The effect of calcium score on the diagnostic accuracy of coronary computed tomography angiography

Cardiovascular Computed Tomography in the Diagnosis of Cardiovascular Disease: Beyond Lumen Assessment

Cardiovascular CT is being widely used in the diagnosis of cardiovascular disease due to the rapid technological advancements in CT scanning techniques. These advancements include the development of multi-slice CT, from early generation to the latest models, which has the capability of acquiring images with high spatial and temporal resolution. The recent emergence of photon-counting CT has further enhanced CT performance in clinical applications, providing improved spatial and contrast resolution. CT-derived fractional flow reserve is superior to standard CT-based anatomical assessment for the detection of lesion-specific myocardial ischemia. CT-derived 3D-printed patient-specific models are also superior to standard CT, offering advantages in terms of educational value, surgical planning, and the simulation of cardiovascular disease treatment, as well as enhancing doctor-patient communication. Three-dimensional visualization tools including virtual reality, augmented reality, and mixed reality are further advancing the clinical value of cardiovascular CT in cardiovascular disease. With the widespread use of artificial intelligence, machine learning, and deep learning in cardiovascular disease, the diagnostic performance of cardiovascular CT has significantly improved, with promising results being presented in terms of both disease diagnosis and prediction. This review article provides an overview of the applications of cardiovascular CT, covering its performance from the perspective of its diagnostic value based on traditional lumen assessment to the identification of vulnerable lesions for the prediction of disease outcomes with the use of these advanced technologies. The limitations and future prospects of these technologies are also discussed.

Hybrid model of CT-fractional flow reserve, pericoronary fat attenuation index and radiomics for predicting the progression of WMH: a dual-center pilot study

Objective

To develop and validate a hybrid model incorporating CT-fractional flow reserve (CT-FFR), pericoronary fat attenuation index (pFAI), and radiomics signatures for predicting progression of white matter hyperintensity (WMH).

Methods

A total of 226 patients who received coronary computer tomography angiography (CCTA) and brain magnetic resonance imaging from two hospitals were divided into a training set (n = 116), an internal validation set (n = 30), and an external validation set (n = 80). Patients who experienced progression of WMH were identified from subsequent MRI results. We calculated CT-FFR and pFAI from CCTA images using semi-automated software, and segmented the pericoronary adipose tissue (PCAT) and myocardial ROI. A total of 1,073 features were extracted from each ROI, and were then refined by Elastic Net Regression. Firstly, different machine learning algorithms (Logistic Regression [LR], Support Vector Machine [SVM], Random Forest [RF], k-nearest neighbor [KNN] and eXtreme Gradient Gradient Boosting Machine [XGBoost]) were used to evaluate the effectiveness of radiomics signatures for predicting WMH progression. Then, the optimal machine learning algorithm was used to compare the predictive performance of individual and hybrid models based on independent risk factors of WMH progression. Receiver operating characteristic (ROC) curve analysis, calibration and decision curve analysis were used to evaluate predictive performance and clinical value of the different models.

Results

CT-FFR, pFAI, and radiomics signatures were independent predictors of WMH progression. Based on the machine learning algorithms, the PCAT signatures led to slightly better predictions than the myocardial signatures and showed the highest AUC value in the XGBoost algorithm for predicting WMH progression (AUC: 0.731 [95% CI: 0.603-0.838] vs.0.711 [95% CI: 0.584-0.822]). In addition, pFAI provided better predictions than CT-FFR (AUC: 0.762 [95% CI: 0.651-0.863] vs. 0.682 [95% CI: 0.547-0.799]). A hybrid model that combined CT-FFR, pFAI, and two radiomics signatures provided the best predictions of WMH progression [AUC: 0.893 (95%CI: 0.815-0.956)].

Conclusion

pFAI was more effective than CT-FFR, and PCAT signatures were more effective than myocardial signatures in predicting WMH progression. A hybrid model that combines pFAI, CT-FFR, and two radiomics signatures has potential use for identifying WMH progression.

Investigating the impact of non-gated thoracic CT prior to CTCA to reduce layered testing

AIM

To determine the proportion of computed tomography (CT) coronary angiography (CTCA) referrals with coronary artery calcification (CAC) evident on previous non-cardiac CT imaging and how this impacted the diagnostic yield for CTCA, the requirement for additional diagnostic testing, and the associated costs to confirm or refute obstructive coronary artery disease (CAD).

MATERIALS AND METHODS

A retrospective review of CTCA examinations was undertaken between 01/05/2018 and 31/05/2020 in which the examinations were cross referenced for previous non-gated thoracic CT at Royal United Hospitals Bath. Major epicardial vessel CAC on baseline CT was re-evaluated by published semi-quantitative methods, giving a per-patient CAC score (mild = 1-3, moderate = 4-6, severe >6). Subsequent incomplete CTCA diagnostic yield, further testing, and cost implications were examined.

RESULTS

Of the 2140 CTCA examinations identified, 13% (280/2140) had a preceding non-gated thoracic CT (53% female, age 63 ± 11 years). The incomplete diagnostic rate increased with CAC grade, mild 32%, (RR 12; 95% CI 4-40), moderate 64% (RR 25; 95% CI 8-80), severe 75%, (RR 29; 95% CI 9-94). Additional diagnostic testing occurred in 4% for the mild CAC category, and 14% and 42% for moderate and severe, respectively. When severe CAC was identified on a non-gated thoracic CT a cost saving of £171/patient (dobutamine stress echo [DSE]) and £61/patient (myocardial perfusion scintigraphy [MPS]) was established with a direct to functional testing pathway.

CONCLUSIONS

In patients referred for CTCA where severe CAC was identified on a preceding non-gated thoracic CT a direct to functional testing altered management in 42% of cases and was cost-effective.

Diagnostic performance of 3D cardiac magnetic resonance perfusion in elderly patients for the detection of coronary artery disease as compared to fractional flow reserve

OBJECTIVES

In patients of advanced age, the feasibility of myocardial ischemia testing might be limited by age-related comorbidities and falling compliance abilities. Therefore, we aimed to test the accuracy of 3D cardiac magnetic resonance (CMR) stress perfusion in the elderly population as compared to reference standard fractional flow reserve (FFR).

METHODS

Fifty-six patients at age 75 years or older (mean age 79 ± 4 years, 35 male) underwent 3D CMR perfusion imaging and invasive coronary angiography with FFR in 5 centers using the same study protocol. The diagnostic accuracy of CMR was compared to a control group of 360 patients aged below 75 years (mean age 61 ± 9 years, 262 male). The percentage of myocardial ischemic burden (MIB) relative to myocardial scar burden was further analyzed using semi-automated software.

RESULTS

Sensitivity, specificity, and positive and negative predictive values of 3D perfusion CMR deemed similar for both age groups in the detection of hemodynamically relevant (FFR < 0.8) stenosis (≥ 75 years: 86%, 83%, 92%, and 75%; < 75 years: 87%, 80%, 82%, and 85%; p > 0.05 all). While MIB was larger in the elderly patients (15% ± 17% vs. 9% ± 13%), the diagnostic accuracy of 3D CMR perfusion was high in both elderly and non-elderly populations to predict pathological FFR (AUC: 0.906 and 0.866).

CONCLUSIONS

3D CMR perfusion has excellent diagnostic accuracy for the detection of hemodynamically relevant coronary stenosis, independent of patient age.

KEY POINTS

• The increasing prevalence of coronary artery disease in elderly populations is accompanied with a larger ischemic burden of the myocardium as compared to younger individuals. • 3D cardiac magnetic resonance perfusion imaging predicts pathological fractional flow reserve in elderly patients aged ≥ 75 years with high diagnostic accuracy. • Ischemia testing with 3D CMR perfusion imaging has similarly high accuracy in the elderly as in younger patients and it might be particularly useful when other non-invasive techniques are limited by aging-related comorbidities and falling compliance abilities.

Diagnostic and Clinical Value of FFRCT in Stable Chest Pain Patients With Extensive Coronary Calcification: The FACC Study

BACKGROUND

The influence of extensive coronary calcifications on the diagnostic and prognostic value of coronary computed tomography angiography-derived fractional flow reserve (FFR_CT) has been scantily investigated.

OBJECTIVES

The purpose of this study was to investigate the diagnostic and short-term role of FFR_CT in chest pain patients with Agatston score (AS) >399.

METHODS

This was a prospective multicenter study of 260 stable patients with suspected coronary artery disease (CAD) and AS >399. FFR_CT was measured blinded by an independent core laboratory. All patients underwent invasive coronary angiography (ICA) and FFR if indicated. The agreement of FFR_CT ≤0.80 with hemodynamically significant CAD on ICA/FFR (≥50% left main or ≥70% epicardial artery stenosis and/or FFR ≤0.80) was assessed. Patients undergoing FFR had colocation FFR_CT measured, and the lowest per-patient FFR_CT was registered in all patients. The association among per-patient FFR_CT, coronary revascularization, and major clinical events (all-cause mortality, myocardial infarction, or unstable angina hospitalization) at 90-day follow-up was evaluated.

RESULTS

Median age and AS were 68.5 years (IQR: 63-74 years) and 895 (IQR: 587-1,513), respectively. FFR_CT was ≤0.80 in 204 patients (78%). Colocation FFR_CT (n = 112) showed diagnostic accuracy, sensitivity, and specificity to identify hemodynamically significant CAD of 71%, 87%, and 54%. The area under the receiver-operating characteristics curve (AUC) was 0.75. When using the lowest FFR_CT (n = 260), per-patient accuracy, sensitivity, and specificity were 57%, 95%, and 32%, respectively. The AUC was 0.84. A total of 85 patients underwent revascularization, and FFR_CT was ≤0.80 in 96% of these. During follow-up, major clinical events occurred in 3 patients (1.2%), all with FFR_CT ≤0.80.

CONCLUSIONS

Most patients with AS >399 had FFR_CT ≤0.80. Using ICA/FFR as the reference revealed a moderate diagnostic accuracy of colocation FFR_CT. Compared with the lowest per-patient FFR_CT, colocation FFR_CT measurement improved diagnostic accuracy and specificity. The 90-day follow-up was favorable with few coronary revascularizations and no major clinical events occurring in patients with FFR_CT >0.80. (Use of FFR-CT in Stable Intermediate Chest Pain Patients With Severe Coronary Calcium Score [FACC]; NCT03548753).

Computed tomography angiography versus Agatston score for diagnosis of coronary artery disease in patients with stable chest pain: individual patient data meta-analysis of the international COME-CCT Consortium

Objectives

There is conflicting evidence about the comparative diagnostic accuracy of the Agatston score versus computed tomography angiography (CTA) in patients with suspected obstructive coronary artery disease (CAD).

Purpose

To determine whether CTA is superior to the Agatston score in the diagnosis of CAD.

Methods

In total 2452 patients with stable chest pain and a clinical indication for invasive coronary angiography (ICA) for suspected CAD were included by the Collaborative Meta-analysis of Cardiac CT (COME-CCT) Consortium. An Agatston score of > 400 was considered positive, and obstructive CAD defined as at least 50% coronary diameter stenosis on ICA was used as the reference standard.

Results

Obstructive CAD was diagnosed in 44.9% of patients (1100/2452). The median Agatston score was 74. Diagnostic accuracy of CTA for the detection of obstructive CAD (81.1%, 95% confidence interval [CI]: 77.5 to 84.1%) was significantly higher than that of the Agatston score (68.8%, 95% CI: 64.2 to 73.1%, p < 0.001). Among patients with an Agatston score of zero, 17% (101/600) had obstructive CAD. Diagnostic accuracy of CTA was not significantly different in patients with low to intermediate (1 to < 100, 100–400) versus moderate to high Agatston scores (401–1000, > 1000).

Conclusions

Results in our international cohort show CTA to have significantly higher diagnostic accuracy than the Agatston score in patients with stable chest pain, suspected CAD, and a clinical indication for ICA. Diagnostic performance of CTA is not affected by a higher Agatston score while an Agatston score of zero does not reliably exclude obstructive CAD.

Key Points

• CTA showed significantly higher diagnostic accuracy (81.1%, 95% confidence interval [CI]: 77.5 to 84.1%) for diagnosis of coronary artery disease when compared to the Agatston score (68.8%, 95% CI: 64.2 to 73.1%, p < 0.001).

• Diagnostic performance of CTA was not affected by increased amount of calcium and was not significantly different in patients with low to intermediate (1 to <100, 100–400) versus moderate to high Agatston scores (401–1000, > 1000).

• Seventeen percent of patients with an Agatston score of zero showed obstructive coronary artery disease by invasive angiography showing absence of coronary artery calcium cannot reliably exclude coronary artery disease.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00330-022-08619-4.

Added Value of Computed Tomography Virtual Intravascular Endoscopy in the Evaluation of Coronary Arteries with Stents or Plaques

Coronary computed tomography angiography (CCTA) is a widely used imaging modality for diagnosing coronary artery disease (CAD) but is limited by a high false positive rate when evaluating coronary arteries with stents and heavy calcifications. Virtual intravascular endoscopy (VIE) images generated from CCTA can be used to qualitatively assess the vascular lumen and might be helpful for overcoming this challenge. In this study, one hundred subjects with coronary stents underwent both CCTA and invasive coronary angiography (ICA). A total of 902 vessel segments were analyzed using CCTA and VIE. The vessel segments were first analyzed on CCTA alone. Then, using VIE, the segments were classified qualitatively as either negative or positive for in-stent restenosis (ISR) or CAD. These results were compared, using ICA as the reference, to determine the added diagnostic value of VIE. Of the 902 analyzed vessel segments, CCTA/VIE had sensitivity, specificity, accuracy, positive predictive value, and negative predictive value (shown in %) of 93.9/90.2, 96.2/98.2, 96.0/97.7, 70.0/83.1, and 99.4/99.0, respectively, in diagnosing ISR or CAD, with significantly improved specificity (p = 0.025), accuracy (p = 0.046), and positive predictive value (p = 0.047). VIE can be a helpful addition to CCTA when evaluating coronary arteries.

Current and Future Applications of Artificial Intelligence in Coronary Artery Disease

Cardiovascular diseases (CVDs) carry significant morbidity and mortality and are associated with substantial economic burden on healthcare systems around the world. Coronary artery disease, as one disease entity under the CVDs umbrella, had a prevalence of 7.2% among adults in the United States and incurred a financial burden of 360 billion US dollars in the years 2016–2017. The introduction of artificial intelligence (AI) and machine learning over the last two decades has unlocked new dimensions in the field of cardiovascular medicine. From automatic interpretations of heart rhythm disorders via smartwatches, to assisting in complex decision-making, AI has quickly expanded its realms in medicine and has demonstrated itself as a promising tool in helping clinicians guide treatment decisions. Understanding complex genetic interactions and developing clinical risk prediction models, advanced cardiac imaging, and improving mortality outcomes are just a few areas where AI has been applied in the domain of coronary artery disease. Through this review, we sought to summarize the advances in AI relating to coronary artery disease, current limitations, and future perspectives.

3D-Printed Coronary Plaques to Simulate High Calcification in the Coronary Arteries for Investigation of Blooming Artifacts

The diagnostic value of coronary computed tomography angiography (CCTA) is significantly affected by high calcification in the coronary arteries owing to blooming artifacts limiting its accuracy in assessing the calcified plaques. This study aimed to simulate highly calcified plaques in 3D-printed coronary models. A combination of silicone + 32.8% calcium carbonate was found to produce 800 HU, representing extensive calcification. Six patient-specific coronary artery models were printed using the photosensitive polyurethane resin and a total of 22 calcified plaques with diameters ranging from 1 to 4 mm were inserted into different segments of these 3D-printed coronary models. The coronary models were scanned on a 192-slice CT scanner with 70 kV, pitch of 1.4, and slice thickness of 1 mm. Plaque attenuation was measured between 1100 and 1400 HU. Both maximum-intensity projection (MIP) and volume rendering (VR) images (wide and narrow window widths) were generated for measuring the diameters of these calcified plaques. An overestimation of plaque diameters was noticed on both MIP and VR images, with measurements on the MIP images close to those of the actual plaque sizes (<10% deviation), and a large measurement discrepancy observed on the VR images (up to 50% overestimation). This study proves the feasibility of simulating extensive calcification in coronary arteries using a 3D printing technique to develop calcified plaques and generate 3D-printed coronary models.

The accuracy of coronary CT angiography in patients with coronary calcium score above 1000 Agatston Units: Comparison with quantitative coronary angiography

BACKGROUND

High amounts of coronary artery calcium (CAC) pose challenges in interpretation of coronary CT angiography (CCTA). The accuracy of stenosis assessment by CCTA in patients with very extensive CAC is uncertain.

METHODS

Retrospective study was performed including patients who underwent clinically directed CCTA with CAC score >1000 and invasive coronary angiography within 90 days. Segmental stenosis on CCTA was graded by visual inspection with two-observer consensus using categories of 0%, 1-24%, 25-49%, 50-69%, 70-99%, 100% stenosis, or uninterpretable. Blinded quantitative coronary angiography (QCA) was performed on all segments with stenosis ≥25% by CCTA. The primary outcome was vessel-based agreement between CCTA and QCA, using significant stenosis defined by diameter stenosis ≥70%. Secondary analyses on a per-patient basis and inclusive of uninterpretable segments were performed.

RESULTS

726 segments with stenosis ≥25% in 346 vessels within 119 patients were analyzed. Median coronary calcium score was 1616 (1221-2118). CCTA identification of QCA-based stenosis resulted in a per-vessel sensitivity of 79%, specificity of 75%, positive predictive value (PPV) of 45%, negative predictive value (NPV) of 93%, and accuracy 76% (68 false positive and 15 false negative). Per-patient analysis had sensitivity 94%, specificity 55%, PPV 63%, NPV 92%, and accuracy 72% (30 false-positive and 3 false-negative). Inclusion of uninterpretable segments had variable effect on sensitivity and specificity, depending on whether they are considered as significant or non-significant stenosis.

CONCLUSIONS

In patients with very extensive CAC (>1000 Agatston units), CCTA retained a negative predictive value ​> ​90% to identify lack of significant stenosis on a per-vessel and per-patient level, but frequently overestimated stenosis.

Deep learning analysis in coronary computed tomographic angiography imaging for the assessment of patients with coronary artery stenosis

BACKGROUND AND OBJECTIVE

Recently, deep convolutional neural network has significantly improved image classification and image segmentation. If coronary artery disease (CAD) can be diagnosed through machine learning and deep learning, it will significantly reduce the burdens of the doctors and accelerate the critical patient diagnoses. The purpose of the study is to assess the practicability of utilizing deep learning approaches to process coronary computed tomographic angiography (CCTA) imaging (termed CCTA-artificial intelligence, CCTA-AI) in coronary artery stenosis.

MATERIALS AND METHODS

A CCTA reconstruction pipeline was built by utilizing deep learning and transfer learning approaches to generate auto-reconstructed CCTA images based on a series of two-dimensional (2D) CT images. 150 patients who underwent successively CCTA and digital subtraction angiography (DSA) from June 2017 to December 2017 were retrospectively analyzed. The dataset was divided into two parts comprising training dataset and testing dataset. The training dataset included the CCTA images of 100 patients which are trained using convolutional neural networks (CNN) in order to further identify various plaque classifications and coronary stenosis. The other 50 CAD patients acted as testing dataset that is evaluated by comparing the auto-reconstructed CCTA images with traditional CCTA images on the condition that DSA images are regarded as the reference method. Receiver operating characteristic (ROC) analysis was used for statistical analysis to compare CCTA-AI with DSA and traditional CCTA in the aspect of detecting coronary stenosis and plaque features.

RESULTS

AI significantly reduces time for post-processing and diagnosis comparing to the traditional methods. In identifying various degrees of coronary stenosis, the diagnostic accuracy of CCTA-AI is better than traditional CCTA (AUC_AI = 0.870, AUC_CCTA = 0.781, P < 0.001). In identifying ≥ 50% stenotic vessels, the accuracy, sensitivity, specificity, positive predictive value and negative predictive value of CCTA-AI and traditional method are 86% and 83%, 88% and 59%, 85% and 94%, 73% and 84%, 94% and 83%, respectively. In the aspect of identifying plaque classification, accuracy of CCTA-AI is moderate compared to traditional CCTA (AUC = 0.750, P < 0.001).

CONCLUSION

The proposed CCTA-AI allows the generation of auto-reconstructed CCTA images from a series of 2D CT images. This approach is relatively accurate for detecting ≥50% stenosis and analyzing plaque features compared to traditional CCTA.

The effect of coronary calcification on diagnostic performance of machine learning-based CT-FFR: a Chinese multicenter study

OBJECTIVE

To investigate the effect of coronary calcification morphology and severity on the diagnostic performance of machine learning (ML)-based coronary CT angiography (CCTA)-derived fractional flow reserve (CT-FFR) with FFR as a reference standard.

METHODS

A total of 442 patients (61.2 ± 9.1 years, 70% men) with 544 vessels who underwent CCTA, ML-based CT-FFR, and invasive FFR from China multicenter CT-FFR study were enrolled. The effect of calcification arc, calcification remodeling index (CRI), and Agatston score (AS) on the diagnostic performance of CT-FFR was investigated. CT-FFR ≤ 0.80 and lumen reduction ≥ 50% determined by CCTA were identified as vessel-specific ischemia with invasive FFR as a reference standard.

RESULTS

Compared with invasive FFR, ML-based CT-FFR yielded an overall sensitivity of 0.84, specificity of 0.94, and accuracy of 0.90 in a total of 344 calcification lesions. There was no statistical difference in diagnostic accuracy, sensitivity, or specificity of CT-FFR across different calcification arc, CRI, or AS levels. CT-FFR exhibited improved discrimination of ischemia compared with CCTA alone in lesions with mild-to-moderate calcification (AUC, 0.89 vs. 0.69, p < 0.001) and lesions with CRI ≥ 1 (AUC, 0.89 vs. 0.71, p < 0.001). The diagnostic accuracy and specificity of CT-FFR were higher than CCTA alone in patients and vessels with mid (100 to 299) or high (≥ 300) AS.

CONCLUSION

Coronary calcification morphology and severity did not influence diagnostic performance of CT-FFR in ischemia detection, and CT-FFR showed marked improved discrimination of ischemia compared with CCTA alone in the setting of calcification.

KEY POINTS

• CT-FFR provides superior diagnostic performance than CCTA alone regardless of coronary calcification. • No significant differences in the diagnostic performance of CT-FFR were observed in coronary arteries with different coronary calcification arcs and calcified remodeling indexes. • No significant differences in the diagnostic accuracy of CT-FFR were observed in coronary arteries with different coronary calcification score levels.

Subtracted Computed Tomography Angiography in the Evaluation of Coronary Arteries With Severe Calcification or Stents Using a 320-Row Computed Tomography Scanner

PURPOSE

Coronary computed tomography angiography (CCTA) has its limitations in evaluating arteries with stents or heavy calcification. This study compares the diagnostic performance of subtracted coronary computed tomography angiography (SCCTA) and nonsubtracted coronary computed tomography angiography (NSCCTA) in evaluating coronary artery disease (CAD) and in-stent restenosis (ISR).

MATERIALS AND METHODS

Twelve patients with stents and 20 patients with heavy coronary calcifications (total Agatston's score >400) underwent both SCCTA and invasive coronary angiography (ICA) with an interval of <3 months. Four subjects in the stented group also had heavy calcifications. Overall, 30 stented segments and 202 calcified segments were assessed to compare the diagnostic performance of SCCTA and NSCCTA in detecting ISR and CAD.

RESULTS

For the 30 stented segments, SCCTA/NSCCTA had a sensitivity, specificity, accuracy, positive predictive value (PPV) and negative predictive value (NPV) (shown in %) of 66.7/100, 100/55.6, 96.7/60, 100/20, and 96.4/100 in diagnosing ISR, respectively. For the 202 calcified segments, SCCTA/NSCCTA had a sensitivity, specificity, accuracy, PPV, and NPV of 68.8/84.4, 97.6/76.5, 93.1/77.7, 84.6/40.3, and 94.3/96.3 in diagnosing CAD, respectively. For both stented and calcified segments, SCCTA was significantly superior to NSCCTA in specificity and accuracy. For the calcified segments, SCCTA was significantly superior to NSCCTA in PPV. There was no significant difference in the diagnostic performance of SCCTA between the stented and calcified segments.

CONCLUSIONS

The diagnostic accuracy and specificity of SCCTA are significantly superior to those of NSCCTA in evaluating CAD and ISR. SCCTA shows no statistical difference in its diagnostic performance between the stented and calcified segments.

Debates over NICE Guideline Update: What Are the Roles of Nuclear Cardiology in the Initial Evaluation of Stable Chest Pain?

Recent clinical trials have demonstrated the values of cardiac computed tomography (CT) in the initial evaluation of stable chest pain which led to drastic changes in the National Institute for Health and Care Excellence (NICE) guidelines in 2016. According to the updated NICE guidelines, cardiac CT should be performed as the initial cardiac testing in stable chest pain regardless of pre-test probability (PTP) of coronary artery disease (CAD). As a result, cardiac CT is now considered as a validated gatekeeper for assessing stable chest pain, which precedes all the functional studies including nuclear myocardial perfusion imaging (MPI). Nuclear MPI, in contrast, has been assigned as one of the second-line studies, which is inevitably dependent on the results of cardiac CT. However, nuclear MPI has genuine values in the diagnosis, treatment decision, and prognostic stratification of stable chest pain, which cannot be replaced by cardiac CT. In this review, the updated NICE guidelines and related cardiac CT trials will be critically reviewed from the view of nuclear physicians and the exceptional values of nuclear MPI will be described along with the future perspectives.

Functional and Anatomical Testing in Intermediate Risk Chest Pain Patients with a High Coronary Calcium Score: Rationale and Design of the FACC Study

Current guidelines do not recommend coronary computed tomography angiography (CCTA) in patients with high levels of coronary calcium, as severe calcification leads to difficulties in estimating stenosis severity due to blooming artifacts obscuring the vessel lumen. Whether the CCTA-derived fractional flow reserve (FFRCT) improves the diagnostic performance of CCTA in patients with high levels of coronary calcification has not been sufficiently evaluated. We hypothesize that a noninvasive diagnostic strategy using FFRCT will perform comparably to an invasive diagnostic strategy in the detection of hemodynamically significant coronary artery disease (CAD) in clinical stable chest pain patients with high levels of coronary calcium. In this prospective, blinded, multicenter study, patients with suspected stable CAD referred for CCTA and demonstrating an Agatston score >399 will be included. Patients accepting inclusion will, in addition to CCTA, undergo invasive coronary angiography (ICA) and invasive FFR measurement. FFRCT analyses are performed by an external core laboratory blinded to any patient data, and the FFRCT results are blinded to all participating study sites. The primary objective is to evaluate whether FFRCT can identify patients with and without hemodynamically significant CAD, when ICA with FFR is the reference standard. A negative study result would question the clinical usefulness of FFRCT in patients with high levels of coronary calcium. A positive study result, however, would imply a reduction in the number of patients referred for coronary catheterization and, at the same time, increase the proportion of patients with hemodynamically significant CAD at the subsequent invasive examination.

Synchrotron radiation computed tomography assessment of calcified plaques and coronary stenosis with different slice thicknesses and beam energies on 3D printed coronary models

Background

To investigate the effect of different slice thicknesses and beam energies on the visualization and assessment of coronary artery stenosis caused by calcified plaques using synchrotron radiation computed tomography (CT) based on 3D printed coronary artery models.

Methods

Patient-specific 3D coronary models were created based on 3 sample coronary CT angiographic cases with calcified plaques in the left coronary arteries. In addition to the original significant coronary stenosis (>70%) shown on these CT images, stenoses of <50% and >90% were created in the segmented coronary models for simulation of different degrees of stenosis. The coronary lumen and calcification were printed with soft and rigid materials to simulate properties of coronary wall and calcified plaque, respectively. The models were scanned with synchrotron radiation CT with beam energies of 30, 40 and 50 keV and spatial resolution of 0.019×0.019×0.019 mm³ voxel size. Original high-resolution images were reconstructed with slice thicknesses of 0.095, 0.208, 0.302 and 0.491 mm to determine the effect of spatial resolution on plaque and coronary stenosis assessment based on 2D axial and 3D virtual intravascular endoscopy (VIE) images.

Results

Three coronary artery models were successfully printed with plaques placed in the coronary arteries to simulate different degrees of stenosis. 2D and 3D VIE images reconstructed with slice thicknesses of 0.095, 0.208 and 0.302 mm allowed for accurate assessment of coronary plaques and lumen stenosis with no significant differences (P>0.05). Synchrotron radiation CT images reconstructed with a slice thickness of 0.491 mm resulted in overestimation of coronary stenosis when compared to other images on 2D and 3D VIE views (<50% vs. 55-72%; 70-79% vs. 80-90%) with significant differences (P<0.05). Similarly, irregular plaque appearances were observed on 2D and 3D VIE images with a slice thickness of 0.491 mm when compared to others using thin slice thicknesses. The scanning protocol with beam energy of 30 keV provided optimal visualization of coronary lumen and plaque appearances.

Conclusions

This study shows the feasibility of using 3D printed coronary artery models to simulate calcifications and different degrees of coronary stenosis. High resolution synchrotron radiation CT imaging with the 30 keV beam energy enables accurate assessment of coronary stenosis in the presence of calcification, thus highlighting the importance of high spatial resolution in the diagnosis of calcified coronary plaques.

Cardiovascular Imaging Techniques in Systemic Rheumatic Diseases

The risk of cardiovascular (CV) events and mortality is significantly higher in patients with systemic rheumatic diseases than in the general population. Although CV involvement in such patients is highly heterogeneous and may affect various structures of the heart, it can now be diagnosed earlier and promptly treated. Various types of assessments are employed for the evaluation of CV risk such as transthoracic or transesophageal echocardiography, magnetic resonance imaging (MRI), and computed tomography (CT) to investigate valve abnormalities, pericardial disease, and ventricular wall motion defects. The diameter of coronary arteries can be assessed using invasive quantitative coronarography or intravascular ultrasound, and coronary flow reserve can be assessed using non-invasive transesophageal or transthoracic ultrasonography (US), MRI, CT, or positron emission tomography (PET) after endothelium-dependent vasodilation. Finally, peripheral circulation can be measured invasively using strain-gauge plethysmography in an arm after the arterial infusion of an endothelium-dependent vasodilator or non-invasively by means of US or MRI measurements of flow-mediated vasodilation of the brachial artery. All of the above are reliable methods of investigating CV involvement, but more recently, introduced use of speckle tracking echocardiography and 3-dimensional US are diagnostically more accurate.

An investigation of correlation between left coronary bifurcation angle and hemodynamic changes in coronary stenosis by coronary computed tomography angiography-derived computational fluid dynamics

Background

To investigate the correlation between left coronary bifurcation angle and coronary stenosis as assessed by coronary computed tomography angiography (CCTA)-generated computational fluid dynamics (CFD) analysis when compared to the CCTA analysis of coronary lumen stenosis and plaque lesion length with invasive coronary angiography (ICA) as the reference method.

Methods

Thirty patients (22 males, mean age: 59±6.9 years) with calcified plaques at the left coronary artery were included in the study with all patients undergoing CCTA and ICA examinations. CFD simulation was performed to analyze hemodynamic changes to the left coronary artery models in terms of wall shear stress, wall pressure and flow velocity, with findings correlated to the coronary stenosis and degree of bifurcation angle. Calcified plaque length was measured in the left coronary artery with diagnostic value compared to that from coronary lumen and bifurcation angle assessments.

Results

Of 26 significant stenosis at left anterior descending (LAD) and 13 at left circumflex (LCx) on CCTA, only 14 and 5 of them were confirmed to be >50% stenosis at LAD and LCx respectively on ICA, resulting in sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of 100%, 52%, 49% and 100%. The mean plaque length was measured 5.3±3.6 and 4.4±1.9 mm at LAD and LCx, respectively, with diagnostic sensitivity, specificity, PPV and NPV being 92.8%, 46.7%, 61.9% and 87.5% for extensively calcified plaques. The mean bifurcation angle was measured 83.9±13.6º and 83.8±13.3º on CCTA and ICA, respectively, with no significant difference (P=0.98). The corresponding sensitivity, specificity, PPV and NPV were 100%, 78.6%, 84.2% and 100% based on bifurcation angle measurement on CCTA, 100%, 73.3%, 78.9% and 100% based on bifurcation angle measurements on ICA, respectively. Wall shear stress was noted to increase in the LAD and LCx models with significant stenosis and wider angulation (>80º), but demonstrated little or no change in most of the coronary models with no significant stenosis and narrower angulation (<80º).

Conclusions

This study further clarifies the relationship between left coronary bifurcation angle and significant stenosis, with angulation measurement serving as a more accurate approach than coronary lumen assessment or plaque lesion length for determining significant coronary stenosis. Left coronary bifurcation angle is suggested to be incorporated into coronary artery disease (CAD) assessment when diagnosing significant CAD.

Comparison of the Left Main Coronary Bifurcating Angle among Patients with Normal, Non-significantly and Significantly Stenosed Left Coronary Arteries

We evaluated the correlation of the left main coronary bifurcating angle (LCBA) with the severity of coronary atherosclerosis, risk factors of coronary artery disease (CAD) and the feasibility of measuring the LBCA using the axial plane. Coronary Computed tomography angiographies (CTAs) of 313 patients between Nov. 2006 and Oct. 2013 were reviewed and separated into three groups. Group I (211 patients) had significant stenosis (≥50%) of the left anterior descending coronary artery (LAD) and/or left circumflex coronary artery (LCX). Group II (62 subjects) had atherosclerosis without significant stenosis. Group III (40 subjects) had unremarkable coronary CTAs. Both Group I and II patients received conventional catheter angiography to confirm the severities of coronary stenoses. Significant differences were found among the groups with respect to risk factors, such as male gender, hypertension and body mass index. Axial plane measurement was feasible in most patients (82.1%), without significant differences among the groups. The mean LCBA was 84.7° among all patients, and significantly differed among groups I, II and III (87.34°, 81.16° and 75.53°, P < 0.001). The LCBA of group I was significantly higher than group III (P < 0.001) in univariate analysis, but insignificant in multivariate analysis (P = 0.064).

Prognostic Value of Coronary Artery Calcium Score for Determination of Presence and Severity of Coronary Artery Disease

Background

There are controversies regarding the usefulness of coronary artery calcium score (CACS) for predicting coronary artery stenosis. The aim of this study was to determine the prognostic value of CACS for determining the presence and severity of coronary artery disease (CAD) in patients with sign and symptoms of the disease.

Material/Methods

In this cross-sectional study, 748 consecutive patients with suspected CAD, referred for coronary computed tomography angiography (CCTA), were enrolled. The mean CACS was compared between patients with different severities of coronary artery stenosis. The association between CACS and different CAD risk factors was determined as well. Different cutoff points of CACS for discriminating between different levels of coronary artery stenosis was determined using receiver operating characteristic (ROC) curves.

Results

The mean CACS was significantly different between different levels of coronary artery stenosis (P<0.001) and there was a significant positive association between the severity of CAD and CACS (P<0.001,r=0.781). ROC curve analysis indicated that the optimal cutoff point for discriminating between CAD (presence of stenosis) and the non-stenosis condition was 5.35 with 88.6% sensitivity and 86.2% specificity. Area under the curve for different levels of coronary artery stenosis did not have sufficient sensitivity and specificity for discriminating between different levels of CAD severity (<70%).

Conclusions

The study demonstrated that there is a significant association between CACS and the presence as well as the severity of CAD. CACS could have an appropriate prognostic value for the determination of coronary artery stenosis but not for discriminating between different severities of stenoses.

The Diagnostic Performance of Coronary CT Angiography for the Assessment of Coronary Stenosis in Calcified Plaque

Purpose

To prospectively evaluate the diagnostic performance of coronary CT angiography (CCTA) for the assessment of coronary stenosis in a calcified plaque, by using conventional coronary angiography (CAG) as a standard reference.

Materials and Methods

Eight hundred and ninety-four patients were known to have or have been suspicious of having coronary artery disease, underwent CCTA and conventional coronary angiography (CAG). All the images acquired were assessed. The calcified plaque in CCTA was classified into four types (I-IV) according to the ratio of calcified plaque volume to vessel circumference (RVTC). Overall diagnostic accuracy was made under receiver operating characteristic curve (AUC) analysis. CAG was used as the standard reference.

Results

A total of 12845 segments were evaluated in 894 patients, among which 4955 calcified plaques were detected on 3645(28.4%) segments by CCTA. The overall AUC, sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were 0.939, 97.8%, 90.1%, 71.2% and 99.4%, respectively. In type I-II calcification, CCTA had high diagnostic performance in AUC (type I: 0.983; type II: 0.976), sensitivity (96.7%; 98.1%), specificity (99.8%; 97.0%), PPV (95.7%; 90.1%), NPV (99.8%; 99.5%) and accuracy (99.6%; 97.3%). In type III-IV calcification, CCTA has high performance in sensitivity (type III: 97.6%; type IV: 97.9%) and NPV (98.3%; 98.7%), moderate performance in AUC (0.877; 0.829), while remarkable decrease in specificity (78.7%; 67.9%), PPV (71.0%; 56.2%) and accuracy (84.9%; 76.8%).

Conclusion

CCTA has highest accuracy in diagnosing the coronary artery stenosis of type I-II calcified plaques, but has a significant decrease in specificity, PPV and accuracy in type III-IV calcified plaque.

Coronary CT Angiography in Heavily Calcified Coronary Arteries: Improvement of Coronary Lumen Visualization and Coronary Stenosis Assessment With Image Postprocessing Methods

To compare the diagnostic value of coronary CT angiography (CCTA) with use of 2 image postprocessing methods (CCTA_S) and (CCTA_OS) and original data (CCTA_O) for the assessment of heavily calcified plaques. Fifty patients (41 men, 9 women; mean age 61.9 years ± 9.1) with suspected coronary artery disease who underwent CCTA and invasive coronary angiography (ICA) examinations were included in the study. Image data were postprocessed with "sharpen" and smooth reconstruction algorithms in comparison with the original data without undergoing any image postprocessing to determine the effects on suppressing blooming artifacts due to heavy calcification in the coronary arteries. Minimal lumen diameter and degree of stenosis were measured and compared between CCTA_S, CCTA_OS, and CCTA_O with ICA as the reference method. The area under the curve (AUC) by receiver-operating characteristic curve analysis (ROC) was also compared among these 3 CCTA techniques. On a per-vessel assessment, the sensitivity, specificity, positive predictive value and negative predictive value, and 95% confidence interval (CI) were 100% (95% CI: 89%, 100%), 33% (95% CI: 22%, 45%), 41% (95% CI: 30%, 53%), 100% (95% CI: 85%, 100%) for CCTA_O, 94% (95% CI: 79%, 99%), 66% (95% CI: 54%, 77%), 57% (95% CI: 43%, 70%), and 95% (95% CI: 85%, 99%) for CCTA_S, 94% (95% CI: 79%, 99%), 44% (95% CI: 32%, 57%), 44% (95% CI: 32%, 57%), and 97% (95% CI: 79%, 99%) for CCTA_OS, respectively. The AUC by ROC curve analysis for CCTA_S showed significant improvement for detection of >50% coronary stenosis in left anterior descending coronary artery compared to that of CCTA_OS and CCTA_O methods (P < 0.05), with no significance differences for detection of coronary stenosis in the left circumflex and right coronary arteries (P > 0.05).CCTA with "sharpen" reconstruction reduces blooming artifacts from heavy calcification, thus, leading to significant improvement of specificity and positive predictive value of CCTA in patients with heavily calcified plaques. However, specificity is still moderate and additional functional imaging may be needed.

Coronary CT angiography in calcified coronary plaques: Comparison of diagnostic accuracy between bifurcation angle measurement and coronary lumen assessment for diagnosing significant coronary stenosis

BACKGROUND

To investigate the diagnostic value of coronary CT angiography (CCTA) by bifurcation angle measurement in the assessment of calcified plaques compared to conventional coronary lumen analysis.

METHODS

Fifty-three patients with calcified plaques identified on CCTA in the left coronary artery were included in the study. Minimal lumen diameter (MLD) and bifurcation angle between the left anterior descending (LAD) and left circumflex (LCx) arteries were measured and compared between CCTA and invasive coronary angiography (ICA), while the areas under the curves (AUCs) by receiver-operating characteristic curve analysis (ROC) were compared between CCTA and ICA with regard to the diagnostic value of using bifurcation angle as a criterion.

RESULTS

On a per-vessel assessment, the sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) and 95% confidence interval (CI) with the use of bifurcation angle for determining coronary stenosis were 100% (86%, 100%), 79% (59%, 92%), 81% (62%, 92%), and 100% (85%, 100%) for CCTA, and 100% (86%, 100%), 82% (63%, 94%), 83% (65%, 94%), and 100% (85%, 100%) for ICA, respectively. While the sensitivity and NPV remained unchanged, the specificity and PPV of CCTA by MLD were 33% (21%, 47%) and 43% (31%, 56%). The AUCs by ROC curve analysis for CCTA and ICA bifurcation angle measurements demonstrated no significant difference (p>0.05, 0.79 vs 0.86, and 0.70 vs 0.68 at the LAD and LCx assessment, respectively).

CONCLUSION

Coronary CT angiography by bifurcation angle measurement shows significant improvement in the diagnosis of calcified plaques with diagnostic value comparable to invasive coronary angiography.

Virtual intravascular endoscopy visualization of calcified coronary plaques: a novel approach of identifying plaque features for more accurate assessment of coronary lumen stenosis

This study was conducted to investigate the feasibility of using 3D virtual intravascular endoscopy (VIE) as a novel approach for characterization of calcified coronary plaques with the aim of differentiating superficial from deep calcified plaques, thus improving assessment of coronary stenosis.A total of 61 patients with suspected coronary artery disease were included in the study. Minimal lumen diameter (MLD) was measured and compared between coronary CT angiography (CCTA) (≥64-slice) and invasive coronary angiography (ICA) with regard to the measurement bias, whereas VIE findings were correlated with CCTA with respect to the diagnostic performance of coronary stenosis and the area under the curve (AUC) by receiver-operating characteristic curve analysis (ROC).In all 3 coronary arteries, the CCTA consistently underestimated the MLD relative to the ICA (P < 0.001). On a per-vessel assessment, the sensitivity, specificity, positive predictive value, and negative predictive value and 95% confidence interval (CI) were 94% (95% CI: 61%, 100%), 27% (95% CI: 18%, 38%), 33% (95% CI: 23%, 43%), and 92% (95% CI: 74%, 99%) for CCTA, and 100% (95% CI: 89%, 100%), 85% (95% CI: 75%, 92%), 71% (95% CI: 56%, 84%), and 100% (95% CI: 95%, 100%) for VIE, respectively. The AUC by ROC analysis for VIE demonstrated significant improvement in analysis of left anterior descending calcified plaques compared with CCTA (0.99 vs 0.60, P < 0.001), with better performance in the left circumflex and right coronary arteries (0.98 vs 0.84 and 0.77 vs 0.77, respectively; P = 0.07 and P = 0.96, respectively). There are no significant differences between 64-, 128-, and 640-slice CCTA and VIE in terms of sensitivity, specificity, positive and negative predictive value in the diagnosis of coronary stenosis.This study shows the feasibility of using VIE for characterizing morphological features of calcified plaques, therefore, significantly improving assessment of coronary stenosis.

Coronary CT angiography: Diagnostic value and clinical challenges

Coronary computed tomography (CT) angiography has been increasingly used in the diagnosis of coronary artery disease due to improved spatial and temporal resolution with high diagnostic value being reported when compared to invasive coronary angiography. Diagnostic performance of coronary CT angiography has been significantly improved with the technological developments in multislice CT scanners from the early generation of 4-slice CT to the latest 320- slice CT scanners. Despite the promising diagnostic value, coronary CT angiography is still limited in some areas, such as inferior temporal resolution, motion-related artifacts and high false positive results due to severe calcification. The aim of this review is to present an overview of the technical developments of multislice CT and diagnostic value of coronary CT angiography in coronary artery disease based on different generations of multislice CT scanners. Prognostic value of coronary CT angiography in coronary artery disease is also discussed, while limitations and challenges of coronary CT angiography are highlighted.

Significance of coronary calcification for prediction of coronary artery disease and cardiac events based on 64-slice coronary computed tomography angiography

This work aims to validate the clinical significance of coronary artery calcium score (CACS) in predicting coronary artery disease (CAD) and cardiac events in 100 symptomatic patients (aged 37-87 years, mean 62.5, 81 males) that were followed up for a mean of 5 years. Our results showed that patients with CAD and cardiac events had significantly higher CACS than those without CAD and cardiac events, respectively. The corresponding data were 1450.42 ± 3471.24 versus 130 ± 188.29 (P < 0.001) for CAD, and 1558.67 ± 513.29 versus 400.46 ± 104.47 (P = 0.031) for cardiac events. Of 72 patients with CAD, cardiac events were found in 56 (77.7%) patients. The prevalence of cardiac events in our cohort was 13.3% for calcium score 0, 50% for score 11-100, 56% for score 101-400, 68.7% for score 401-1,000, and 75.0% for score >1000. Increased CACS (>100) was also associated with an increased frequency of multi-vessel disease. Nonetheless, 3 (20%) out of 15 patients with zero CACS had single-vessel disease. Significant correlation (P < 0.001) was observed between CACS and CAD on a vessel-based analysis for coronary arteries. It is concluded that CACS is significantly correlated with CAD and cardiac events.