Computed tomographic angiography characteristics of atherosclerotic plaques subsequently resulting in acute coronary syndrome

Association between epicardial adipose tissue volume and characteristics of non-calcified plaques assessed by coronary computed tomographic angiography

BACKGROUND

The aim of this study was to investigate whether high epicardial adipose tissue (EAT) volume is related to the presence of vulnerable coronary plaque components as assessed by computed tomography (CT).

METHODS

We evaluated 357 patients referred for 64-slice CT, and assessed coronary plaque components and EAT volume. Vulnerable coronary plaque components were defined as the presence of non-calcified plaque (NCP), including low-density plaque (LDP: <39 HU) and positive remodeling (PR: remodeling index>1.05). In accordance with a previous report, patients were assigned to two groups: low (<100 ml) or high (≥100 ml) EAT volume.

RESULTS

Compared to the low EAT volume group, the high EAT volume group had a higher prevalence of NCP (74% vs. 59%, p=0.003). Additionally, the high EAT volume group had a higher prevalence of LDP with PR than the low EAT volume group (46% vs. 25%, p<0.001). Interestingly, a high EAT volume was an independent predictor of LDP with PR (odds ratio 2.56, 95% confidence interval 1.38-4.85, p=0.003) after adjusting for age, gender, traditional cardiovascular risk factors, body mass index (BMI), abdominal visceral adipose tissue (VAT), and coronary artery calcium (CAC) scores.

CONCLUSIONS

A high EAT volume was associated with the presence of vulnerable plaque components, independent of obesity measurements (BMI and VAT) and CAC scores.

Comparison of in vivo assessment of vulnerable plaque by 64-slice multislice computed tomography versus optical coherence tomography

The aim of this study was to investigate the possibility of 64-slice multislice computed tomography (MSCT) to detect vulnerable plaque derived by optical coherence tomography. From September 2007 through December 2009, 122 lesions in 81 patients were evaluated by 64-slice MSCT and optical coherence tomography. Based on optical coherence tomographic findings, lesions were classified as thin-capped fibroatheroma (TCFA; n=37) and non-TCFA (n=85). Mean computed tomographic density value of the lesion was lower and remodeling index was larger in the TCFA group (44.9 ± 19.2 vs 78.7 ± 25.0 HU, p <0.0001; 1.14 ± 0.20 vs 0.95 ± 0.16, p<0.0001, respectively). Mean computed tomographic density value was correlated and remodeling index was inversely correlated with fibrous cap thickness (r=0.605, p<0.0001; r=-0.591, p<0.0001, respectively). Optimal threshold of mean computed tomographic value and remodeling index identified by receiver operating characteristic curve were 62.4 HU and 1.08 (area under the curve 0.859 and 0.781). Signet ringlike appearance was observed more frequently in the TCFA group (65% vs 16%, p<0.0001). In multivariate analysis, independent predictors of TCFA were mean computed tomographic density value ≤62.4 HU (odds ratio 8.20, 95% confidential interval 2.49 to 27.0, p=0.0005), remodeling index ≥1.08 (odds ratio 6.10, 95% confidential interval 2.04 to 18.2, p=0.0012), and signet ringlike appearance (odds ratio 6.33, 95% confidential interval 2.03 to 19.7, p=0.0014). In conclusion, based on comparisons with optical coherence tomographic findings, 64-slice MSCT may have the potential to detect vulnerable plaque.

[Cardiac hybrid imaging]

CT coronary angiography and myocardial perfusion scintigraphy are both established noninvasive techniques for the diagnosis of coronary artery disease (CAD). Cardiac hybrid imaging consists of the combination (or fusion) of both modalities and allows obtaining complementary morphological (coronary anatomy, stenoses) and functional (myocardial perfusion) information in a single image. The increased availability of these techniques in clinical practice has also raised a controversy with regard to which patients should undergo such integrated examinations. The feasibility and clinical value of hybrid imaging has been documented in small cohort studies and selected series of patients. The incremental value of the hybrid technique arises from the spatial co-registration of perfusion defects with coronary stenoses. This allows an assessment of the hemodynamic relevance of coronary stenoses and the determination of the need for revascularization procedures in each individual artery. Thus, it can be anticipated that the ongoing efforts to reduce radiation exposure and the increasing clinical interest will further pave the way for an ever-increasing use of cardiac hybrid imaging in clinical practice.

CT evaluation of vulnerable plaque: noninvasive fortune-telling?

Recently, cardiac CTA has been proposed as a promising noninvasive tool for identification of rupture-prone plaques prior to a subsequent coronary event. This task is particularly challenging but the reward is high: identification of high-risk lesions could preclude plaque thrombosis and possibly prevent acute coronary syndromes. We present a case of a borderline mixed plaque with positive remodeling in the proximal left anterior descending artery (LAD). After 6 months and despite aggressive medical therapy, the patient developed acute ST-elevation myocardial infarction caused by a thrombotic lesion in the proximal LAD. We review the literature on CT characteristics of vulnerable plaque and discuss the possible preventive interventions.

Prevalence of computed tomographic angiography-verified high-risk plaques and significant luminal stenosis in patients with zero coronary calcium score

BACKGROUND

Some patients were detected with coronary artery disease even if the coronary artery calcium score was (CACS)=0. We evaluated the prevalence and predictor of significant stenosis and computed tomography (CT) based vulnerable plaque (CTVP) for patients with CACS=0.

METHODS

Subjects were 2160 patients (M/F=1110/1050, 64.7 ± 11.6 years) who underwent measurement of calcium score and CT coronary angiography. As for CACS=0 group, age, gender, coronary risk factor (family history (FH), hypertension (HT), hyperlipidemia (HL), diabetes (DM), and smoking), body mass index, history of cerebral infarction, the presence of chest symptom, and abnormal rest ECG findings were investigated as predictors for significant stenosis and CTVP by multivariate analysis using logistic regression analysis.

RESULTS

Out of 2160 patients, 1141 (52.8%, M/F=655/486, 68.4 ± 9.8 years) were of CACS>0 and 1019 (47.2%, M/F=455/564, 60.5 ± 12.0 years) were of CACS=0. In the CACS=0 group, 24 patients (2.4%) were found with significant stenosis and 47 (4.6%) with 2FPP. In 104 patients with spotty calcification (10.2%), 10 (9.6%) out of these 104 had significant stenosis and also had CTVP. Multivariate analysis using logistic regression analysis revealed significant predictor for significant stenosis to be only male (Odds ratio (OR): 3.075, 95%CI 1.166-8.109, p=0.0232) and significant predictor for CTVP to be age (OR: 1.032, 95%CI 1.001-1.063, p=0.0437) and male (OR: 2.386, 95%CI 1.193-4.775, p=0.0140).

CONCLUSIONS

The present study suggests that the presence of CTVP must be noted, when patients are male and elderly even if CACS=0 and the presence of spotty calcification increases the prevalence of significant stenosis and CTVP in patients with CACS=0.

Association between high-sensitivity C-reactive protein and coronary plaque subtypes assessed by 64-slice coronary computed tomography angiography in an asymptomatic population

BACKGROUND

Elevated levels of C-reactive protein (CRP) are associated with poor cardiovascular outcomes, even after accounting for traditional cardiovascular risk factors. We sought to analyze the relationship between levels of CRP and coronary plaque subtypes as assessed by coronary computed tomography angiography.

METHODS AND RESULTS

We evaluated 1004 asymptomatic South Korean subjects (mean age, 49±9.3 years) who underwent coronary computed tomography angiography as part of a health screening evaluation. We examined the association between increasing CRP levels and plaque subtypes using multivariable linear and logistic regression analysis. Coronary plaque was observed in 211 of 1004 individuals (21%). Subjects with high CRP (≥2 mg/L) had an increased prevalence of any plaque type (30.7% versus 16.7% P<0.001) and mixed calcified arterial plaque (MCAP) (19.3% versus 6.3% P<0.001) as compared with subjects with low-normal CRP. Multivariable logistic regression analysis demonstrated that elevated CRP predicted the presence of any MCAP (high versus low-normal CRP group; odds ratio, 2.81; 95% confidence interval, 1.62 to 4.89). When examining the multivariable logistic regression analysis between the presence of ≥2 plaques and CRP, subjects with high CRP were more likely to have MCAP than those with low-normal CRP levels (odds ratio, 3.78; 95% confidence interval, 1.49 to 9.55).

CONCLUSIONS

Elevated levels of CRP are associated with an increased prevalence of MCAP as assessed by coronary computed tomography angiography. Longitudinal studies will determine if the excess risk observed in persons with elevated CRP may be mediated, at least in part, by an increased burden of MCAP.

Cardiac hybrid imaging

Computed tomography coronary angiography (CTCA) and myocardial perfusion imaging techniques (single photon emission computed tomography, SPECT, or positron emission tomography, PET) are established non-invasive modalities for the diagnosis of coronary artery disease (CAD). Cardiac hybrid imaging consists of the combination (or 'fusion') of both modalities and allows obtaining complementary morphological (coronary anatomy, stenoses) and functional (myocardial perfusion) information in a single setting. However, hybrid cardiac imaging has also generated controversy with regard to which patients should undergo such integrated examinations for clinical effectiveness and minimization of costs and radiation dose. The feasibility and clinical value of hybrid imaging has been documented in small cohort studies and selected series of patients. Hybrid imaging appears to offer superior diagnostic and prognostic information compared with stand-alone or side-by-side interpretation of data sets. Particularly in patients with multivessel disease, the hybrid approach allows identification of flow-limiting coronary lesions and thereby provides useful information for the planning of revascularization procedures. Furthermore, integration of the detailed anatomical information from CTCA with the high molecular sensitivity of SPECT and PET may be useful to evaluate targeted molecular and cellular abnormalities in the future. While currently still restricted to specialized cardiac centres, the ongoing efforts to reduce radiation exposure and the increasing clinical interest will further pave the way for an increasing use of cardiac hybrid imaging in clinical practice.

Features of Disrupted Plaques by Coronary Computed Tomographic Angiography

Background—

This study was designed as a “proof-of-concept” to establish whether coronary computed tomographic angiography (CTA) has the capability to identify morphological features of plaque disruption.

Methods and Results—

In patients with unstable angina undergoing CTA and invasive coronary angiography within 30 days, quantitative CTA analysis was performed on all plaques for percent stenosis, volume, remodeling index, and volume of low-attenuation plaque (<50 Hounsfield units). Plaques with >25% stenosis were evaluated for CTA features of disruption, including ulceration and intraplaque dye penetration. Using invasive coronary angiography complex plaque as the reference standard for disruption, the sensitivity and specificity of ulceration and intraplaque dye penetration by CTA were determined. In 60 patients, 294 plaques were identified by CTA, of which 109 (37%) had features of disruption, including ulceration in 53 (18%) lesions and intraplaque dye penetration in 80 (27%). Compared with nondisrupted lesions, plaques with ulceration or intraplaque dye penetration by CTA were more voluminous (313±356 mm 3 versus 118±93 mm 3 P <0.0001), more often positively remodeled (94.5% versus 44.3%, P <0.0001), contained more low-attenuation plaque (99±161 mm 3 versus 19±18 mm 3 , P <0.0001), and were more often complex by ICA (57.8% versus 8.1%, P <0.0001). CTA features of disruption demonstrated modest to good sensitivity (53% to 81%) and good specificity (82% to 95%) for complex plaque by invasive coronary angiography.

Conclusions—

In this highly selected group of patients with unstable angina, CTA can delineate features of plaque disruption, including ulceration and intraplaque dye penetration, which are specific markers of invasively identified complex plaque. Further studies are needed to confirm the generalizability of the results and to explore the clinical and prognostic implications of these findings.

Influence of hemodynamic parameters on coronary artery attenuation with 320-detector coronary CT angiography

OBJECTIVES

To investigate the relationship between cardiac output, end diastolic volume and the contrast enhancement in coronary CT angiography using 320-detector CT.

MATERIALS AND METHODS

A total of 38 patients underwent coronary CT angiography by using a 320-detector CT scanner (detector configuration, 320 × 0.5mm). The attenuation value of the ascending aorta at the level of the orifice of the left main trunk was measured. The cardiac output (CO), end diastolic volume (EDV) and stroke volume (SV) were measured by echocardiography. The EDV was normalized to the body surface area (BSA). The total blood volume injected from the left ventricle from the beginning of the contrast agent injection to the time of image acquisition was determined to be the total injected blood volume (TIV), which is a product of SV and the number of heart beats from the initiation of contrast agent injection to the scan.

RESULTS

There was a negative correlation between the attenuation of the ascending aorta and CO (r = -0.44, P = 0.0053). However, the negative correlation between the attenuation of the ascending aorta and TIV was stronger (r = -0.52, P = 0.0007). There was a negative correlation between the attenuation of the ascending aorta and EDV/BSA (r = -0.45, P = 0.0039).

CONCLUSION

In 320-detector CT, contrast enhancement in CCTA with a lesser amount of contrast medium decreases when cardiac output is high. Patients with larger EDV/BSA may also show decreased attenuation.

Computerized method for evaluating diagnostic image quality of calcified plaque images in cardiac CT: validation on a physical dynamic cardiac phantom

PURPOSE

In cardiac computed tomography (CT), important clinical indices, such as the coronary calcium score and the percentage of coronary artery stenosis, are often adversely affected by motion artifacts. As a result, the expert observer must decide whether or not to use these indices during image interpretation. Computerized methods potentially can be used to assist in these decisions. In a previous study, an artificial neural network (ANN) regression model provided assessability (image quality) indices of calcified plaque images from the software NCAT phantom that were highly agreeable with those provided by expert observers. The method predicted assessability indices based on computer-extracted features of the plaque. In the current study, the ANN-predicted assessability indices were used to identify calcified plaque images with diagnostic calcium scores (based on mass) from a physical dynamic cardiac phantom. The basic assumption was that better quality images were associated with more accurate calcium scores.

METHODS

A 64-channel CT scanner was used to obtain 500 calcified plaque images from a physical dynamic cardiac phantom at different heart rates, cardiac phases, and plaque locations. Two expert observers independently provided separate sets of assessability indices for each of these images. Separate sets of ANN-predicted assessability indices tailored to each observer were then generated within the framework of a bootstrap resampling scheme. For each resampling iteration, the absolute calcium score error between the calcium scores of the motion-contaminated plaque image and its corresponding stationary image served as the ground truth in terms of indicating images with diagnostic calcium scores. The performances of the ANN-predicted and observer-assigned indices in identifying images with diagnostic calcium scores were then evaluated using ROC analysis.

RESULTS

Assessability indices provided by the first observer and the corresponding ANN performed similarly (AUC(OBS1) = 0.80 [0.73, 0.86] vs AUC(ANN1) = 0.88 [0.82, 0.92]) as that of the second observer and the corresponding ANN (AUC(OBS2) = 0.87 [0.83,0.91] vs. AUC(ANN2) = 0.90 [0.85, 0.94]). Moreover, the ANN-predicted indices were generated in a fraction of the time required to obtain the observer-assigned indices.

CONCLUSIONS

ANN-predicted assessability indices performed similar to observer-assigned assessability indices in identifying images with diagnostic calcium scores from the physical dynamic cardiac phantom. The results of this study demonstrate the potential of using computerized methods for identifying images with diagnostic clinical indices in cardiac CT images.

Progress and Current State of Coronary CT

The recent appearance of multislice computed tomography (CT) has enabled noninvasive imaging of the coronary artery. Particularly, the appearance of 64-row CT has rapidly promoted its spread into routine medical practice. In this report, progress and current state of coronary CT employing multislice CT are outlined.

In vivo CT detection of lipid-rich coronary artery atherosclerotic plaques using quantitative histogram analysis: a head to head comparison with IVUS

BACKGROUND

Coronary atherosclerotic plaque characterisation may contribute to risk stratification for future cardiovascular events. The ability of computed tomography to classify plaques as 'fibrous' or 'lipid-rich' based on their average CT attenuation has been investigated but is fraught with substantial limitations. In this study, we evaluated the potential of analysing the distribution of CT attenuation values measured in Hounsfield Units (HU) within coronary atherosclerotic plaques to classify non-calcified plaques into fibrous and lipid-rich subtypes. Intravascular ultrasound (IVUS) served as the gold standard.

PATIENTS AND METHODS

We evaluated the data sets of 40 patients (30 males, 59±10 years) who had been referred for invasive coronary angiography for clinical reasons and in whom IVUS was performed in at least one coronary vessel. Using dual source CT, coronary CT angiography was performed as a part of a research protocol within 24 h previous to invasive coronary angiography. A contrast-enhanced volume dataset was acquired with retrospective ECG gating (120 kV, 400 mAs/rot, collimation 2 mm×64 mm×0.6 mm, 60-80 ml contrast agent i.v). IVUS was performed using a 40-MHz IVUS catheter (Atlantis, Boston Scientific Corporation, Natick, MA) and motorized pullback at 0.5 mm/s. Fifty five corresponding non-calcified plaques within the coronary artery system were identified in both DSCT and IVUS using bifurcation points as fiducial markers. In DSCT data sets, serial parallel cross-sections (1mm slice thickness) were rendered orthogonally to the centre line of the coronary artery for each of the 55 plaques. For each cross section and each plaque, a histogram of CT attenuation values (increments of 10HU) was determined. The percentage of pixels with a density ≤30 HU was calculated. Using IVUS as the gold standard, plaques were classified as predominantly fibrous (hyperechoic) or predominantly lipid-rich (hypoechoic).

RESULTS

15 predominantly fibrous plaques vs. 40 predominantly lipid-rich plaques were identified in IVUS. The mean CT attenuation in both plaque types was significantly different (67±31 HU vs. 96±40 HU, p=0.006), yet with a wide overlap. For the 15 fibrous plaques identified in IVUS, the mean percentage of pixels ≤30 HU in CT was 6±10%. For lipid-rich plaques it was 16±10% (p<0.0001). ROC curve analysis revealed that a cut-off of 5.5% pixels with an attenuation ≤30 HU identified lipid rich plaques in CT angiography with a sensitivity of 95% (38/40, 95% CI 83-99) and a specificity of 80% (12/15, 95% CI 52-96) [AUC 0.9, 95% CI 0.7-1.0]. Using this threshold, the negative predictive value was 86% (12/14, 95% CI 57-98) and the positive predictive value was 93% (38/41, 95% CI 80-98).

CONCLUSION

Lipid-rich coronary atherosclerotic plaques contain a significantly higher percentage of pixels with low CT attenuation as compared to fibrous plaques. Histogram analysis may help to differentiate both plaque types. A cut-off of 5.5% of pixels with an attenuation of ≤30 HU allowed identification of lipid-rich plaques with a sensitivity of 95% and a specificity of 80%.

Plaque regression determined by intravascular ultrasound predicts long-term outcomes of patients with acute coronary syndrome

AIM

The usefulness of drugs to treat plaque regression is assessed by intravascular ultrasound (IVUS); however, the impact of plaque regression on clinical outcomes in patients with acute coronary syndrome (ACS) has not been established; therefore, we investigated the relationship between coronary plaque regression and long-term clinical outcomes.

METHODS

We analyzed data from 86 patients who underwent percutaneous coronary intervention (PCI) and who were assessed in detail at baseline and at 6 months of follow-up by measuring proximal non-culprit sites of PCI lesions using volumetric IVUS. Patients were divided according to changes in plaque volume over 6 months into one group with plaque regression (n =55; 64.0%) and another with progression (n =31; 36.0%). They were followed up observationally for a mean of 1,736 days.

RESULTS

Baseline characteristics at the time of ACS were similar between the groups. The probability of event-free survival was significantly higher in the regression group than in the progression group as estimated by the Kaplan-Meier method (Log-rank test, p =0.032). Furthermore, the Cox hazards model revealed the relative contribution of plaque regression as a predictor of cardiovascular events (hazard ratio: 0.26; 95% CI, 0.07 to 0.83; p =0.023).

CONCLUSIONS

Plaque regression determined by volumetric IVUS over a period of 6 months was associated with a lower rate of cardiovascular events among patients with ACS. This study also demonstrated that plaque regression could be a surrogate marker of future cardiovascular events.

Comparison of prognostic usefulness (three years) of computed tomographic angiography versus 64-slice computed tomographic calcium scanner in subjects without significant coronary artery disease

Coronary computerized tomographic angiography (CTA) has been used as a noninvasive method for ruling out high-grade stenoses. Even in the absence of such stenoses, analysis of coronary atherosclerosis may provide for important prognostic information, and this may be superior to exclusive coronary artery calcium scoring. We tested this hypothesis in patients undergoing CTA for clinical indications who had no stenoses requiring revascularization. From December 2004 to December 2006, 706 consecutive patients who underwent CTA but had no high-grade stenoses were included (58% men, mean age 59 ± 11 years). CTA and coronary artery calcium scoring (Agatston method) were performed using a 64-slice CT scanner with a gantry rotation time of 330 ms. CT angiograms were categorized as completely normal (group 1), showing minor plaque (group 2), or showing intermediate stenoses (group 3). Follow-up information was obtained in 670 patients (95%) over a mean of 3.2 years. There were 31 major adverse events (5%), namely 9 deaths (all noncoronary), 2 myocardial infarctions, 5 strokes, 13 coronary revascularization procedures (percutaneous or surgical > 6 months after CTA), and 2 peripheral percutaneous interventions. Coronary status as defined by CTA was predictive of major events after adjustment for age and gender. In group 1, the probability of event-free survival at 3 years was 100%; in group 2, it was 96%; and in group 3, it was 91%. Compared to group 1, the risk in group 2 was increased 2.3-fold, and in group 3, it was increased 5.6-fold after adjusting for age and gender. However, after addition of the coronary artery calcium score to the regression analysis, CT angiographic status no longer appeared to be predictive. In conclusion, the risk of a major adverse cardiovascular event or death increased in a graded manner with degree of coronary atherosclerosis as defined by CTA even in the absence of high-grade coronary stenoses. However, in the absence of high-grade stenoses, we were unable to demonstrate a superior prognostic value of CTA compared to coronary artery calcium.

Lipid-rich plaques predict non-target-lesion ischemic events in patients undergoing percutaneous coronary intervention

BACKGROUND

Despite growing interest in non-target lesion events in patients undergoing percutaneous coronary intervention (PCI), there has been little discussion of predictors.

METHODS AND RESULTS

A total of 155 consecutive patients who underwent PCI were enrolled. Conventional and integrated backscatter intravascular ultrasound (IB-IVUS) parameters were measured in non-target lesions utilizing a 40-MHz intravascular catheter. Lipid-rich plaques (LRP) were defined as lesions with an increased lipid volume (> median) and greater lipid content. Non-target ischemic events were defined as death, non-fatal myocardial infarction, any repeat revascularization and rehospitalization for angina involving the non-target vessel or the target vessel outside the index lesion. During the follow-up period (median: 1,265 days), non-target events were observed in 16 patients (11%). Using the Cox proportional hazard model, LRP (odds ratio [OR], 6.06; 95% confidence interval [CI]: 1.81-20.4, P = 0.0035), elevated serum C-reactive protein (CRP) levels (OR, 6.83; 95%CI: 2.19-21.3, P = 0.0009) and acute coronary syndrome present at baseline (OR, 4.08; 95%CI: 1.21-13.8, P = 0.024) were significantly and independently associated with non-target events. Synergistic effects of LRP and elevated serum CRP levels for prediction of non-target events (OR, 14.8; 95%CI: 4.57-48.0, P < 0.0001) were found even after adjusting for confounders.

CONCLUSIONS

LRP measured using IB-IVUS proved to be an independent morphologic predictor of non-target ischemic events after PCI, particularly enhancing the risk in patients with elevated serum CRP levels.

Assessment of coronary artery disease and calcified coronary plaque burden by computed tomography in patients with and without diabetes mellitus

Purpose

To compare the coronary atherosclerotic burden in patients with and without type-2 diabetes using CT Coronary Angiography (CTCA).

Methods and Materials

147 diabetic (mean age: 65 ± 10 years; male: 89) and 979 nondiabetic patients (mean age: 61 ± 13 years; male: 567) without a history of coronary artery disease (CAD) underwent CTCA. The per-patient number of diseased coronary segments was determined and each diseased segment was classified as showing obstructive lesion (luminal narrowing >50%) or not. Coronary calcium scoring (CCS) was assessed too.

Results

Diabetics showed a higher number of diseased segments (4.1 ± 4.2 vs. 2.1 ± 3.0; p < 0.0001); a higher rate of CCS > 400 (p < 0.001), obstructive CAD (37% vs. 18% of patients; p < 0.0001), and fewer normal coronary arteries (20% vs. 42%; p < 0.0001), as compared to nondiabetics. The percentage of patients with obstructive CAD paralleled increasing CCS in both groups. Diabetics with CCS ≤ 10 had a higher prevalence of coronary plaque (39.6% vs. 24.5%, p = 0.003) and obstructive CAD (12.5% vs. 3.8%, p = 0.01). Among patients with CCS ≤ 10 all diabetics with obstructive CAD had a zero CCS and one patient was asymptomatic.

Conclusions

Diabetes was associated with higher coronary plaque burden. The present study demonstrates that the absence of coronary calcification does not exclude obstructive CAD especially in diabetics.

Prediction of the no-reflow phenomenon during percutaneous coronary intervention using coronary computed tomography angiography

Coronary computed tomography angiography (CTA) can assess plaque characteristics and plaque size noninvasively. The purpose of this study was to investigate whether coronary CTA before percutaneous coronary intervention (PCI) can predict the no-reflow phenomenon during PCI. Seventy-eight patients [acute coronary syndrome (ACS) = 43, stable angina pectoris (SAP) = 35, male/female = 72/6, age: 65 ± 10 years] who underwent 16- or 64-slice CTA in the 4 weeks before PCI were enrolled. The low attenuation plaque size on CTA was compared between patients with (NR+) and without the no-reflow phenomenon (NR-). No-reflow phenomenon was observed in 11 patients, including 10 patients with ACS and 1 patient with SAP. Low attenuation plaque was detected in 9 (82%) NR(+) lesions and 35 (52%) NR(-) lesions. The length of low attenuation plaque was significantly longer in NR(+) than in NR(-) patients (9.0 ± 6.5 vs. 1.6 ± 2.7 mm, p < 0.0001). On step-wise regression analysis, ACS (p = 0.036, 95% CI = 0.009-0.258) and the presence of low attenuation plaque with a length >4.7 mm (p < 0.001, 95% CI = 0.447-0.778) were significant independent predictors of NR(-) no-reflow phenomenon. Low attenuation plaque with lesion length of >4.7 mm on coronary CTA and ACS were the significant predictors for the no-reflow phenomenon during PCI. Coronary CTA assessment before PCI would be useful to predict coronary events during PCI in advance.

Serial coronary CT angiography-verified changes in plaque characteristics as an end point: evaluation of effect of statin intervention

OBJECTIVES

This study sought to assess, by serial computed tomography angiography (CTA), the effect of statin treatment on coronary plaque morphology.

BACKGROUND

In addition to the assessment of luminal stenosis, CTA also allows characterization of plaque morphology. Large, positively remodeled plaques with large necrotic cores have been reported as indicators of plaque instability.

METHODS

CTA was performed in 32 patients (26 men, ages 64.3 +/- 8.5 years). Of these, 24 received fluvastatin after the baseline study; 8 subjects who refused statin treatment were followed as the control subjects. Serial imaging was performed after a median interval of 12 months. All vessels were examined in every subject, and a 10-mm-long segment was identified for comparison before and after intervention. Total plaque volume, low attenuation plaque (LAP) volume, lumen volume, and remodeling index were calculated.

RESULTS

In the statin-treated patients, the total plaque volume (92.3 +/- 37.7 vs. 76.4 +/- 26.5 mm(3), p < 0.01) and LAP volume (4.9 +/- 7.8 vs. 1.3 +/- 2.3 mm(3), p = 0.01) were significantly reduced over time; however, there was no change in the lumen volume (63.9 +/- 25.3 vs. 65.2 +/- 26.2 mm(3), p = 0.59). On the other hand, no change was observed in the CTA characteristics in the control subjects, including total plaque volume (94.4 +/- 21.2 vs. 98.4 +/- 28.6 mm(3), p = 0.48), LAP volume (2.1 +/- 3.0 vs. 2.3 +/- 3.6 mm(3), p = 0.91), and lumen volume (80.5 +/- 20.7 vs. 75.0 +/- 16.3 mm(3), p = 0.26). The plaque volume change (-15.9 +/- 22.2 vs. 4.0 +/- 14.0 mm(3), p = 0.01) and LAP volume change (-3.7 +/- 7.0 vs. 0.2 +/- 1.5 mm(3), p < 0.01) were significantly greater in the statin than the control group. The lumen volume (1.3 +/- 15.6 vs. -5.5 +/- 13.1 mm(3), p = 0.24) and remodeling index (-2.4 +/- 6.8% vs. -0.3 +/- 6.5%, p = 0.53) did not show the significant differences between the 2 groups. The decrease in the plaque volume was due to reduction in the LAP volume (R = 0.83, p < 0.01), and was not related to any changes in the lumen volume (R = 0.21, p = 0.24).

CONCLUSIONS

This preliminary study suggests that serial CTA evaluation of coronary plaques allows for the assessment of interval change in the plaque morphology. Statin treatment results in decreases in the plaque and necrotic core volume. The features known to be associated with plaque instability.

Prognostic value of coronary computed tomographic angiography in comparison with calcium scoring and clinical risk scores

BACKGROUND

Several studies have demonstrated a high accuracy of coronary computed tomography angiography (CCTA) for detection of obstructive coronary artery disease (CAD), whereas some studies have also shown a good prediction of cardiac events. However, it remains to be proven whether CCTA is better predictive of events than conventional risk scores or calcium scoring. Therefore, we compared CCTA with calcium scoring and clinical risk scores for the ability to predict cardiac events.

METHODS AND RESULTS

Patients (n=2223) with suspected CAD undergoing CCTA were followed up for a median of 28 months. The end point was the occurrence of cardiac events (cardiac death, nonfatal myocardial infarction, unstable angina requiring hospitalization, and coronary revascularization later than 90 days after CCTA). Patients with obstructive CAD had a significantly higher event rate (2.9% per year; 95% confidence interval, 2.1 to 4.0) than those without obstructive CAD, having an event rate 0.3% per year (95% confidence interval, 0.1 to 0.5; hazard ratio, 13.5; 95% confidence interval, 6.7 to 27.2; P<0.001). CCTA had significant incremental predictive value when compared with calcium scoring, both with scores assessing the degree of stenosis (P<0.001) and with scores assessing the number of diseased coronary segments (P=0.027).

CONCLUSIONS

In patients with suspected CAD, CCTA not only detects coronary stenosis but also improves prediction of cardiac events over and above conventional risk scores and calcium scoring. This may result in a reclassification of cardiovascular risk in a substantial proportion of patients.

Combined presence of aortic valve calcification and mitral annular calcification as a marker of the extent and vulnerable characteristics of coronary artery plaque assessed by 64-multidetector computed tomography

OBJECTIVE

We examined the association of aortic valve calcification (AVC) and mitral annular calcification (MAC) to coronary atherosclerosis using 64-multidetector computed tomography (MDCT).

BACKGROUND

Valvular calcification is considered a manifestation of atherosclerosis. The impact of multiple heart valve calcium deposits on the distribution and characteristics of coronary plaque is unknown.

METHODS

We evaluated 322 patients referred for 64-MDCT, and assessed valvular calcification and the extent of calcified (CAP), mixed (MCAP), and noncalcified coronary atherosclerotic plaque (NCAP) in accordance with the 17-coronary segments model. We assessed the vulnerable characteristics of coronary plaque with positive remodeling, low-density plaque (CT density ≤38 Hounsfield units), and the presence of adjacent spotty calcification.

RESULTS

In 49 patients with both AVC and MAC, the segment numbers of CAP and MCAP were larger than in those with a lack of valvular calcification and an isolated AVC (p<0.001 for both). Multivariate analyses revealed that a combined presence of AVC and MAC was independently associated with the presence (odds ratio [OR] 9.36, 95% confidence interval [95%CI] 1.55-56.53, p=0.015) and extent (β-estimate 1.86, p<0.001) of overall coronary plaque. When stratified by plaque composition, it was associated with the extent of CAP (β-estimate 1.77, p<0.001) and MCAP (β-estimate 1.04, p<0.001), but not with NCAP. Moreover, it was also related to the presence of coronary plaque with all three vulnerable characteristics (OR 4.87, 95%CI 1.85-12.83, p=0.001).

CONCLUSION

The combined presence of AVC and MAC is highly associated with the presence, extent, and vulnerable characteristics of coronary plaque identified by 64-MDCT.

CT angiography: current technology and clinical use

Since 1958, catheter angiography has assumed the role of gold standard for vascular imaging, despite the invasive nature of the procedure. Less invasive techniques for vascular imaging, such as computed tomographic angiography (CTA), have been developed and have matured in conjunction with developments in catheter arteriography. In a few cases, such as imaging, the aorta and the pulmonary arteries, CTA has supplanted catheter angiography as the gold standard. The expanding role of CTA emphasizes the need for deep, broad-based understanding of physical principles. This review describes CT hardware and associated software for angiography. The fundamentals of CTA physics are complemented with several clinical examples.

Cardiac computed tomography and myocardial perfusion scintigraphy for risk stratification in asymptomatic individuals without known cardiovascular disease: a position statement of the Working Group on Nuclear Cardiology and Cardiac CT of the European Society of Cardiology

Cardiovascular events remain one of the most frequent causes of mortality and morbidity worldwide. The majority of cardiac events occur in individuals without known coronary artery disease (CAD) and in low- to intermediate-risk subjects. Thus, the development of improved preventive strategies may substantially benefit from the identification, among apparently intermediate-risk subjects, of those who have a high probability for developing future cardiac events. Cardiac computed tomography and myocardial perfusion scintigraphy (MPS) by single photon emission computed tomography may play a role in this setting. In fact, absence of coronary calcium in cardiac computed tomography and inducible ischaemia in MPS are associated with a very low rate of major cardiac events in the next 3-5 years. Based on current evidence, the evaluation of coronary calcium in primary prevention subjects should be considered in patients classified as intermediate-risk based on traditional risk factors, since high calcium scores identify subjects at high-risk who may benefit from aggressive secondary prevention strategies. In addition, calcium scoring should be considered for asymptomatic type 2 diabetic patients without known CAD to select those in whom further functional testing by MPS or other stress imaging techniques may be considered to identify patients with significant inducible ischaemia. From available data, the use of MPS as first line testing modality for risk stratification is not recommended in any category of primary prevention subjects with the possible exception of first-degree relatives of patients with premature CAD in whom MPS may be considered. However, the Working Group recognizes that neither the use of computed tomography for calcium imaging nor of MPS have been proven to significantly improve clinical outcomes of primary prevention subjects in prospective controlled studies. This information would be crucial to adequately define the role of imaging approaches in cardiovascular preventive strategies.

Concept of Vulnerable/Unstable Plaque

Today’s concept of vulnerable plaque has evolved primarily from the early pioneering work uncovering the pivotal role of plaque rupture and coronary thrombosis as the major cause of acute myocardial infarction and sudden cardiac death. Since the first historical description of plaque rupture in 1844, several key studies by leading researchers and clinicians have lead to the current accepted views on lesion instability. Important to the complex paradigm of plaque destabilization and thrombosis are many discoveries beginning with the earliest descriptions of advanced plaques, reminiscent of abscesses encapsulated by fibrous tissue capable of rupture. It was not until the late 1980s that studies of remodeling provided keen insight into the growth of advanced plaques, beyond the simple accumulation of lipid. The emphasis in the next decade, however, was on a focused shift toward the mechanisms of lesion vulnerability based on the contribution of tissue proteolysis by matrix metalloproteinases as an essential factor responsible for thinning and rupture of the fibrous cap. In an attempt to unify the understanding of what constitutes a vulnerable plaque, morphological studies, mostly from autopsy, suggest the importance of necrotic core size, inflammation, and fibrous cap thickness. Definitive proof of the vulnerable plaque, however, remains elusive because animal or human data supporting a cause-and-effect relationship are lacking. Although emerging imagining technologies involving optical coherence tomography, high-resolution MRI, molecular biomarkers, and other techniques have far surpassed the limits of the early days of angiography, advancing the field will require establishing relevant translational animal models that produce vulnerable plaques at risk for rupture and further testing of these modalities in large prospective clinical trials.

The BioImage Study: novel approaches to risk assessment in the primary prevention of atherosclerotic cardiovascular disease--study design and objectives

The identification of asymptomatic individuals at risk for near-term atherothrombotic events to ensure optimal preventive treatment remains a challenging goal. In the BioImage Study, novel approaches are tested in a typical health-plan population. Based on certain demographic and risk characteristics on file with Humana Inc, a total of 7,687 men 55 to 80 years of age and women 60 to 80 years of age without evidence of atherothrombotic disease but presumed to be at risk for near-term atherothrombotic events were enrolled between January 2008 and June 2009. Those who met the prespecified eligibility criteria were randomized to a telephonic health survey only (survey only: n = 865), standard risk assessment (Framingham only: n = 718), or comprehensive risk assessment in a dedicated mobile facility equipped with advanced imaging tools (n = 6,104). Baseline examination included assessment of cardiovascular risk factors and screening for subclinical (asymptomatic) atherosclerosis with quantification of coronary artery calcification by computed tomography (CT), measurement of intima-media thickness, presence of carotid atherosclerotic plaques and abdominal aortic aneurysm by ultrasound, and ankle brachial index. Participants with one or more abnormal screening test results underwent advanced imaging with contrast-enhanced magnetic resonance imaging for carotid and aortic plaques, contrast-enhanced coronary CT angiography for luminal stenosis and noncalcified plaques, and 18F-fluorodeoxyglucose-positron emission tomography/CT for carotid and aortic plaque inflammation. Plasma, PAXgene RNA, and DNA samples were obtained, frozen, and stored for future biomarker discovery studies. All individuals will be followed until 600 major atherothrombotic events have occurred in those undergoing imaging. The BioImage Study will help identify those patients with subclinical atherosclerosis who are at risk for near-term atherothrombotic events and enable a more personalized management of care.