Takahiro Imanaka

Impact of contrast-induced acute kidney injury on outcomes in patients with ST-segment elevation myocardial infarction undergoing primary percutaneous coronary intervention.

PURPOSE The purpose of this study was to identify predictors of contrast-induced acute kidney injury (CI-AKI) and the effect of CI-AKI on cardiovascular outcomes after hospital discharge in patients with ST-segment elevation myocardial infarction (STEMI) treated with primary percutaneous coronary intervention (PCI). METHODS AND MATERIALS We retrospectively reviewed 194 STEMI consecutive patients who underwent primary PCI to evaluate the predictors for CI-AKI and 187 survivors to examine all-cause mortality and cardiovascular events. Outcomes were compared between patients with CI-AKI and those without CI-AKI, which was defined as an increase >50% or >0.5mg/dl in serum creatinine concentration within 48hours after primary PCI. RESULTS CI-AKI occurred in 23 patients (11.9%). Multivariate analysis identified pre-procedural renal insufficiency as a predictor of CI-AKI, and this predictor was independent from hemodynamic instability and excessive contrast volume. Receiver-operator characteristics analysis demonstrated that patients with an estimated glomerular filtration rate (eGFR) of ≤43.6ml/min per 1.73m(2) had the potential for CI-AKI. Patients who developed CI-AKI had higher mortality and cardiovascular events than did those without CI-AKI (27.8% vs. 4.7%; log-rank P=.0003, 27.8% vs. 11.2%; log-rank P=.0181, respectively). Cox proportional hazards model analysis identified CI-AKI as the independent predictor of mortality and cardiovascular events [hazard ratio [HR]=5.36; P=.0076, HR=3.10; P=.0250, respectively]. CONCLUSIONS The risk of CI-AKI is increased in patients with pre-procedural renal insufficiency, and eGFR is clinically useful in the emergent setting for CI-AKI risk stratification before primary PCI.

Thermodilution-Derived Coronary Blood Flow Pattern Immediately After Coronary Intervention as a Predictor of Microcirculatory Damage and Midterm Clinical Outcomes in Patients With ST-Segment–Elevation Myocardial Infarction

Background—Despite a sufficient coronary blood flow after primary percutaneous coronary intervention for patients with ST-segment–elevation myocardial infarction; some patients have a poor outcome because of microcirculatory damage. This study evaluates whether the thermodilution-derived coronary blood flow parameters immediately after primary percutaneous coronary intervention predict early microvascular damage and midterm outcomes in patients with ST-segment–elevation myocardial infarction. Methods and Results—Using a pressure sensor/thermistor-tipped guidewire, we measured the index of microcirculatory resistance at maximum hyperemia, and coronary blood flow pattern was assessed from the thermodilution curves after successful primary percutaneous coronary intervention in 88 patients with ST-segment–elevation myocardial infarction. Coronary blood flow pattern was classified into 3 groups according to the shape of thermodilution curve: a narrow unimodal (n=41), a wide unimodal (n=32), or bimodal (n=15). All patients had contrast-enhanced cardiac magnetic resonance scans within 2 weeks. The index of microcirculatory resistance values were significantly higher both in a wide unimodal and in a bimodal groups than in a narrow unimodal group (65±41 and 76±38 versus 20±9U; P<0.001). Bimodal group had higher prevalence of microvascular obstruction on contrast-enhanced cardiac magnetic resonance when compared with the other groups (100%, 78%, and 30%; P<0.001). Patients in bimodal group had a higher risk of death and heart failure rehospitalization at 6 months (73%, 6.3%, 7.3%; P<0.001). Multivariate analysis revealed that bimodal shape of the thermodilution curve was the only independent predictor of cardiac death at 6 months after ST-segment–elevation myocardial infarction (P<0.01). Conclusions—A bimodal shape of the thermodilution curve, which may indicate myocardial edema and consequent extrinsic compression of the capillary network, is associated with microcirculatory damage and poor midterm clinical outcomes rather than index of microcirculatory resistance value itself.

Ex vivo assessment of neointimal characteristics after drug-eluting stent implantation: Optical coherence tomography and histopathology validation study.

BACKGROUND Optical coherence tomography (OCT) is one of the tools trying to distinguish neoatherosclerosis from other neointimal tissue but its role has to be still validated. This study evaluated the diagnostic accuracy of OCT for characterization of lipid-atherosclerotic neointima following drug-eluting stent (DES) implantation. METHODS Twelve stented coronary arteries from the 7 autopsy hearts were imaged by OCT. These OCT images were compared with histology. By OCT, the morphological appearances of neointima were classified into three patterns: homogeneous pattern, heterogeneous pattern with visible strut, or heterogeneous pattern with invisible strut. RESULTS Of 21 histological cross-sections, 6 were categorized as homogeneous patterns (29%), 11 as heterogeneous patterns with visible stent strut (52%), and 4 as heterogeneous patterns with invisible stent strut (19%). All homogeneous patterns were composed of smooth muscle cells with collagen fibers. The heterogeneous patterns with visible stent strut included proteoglycan-rich myxomatous matrix and calcium deposition. On the other hand, the heterogeneous patterns with invisible stent strut comprised atheromatous tissue, including a large amount of foam cell accumulation (25%) or large fibroatheroma/necrotic core (75%) inside the stent struts within neointima. The optical attenuation coefficient was highest in the heterogeneous pattern with invisible stent strut due to scattering of light by atheromatous tissue. CONCLUSION The heterogeneous patterns with invisible stent strut on OCT imaging identify the presence of lipid-atherosclerotic tissue within neointima after DES. This may suggest the potential capability of OCT based on visualization of stent struts for discriminating atheromatous formation within neointima from other neointimal tissue.

Intravascular Ultrasound-Derived Stent Dimensions as Predictors of Angiographic Restenosis Following Nitinol Stent Implantation in the Superficial Femoral Artery.

Purpose: To identify intravascular ultrasound (IVUS) measurements that can predict angiographic in-stent restenosis (ISR) following nitinol stent implantation in superficial femoral artery (SFA) lesions. Methods: A retrospective review was conducted of 97 patients (mean age 72.9±8.9 years; 63 men) who underwent IVUS examination during endovascular treatment of 112 de novo SFA lesions between July 2012 and December 2014. Self-expanding bare stents were implanted in 46 lesions and paclitaxel-eluting stents in 39 lesions. Six months after stenting, follow-up angiography was conducted to assess stent patency. The primary endpoint was angiographic ISR determined by quantitative vascular angiography analysis at the 6-month follow-up. Variables associated with restenosis were sought in multivariate analysis; the results are presented as the odds ratio (OR) and 95% confidence interval (CI). Results: At follow-up, 27 (31.8%) angiographic ISR lesions were recorded. The lesions treated with uncoated stents were more prevalent in the ISR group compared with the no restenosis group (74.1% vs 44.8%, p=0.02). Lesion length was longer (154.4±79.5 vs 109.0±89.3 mm, p=0.03) and postprocedure minimum stent area (MSA) measured by IVUS was smaller (13.9±2.8 vs 16.3±1.6 mm2, p<0.001) in the ISR group. Multivariate analysis revealed that bare stent use (OR 7.11, 95% CI 1.70 to 29.80, p<0.01) and longer lesion length (OR 1.08, 95% CI 1.01 to 1.16, p=0.04) were predictors of ISR, while increasing postprocedure MSA (OR 0.58, 95% CI 0.41 to 0.82, p<0.01) was associated with lower risk of ISR. Receiver operating characteristic analysis identified a MSA of 15.5 mm2 as the optimal cutpoint below which the incidence of restenosis increased (area under the curve 0.769). Conclusion: Postprocedure MSA can predict ISR in SFA lesions, which suggests that adequate stent enlargement during angioplasty might be required for superior patency.

Histopathological validation of optical frequency domain imaging to quantify various types of coronary calcifications.

Aims This study evaluated whether optical frequency domain imaging (OFDI) could identify various coronary calcifications and accurately measure calcification thickness in comparison with histopathology. Methods and results A total of 902 pathological cross‐sections from 44 coronary artery specimens of human cadavers were examined to compare OFDI and histological images. Histological coronary calcification was classified into four different types: (i) superficial dense calcified plates, (ii) deep intimal calcification, (iii) scattered microcalcification, and (iv) calcified nodule. The thickness of calcification was measured when both the leading and trailing edges of calcification were visible on OFDI. Of the 902 histological cross‐sections, 158 (18%) had calcification: 105 (66%) were classified as superficial dense calcified plates, 20 (13%) as deep intimal calcifications, 30 (19%) as scattered microcalcifications, and 3 (2%) as calcified nodules. Superficial dense calcified plates appeared as well‐delineated heterogeneous signal‐poor regions with sharp borders on OFDI. Deep intimal calcifications could not be identified on OFDI. Scattered microcalcification appeared as homogeneous low intensity areas with indiscriminant borders. Calcified nodule, a high‐backscattering protruding mass with an irregular surface, also appeared as a low intensity area with a diffuse border. The ROC analysis identified calcium thicknesses <893 µm as cut points for the prediction of measurable calcification (72% sensitivity and 91% specificity, area under the curve = 0.893, P < 0.001). Conclusion Our study demonstrated the potential capability of OFDI to characterize various types of coronary calcifications, which may contribute to the understanding of the pathogenesis of coronary atherosclerosis.

Tissue Characterization of In-Stent Neointima Using Optical Coherence Tomography in the Late Phase After Bare-Metal Stent Implantation – An Ex Vivo Validation Study –

BACKGROUND We performed an ex vivo study to investigate optical coherence tomography (OCT) imaging for differentiating several types of neointimal tissue during the later phases after bare-metal stent (BMS) implantation as compared with histologic results. METHODSANDRESULTS OCT imaging was performed in 6 autopsy hearts for 10 BMS with implant duration >4 years. OCT qualitative neointimal tissue characterization was based on tissue structure and classified as homogeneous pattern, heterogeneous pattern with visible struts, or heterogeneous pattern with invisible struts. Corresponding histological analyses of each 2-mm cross-section of the entire BMS were performed. Of 81 cross-sections, histological analysis revealed that the homogeneous pattern of neointima on OCT (n=39) contained smooth muscle cells with collagen, indicating high neointimal maturity. The heterogeneous patterns with visible struts (n=35) contained different tissues, including a proteoglycan-rich myxomatous matrix or dense calcified plate deposition. The heterogeneous patterns with invisible struts (n=7) included neointimal lipid/necrotic core formation, accumulation of foam cells, or microcalcification scattering. Of the 66 cross-sections containing large microvessels within the neointima on histology, only 6 (9%) were visualized by OCT. CONCLUSIONS The present study confirmed the potential use of OCT in differentiating several types of neointima after BMS implantation. The image interpretation of OCT, based on visualization of stent struts, enables identification of several types of neointimal tissues, including in-stent fibroatheroma formation, more accurately.

Natural history of low-intensity neointimal tissue after an everolimus-eluting stent implantation: a serial observation with optical coherence tomography

Although previous optical coherence tomography (OCT) studies reported that restenosis tissue after implantation of a drug-eluting stent (DES) was composed of a variety of cells, the clinical significance of morphologic characteristics for in-stent neointimal tissue as assessed by OCT has not been clarified. We experienced a patient with stable angina who underwent percutaneous coronary intervention with a 2.5 × 18-mm DES implantation 6 months before the OCT examination. OCT imaging showed a mild intimal hyperplasia (39 % neointimal hyperplasia) with eccentric, heterogeneous tissue, predominantly of low signal intensity. Seventeen months after the initial procedure, OCT revealed a significant increase in percent neointimal hyperplasia of 58 %, with morphologically different intimal tissue of concentric homogeneous high intensity in the stented segments. This finding suggests that low-intensity intimal tissue morphology detected by OCT could be a morphometric predictor of late neointimal tissue growth after DES implantation.

Strut Coverage After Paclitaxel-Eluting Stent Implantation in the Superficial Femoral Artery

In the superficial femoral artery (SFA), quantitative analysis for vascular healing response after self-expanding nitinol bare metal stent (BMS) or drug-eluting stent (DES) implantation is limited. The purpose of this study was to evaluate the endothelial strut coverage after nitinol paclitaxel-

Impact of analysis interval size on the quality of optical frequency domain imaging assessments of stent implantation for lesions of the superficial femoral artery.

This study aimed to investigate the influence of analysis interval size on optical frequency domain imaging (OFDI) assessment of stent therapy for lesions of the superficial femoral artery (SFA). Background. No consensus or validating data are available with respect to the methodology of intravascular imaging analysis for the peripheral arteries. Methods. OFDI was performed for 30 SFA lesions, during endovascular therapy and at the 6‐month follow‐up. Initially, lumen and stent borders were traced at 1‐mm axial intervals. Volumes were calculated using a PC‐based software, and the volume index (VI) was defined as the volume divided by the stent length. Two additional OFDI analyses were performed using 2‐mm and 5‐mm intervals, thereby reducing the number of cross‐sectional image frames analyzed. Results. The mean stent length was 89.7 ± 35.2 mm. The mean difference in baseline minimum lumen area (MLA) was 0.4 mm2 between MLA values from the 1‐mm and 2‐mm interval analyses, and 2.2 mm2 between MLA values from the 1‐mm and 5‐mm interval analyses. In volumetric analysis, there were excellent correlations and good agreements for stent, lumen, and neointimal VI measurements obtained on the basis of different analysis intervals. Conclusions. Using large intervals in OFDI analyses of SFA lesions resulted in few differences in measurement variability of volumetric parameters. However, planar analysis for MLA assessment can be susceptible to high variability when large intervals are applied.

Impact of stent diameter on vascular response after self-expanding paclitaxel-eluting stent implantation in the superficial femoral artery ☆

BACKGROUND The optimal sizing of self-expanding paclitaxel-eluting stents (PES) in the treatment for superficial femoral artery (SFA) lesions is unclear. This study sought to investigate the influence of PES diameter on stent patency in SFA lesions using optical frequency domain imaging (OFDI). METHODS A total of 20 de novo SFA lesions were randomized 1:1 to receive either self-expanding PES with a nominal diameter of 6mm or 8mm. Follow-up angiography and OFDI was scheduled six months after stent implantation, and volumetric OFDI analysis was performed to evaluate vascular response to the stents. Volume index (VI) was defined as the volume divided by the stent length. The primary end point was lumen VI at the 6-month follow-up. Secondary end point was minimum lumen diameter (MLD) by quantitative vascular angiography (QVA) at the follow-up. RESULTS Stent length was 78.0±23.9mm in the 6-mm group and 70.0±23.6mm in the 8-mm group (p=0.46). Baseline QVA data were also similar between the two groups. MLD immediately after stent implantation was similar between the two groups (4.2±0.5mm in the 6-mm group and 3.9±0.5mm in the 8-mm group, p=NS). At the 6-month follow-up, MLD was greater in the 8-mm group compared to the 6-mm group (4.0±1.0mm vs. 3.2±0.4mm, p<0.05). Stent VI was larger in the 8-mm group (28.4±6.7mm3/mm vs. 22.2±1.2mm3/mm, p=0.01). Neointimal VI was similar between the two groups (5.8±2.9mm3/mm vs. 5.2±2.6mm3/mm, p=0.68). Lumen VI was greater in the 8-mm group (23.2±7.6mm3/mm vs. 17.3±2.6mm3/mm, p=0.04). CONCLUSIONS Chronic stent enlargement resulted in greater lumen area after implantation of self-expanding PES with a large diameter at the mid-term follow-up. Stent diameter might be important for stent patency in procedure with PES for SFA lesions.