Quantification of Coronary Calcification by Intravascular Ultrasound Do Calcium Deposits With Larger Arcs Have Longer Lengths?

Calcification in Atherosclerotic Plaque Vulnerability: Friend or Foe?

Calcification is a clinical marker of atherosclerosis. This review focuses on recent findings on the association between calcification and plaque vulnerability. Calcified plaques have traditionally been regarded as stable atheromas, those causing stenosis may be more stable than non-calcified plaques. With the advances in intravascular imaging technology, the detection of the calcification and its surrounding plaque components have evolved. Microcalcifications and spotty calcifications represent an active stage of vascular calcification correlated with inflammation, whereas the degree of plaque calcification is strongly inversely related to macrophage infiltration. Asymptomatic patients have a higher content of plaque calcification than that in symptomatic patients. The effect of calcification might be biphasic. Plaque rupture has been shown to correlate positively with the number of spotty calcifications, and inversely with the number of large calcifications. There may be certain stages of calcium deposition that may be more atherogenic. Moreover, superficial calcifications are independently associated with plaque rupture and intraplaque hemorrhage, which may be due to the concentrated and asymmetrical distribution of biological stress in plaques. Conclusively, calcification of differential amounts, sizes, shapes, and positions may play differential roles in plaque homeostasis. The surrounding environments around the calcification within plaques also have impacts on plaque homeostasis. The interactive effects of these important factors of calcifications and plaques still await further study.

New insights into spotty calcification and plaque rupture in acute coronary syndrome: an optical coherence tomography study

Although recent optical coherence tomography (OCT) studies have focused on spotty calcification, whether there were any characteristics in the concomitant existence of calcification and plaque rupture remains unknown. The aim of the present study was to investigate the characteristics of spotty calcification in acute coronary syndrome (ACS) patients with or without plaque rupture, using OCT. This study enrolled 98 consecutive patients with ACS. OCT image acquisitions were performed in the culprit lesions, and patients were divided into the plaque rupture group (n = 38) and the non-rupture group (n = 60). The frequency of spotty calcification (p = 0.006), thin-capped fibroatheroma (p = 0.012), macrophage infiltration (p = 0.022), and the number of spotty calcification per patient (p < 0.001) were significantly higher and the largest arc and the minimum depth of spotty calcification from the luminal surface were significantly smaller in the rupture group. Moreover, in the rupture group, most of the spotty calcifications in the site nearest to the minimum lumen area were observed in the proximal portion of that site, and tended to be located near the plaque rupture. Multivariate analysis revealed that the presence of spotty calcification (OR 3.19, 95 % CI 1.12-9.76, p = 0.030) and age (OR 1.08, 95 % CI 1.02-1.14, p = 0.008) were independent predictive factors for plaque rupture. This study demonstrates the characteristics of spotty calcification in ACS patients with plaque rupture and the positional relationship between spotty calcification and plaque rupture. These detailed observations could impact on treatment strategies for the prevention of ACS.

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 artery calcification as a new predictor of non-target lesion revascularization during the chronic phase after successful percutaneous coronary intervention

In the drug-eluting stent era, the outcome of patients undergoing percutaneous coronary intervention (PCI) has remarkably improved. Nevertheless, non-target lesion revascularization (non-TLR) is often performed even after successful PCI and optimized medical therapy. This study aimed to determine the predictor of non-TLR. In all, 125 consecutive patients with stable angina pectoris underwent intravascular ultrasound (IVUS)-guided PCI and were followed up for 3.3 ± 0.5 years. We performed oral glucose-tolerance tests in patients with no history of known diabetes mellitus (DM) to investigate glucose tolerance. To evaluate the severity of coronary artery calcification (CAC), we calculated CAC score by multiplying the arc (degree) with the length (mm) of the superficial calcium deposit detected by IVUS. Fourteen patients underwent non-TLR (non-TLR group); the remaining 111 did not (reference group). Glycosylated hemoglobin (HbA1c; %) and prevalence of known DM were similar in both groups, but the non-TLR group had higher fasting blood glucose (103 ± 16 vs. 94 ± 11 mg/dl, p = 0.04) and blood glucose (196 ± 60 vs. 149 ± 48 μU/ml, p = 0.01) and insulin at 2 h (184 ± 241 vs. 67 ± 49 μU/ml, p < 0.01) than did the reference group. CAC score was significantly higher in the non-TLR group (788 ± 585 vs. 403 ± 466, p = 0.01). Multiple logistic analysis indicated that CAC score is an independent predictor of non-TLR (p = 0.008). Non-TLR-free rate was significantly higher for patients with CAC score ≥400 than for those with CAC score <400 (p = 0.01). Non-TLR is associated with abnormal glucose tolerance and CAC score; CAC score is an independent predictor of non-TLR. Secondary prevention is especially important in patients with high CAC scores.

Relationship between coronary artery calcium score by multidetector computed tomography and plaque components by virtual histology intravascular ultrasound

The aim of this study was to evaluate the relationship between coronary artery calcium score (CACS) assessed by multidetector computed tomography (MDCT) and plaque components assessed by virtual histology-intravascular ultrasound (VH-IVUS) in 172 coronary artery disease (CAD) patients with 250 coronary lesions. CACS was assessed according to Agatston scoring method by MDCT and patients were divided into four groups: Group I (CACS = 0 [n = 52]); Group II (CACS = 1-100 [n = 99]); Group III (CACS = 101-400 [n = 84]); and Group IV (CACS > 400 [n = 15]). Total atheroma volume was greatest in Group IV (152 ± 132 µL vs 171 ± 114 µL vs 195 ± 149 µL vs 321±182 µL, P < 0.001). The absolute dense calcium (DC) and necrotic core (NC) volumes were greatest, and relative DC volume was greatest in Group IV (5.5 ± 6.6 µL vs 11.0 ± 10.3 µL vs 15.6 ± 13.6 µL vs 36.6 ± 18.2 µL, P < 0.001, and 14.8 ± 18.2 µL vs 19.5 ± 18.9 µL vs 22.5 ± 19.1 µL vs 41.7 ± 27.9 µL, P < 0.001, and 6.4 ± 5.3% vs 11.0 ± 6.2% vs 14.0 ± 6.5% vs 20.0 ± 7.8%, P < 0.001, respectively). The absolute plaque and DC and NC volumes and the relative DC volume correlated positively with calcium score. CAD patients with high calcium score have more vulnerable plaque components (greater DC and NC-containing plaques) than those with low calcium score.

The predictive value of computed tomography calcium scores: a comparison with quantitative volumetric intravascular ultrasound

OBJECTIVE

To evaluate the relationship between coronary artery calcium scoring (CACS) and intravascular ultrasound (IVUS) calcification and disease severity.

METHODS

Forty-five angina patients who underwent CACS 18+/-23 days before IVUS were studied. The CACS was recorded for each lesion matched to a specific IVUS lesion. Cross-sectional area measurements of the external elastic membrane, lumen area, plaque and media, and plaque burden were performed. The arc and length of calcification were measured.

RESULTS

There were 106 calcified lesions detected by IVUS. Eighty-five of those lesions (80%) were detected by CACS, but 21 calcified lesions (20%) were missed. Fourteen (50%) out of 28 of the lesions with an IVUS-calcium arc below the 25th percentile (51.4 degrees ) were detected by CACS vs. 91% of lesions with an IVUS-calcium arc >51.4 degrees (P<.05). Similarly, 21 (58%) of 36 lesions <or=3 mm in length were detected vs. 91% of lesions >3 mm (P<.05). We divided IVUS-calcified lesions into CACS <or=10 and >10. Mean plaque burden, calcified length, and arc of calcium increased significantly, while minimum lumen area decreased with increasing CACS. There was the same tendency in culprit and nonculprit calcified lesions, respectively. Multivariate analysis showed a calcified length (regression coefficient=8.718, 95% CI 4.668-12.77, P<.001) and an arc of calcium (regression coefficient=2.789, 95% CI 1.419-4.119, P<.001) were significant predictors for CACS.

CONCLUSIONS

This study suggests that a CACS could evaluate coronary calcium burden noninvasively through the accurate estimation of calcium-arc and length.

The role of inflammation in coronary artery calcification

Vascular calcification is an age-dependent, common finding in human coronary arteries and begins as early as the second decade of life, just after fatty streak formation. Previous studies have showed that the severity of coronary calcification is closely related to atherosclerotic plaque burden and cardiac event rate. In the past few decades, coronary calcification has been considered passive and degenerative. With recent clinical and basic research, however, there is increasing recognition that coronary calcification is an active, regulated process. Current diagnostic methods for coronary artery calcification (CAC) are usually traditional coronary angiography, intravascular ultrasound (IVUS), electron beam computed tomography (EBCT) and multi-slice computed tomography (MSCT) while treatment for patients with calcified coronary arteries is troublesome. Several lines of evidence suggest that inflammation plays a major role in the development of atherosclerosis as well as its clinical manifestations. Recent study showed that inflammatory process might be also involved in coronary calcification. Accordingly, measurements of inflammatory markers such as C-reactive protein (CRP) may in part reflect indices of atherosclerosis, such as coronary calcification, and are likely to provide distinct information regarding cardiovascular risk. In this article, we review the current evidence of relationship between coronary calcification and inflammation for purpose of drawing the more attention on the inflammatory mechanism of coronary calcification, which may change our research as well as therapeutic strategies for coronary calcification in the future.