Role of calcified spots detected by intravascular ultrasound in patients with ST-segment elevation acute myocardial infarction

The Impact of Coronary Artery Calcification on Long-Term Cardiovascular Outcomes

Decades of research and experimental studies have investigated various strategies to prevent acute coronary events. However, significantly efficient preventive methods have not been developed and still remains a challenge to determine if a coronary atherosclerotic plaque will become vulnerable and unstable. This review aims to assess the significance of plaque vulnerability markers, more precisely the role of spotty calcifications in the development of major cardiac events, given that coronary calcification is a hallmark of atherosclerosis. Recent studies have suggested that microcalcifications, spotty calcifications, and the presence of the napkin-ring sign are predictive vulnerable plaque features, and their presence may cause plaque instability.

Shape-based approach for coronary calcium lesion volume measurement on intravascular ultrasound imaging and its association with carotid intima-media thickness

OBJECTIVES

Coronary calcification plays an important role in diagnostic classification of lesion subsets. According to histopathologic studies, vulnerable atherosclerotic plaque contains calcified deposits, and there can be considerable variation in the extent and degree of calcification. Intravascular ultrasound (IVUS) has demonstrated its role in imaging coronary arteries, thereby displaying calcium lesions. The aim of this work was to develop a fully automated system for detection, area and volume measurement, and characterization of the largest calcium deposits in coronary arteries. Furthermore, we demonstrate the correlation between the coronary calcium IVUS volume and the neurologic risk biomarker B-mode carotid intima-media thickness (IMT).

METHODS

Our system automatically detects the frames with calcium, identifies the largest calcium region, and performs shape-based volume measurements. The carotid IMT is measured by using AtheroEdge software (AtheroPoint, LLC) on B-mode ultrasound imaging.

RESULTS

Our database consists of low-contrast IVUS videos and corresponding B-mode images from 100 patients. Our experiments showed that the correlation between calcium volumes and carotid IMT was higher for the left carotid artery compared to the right carotid artery (r = 0.066 for the left carotid artery and 0.121 for the right carotid artery). We obtained 97% accuracy for automated calcium detection compared against the scoring given by our expert radiologists. Furthermore, we benchmarked shape-based volume measurement against the conventional method, which used integration of regions and showed a correlation of 84%.

CONCLUSIONS

Since carotid IMT is an independent prognostic factor for myocardial infarction, and calcium lesions are correlated with stroke risk, we believe that this automated system for calcium volume measurement could be useful for assessing patients' cardiovascular risk.

Coronary CT angiography in the quantitative assessment of coronary plaques

Coronary computed tomography angiography (CCTA) has been recently evaluated for its ability to assess coronary plaque characteristics, including plaque composition. Identification of the relationship between plaque composition by CCTA and patient clinical presentations may provide insight into the pathophysiology of coronary artery plaque, thus assisting identification of vulnerable plaques which are associated with the development of acute coronary syndrome. CCTA-generated 3D visualizations allow evaluation of both coronary lesions and lumen changes, which are considered to enhance the diagnostic performance of CCTA. The purpose of this review is to discuss the recent developments that have occurred in the field of CCTA with regard to its diagnostic accuracy in the quantitative assessment of coronary plaques, with a focus on the characterization of plaque components and identification of vulnerable plaques.

Comprehensive assessment of spotty calcifications on computed tomography angiography: comparison to plaque characteristics on intravascular ultrasound with radiofrequency backscatter analysis

BACKGROUND

The purpose of the study was to systematically compare calcification patterns in plaques on computed tomography angiography (CTA) with plaque characteristics on intravascular ultrasound with radiofrequency backscatter analysis (IVUS-VH).

METHODS AND RESULTS

In total, 108 patients underwent CTA and IVUS-VH. On CTA, calcification patterns in plaques were classified as non-calcified, spotty or dense calcifications. Plaques with spotty calcifications were differentiated into small spotty (<1 mm), intermediate spotty (1-3 mm) and large spotty calcifications (≥3 mm). Plaque characteristics deemed more high-risk on IVUS-VH were defined by % necrotic core (NC) and presence of thin cap fibroatheroma (TCFA). Overall, 300 plaques were identified both on CTA and IVUS-VH. % NC core was significantly higher in plaques with small spotty calcifications as compared to non-calcified plaques (20% vs 13%, P = .006). In addition, there was a trend for a higher % NC in plaques with small spotty calcifications than in plaques with intermediate spotty calcifications (20% vs 14%, P = .053). Plaques with small spotty calcifications had the highest % TCFA as compared to large spotty and dense calcifications (31% vs 9% and 31% vs 6%, P < .05).

CONCLUSION

Plaques with small spotty calcifications on CTA were related to plaque characteristics deemed more high-risk on IVUS-VH. Therefore, CTA may be valuable in the assessment of the vulnerable plaque.

Effect of renal function on ultrasonic coronary plaque characteristics in patients with acute myocardial infarction

We used intravascular ultrasonography to assess plaque morphology and morphometry in 310 patients with acute myocardial infarction (125 with ST-segment elevation and 185 with non-ST-segment elevation myocardial infarction) with varying degrees of renal dysfunction according to the creatinine clearance (CrCl): CrCl >70 ml/min in 153, CrCl of 30 to 69 ml/min in 103, and CrCl of <30 ml/min in 54 patients, including 20 patients requiring dialysis). The lesion site plaque burden was greatest (77.4 +/- 11.0% vs 79.8 +/- 12.5% vs 82.0 +/- 10.3%, p = 0.031) and the lesion was longest (20.9 +/- 9.1 vs 23.1 +/- 9.5 vs 26.3 +/- 9.6 mm, p = 0.038) in the lowest CrCl group. Infarct-related artery plaque rupture (31.4% vs 34.0% vs 53.7%, p = 0.011) and multiple plaque ruptures (11.1% vs 12.6% vs 33.3%, p <0.001) were the most common, the ruptured plaque cavities were the largest (1.98 +/- 0.89 vs 2.20 +/- 1.45 vs 3.06 +/- 1.70 mm(2), p = 0.002), and the ruptured plaque was longest (2.33 +/- 0.93 vs 2.59 +/- 1.50 vs 3.33 +/- 1.76 mm, p = 0.008) in the lowest CrCl group (<30 ml/min). Intravascular ultrasound-detected thrombus was observed most frequently in the lowest CrCl group (22.9% vs 23.3% vs 40.7%, p = 0.027). CrCl was the one of the independent predictors of culprit lesion plaque rupture (odds ratio 0.979, 95% confidence interval 0.963 to 0.994, p = 0.008). During 1 year of follow-up, the incidence of nonfatal myocardial infarction (2.6% vs 4.9% vs 11.1%, p = 0.044) and cardiac death (3.9% vs 6.8% vs 14.8%, p = 0.024) was greatest in the lowest CrCl group. Also, a strong trend was found toward the greatest incidence of stent thrombosis (2.0% vs 3.9% vs 9.3%, p = 0.057) in the lowest CrCl group. In conclusion, patients with acute myocardial infarction and significant renal dysfunction had more plaque vulnerability compared to those with normal renal function. This might be associated with poor clinical outcomes in patients with acute myocardial infarction and renal dysfunction.

Automatic segmentation of calcifications in intravascular ultrasound images using snakes and the contourlet transform

It is valuable to detect calcifications in intravascular ultrasound images for studies of coronary artery diseases. An image segmentation method based on snakes and the Contourlet transform is proposed to automatically and accurately detect calcifications. With the Contourlet transform, an original image is decomposed into low-pass bands and band-pass directional sub-bands. The 2-D Renyi's entropy is used to adaptively threshold the low-pass bands in a multiresolution hierarchy to determine regions-of-interest (ROIs). Then a mean intensity ratio, reflecting acoustic shadowing, is presented to classify calcifications from noncalcifications and obtain initial contours of calcifications. The anisotropic diffusion is used in bandpass directional sub-bands to suppress noise and preserve calcific edges. Finally, the contour deformation in the boundary vector field is used to obtain final contours of calcifications. The method was evaluated via 60 simulated images and 86 in vivo images. It outperformed a recently proposed method, the Santos Filho method, by 2.76% and 14.53%, in terms of the sensitivity and specificity of calcification detection, respectively. The area under the receiver operating characteristic curve increased by 0.041. The relative mean distance error, relative difference degree, relative arc difference, relative thickness difference and relative length difference were reduced by 5.73%, 19.79%, 11.62%, 12.06% and 20.51%, respectively. These results reveal that the proposed method can automatically and accurately detect calcifications and delineate their boundaries. (E-mail: yywang@fudan.edu.cn).

Key Issues in the Developing Synergism between Cardiovascular Imaging and Biomarkers

Background: Sophisticated methods of cardiac imaging have the potential to revolutionize the care of patients with cardiovascular disease. The benefits of these state-of-the art imaging techniques can be enhanced by their use in combination with new cardiac biomarkers. This review addresses potentially useful interactions between imaging and biomarkers.

Content: Areas were defined in which the combined use of novel imaging techniques and biomarkers would be most beneficial. This review addresses multiple cardiovascular conditions for which the useful aspects of imaging and biomarkers are likely to be positively synergistic, including acute and chronic ischemic heart disease, heart failure, myocarditis, hypertension, and atherosclerosis.

Conclusions: The synergistic use of imaging techniques and biomarkers will enhance the investigation of many key issues and questions and will be an important resource in the future.