosis, however, is at higher risk of recurrent restenosis and may benefit from alternative therapeutic strategies.

Preliminary experience with the NIR coronary stent

We prospectively studied 223 patients (288 lesions) who underwent elective or bail out implantation of 309 NIR stents (Scimed, Boston Scientific Corporation, Galway, Ireland). Most lesions (68.4%) had unfavorable characteristics (type B2 or C). Primary success in stent deployment was achieved in 305 (98.6%). There was no Q-wave myocardial infarction. Emergency coronary artery bypass grafting (CABG) was required in 1 patient and 1 death occurred. Subacute thrombosis rate was 0.4%. Reference diameter was 2.65+/-0.67 mm. Minimum luminal diameter (MLD) increased from 0.62+/-0.45 to 2.69+/-0.57 mm and diameter stenosis decreased from 78.3+/-13.4% to 12.7+/-5.9%. Clinical follow-up was performed in the first 135 patients for 5.3+/-1.6 months and repeat angiography was undertaken in 35 (16%) with recurrence of symptoms at 4.6+/-1.3 months. Clinical restenosis rate was 9.6%. We conclude that the NIR coronary stent exhibits favorable performance characteristics and appears to be safe and efficacious in the treatment of coronary lesions even in the presence of high-risk characteristics.

Intravascular ultrasound predictors of angiographic restenosis in lesions treated with Palmaz-Schatz stents

OBJECTIVES

This study sought to evaluate the clinical, procedural, preinterventional and postinterventional quantitative coronary angiographic (QCA) and intravascular ultrasound (IVUS) predictors of restenosis after Palmaz-Schatz stent placement.

BACKGROUND

Although Palmaz-Schatz stent placement reduces restenosis compared with balloon angioplasty, in-stent restenosis remains a major clinical problem.

METHODS

QCA and IVUS studies were performed before and after intervention (after stent placement and high pressure adjunct balloon angioplasty) in 382 lesions in 291 patients treated with 476 Palmaz-Schatz stents for whom follow-up QCA data were available 5.5 +/- 4.8 months (mean +/- SD) later. Univariate and multivariate predictors of QCA restenosis (> or = 50% diameter stenosis at follow-up, follow-up percent diameter stenosis [DS] and follow-up minimal lumen diameter [MLD]) were determined.

RESULTS

Three variables were the most consistent predictors of the follow-up angiographic findings: ostial lesion location, IVUS preinterventional lesion site plaque burden (plaque/total arterial area) and IVUS assessment of final lumen dimensions (whether final lumen area or final MLD). All three variables predicted both the primary (binary restenosis) and secondary (follow-up MLD and follow-up DS) end points. In addition, a number of variables predicted one or more but not all the end points: 1) restenosis (IVUS preinterventional lumen and arterial area); 2) follow-up DS (QCA lesion length); and 3) follow-up MLD (QCA lesion length and preinterventional MLD and DS and IVUS preinterventional lumen and arterial area).

CONCLUSIONS

Ostial lesion location and IVUS preinterventional plaque burden and postinterventional lumen dimensions were the most consistent predictors of angiographic in-stent restenosis.

[Rotational atherectomy: technique, indications, results]

Rotational atherectomy (Rotablation) represents one of the alternative devices to treat complex coronary artery stenoses. Rather than increasing luminal diameter by arterial stretching and plaque fracture as with balloon angioplasty, rotablation debulks atherosclerotic plaque with an abrasive diamond coated burr. The basic physical principle is differential cutting. It allows the advancing burr to selectively cut inelastic material while elastic tissue deflects away from the burr. 95% of the particles generated by the Rotablator are less than 5 microns. They are removed by the body's reticuloendothelial system. There are different strategies to perform a rotablation, regarding the number of burrs used and the final burr-to-artery ratio. An adjunctive PTCA is recommended without proof by randomized studies so far. The best indication for the Rotablator is the undilatable lesion. Lesion modification (debulking) as a method of improving vessel compliance seems to be also usefull in diffusely diseased and calcified vessels, as well as in aorto-ostial and angulated stenoses. The instent restenoses is a new indication. Randomized studies will have to proof if there is an advantage for rotablation compared to PTCA. Restenosis rates appear comparable to balloon angioplasty.

Acute and long-term outcome after Palmaz-Schatz stenting: analysis from the New Approaches to Coronary Intervention (NACI) registry

The randomized Stent Restenosis Study (STRESS) and Belgium Netherlands Stent (Benestent) trials established that elective use of Palmaz-Schatz stents (PSSs) in native coronary arteries with de novo lesions is associated with increased procedural success and reduced restenosis. However there are other clinical indications for which stents are commonly used (unplanned use, vein grafts, restenosis lesions) that are not addressed in these studies. From 1990-1992, 688 lesions in 628 patients were treated with PSSs in the New Approaches to Coronary Intervention (NACI) registry. Angiographic core laboratory readings were available for 543 patients (595 lesions, of which 106 were stented for unplanned indications, 239 were in saphenous vein bypass grafts, and 296 were previously treated). The cohort of patients in whom stents were placed for unplanned indications had more women, current smokers, and had a higher incidence of recent myocardial infarction (MI). Patients who underwent stenting of saphenous vein grafts were older, had a higher incidence of diabetes mellitus, unstable angina, prior MI, and congestive heart failure. Lesion success was similar in all cohorts (98%), but procedural success was significantly higher for planned stenting (96% vs 87%; p < 0.01). Predictors of adverse events in-hospital were presence of a significant left main stenosis and stenting for unplanned indication. The incidence of target lesion revascularization by 30 days was significantly higher for patients undergoing unplanned stenting due to a higher risk for stent thrombosis. Recent MI, stenting in native lesion, and small postprocedural minimum lumen diameter independently predicted target lesion revascularization at 30 days. Independent predictors of death, Q-wave myocardial infarction, or target lesion revascularization at 1 year included severe concomitant disease, high risk for surgery, left main disease, stenting in the left main coronary artery, and low postprocedure minimum lumen diameter.

Predictive factors of restenosis after coronary stent placement

OBJECTIVES

The objective of this study was to identify clinical, lesional and procedural factors that can predict restenosis after coronary stent placement.

BACKGROUND

Coronary stent placement reduces the restenosis rate compared with that after percutaneous transluminal coronary angioplasty (PTCA). However, restenosis remains an unresolved issue, and identification of its predictive factors may allow further insight into the underlying process.

METHODS

All patients with successful coronary stent placement were eligible for this study unless they had had a major adverse cardiac event during the 1st 30 days after the procedure. Of the 1,349 eligible patients (1,753 lesions), follow-up angiography at 6 months was performed in 80.4% (1,084 patients, 1,399 lesions). Demographic, clinical, lesional and procedural data were prospectively recorded and analyzed for any predictive power for the occurrence of late restenosis after stenting. Restenosis was evaluated by using three outcomes at follow-up: binary restenosis as a diameter stenosis > or =50%, late lumen loss as lumen diameter reduction and target lesion revascularization (TLR) as any repeat PTCA or coronary artery bypass surgery involving the stented lesion.

RESULTS

Multivariate analysis demonstrated that diabetes mellitus, placement of multiple stents and minimal lumen diameter (MLD) immediately after stenting were the strongest predictors of restenosis. Diabetes increased the risk of binary restenosis with an odds ratio (OR) [95% confidence interval] of 1.86 [1.56 to 2.16] and the risk of TLR with an OR of 1.45 [1.11 to 1.80]. Multiple stents increased the risk of binary restenosis with an OR of 1.81 [1.55 to 2.06] and that of TLR with an OR of 1.94 [1.66 to 2.22]. An MLD <3 mm at the end of the procedure augmented the risk of binary restenosis with an OR of 1.81 [1.55 to 2.06] and that of TLR with an OR of 2.05 [1.77 to 2.34]. Classification and regression tree analysis demonstrated that the incidence of restenosis may be as low as 16% for a lesion without any of these risk factors and as high as 59% for a lesion with a combination of these risk factors.

CONCLUSIONS

Diabetes, multiple stents and smaller final MLD are strong predictors of restenosis after coronary stent placement. Achieving an optimal result with a minimal number of stents during the procedure may significantly reduce this risk even in patients with adverse clinical characteristics such as diabetes.

Comparison of angiography and intravascular ultrasound for the assessment of lumen size after coronary stent placement: impact of dilation pressures

This study was designed to assess the extent of potential discrepancies between intravascular ultrasound (IVUS) and quantitative coronary angiography (QCA) measurement of intrastent minimal luminal diameter and to evaluate the impact of dilation pressures and the balloon:artery ratio on the assessment of the minimal lumen diameter (MLD) by these imaging modalities. IVUS is recommended as an adjunct to angiography to assess stent expansion; however, the extent of potential discrepancies between the two imaging modalities is not well defined. Included were 225 patients in whom coronary Palmaz-Schatz stents were successfully placed after PTCA. IVUS and QCA were performed at the end of the intervention. We compared the MLD assessed by QCA and IVUS in the instent and reference site. The MLD assessed by IVUS and QCA were 2.68 +/- 0.41 mm and 3.08 +/- 0.47 mm (P < 0.001), respectively, at the tightest intrastent site and 3.19 +/- 0.50 mm and 3.17 +/- 0.52 ns at the reference site. There was a correlation between the dilation pressure and the difference between QCA- and IVUS-based intrastent MLD measurement (y = -0.05x + 1.11; r = -0.53; P < 0.0001). At low dilation pressures, a significant difference between the image modalities was found, but after high dilation pressures no discrepancies were detected. No relation was found with the balloon:artery ratio. These data provide clear evidence that in the case of low-pressure dilation, the exclusive reliance on data obtained by QCA will not yield sufficiently accurate information on intrastent MLD, whereas after high dilation pressure, the differences between the imaging modalities are minimized.

Clinical outcome of patients undergoing endoluminal coronary artery reconstruction with three or more stents

OBJECTIVES

We sought to evaluate the outcome of patients undergoing multiple (three or more), contiguous stent implantation within a single native coronary artery.

BACKGROUND

The implantation of multiple stents within a single coronary artery is increasing in frequency, although the outcome of such patients is not well described.

METHODS

Forty-five patients without previous coronary artery bypass graft surgery (CABG) undergoing multiple, contiguous stent implantation in a single coronary artery were identified. Clinical and angiographic characteristics and outcomes were analyzed.

RESULTS

The angiographic success rate was 97.8%. The procedural success rate was 91.1%; stent occlusion during the initial hospital period occurred in four patients (8.9%). Death, myocardial infarction (MI), CABG, repeat target vessel intervention or severe angina occurred in 10 (23.3%) of 43 hospital survivors at 6-months follow-up. The indication for stent placement was threatened or abrupt closure in 30 patients (66.7%). Of the 25 patients with abrupt or threatened closure whose clinical and angiographic data would have indicated emergent CABG had stents not been available, the frequency of in-hospital death and Q wave MI was similar to that of a matched consecutive series of patients at our institution who underwent emergent CABG after failed angioplasty. At 1 year, the frequency of death, Q wave MI, CABG and severe angina at 1 year was similar in the two groups; the need for repeat percutaneous intervention was more common in the stent group (25% vs. 0%, p = 0.01).

CONCLUSIONS

Implantation of multiple, contiguous intracoronary stents was associated with a high initial success rate, although the incidence of early stent closure was relatively high. Adverse events at 6 months of follow-up were more frequent than previously reported for elective single-stent implantation; however, adverse angiographic characteristics such as dissection and thrombus were frequent in this group. In addition, the strategy of multiple stent implantation in the setting of failed angioplasty is a reasonable alternative to emergent CABG, although the need for further percutaneous intervention must be anticipated.

Abrupt vessel closure: changing importance, management, and consequences

Percutaneous coronary interventions have been performed for 20 years. Despite the success and progress of these interventions, abrupt vessel closure has been a dramatic adverse event of coronary interventions. Closure has frequently led to the major complications of death, myocardial infarction, and emergency coronary artery bypass. Because of the fear of this adverse event and its subsequent complications, the applicability of coronary interventions is sometimes limited. The pathologic characteristics of abrupt vessel closure have been recognized as predominantly caused by dissection, with vessel recoil and thrombus formation playing important secondary roles. The recognition of the lesions at risk for abrupt vessel closure has led to a strategy of lesion-specific device therapy to reduce complications. Similarly the role of antiplatelet and antithrombotic therapies have reduced complications. The earliest methods of dealing with abrupt closure was emergency coronary artery bypass surgery with significant rates of morbidity and mortality. With the advent of second-generation devices and techniques, particularly stents, the management of abrupt vessel closure has been simplified and alternatives to emergency coronary bypass are more available. This article will review the history and current status of the prevention and management of abrupt vessel closure and demonstrate that anticipation and management of this complication have been facilitated with reduction of subsequent complications and increased applicability of coronary interventions.

Long-term clinical follow-up after successful repeat percutaneous intervention for stent restenosis

OBJECTIVES

This study evaluated the long-term clinical outcome of successful repeat percutaneous intervention after in-stent restenosis.

BACKGROUND

Recurrence of symptoms and angiographic restenosis after stent implantation are observed in 15% to 35% of cases. Repeat percutaneous treatment for in-stent restenosis has been shown to be safe, with high immediate success, but little is known about the long-term clinical outcome.

METHODS

Clinical follow-up (minimum 9 months) was obtained in a consecutive series of 124 patients (127 vessels) presenting with stent restenosis who were successfully treated with repeat percutaneous intervention.

RESULTS

Clinical follow-up was obtained in all 124 patients at a mean [+/-SD] of 27.4 +/- 14.7 months (range 9 to 66); a stress test was available in 88 patients (71%). Recurrence of clinical events occurred in 25 patients (20%) and included death from any cause in 2 patients (2%), target vessel revascularization in 14 (11%), myocardial infarction in 1 (1%) and positive stress test results or recurrence of symptoms (Canadian Cardiovascular Society class I to IV) treated medically in 8 (6%). Cumulative event-free survival at 12 and 24 months was 86.2% and 80.7%, respectively. Significant predictive factors of recurrence of clinical events were repeat intervention in saphenous vein grafts, multivessel disease, low ejection fraction and a < or = 3-month interval between stent implantation and repeat intervention.

CONCLUSIONS

In-stent balloon angioplasty for stent restenosis in native vessels seems to be an effective method in terms of a low long-term clinical event rate.

Early and late assessment of the Micro Stent PL coronary stent for restenosis and suboptimal balloon angioplasty

This prospective study represents the initial assessment of the Micro Stent PL (Arterial Vascular Engineering, Inc.) coronary stent. From one to three radiopaque stainless steel stents, each measuring 4 mm long, were premounted onto specially designed balloon catheters. A total of 123 stents were implanted in 41 patients without procedural failure or complications. Stent dislodgment proved a concern, with 7 of 123 stents (5.7%) moving > 3 mm from the site of placement and late downstream migration occurring in an additional patient. Subacute stent thrombosis occurred in two patients (5%). Six-month angiographic follow-up was available in 37 of 41 patients (90%). Minimal lumen diameter at baseline was 0.93 +/- 0.51 mm, increasing to 2.74 +/- 0.49 mm after stenting, and falling to 1.66 +/- 0.89 mm at 6 months; this represents a late loss of 60% of the initial gain. Restenosis, based on a binary definition of > 50% diameter stenosis, was documented in 18 patients (49%). Advantages of the Micro Stent PL include its radiopacity and marked ease of distal delivery. The potential for stent dislodgment has implications for future stent designs. The role of the Micro Stent PL in managing restenosis is unclear, but it appears useful in the management of dissection and threatened closure after balloon angioplasty.

Endovascular stents: a 'break through technology', future challenges

Coronary stents were developed to overcome the two main limitations of balloon angioplasty, acute occlusion and long term restenosis. Coronary stents can tack back intimal flaps and seal the dissected vessel wall and thereby treat acute or threatened vessel closure after unsuccessful balloon angioplasty. Following successful balloon angioplasty stents can prevent late vessel remodeling (chronic vessel recoil) by mechanically enforcing the vessel wall and resetting the vessel size resulting in a low incidence of restenosis. All currently available stents are composed of metal and the long-term effects of their implantation in the coronary arteries are still not clear. Because of the metallic surface they are also thrombogenic, therefore rigorous antiplatelet or anticoagulant therapy is theoretically required. Furthermore, they have an imperfect compromise between scaffolding properties and flexibility, resulting in an unfavourable interaction between stents and unstable or thrombus laded plaque. Finally, they still induce substantial intimal hyperplasia which may result in restenosis. Future stent can be made less thrombogenic by modifying the metallic surface, or coating it with an antithrombotic agent or a membrane eluting an antithrombotic drug. The unfavourable interaction with the unstable plaque and the thrombus burden can be overcome by covering the stent with a biological conduit such as a vein, or a biodegradable material which can be endogenous such as fibrin or exogenous such as a polymer. Finally the problem of persisting induction of intimal hyperplasia may be overcome with the use of either a radioactive stent or a stent eluting an antiproliferative drug.

Intravascular ultrasound-guided emergency coronary Palmaz-Schatz stent placement without post-procedural systemic anticoagulation

OBJECTIVE

To test the efficacy of intravascular ultrasound (IVUS)-guided stent placement and to determine the clinical outcome during the first 30 days in those patients who were treated with antiplatelet therapy rather than anticoagulants because they met the IVUS criteria for optimal stent placement.

DESIGN

Prospective observational study.

PATIENTS

126 patients with successful, non-elective Palmaz-Schatz stent placement.

INTERVENTIONS

IVUS was performed to assess the attachment of stent struts, the coverage of the dissection, and the intrastent minimal lumen area.

MAIN OUTCOME MEASURES

Intrastent lumen area, clinical outcome during the first 30 days.

RESULTS

In all patients IVUS showed complete apposition and coverage of the dissection. In 23 patients (18%) the IVUS lumen area criterion was achieved. In 75 patients, further balloon dilatation was performed and in 41 IVUS criteria were finally fulfilled. The minimal intrastent lumen area increased from a mean (SD) of 6.81 (1.15) mm2 to 9.56 (2.61) mm2 (P < or = 0.01) between the first and final IVUS investigations. 64 patients (51%) who met the IVUS criteria were treated with aspirin (100 mg) and ticlopidine (250 mg) twice a day. During the first 30 days none of the following events occurred: death, myocardial infarction, repeat intervention, aortocoronary bypass surgery, and subacute stent thrombosis.

CONCLUSION

The additional information provided by IVUS examination helped the operator to decide whether further dilatation was needed after a coronary stent had been placed. For patients who met the IVUS criteria for optimal stent placement, antiplatelet therapy was associated with an excellent clinical outcome during the first 30 days.

New stent technologies

Coronary stents were developed to overcome the two main limitations of balloon angioplasty, acute occlusion and long-term restenosis. Coronary stents can tack back intimal flaps and seal the dissected vessel wall, thereby treating acute or threatened vessel closure after unsuccessful balloon angioplasty. After successful balloon angioplasty, stents can prevent late vessel remodeling (chronic vessel recoil) by mechanically enforcing the vessel wall and resetting the vessel size, resulting in a low incidence of restenosis. All currently available stents are composed of metal, and the long-term effects of their implantation in the coronary arteries are still not clear. Because of the metallic surface, they are also thrombogenic; therefore, rigorous antiplatelet or anticoagulant therapy is theoretically required. Furthermore, they have an imperfect compromise between scaffolding properties and flexibility, resulting in an unfavorable interaction between stents and unstable or thrombus-laden plaque. Finally, they still induce substantial intimal hyperplasia that may result in restenosis. Future stents can be made less thrombogenic by modifying the metallic surface or coating it with an antithrombotic agent or a membrane eluting an antithrombotic drug. The unfavorable interaction with the unstable plaque and the thrombus burden can be overcome by covering the stent with a biological conduit, such as a vein, or a biodegradable material that can be endogenous, such as fibrin, or exogenous, such as a polymer. Finally, the problem of persisting induction of intimal hyperplasia may be overcome with the use of either a radioactive stent or a stent eluting an antiproliferative drug.

Contemporary stent designs: technical considerations, complications, role of intravascular ultrasound, and anticoagulation therapy

A number of studies have shown the benefits of stent placement over balloon angioplasty for the treatment of focal, native coronary artery, and saphenous vein graft disease. Although the number of stent designs available for clinical use has increased dramatically, the late clinical benefit of stenting over balloon angioplasty has yet to be shown in diffuse disease, complex bifurcation stenoses, or smaller (2.5-mm) vessels, each of which may require unique stent designs and adjunct therapies not currently available or extensively studied. The purposes of this review are to discuss the various stent designs currently available for clinical use, outline the known complications associated with these stents, assess the contribution of intravascular ultrasound, and describe current antiplatelet and antithrombotic therapy used after stent use.

Platelet activation and coronary stent implantation. Effect of antithrombotic therapy

BACKGROUND

Platelet activation and surface expression of adhesive glycoproteins play a key role in ischemic thrombotic complications after coronary intervention. The purpose of this case-control study was to evaluate the effects of two different antithrombotic regimens on platelet function after coronary Palmaz-Schatz stent implantation.

METHODS AND RESULTS

The study group consisted of 46 "low-risk" patients who were treated with ticlopidine (250 mg BID) and aspirin (100 mg BID) after stenting. The control group was derived from a cohort of 151 patients receiving conventional anticoagulation therapy, including phenprocoumon (target international normalized ratio, 3.5), heparin (activated partial thromboplastin time, 80 to 120 seconds), and aspirin (100 mg BID) after stenting. Criteria for matching were indication for stenting, target vessel, balloon size, inflation pressure, and number of inserted stents. Matches were obtained for 38 patients. Platelet function was evaluated before and daily for 12 days after stenting in venous blood samples with immunologic activation markers. Patients receiving anticoagulation therapy showed a significantly increased surface exposure of LIBS1 (activated fibrinogen receptor; P < .05) and CD62P (P-selectin; P < .001) above prestent values, peaking days 3 to 6 after stenting. In contrast, in patients receiving ticlopidine, expression of LIBS1 decreased (P < .01) and expression of CD62P remained basically unchanged after stenting. Platelet count significantly decreased after stenting in patients treated by anticoagulation (day 3; P < .01), whereas no significant changes were found in the ticlopidine group.

CONCLUSIONS

Significant platelet activation occurs in patients receiving anticoagulation therapy after stenting, while platelet deactivation is found in patients treated with combined antiplatelet therapy. This may contribute to a lowering of the incidence of subacute stent thrombosis.