Yutaka Hikichi

Mobilization of CD34-Positive Bone Marrow–Derived Cells After Coronary Stent Implantation Impact on Restenosis

Background— Recently, accumulating evidence has indicated that bone marrow–derived stem cells are capable of differentiating into vascular cells. It has been hypothesized that the inflammatory response after vascular injury triggers the mobilization of endothelial and smooth muscle progenitor cells from bone marrow. Methods and Results— We measured circulating CD34-positive mononuclear cells, activation of integrin Mac-1 on the surface of neutrophils, and plasma granulocyte-colony stimulating factor levels in 40 patients undergoing coronary stenting. After bare-metal stenting, CD34-positive cells increased, reaching a maximum on day 7 after stenting. The maximum change compared with baseline before stenting was more striking in patients with restenosis than without restenosis (332±108% versus 148±49%; P<0.05). In contrast, CD34-positive cells decreased after sirolimus-eluting stenting (72±21% on day 7). The change in CD34-positive cells on day 7 relative to baseline was closely correlated with that in activated Mac-1 at 48 hours (R=0.52, P<0.01) and that in granulocyte-colony stimulating factor levels at 24 hours (R=0.42, P<0.05). Cell culture assay on day 7 showed that mononuclear cells differentiated into CD31-positive endothelium-like cells after bare-metal stenting. In patients with restenosis, mononuclear cells differentiating into α-smooth muscle actin–positive smooth muscle–like cells also were observed. Implantation of sirolimus-eluting stents suppressed both types of differentiation. Conclusions— Stent implantation may induce differentiation of bone marrow cells into endothelial or smooth muscle cells. Endothelial cells may participate in reendothelialization, a protective reaction against vascular injury, whereas smooth muscle cells may participate in neointimal thickening and restenosis. Sirolimus-eluting stents appear to inhibit the mobilization and differentiation of bone marrow cells.

Involvement of C-reactive protein obtained by directional coronary atherectomy in plaque instability and developing restenosis in patients with stable or unstable angina pectoris

We investigated whether positive immunohistochemical staining of C-reactive protein (CRP) in initial culprit lesions is related to coronary plaque instability and whether it could affect the outcome of directional coronary atherectomy (DCA). The plasma level of CRP is a reliable marker of the risk of coronary events and restenosis after percutaneous coronary intervention. However, the influence of tissue CRP in atheromatous plaque on plaque vulnerability and restenosis remains unknown. Samples of DCA obtained from 12 patients with stable angina pectoris and 15 patients with unstable angina pectoris were immunohistochemically stained with a monoclonal antibody against CRP. We performed follow-up coronary angiography on 22 of 27 patients to evaluate the presence of restenosis after DCA. Immunoreactivity to CRP was localized to macrophages, smooth muscle cells, and necrotic areas. The ratio of CRP positive cells to total cells was significantly higher in DCA samples from patients with unstable (17.9 +/- 2.0%) than with stable angina (11.0 +/- 2.5%) (p <0.05). Follow-up coronary angiography showed that 12 of 22 patients developed restenosis after DCA. The ratio was also significantly higher in DCA specimens from patients with restenosis (19.3 +/- 2.8%) compared with those without restenosis (11.0 +/- 2.0%) (p <0.05). In addition, the ratio significantly correlated with late luminal loss (r = 0.428, p <0.05) and loss index (r = 0.636, p = 0.0011) after DCA. Immunoreactivity to CRP in coronary atheromatous plaque increases in culprit lesions of unstable angina, and it affects restenosis after DCA. These findings suggest that CRP in atheromatous plaque plays an important role in the pathogenesis of unstable angina and restenosis after coronary intervention.

Efficacy of cilostazol after endovascular therapy for femoropopliteal artery disease in patients with intermittent claudication.

OBJECTIVES The purpose of this study was to investigate whether cilostazol reduces restenosis and revascularization after endovascular therapy (EVT) for femoropopliteal lesions. BACKGROUND Cilostazol improves walking distance in patients with intermittent claudication and reduces restenosis after coronary intervention, but its efficacy remains unclear after EVT for femoropopliteal disease. METHODS This study was performed as a multicenter, randomized, open-label clinical trial. Eighty patients (mean age 70.7 +/- 6.2 years, 84% men) with intermittent claudication due to a femoropopliteal lesion were randomly assigned to receive or not receive cilostazol in addition to aspirin. The primary end point was freedom from target vessel revascularization, and the secondary end points were the rate of restenosis and freedom from target lesion revascularization and major adverse cardiovascular events, defined as all-cause death, myocardial infarction, stroke, repeat revascularization, and leg amputation. RESULTS Clinical follow-up information was obtained in all patients. Patient, lesion, and procedural characteristics did not differ significantly between the 2 groups. Stenting was performed in 36 patients (cilostazol, 16; control, 20; p = 0.36). Freedom from target vessel revascularization at 2 years after EVT was significantly higher compared with the control group (84.6% vs. 62.2%, p = 0.04). The rate of restenosis was lower in the cilostazol group (43.6% vs. 70.3%, p = 0.02), and freedom from target lesion revascularization and major adverse cardiovascular events was higher in the cilostazol group (87.2% vs. 67.6%, p = 0.046, 76.8% vs. 45.6%, p = 0.006, respectively). There was no major bleeding in either group during follow-up period. CONCLUSIONS Cilostazol reduced restenosis and repeat revascularization after EVT in patients with intermittent claudication due to femoropopliteal disease.

Examination of Stent Deformation and Gap Formation after Complex Stenting of Left Main Coronary Artery Bifurcations Using Microfocus Computed Tomography

BACKGROUND Fluoroscopy and intravascular ultrasound (IVUS) lack sufficient resolution for assessing the results of complex stenting in true bifurcation lesions. OBJECTIVES After diverse bifurcation stenting at the left main coronary artery (LM) bifurcation model, the results were examined using microfocus computed tomography (MFCT). METHODS The strut distribution of three kinds of stents deployed on a straight vessel segment was investigated. Classical crush, double kissing (DK)-double crush, and culotte stenting were performed on a three-dimensional (3D) LM model. The results were assessed using cross-sectional, longitudinal, and 3D reconstruction views of MFCT. RESULTS Nonuniform strut distribution was observed in a corrugated stent design deployed on a straight vessel segment. Following classical crush stenting, a relatively large gap at the nonmyocardial site was observed in the corrugated stents. When the guidewire recrossed outside the ostium of the crushed side branch stent, kissing balloon inflation caused further crushing of the stent at the more distal segment. The dilated strut rose up from the main vessel bed after the first kissing balloon inflation in DK crush stenting; the advantage of DK would be cancelled after main vessel stenting due to recrushing the raised strut. The culotte stenting with closed-cell stents showed the restriction of the expansion at the branch ostium when it was dilated with a 3.5-mm balloon. The culotte stenting with open-cell-based stents showed a good stent apposition except for a tiny gap and small metallic carina at the distal bifurcation. CONCLUSION MFCT analysis in the 3D phantom model is useful to assess the structural deformation of the stents and gap on vessel wall coverage after complex stenting at the LM bifurcation.

Stent-induced neutrophil activation is associated with an oxidative burst in the inflammatory process, leading to neointimal thickening.

Activation of leukocytes plays an essential role in the mechanism of restenosis. Prior research has focused on monocytes and little is known about the role of neutrophils in this process. Neutrophils are known to contribute to tissue injury through oxygen-derived free radicals that nitrate tyrosine. This study was designed to elucidate clinically the role of neutrophil-mediated oxidative burst in the regulation of the post-stent inflammatory process. In 36 patients undergoing coronary stenting, we serially measured serum levels of glycosyl-phosphatidil-inositol-anchored protein (GPI)-80,a modulator of Mac-1 on the surface of neutrophils, in samples of coronary sinus as well as peripheral blood. We also simultaneously measured the serum 3-nitrotyrosine/tyrosine ratio as an index of oxidative stress. The GPI-80 level and the 3-nitrotyrosine/tyrosine ratio increased in the coronary sinus after coronary stenting in a time-dependent manner; with the maximum increase of GPI-80 level (3.1 +/- 2.9 to 8.6 +/- 4.3 ng/ml, P < 0.01) at 48 hours, and 3-nitrotyrosine/tyrosine ratio at 24 hrs (5.2 +/- 4.8 to 28.4 +/- 13.2 x 10(-4), P < 0.01), more strikingly than in the peripheral blood. In the coronary sinus blood, the 3-nitrotyrosine/tyrosine ratio was correlated with GPI-80 levels at 24 hr (R = 0.58, P < 0.001) and at 48 hr (R = 0.41, P < 0.01). Multiple regressions analysis showed that the maximum responses of GPI-80 level and 3-nitrotyrosine/tyrosine ratio were independent predictors of angiographic late lumen loss. Our results may support a hypothesis that Mac-1-dependent activation of neutrophils causes oxidative burst in the post-stent inflammatory process, possibly leading to restenosis.

Biomechanical Modeling to Improve Coronary Artery Bifurcation Stenting: Expert Review Document on Techniques and Clinical Implementation

Treatment of coronary bifurcation lesions remains an ongoing challenge for interventional cardiologists. Stenting of coronary bifurcations carries higher risk for in-stent restenosis, stent thrombosis, and recurrent clinical events. This review summarizes the current evidence regarding application and use of biomechanical modeling in the study of stent properties, local flow dynamics, and outcomes after percutaneous coronary interventions in bifurcation lesions. Biomechanical modeling of bifurcation stenting involves computational simulations and in vitro bench testing using subject-specific arterial geometries obtained from in vivo imaging. Biomechanical modeling has the potential to optimize stenting strategies and stent design, thereby reducing adverse outcomes. Large-scale clinical studies are needed to establish the translation of pre-clinical findings to the clinical arena.

Coronary bifurcation stenting: insights from in-vitro and virtual bench testing

The various techniques and devices that have been proposed for the treatment of coronary bifurcation lesions have differing levels of complexity and each has one or more limitations. Two highly complementary ex vivo methods are available to study the treatment of bifurcation lesions: in vitro and virtual bench testing. Both methods can be used to develop, evaluate and optimise bifurcation stenting techniques and dedicated devices. The basics, the evolution, the advantages and limitations of both methods are discussed in this paper. Subsequently, a literature overview of the main insights gained from ex vivo testing in the field of bifurcation stenting is given.

Benefits and Limitations of Cypher Stent-Based Bifurcation Approaches: In Vitro Evaluation Using Micro-Focus CT Scan

Intervention for bifurcated lesions is a complex procedure. It could involve a simple main vessel stenting to a comprehensive double stenting of the main vessel and side branch. The clinical outcomes of these different strategies were evidenced by recent results of many randomized trials. However, the mechanisms of technical success or failure from these stenting strategies were not investigated. In this bench study, in vitro silicone bifurcated vessel models were constructed. Stenting from various technical strategies was studied in detail by micro-focus computer tomography.

Optimal kissing balloon inflation after single-stent deployment in a coronary bifurcation model

AIMS To define the optimal kissing balloon inflation (KBI) after single-stent deployment in a coronary bifurcation model. METHODS AND RESULTS We deployed stents in main vessels (MV) followed by KBI in various conditions and compared the stent configurations. A) KBI at the operators discretion vs. under the guidelines of minimal balloon overlapping (MBO). Various stent configurations were observed after the former option, whereas similar maximal dilation points were observed under the MBO guidelines. B) Long balloon overlapping (LBO) vs. MBO with proximal MV dilated by a large balloon. The proximal MV was dilated to an ideal round shape with MBO versus an oval shape with LBO. C) Two-link vs. 3-link stents. Although the 2-link stent was advantageous to open the side branch, it incurred a risk of overdilatation of the proximal struts, whereas the 3-link stent preserved its structure. Computed simulations of coronary flow were analysed in the following left main coronary models: circle with a diameter of 4 and 5.5 mm, ellipse with longitudinal direction and tilt position. They revealed that the overdilated side was exposed to low shear stress regardless of its shape. CONCLUSIONS Optimal KBI can be achieved with MBO and proximal dilatation by an optimally sized balloon.

Comparison of changes in circulating platelet-derived microparticles and platelet surface P-selectin expression after coronary stent implantation

Platelet-derived microparticles (PDMPs) are released from activated platelets and may participate in the inflammatory process in response to vessel wall injury. This study was designed to compare the clinical significance of circulating PDMPs with that of P-selectin on the platelet membrane surface. In 20 patients with stable angina undergoing coronary stent implantation, circulating PDMPs were serially measured by enzyme-linked immunosorbent assay, and P-selectin expression on the surface of platelets was simultaneously analyzed by flow cytometry. PDMPs increased 24–48 h after coronary stenting in the coronary sinus (8.7 ± 8.9 to 31.8 ± 19.8 U/ml, P < 0.001) with a maximum at 48 h. In contrast, the mean channel fluorescence intensity for P-selectin increased 15 min after coronary stenting in the coronary sinus (19.5 ± 5.6 to 25.2 ± 7.5, P < 0.01) and remained elevated for 48 h; the changes were less striking in peripheral blood. The relative increase in PDMPs was not correlated with the increase in P-selectin expression at 15 min or 24 h after coronary stenting, but was correlated at 48 h (R = 0.48, P < 0.05). Both circulating PDMPs and P-selectin expression were enhanced in association with stent-induced platelet activation; however, the time course of changes in these two platelet activation markers was different. Therefore, the clinical relevance of circulating PDMPs may differ from that of P-selectin expression on the platelet membrane surface.