Hirosada Yamamoto

Incidence and clinical impact of coronary stent fracture after sirolimus-eluting stent implantation

Background: Stent fracture is one of the possible causes of restenosis after sirolimus‐eluting stents (SES) implantation. The aim of our study was to evaluate the prevalence and clinical impact of coronary stent fracture after SES implantation. Methods: From our prospective institutional database, 280 patients were treated solely with SES from August 2004 to June 2005. Among the 280 patients, 256 patients with a total of 307 lesions underwent follow‐up angiography on an average of 240 days after the procedure. Results: Stent fractures were observed in eight (2.6%) lesions. Of the eight lesions with stent fracture, five were located in the right coronary artery (RCA), two in the saphenous vein (SV) graft, and one in the left anterior descending coronary artery. The stent fractures were all in the locations that served as hinges during vessel movement in the cardiac contraction cycle. Seven of the eight stent fractures were adjacent to the edge of previously implanted or overlapped stent. Significant multivariate predictors of stent fracture were SV graft location (Odds ratio 35.88; 95% confidence interval 2.73–471.6, P = 0.006), implanted stent length (Odds ratio 1.04; 95% confidence interval 1.01–1.07, P = 0.02), and RCA location (Odds ratio 10.00; 95% confidence interval 1.11–89.67, P = 0.04). In‐stent binary restenosis rate was 37.5% and target lesion repeat revascularization rate was 50.0% in patients with stent fracture. Conclusions: Stent fracture was likely to be affected by mechanical stress provoked by rigid structures and hinge points. Stent fracture might be associated with the high incidence of target lesion revascularization.

Prevalence of Carotid Artery Stenosis in Patients With Coronary Artery Disease in Japanese Population

Background and Purpose— Prevalence of carotid artery stenosis in patients with coronary artery disease (CAD) is unknown in Japanese population. Methods— The study populations consisted of 632 consecutive patients who underwent coronary angiography because of suspicion of CAD. All patients underwent carotid ultrasonography to screen carotid artery stenosis before coronary angiography. We defined echographic carotid stenosis as area stenosis of >50% or peak systolic velocity of >200 cm/s. Results— Echographic carotid stenosis was observed in 124 patients (19.6%). Coronary angiography revealed 433 patients had CAD. Prevalence of echographic carotid artery stenosis was 14 of 199 (7.0%), 18 of 124 (14.5%), 28 of 131 (21.4%), and 64 of 178 (36.0%) in patients with 0-, 1-, 2-, and 3-vessel CAD, respectively (P<0.0001). The prevalence rate with carotid stenosis and CAD was 25.4%. Multivariate stepwise logistic regression analysis showed that age and the extent of CAD were independently related to the presence of carotid stenosis (P=0.0002 and <0.0001, respectively). Conclusions— Prevalence of carotid stenosis in patients with CAD is high in Japan as well as in Western countries. Screening of carotid artery stenosis is recommended especially in older patients with multivessel CAD.

Impact of renal insufficiency on clinical and angiographic outcomes following percutaneous coronary intervention with sirolimus-eluting stents

Background: Sirolimus‐eluting stents (SES) have been demonstrated to reduce restenosis. However, there have been few studies evaluating the impact of renal insufficiency on the angiographic as well as clinical outcomes after SES implantation. Methods: This study was composed of 304 consecutive patients having 361 lesions who underwent percutaneous coronary intervention with SES. The patients were divided into 3 groups according to renal function (group 1 [n = 204]; creatinine clearance (Ccr) ≥≥60ml/min, group 2 [n = 69]; Ccr <60 ml/min, group 3 [n = 31]; hemodialysis). Clinical and angiographic follow‐up were evaluated at 8 months. Results: Clinical follow‐up was obtained in all patients and angiographic follow‐up was obtained in 283 patients (93.1%). Patients in group 3 showed a higher incidence of previous coronary artery bypass graft surgery, and there were more female gender, hypertensive, and less hyperlipidemia in this group. Late lumen loss at 8 months was significantly different among the 3 groups (group 1; 0.16 ± 0.46 mm, group 2; 0.44 ± 0.62 mm, group 3; 0.81 ± 0.88 mm, P < 0.0001). Major adverse cardiac events (MACE) were documented in 22 patients (10.8%) in group 1, 13patients (18.8%) in group 2, and 12 patients (38.7%) in group 3, respectively (P = 0.0002). Conclusion: Neointimal growth following SES implantation is more pronounced in patients with renal insufficiency, especially those undergoing dialysis, compared with patients with normal renal function. Regardless of the beneficial effect of SES, the increased risk of MACE mainly due to high incidence of target vessel revascularization in the subgroup of patients with renal insufficiency should be taken into account.

Volumetric quantification of fibrous caps using intravascular optical coherence tomography

The rupture of thin-cap fibroatheroma accounts for most acute coronary events. Optical Coherence Tomography (OCT) allows quantification of fibrous cap (FC) thickness in vivo. Conventional manual analysis, by visually determining the thinnest part of the FC is subject to inter-observer variability and does not capture the 3-D morphology of the FC. We propose and validate a computer-aided method that allows volumetric analysis of FC. The radial FC boundary is semi-automatically segmented using a dynamic programming algorithm. The thickness at every point of the FC boundary, along with 3-D morphology of the FC, can be quantified. The method was validated against three experienced OCT image analysts in 14 lipid-rich lesions. The proposed method may advance our understanding of the mechanisms behind plaque rupture and improve disease management.

Clinical and Angiographic Outcomes Following Percutaneous Coronary Intervention With Sirolimus-Eluting Stents Versus Bare-Metal Stents in Hemodialysis Patients

BACKGROUND Percutaneous coronary intervention for hemodialysis patients has been hampered by the high rate of adverse cardiac events. Our aim was to investigate whether sirolimus-eluting stents (SESs) improve clinical outcomes of hemodialysis patients compared with bare-metal stents (BMSs). STUDY DESIGN Retrospective study. SETTING & PARTICIPANTS 123 consecutive patients on hemodialysis therapy treated with either an SES or BMS. There were 56 patients with 68 lesions treated with SESs between August 2004 and April 2006 (SES group) and 67 patients with 71 lesions treated with BMSs 4 years before approval of SESs in Japan (BMS group). PREDICTOR SES and BMS implantation for hemodialysis patients with coronary artery disease. OUTCOMES & MEASUREMENTS Follow-up angiography was performed at 6 to 8 months and clinical follow-up was obtained at 9 months after the procedure. Late lumen loss and major adverse cardiac events, including all-cause death, myocardial infarction, and target-lesion revascularization, were investigated. RESULTS Clinical follow-up was obtained in all patients. Angiographic follow-up was obtained in 50 patients (89.3%) in the SES group and 50 patients (74.6%) in the BMS group. The SES group had more complex lesions than the BMS group. Quantitative angiographic analysis showed a significant difference for in-stent late lumen loss (SES, 0.62 +/- 0.75 mm; BMS, 1.07 +/- 0.75 mm; P = 0.003). Of angiographic restenosis lesions analyzed, a focal restenotic pattern was observed more frequently in the SES group than the BMS group (SES, 87.5%; BMS, 23.8%; P < 0.001). The rate of major adverse cardiac events was significantly lower in the SES group (n = 14; 25.0%) than the BMS group (n = 26; 38.9%; log-rank P = 0.02). LIMITATIONS Retrospective study design, small sample size, and a single-center study. CONCLUSIONS Clinical and angiographic data in the present study suggest that SESs are more effective than BMSs in hemodialysis patients.

Difference of culprit plaque composition between patients with and without pre-infarction angina: an intravascular ultrasound radiofrequency analysis.

AIMS This study was performed to assess the differences in culprit plaque composition between patients with and without pre-infarction angina (PA) by using spectral analysis of intravascular ultrasound (IVUS) radiofrequency (RF) data. METHODS AND RESULTS Of 57 patients consecutively admitted to our institution with acute myocardial infarction, pre-intervention IVUS RF data of culprit plaques were obtained and analysed in 35 patients after percutaneous aspiration thrombectomy. Among the 35 patients, 21 patients had PA. Culprit plaques of patients without PA consisted of a higher percentage of the necrotic core component than those with PA (minimum lumen area [MLA]) site, 21.2+/-8.9% versus 9.9+/-9.8%, p=0.0015; entire culprit lesion, 18.9+/-6.3% versus 12.0+/-9.6%, p=0.023). In contrast, culprit plaques of patients with PA contained a higher percentage of the fibrofatty component than those without PA (MLA site, 21.0+/-12.0% versus 11.5+/-7.6%, p=0.013; entire culprit lesion, 16.8+/-7.9% versus 12.1+/-5.5%, p=0.062). There was no significant difference in quantitative parameters between the patients with and without PA. CONCLUSIONS Culprit plaques of patients with PA were different from those without PA. Plaque composition may play an important role in the occurrence of PA.

Three-dimensional registration of intravascular optical coherence tomography and cryo-image volumes for microscopic-resolution validation.

Abstract. Evidence suggests high-resolution, high-contrast, 100  frames/s intravascular optical coherence tomography (IVOCT) can distinguish plaque types, but further validation is needed, especially for automated plaque characterization. We developed experimental and three-dimensional (3-D) registration methods to provide validation of IVOCT pullback volumes using microscopic, color, and fluorescent cryo-image volumes with optional registered cryo-histology. A specialized registration method matched IVOCT pullback images acquired in the catheter reference frame to a true 3-D cryo-image volume. Briefly, an 11-parameter registration model including a polynomial virtual catheter was initialized within the cryo-image volume, and perpendicular images were extracted, mimicking IVOCT image acquisition. Virtual catheter parameters were optimized to maximize cryo and IVOCT lumen overlap. Multiple assessments suggested that the registration error was better than the 200-μm spacing between IVOCT image frames. Tests on a digital synthetic phantom gave a registration error of only +1.3±2.7  μm (signed distance). Visual assessment of randomly presented nearby frames suggested registration accuracy within 1 IVOCT frame interval (−25.0±174.3  μm). This would eliminate potential misinterpretations confronted by the typical histological approaches to validation, with estimated 1-mm errors. The method can be used to create annotated datasets and automated plaque classification methods and can be extended to other intravascular imaging modalities.

Comparison of scanning electron microscopy and optical coherence tomography for imaging of coronary bifurcation stents

Optical coherence tomography (OCT) is a new intracoronary imaging modality that has excellent resolution and image quality and has been used to image neointimal coverage after stent implantation. OCT has been compared to histologic, intravascular ultrasound, and scanning electron microscopy (SEM) studies. However, OCT has not been compared with SEM for imaging stent coverage over side branches.

3D registration of intravascular optical coherence tomography and cryo-image volumes for microscopic-resolution validation

High resolution, 100 frames/sec intravascular optical coherence tomography (IVOCT) can distinguish plaque types, but further validation is needed, especially for automated plaque characterization. We developed experimental and 3D registration methods, to provide validation of IVOCT pullback volumes using microscopic, brightfield and fluorescent cryoimage volumes, with optional, exactly registered cryo-histology. The innovation was a method to match an IVOCT pullback images, acquired in the catheter reference frame, to a true 3D cryo-image volume. Briefly, an 11-parameter, polynomial virtual catheter was initialized within the cryo-image volume, and perpendicular images were extracted, mimicking IVOCT image acquisition. Virtual catheter parameters were optimized to maximize cryo and IVOCT lumen overlap. Local minima were possible, but when we started within reasonable ranges, every one of 24 digital phantom cases converged to a good solution with a registration error of only +1.34±2.65μm (signed distance). Registration was applied to 10 ex-vivo cadaver coronary arteries (LADs), resulting in 10 registered cryo and IVOCT volumes yielding a total of 421 registered 2D-image pairs. Image overlays demonstrated high continuity between vascular and plaque features. Bland- Altman analysis comparing cryo and IVOCT lumen area, showed mean and standard deviation of differences as 0.01±0.43 mm2. DICE coefficients were 0.91±0.04. Finally, visual assessment on 20 representative cases with easily identifiable features suggested registration accuracy within one frame of IVOCT (±200μm), eliminating significant misinterpretations introduced by 1mm errors in the literature. The method will provide 3D data for training of IVOCT plaque algorithms and can be used for validation of other intravascular imaging modalities.