Performance of a Novel CT-Derived Fractional Flow Reserve Measurement to Detect Hemodynamically Significant Coronary Stenosis

Background@#Fractional flow reserve (FFR) based on computed tomography (CT) has been shown to better identify ischemia-causing coronary stenosis. However, this current technology requires high computational power, which inhibits its widespread implementation in clinical practice. This prospective, multicenter study aimed at validating the diagnostic performance of a novel simple CT based fractional flow reserve (CT-FFR) calculation method in patients with coronary artery disease. @*Methods@#Patients who underwent coronary CT angiography (CCTA) within 90 days and invasive coronary angiography (ICA) were prospectively enrolled. A hemodynamically significant lesion was defined as an FFR ≤ 0.80, and the area under the receiver operating characteristic curve (AUC) was the primary measure. After the planned analysis for the initial algorithm A, we performed another set of exploratory analyses for an improved algorithm B. @*Results@#Of 184 patients who agreed to participate in the study, 151 were finally analyzed.Hemodynamically significant lesions were observed in 79 patients (52.3%). The AUC was 0.71 (95% confidence interval [CI], 0.63–0.80) for CCTA, 0.65 (95% CI, 0.56–0.74) for CT-FFR algorithm A (P = 0.866), and 0.78 (95% CI, 0.70–0.86) for algorithm B (P = 0.112). Diagnostic accuracy was 0.63 (0.55–0.71) for CCTA alone, 0.66 (0.58–0.74) for algorithm A, and 0.76 (0.68–0.82) for algorithm B. @*Conclusion@#This study suggests the feasibility of automated CT-FFR, which can be performed on-site within several hours. However, the diagnostic performance of the current algorithm does not meet the a priori criteria for superiority. Future research is required to improve the accuracy.

Prognostic Value of Coronary CT Angiography forPredicting Poor Cardiac Outcome in Stroke Patientswithout Known Cardiac Disease or Chest Pain:The Assessment of Coronary Artery Disease in StrokePatients Study

Objective@#To assess the incremental prognostic value of coronary computed tomography angiography (CCTA) in comparison toa clinical risk model (Framingham risk score, FRS) and coronary artery calcium score (CACS) for future cardiac events in ischemicstroke patients without chest pain. @*Materials and Methods@#This retrospective study included 1418 patients with acute stroke who had no previous cardiac diseaseand underwent CCTA, including CACS. Stenosis degree and plaque types (high-risk, non-calcified, mixed, or calcified plaques) wereassessed as CCTA variables. High-risk plaque was defined when at least two of the following characteristics were observed:low-density plaque, positive remodeling, spotty calcification, or napkin-ring sign. We compared the incremental prognosticvalue of CCTA for major adverse cardiovascular events (MACE) over CACS and FRS. @*Results@#The prevalence of any plaque and obstructive coronary artery disease (CAD) (stenosis ≥ 50%) were 70.7% and 30.2%,respectively. During the median follow-up period of 48 months, 108 patients (7.6%) experienced MACE. Increasing FRS, CACS,and stenosis degree were positively associated with MACE (all p 0.05). @*Conclusion@#Assessment of stenosis degree and plaque type using CCTA provided additional prognostic value over CACS andFRS to risk stratify stroke patients without prior history of CAD better.

Troponin-Positive Non-Obstructive Coronary Arteries and Myocardial Infarction with Non-Obstructive Coronary Arteries: Definition, Etiologies, and Role of CT and MR Imaging

In approximately 10% of patients with acute myocardial infarction (MI), angiography does not reveal an obstructive coronary stenosis. This is known as myocardial infarction with non-obstructive coronary arteries (MINOCA), which has complex and multifactorial causes. However, this term can be confusing and open to dual interpretation, because MINOCA is also used to describe patients with acute myocardial injury caused by ischemia-related myocardial necrosis. Therefore, with regards to this specific context of MINOCA, the generic term for MINOCA should be replaced with troponin-positive with non-obstructive coronary arteries (TpNOCA). The causes of TpNOCA can be subcategorized into epicardial coronary (causes of MINOCA), myocardial, and extracardiac disorders. Cardiac magnetic resonance imaging can confirm MI and differentiate various myocardial causes, while cardiac computed tomography is useful to diagnose the extracardiac causes.

Troponin-Positive Non-Obstructive Coronary Arteries and Myocardial Infarction with Non-Obstructive Coronary Arteries: Definition, Etiologies, and Role of CT and MR Imaging

In approximately 10% of patients with acute myocardial infarction (MI), angiography does not reveal an obstructive coronary stenosis. This is known as myocardial infarction with non-obstructive coronary arteries (MINOCA), which has complex and multifactorial causes. However, this term can be confusing and open to dual interpretation, because MINOCA is also used to describe patients with acute myocardial injury caused by ischemia-related myocardial necrosis. Therefore, with regards to this specific context of MINOCA, the generic term for MINOCA should be replaced with troponin-positive with non-obstructive coronary arteries (TpNOCA). The causes of TpNOCA can be subcategorized into epicardial coronary (causes of MINOCA), myocardial, and extracardiac disorders. Cardiac magnetic resonance imaging can confirm MI and differentiate various myocardial causes, while cardiac computed tomography is useful to diagnose the extracardiac causes.

Evaluation of Coronary Artery Calcium Progression in Asymptomatic Individuals with an Initial Score of Zero

BACKGROUND AND OBJECTIVES: Coronary artery calcium (CAC) scoring in the asymptomatic population can improve cardiovascular risk prediction. We aimed to assess CAC progression and the impact of coronary risk factors on the CAC progression rate in asymptomatic Korean individuals with a baseline CAC score of zero. METHODS: The study population was derived from the Korea Initiatives on Coronary Artery Calcification (KOICA) registry: a retrospective, single ethnicity, multicenter registry of asymptomatic individuals who underwent CAC scoring as a part of a health checkup. Individuals with at least two CAC scores and an initial score of zero were included. CAC progression was defined as [√CAC score (follow-up) − √CAC score (baseline)] ≥2.5. The 10-year atherosclerotic cardiovascular disease (ASCVD) risk was calculated. RESULTS: Among 6,268 participants (mean age, 48.0±7.1 years; male, 80.5%), 719 (11.5%) experienced CAC progression during follow-up (median, 109 months; interquartile range, 78–208 months). The CAC progression rate was 0.3%, 1.9%, 4.3%, 8.6%, and 16.7% in years 1–5, respectively. The chance of CAC progression at 5 years was 13.1%, 22.0%, and 27.9% for individuals with a 10-year ASCVD risk of <5%, ≥5% but <7.5%, and ≥7.5%, respectively. A multivariable analysis revealed age, male sex, waist circumference, diabetes, and low-density lipoprotein cholesterol level as independently associated with annualized CAC progression (p<0.001, p=0.017, p=0.025, p=0.032, and p=0.003, respectively). CONCLUSIONS: The probability of CAC progression is very low in Korean individuals with a CAC score of zero. However, the risk of CAC progression increases nonlinearly over time, and increases as the 10-year ASCVD risk increases.

Recent Update of Advanced Imaging for Diagnosis of Cardiac Sarcoidosis: Based on the Findings of Cardiac Magnetic Resonance Imaging and Positron Emission Tomography

Sarcoidosis is a multisystem disease characterized by noncaseating granulomas. Cardiac involvement is known to have poor prognosis because it can manifest as a serious condition such as the conduction abnormality, heart failure, ventricular arrhythmia, or sudden cardiac death. Although early diagnosis and early treatment is critical to improve patient prognosis, the diagnosis of CS is challenging in most cases. Diagnosis usually relies on endomyocardial biopsy (EMB), but its diagnostic yield is low due to the incidence of patchy myocardial involvement. Guidelines for the diagnosis of CS recommend a combination of clinical, electrocardiographic, and imaging findings from various modalities, if EMB cannot confirm the diagnosis. Especially, the role of advanced imaging such as cardiac magnetic resonance (CMR) imaging and positron emission tomography (PET), has shown to be important not only for the diagnosis, but also for monitoring treatment response and prognostication. CMR can evaluate cardiac function and fibrotic scar with good specificity. Late gadolinium enhancement (LGE) in CMR shows a distinctive enhancement pattern for each disease, which may be useful for differential diagnosis of CS from other similar diseases. Effectively, T1 or T2 mapping techniques can be also used for early recognition of CS. In the meantime, PET can detect and quantify metabolic activity and can be used to monitor treatment response. Recently, the use of a hybrid CMR-PET has introduced to allow identify patients with active CS with excellent co-localization and better diagnostic accuracy than CMR or PET alone. However, CS may show various findings with a wide spectrum, therefore, radiologists should consider the possible differential diagnosis of CS including myocarditis, dilated cardiomyopathy (DCM), hypertrophic cardiomyopathy, amyloidosis, and arrhythmogenic right ventricular cardiomyopathy. Radiologists should recognize the differences in various diseases that show the characteristics of mimicking CS, and try to get an accurate diagnosis of CS.

Assessment of Left Ventricular Myocardial Diseases with Cardiac Computed Tomography

Rapid advances in cardiac computed tomography (CT) have enabled the characterization of left ventricular (LV) myocardial diseases based on LV anatomical morphology, function, density, and enhancement pattern. Global LV function and regional wall motion can be evaluated using multi-phasic cine CT images. CT myocardial perfusion imaging facilitates the identification of hemodynamically significant coronary artery disease. CT delayed-enhancement imaging is used to detect myocardial scar in myocardial infarction and to measure the extracellular volume fraction in non-ischemic cardiomyopathy. Multi-energy cardiac CT allows the mapping of iodine distribution in the myocardium. This review summarizes the current techniques of cardiac CT for LV myocardial assessment, highlights the key findings in various myocardial diseases, and presents future applications to complement echocardiography and cardiovascular magnetic resonance.

Evaluation of Coronary Artery Calcium Progression in Asymptomatic Individuals with an Initial Score of Zero

BACKGROUND AND OBJECTIVES@#Coronary artery calcium (CAC) scoring in the asymptomatic population can improve cardiovascular risk prediction. We aimed to assess CAC progression and the impact of coronary risk factors on the CAC progression rate in asymptomatic Korean individuals with a baseline CAC score of zero.@*METHODS@#The study population was derived from the Korea Initiatives on Coronary Artery Calcification (KOICA) registry: a retrospective, single ethnicity, multicenter registry of asymptomatic individuals who underwent CAC scoring as a part of a health checkup. Individuals with at least two CAC scores and an initial score of zero were included. CAC progression was defined as [√CAC score (follow-up) −√CAC score (baseline)] ≥2.5. The 10-year atherosclerotic cardiovascular disease (ASCVD) risk was calculated.@*RESULTS@#Among 6,268 participants (mean age, 48.0±7.1 years; male, 80.5%), 719 (11.5%) experienced CAC progression during follow-up (median, 109 months; interquartile range, 78–208 months). The CAC progression rate was 0.3%, 1.9%, 4.3%, 8.6%, and 16.7% in years 1–5, respectively. The chance of CAC progression at 5 years was 13.1%, 22.0%, and 27.9% for individuals with a 10-year ASCVD risk of <5%, ≥5% but <7.5%, and ≥7.5%, respectively. A multivariable analysis revealed age, male sex, waist circumference, diabetes, and low-density lipoprotein cholesterol level as independently associated with annualized CAC progression (p<0.001, p=0.017, p=0.025, p=0.032, and p=0.003, respectively).@*CONCLUSIONS@#The probability of CAC progression is very low in Korean individuals with a CAC score of zero. However, the risk of CAC progression increases nonlinearly over time, and increases as the 10-year ASCVD risk increases.

Multimodality Imaging in Patients with Secondary Hypertension: With a Focus on Appropriate Imaging Approaches Depending on the Etiologies

Although the causes of hypertension are usually unknown, about 10% of the cases occur secondary to specific etiologies, which are often treatable. Common categories of secondary hypertension include renal parenchymal disease, renovascular stenosis, vascular and endocrinologic disorders. For diseases involving the renal parenchyma and adrenal glands, ultrasonography (US), computed tomography (CT) or magnetic resonance (MR) imaging is recommended. For renovascular stenosis and vascular disorders, Doppler US, conventional or noninvasive (CT or MR) angiography is an appropriate modality. Nuclear imaging can be useful in the differential diagnosis of endocrine causes. Radiologists should understand the role of each imaging modality and its typical findings in various causes of secondary hypertension. This article focuses on appropriate imaging approaches in accordance with the categorized etiologies leading to hypertension.

Ultrasonographic evaluation of complications related to transfemoral arterial procedures

The transfemoral arterial approach is used to gain access for angiography, percutaneous coronary interventions, or various endovascular therapies. To decrease the risk of procedure-related vascular complications, it is recommended to puncture the common femoral artery in its middle segment. However, due to inadequate access or anatomical variability, various complications, including hematoma, pseudoaneurysm, arteriovenous fistula, thrombosis, or dissection, can occur after transfemoral arterial interventions. Duplex ultrasound has proven to be an excellent noninvasive modality that provides not only anatomic but also hemodynamic information, effectively detecting and differentiating various femoral puncture-related complications. Radiologists should be familiar with the characteristic sonographic findings of the entire spectrum of transfemoral puncture-related vascular complications for early detection and proper treatment.

SEALONE (Safety and Efficacy of Coronary Computed Tomography Angiography with Low Dose in Patients Visiting Emergency Room) trial: study protocol for a randomized controlled trial

OBJECTIVE: Chest pain is one of the most common complaints in the emergency department (ED). Cardiac computed tomography angiography (CCTA) is a frequently used tool for the early triage of patients with low- to intermediate-risk acute chest pain. We present a study protocol for a multicenter prospective randomized controlled clinical trial testing the hypothesis that a low-dose CCTA protocol using prospective electrocardiogram (ECG)-triggering and limited-scan range can provide sufficient diagnostic safety for early triage of patients with acute chest pain. METHODS: The trial will include 681 younger adult (aged 20 to 55) patients visiting EDs of three academic hospitals for acute chest pain or equivalent symptoms who require further evaluation to rule out acute coronary syndrome. Participants will be randomly allocated to either low-dose or conventional CCTA protocol at a 2:1 ratio. The low-dose group will undergo CCTA with prospective ECG-triggering and restricted scan range from sub-carina to heart base. The conventional protocol group will undergo CCTA with retrospective ECG-gating covering the entire chest. Patient disposition is determined based on computed tomography findings and clinical progression and all patients are followed for a month. The primary objective is to prove that the chance of experiencing any hard event within 30 days after a negative low-dose CCTA is less than 1%. The secondary objectives are comparisons of the amount of radiation exposure, ED length of stay and overall cost. RESULTS AND CONCLUSION: Our low-dose protocol is readily applicable to current multi-detector computed tomography devices. If this study proves its safety and efficacy, dose-reduction without purchasing of expensive newer devices would be possible.

Additive Role of Coronary Magnetic Resonance Angiography for the Evaluation of Coronary Artery Disease

Coronary magnetic resonance angiography (CMRA) allows a noninvasive assessment of the coronary anatomy without exposing the patients to radiation. It is also superior to coronary computed tomography angiography (CCTA) for the evaluation of luminal narrowing in heavily calcified coronary segments. We report a case with triple-vessel disease, but it could not be accurately assessed by CCTA because of calcification and lack of a significant perfusion defect or myocardial scarring on cardiac magnetic resonance imaging (MRI). However, whole-heart CMRA performed as part of the cardiac MRI protocol demonstrated significant triple-vessel disease with left main involvement, confirmed by subsequent invasive angiography with a fractional flow reserve measurement.

CT Features of Vasculitides Based on the 2012 International Chapel Hill Consensus Conference Revised Classification

Vasculitis, characterized by inflammation of vessel walls, is comprised of heterogeneous clinicopathological entities, and thus poses a diagnostic challenge. The most widely used approach for classifying vasculitides is based on the International Chapel Hill Consensus Conference (CHCC) nomenclature system. Based on the recently revised CHCC 2012, we propose computed tomography (CT) features of vasculitides and a differential diagnosis based on location and morphological characteristics. Finally, vasculitis mimics should be differentiated, because erroneous application of immunosuppressive drugs on vasculitis mimics may be ineffective, even deteriorating. This article presents the utility of CT in the diagnosis and differential diagnosis of vasculitides.

Prediction of Intimal Tear Site by Computed Tomography in Acute Aortic Dissection Type A

BACKGROUND AND OBJECTIVES: Preoperative identification of intimal tear site in acute type A dissection will help procedural planning. The objective of this study was to determine the key findings of computed tomography (CT)-based prediction for tear site and compare the accuracy between radiologists and surgeons. SUBJECTS AND METHODS: Multi-detector CT (MDCT) images from 50 patients who underwent surgical repair of type A aortic dissection were retrospectively reviewed by 4 cardiac surgeons with limited experience or by 3 radiologists specialized in cardiovascular imaging. Surgical findings of intimal tear site were used as references. RESULTS: In surgical findings, the locations of intimal tear that were identified in 43 patients included aorta (n=25), ascending with arch (n=7), and arch only (n=11). The rest were retrograde dissections from the tear of descending aorta. Key CT findings that were most frequently found were defect in the intimal flap shadow (30.0+/-4.0 patients/reviewer, accuracy 87.0+/-11.7%) and differential filling of false lumen by phase and location (9.4+/-2.9 patients/reviewer, 84.8+/-10.4%). Surgeons predicted tear site (75.0+/-7.7% vs. 86.7+/-1.2%, p=0.055) and specified flap defect (80.5+/-10.3% vs. 95.7+/-7.4%, p=0.073) with lower accuracy than radiologists. CONCLUSIONS: With MDCT imaging, well-educated surgeons could be accurate in three fourths of cases. There was room for improvement through experience. Considering the substantial possibility of inaccuracy, critical decisions on CT images should be made through thorough reviewing by as many experienced radiologists and surgeons as possible.

Prospective Study on the Incidence of Postoperative Venous Thromboembolism in Korean Patients with Colorectal Cancer / Journal of the Korean Cancer Association, 대한암학회지

PURPOSE: Pharmacologic thromboprophylaxis is routinely recommended for Western cancer patients undergoing major surgery for prevention of venous thromboembolism (VTE). However, it is uncertainwhetherroutine administration of pharmacologic thromboprophylaxis is necessary in all Asian surgical cancer patients. This prospective study was conducted to examine the incidence of and risk factors for postoperative VTE in Korean colorectal cancer (CRC) patients undergoing major abdominal surgery. MATERIALS AND METHODS: This study comprised two cohorts, and none of patients received perioperative pharmacologic thromboprophylaxis. In cohort A (n=400), patients were routinely screened for VTE using lower-extremity Doppler ultrasonography (DUS) on postoperative days 5-14. In cohort B (n=148), routine DUS was not performed, and imaging was only performed when there were symptoms or signs that were suspicious for VTE. The primary endpoint was the VTE incidence at 4 weeks postoperatively in cohort A. RESULTS: The postoperative incidence of VTE was 3.0% (n=12) in cohort A. Among the 12 patients, eight had distal calf vein thromboses and one had symptomatic thrombosis. Age ≥ 70 years (odds ratio [OR], 5.61), ≥ 2 comorbidities (OR, 13.42), and white blood cell counts of > 10,000/μL (OR, 17.43) were independent risk factors for postoperative VTE (p < 0.05). In cohort B, there was one case of VTE (0.7%). CONCLUSION: The postoperative incidence of VTE, which included asymptomatic cases, was 3.0% in Korean CRC patients who did not receive pharmacologic thromboprophylaxis. Perioperative pharmacologic thromboprophylaxis should be administered to Asian CRC patients on a risk-stratified basis.

First-pass Stress Perfusion MR Imaging Findings of Apical Hypertrophic Cardiomyopathy: with Relation to LV Wall Thickness and Late Gadolinium-enhancement

PURPOSE: To evaluate the prevalence and pattern of perfusion defect (PD) on first-pass stress perfusion MR imaging in relation with the degree of left ventricular hypertrophy (LVH) and late gadolinium-enhancement (LGE) in patients with apical hypertrophic cardiomyopathy (APH). MATERIALS AND METHODS: Cardiac MR imaging with first-pass stress perfusion, cine, and LGE sequence was performed in 26 patients with APH from January 2008 to December 2012. We analyzed a total of 416 segments for LV wall thickness on end-diastolic phase of cine images, and evaluated the number of hypertrophied segment and number of consecutive hypertrophied segment (NCH). We assessed the presence or absence of PD and LGE from all patients. If there was PD, we subdivided the pattern into sporadic (sporadic-PD) or ring (ring-PD). Using univariate logistic method, we obtained the independent predictor for presence of overall PD and ring-PD. RESULTS: PD on stress perfusion MRI was observed in 20 patients (76.9%), 12 of them (60%) showed ring-PD. Maximal LV wall thickness and number of hypertrophied segment were independent predictors for overall PD (all, p < 0.05). NCH with more than 3 segments was an additional independent factor for ring-PD. However, LGE was not statistically related with PD in patients with APH. CONCLUSION: About three quarters of the patients with APH showed PD, most of them represented as ring-PD. LVH degree or distribution was related with pattern of PD, however, LGE was not related with PD. Therefore, the clinical significance of PD in the patients with APH seems to be different from those with non-APH, and further comparison study between the two groups should be carried out.

Coronary Vasospastic Angina: Assessment by Multidetector CT Coronary Angiography

OBJECTIVE: We aimed to describe the imaging findings of multidetector CT coronary angiography (MDCTA) in cases of vasospastic angina (VA) and to determine the accuracy of MDCTA in the identification of VA as compared with invasive coronary angiography with an ergonovine provocation test (CAG with an EG test). MATERIALS AND METHODS: Fifty-three patients with clinically suspected VA were enrolled in this study. Two radiologists analyzed the stenosis degree, presence or absence of plaque, plaque composition, and a remodeling index of the related-segment in CAG with an EG test, which were used as a gold standard. We evaluated the diagnostic performances of MDCTA by comparing the MDCTA findings with those of CAG with an EG test. RESULTS: Among the 25 patients with positive CAG with an EG test, all 12 patients with significant stenosis showed no definite plaque with the negative arterial remodeling. Of the six patients with insignificant stenosis, three (50%) had non-calcified plaque (NCP), two (33%) had mixed plaque, and one (17%) had calcified plaque. When the criteria for significant stenosis with negative remodeling but no definite evidence of plaque as a characteristic finding of MDCTA were used, results showed sensitivities, specificities, positive predictive values (PPV), and negative predictive values (NPV) of 48%, 100%, 100%, and 68%, respectively. CONCLUSION: Significant stenosis with negative remodeling, but no definite evidence of plaque, is the characteristic finding on MDCTA of VA. Cardiac MDCTA shows good diagnostic performance with high specificity and PPV as compared with CAG with an EG test.

A Novel Biomarker of Coronary Atherosclerosis: Serum DKK1 Concentration Correlates with Coronary Artery Calcification and Atherosclerotic Plaques

DKK1 modulates Wnt signaling, which is involved in the atherosclerosis. However, no data exist regarding the usefulness of measuring serum DKK1 concentration in predicting coronary atherosclerosis. A total of 270 consecutive patients (62.8 +/- 11.2 yr; 70% male) were included. A contrast-enhanced 64-slice coronary MDCT was performed to identify the presence of atherosclerotic plaques. Agatston calcium scores (CS) were calculated to quantify the coronary artery calcification (CAC). DKK1 concentrations were measured by enzyme-linked immunosorbent assay. For each subsequent DKK1 quartile, there was a significant increase in CAC (P = 0.004) and the number of segments with coronary atherosclerosis (P or = 68.6 pg/mL demonstrated coronary atherosclerotic plaques even when they had low CS. Serum DKK1 concentrations correlate with the coronary atherosclerosis and play an independent role in predicting the presence of coronary atherosclerosis.

MR Imaging Findings of a Primary Cardiac Osteosarcoma and Its Bone Metastasis with Histopathologic Correlation

An osteosarcoma of cardiac origin is extremely rare, and a comprehensive description of MR imaging (MRI) findings of cardiac osteosarcoma and its metastasis in the femur have not been reported in the literature. We present a case of cardiac osteosarcoma in a 47-year-old woman and its metastasis to the femur, focusing on the description of MRI findings of the cardiac and metastatic bony osteosarcoma with a histopathologic correlation.

Subclinical Coronary Artery Disease as Detected by Coronary Computed Tomography Angiography in an Asymptomatic Population

BACKGROUND AND OBJECTIVES: Primary prevention of coronary artery disease (CAD) has become a public health issue, according to increasing awareness of the substantial risks posed by asymptomatic atherosclerosis. The aims of this study were to determine the prevalence and characteristics of subclinical CAD using coronary computed tomography angiography (CCTA), and to evaluate the role of this advanced technology in identifying subclinical CAD in asymptomatic Korean individuals, compared with conventional risk stratification. SUBJECTS AND METHODS: We enrolled 4,320 consecutive asymptomatic individuals (61% males, aged 50+/-9 years), who underwent 64-slice CCTA during a routine health check. RESULTS: Coronary artery plaques were present in 1,053 (24%) individuals. Significant stenosis (diameter stenosis > or =50%) was identified in 139 (3%) subjects, and most of the significant lesions (87%) were located in the left anterior descending artery. CCTA revealed noncalcified plaques in 5% of subjects with a coronary calcium score of zero (n=801). Although 25% (n=10) of those with noncalcified plaque had significant stenosis, most of them (90%) were classified into low- or moderate-risk groups according to National Cholesterol Education Program risk stratification guidelines. In a young population (age < or =55 years for males, < or =65 years for females), 30% of subjects with significant stenosis were classified into a low-risk group and 60% had low (0 to 100) calcium scores. CONCLUSION: Subclinical CAD in asymptomatic individuals cannot be ignored for its considerable prevalence, CCTA may be helpful in identifying at-risk subclinical CAD in a noninvasive manner, especially in the young and traditionally low-risk population.