Quantification of obstructive and nonobstructive coronary lesions by 64-slice computed tomography: a comparative study with quantitative coronary angiography and intravascular ultrasound

Computed tomography coronary angiography assessment of left main coronary artery stenosis severity

BACKGROUND

Angiographic assessment of left main coronary artery (LMCA) stenosis severity can be unreliable. In cases of ambiguity, intravascular ultrasound (IVUS) can be utilised with a minimal lumen area (MLA) of ≥6 ​mm2 an accepted threshold for safe deferral of revascularization. We sought to assess whether quantitative computer tomography coronary angiography (CTCA) measures could assist clinicians making LMCA revascularization decisions when compared with IVUS as gold standard.

METHODS

Consecutive patients undergoing IVUS assessment of angiographically intermediate LMCA stenosis were included. All patients had undergone 320-slice CTCA <90 days prior to IVUS imaging. Offline quantitative assessment of IVUS- and CT-derived measures were undertaken with the cohort divided into those with significant (s-LMCA) versus non-significant (ns-LMCA) disease using the accepted IVUS threshold.

RESULTS

Fifty-eight patients were included, with no difference in mean age (61.5 ​± ​12.2 vs. 59.7 ​± ​11.9 years, p ​= ​0.57), diabetic status (24.2% vs 16.0%, p ​= ​0.44) or other baseline demographics between groups. Patients with ns-LMCA had larger CT luminal area (8.64 ​± ​3.91 vs. 5.41 ​± ​1.54 ​mm2, p ​< ​0.001), larger minimal lumen diameter (MLD) (3.25 ​± ​0.74 vs. 2.56 ​± ​0.38 ​mm, p ​< ​0.001) and lower area stenosis (45.74 ​± ​18.10 vs. 60.93 ​± ​14.68%, p ​= ​0.001). There was a significant positive correlation between CTCA and IVUS MLA (r ​= ​0.68, p ​< ​0.001) and MLD (r ​= ​0.67, p ​< ​0.001). ROC analysis demonstrated CTCA MLA cut-off <8.29 ​mm2 provides the greatest negative predictive value and sensitivity in predicting the presence of significant LMCA disease.

CONCLUSION

CTCA derived MLA and MLD have a strong correlation with IVUS. A CTCA derived MLA cut-off <8.29 ​mm2 showed greatest clinical utility for predicting the need for further assessment, based on IVUS gold standard.

Predictors of non-calcified plaque presence and future adverse cardiovascular events in symptomatic rural Appalachian patients with a zero coronary artery calcium score

BACKGROUND

Coronary artery calcium (CAC) scoring is a proven predictor for future adverse cardiovascular events (CVE) in asymptomatic individuals. Data is emerging regarding the usefulness of non-calcified plaque (NCP) assessment on cardiac computed tomography (CCT) angiography in symptomatic patients with a zero CAC score for further risk assessment.

METHODS

A retrospective review from January 2019 to January 2022 of 696 symptomatic patients with no known CAD and a zero CAC score identified 181 patients with NCP and 515 patients without NCP by a visual assessment on CCT angiography. The primary endpoint was to identify predictors for NCP presence and adverse CVEs (death, myocardial infarction, or cerebrovascular accident) within two years.

RESULTS

Based on logistic regression, age (OR 1.039, 95% CI [1.020-1.058], p ​< ​0.001), diabetes mellitus (OR 2.192, 95% CI [1.307-3.676], p ​< ​0.003), tobacco use (OR 1.748, 95% CI [1.157-2.643], p ​< ​0.008), low-density lipoprotein cholesterol level (OR 1.009, 95% CI [1.003-1.015], p ​< ​0.002), and hypertension (OR 1.613, 95% CI [1.024-2.540], p ​< ​0.039) were found to be predictors of NCP presence. NCP patients had a higher pretest probability for CAD using the Morise risk score (p ​< ​0.001∗), with NCP detection increasing as pretest probability increased from low to high (OR 55.79, 95% CI [24.26-128.26], p ​< ​0.001∗). 457 patients (66%) reached a full two-year period after CCT angiography completion, with NCP patients noted to have shorter follow-up times and higher rates of elective coronary angiography, intervention, and CVEs. The presence of NCP (aOR 2.178, 95% CI [1.025-4.627], p ​< ​0.043) was identified as an independent predictor for future adverse CVEs when adjusted for diabetes mellitus, age, and hypertension.

CONCLUSION

NCP was identified at high rates (26%) in our symptomatic Appalachian population with no known CAD and a zero CAC score. NCP was identified as an independent predictor of future adverse CVEs within two years.

Comparison of prognosis between coronary computed tomography angiography versus invasive coronary angiography for stable coronary artery disease: a systematic review and meta-analysis

Background

The impact of using invasive coronary angiography (ICA) or coronary computed tomography angiography (CCTA) as an initial examination on the incidence of major adverse cardiovascular events (MACEs) in patients with stable coronary artery disease and the occurrence of major operation-related complications is uncertain.

Objective

This study aimed to explore the effects of ICA vs. CCTA on MACEs, all-cause death, and major operation-related complications.

Methods

A systematic search of electronic databases (PubMed and Embase) was conducted for randomized controlled trials and observational studies comparing MACEs between ICA and CCTA from January 2012 to May 2022. The primary outcome measure was analyzed using a random-effects model as a pooled odds ratio (OR). The main observations were MACEs, all-cause death, and major operation-related complications.

Results

A total of six studies, comprising 26,548 patients, met the inclusion criteria (ICA n = 8,472; CCTA n = 18,076). There were statistically significant differences between ICA and CCTA for MACE [OR 1.37; 95% confidence interval (CI), 1.06-1.77; p = 0.02], all-cause death (OR 1.56; 95% CI, 1.38-1.78; p < 0.00001), and major operation-related complications (OR 2.10; 95% CI, 1.23-3.61; p = 0.007) among patients with stable coronary artery disease. Subgroup analysis demonstrated statistically significant results in the impact of ICA or CCTA on MACEs according to the length of follow-up. Compared to CCTA, ICA was related to a higher incidence of MACEs in the subgroup with a short follow-up (≤3 years) (OR 1.74; 95% CI, 1.54-1.96; p < 0.00001).

Conclusions

Among patients with stable coronary artery disease, an initial examination with ICA was significantly associated with the risk of MACEs, all-cause death, and major procedure-related complications compared to CCTA in this meta-analysis.

Ischemia With Nonobstructive Coronary Artery Disease: Concept, Assessment, and Management

In daily clinical practice, physicians often encounter patients with angina or those with evidence of myocardial ischemia from noninvasive tests but not having obstructive coronary artery disease. This type of ischemic heart disease is referred to as ischemia with nonobstructive coronary arteries (INOCA). INOCA patients often suffer from recurrent chest pain without adequate management and are associated with poor clinical outcomes. There are several endotypes of INOCA, and each endotype should be treated based on its specific underlying mechanism. Therefore, identifying INOCA and discriminating its underlying mechanisms are important issues and of clinical interest. Invasive physiologic assessment is the first step in the diagnosis of INOCA and discriminating the underlying mechanism; additional provocation tests help physicians identify the vasospastic component in INOCA patients. Comprehensive information acquired from these invasive tests can provide a template for mechanism-specific management for patients with INOCA.

Cardiac CT blooming artifacts: clinical significance, root causes and potential solutions

This review paper aims to summarize cardiac CT blooming artifacts, how they present clinically and what their root causes and potential solutions are. A literature survey was performed covering any publications with a specific interest in calcium blooming and stent blooming in cardiac CT. The claims from literature are compared and interpreted, aiming at narrowing down the root causes and most promising solutions for blooming artifacts. More than 30 journal publications were identified with specific relevance to blooming artifacts. The main reported causes of blooming artifacts are the partial volume effect, motion artifacts and beam hardening. The proposed solutions are classified as high-resolution CT hardware, high-resolution CT reconstruction, subtraction techniques and post-processing techniques, with a special emphasis on deep learning (DL) techniques. The partial volume effect is the leading cause of blooming artifacts. The partial volume effect can be minimized by increasing the CT spatial resolution through higher-resolution CT hardware or advanced high-resolution CT reconstruction. In addition, DL techniques have shown great promise to correct for blooming artifacts. A combination of these techniques could avoid repeat scans for subtraction techniques.

Emerging Evidence on Coronary Heart Disease Screening in Kidney and Liver Transplantation Candidates: A Scientific Statement From the American Heart Association: Endorsed by the American Society of Transplantation

Coronary heart disease is an important source of mortality and morbidity among kidney transplantation and liver transplantation candidates and recipients and is driven by traditional and nontraditional risk factors related to end-stage organ disease. In this scientific statement, we review evidence from the past decade related to coronary heart disease screening and management for kidney and liver transplantation candidates. Coronary heart disease screening in asymptomatic kidney and liver transplantation candidates has not been demonstrated to improve outcomes but is common in practice. Risk stratification algorithms based on the presence or absence of clinical risk factors and physical performance have been proposed, but a high proportion of candidates still meet criteria for screening tests. We suggest new approaches to pretransplantation evaluation grounded on the presence or absence of known coronary heart disease and cardiac symptoms and emphasize multidisciplinary engagement, including involvement of a dedicated cardiologist. Noninvasive functional screening methods such as stress echocardiography and myocardial perfusion scintigraphy have limited accuracy, and newer noninvasive modalities, especially cardiac computed tomography-based tests, are promising alternatives. Emerging evidence such as results of the 2020 International Study of Comparative Health Effectiveness With Medical and Invasive Approaches-Chronic Kidney Disease trial emphasizes the vital importance of guideline-directed medical therapy in managing diagnosed coronary heart disease and further questions the value of revascularization among asymptomatic kidney transplantation candidates. Optimizing strategies to disseminate and implement best practices for medical management in the broader end-stage organ disease population should be prioritized to improve cardiovascular outcomes in these populations.

High Temporal Resolution Dual-Source Photon-Counting CT for Coronary Artery Disease: Initial Multicenter Clinical Experience

The aim of this paper is to evaluate the diagnostic image quality of spectral dual-source photon-counting detector coronary computed tomography angiography (PCD-CCTA) for coronary artery disease in a multicenter study. The image quality (IQ), assessability, contrast-to-noise ratio (CNR), Agatston score, and radiation exposure were measured. Stenoses were quantified and compared with invasive coronary angiography, if available. A total of 92 subjects (65% male, age 58 ± 14 years) were analyzed. The prevalence of significant coronary artery disease (CAD) (stenosis ≥ 50%) was 17% of all patients, the range of the Agatston score was 0−2965 (interquartile range (IQR) 0−135). The IQ was very good (one, IQR one−two), the CNR was very high (20 ± 10), and 5% of the segments were rated non-diagnostic. The IQ and assessability were higher in proximal coronary segments (p < 0.001). Agatston scores up to 600 did not significantly affect the assessability of the coronary segments (p = 0.3). Heart rate influenced assessability only at a high-pitch mode (p = 0.009). For the invasive coronary angiography (ICA) subgroup (n = nine), the diagnostic performance for CAD per segment was high (sensitivity 92%, specificity 96%), although the limited number of patients who underwent both diagnostic modalities limits the generalization of this finding at this stage. PCD-CCTA provides good image quality for low and moderate levels of coronary calcifications.

Positive remodelling of coronary arteries on computed tomography coronary angiogram: an observational study

BACKGROUND

Coronary artery disease (CAD) due to atherosclerosis is projected to be the leading cause of morbidity and mortality worldwide until 2040. CAD affects approximately 2.6 million people in the United Kingdom (UK), and 1 in 4 of them do not experience any symptoms.

AIMS

The aim of this study was to assess the characteristics and outcomes of patients with plaque features of positive remodelling (PR) on their computed tomography coronary angiogram (CTCA) images.

METHODS

Patients who were referred for CTCA from June 2018 to January 2020 were retrospectively identified. Patients underwent prospective, gated 128-slice dual-source CTCA. Patients with PR were compared to those without PR for demographics and outcomes.

RESULTS

A total of 861 patients were included in our study; 241 (28%) had PR, and 620 (72%) had no PR. Patients with PR were older (PR: 63.9±11.0 years vs no PR: 62.1±11.2 years; p=0.04), more likely to be male (PR: 65.6% vs no PR: 55.8%; p=0.01) and underwent coronary angiography more frequently (PR: 25.7% vs no PR: 14.4%; p<0.01). There were also significant increases in subsequent acute coronary syndrome (ACS) events (PR: 2.5% vs no PR: 0.0%; p<0.01) and the need for revascularisation therapy (PR: 15.4% vs no PR: 7.8%; p<0.01) in patients with PR despite being on statins (not a high dose). There was no difference in all-cause mortality.

CONCLUSIONS

Detection of PR on CTCA is a reliable prognostic indicator of future cardiovascular events and presents a valuable opportunity for initiation of aggressive primary prevention therapy.

Effect of guidewire insertion in fractional flow reserve procedure for real geometry using computational fluid dynamics

BACKGROUND

Coronary artery disease is an abnormal contraction of the heart supply blood vessel. It limits the oxygenated blood flow to the heart. Thus, diagnosing its severity helps physicians to select the appropriate treatment plan. Fractional flow reserve (FFR) is the most accurate method to pinpoint the stenosis severity. However, inserting the guidewire across stenosis may cause a false overestimation of severity.

METHODS

To estimate the errors due to guidewire insertion, reconstructed three-dimensional coronary artery geometry from a patient-specific scan is used. A comprehensive three-dimensional blood flow model is developed. Blood is considered non-Newtonian and the flow is pulsatile. The model is numerically simulated using realistic boundary conditions.

RESULTS

The FFR value is calculated and compared with the actual flow ratio. Additionally, the ratio between pressure drop and distal dynamic pressure (CDP) is studied. The obtained results for each case are compared and analyzed with the case without a guidewire. It was found that placing the guidewire leads to overestimating the severity of moderate stenosis. It reduces the FFR value from 0.43 to 0.33 with a 23.26% error compared to 0.44 actual flow ratio and the CDP increases from 5.31 to 7.2 with a 35.6% error. FFR value in mild stenosis does not have a significant change due to placing the guidewire. The FFR value decreases from 0.83 to 0.82 compared to the 0.83 actual flow ratio.

CONCLUSION

Consequently, physicians should consider these errors while deciding the treatment plan.

Recent Trends in Artificial Intelligence-Assisted Coronary Atherosclerotic Plaque Characterization

Coronary artery disease is a major cause of morbidity and mortality worldwide. Its underlying histopathology is the atherosclerotic plaque, which comprises lipid, fibrous and—when chronic—calcium components. Intravascular ultrasound (IVUS) and intravascular optical coherence tomography (IVOCT) performed during invasive coronary angiography are reference standards for characterizing the atherosclerotic plaque. Fine image spatial resolution attainable with contemporary coronary computed tomographic angiography (CCTA) has enabled noninvasive plaque assessment, including identifying features associated with vulnerable plaques known to presage acute coronary events. Manual interpretation of IVUS, IVOCT and CCTA images demands scarce physician expertise and high time cost. This has motivated recent research into and development of artificial intelligence (AI)-assisted methods for image processing, feature extraction, plaque identification and characterization. We performed parallel searches of the medical and technical literature from 1995 to 2021 focusing respectively on human plaque characterization using various imaging modalities and the use of AI-assisted computer aided diagnosis (CAD) to detect and classify atherosclerotic plaques, including their composition and the presence of high-risk features denoting vulnerable plaques. A total of 122 publications were selected for evaluation and the analysis was summarized in terms of data sources, methods—machine versus deep learning—and performance metrics. Trends in AI-assisted plaque characterization are detailed and prospective research challenges discussed. Future directions for the development of accurate and efficient CAD systems to characterize plaque noninvasively using CCTA are proposed.

Prevalence and Functional Implication of Silent Coronary Artery Disease in Marathon Runners Over 40 Years of Age: The MATCH-40 Study

BACKGROUND

Marathon participation is becoming increasingly popular among individuals ≥40 years of age. Little is known about the prevalence of subclinical coronary artery disease (CAD) and corresponding ischemia in this patient population. The study objectives are: (1) to characterize the prevalence of silent CAD in marathoners ≥ 40 years old using cardiac computed tomography angiography (CCT); and (2) if subclinical CAD was detected, to determine the functional significance of occult lesions by stress echocardiography (SE).

METHODS

Marathoners aged ≥ 40 years who completed a full marathon between 2018 and 2019 were recruited to undergo a prospective CCT. Coronary artery stenosis was graded as zero, mild (1%-49%), moderate (50%-69%), or severe (> 70%). All study participants diagnosed with mild-to-severe atherosclerotic CAD on CCT further underwent functional imaging with exercise treadmill SE.

RESULTS

A total of 65 individuals (53 ± 7 years, 65% males, 24 ± 3 kg/m2) underwent a prospective CCT within 12 months of marathon completion. Of the total study population, 13 participants (20%) were diagnosed with CAD, of whom 10 (77%) had mild disease, 1 (8%) had moderate disease, and 2 (15%) had severe disease by CCT. Despite the identification of subclinical CAD on CCT, none of the 13 patients had any evidence of inducible ischemia on SE.

CONCLUSIONS

This is the first study to incorporate both CCT and SE in the evaluation of subclinical CAD in marathoners ≥40 years old. Although the overall prevalence of anatomic CAD was 20%, there was no evidence of functional ischemia in this highly competitive cohort.

Pericoronary adipose tissue CT attenuation and volume: Diagnostic performance for hemodynamically significant stenosis in patients with suspected coronary artery disease

OBJECTIVES

The aim of this study was to investigate the diagnostic abilities of both pericoronary adipose tissue (PCAT) CT attenuation and volume for the predication hemodynamic significance of coronary artery stenosis as evaluated by fractional flow reserve (FFR).

METHODS

Patients with ≥ 30 % in at least 1 major epicardial coronary artery were retrospectively included. Furthermore, all eligible patients underwent coronary computed tomography angiography (CCTA) and invasive coronary angiography (ICA) as well as FFR within 1 month. PCAT CT attenuation and volume around ischemic and non-ischemic coronary stenosis were measured and compared. The diagnostic accuracy of PCAT CT attenuation and volume for the identification of hemodynamically significant stenosis was determined against the reference standard of FFR ≤ 0.80.

RESULTS

A total of 61 patients (mean age, 57.8 years ± 11.8) with 77 vessels were included. Average PCAT CT attenuation of all vessels was -70.3 ± 7.4 HU. PCAT CT attenuation in coronary arteries with hemodynamically significant stenosis (FFR ≤ 0.80) (-65.6 ± 5.9 HU) was significantly higher than those with FFR > 0.80 (-75.3 ± 5.4 HU; p = 0.000). There was a strong correlation between FFR and PCAT CT attenuation (r = 0.64, p < 0.001). However, no significant difference in PCAT volume was observed between FFR ≤ 0.8 (5.0 ± 3.5 cm³) and FFR > 0.80 (5.5 ± 3.7 cm³, p = 0.511). The diagnostic accuracy was significantly higher in the combination of CCTA and PCAT CT attenuation compared with CCTA alone (area under the curve: 0.869 vs. 0.569, p < 0.001).

CONCLUSIONS

PCAT CT attenuation but not volume was related to the hemodynamic significance of coronary artery stenosis. For the patients with suspected coronary artery disease, after adding of PCAT CT attenuation to CCTA, the diagnostic ability for the identification of ischemic coronary stenosis was significantly improved.

A simple coronary blood flow model to study the collateral flow index

In this work, we present a novel modeling framework to investigate the effects of collateral circulation into the coronary blood flow physiology. A prototypical model of the coronary tree, integrated with the concept of Collateral Flow Index (CFI), is employed to gain insight about the role of model parameters associated with the collateral circuitry, which results in physically-realizable solutions for specific CFI data. Then, we discuss the mathematical feasibility of pressure-derived CFI, anatomical implications and practical considerations involving the estimation of model parameters in collateral connections. A sensitivity analysis is carried out, and the investigation of the impact of the collateral circulation on FFR values is also addressed.

Predictors of abnormality in thallium myocardial perfusion scans for type 2 diabetes

Type 2 diabetes mellitus (T2DM) increases coronary artery disease (CAD) risk. In this study, we used T2DM clinical variables to predict abnormality in thallium-201 myocardial perfusion scans (Th-201 scans). These clinical variables were summed stress score (SSS), summed rest score, and summed difference score (SDS), with data obtained from 368 male and 428 female participants with T2DM. Multiple linear regression results were as follows. In male participants, body mass index (BMI) and creatinine (Cr) were associated with SSS (β = 0.224, p < 0.001; β = 0.140, p = 0.022, respectively), and only BMI was associated with SDS (β = 0.174, p = 0.004). In female participants, BMI and high-density lipoprotein cholesterol level were associated with SSS (β = 0.240, p < 0.001; β =  - 0.120, p = 0.048, respectively), and only BMI was correlated with SDS (β = 0.123, p = 0.031). Our multivariate logistic regression indicated that in male and female participants, BMI was the only independent indicator of high SSS (SSS ≥ 9). In this study, we demonstrated that male patients have a higher SSS and SDS than female patients do in Th-201 scans for T2DM in a Chinese population. For male and female patients, BMI was the strongest predictor of abnormality in Th-201 scans. Our results can help clinicians identify patients with T2DM at high risk of CAD.

Exercise Electrocardiography and Computed Tomography Coronary Angiography for Patients With Suspected Stable Angina Pectoris: A Post Hoc Analysis of the Randomized SCOT-HEART Trial

Importance

Recent European guidance supports a diminished role for exercise electrocardiography (ECG) in the assessment of suspected stable angina.

Objective

To evaluate the utility of exercise ECG in contemporary practice and assess the value of combined functional and anatomical testing.

Design, Setting, and Participants

This is a post hoc analysis of the Scottish Computed Tomography of the Heart (SCOT-HEART) open-label randomized clinical trial, conducted in 12 cardiology chest pain clinics across Scotland for patients with suspected angina secondary to coronary heart disease. Between November 18, 2010, and September 24, 2014, 4146 patients aged 18 to 75 years with stable angina underwent clinical evaluation and 1417 of 1651 (86%) underwent exercise ECG prior to randomization. Statistical analysis was conducted from October 10 to November 5, 2019.

Interventions

Patients were randomized in a 1:1 ratio to receive standard care plus coronary computed tomography (CT) angiography or to receive standard care alone. The present analysis was limited to the 3283 patients who underwent exercise ECG alone or in combination with coronary CT angiography.

Main Outcomes and Measures

The primary clinical end point was death from coronary heart disease or nonfatal myocardial infarction at 5 years.

Results

Among the 3283 patients (1889 men; median age, 57.0 years [interquartile range, 50.0-64.0 years]), exercise ECG had a sensitivity of 39% and a specificity of 91% for detecting any obstructive coronary artery disease in those who underwent subsequent invasive angiography. Abnormal results of exercise ECG were associated with a 14.47-fold (95% CI, 10.00-20.41; P < .001) increase in coronary revascularization at 1 year and a 2.57-fold (95% CI, 1.38-4.63; P < .001) increase in mortality from coronary heart disease death at 5 years or in cases of nonfatal myocardial infarction at 5 years. Compared with exercise ECG alone, results of coronary CT angiography had a stronger association with 5-year coronary heart disease death or nonfatal myocardial infarction (hazard ratio, 10.63; 95% CI, 2.32-48.70; P = .002). The greatest numerical difference in outcome with CT angiography compared with exercise ECG alone was observed for those with inconclusive results of exercise ECG (5 of 285 [2%] vs 13 of 283 [5%]), although this was not statistically significant (log-rank P = .05).

Conclusions and Relevance

This study suggests that abnormal results of exercise ECG are associated with coronary revascularization and the future risk of adverse coronary events. However, coronary CT angiography more accurately detects coronary artery disease and is more strongly associated with future risk compared with exercise ECG.

Trial Registration

ClinicalTrials.gov Identifier: NCT01149590.

Analysis of the effect of guidewire position on stenosis diagnosis using computational fluid dynamics

BACKGROUND

Fractional flow reserve is an accurate method for diagnosing stenosis. The difficulty in using this procedure lies in placing the guidewire precisely at the blood vessel centerline. Owing to the long distance between the insertion point and the stenosis, a guidewire inclination can occur. Therefore, the main objective of this study is to investigate how the measured pressure in a blood vessel varies with the guidewire position.

METHODS

A three-dimensional model of blood flow is developed and numerically simulated. Two positions and two inclination angles from the blood vessel centerline and three throat diameters are investigated. The predicted results are validated using the available experimental data. The predicted results and actual measurements are observed to agree well with each other.

RESULTS

The pressure drop coefficient (CDP) increases because of guidewire insertion. When the guidewire is placed at inclined positions in moderate stenosis, the values of CDP are 66 and 68, depending on the inclination angle; the errors in CDP are 69% and 76%, respectively. At a high flow rate, the errors are reduced to 67% and 70%, respectively. The error in the CDP ranges from 42% to 61% when the guidewire is placed parallel to the centerline. For severe stenosis, the CDP is nearly the same at all positions and varies between 240 and 250; without a guidewire, the CDP is 163.

CONCLUSIONS

The findings confirmed that practitioners should be aware of the guidewire position during the operation. The displacement of the guidewire should be estimated, and the corresponding error must be considered.

State of the art of coronary computed tomography angiography

OBJECTIVES

The aim of this paper is to evaluate contrast media (CM) bolus geometry and opacification patterns in the coronary arteries with particular focus on patient, scanner and safety considerations during coronary computed tomography angiography (CCTA).

KEY FINDINGS

The rapid evolution of computed tomography (CT) technology has seen this imaging modality challenge conventional coronary angiography in the evaluation of coronary artery disease. Increases in spatial and temporal resolutions have enabled CCTA to become the modality of choice when evaluating the coronary vascular tree as an alternative in the diagnostic algorithm for acute chest pain. However, these new technologic improvements in scanner technology have imposed new challenges for the optimisation of CM delivery and image acquisition strategies.

CONCLUSION

Understanding basic CM-imaging principles is essential for designing optimal injection protocols according to each specific clinical scenario, independently of scanner technology.

IMPLICATIONS FOR PRACTICE

With rapid advances in CT scanner technology including faster scan acquisitions, the risk of poor opacification of coronary vasculature increases significantly. Therefore, awareness of CM delivery protocols is paramount to consistently provide optimal image quality at a low radiation dose.

Diagnostic Accuracy of a Novel On-site Virtual Fractional Flow Reserve Parallel Computing System

PURPOSE

To evaluate the diagnostic accuracy of a novel on-site virtual fractional flow reserve (vFFR) derived from coronary computed tomography angiography (CTA).

MATERIALS AND METHODS

We analyzed 100 vessels from 57 patients who had undergone CTA followed by invasive FFR during coronary angiography. Coronary lumen segmentation and three-dimensional reconstruction were conducted using a completely automated algorithm, and parallel computing based vFFR prediction was performed. Lesion-specific ischemia based on FFR was defined as significant at ≤0.8, as well as ≤0.75, and obstructive CTA stenosis was defined that ≥50%. The diagnostic performance of vFFR was compared to invasive FFR at both ≤0.8 and ≤0.75.

RESULTS

The average computation time was 12 minutes per patient. The correlation coefficient (r) between vFFR and invasive FFR was 0.75 [95% confidence interval (CI) 0.65 to 0.83], and Bland-Altman analysis showed a mean bias of 0.005 (95% CI -0.011 to 0.021) with 95% limits of agreement of -0.16 to 0.17 between vFFR and FFR. The accuracy, sensitivity, specificity, positive predictive value, and negative predictive value were 78.0%, 87.1%, 72.5%, 58.7%, and 92.6%, respectively, using the FFR cutoff of 0.80. They were 87.0%, 95.0%, 80.0%, 54.3%, and 98.5%, respectively, with the FFR cutoff of 0.75. The area under the receiver-operating characteristics curve of vFFR versus obstructive CTA stenosis was 0.88 versus 0.61 for the FFR cutoff of 0.80, respectively; it was 0.94 versus 0.62 for the FFR cutoff of 0.75.

CONCLUSION

Our novel, fully automated, on-site vFFR technology showed excellent diagnostic performance for the detection of lesion-specific ischemia.

Prognostic value of normal and non-obstructive coronary artery disease based on CT angiography findings. A 12 month follow up study

Introduction: The advent of multi-slice computed tomography (CT) technology has provided a new promising tool for non-invasive assessment of the coronary arteries. However, as the prognostic outcome of patients with normal or non-significant finding on computed tomography coronary angiography (CTCA) is not well-known, this study was aimed to determine the prognostic value of CTCA in patients with either normal or non-significant CTCA findings.

Methods: This retrospective cohort study was performed on patients who were referred for CTCA to the hospital. 527 patients with known or suspected coronary artery disease (CAD), who had undergone CTCA within one year were enrolled. Among them, data of 465 patients who had normal (no stenosis, n=362) or non-significant CTCA findings (stenosis <50% of luminal narrowing, n=103) were analyzed and prevalence of cardiac risk factors and major adverse cardiac events (MACE) were compared between these groups. In addition, a correlation between these factors and the number of involved coronary arteries was also determined.

Results: After a mean follow-up duration of 13.11±4.63 months, all cases were alive except for three patients who died by non-cardiac events. Prevalence of MACE was 0% and 3% in normal CTCA group and non-significant groups, respectively. There was no correlation found between the number of involved coronary arteries and the prevalence of MACE (P = 0.57).

Conclusion: A normal CTCA could be associated with extremely low risk of MACE over the first year after the initial imaging, whereas non-significant obstruction in coronary arteries may be associated with a slightly higher risk of MACE.

Acute myocardial infarction in pregnancy: Current diagnosis and management approaches

Acute myocardial infarction during pregnancy is a very uncommon condition; atherosclerotic coronary artery disease is by far the most common cause of an acute coronary syndrome in the general population. The causes of an acute coronary syndrome in the pregnant patient are wide and varied. This has important implications with respect to the diagnosis of the etiology and the subsequent management of the cause of the acute coronary syndrome. There are a number of diagnostic tools for the diagnosis of coronary artery disease but it is important to understand their role in pregnant patients. Spontaneous coronary artery dissection is one of the most common causes of acute coronary syndrome in pregnant patients. Understanding its pathophysiology and knowing the natural history of this condition is paramount in the management of this condition. The article also lists the various therapeutic modalities available to the clinician faced with an acute coronary syndrome in the pregnant patient. Finally, we discuss the delivery of the baby and post partum care of these complex patients.

Molecular Imaging of Factor XIII Activity for the Early Detection of Mouse Coronary Microvascular Disease

Coronary microvascular disease (MVD) remains a major clinical problem due to limited mechanistic understanding and a challenging diagnosis. In the present study we evaluated the utility of targeted imaging of active factor XIII (FXIII) for detection of coronary MVD associated with thrombus. We hypothesized that a high specificity and sensitivity FXIII targeted radiolabeled probe can serve as a biomarker for cross-linked thrombi in the microvasculature, and thus an indicator for underlying coronary MVD. To evaluate this approach, a coronary MVD model was established for local induction of singlet oxygen and reactive oxygen species (ROS) via a photochemical reaction (PCR).

Methods: PCR was used to induce endothelial injury and microthrombi via focal over-production of ROS only in the coronary microvasculature. Oxidative stress was initially evaluated in primary coronary endothelial cells to optimize parameters of PCR, which were then translated to in vivo experiments. To develop the coronary MVD model, 64 mice were assigned to one of four groups after thoracotomy: 1) sham control; 2) rose bengal; 3) green light; or 4) their combination. Following interventions, the mice underwent transmission electron microscopy, fluorescent myocardial perfusion, coronary angiography, and immunohistochemical staining. Echocardiography (n = 12) and gene expression (n = 10) studies were also performed after MVD induction to monitor serial changes in cardiac function and explore possible mechanisms. To diagnose early onset MVD, FXIII radioactivity was assessed in 104 mice using ex vivo gamma well counting (GWC) and in 14 mice using in vivo serial single photon emission computed tomography / computed tomography (SPECT/CT) imaging of a FXIII targeted technetium-labeled probe (^99mTc-NC100668).

Results:In vitro experiments demonstrated that photosensitizer concentration and light illumination time were critical parameters for PCR. In vivo experiments demonstrated manifestations of clinical MVD, including endothelial damage, a “no flow zone,” arteriole rarefaction with patent epicardial coronary arteries, infiltration of inflammatory cells in the PCR-treated region, and preserved cardiac function. Gene expression also demonstrated a pro-thrombotic and impaired fibrinolytic status. In the early stages of MVD, enhanced FXIII activity was confirmed within the MVD region using GWC and in vivo SPECT/CT imaging.

Conclusion: Our results demonstrate that molecular imaging of FXIII activity may allow for early detection of coronary MVD associated with thrombus, in a novel pre-clinical model.

Prediction of Thin-Walled Areas of Unruptured Cerebral Aneurysms through Comparison of Normalized Hemodynamic Parameters and Intraoperative Images

Object

Rupture of a cerebral aneurysm occurs mainly in a thin-walled area (TWA). Prediction of TWAs would help to assess the risk of rupture and select appropriate treatment strategy. There are several limitations of current prediction techniques for TWAs. To predict TWAs more accurately, HP should be normalized to minimize the influence of analysis conditions, and the effectiveness of normalized, combined hemodynamic parameters (CHPs) should be investigated with help of the quantitative color analysis of intraoperative images.

Methods

A total of 21 unruptured cerebral aneurysms in 19 patients were analyzed. A normalized CHP was newly suggested as a weighted average of normalized wall shear stress (WSS) and normalized oscillatory shear index (OSI). Delta E from International Commission on Illumination was used to more objectively quantify color differences in intraoperative images.

Results

CFD analysis results indicated that WSS and OSI were more predictive of TWAs than pressure (P<.001, P=.187, P=.970, respectively); these two parameters were selected to define the normalized CHP. The normalized CHP became more statistically significant (P<.001) as the weighting factor of normalized WSS increased and that of normalized OSI decreased. Locations with high CHP values corresponded well to those with high Delta E values (P<.001). Predicted TWAs based on the normalized CHP showed a relatively good agreement with intraoperative images (17 in 21 cases, 81.0%).

Conclusion

100% weighting on the normalized WSS produced the most statistically significant result. The normalization scheme for WSS and OSI suggested in this work was validated using quantitative color analyses, rather than subjective judgments, of intraoperative images, and it might be clinically useful for predicting TWAs of unruptured cerebral aneurysms. The normalization scheme would also be integrated into further fluid-structure interaction analysis for more reliable estimation of the risk of aneurysm rupture.

A phantom based evaluation of vessel lumen area quantification for coronary CT angiography

Coronary computed tomography (CT) angiography is a noninvasive method for visualizing coronary artery disease. However, coronary CT angiography is limited in assessment of stenosis severity by the partial volume effect and calcification. Therefore, an accurate method for assessment of stenosis severity is needed. A 10 cm diameter cylindrical Lucite phantom with holes in the range of 0.4-4.5 mm diameter was fitted in a chest phantom. The holes were filled with an iodine solution of 8 mg/mL. To simulate coronary artery disease, different levels of stenosis were created by inserting Lucite rods into the holes with diameter range of 2-4.5 mm. The resulting lumen cross sectional areas ranged from 1.4 to 12.3 mm². To simulate arterial calcification, calcium hydroxyapatite rods were inserted into the holes with diameter range of 2-4.5 mm. Images of the phantoms were acquired at 100 kVp using a 320-slice CT scanner. A maual and a semi-automated technique based on integrated Hounsfield units was used to calculate vessel cross-sectional area. There was an excellent correlation between the measured and the known cross-sectional area for both normal and stenotic vessels using the manual and the semi-automated techniques. However, the overall measurement error for the manual method was more than twice as compared with the integrated HU technique. Determination of vessel lumen area using the semi-automated integrated Hounsfield unit technique yields more than a factor of two improvement in precision and accuracy as compared to the existing manual technique for vessels with and without stenosis. This technique can also be used to accurately measure arterial cross-sectional area in the presence of coronary calcification.

The clinical evaluation of the CADence device in the acoustic detection of coronary artery disease

The noninvasive detection of turbulent coronary flow may enable diagnosis of significant coronary artery disease (CAD) using novel sensor and analytic technology. Eligible patients (n = 1013) with chest pain and CAD risk factors undergoing nuclear stress testing were studied using the CADence (AUM Cardiovascular Inc., Northfield MN) acoustic detection (AD) system. The trial was designed to demonstrate non-inferiority of AD for diagnostic accuracy in detecting significant CAD as compared to an objective performance criteria (sensitivity 83% and specificity 80%, with 15% non-inferiority margins) for nuclear stress testing. AD analysis was blinded to clinical, core lab-adjudicated angiographic, and nuclear data. The presence of significant CAD was determined by computed tomographic (CCTA) or invasive angiography. A total of 1013 subjects without prior coronary revascularization or Q-wave myocardial infarction were enrolled. Primary analysis was performed on subjects with complete angiographic and AD data (n = 763) including 111 subjects (15%) with severe CAD based on CCTA (n = 34) and invasive angiography (n = 77). The sensitivity and specificity of AD were 78% (p = 0.012 for non-inferiority) and 35% (p < 0.001 for failure to demonstrate non-inferiority), respectively. AD results had a high 91% negative predictive value for the presence of significant CAD. AD testing failed to demonstrate non-inferior diagnostic accuracy as compared to the historical performance of a nuclear stress OPC due to low specificity. AD sensitivity was non-inferior in detecting significant CAD with a high negative predictive value supporting a potential value in excluding CAD.

Diagnostic accuracy of multi-slice computed tomography in identifying lesion characteristics in coronary total occlusion

We performed this study to compare the sensitivity and specificity of multi-slice computed tomography (MSCT) to coronary angiography (CA) in detecting coronary total occlusion (CTO) lesion characteristics. Moreover, we analyzed the association between these characteristics and the risk of revascularization failure. Fifty patients with confirmed CTO diagnosis were tried for revascularization using the antegrade (all 50) or retrograde (in failed nine antegrade interventions) approaches. Each patient underwent CA and MSCT before the intervention and data from both modalities were compared using the SPSS software. Successful revascularization occurred in 36 (72%) and 6 (66.7%) patients of the antegrade and retrograde groups, respectively. Compared to CA, MSCT exhibited high sensitivity in detecting CTO segment calcification (100%), size of the affected vessel (100%, area under the curve [AUC] = 0.82), distal filling of the affected segment (97.7%) and side-branching at the CTO segment (93.3%). However, it had lower sensitivity in detecting collaterals (75%) and the length of the affected segment (87.5%, AUC = 0.77). According to MSCT data, increased occlusion length > 18 mm (p = 0.01), atherosclerotic vessel wall (p = 0.02), small distal vessel size ≤ 2.75 mm (p = 0.002), proximal side-branching (p = 0.01) and calcification of the proximal cap (p = 0.007) or distal stump (p = 0.01) were associated with an increased risk of revascularization failure. MSCT exhibited high sensitivity in identifying several CTO lesion characteristics, such as lesional calcification and size of the affected vessel. However, further research is needed to improve the diagnostic accuracy of this modality and define the predictors of revascularization failure in CTO patients.

Changes in Coronary Plaque Volume: Comparison of Serial Measurements on Intravascular Ultrasound and Coronary Computed Tomographic Angiography

Serial measurements of coronary plaque volume have been used to evaluate drug efficacy in atherosclerotic progression. However, the usefulness of computed tomography for this purpose is unknown. We investigated whether the change in total plaque volume on coronary computed tomographic angiography is associated with the change in segment plaque volume on intravascular ultrasound. We prospectively enrolled 11 consecutive patients (mean age, 56.3 ± 5 yr; 6 men) who were to undergo serial invasive coronary angiographic examinations with use of grayscale intravascular ultrasound and coronary computed tomography, performed <180 days apart at baseline and from 1 to 2 years later. Subjects underwent 186 serial measurements of total plaque volume on coronary computed tomography and 22 of segmental plaque volume on intravascular ultrasound. We used semiautomated software to examine percentage relationships and changes between total plaque and segmental plaque volumes. No significant correlations were found between percentages of total coronary and segment coronary plaque volume, nor between normalized coronary plaque volume. However, in the per-patient analysis, there were strong correlations between the imaging methods for changes in total coronary and segment coronary plaque volume (r=0.62; P=0.04), as well as normalized plaque volume (r=0.82; P=0.002). Per-patient change in plaque volume on coronary computed tomography is significantly associated with that on intravascular ultrasound. Computed tomographic angiography may be safer and more widely available than intravascular ultrasound for evaluating atherosclerotic progression in coronary arteries. Larger studies are warranted.

Blooming Artifact Reduction in Coronary Artery Calcification by A New De-blooming Algorithm: Initial Study

The aim of this study was to investigate the use of de-blooming algorithm in coronary CT angiography (CCTA) for optimal evaluation of calcified plaques. Calcified plaques were simulated on a coronary vessel phantom and a cardiac motion phantom. Two convolution kernels, standard (STND) and high-definition standard (HD STND), were used for imaging reconstruction. A dedicated de-blooming algorithm was used for imaging processing. We found a smaller bias towards measurement of stenosis using the de-blooming algorithm (STND: bias 24.6% vs 15.0%, range 10.2% to 39.0% vs 4.0% to 25.9%; HD STND: bias 17.9% vs 11.0%, range 8.9% to 30.6% vs 0.5% to 21.5%). With use of de-blooming algorithm, specificity for diagnosing significant stenosis increased from 45.8% to 75.0% (STND), from 62.5% to 83.3% (HD STND); while positive predictive value (PPV) increased from 69.8% to 83.3% (STND), from 76.9% to 88.2% (HD STND). In the patient group, reduction in calcification volume was 48.1 ± 10.3%, reduction in coronary diameter stenosis over calcified plaque was 52.4 ± 24.2%. Our results suggest that the novel de-blooming algorithm could effectively decrease the blooming artifacts caused by coronary calcified plaques, and consequently improve diagnostic accuracy of CCTA in assessing coronary stenosis.

Evolution of Biomarkers of Atherogenic Risk in Liver Transplantation Recipients

BACKGROUND

Cardiovascular disease is a major contributing factor to long-term mortality after liver transplantation (LT).

METHODS

This study evaluated the evolution of atherogenic risk in liver transplant recipients (LTRs). Thirty-six subjects were prospectively enrolled at 12 months and followed for 48 months after liver transplantation. Serum biomarkers of endothelial dysfunction (sICAM-1 and sVCAM-1), chronic inflammation (serum amyloid A), and oxidative stress (myeloperoxidase) were measured at 12 and 48 months after LT. Additionally, at 12 months all patients underwent a cardiac computed tomography (CT) scan and a coronary artery calcium score (CACS).

RESULTS

The prevalence of risk factors of metabolic syndrome (MS) increased over the course of the study. The patients' sVCAM-1 and sICAM-1 increased from 1.82 ± 0.44 ng/mL to 9.10 ± 5.82 ng/mL (P < .001) and 0.23 ± 0.09 ng/mL to 2.7 ± 3.3 ng/mL, respectively from month 12 to 48. Serum myeloperoxidase increased from 0.09 ± 0.07 ng/mL to 3.46 ± 3.92 ng/mL (P < .001) over the course of the study. Serum amyloid A also increased from 21.4 ± 40.7 ng/mL at entry to 91.5 ± 143.6 ng/mL at end of study (P < .001).

CONCLUSION

No association between these biomarkers and MS was noted. The cardiac CT revealed mild and moderate disease in 19% and 25% of the cohort, respectively. No association between serum biomarkers and CACS was noted. Serum biomarkers of atherogenic risk increase rapidly in LTRs and precede coronary plaques.

Measurements of Lumen Areas and Diameters of Proximal and Middle Coronary Artery Segments in Subjects Without Coronary Atherosclerosis

There are plenty of data on morphology and lumen dimensions of diseased coronary arteries. However, information on normal coronary vessel anatomy is scarce. We provided computed tomography angiography-derived reference values of lumen dimensions in proximal and middle coronary segments in a healthy population with respect to gender and vessel dominance. Consecutive 2,849 computed tomography angiography examinations were reviewed to identify 201 subjects (77 men, patient age 50 ± 13 years) whose coronary arteries were free from any sign of atherosclerosis (calcium score 0, no detectable plaque). For all proximal and middle coronary segments, lumen areas (LAs) and lumen diameters were measured. Coronary vessel segmentation and dominance pattern were defined using the Syntax Score. Normal values of LAs and lumen diameters were significantly smaller for women compared with men except for the proximal right coronary artery and the left main coronary artery (LMCA) (20.2 ± 6.6 mm² vs 23.0 ± 6.1 mm², p = 0.0003, and 5.0 ± 0.8 mm vs 5.4 ± 0.7 mm, p = 0.0001). The lower limit of normal for the LMCA (defined as mean LA - 2 standard deviations) equaled 7.0 and 10.8 mm² for women and men, respectively. Subjects with left (vs right) coronary dominance had significantly larger areas and diameters of the LMCA (26.2 ± 9.2 mm² vs 20.7 ± 6.0 mm², p = 0.0017, and 5.7 ± 1.0 mm vs 5.1 ± 0.7 mm, p = 0.0017, respectively) and proximal left circumflex (13.8 ± 2.7 mm² vs 10.4 ± 3.8 mm², p = 0.0001, and 4.2 ± 0.4 mm vs 3.6 ± 0.7 mm, p = 0.0001, respectively) and smaller areas and diameters of the proximal right coronary artery (7.1 ± 2.0 mm² vs 13.3 ± 3.6 mm², p <0.0001, and 3.0 ± 0.4 mm vs 4.1 ± 0.6 mm, p <0.0001, respectively). In conclusion, gender and coronary artery dominance pattern significantly impact normal LAs and dimensions in subjects without coronary atherosclerosis.

Molecular imaging of atherosclerosis: spotlight on Raman spectroscopy and surface-enhanced Raman scattering

To accurately predict atherosclerotic plaque progression, a detailed phenotype of the lesion at the molecular level is required. Here, we assess the respective merits and limitations of molecular imaging tools. Clinical imaging includes contrast-enhanced ultrasound, an inexpensive and non-toxic technique but with poor sensitivity. CT benefits from high spatial resolution but poor sensitivity coupled with an increasing radiation burden that limits multiplexing. Despite high sensitivity, positron emission tomography and single-photon emission tomography have disadvantages when applied to multiplex molecular imaging due to poor spatial resolution, signal cross talk and increasing radiation dose. In contrast, MRI is non-toxic, displays good spatial resolution but poor sensitivity. Preclinical techniques include near-infrared fluorescence (NIRF), which provides good spatial resolution and sensitivity; however, multiplexing with NIRF is limited, due to photobleaching and spectral overlap. Fourier transform infrared spectroscopy and Raman spectroscopy are label-free techniques that detect molecules based on the vibrations of chemical bonds. Both techniques offer fast acquisition times with Raman showing superior spatial resolution. Raman signals are inherently weak; however, leading to the development of surface-enhanced Raman spectroscopy (SERS) that offers greatly increased sensitivity due to using metallic nanoparticles that can be functionalised with biomolecules targeted against plaque ligands while offering high multiplexing potential. This asset combined with high spatial resolution makes SERS an exciting prospect as a diagnostic tool. The ongoing refinements of SERS technologies such as deep tissue imaging and portable systems making SERS a realistic prospect for translation to the clinic.

A multifunctional CT technology: Reality or illusion for patient risk assessment?

A high-speed, multi-slice coronary computed tomography (CT) imaging has emerged as a promising or clinically available multifunctional technique for the assessment of myocardial ischemia, viability, ischemia-induced cardiac dysfunction, and coronary atherosclerotic alterations in patients with suspected or known coronary artery disease. Despite several technical issues remain to be resolved, cardiac CT imaging will have a reality as a multifunctional modality for guiding physicians in better decision-making for favorable clinical outcomes in patients with suspected coronary artery disease, provided that this imaging technology can contribute to characterization and localization of high-risk coronary atherosclerosis in combination with the quantitative evaluation of functional myocardial ischemia.

Evaluation of Plaque Morphology by 64-Slice Coronary Computed Tomographic Angiography Compared to Intravascular Ultrasound in Nonocclusive Segments of Coronary Arteries

RATIONALE AND OBJECTIVES

Although intravascular ultrasound (IVUS) is the current gold standard for plaque characterization, noninvasive coronary computed tomographic angiography (CCTA) requires further evaluation. The ability to detect plaque morphology by CCTA remains unclear. The purpose of this study was to evaluate the diagnostic accuracy of CCTA for plaque detection and morphology.

MATERIALS AND METHODS

Thirty-one patients underwent cardiac catheterization with IVUS and CCTA. The presence of plaque was evaluated by both modalities in nonocclusive segments (<50% stenosis) of the left anterior descending artery, left circumflex artery, and right coronary artery. Plaque morphology was classified as (1) normal, (2) soft or fibrous, (3) fibrocalcific, or (4) calcific. Results by IVUS and CCTA were compared blindly on a segment-to-segment basis with subgroup analysis based on CCTA tube voltage.

RESULTS

Among the 31 patients (mean age 56.2 ± 8.6 years, 27% female), 152 segments were analyzed. Of these segments, 42% were in the left anterior descending artery, 32% were in the left circumflex artery, and 26% were in the right coronary artery. Plaque morphology by IVUS identified 103 segments as fibrous (68%), 31 as fibrocalcific (20%), and 6 as calcific (4.0%); 12 segments were normal (8.0%). To evaluate for the presence of plaque, CCTA had an overall sensitivity and specificity of 99% and 75%, respectively. In patients who underwent CCTA with a tube voltage of 100 kV, both sensitivity and specificity were 100%. The sensitivity and specificity of CCTA to identify plaque as calcified (fibrocalcific or calcific) vs noncalcified (soft or fibrous) were 87% and 96%, respectively. Overall, the accuracy of CCTA to detect the presence of plaque was 97%; the accuracy to detect plaque calcification was 94%.

CONCLUSIONS

CCTA offers excellent sensitivity and accuracy for plaque detection and morphology characterization in nonocclusive coronary segments. In addition, diagnostic accuracy is preserved with a reduced tube voltage protocol.

Assessment of myocardial viability based on dual-energy computed tomography in patients with chronic myocardial infarction: comparison with magnetic resonance imaging

PURPOSE

To evaluate the diagnostic performance of dual-energy computed tomography (DECT) for the assessment of myocardial viability compared with magnetic resonance imaging (MRI) in patients with chronic myocardial infarction (CMI).

METHODS AND MATERIAL

Twenty-six patients were prospectively enrolled, who underwent DECT and MRI at delayed phase. The infarct volumes for DECT and MRI were measured.

RESULTS

In per-segment and per-vessel analysis, DECT showed excellent diagnostic performance compared with MRI (diagnostic accuracy: 86.2%, 81.2% respectively). In volume analysis, DECT correlated well with MRI (r=0.966, p<0.0001).

CONCLUSIONS

DECT has excellent diagnostic performance for detecting CMI.

ESTIMATION OF CARDIAC CT ANGIOGRAPHY RADIATION DOSE TOWARD THE ESTABLISHMENT OF NATIONAL DIAGNOSTIC REFERENCE LEVEL FOR CCTA IN IRAN

In recent years, with the introduction of 64-slice CT and dual-source CT technology, coronary CT angiography (CCTA) has emerged as a useful diagnostic imaging modality as a non-invasive assessment of coronary heart disease. CT produces a larger radiation dose than other imaging tests and cardiac CT involves higher radiation dose with the advances in the spatial and temporal resolution. The aims of this study are patient dose assessment and establishment of national diagnostic reference level for CCTA in Iran. A questionnaire was sent to CCTA centers. Data for patient and CT protocols were obtained. The volumetric CT dose index (CTDIvol), dose length product (DLP) and total DLP were considered in the 32 cm standard body phantom. Calculation of estimated effective dose (ED) was obtained by multiplying the DLP by a conversion factor [k = 0.014 mSv (mGy·cm)-1]. Mean value of CTDIvol and DLP for CCTA was 50 mGy and 825 mGy·cm. The third quartile (75th) of the distribution of mean CTDIvol (66.54 mGy) and DLP (1073 mGy·cm) values was expressed as the diagnostic reference level (DRL) for CCTA in Iran. The median of ED was 10.26 mSv and interquartile range of ED was 7.08-15.03 mSv. A large variety in CTDIvol and DLP among CT scanner and different sites due to variability in CT parameter is noted. It seems that training could help to reduce patient's dose.

Myocardial CT perfusion imaging for ischemia detection

Coronary computed tomography angiography (CCTA) plays an important role in many specific scenarios such as in symptomatic patients with intermediate pretest of coronary artery disease (CAD), as well as in the triage of patients with acute chest pain with TIMI risk ≤2. However, it cannot detect the presence of associated ischemia, which is critical for clinical decision making among patients with moderate to severe stenosis. Although functional information can be obtained with different non-invasive tools, cardiac CT is the unique modality that can perform a comprehensive evaluation of coronary anatomy plus the functional significance of lesions. Myocardial CT perfusion (CTP) can be performed with different approaches such as static and dynamic CTP. In addition, static CTP can be performed using single energy CT (SECT) or dual energy CT (DECT). In this review, we will discuss the technical parameters and the available clinical evidence of static CTP using both SECT and DECT.

Diagnostic accuracy of carotid intima media thickness in predicting coronary plaque burden on coronary computed tomography angiography in patients with obstructive sleep apnoea

AIM

To assess the diagnostic accuracy of common carotid artery intima media thickness (CIMT) for coronary artery disease (CAD) detection in patients with obstructive sleep apnoea (OSA).

MATERIALS & METHODS

Patients with clinically suspected OSA prospectively underwent polysomnography (PSG), ultrasound CIMT measurement and coronary computed tomography angiography (CTA). An average CIMT of ≥0.9 mm in either common carotid artery designated as a positive test. Coronary CTA was the reference standard for the presence of CAD. Coronary plaque presence, volume, density and type were correlated with CIMT findings.

RESULTS

35 consecutive male patients were enrolled from sleep clinic. Two patients had no evidence of OSA on PSG (apnoea-hypopnea index [AHI]<5/hr), and were excluded. Of the remaining 33, 18 (54%) had mild-moderate OSA (AHI 5-30/hr) and 15 (46%) had severe OSA (AHI >30/hr). Eight (24%) patients had CAD on coronary CTA. Coronary plaques were predominantly non- or partly calcified, and located in proximal coronary artery segments. Sensitivity, specificity, positive and negative predictive and likelihood ratios for a positive CIMT (≥0.9 mm) in diagnosing CAD were 0.5 (95% confidence interval: 0.76-0.12), 0.96 (1-0.89), 80, 85.7, 12.5 and 0.52 respectively. The adjusted odds ratio was 40.8.

CONCLUSION

In patients with OSA, CIMT is a highly specific but poorly sensitive test for detecting CAD.

Iterative Image Reconstruction Improves the Accuracy of Automated Plaque Burden Assessment in Coronary CT Angiography: A Comparison With Intravascular Ultrasound

OBJECTIVE

The purpose of this study was to determine whether use of iterative image reconstruction algorithms improves the accuracy of coronary CT angiography (CCTA) compared with intravascular ultrasound (IVUS) in semiautomated plaque burden assessment.

MATERIALS AND METHODS

CCTA and IVUS images of seven coronary arteries were acquired ex vivo. CT images were reconstructed with filtered back projection (FBP) and adaptive statistical (ASIR) and model-based (MBIR) iterative reconstruction algorithms. Cross-sectional images of the arteries were coregistered between CCTA and IVUS in 1-mm increments. In CCTA, fully automated (without manual corrections) and semiautomated (allowing manual corrections of vessel wall boundaries) plaque burden assessments were performed for each of the reconstruction algorithms with commercially available software. In IVUS, plaque burden was measured manually. Agreement between CCTA and IVUS was determined with Pearson correlation.

RESULTS

A total of 173 corresponding cross sections were included. The mean plaque burden measured with IVUS was 63.39% ± 10.63%. With CCTA and the fully automated technique, it was 54.90% ± 11.70% with FBP, 53.34% ± 13.11% with ASIR, and 55.35% ± 12.22% with MBIR. With CCTA and the semiautomated technique mean plaque burden was 54.90% ± 11.76%, 53.40% ± 12.85%, 57.09% ± 11.05%. Manual correction of the semiautomated assessments was performed in 39% of all cross sections and improved plaque burden correlation with the IVUS assessment independently of reconstruction algorithm (p < 0.0001). Furthermore, MBIR was superior to FBP and ASIR independently of assessment method (semiautomated, r = 0.59 for FBP, r = 0.52 for ASIR, r = 0.78 for MBIR, all p < 0.001; fully automated, r = 0.40 for FBP, r = 0.37 for ASIR, r = 0.53 for MBIR, all p < 0.001).

CONCLUSION

For the quantification of plaque burden with CCTA, MBIR led to better correlation with IVUS than did traditional reconstruction algorithms such as FBP, independently of the use of a fully automated or semiautomated assessment approach. The highest accuracy for quantifying plaque burden with CCTA can be achieved by using MBIR data with semiautomated assessment.

Improved diagnostic accuracy when combining computed tomography angiography and corrected coronary opacification in patients with coronary stents

Background The accuracy of coronary computed tomography angiography (CCTA) is sub-optimal in patients with coronary stents. Methods that can increase its diagnostic accuracy are desirable. Objective A proof-of-concept study was undertaken to determine if corrected coronary opacification (CCO) differences can improve the accuracy of CCTA in stented coronary arteries. Methods PCI patients who underwent both CCTA and invasive coronary angiography (ICA) within 3 months were analyzed. Coronary luminal attenuation values (normalized to the aorta) were measured proximally and distally to coronary stents. CCO differences were evaluated for ability to predict (i) stenosis on invasive angiography, (ii) abnormal resting coronary flow as measured by the corrected thrombolysis in myocardial infarction (TIMI) frame count (cTFC), and (iii) the combination of abnormal resting flow and significant stenosis on invasive angiography. Results Twenty-nine stented coronary arteries (n = 25, mean age =61.4 years, men =80.0%) were assessed. In stented coronary vessels, CCO identified stenosis (≥ 70%) with an area under the curve of 0.767 (P = 0.021). CCO predicted abnormal resting coronary flow with high accuracy (AUC =0.867, P = 0.002). Combined CCTA/CCO identified both abnormal cTFC and stenosis ≥70% on ICA (functionally significant stenosis) with diagnostic accuracy of 92.3%. In contrast, CCTA visual assessment alone had lower diagnostic accuracy of 66.7% for identifying functionally significant stenosis. Conclusion CCO differences are predictive of abnormal resting flow and consequently, in-stent restenosis. Incorporation of this technique may improve the specificity of CCTA in PCI patients.

A Study of Coronary Bifurcation Shape in a Normal Population

During percutaneous coronary intervention, stents are placed in narrowings of the arteries to restore normal blood flow. Despite improvements in stent design, deployment techniques and drug-eluting coatings, restenosis and stent thrombosis remain a significant problem. Population stent design based on statistical shape analysis may improve clinical outcomes. Computed tomographic (CT) coronary angiography scans from 211 patients with a zero calcium score, no stenoses and no intermediate artery, were used to create statistical shape models of 446 major coronary artery bifurcations (left main, first diagonal and obtuse marginal and right coronary crux). Coherent point drift was used for registration. Principal component analysis shape scores were tested against clinical risk factors, quantifying the importance of recognised shape features in intervention including size, angles and curvature. Significant differences were found in (1) vessel size and bifurcation angle between the left main and other bifurcations; (2) inlet and curvature angle between the right coronary crux and other bifurcations; and (3) size and bifurcation angle by sex. Hypertension, smoking history and diabetes did not appear to have an association with shape. Physiological diameter laws were compared, with the Huo-Kassab model having the best fit. Bifurcation coronary anatomy can be partitioned into clinically meaningful modes of variation showing significant shape differences. A computational atlas of normal coronary bifurcation shape, where disease is common, may aid in the design of new stents and deployment techniques, by providing data for bench-top testing and computational modelling of blood flow and vessel wall mechanics.

The influence of cardiac function on coronary arterial enhancement at coronary computed tomography angiography: A cross-sectional study

Background:

The purpose of this study was to evaluate the influence of ejection fraction (EF) on peak aortic time (PAT) and peak aortic enhancement (PAE) during coronary computed tomography angiography (CTA).

Materials and Methods:

One-hundred and twenty patients (64 men, 56 women) underwent measurement of coronary CTA with a measurement of EF within 3 months of coronary CTA. Pearson's correlation coefficient analysis was used to investigate the relationships between EF, PAT and PAE, and peak attenuation of all coronary arteries.

Results:

The range of EF was (25%–70%) (mean: 55 ± 7.7). The range of PAT and PAE of ascending aorta on bolus test was 13–31 s (mean: 19.3 ± 2) and 153–435 HU (mean: 235 ± 40.6), respectively. Mean peak attenuation of ascending aorta, right coronary artery, left coronary artery, left circumflex artery, and left anterior descending were (561 ± 119), (476 ± 109), (505 ± 108), (467 ± 113), and (473 ± 104), respectively. There was a negative correlation between EF and PAT (r = −0.266, P = 0.003); however, there was no significant correlation between EF and PAE (r = −0.027, P = 0.767). In addition, there was no significant correlation between EF and the peak attenuation of coronary arteries.

Conclusion:

PAT was related to EF, but there was no relationship between PAE and EF. One of the explanation is that the left ventricular EF used for our study was assessed with echocardiography which is used roughly estimation of EF with interval of 5%–10% and may cause confounding results.

A head-to-head comparison between CT- and IVUS-derived coronary blood flow models

The goal of this work is to compare coronary hemodynamics as predicted by computational blood flow models derived from two imaging modalities: coronary computed tomography angiography (CCTA) and intravascular ultrasound integrated with angiography (IVUS). Criteria to define boundary conditions are proposed to overcome the dissimilar anatomical definition delivered by both modalities. The strategy to define boundary conditions is novel in the present context, and naturally accounts for the flow redistribution induced by the resistance of coronary vessels. Hyperemic conditions are assumed to assess model predictions under stressed hemodynamic environments similar to those encountered in Fractional Flow Reserve (FFR) calculations. As results, it was found that CCTA models predict larger pressure drops, higher average blood velocity and smaller FFR. Concerning the flow rate at distal locations in the major vessels of interest, it was found that CCTA predicted smaller flow than IVUS, which is a consequence of a larger sensitivity of CCTA models to coronary steal phenomena. Comparisons to in-vivo measurements of FFR are shown.

Relationship Among Risk Score Systems and Coronary Atherosclerosis Determined by Multislice Computed Tomography

BACKGROUND

Risk score systems (RSS) were designed to estimate the risk of cardiac events. Their ability to predict coronary atherosclerosis (CA) has not been established.

HYPOTHESIS

Risk score systems can predict presence of CA in patients without typical symptoms or ischemia. Because design of each RSS is different, their predictive value could also differ.

METHODS

A retrospective analysis was done on patients from a low-risk region referred for cardiac multislice computed tomography (MSCT). The sample included low- to intermediate-risk patients with nontypical chest pain and asymptomatic high-risk patients. Patients with documented ischemia were excluded. Three RSS were determined: Framingham Risk Score (FRS), Regicor (FRS calibrated for Spanish population), and Systematic Coronary Risk Evaluation (SCORE). Coronary arteries were investigated to determine calcium score and presence of protruding atheromas.

RESULTS

We analyzed 582 patients (53.8% male; mean age 51 ± 11.5 years). Their mean estimated risk was intermediate: 15.6 ± 10.4 by FRS, 6.3 ± 4.3 by Regicor, and 3.9 ± 4.1 by SCORE. The MSCT showed no CA in 38.8%, nonobstructive plaques in 28.7%, and obstructive ones in 32.5%. The ability of the RSS to predict CA was not significantly different, with moderate diagnostic value (areas under ROC curves, 0.72-0.65). The prevalence of CA was high in low-risk patients: 40%, 47%, and 53% in FRS, Regicor, and SCORE low-risk patients, respectively.

CONCLUSIONS

Risk score systems have only moderate diagnostic value to predict presence of CA, without significant differences among them. Coronary artery disease is highly prevalent in patients considered low risk.