In Vivo Quantitative Tissue Characterization of Angiographically Normal Coronary Lesions and the Relation With Risk Factors A Study Using Integrated Backscatter Intravascular Ultrasound

Deep learning with convolutional neural network for estimation of the characterisation of coronary plaques: Validation using IB-IVUS

INTRODUCTION

Deep learning approaches have shown high diagnostic performance in image classifications, such as differentiation of malignant tumors and calcified coronary plaque. However, it is unknown whether deep learning is useful for characterizing coronary plaques without the presence of calcification using coronary computed tomography angiography (CCTA). The purpose of this study was to compare the diagnostic performance of deep learning with a convolutional neural network (CNN) with that of radiologists in the estimation of coronary plaques.

METHODS

We retrospectively enrolled 178 patients (191 coronary plaques) who had undergone CCTA and integrated backscatter intravascular ultrasonography (IB-IVUS) studies. IB-IVUS diagnosed 81 fibrous and 110 fatty or fibro-fatty plaques. We manually captured vascular short-axis images of the coronary plaques as Portable Network Graphics (PNG) images (150 × 150 pixels). The display window level and width were 100 and 700 Hounsfield units (HU), respectively. The deep-learning system (CNN; GoogleNet Inception v3) was trained on 153 plaques; its performance was tested on 38 plaques. The area under the curve (AUC) obtained by receiver operating characteristic analysis of the deep learning system and by two board-certified radiologists was compared.

RESULTS

With the CNN, the AUC and the 95% confidence interval were 0.83 and 0.69-0.96, respectively; for radiologist 1 they were 0.61 and 0.42-0.80; for radiologist 2 they were 0.68 and 0.51-0.86, respectively. The AUC for CNN was significantly higher than for radiologists 1 (p = 0.04); for radiologist 2 it was not significantly different (p = 0.22).

CONCLUSION

DL-CNN performed comparably to radiologists for discrimination between fatty and fibro-fatty plaque on CCTA images.

IMPLICATIONS FOR PRACTICE

The diagnostic performance of the CNN and of two radiologists in the assessment of 191 ROIs on CT images of coronary plaques whose type corresponded with their IB-IVUS characterization was comparable.

Using optical coherence tomography and intravascular ultrasound imaging to quantify coronary plaque cap thickness and vulnerability: a pilot study

Background

Detecting coronary vulnerable plaques in vivo and assessing their vulnerability have been great challenges for clinicians and the research community. Intravascular ultrasound (IVUS) is commonly used in clinical practice for diagnosis and treatment decisions. However, due to IVUS limited resolution (about 150–200 µm), it is not sufficient to detect vulnerable plaques with a threshold cap thickness of 65 µm. Optical Coherence Tomography (OCT) has a resolution of 15–20 µm and can measure fibrous cap thickness more accurately. The aim of this study was to use OCT as the benchmark to obtain patient-specific coronary plaque cap thickness and evaluate the differences between OCT and IVUS fibrous cap quantifications. A cap index with integer values 0–4 was also introduced as a quantitative measure of plaque vulnerability to study plaque vulnerability.

Methods

Data from 10 patients (mean age: 70.4; m: 6; f: 4) with coronary heart disease who underwent IVUS, OCT, and angiography were collected at Cardiovascular Research Foundation (CRF) using approved protocol with informed consent obtained. 348 slices with lipid core and fibrous caps were selected for study. Convolutional Neural Network (CNN)-based and expert-based data segmentation were performed using established methods previously published. Cap thickness data were extracted to quantify differences between IVUS and OCT measurements.

Results

For the 348 slices analyzed, the mean value difference between OCT and IVUS cap thickness measurements was 1.83% (p = 0.031). However, mean value of point-to-point differences was 35.76%. Comparing minimum cap thickness for each plaque, the mean value of the 20 plaque IVUS-OCT differences was 44.46%, ranging from 2.36% to 91.15%. For cap index values assigned to the 348 slices, the disagreement between OCT and IVUS assignments was 25%. However, for the OCT cap index = 2 and 3 groups, the disagreement rates were 91% and 80%, respectively. Furthermore, the observation of cap index changes from baseline to follow-up indicated that IVUS results differed from OCT by 80%.

Conclusions

These preliminary results demonstrated that there were significant differences between IVUS and OCT plaque cap thickness measurements. Large-scale patient studies are needed to confirm our findings.

Macrophage accumulation within coronary arterial wall in diabetic patients with acute coronary syndrome: a study with in-vivo intravascular imaging modalities

Background and aims

Macrophage accumulation in arteriosclerotic plaque of coronary arteries is involved in plaque destabilization. Atherosclerosis has been known to be progressive in patients with type 2 diabetes mellitus (DM). This study compared the features of 3-dimensional (3D) spatial distribution of macrophage accumulation within coronary artery wall between acute coronary syndrome (ACS) patients with DM (n = 20) and those without (non-DM, n = 20) by using intravascular ultrasound (IVUS) and optical coherence tomography (OCT).

Methods

The OCT-derived macrophage accumulation was measured within the proximal left anterior-descending artery. This measurement was performed for the whole vessel segment of interest, higher shear stress region (flow divider side) and lower shear stress region (the opposite side).

Results

Normalized macrophage accumulation per unit length of the whole segment of interest was significantly larger in ACS patients with DM than without. In non-DM patients, macrophage density per IVUS-derived plaque volume was significantly higher in high shear stress region compared to low shear stress region, however, there was no significant difference between the two regions in DM patients. The macrophage density in the low shear stress region was significantly higher in the DM group than in the non-DM group. A multivariate analysis showed that the presence of DM was a major determinant for macrophage distribution.

Conclusions

Macrophage accumulation was more abundant and homogeneous within coronary arterial wall in DM patients with ACS compared to non-DM patients, suggesting that plaque destabilization may occur more widely throughout coronary wall in DM patients.

Coronary Atherosclerotic Plaque Volume Quantified by Computed Tomographic Angiography in Smokers Compared to Nonsmokers

RATIONALE AND OBJECTIVES

We sought to compare the prevalence and volume of lipid plaque, fibrous plaque, and calcified plaque in patients with smokers versus nonsmokers.

MATERIALS AND METHODS

We studied consecutive patients suspected of coronary artery disease and who underwent coronary computed tomography angiography. A structured interview and review of existing clinical data was conducted before computed tomography angiography to collect information on demographic characteristics, the presence of cardiovascular risk factors. The volume of lipid, fibrous, and calcified plaque were automatically calculated and marked in different colors according to predefined Hounsfield unit thresholds. The prevalence and volume of plaques were compared between smokers and nonsmokers.

RESULTS

Overall 6380 patients (3351 men and 3029 women, mean age 55.35 years) were finally analyzed, of whom 2075 (32.5%) were smokers, and 4305 (67.5%) were never smokers. The prevalence of any plaque in smokers was significantly higher compared to never smokers (47.7% vs. 32.3%, p < 0.001). Smoking was an independent risk factor of the presence of any plaque after correcting for age, gender, body mass index, hypertension, dyslipidemia, diabetes, and family history in a multivariate model (odds ratio = 1.250 (1.088-1.437), p = 0.002). The volume of lipid plaque, fibrous plaque, calcified plaque, and total plaque in smokers was significantly greater than nonsmokers (p < 0.001).

CONCLUSION

The prevalence and volume of lipid plaque, fibrous plaque, and calcified plaque were significantly higher in smokers versus never smokers.

Relationship of serum salusin beta levels with coronary slow flow

OBJECTIVE

The pathophysiology of coronary slow flow (CSF) has not been clarified. Salusin-β is released predominantly from the atheroma plaques and influences the pathophysiologic processes of atherosclerosis. Therefore, this study aimed to determine serum salusin-β levels in CSF and its correlation with CSF.

METHODS

The study included 39 patients with CSF, and the control group (n=42) consisted of consecutive subjects with normal coronary arteriogram. We measured salusin-β and thrombolysis in myocardial infarction frame count (TFC).

RESULTS

Age, body mass index (BMI), systolic blood pressure, diabetes, hyperlipidemia, and smoking rates were similar (p values>0.05) in both groups. High sensitive C-reactive protein (2.80±1.2 vs. 2.21±1.2 mg/dL, p=0.011), salusin-β [1205 (330-2092) vs. 162 (29-676), pg/ml, p<0.001], corrected TFC of left anterior descending coronary artery (29±9 vs. 19.7±3.7, p<0.001), circumflex artery TFC (25±10 vs. 15±3.2, p<0.001), right coronary artery TFC (28±7.1 vs. 13±3.3, p<0.001), and mean TFC (28±4.4 vs. 16±3.7, p<0.001) were significantly higher in the CSF group. In univariate and multivariate regression analysis, only BMI (unstandardized β±SE=0.178±0.08, p=0.036) and salusin-β levels (unstandardized β±SE=0.006±0.01, p<0.001) were determined as predictors of CSF. There was a good correlation between serum salusin-β and mean TFC values (r=0.564; p<0.001).

CONCLUSION

There is an association between serum salusin-β levels and CSF.

Machine-learning integration of CT histogram analysis to evaluate the composition of atherosclerotic plaques: Validation with IB-IVUS

BACKGROUND

To determine whether machine learning with histogram analysis of coronary CT angiography (CCTA) yields higher diagnostic performance for coronary plaque characterization than the conventional cut-off method using the median CT number.

METHODS

We included 78 patients with 78 coronary plaques who had undergone CCTA and integrated backscatter intravascular ultrasound (IB-IVUS) studies. IB-IVUS diagnosed 32 as fibrous- and 46 as fatty or fibro-fatty plaques. We recorded the coronary CT number and 7 histogram parameters (minimum and mean value, standard deviation (SD), maximum value, skewness, kurtosis, and entropy) of the plaque CT number. We also evaluated the importance of each feature using the Gini index which rates the importance of individual features. For calculations we used XGBoost. Using 5-fold cross validation of the plaque CT number, the area under the receiver operating characteristic curve of the machine learning- (extreme gradient boosting) and the conventional cut-off method was compared.

RESULTS

The median CT number was 56.38 Hounsfield units (HU, 8.00-95.90) for fibrous- and 1.15 HU (-35.8-113.30) for fatty- or fibro-fatty plaques. The calculated optimal threshold for the plaque CT number was 36.1 ± 2.8 HU. The highest Gini index was the coronary CT number (0.19) followed by the minimum value (0.17), kurtosis (0.17), entropy (0.14), skewness (0.11), the mean value (0.11), the standard deviation (0.06), and the maximum value (0.05), and energy (0.00). By validation analysis, the machine learning-yielded a significantly higher area under the curve than the conventional method (area under the curve 0.92 and 95%, confidence interval 0.86-0.92 vs 0.83 and 0.75-0.92, p = 0.001).

CONCLUSION

The machine learning-was superior the conventional cut-off method for coronary plaque characterization using the plaque CT number on CCTA images.

Effect of sitagliptin on plaque changes in coronary artery following acute coronary syndrome in diabetic patients: The ESPECIAL-ACS study

BACKGROUND

Dipeptidyl peptidase-4 (DPP-4) inhibitors have anti-atherosclerotic and cardioprotective effects in vitro. However, the impact of DPP-4 inhibitors on coronary plaque remains unclear. We sought to assess the effect of sitagliptin on coronary plaque volume (PV) and stabilization in diabetic patients with acute coronary syndrome (ACS).

METHODS

The ESPECIAL-ACS was a prospective, randomized, open-label, parallel group study at 4 Japanese centers to assess the effect of 6-month treatment with sitagliptin on coronary plaque changes in non-culprit lesion in diabetic patients with ACS using serial intravascular ultrasound (IVUS) and integrated backscatter IVUS (IB-IVUS) analysis.

RESULTS

A total of 41 patients were randomly allocated to either sitagliptin group (diet and exercise with sitagliptin 50-100mg daily, n=21) or control group (diet and exercise, n=20) within 72h after percutaneous coronary intervention, and underwent volumetric IVUS and IB-IVUS analyses at baseline and 6-month follow-up. At 6-month follow-up, the percent change in PV as primary endpoint was larger in the sitagliptin group than in the control group, but the difference was not statistically significant (-4.0±8.5% vs. -1.4±8.8%, p=0.35). In IB-IVUS analysis, the percent change in lipid PV significantly decreased in the sitagliptin group compared with the control group (-7.1±21.5% vs. 15.6±41.8%, p=0.03).

CONCLUSIONS

Compared with diet and exercise therapy, sitagliptin did not significantly reduce coronary PV in diabetic patients with ACS at 6-month follow-up. However, the percent change in lipid PV significantly decreased in the sitagliptin group, suggesting that sitagliptin has a potential to stabilize the plaque vulnerability.

Smoking in Relation to Coronary Atherosclerotic Plaque Burden, Volume and Composition on Intravascular Ultrasound

Background

This study aimed to evaluate the relationship between cigarette smoking and coronary atherosclerotic burden, volume and composition as determined in-vivo by grayscale and virtual histology (VH) intravascular ultrasound (IVUS).

Methods and Results

Between 2008 and 2011, (VH-)IVUS of a non-culprit coronary artery was performed in 581 patients undergoing coronary angiography. To account for differences in baseline characteristics, current smokers were matched to never smokers by age, gender and indication for catheterization, resulting in 280 patients available for further analysis. Coronary atherosclerotic plaque volume, burden, composition (fibrous, fibro-fatty, dense calcium and necrotic core) and high-risk lesions (VH-IVUS derived thin-cap fibroatheroma (TCFA), plaque burden ≥70%, minimal luminal area ≤4.0 mm²) were assessed. Cigarette smoking showed a tendency towards higher coronary plaque burden (mean±SD, 38.6±12.5% in current versus 36.4±11.0% in never smokers, p = 0.080; and odds ratio (OR) of current smoking for plaque burden above versus below the median 1.69 (1.04–2.75), p = 0.033). This effect was driven by an association in patients presenting with an acute coronary syndrome (ACS) (current smokers, plaque burden 38.3±12.8% versus never smokers, plaque burden 35.0±11.2%, p = 0.049; OR 1.88 (1.02–3.44), p = 0.042). Fibrous tissue tended to be lower in current smokers (mean±SD, 57.7±10.5% versus 60.4±12.6%, p = 0.050) and fibro-fatty tissue was higher in current smokers (median[IQR], 9.6[6.0–13.7]% versus 8.6[5.8–12.2]%, p = 0.039). However, differences in percentage necrotic core and dense calcium could not be demonstrated. Also, no differences were found with regard to high-risk lesions.

Conclusions

An association between smoking and degree of coronary atherosclerosis was present in patients undergoing coronary angiography who presented with ACS. Although smoking was associated with higher fibro-fatty percentage, no associations could be demonstrated with percentage necrotic core, nor with VH-IVUS derived TCFA lesions. Since the magnitude of the differences in both degree and composition of atherosclerosis was modest, clinical relevance of the findings may be questioned.

Comparison of carotid plaque tissue characteristics in patients with acute coronary syndrome or stable angina pectoris: assessment by iPlaque, transcutaneous carotid ultrasonography with integrated backscatter analysis

Background

The association of the tissue characteristics of carotid plaques with coronary artery disease has attracted interest. The present study compared the tissue characteristics of carotid plaques in patients with acute coronary syndrome (ACS) with those in patients with stable angina pectoris (SAP) using the iPlaque system, which is based on ultrasound integrated backscatter.

Methods and results

Carotid ultrasound examinations were performed in 26 patients with ACS, and 38 age- and gender-matched patients with SAP. Neither plaque area nor maximal intima-media thickness differed significantly between the two groups. However, the average integrated backscatter value within the plaque was greater in the ACS patients than in the SAP patients. iPlaque analysis revealed that the percentage blue area (lipid pool) was greater in the ACS patients than in the SAP patients (43.4 ± 11.2 vs 18.3 ± 10.3 %, p < 0.0001), and that the percentage green area (fibrosis) was lower in the ACS than in the SAP patients (7.5 ± 7.5 % vs 20.7 ± 11.7 %, p < 0.0001).

Conclusions

The lipid component of carotid plaques is greater in ACS patients than in SAP patients. Our iPlaque system provides a useful and feasible method for the tissue characterization of carotid plaques in the clinical setting.

Echocardiographic integrated backscatter for assessing reduction of aortic valve calcifications by R-568 in a rat model of chronic kidney disease

Chronic kidney disease (CKD) and secondary hyper-parathyroidism are associated with calcific aortic valve disease (CAVD). Innovative modalities for imaging CAVD are warranted. Our aim was to use echocardiographic calibrated integrated backscatter (cIB) to quantitatively determine the preventive effect of the calcimimetic R-568 on CAVD in a CKD rat model, and to compare the results with those of micro-computed tomography and histology. Thirty-six male Wistar rats were followed for 7 wk. Rats were divided into four groups with respect to treatment: (1) adenine 0.5% to induce CKD + vehicle; (2) adenine + R-568 (30 mg/kg/d); (3) control, normal diet + vehicle; (4) controls, normal diet + R-568. At week 7, cIB values of the aortic valve were significantly lower in R-568-treated group 2 than in vehicle-treated group 1. This was confirmed by the significantly lower calcified volume observed on micro-computed tomography and the calcified area observed on histology. There were no significant differences in fractional area change and aortic valve area between groups. In conclusion, echocardiographic cIB was able to quantitatively assess a reduction in CAVD by R-568 in a rat model of CKD.

Relation between the GRACE score and severity of atherosclerosis in acute coronary syndrome

BACKGROUND

Patients with non-ST-elevation acute coronary syndrome are heterogeneous in terms of clinical presentation and immediate- and long-term risk of death or non-fatal ischemic events. The aim of the present study was to evaluate the relationship between the Global Registry of Acute Coronary Events (GRACE) score and severity of coronary artery disease angiographically evaluated by Gensini score in patients with non-ST-elevation acute coronary syndrome.

METHODS

A total of 245 patients with non-ST-elevation acute coronary syndrome were enrolled to the study. Based on the GRACE risk score classification system, the patients were divided into low- (n=97, 39.6%), intermediate- (n=84, 34.3%), and high- (n=64, 26.1%) risk groups. All patients underwent coronary angiography within five days after admission.

RESULTS

The Gensini scores were 26±29 in the low-risk group, 29±19 in the intermediate-risk group, and 38±23 in the high-risk group (p=0.016). The low-risk group was significantly different from the high-risk group (p=0.013), and the difference from the intermediate-risk group almost reached significance. Normal, noncritical, one and two, or multivessel disease were identified in 15 (6.1%), 31 (12.7%), 75 (30.6%), and 124 (50.6%) patients, respectively. The prevalence of multivessel disease was 28% in the low-risk group, 30% in the intermediate-risk group, and 42% in the high-risk group. The high-risk group was significantly different from the low-risk group (p<0.01).

CONCLUSION

Our study demonstrates that the GRACE score has significant value for assessing the severity and extent of coronary artery stenosis in patients with non-ST-elevation acute coronary syndrome.

High HbA1c levels correlate with reduced plaque regression during statin treatment in patients with stable coronary artery disease: results of the coronary atherosclerosis study measuring effects of rosuvastatin using intravascular ultrasound in Japanese subjects (COSMOS)

Background

The incidence of cardiac events is higher in patients with diabetes than in people without diabetes. The Coronary Atherosclerosis Study Measuring Effects of Rosuvastatin Using Intravascular Ultrasound in Japanese Subjects (COSMOS) demonstrated significant plaque regression in Japanese patients with chronic coronary disease after 76 weeks of rosuvastatin (2.5 mg once daily, up-titrated to a maximum of 20 mg/day to achieve LDL cholesterol <80 mg/dl).

Methods

In this subanalysis of COSMOS, we examined the association between HbA1c and plaque regression in 40 patients with HbA1c ≥6.5% (high group) and 86 patients with HbA1c <6.5% (low group).

Results

In multivariate analyses, HbA1c and plaque volume at baseline were major determinants of plaque regression. LDL cholesterol decreased by 37% and 39% in the high and low groups, respectively, while HDL cholesterol increased by 16% and 22%, respectively. The reduction in plaque volume was significantly (p = 0.04) greater in the low group (from 71.0 ± 39.9 to 64.7 ± 34.7 mm³) than in the high group (from 74.3 ± 34.2 to 71.4 ± 32.3 mm³). Vessel volume increased in the high group but not in the low group (change from baseline: +4.2% vs −0.8%, p = 0.02). Change in plaque volume was significantly correlated with baseline HbA1c.

Conclusions

Despite similar improvements in lipid levels, plaque regression was less pronounced in patients with high HbA1c levels compared with those with low levels. Tight glucose control during statin therapy may enhance plaque regression in patients with stable coronary disease.

Trial registration

ClinicalTrials.gov, Identifier NCT00329160

Visualization of coronary plaque in type 2 diabetes mellitus patients using a new 40 MHz intravascular ultrasound imaging system

BACKGROUND

Previous epidemiological studies demonstrated plaque vulnerability to be high in diabetic patients. iMap-intravascular ultrasound (IVUS) is a recently developed radiofrequency 40 MHz IVUS imaging system for tissue characterization. This study aimed to characterize coronary plaque in target lesions of diabetic patients using iMap-IVUS.

METHODS

We studied 175 treated vessels in 146 patients with stable angina pectoris and analyzed plaque components of culprit lesions by iMAP-IVUS. Patients were divided into 2 groups: non-diabetic (non-DM: 112 vessels, 93 patients) and diabetic (DM: 63 vessels, 53 patients).

RESULTS

In gray-scale IVUS 2D analysis, there were no differences in IVUS parameters. In 3D analysis, the DM group tended to have a larger plaque volume (p=0.07) and plaque burden (p=0.10). At minimum lumen sites, the absolute lipidic and necrotic areas (0.84 ± 0.44 mm(2) vs. 0.58 ± 0.41 mm(2), p<0.001, and 2.42 ± 1.65 mm(2) vs. 1.46 ± 1.76 mm(2), p<0.001, respectively) and percent lipidic and necrotic areas were significantly greater in the DM than in the non-DM group (8.39 ± 3.38% vs. 5.25 ± 2.30%, p<0.0001, and 23.65 ± 11.54% vs. 12.99 ± 10.71%, p<0.0001, respectively). In addition, the absolute lipidic and necrotic volumes (11.75 ± 10.59 mm(3) vs. 8.18 ± 6.24 mm(3), p<0.01, and 29.99 ± 28.90 mm(3) vs. 19.44 ± 19.35 mm(3), p<0.01, respectively) and percent lipidic and necrotic volumes were significantly greater in the DM than in the non-DM group (6.27 ± 1.92% vs. 5.13 ± 1.82%, p<0.0001, and 16.54 ± 7.56% vs. 12.08 ± 6.05%, p<0.0001, respectively).

CONCLUSION

Characterization of coronary plaque by iMAP-IVUS in diabetic patients showed increased lipidic amount and necrotic plaque volume relative to subjects without DM.

Focus on the research utility of intravascular ultrasound - comparison with other invasive modalities

Intravascular ultrasound (IVUS) is an invasive modality which provides cross-sectional images of a coronary artery. In these images both the lumen and outer vessel wall can be identified and accurate estimations of their dimensions and of the plaque burden can be obtained. In addition, further processing of the IVUS backscatter signal helps in the characterization of the type of the plaque and thus it has been used to study the natural history of the atherosclerotic evolution. On the other hand its indigenous limitations do not allow IVUS to assess accurately stent struts coverage, existence of thrombus or exact site of plaque rupture and to identify some of the features associated with increased plaque vulnerability. In order this information to be obtained, other modalities such as optical coherence tomography, angioscopy, near infrared spectroscopy and intravascular magnetic resonance imaging have either been utilized or are under evaluation. The aim of this review article is to present the current utilities of IVUS in research and to discuss its advantages and disadvantages over the other imaging techniques.

Tissue characterization of coronary plaques and assessment of thickness of fibrous cap using integrated backscatter intravascular ultrasound. Comparison with histology and optical coherence tomography

BACKGROUND

The purpose of this study was to develop a new online integrated backscatter intravascular ultrasound (IB-IVUS) system and to validate its ability to measure fibrous cap thickness by comparing IB-IVUS images with those from optical coherence tomography (OCT).

METHODS AND RESULTS

Images were acquired from 125 segments of 26 coronary arteries obtained at autopsy from 11 cadavers. In the training study (n=30), 242 regions-of-interest on color-coded maps were compared with histology. In the validation study, 95 cross-sections were diagnosed by IB-IVUS and histology. In 24 patients with stable angina, 28 arterial cross-sections were imaged by IB-IVUS and OCT in vivo. In the training study, cutoff values of 39 decibels (dB) and 17dB were the optimal predictors of lipid pool/fibrosis and fibrosis/calcification, respectively, with 38-MHz mode; 42dB and 20dB, respectively, with 43-MHz mode. In the validation study, IB classified the fibrous, lipid-rich and fibrocalcific components with an accuracy of 92%, 91% and 95%, respectively. Agreement between the histological and IB-IVUS diagnoses was excellent (Cohen's κ=0.83). There was a correlation between the fibrous cap thickness measured by IB-IVUS and OCT (r=0.74, P<0.001).

CONCLUSIONS

The IB-IVUS system with improved resolution provides high diagnostic accuracy for the analysis of the tissue characteristics of coronary plaques, and enables estimation of the thickness of the fibrous cap in the clinical setting.

Diabetes mellitus is a major negative determinant of coronary plaque regression during statin therapy in patients with acute coronary syndrome--serial intravascular ultrasound observations from the Japan Assessment of Pitavastatin and Atorvastatin in Acute Coronary Syndrome Trial (the JAPAN-ACS Trial)

BACKGROUND

The Japan Assessment of Pitavastatin and Atorvastatin in Acute Coronary Syndrome (JAPAN-ACS) trial has found that early aggressive statin therapy in patients with acute coronary syndrome (ACS) significantly reduces the plaque volume (PV) of non-culprit coronary lesions. The purpose of the present study was to evaluate clinical factors that have an impact on plaque regression using statin therapy.

METHODS AND RESULTS

Serial intravascular ultrasound observations over 8-12 months were performed in 252 ACS patients receiving pitavastatin or atorvastatin. Linear regression analysis identified the presence of diabetes mellitus (DM) and PV at baseline as inhibiting factors, and serum remnant-like particle-cholesterol level at baseline as a significant factor significantly affecting the degree of plaque regression. Significant correlation between % change of PV and low-density lipoprotein cholesterol (LDL-C) level was found in patients with DM (n=73, P<0.05, r=0.4), whereas there was no significant correlation between the 2 parameters in patients without DM (n=178).

CONCLUSIONS

The regression of coronary plaque induced by statin therapy after ACS was weaker in diabetic patients than their counterparts. Moreover, vigorous reduction of the LDL-C levels might induce a greater degree of plaque regression in ACS patients with DM.

In vivo attenuation and equivalent scatterer size parameters for atherosclerotic carotid plaque: preliminary results

We have previously reported on the equivalent scatterer size, attenuation coefficient, and axial strain properties of atherosclerotic plaque ex vivo. Since plaque structure and composition may be damaged during a carotid endarterectomy procedure, characterization of in vivo properties of atherosclerotic plaque is essential. The relatively shallow depth of the carotid artery and plaque enables non-invasive evaluation of carotid plaque utilizing high frequency linear-array transducers. We investigate the ability of the attenuation coefficient and equivalent scatterer size parameters to differentiate between calcified, and lipidic plaque tissue. Softer plaques especially lipid rich and those with a thin fibrous cap are more prone to rupture and can be classified as unstable or vulnerable plaque. Preliminary results were obtained from 10 human patients whose carotid artery was scanned in vivo to evaluate atherosclerotic plaque prior to a carotid endarterectomy procedure. Our results indicate that the equivalent scatterer size obtained using Faran's scattering theory for calcified regions are in the 120-180 microm range while softer regions have larger equivalent scatterer size distribution in the 280-470 microm range. The attenuation coefficient for calcified regions as expected is significantly higher than that for softer regions. In the frequency bandwidth ranging from 2.5 to 7.5 MHz, the attenuation coefficient for calcified regions lies between 1.4 and 2.5 dB/cm/MHz, while that for softer regions lies between 0.3 and 1.3 dB/cm/MHz.

Effort angina in a patient with advanced coronary artery disease. Role played by coronary angiography, Ivus and cardiac CT: case report

Coronary angiography is considered to be the gold standard technique for assessing the severity of obstructive luminal narrowing; however, in a few circumstances it may be misleading. In these cases, cardiac computed tomography (CT) and intravascular ultrasound (IVUS) may help to give a correct interpretation.

In this report, we describe the case of a 62-year-old man whose effort angina was first evaluated with coronary angiography, but whose severe stenosis of the right coronary artery was only observed on cardiac CT and IVUS. This additional diagnosis promptly resulted in a therapeutic approach with percutaneous transluminal coronary angioplasty (PTCA).

Tissue characterization of coronary plaques: comparison of integrated backscatter intravascular ultrasound with virtual histology intravascular ultrasound

BACKGROUND

Integrated backscatter (IB) intravascular ultrasound (IVUS) and IVUS Virtual Histology (VH) have been developed for tissue characterization, but have never been compared directly. The purpose of this study was to compare the overall agreement between IB-IVUS and IVUS-VH in the tissue characterization of plaques from the same coronary arterial cross-section.

METHODS AND RESULTS

Images were acquired from 46 coronary arteries from 25 cadavers. Of a total of 392 histology/IVUS image pairs, 152 pairs were diagnosed as Stary's type III, IV, Va, Vb and Vc, and compared for IB-IVUS, IVUS-VH and histology. In the qualitative comparison, the overall agreement between histological and IB-IVUS diagnoses was higher (kappa = 0.81, 95% confidence interval (CI): 0.74-0.89) than that of the IVUS-VH diagnoses (kappa = 0.66, 95%CI: 0.56-0.75). The % fibrosis area determined by IB-IVUS was significantly correlated with the relative area of fibrosis based on histology (r = 0.67, p < 0.001). In the quantitative comparison, the overall agreement between the histological and IB-IVUS diagnoses was higher (kappa = 0.83, 95% CI: 0.75-0.91) than that of the IVUS-VH diagnoses (kappa = 0.73, 95% CI: 0.63-0.83).

CONCLUSION

Based on histology as the gold standard, IB-IVUS provided higher diagnostic accuracy than IVUS-VH for tissue characterization of coronary plaques.

Impact of vascular remodeling on the coronary plaque compositions: an investigation with in vivo tissue characterization using integrated backscatter-intravascular ultrasound

Recent studies have indicated that positive remodeling is strongly associated with development of acute coronary syndrome (ACS). The aim of this study was to compare plaque composition of vascular remodeling patterns by an established in vivo tissue characterization method using integrated backscatter (IB)-intravascular ultrasound (IVUS). The study population consisted of 41 consecutive patients who received IVUS prior to percutaneous coronary intervention. Remodeling index (RI) was calculated as the external elastic membrane (EEM) area at the minimal lumen area (MLA) site divided by average EEM area at the proximal and distal reference sites. The patients were divided into two groups based on RI: positive remodeling (PR) defined as RI>1 and non-PR as RI<or=1. A total of 21 areas centered at MLA per lesion site were evaluated by IB-IVUS at 1mm intervals. The occupancy rate of four tissue types within atherosclerotic plaques was compared between the two groups. Percent lipid volume in the PR group (n=20) was significantly greater than the non-PR group (n=21) (40.5+/-14.8% vs. 26.4+/-15.9%, p<0.001). In contrast, % fibrous volume in the PR group was significantly lower than the non-PR group (49.9+/-9.4% vs. 56.1+/-9.6%, p=0.042). Percent dense fibrous volume and % calcified volume were slightly but significantly lower in the PR group compared with the non-PR group (dense fibrous: 6.8+/-5.0% vs. 11.6+/-8.4%, p=0.034, calcified: 2.6+/-2.0% vs. 5.1+/-4.4%, p=0.026). In conclusions, PR lesions contain more lipid-rich and less hard plaque components compared with non-PR lesions, which may account for the higher incidence of ACS and plaque vulnerability.

Distribution of ultrasonic radiofrequency signal amplitude detects lipids in atherosclerotic plaque of coronary arteries: an ex-vivo study

BACKGROUND

Accumulation of lipids within coronary plaques is an important process in disease progression. However, gray-scale intravascular ultrasound images cannot detect plaque lipids effectively. Radiofrequency signal analysis could provide more accurate information on preclinical coronary plaques.

METHODS

We analyzed 29 zones of mild atheroma in human coronary arteries acquired at autopsy. Two histologic groups, i.e., plaques with a lipid core (group L) and plaques without a lipid core (group N), were analyzed by automatic calculation of integrated backscatter. One hundred regions of interest were set on the target zone. Radiofrequency signals from a 50 MHz transducer were digitized at 240 MHz with 12-bit resolution. The intensity of integrated backscatter and its distribution within each plaque were compared between the two groups.

RESULTS

Although the mean backscatter was similar between the groups, intraplaque variation of backscatter and backscatter in the axial direction were larger in group L than in group N (p = 0.02). Conventional intravascular ultrasound showed extremely low sensitivity for lipid detection, despite a high specificity. In contrast, a cut-off value>32 for the total variance of integrated backscatter identified lipid-containing plaque with a high sensitivity (85%) and specificity (75%).

CONCLUSION

Compared with conventional imaging, assessment of the intraplaque distribution of integrated backscatter is more effective for detecting lipid. As coronary atheroma progresses, its composition becomes heterogeneous and multi-layered. This radiofrequency technique can portray complex plaque histology and can detect the early stage of plaque progression.

Randomized evaluation of atorvastatin in patients with coronary heart disease: a serial intravascular ultrasound study

BACKGROUND

It is unclear whether a marked reduction of low-density lipoprotein-cholesterol (LDL-C) in patients with coronary heart disease (CHD) and mild hypercholesterolemia leads to less progression of atherosclerosis.

METHODS AND RESULTS

Patients with CHD and hypercholesterolemia (100<LDL-C<140 mg/dl) who underwent coronary angiography (CAG) and intravascular ultrasound (IVUS) were randomly assigned to the atorvastatin (10-20 mg/day) group or ;usual care' group. After 12 months 58 patients had follow-up CAG and IVUS studies that could be evaluated. Cross-sectional areas of the vessel, lumen, and plaque were measured at 1-mm intervals, and volumetric calculations were based on Simpson's rule. After 12 months, the mean reduction of LDL-C was 34% in the atorvastatin group and 0% in the usual care group (p<0.01). The mean absolute plaque volume showed a larger increase in the usual care group than in the atorvastatin group (atorvastatin -1.4+/-11.6 mm3, usual care 7.6+/-10.3 mm3; p<0.01). Vessel volume also showed a larger increase in the usual care group than in the atorvastatin group (atorvastatin 2.2+/-10.9 mm3, usual care 10.9+/-17.7 mm3; p=0.03).

CONCLUSIONS

Atorvastatin treatment prevented the further progression of atherosclerosis by maintaining LDL-C below 100 mg/dl in patients with CHD and hypercholesterolemia (100<LDL-C<140 mg/dl).

Impact of lipid-lowering therapy with pitavastatin, a new HMG-CoA reductase inhibitor, on regression of coronary atherosclerotic plaque

BACKGROUND

Recent lipid-lowering trials have reported that statin therapy may retard progression or stimulate regression of human coronary plaque. In the present study volumetric intravascular ultrasound (IVUS) analyses were performed to investigate the effect of pitavastatin, a newly developed statin, on regression of human coronary plaque.

METHODS AND RESULTS

Eighty-two patients matched for age and gender from 870 consecutive patients undergoing IVUS guided percutaneous coronary intervention were retrospectively assigned to either lipid-lowering therapy (n=41; pitavastatin 2 mg/day) or control group (n=41; diet only). Serial volumetric IVUS analyses of a matched left main coronary arterial site were performed. A significant reduction in low-density lipoprotein-cholesterol (LDL-C) level of 33.2% (p<0.001) was observed in the pitavastatin group. Plaque volume index (PVI) was significantly reduced in the pitavastatin group (10.6+/-9.4% decrease) compared with the control group (8.1+/-14.0% increase, p<0.001). There were positive correlations between the percent change in the PVI and follow-up LDL-C level (r=0.500, p<0.001) and the percent change in LDL-C level (r=0.479, p<0.001).

CONCLUSION

Lipid-lowering therapy with pitavastatin induced significant coronary plaque regression, associated with a significant reduction in the LDL-C level. The percent change in the PVI showed a significant positive correlation with the percent change in LDL-C level.

Transient electrocardiographic recording of acute myocardial ischemia with ST-segment elevation of the diaphragmal location accompanied by a total atrioventricular block as an initial manifestation of Prinzmetal’s angina — A case report

Prinzmetal’s angina, also known as Prinzmetal’s variant or Prinzmetal’s vasospastic angina is characterized by angina attacks caused by spasm of the great epicardial coronary arteries. Coronary artery endothelial dysfunction plays a crucial role in the development of this vasospastic angina. The attacks of vasospastic angina can be prevented with calcium antagonists and nitrates, whereas in refractory variant angina, coronary angioplasty with stenting may help prevent further coronary spasm. In this case report, we present a 52-year-old male patient with a transient electrocardiographic recording of acute myocardial ischemia with ST-segment elevation of the diaphragmal location accompanied by a total atrioventricular block immediately after exercise testing and as a first manifestation of Prinzmetal’s angina. After regression of the symptoms and electrocardiographic changes, significant pathomorphologic changes of coronary arteries were excluded by coronary angiography. Following discharge, the patient was treated with calcium antagonists and did not show symptoms during a 4-year follow-up period.

Assessment of vulnerable plaques causing acute coronary syndrome using integrated backscatter intravascular ultrasound

OBJECTIVES

This study aims to define tissue characteristics of vulnerable plaques before acute coronary syndrome (ACS) by use of integrated backscatter intravascular ultrasound (IB-IVUS).

BACKGROUND

Tissue characterization of coronary plaques is possible with the use of IB-IVUS.

METHODS

The subjects were 140 patients with angina pectoris, and we selected 160 coronary lesions without significant stenosis for evaluation. Ultrasound signals were obtained by an IVUS system using a 40-MHz catheter.

RESULTS

At the follow-up (30 +/- 7 months), 12 plaques caused ACS after the initial IVUS examination. Ten of the 12 plaques had IVUS parameters recorded at baseline. These 10 plaques were classified as vulnerable plaques (VP), and the other plaques were classified as stable plaques (SP; n = 143). There was no significant difference of vessel area, lumen area, and plaque area between VP and SP. However, plaque burden (60 +/- 9% vs. 52 +/- 9%; p = 0.014), eccentricity (0.70 +/- 0.10 vs. 0.55 +/- 0.17; p = 0.013), remodeling index (1.30 +/- 0.08 vs. 1.16 +/- 0.16; p = 0.006) and percentage lipid area (72 +/- 10% vs. 50 +/- 16%; p < 0.0001) were greater in VP than in SP. Percentage fibrous area (23 +/- 6% vs. 47 +/- 14%; p < 0.0001) was smaller in VP than in SP. The sensitivities, specificities, and positive predictive values of percentage fibrous area (90%, 96%, and 69%, respectively) and percentage lipid area (80%, 90%, and 42%, respectively) for classifying VP were evaluated.

CONCLUSIONS

Tissue characteristics of VP before ACS were different from those of SP. This suggests that VP and SP as classified by IB-IVUS are useful in predicting ACS.