Arterial remodeling influences the development of intimal hyperplasia after stent implantation

Highly flexible and porous silk fibroin microneedle wraps for perivascular drug delivery

Various perivascular drug delivery techniques have been demonstrated for localized post-treatment of intimal hyperplasia: a vascular inflammatory response caused by endothelial damages. Although most perivascular devices have focused on controlling the delivery duration of anti-proliferation drug, the confined and unidirectional delivery of the drug to the target tissue has become increasingly important. In addition, careful attention should also be paid to the luminal stability and the adequate exchange of vascular protein or cell between the blood vessel and extravascular tissue to avoid any side effect from the long-term application of any perivascular device. Here, a highly flexible and porous silk fibroin microneedle wrap (Silk MN wrap) is proposed to directly inject antiproliferative drug to the anastomosis sites while ensuring sufficient vascular exchanges. Drug-embedded silk MNs were transfer-molded on a highly flexible and porous silk wrap. The enhanced cell compatibility, molecular permeability, and flexibility of silk MN wrap guaranteed the structural integrity of blood vessels. Silk wrap successfully supported the silk MNs and induced multiple MN penetration to the target tissue. Over 28 days, silk MN wrap significantly inhibited intimal hyperplasia with a 62.1% reduction in neointimal formation.

Epigenetic Regulation of Vascular Smooth Muscle Cell Phenotype Switching in Atherosclerotic Artery Remodeling: A Mini-Review

Atherosclerosis is a chronic inflammatory disease characterized by extensive remodeling of medium and large-sized arteries. Inward remodeling (=lumen shrinkage) of the vascular walls is the underlying cause for ischemia in target organs. Therefore, inward remodeling can be considered the predominant feature of atherosclerotic pathology. Outward remodeling (=lumen enlargement) is a physiological response compensating for lumen shrinkage caused by neointimal hyperplasia, but as a pathological response to changes in blood flow, outward remodeling leads to substantial arterial wall thinning. Thinned vascular walls are prone to rupture, and subsequent thrombus formation accounts for the majority of acute cardiovascular events. Pathological remodeling is driven by inflammatory cells which induce vascular smooth muscle cells to switch from quiescent to a proliferative and migratory phenotype. After decades of intensive research, the molecular mechanisms of arterial remodeling are starting to unfold. In this mini-review, we summarize the current knowledge of the epigenetic and transcriptional regulation of vascular smooth muscle cell phenotype switching from the contractile to the synthetic phenotype involved in arterial remodeling and discuss potential therapeutic options.

Culprit lesion remodelling and long-term prognosis in patients with acute coronary syndrome: an intravascular ultrasound study

AIMS

Positive arterial remodelling is recognized as one of the morphological characteristics of the vulnerable plaque. Limited data are available on a long-term outcome of acute coronary syndrome (ACS) patients with culprit lesion positive arterial remodelling (PR). The aim of this study was to investigate the long-term impact of culprit lesion PR in patients with ACS.

METHODS AND RESULTS

In 134 patients with ACS, intravascular ultrasound (IVUS) was performed to assess target lesion remodelling before percutaneous coronary intervention. PR was defined as the ratio of the external elastic membrane cross-sectional area at the target lesion to that of at the proximal reference of >1.05, and intermediate or negative remodelling (IR/NR) was defined as that of ≤1.05. Major adverse cardiac event (MACE) was defined as a composite of death, ACS, and target lesion revascularization. During the follow-up (median 5.8 years), MACE-free survival was significantly lower in the PR group than that in the IR/NR group (log-rank, P = 0.005). Survival and ACS-free survival were also significantly lower in the PR group than that in the IR/NR group (log-rank, both P = 0.04). By multivariable Cox regression analysis, PR (hazard ratio = 2.4, P = 0.02) and diabetes (hazard ratio = 1.9, P = 0.03) were independent predictors of MACE.

CONCLUSION

Culprit lesion PR was associated with a poor long-term prognosis in patients with ACS. PR may be a marker of vulnerable patients.

Predictors of in-stent stenosis and occlusion after endovascular treatment of intracranial vascular disease with the Willis covered stent

Covered stent placement has emerged as a promising therapeutic option for intracranial vascular lesions. However, in-stent stenosis and occlusion continue to be important concerns with the use of a covered stent, which is more thrombogenic than other types of stents. The purpose of this study was to determine predictors of in-stent stenosis and occlusion for covered stents used in the treatment of intracranial vascular diseases. Clinical, procedural and angiographic data of 46 patients with 49 intracranial vascular lesions treated with the Willis covered stent (Micro-Port, Shanghai, China) between April 2005 and October 2010 were collected and analyzed retrospectively. Univariate analysis and multivariate logistic regression analysis were performed to determine the factors predictive of in-stent stenosis and/or occlusion of the stents. In-stent stenosis and/or occlusion were documented at angiography in six patients with six lesions, and no stenoses or occlusions were seen at angiography in the remaining 40 patients with 43 lesions. Univariate analysis revealed that hypertension, post-procedure irregular antiplatelet therapy and cerebrovascular arteriosclerosis were associated with in-stent stenosis and/or occlusion. By multivariate logistic regression analysis, post-procedure irregular antiplatelet therapy (odds ratio [OR]=15; 95% confidence interval [CI], 1.172-192.004; p=0.037) and cerebrovascular arteriosclerosis (OR=19; 95% CI, 1.374-262.659; p=0.028) were independent predictors of in-stent stenosis and/or occlusion. Thus, post-procedure irregular antiplatelet therapy and coexistent cerebrovascular arteriosclerosis appear to increase the risk of in-stent stenosis and/or occlusion of covered stents in the treatment of intracranial vascular disease.

Long-term effectiveness and safety of sirolimus drug-eluting stents

The root cause of coronary artery disease is atherosclerosis, ie, intraluminal narrowing (stenosis) of the arteries that supply blood to tissues of the heart. The introduction of the drug-eluting stent over the past decade has revolutionized the field of interventional cardiology. It is used extensively in clinical practice for the treatment of coronary artery disease. The first drug-eluting stent to receive US Food and Drug Administration approval was the sirolimus-eluting stent. Recently, two other stent analogs of sirolimus were approved, ie, the zotarolimus-eluting stent and the everolimus-eluting stent. However, concern has arisen in recent years about the long-term safety and efficacy of drug-eluting stents, due to the occurrence of late adverse clinical events, such as stent thrombosis. This review focuses on clinical studies that have been performed with the sirolimus-eluting stent or its analogs. We discuss the pharmacology, safety, and various therapeutic options that exist when choosing stents for coronary artery disease. Our aim is to provide a thorough review of the long-term efficacy and safety of sirolimus drug-eluting stents, and also to discuss currently approved and promising investigational drug-eluting stents, in an effort to provide insight into how these stents are currently evolving and generate further investigation in this area.

Carotid and femoral atherosclerotic plaques show different morphology

OBJECTIVE

Results of endovascular repair vary according to the arterial bed. We hypothesized that these differences may be related to the plaque features. To explore this hypothesis, we designed a prospective study that compared carotid and femoral atheroma.

METHODS AND RESULTS

Patients that underwent femoral or carotid endarterectomy were included in our study. Demographic data and blood sampling were obtained prior to surgery. Plaques were evaluated for AHA grading, calcification and lipid content. Eighty-eight plaques were harvested during this study (45 carotid specimens and 43 femoral specimens). No differences were noted between carotid and femoral groups regarding demographic and biological data. Histological data more frequently showed fibrous cap atheroma in carotid arteries (75%) and fibrocalcific plaques in femoral arteries (93%), p<0.001. Morphological analyses showed a high prevalence of osteoid metaplasia in femoral arteries (63%) compared to carotid arteries (20%, p<0.001). Biochemical analyses were consistent with histological data, showing higher calcium and lesser cholesterol concentrations in femoral than in carotid plaques (p<0.01).

CONCLUSIONS

Femoral and carotid plaques showed different morphology in comparable groups of patients.

Relationship Between Arterial and Fibrous Cap Remodeling

Background—

Positive arterial remodeling and thin fibrous cap are characteristics of rupture-prone or vulnerable plaque. The natural course of the fibrous cap thickness and the relationship between serial arterial remodeling and changes in fibrous cap thickness are unknown. Therefore, the purpose of this study was to evaluate the relationship between changes in fibrous cap thickness and arterial remodeling by using optical coherence tomography (OCT) and intravascular ultrasound (IVUS) during 6-month follow-up.

Methods and Results—

Both IVUS and OCT examinations were performed on 108 vessels from 36 patients with ischemic heart disease who underwent percutaneous coronary intervention. Fifty-eight fibroatheromas were selected from 82 nonsignificant, nonculprit lesions (angiographic diameter stenosis, 25% to 75%; plaque burden, >40% by IVUS). Fibroatheroma was defined by OCT as lipid-rich plaque in >1 quadrant that has lipid. Thickness of the fibrous cap was measured by OCT. IVUS and OCT examinations were repeated at 6-month follow-up. Serial changes and relationships between IVUS indices and fibrous cap thickness were investigated. Overall, fibrous cap thickness (98.1±38.9 to 96.9±44.5 μm) as well as IVUS indices did not change significantly within 6 months. The percent changes in fibrous cap thickness correlated negatively and significantly ( r =−0.54; P <0.0001; generalized estimating equation adjusted, r =−0.42; P =0.001) with the percent changes in external elastic membrane cross-sectional area.

Conclusions—

Arterial remodeling is related to changes in fibrous cap thickness. Positive arterial remodeling is not only an adaptive process, but also related to thinning of the fibrous cap.

Effect of culprit-lesion remodeling versus plaque rupture on three-year outcome in patients with acute coronary syndrome

To investigate intravascular ultrasound predictors of long-term clinical outcome in patients with acute coronary syndrome, 94 patients with a first acute coronary syndrome with both preintervention intravascular ultrasound imaging and long-term follow-up were enrolled in this study. Remodeling index was defined as external elastic membrane cross-sectional area at the target lesion divided by that at the proximal reference. Arterial remodeling was defined as either positive (PR: remodeling index >1.05) or intermediate/negative remodeling (remodeling index < or =1.05). Clinical events were death, myocardial infarction, and target-lesion revascularization. Patients were followed up for a mean of 3 years. PR was observed in 50 (53%), and intermediate/negative remodeling, in 44 (47%). During the 3-year follow-up, there were 20 target-lesion revascularization events and 5 deaths (2 cardiac and 3 noncardiac), but no myocardial infarctions. Patients with PR showed significantly lower major adverse cardiac event (MACE; death, myocardial infarction, and target-lesion revascularization)-free survival (log-rank p = 0.03). However, patients with plaque rupture showed a nonsignificant trend toward lower MACE-free survival (p = 0.13), but there were no significant differences in MACE-free survival between those with single versus multiple plaque ruptures. Using multivariate logistic regression analysis, only culprit lesion PR was an independent predictor of MACEs (p = 0.04). In conclusion, culprit-lesion remodeling rather than the presence or absence of culprit-lesion plaque rupture was a strong predictor of long-term (3-year) clinical outcome in patients with acute coronary syndrome.

Positive remodeling is associated with more plaque vulnerability and higher frequency of plaque prolapse accompanied with post-procedural cardiac enzyme elevation compared with intermediate/negative remodeling in patients with acute myocardial infarction

BACKGROUND

We assessed the impact of remodeling patterns on pre- and post-procedural intravascular ultrasound (IVUS) findings and cardiac enzyme elevation after stenting in 310 acute myocardial infarction (AMI) patients.

METHODS

The positive remodeling (PR) (PR group, n=113) was defined as remodeling index (lesion/reference external elastic membrane cross-sectional area) >1.05, intermediate remodeling (IR) as between 0.95 and 1.05, and negative remodeling (NR) as<0.95 (IR/NR group, n=197). IVUS findings included ruptured plaque (a cavity that communicated with the lumen with an overlying residual fibrous cap fragment), multiple ruptured plaques (different plaque ruptures separated by a >5-mm length of artery containing smooth lumen contours), thrombus (discrete intraluminal filling defects), and plaque prolapse (tissue extrusion through the stent strut at post-stenting). We compared pre- and post-procedural IVUS findings and cardiac-specific troponin I (cTnI) elevation after stenting according to the remodeling pattern.

RESULTS

The plaque rupture (60% vs. 42%, p=0.004), multiple plaque ruptures (22% vs. 14%, p=0.014), and IVUS-detected thrombus (42% vs. 28%, p=0.012) were more common in the PR group compared with the IR/NR group. Post-stenting plaque prolapse was observed more frequently (36% vs. 22%, p=0.008), and cTnI was elevated more significantly after stenting in the PR group compared with the IR/NR group (DeltacTnI; +7.8+/-51.1 ng/ml vs. +0.9+/-41.1 ng/ml, p=0.008). Multivariate analysis showed that PR [odds ratio (OR)=1.92; 95% CI 1.04-2.98, p=0.028], plaque rupture (OR 1.98; 95% CI 1.16-3.45, p=0.025), IVUS-detected thrombus (OR 2.30; 95% CI 1.22-3.98, p=0.008), and plaque prolapse (OR 8.40; 95% CI 4.19-16.84, p<0.001) were independently associated with post-stenting cTnI elevation.

CONCLUSIONS

AMI patients with PR have more plaque vulnerability and higher frequency of plaque prolapse accompanied by post-procedural cardiac enzyme elevation compared with AMI patients with IR/NR.

Effect of preinterventional arterial remodeling on intimal hyperplasia after implantation of a polymer-based paclitaxel-eluting stent: angiographic and IVUS study

BACKGROUND

The aim of this study was to evaluate the effect of preinterventional arterial remodeling on in-stent intimal hyperplasia (IH) after the implantation of a polymer-based paclitaxel-eluting stent.

METHODS

The study population consisted of 55 patients (61 lesions) with a de novo lesion treated with a paclitaxel-eluting stent. The lesions were divided into two groups, positive or intermediate (PR/IR), and negative remodeling (NR) groups, according to the preinterventional arterial remodeling. Angiographic and IVUS examinations were performed preintervention, postintervention and at 9 months of follow-up.

RESULTS

The remodeling index (RI) was 1.19+/-0.16 in the PR/IR group and 0.81+/-0.10 in the NR group. At follow-up, the late loss was significantly larger in the PR/IR group than in the IR group. (0.65+/-0.58 mm vs. 0.29+/-0.5 mm, p=0.017). The external elastic membrane cross-sectional area (CSA) (18.68+/-5.39 vs. 12.87+/-3.72 mm(2), p=0.000), plaque CSA (16.99+/-4.04 vs. 10.34+/-3.45 Mm(2), p=0.000) and plaque index (85.84+/-5.02 vs. 81.80+/-7.26%, p=0.048) during the preintervention period and IH volume during the follow-up were significantly larger in the PR/IR group than in the NR group (17.98+/-16.7 mm(3) vs. 4.59+/-12.4 mm(3); p<0.001). Further, the percentage of the change in the IH was also larger in the PR/IR group than in the NR group (13.49+/-11.78% vs. 4.12+/-10.76%; p=0.002). A significant positive correlation was found between the preinterventional RI and follow-up IH CSA (r=0.406, p=0.001).

CONCLUSIONS

The preinterventional arterial remodeling influenced the development of the IH after the implantation of the polymer-based paclitaxel-eluting stent which had a greater effect on reducing the IH accumulation in the lesions with preinterventional negative remodeling characteristics.

Intravascular ultrasonic analysis of atherosclerotic vessel remodeling and plaque distribution of stenotic left anterior descending coronary arterial bifurcation lesions upstream and downstream of the side branch

Bifurcation lesions remain a challenging lesion subset, even in the era of drug-eluting stents. The aim of this study was to investigate the longitudinal remodeling pattern and cross-sectional plaque location of bifurcation lesions. Seventy-four preintervention intravascular ultrasound studies of left anterior descending bifurcation lesions were analyzed, in which the lesion was located proximal (type A, n=32) or distal (type B, n=42) to the side branch. Vessel area and plaque area at the lesion (VAlesion and PAlesion) and at the reference site (VAreference and PAreference) were measured. The remodeling ratio was defined as VAlesion/VAreference, and the vessel compensation ratio was defined as (VAlesion-VAreference)/(PAlesion-PAreference). The geometric center of the lumen at the lesion site was identified, and the lesion site was divided into circumferential equal arcs to compare the cross-sectional distribution of percentage plaque area (100x[PAlesion/VAlesion]) between the 2 groups. The remodeling ratio (1.03+/-0.15 vs 0.94+/-0.14, p=0.01) and the vessel compensation ratio (0.0+/-0.36 vs -0.37+/-0.61, p<0.01) were significantly greater in type A than in type B lesions. The circumferential distribution pattern of percentage plaque area was significantly different between the groups (analysis of variance p<0.005), with greater percentage plaque area for the vessel wall opposite from the side branch in type B lesions (46.3+/-18.0% vs 54.6+/-15.4%, type A vs type B lesions, p<0.05). In conclusion, these results suggest that a major side branch may affect longitudinal lesion remodeling as well as the circumferential location of atherosclerotic plaque.

Remodeling Index Compared to Actual Vascular Remodeling in Atherosclerotic Left Main Coronary Arteries as Assessed With Long-Term (≥12 Months) Serial Intravascular Ultrasound

OBJECTIVES

We present the remodeling index (RI) versus serial intravascular ultrasound (IVUS) data.

BACKGROUND

The RI, derived by comparing lesion external elastic membrane (EEM) cross-sectional area versus the reference at one time point, is used in various IVUS studies as a substitute of true remodeling (change in EEM over time), assuming that it represents true remodeling.

METHODS

We studied 46 non-stenotic left main arteries using serial IVUS (follow-up 18 +/- 8 months). Plaques were divided into subgroups according to the follow-up RI: follow-up RI >1 (n = 27) versus follow-up RI < or =1 (n = 19).

RESULTS

Lesions with a follow-up RI >1 had an increase in lumen despite an increase in plaque because of an increase in EEM. Conversely, lesions with a follow-up RI < or =1 had a reduction in lumen as a result of both a plaque increase and EEM decrease. Overall, the follow-up RI correlated directly with changes in lesion site EEM (baseline-to-follow-up). Although there was no correlation between the follow-up RI and changes in reference EEM area, changes in reference EEM area did correlate directly with changes in lesion EEM area. In nearly 90% of lesions with a follow-up RI >1, there was a previously documented increase in EEM area. Using multivariate linear regression analysis, the follow-up RI was dependent on the baseline RI, the increase in lesion EEM area, and the decrease in reference EEM area. The follow-up RI was not dependent on changes in lesion plaque area.

CONCLUSIONS

The vast majority of left main lesions with a remodeling index >1 had evidence of a previous increase in lesion-site EEM area.

Impact of intravascular ultrasound lesion characteristics on neointimal hyperplasia following sirolimus-eluting stent implantation

The effect of lesion characteristics on neointimal hyperplasia after sirolimus-eluting stent implantation was examined in 45 patients who underwent successful preinterventional intravascular ultrasound. There were no differences in neointimal hyperplasia between the moderate/severe calcified lesion group (calcium arc >120 degrees ) and the non/mild calcified lesion group or between the positive vessel remodeling group (external elastic membrane area at the minimal lumen area site larger than that at the proximal reference site) and negative vessel remodeling group. No correlation between preinterventional plaque burden and neointimal hyperplasia was found. In patients who have coronary artery disease, sirolimus-eluting stents continue to demonstrate striking suppression of neointimal proliferation, irrespective of lesion characteristics previously associated with greater restenotic risk.

Cumulative incidence of coronary lesions with vulnerable characteristics in patients with stable angina pectoris: an intravascular ultrasound and angiographic study

BACKGROUND

Development of vulnerable lesion may take place simultaneously at many sites of coronary vasculature, therefore causing multisite instability. The prevalence of the phenomenon in stable angina (SA) patients remains unknown. The aim of our study was to assess, in patients with stable angina, the prevalence of coronary plaques with vulnerable characteristics and to ascertain whether the number of such lesions may accumulate.

METHODS

Vulnerable plaques are characterised by positive remodelling on intravascular ultrasound (IVUS) and with complex appearance on angiography. We performed preprocedural IVUS in target lesion of 67 patients with SA (46 males, age 55.9). Remodelling index (RI) defined as vessel area at the target lesion divided by that of average reference segments > or = 1.05 was assumed as positive remodelling. Plaques of > or = 30% stenosis on angiography were classified into complex or smooth groups.

RESULTS

Positive remodelling was found in 30 (44.8%) and complex plaque in 16 (23.9%) of 67 target lesions. Multiple complex plaques were present in 21 (31.3%) patients. Plaques with positive remodelling more often were complex on angiography (12/30 vs. 4/37, respectively; p=0.005) and were more often associated by complex plaques at other sites (35/30 vs. 23/37; p=0.04) than the remaining lesions. Moreover, the presence of positive remodelling predicted multiple complex lesions at other sites (OR 5.6; 95% CI 1.7-18.3).

CONCLUSION

Multiple coronary plaques with vulnerable characteristics are present in nearly one third of patients with stable angina. Incidence of vulnerable lesions may have cumulative character, i.e. the presence of one vulnerable lesion predicts occurrence of further vulnerable plaques.

Impact of Preinterventional Arterial Remodeling on In-Stent Neointimal Hyperplasia and In-Stent Restenosis After Coronary Stent Implantation-An Intravascular Ultrasound Study-

BACKGROUND

Patterns of arterial remodeling during the course of plaque development have been shown to play an important role in both the progression of de novo atherosclerosis and in the restenotic process following coronary intervention. The aim of the present prospective study was to evaluate the effect of pre-interventional arterial remodeling on in-stent neointimal hyperplasia (NIH) and in-stent restenosis (ISR) after stenting.

METHODS AND RESULTS

Pre-interventional arterial remodeling was assessed in 85 native coronary lesions by using intravascular ultrasound (IVUS). The remodeling index (RI) was 1.09+/-0.20 in the positive remodeling (PR)/intermediate remodeling (IR) group and 0.84+/-0.12 in the negative remodeling (NR) group. The plaque plus media cross sectional area (P&M CSA) at pre-intervention and NIH CSA at follow-up in the minimal lumen CSA were significantly larger in the PR/IR group (9.2+/-2.9 mm2 vs 6.2+/-1.8 mm2, 3.3+/-1.2 mm2 vs 1.5+/-0.9 mm2; p = 0.001, p = 0.001, respectively). On 3-dimensional analysis of IVUS images at follow-up, the lumen volume was significantly smaller in the PR/IR group than that in the NR group (62+/-15 mm3 vs 75 +/-20 mm3; p = 0.001), and neointima hyperplasia volume was significantly larger in the PR/IR group than that in the NR group (46+/-15 mm3 vs 26+/-10 mm3; p = 0.001). A significant positive correlation was found between pre-interventional RI and follow-up NIH CSA (r = 0.25, p = 0.022). The incidence of ISR and repeat intervention was significantly higher in the PR/IR group (30.8% vs 18.2%, 28.8% vs 15.2%; p = 0.032, 0.035, respectively).

CONCLUSION

Measuring pre-interventional arterial remodeling patterns by IVUS may be helpful to stratify lesions at high-risk of ISR.

Impact of peri-stent remodeling on in-stent neointimal proliferation in acute myocardial infarction

Fifty stented lesions in 50 patients with acute myocardial infarction were studied by intravascular ultrasound (IVUS) before and just after stent implantation and at follow-up. Volumetric IVUS analyses revealed that greater peristent positive remodeling after stent implantation was associated with less neointimal proliferation and greater luminal gain at follow-up.

Effect of preintervention remodeling type on subsequent coronary artery behavior after directional atherectomy

To evaluate the influence of preintervention remodeling on subsequent vessel behavior after directional coronary atherectomy (DCA) under intravascular ultrasound (IVUS) guidance, serial (before and after DCA and at 6-month follow-up) IVUS data were analyzed for 246 lesions that were classified into 2 categories: positive remodeling (PR) in 77 lesions versus intermediate or negative remodeling in 169 lesions. Although the 2 groups had similar baseline characteristics, IVUS data showed that the PR group had a greater acute lumen area (LA) gain without an increased late LA loss, resulting in a greater net (acute plus late) LA gain and follow-up LA. This suggests that IVUS-guided DCA may neutralize the negative impact of preintervention PR on late vessel patency.

Arterial remodeling patterns before intervention predict diffuse in-stent restenosis

OBJECTIVES

The aim of this retrospective study was to determine the predictors of diffuse in-stent restenosis (ISR) among the lesions causing the first ISR by intravascular ultrasound (IVUS) studies.

BACKGROUND

Although some predictors of diffuse ISR have been reported, parameters on IVUS relating to diffuse ISR are not well characterized.

METHODS

We classified 52 ISR lesions that had undergone successful stent implantation and led to restenosis into two types--focal and diffuse ISR--using quantitative coronary angiography. Restenosis was defined as > or =50% diameter stenosis, and diffuse ISR as lesion length > or =10 mm at follow-up. The remodeling index (RI) was defined as the vessel area at the target lesion divided by that of averaged reference segments.

RESULTS

There were no significant differences in patient, angiographic, and procedural characteristics between the focal (n = 25) and diffuse (n = 27) ISR groups. Baseline RI was significantly greater in the diffuse ISR group (1.03 +/- 0.18 vs. 0.88 +/- 0.24, p = 0.0159). Negative remodeling, defined as RI <0.9, was detected in 60% of the focal ISR group and in only 26% of the diffuse ISR group. By logistic regression analysis, baseline RI was the only independent predictor of diffuse ISR (p = 0.0341). Moreover, volumetric analyses revealed that lesions developing into diffuse ISR had less capacity to compensate for further plaque growth.

CONCLUSIONS

Among the first ISR lesions, baseline positive remodeling was the most powerful predictor of diffuse ISR. Measuring pre-interventional arterial remodeling patterns by IVUS may be helpful to stratify lesions at higher risk.

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

BACKGROUND

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

METHODS AND RESULTS

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

CONCLUSIONS

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

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

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

Relationship between residual atheroma burden and neointimal growth in patients undergoing stenting: analysis of the atherectomy before MULTI-LINK improves lumen gain and clinical outcomes trial intravascular ultrasound substudy

OBJECTIVES

The objective of this study was to examine the relationship between quantitative volumetric and cross-sectional measures of residual atheroma burden and neointimal growth after coronary stenting.

BACKGROUND

Previous intravascular ultrasound (IVUS) studies have demonstrated a correlation between residual atheroma burden and neointimal growth after coronary stenting. However, postmortem studies contradict this finding.

METHODS

The study population included 34 patients who underwent IVUS six to eight months after stent placement, including 26 patients who underwent IVUS immediately after stent placement and at six to eight months follow-up. Using manual planimetry, the lumen cross-sectional area (LA), stent cross-sectional area (SA) and external elastic membrane cross-sectional area (EEM) were measured at 1-mm intervals after the procedure and at follow-up. Percent neointimal area (NA) and atheroma area (AA) were calculated as: percent neointimal area = ([SA - LA]/SA) x 100; percent AA = ([EEM - SA]/EEM) x 100 in the entire cross section and in individual quadrants. Postinterventional atheroma volume and neointimal volume at follow-up were calculated using Simpsons's rule.

RESULTS

In pooled analyses using all cross sections and cross-sectional quadrants, there was a weak correlation between percent AA and NA (r = 0.11 and 0.12, respectively). Analysis in individual patients demonstrated no significant relationship between total or quadrant measurements of percent AA and NA (p = 0.47 and 0.4, respectively). No relationship between atheroma volume postintervention and neointimal volume at follow-up was observed (r = 0.1, p = 0.62).

CONCLUSIONS

This study failed to demonstrate a clinically significant relationship between quantitative volumetric and cross-sectional measures of residual atheroma burden and subsequent neointimal growth.

Can we prevent in-stent restenosis?

Nowadays stent placement has replaced balloon angioplasty as the most commonly performed percutaneous coronary interventional procedure, mainly because of its better acute and chronic outcome. As a result, in-stent restenosis (ISR) has become a widespread problem. The incidence of ISR varies from 10% to 50% and depends on the absence or presence of several risk factors, such as small vessel size, longer lesions, and diabetes. Intravascular ultrasound studies have demonstrated that ISR is mainly caused by neointimal proliferation; consequently, this pathologic process has become the target of many preventive and therapeutic approaches. This article provides an overview of such management strategies, highlighting the rather disappointing experiences with mechanical and systemic drug therapies; the relative merits and disadvantages of intracoronary radiation; and the exciting yet realistic promise, embodied by the recent advancements in drug-eluting stent technology, of potentially eradicating ISR in the near future.

Effective plaque removal with a new 8 French-compatible atherectomy catheter

The purpose of this study was to evaluate the safety and efficacy of the new 8 Fr guide catheter-compatible Flexicut directional atherectomy device and to compare it with the conventional Atherocath GTO catheter. The 6 Fr Flexicut catheter has a larger cutting window and a titanium nitride-coated cutter to effect more tissue removal as well as treat mildly calcified lesions. A group of 143 lesions in 117 consecutive patients treated with the Flexicut catheter in four centers were compared with a control group of 277 lesions in 212 consecutive patients treated with the GTO device. Postatherectomy luminal diameters were larger (2.92 +/- 0.79 vs. 2.52 +/- 0.64 mm; P < 0.0001), with more luminal gain (relative gain: 0.58 +/- 0.24 vs. 0.48 +/- 0.25; P = 0.0007) using fewer directional coronary atherectomy (DCA) cuts (12 +/- 7 vs. 16 +/- 9; P = 0.0001) in the Flexicut group. A residual diameter stenosis < 20% immediately after DCA was obtained in 77% of the lesions in the Flexicut group vs. 45% in the GTO group (P < 0.0001). Histology in the former group revealed large calcium speckles in the retrieved specimens. In the Flexicut group, there was a lower incidence of access site complications and damage to the coronary ostium (2.5% vs. 7.5%; P = 0.08). The new Flexicut catheter is more effective than the conventional GTO catheter with a trend for reduced guiding catheter-related complications.

Mechanisms of acute gain and late lumen loss after atherectomy in different preintervention arterial remodeling patterns

The main mechanism of restenosis after directional coronary atherectomy (DCA) remains obscure. We investigated mechanisms of restenosis after DCA in different coronary artery remodeling patterns. DCA was performed in 51 de novo lesions. The lesions were evaluated by intravascular ultrasound (IVUS) before, immediately after, and 6 months after the procedure. According to the IVUS findings before DCA, we classified the lesions into the following 3 groups: (1) positive (n = 10), (2) intermediate (n = 25), and (3) negative (n = 16) remodeling. We measured lumen area, vessel area, and plaque area using IVUS before DCA, immediately after DCA, and at follow-up. Lumen area increase after DCA was mainly due to plaque area reduction in the positive and intermediate remodeling groups (90 plus minus 15% and 80 plus minus 25% increase in lumen area, respectively), whereas that in the negative remodeling group was due to both plaque area reduction (57 plus minus 22% increase in lumen area) and vessel area enlargement (43 plus minus 33% increase in lumen area). The plaque area increase correlated strongly with late lumen area loss in the positive and intermediate remodeling groups (r = 0.884, p <0.001; r = 0.626, p <0.001, respectively), but the decrease in vessel area was not correlated with lumen area loss. In contrast, both an increase in plaque area and a decrease in vessel area were correlated with late lumen area loss (r = 0.632, p = 0.009; r = 0.515, p = 0.041) in the negative remodeling group. Coronary artery restenosis after atherectomy was primarily due to an increase in plaque in the positive and/or intermediate remodeling groups. However, in the negative remodeling group, late lumen loss might have been caused by both an increase in plaque and vessel shrinkage.

What has intravascular ultrasound taught us about plaque biology?

Intravascular ultrasound (IVUS) has a defined role in the cardiac catheterization laboratory to assess lesion severity and the procedural success of vascular interventions. However, IVUS has also contributed to our understanding of the biology of atherosclerosis and restenosis. In acute coronary syndromes, IVUS has revealed varying degrees of stenosis, thrombosis, and plaque derangement typical of the plaque disruption seen in many pathologic studies of patients who have died of this condition. IVUS has demonstrated that the culprit lesions of patients surviving acute coronary syndromes also tend to be softer, with less calcium, and tend to have more plaque with positive arterial remodeling (compensatory enlargement) than lesions causing stable coronary syndromes. Arterial remodeling is also an important component of restenosis after coronary interventions. IVUS has suggested that interventions that reduce restenosis tend to have a greater impact on preventing negative remodeling (constriction) rather than reducing neointimal proliferation. Oxidant stress may be an important contributor to negative remodeling, as IVUS has demonstrated this anatomy at sites of coronary artery spasm. Positive remodeling seen by IVUS is also associated with impaired endothelial vasomotor dysfunction, and IVUS studies have demonstrated the contribution of vasomotor tone to arterial elasticity. Future directions include integrating IVUS with other imaging modalities, such as angiography, to study the interaction of anatomic and physiologic factors in atherosclerosis progression, and using the raw ultrasound signal to distinguish plaque components and differences in wall strain that may identify vulnerable plaques.