Coronary calcium and cardiovascular event risk: evaluation by age- and sex-specific quartiles

Coronary artery calcium (CAC) score for cardiovascular risk stratification in a Thai clinical cohort: A comparison of absolute scores and age-sex-specific percentiles

Purposes

Coronary artery calcium (CAC) score provides a quantification of atherosclerotic plaque within the coronary arteries. This study aimed to examine the prevalence and CAC score distribution and to evaluate the association of each CAC score classifications with major adverse cardiovascular events (MACE) in a Thai clinical cohort.

Methods

This study was a retrospective observational cohort. We included patients aged above 35 years who underwent CAC score testing. The absolute and age-sex specific percentile classifications were categorized as 0, 1 to 10, 11 to 100, 101 to 400, and >400 and 0, <75th, 75th - 90th, and >90th, respectively. The endpoint was MACE, including cardiovascular death, myocardial infarction, heart failure hospitalization, coronary artery revascularization procedure, and stroke. Multivariable Cox regression was used to estimate the hazard ratios. The discriminative performance between classifications were compared using Harrell's C-statistics. The agreement was assessed via Cohen's Kappa.

Results

This study included 440 patients, with approximately 70% of Thai patients exhibiting a CAC score. CAC score distributed higher in male than female and increased with age. Both CAC score classification demonstrated the acceptable predictive performance. However, fair agreement was observed between classifications (Cohen's kappa 0.51, 95%CI 0.42-0.59). Within the absolute classification, a higher CAC score was associated with increased hazard ratios for MACE across stratified age-sex-specific percentile levels. In contrast, the hazard ratios for MACE did not consistently rise with higher age-sex-specific percentile CAC score when stratified by absolute CAC score levels.

Conclusions

Both absolute and age-sex-specific percentile CAC score demonstrated acceptable performance in predicting MACE. However, the absolute CAC score classification may be more suitable for risk stratification within the Thai clinical cohort. Our findings offer supportive information that could inform future recommendations for CAC score testing criteria within national clinical practice guidelines.

Machine Learning Approach for Cardiovascular Risk and Coronary Artery Calcification Score

Coronary artery calcification (CAC) could assist in the discovery of new risk elements for coronary artery disorder. CAC evaluation, on the other hand, is difficult due to the wide range of CAC in the populations. As a reason, evaluating and analysing data among research have become complicated. In the Research of Inherited Risk Factors for Coronary Atherosclerosis, we used CAC information to test the effects of different analytical methodologies on the correlation with recognized cardiovascular risk elements in asymptomatic patients. Cardiac computed tomography (CT) is also seeing an increase in examinations, and machine learning (ML) could assist with the growing amount of extracted data. Furthermore, there are other sectors in cardiac CT where machine learning could be crucial, including coronary calcium scoring, perfusion, and CT angiography. The establishment of risk evaluation algorithms based on information from CAC utilizing machine learning could assist in the categorization of patients undergoing cardiovascular into distinct risk groups and effectively adapt their treatments to their unique situations. Our findings imply that for forecasting CVD occurrences in asymptomatic people, age-sex segmentation by CAC percentile rank is as effective as absolute CAC scoring. Longitudinal population-based investigations are currently underway and would offer further definitive findings. While machine learning is a strong technology with a lot of possibilities, its implementations in the domain of cardiac CAC are generally in the early stages of development and are not currently commonly accessible in medical practise because of the requirement for substantial verification. Enhanced machine learning will, however, have a significant effect on cardiovascular and coronary artery calcification in the upcoming years.

Aortic enlargement and coronary artery calcification in a general population cohort

AIMS

The role of atherosclerosis in the pathogenesis of aortic enlargement is uncertain. We aimed to evaluate the relationship between the diameters of the ascending, descending and abdominal aorta, and coronary artery calcification.

METHODS AND RESULTS

Individuals in the Copenhagen General Population Study underwent thoracic and abdominal computed tomography. Maximal aortic diameters were measured in each aortic segment and coronary artery calcium scores (CACS) were calculated. Participants were stratified into five predefined groups according to CACSs and compared to aortic dimensions. The relation between aortic diameter and CACS was adjusted for risk factors for aortic dilatation in a multivariable model. A total of 2678 eligible individuals were included. In all segments of the aorta, aortic diameter was associated to CACSs, with mean increases in aortic diameters ranging from 0.7 to 3.5 mm in individuals with calcified coronary arteries compared to non-calcified subjects (P-value < 0.001). After correction for risk factors, individuals with CACS above 400 had larger ascending, descending and abdominal aortic diameter than the non-calcified reference group (P-value < 0.01).

CONCLUSION

Enlarged thoracic and abdominal aortic vascular segments are associated with co-existing coronary artery calcification in the general population.

Largely Accelerated Arterial Aging in Rheumatoid Arthritis Is Associated With Inflammatory Activity and Smoking in the Early Stage of the Disease

Background: Rheumatoid arthritis (RA) patients have a shorter life expectancy than the general population primarily due to cardiovascular comorbidities.

Objectives: To characterize arterial aging in RA.

Patients and Methods: Coronary calcium score (CCS) were available from 112 RA patients; out of these patients, follow-up CCS were measured for 54 randomly selected individuals. Control CCS were obtained from the MESA database (includes 6,000 < participants); arterial age was calculated from CCS.

Results: RA patients were significantly older (10.45 ± 18.45 years, p < 0.001) in terms of the arterial age than the age-, gender-, and race-matched controls. The proportion of RA patients who had zero CCS was significantly less (p < 0.01) than that of those in the MESA reference group. Each disease year contributed an extra 0.395 years (p < 0.01) on the top of the normal aging process. However, the rate of the accelerated aging is not uniform, in the first years of the disease it is apparently faster. Smoking (p < 0.05), previous cardiovascular events (p < 0.05), and high blood pressure (p < 0.05) had additional significant effect on the aging process. In the follow-up study, inflammatory disease activity (CRP > 5 mg/L, p < 0.05) especially in smokers and shorter than 10 years of disease duration (p = 0.05) had the largest impact.

Conclusion: Arterial aging is faster in RA patients than in control subjects, particularly in the first 10 years of the disease. Inflammation, previous cardiovascular events, and smoking are additional contributing factors to the intensified coronary atherosclerosis progression. These data support that optimal control of inflammation is essential to attenuate the cardiovascular risk in RA.

Low Iliofemoral Calcium Score May Predict Higher Survival after EVAR and FEVAR

BACKGROUND

Abdominal aortic aneurysm is associated with an increased mortality, mostly cardiovascular events. Moreover, aortoiliac calcification is associated with increased mortality in patients with peripheral occlusive disease. The aim of this study is to assess the potential association between iliofemoral calcification, assessed by calcium score, in patients undergoing infrarenal (endovascular aneurysm repair [EVAR]) or fenestrated endovascular aortic repair (FEVAR) and long-term mortality, particularly caused by cardiac events.

METHODS

All patients with preoperative noncontrast-enhanced computed tomographic scans who underwent infrarenal EVAR and FEVAR of nonruptured abdominal aortic aneurysm between 2004 and 2012 at a single tertiary center were screened for inclusion. Agatston calcium score was measured from the aortic bifurcation to common femoral arteries using a dedicated postprocessing software. The values are presented as median and interquartile range.

RESULTS

About 404 (62.05%) of 651 patients who underwent EVAR and FEVAR had sufficient imaging quality to be included. There was no difference in survival between included and excluded patients (P = 0.33). Nine patients (2.2%) died within 30 days of the operation, whereas the remaining were followed up for 6.3 (4.7-8.4) years. The iliofemoral calcium score was 8348 (3830-14,179). Estimated overall survival at 5 years was 73 ± 2%. Patients within the lowest quartile of iliofemoral calcium score had significantly higher overall survival (5 years: 79 ± 4% vs. 71 ± 3%; P = 0.01) and cardiac event-free survival (5 years: 95 ± 2% vs. 91 ± 2%; P = 0.033) when compared with the remaining ones. Calcium score was associated with neither univariate regression analysis with survival (odds ratio, 1.016 [0.988-1.045]; P = 0.268) nor cardiac event-free survival (odds ratio, 1.024 [0.986-1.063]; P = 0.222).

CONCLUSIONS

Low iliofemoral calcium score may be associated with lower incidence of fatal cardiac events and all-cause long-term mortality after EVAR and FEVAR. This may be partially a reflection of aging and cardiovascular comorbidity but needs to be studied further.

Racial Disparities in the Cardiac Computed Tomography Assessment of Coronary Artery Disease: Does Gender Matter

Coronary heart disease (CHD) represents a significant healthcare burden in terms of hospital resources, morbidity, and mortality. Primary prevention and early detection of risk factors for the development of CHD are pivotal to successful intervention programs and prognostication. Yet, there remains a paucity of evidence regarding differences in the assessment of these risk factors and the tools of assessment among different ethnicities. We conducted a narrative review to assess the utility of cardiac computed tomography, particularly coronary artery calcification (CAC), in different ethnicities. We also looked to see whether age, sex, comorbidities, and genetic background have peculiar influences on CAC. In this review, we highlight some of the pivotal studies regarding the question of CAC in relation to the development of CHD among different ethnicities. We identify several key trends in the literature showing that although African Americans have high rates of CHD, their risk of CAC may be relatively lower compared with other ethnicities. Similarly, South Asian patients may be at a high risk for adverse cardiac events due to elevated CAC. We also note that several studies are limited by small sample size and were based on 1 large cohort study. Future studies should include a large international prospective cohort to truly evaluate the effects of ethnicity on CAC and CHD risk. To appropriately apply CAC in the clinical practice, the variations in its scoring based on a subject's age, sex, comorbidity, and ethnicity should be addressed and interpreted beforehand.

Predictive Value of Age- and Sex-Specific Nomograms of Global Plaque Burden on Coronary Computed Tomography Angiography for Major Cardiac Events

BACKGROUND

Age-adjusted coronary artery disease (CAD) burden identified on coronary computed tomography angiography predicts major adverse cardiovascular event (MACE) risk; however, it seldom contributes to clinical decision making because of a lack of nomographic data. We aimed to develop clinically pragmatic age- and sex-specific nomograms of CAD burden using coronary computed tomography angiography and to validate their prognostic use.

METHODS AND RESULTS

Patients prospectively enrolled in phase I of the CONFIRM registry (Coronary CT Angiography Evaluation for Clinical Outcomes) were included (derivation cohort: n=21,132; 46% female) to develop CAD nomograms based on age-sex percentiles of segment involvement score (SIS) at each year of life (40-79 years). The relationship between SIS age-sex percentiles (SIS%) and MACE (all-cause death, myocardial infarction, unstable angina, and late revascularization) was tested in a nonoverlapping validation cohort (phase II, CONFIRM registry; n=3030, 44% female) by stratifying patients into 3 SIS% groups (≤50th, 51-75th, and >75th) and comparing annualized MACE rates and time to MACE using multivariable Cox proportional hazards models adjusting for Framingham risk and chest pain typicality. Age-sex percentiles were well fitted to second-order polynomial curves (men: R²=0.86±0.12; women: R²=0.86±0.14). Using the nomograms, there were 1576, 965, and 489 patients, respectively, in the ≤50th, 51-75th, and >75th SIS% groups. Annualized event rates were higher among patients with greater CAD burden (2.1% [95% confidence interval: 1.7%-2.7%], 3.9% [95% confidence interval: 3.0%-5.1%], and 7.2% [95% confidence interval: 5.4%-9.6%] in ≤50th, 51-75th, and >75th SIS% groups, respectively; P<0.001). Adjusted MACE risk was significantly increased among patients in SIS% groups above the median compared with patients below the median (hazard ratio [95% confidence interval]: 1.9 [1.3-2.8] for 51-75th SIS% group and 3.4 [2.3-5.0] for >75th SIS% group; P<0.01 for both).

CONCLUSIONS

We have developed clinically pragmatic age- and sex-specific nomograms of CAD prevalence using coronary computed tomography angiography findings. Global plaque burden measured using SIS% is predictive of cardiac events independent of traditional risk assessment.

CLINICAL TRIAL REGISTRATION

URL: https://www.clinicaltrials.gov. Unique identifier: NCT01443637.

[Prevalence and extent of coronary artery calcification in an asymptomatic cardiovascular Mexican population: Genetics of Atherosclerotic Disease study]

OBJECTIVE

The prevalence of coronary artery calcification (CAC), a specific marker of atherosclerosis, is unknown in Mexico. Our aim was to investigate the prevalence and quantity of CAC and their association with cardiovascular risk factors in a Mexican population.

METHODS

CAC was measured by multidetector computed tomography in asymptomatic subjects who participated in the Genetics of Atherosclerotic Disease study. Cardiovascular risk factors and medication were recorded.

RESULTS

The sample included 1,423 individuals (49.5% men), aged 53.7±8.4 years. Those with CAC showed a higher prevalence of dyslipidaemia, diabetes, hypertension, and other risk factors. The prevalence of CAC>0 Agatston units was significantly higher among men (40%) than among women (13%). Mean values of CAC score increased consistently with increasing age and were higher in men than women in each age group. Age and high low density lipoprotein cholesterol were independently associated with prevalence of CAC>0 in men and women, while increasing systolic blood pressure in women and age in both genders showed an independent association with CAC extension.

CONCLUSIONS

In the Mexican population the prevalence and extent of CAC were much higher in men than in women, and strongly increased with age. Independent predictors of CAC prevalence were age and low density lipoprotein cholesterol (LDL-C).

Korean guidelines for the appropriate use of cardiac CT

The development of cardiac CT has provided a non-invasive alternative to echocardiography, exercise electrocardiogram, and invasive angiography and cardiac CT continues to develop at an exponential speed even now. The appropriate use of cardiac CT may lead to improvements in the medical performances of physicians and can reduce medical costs which eventually contribute to better public health. However, until now, there has been no guideline regarding the appropriate use of cardiac CT in Korea. We intend to provide guidelines for the appropriate use of cardiac CT in heart diseases based on scientific data. The purpose of this guideline is to assist clinicians and other health professionals in the use of cardiac CT for diagnosis and treatment of heart diseases, especially in patients at high risk or suspected of heart disease.

Vascular calcification in diabetes: mechanisms and implications

Cardiovascular disease (CVD) remains the leading cause of death among adults with diabetes, and CVD prevention remains a major challenge. Coronary artery calcium (CAC) score measured by electron beam tomography (EBT) or multi-slice detector computed tomography correlates closely with plaque burden and coronary angiography, and predicts coronary events independently of other risk factors. Further, progression of CAC over several years has been shown to predict increased mortality. Coronary calcification is an active process strongly associated with atherosclerotic plaque evolution and is an accepted surrogate endpoint in studies of patients with diabetes older than 30. In this review, recent findings regarding the mechanisms and implications of vascular calcification in diabetes will be discussed.

Coronary artery calcium screening in persons with metabolic syndrome and diabetes: implications for prevention

Abstract Diabetes and metabolic syndrome are major risk factors for coronary heart disease (CHD). Many patients suffering CHD events are not adequately identified by traditional risk assessment, suggesting the need for early detection of subclinical CHD to identify those at highest risk. Coronary artery calcium (CAC) screening has added utility in categorizing patients with intermediate and high risk of CHD events, and a growing body of evidence suggests its use for CHD risk assessment in persons with metabolic syndrome and diabetes mellitus. These studies demonstrate the presence and extent of CAC to be greater in those with these conditions, compared to those without, and that CHD risk varies greatly according to the extent of CAC both in persons with and without metabolic syndrome and diabetes mellitus. More recently, guidelines regarding the use of CAC screening have been extended to those with diabetes mellitus, helping to further stratify those patients that may benefit from more intensive therapy. This review evaluates the role and possible benefits of CAC screening, with a focus on those with metabolic syndrome and diabetes mellitus for evaluating the risk for CHD.

Current techniques for MR imaging of atherosclerosis

Vessel wall imaging of large vessels has the potential to identify culprit atherosclerotic plaques that lead to cardiovascular events. Comprehensive assessment of atherosclerotic plaque size, composition, and biological activity is possible with magnetic resonance imaging (MRI). Magnetic resonance imaging of the atherosclerotic plaque has demonstrated high accuracy and measurement reproducibility for plaque size. The accuracy of in vivo multicontrast MRI for identification of plaque composition has been validated against histological findings. Magnetic resonance imaging markers of plaque biological activity such as neovasculature and inflammation have been demonstrated. In contrast to other plaque imaging modalities, MRI can be used to study multiple vascular beds noninvasively over time. In this review, we compare the status of in vivo plaque imaging by MRI to competing imaging modalities. Recent MR technological improvements allow fast, accurate, and reproducible plaque imaging. An overview of current MRI techniques required for carotid plaque imaging including hardware, specialized pulse sequences, and processing algorithms are presented. In addition, the application of these techniques to coronary, aortic, and peripheral vascular beds is reviewed.

Coronary artery calcium, brain function and structure: the AGES-Reykjavik Study

BACKGROUND AND PURPOSE

Several cardiovascular risk factors are associated with cognitive disorders in older persons. Little is known about the association of the burden of coronary atherosclerosis with brain structure and function.

METHODS

This is a cross-sectional analysis of data from the Age, Gene, Environment Susceptibility (AGES)-Reykjavik Study cohort of men and women born 1907 to 1935. Coronary artery calcification (CAC), a marker of atherosclerotic burden, was measured with CT. Memory, speed of processing, and executive function composites were calculated from a cognitive test battery. Dementia was assessed in a multistep procedure and diagnosed according to international guidelines. Quantitative data on total intracranial and tissue volumes (total, gray matter volume, white matter volume, and white matter lesion volume), cerebral infarcts, and cerebral microbleeds were obtained with brain MRI. The association of CAC with dementia (n=165 cases) and cognitive function in nondemented subjects (n=4085), and separately with MRI outcomes, was examined in multivariate models adjusting for demographic and vascular risk factors. Analyses tested whether brain structure mediated the associations of CAC to cognitive function.

RESULTS

Subjects with higher CAC were more likely to have dementia and lower cognitive scores, more likely to have lower white matter volume, gray matter volume, and total brain tissue, and to have more cerebral infarcts, cerebral microbleeds, and white matter lesions. The relations of cognitive performance and dementia to CAC were significantly attenuated when the models were adjusted for brain lesions and volumes.

CONCLUSIONS

In a population-based sample, increasing atherosclerotic load assessed by CAC is associated with poorer cognitive performance and dementia, and these relations are mediated by evidence of brain pathology.

Towards cardiovascular risk stratification using imaging data

In spite of the advancement and proliferation of cardiovascular imaging data, the rate of deaths due to unpredicted heart attack remains high. Thus, it becomes imperative to develop novel computational tools to mine quantitative parameters from imaging data for early detection and diagnosis of asymptomatic cardiovascular disease. In this paper, we present our progress towards developing a computational framework to mine cardiac imaging data and provide quantitative measures for developing a new risk assessment method. Specifically, we present computational methods developed for the detection of coronary calcification and segmentation of thoracic aorta in non-contrast cardiac computed tomography, and detection of neovessels in plaques in intravascular ultrasound imaging data.

A supervised classification-based method for coronary calcium detection in non-contrast CT

Accurate quantification of coronary artery calcium provides an opportunity to assess the extent of atherosclerosis disease. Coronary calcification burden has been reported to be associated with cardiovascular risk. Currently, an observer has to identify the coronary calcifications among a set of candidate regions, obtained by thresholding and connected component labeling, by clicking on them. To relieve the observer of such a labor-intensive task, an automated tool is needed that can detect and quantify the coronary calcifications. However, the diverse and heterogeneous nature of the candidate regions poses a significant challenge. In this paper, we investigate a supervised classification-based approach to distinguish the coronary calcifications from all the candidate regions and propose a two-stage, hierarchical classifier for automated coronary calcium detection. At each stage, we learn an ensemble of classifiers where each classifier is a cost-sensitive learner trained on a distinct asymmetrically sampled data subset. We compute the relative location of the calcifications with respect to a heart-centered coordinate system, and also use the neighboring regions of the calcifications to better characterize their properties for discrimination. Our method detected coronary calcifications with an accuracy, sensitivity and specificity of 98.27, 92.07 and 98.62%, respectively, for a testing dataset of non-contrast computed tomography scans from 105 subjects.

Premature coronary artery calcification is associated with disease duration and bone mineral density in young female systemic lupus erythematosus patients

Our objective was to evaluate the relevance of traditional and disease-related cardiovascular risk factors and of bone mineral density for premature coronary artery calcification in young patients with systemic lupus erythematosus. Ninety-four female patients with systemic lupus erythematosus with disease durations >5 years and <45 years were consecutively selected. Cardiovascular risks (diabetes mellitus, arterial hypertension, dyslipoproteinemia, smoking, family history, body mass index, ovarian and renal insufficiency) and systemic lupus erythematosus-related risk factors (disease duration, ACR criteria, modified SLICC/ ACR, SLEDAI and treatment) were evaluated. Bone mineral density was assessed by dual X-ray absorptiometry. Coronary artery calcification was determined by computed tomography. Coronary artery calcification was identified in 12 (12.7%) patients and was associated with a higher frequency of patients with cardiovascular risks (p = 0.001), higher number of cardiovascular risks (p = 0.002), age (p = 0.025), disease duration (p = 0.011) and SLICC (p=0.011). Individual analysis of cardiovascular risks demonstrated that menopause (p = 0.036), dyslipidemia (p = 0.003) and hypertension (p = 0.006) were significantly associated with coronary artery calcification. In addition, coronary artery calcification was associated with a lower whole body bone mineral density (p = 0.013). Multiple logistic regression analysis using cardiovascular risks, age, disease duration, SLICC and whole body bone mineral density revealed that only disease duration (p = 0.038) and whole body bone mineral density (p = 0.021) remained significant for coronary artery calcification. In conclusion, we found that disease duration and decreased bone mineral density are independent predictors for premature coronary calcification in young women with systemic lupus erythematosus, suggesting a common underlying mechanism. Lupus (2010) 19, 27—33.

Diagnostic and prognostic value of absence of coronary artery calcification

OBJECTIVES

In this study, we systematically assessed the diagnostic and prognostic value of absence of coronary artery calcification (CAC) in asymptomatic and symptomatic individuals.

BACKGROUND

Presence of CAC is a well-established marker of coronary plaque burden and is associated with a higher risk of adverse cardiovascular outcomes. Absence of CAC has been suggested to be associated with a very low risk of significant coronary artery disease, as well as minimal risk of future events.

METHODS

We searched online databases (e.g., PubMed and MEDLINE) for original research articles published in English between January 1990 and March 2008 examining the diagnostic and prognostic utility of CAC.

RESULTS

A systematic review of published articles revealed 49 studies that fulfilled our criteria for inclusion. These included 13 studies assessing the relationship of CAC with adverse cardiovascular outcomes in 64,873 asymptomatic patients. In this cohort, 146 of 25,903 patients without CAC (0.56%) had a cardiovascular event during a mean follow-up period of 51 months. In the 7 studies assessing the prognostic value of CAC in a symptomatic population, 1.80% of patients without CAC had a cardiovascular event. Overall, 18 studies demonstrated that the presence of any CAC had a pooled sensitivity and negative predictive value of 98% and 93%, respectively, for detection of significant coronary artery disease on invasive coronary angiography. In 4,870 individuals undergoing myocardial perfusion and CAC testing, in the absence of CAC, only 6% demonstrated any sign of ischemia. Finally, 3 studies demonstrated that absence of CAC had a negative predictive value of 99% for ruling out acute coronary syndrome.

CONCLUSIONS

On the basis of our review of more than 85,000 patients, we conclude that the absence of CAC is associated with a very low risk of future cardiovascular events, with modest incremental value of other diagnostic tests in this very low-risk group.

Coronary calcium predicts events better with absolute calcium scores than age-sex-race/ethnicity percentiles: MESA (Multi-Ethnic Study of Atherosclerosis)

OBJECTIVES

In this study, we aimed to establish whether age-sex-specific percentiles of coronary artery calcium (CAC) predict cardiovascular outcomes better than the actual (absolute) CAC score.

BACKGROUND

The presence and extent of CAC correlates with the overall magnitude of coronary atherosclerotic plaque burden and with the development of subsequent coronary events.

METHODS

MESA (Multi-Ethnic Study of Atherosclerosis) is a prospective cohort study of 6,814 asymptomatic participants followed for coronary heart disease (CHD) events including myocardial infarction, angina, resuscitated cardiac arrest, or CHD death. Time to incident CHD was modeled with Cox regression, and we compared models with percentiles based on age, sex, and/or race/ethnicity to categories commonly used (0, 1 to 100, 101 to 400, 400+ Agatston units).

RESULTS

There were 163 (2.4%) incident CHD events (median follow-up 3.75 years). Expressing CAC in terms of age- and sex-specific percentiles had significantly lower area under the receiver-operating characteristic curve (AUC) than when using absolute scores (women: AUC 0.73 versus 0.76, p = 0.044; men: AUC 0.73 versus 0.77, p < 0.001). Akaike's information criterion indicated better model fit with the overall score. Both methods robustly predicted events (>90th percentile associated with a hazard ratio [HR] of 16.4, 95% confidence interval [CI]: 9.30 to 28.9, and score >400 associated with HR of 20.6, 95% CI: 11.8 to 36.0). Within groups based on age-, sex-, and race/ethnicity-specific percentiles there remains a clear trend of increasing risk across levels of the absolute CAC groups. In contrast, once absolute CAC category is fixed, there is no increasing trend across levels of age-, sex-, and race/ethnicity-specific categories. Patients with low absolute scores are low-risk, regardless of age-, sex-, and race/ethnicity-specific percentile rank. Persons with an absolute CAC score of >400 are high risk, regardless of percentile rank.

CONCLUSIONS

Using absolute CAC in standard groups performed better than age-, sex-, and race/ethnicity-specific percentiles in terms of model fit and discrimination. We recommend using cut points based on the absolute CAC amount, and the common CAC cut points of 100 and 400 seem to perform well.

Family history of premature coronary heart disease and coronary artery calcification: Multi-Ethnic Study of Atherosclerosis (MESA)

BACKGROUND

A family history of premature coronary heart disease (CHD) is a known risk factor for CHD events. The purpose of this study was to assess the strength of the association between a family history of premature CHD and coronary artery calcification (CAC) in a multiethnic cohort of asymptomatic individuals. We also sought to determine whether individuals with a reported family history of premature CHD have an increased atherosclerotic burden among those classified as being at low to intermediate risk on the basis of the conventional Framingham risk score.

METHODS AND RESULTS

The association of family history of premature CHD with CAC was assessed in 5347 asymptomatic individuals (47% men; mean age 62+/-10 years) in the Multi-Ethnic Study of Atherosclerosis (MESA). The demographics (age, gender, and race)-adjusted OR for CAC > 0 with versus without a family history of premature CHD was 1.94 (95% CI, 1.64 to 2.29). On adjustment for CHD risk factors, the association was slightly attenuated to an OR of 1.84 (95% CI, 1.55 to 2.19). Family history of premature CHD was significantly associated with CAC in all ethnic groups. The age-, gender-, and race-adjusted prevalence of CAC > 0 was significantly higher with presence of any family history of premature CHD than for those with no family history of premature CHD among individuals classified as low risk (35% versus 23%, P<0.0001) and among those at intermediate risk (70% versus 60%, P=0.01). Similarly, the prevalence of age-gender-race-based CAC > or = 75th percentile in low-risk (24% versus 14%, P=0.0003) and intermediate-risk (34% versus 20%, P<0.001) individuals was also higher among those with a family history of premature CHD. Compared with those without a family history of premature CHD, the association with the presence of CAC was strongest in participants reporting such history in both a parent and a sibling (odds ratio, 2.74; 95% CI, 1.64 to 4.59), followed by those reporting a family history in a sibling only (odds ratio, 2.06; 95% CI, 1.64 to 2.58) and those reporting a family history of premature CHD only in a parent (odds ratio, 1.52; 95% CI, 1.19 to 1.93).

CONCLUSIONS

An association between family history of premature CHD and the presence of any CAC, as well as advanced CAC, was observed in the present population-based multiethnic study. The relationship was independent of other risk factors and Framingham risk score, which supports the utility of including information on family history of premature CHD in current methods of global risk assessment and practice guidelines.

Measurement of coronary calcium scores or exercise testing as initial screening tool in asymptomatic subjects with ST-T changes on the resting ECG: an evaluation study

BACKGROUND

Asymptomatic subjects at intermediate coronary risk may need diagnostic testing for risk stratification. Both measurement of coronary calcium scores and exercise testing are well established tests for this purpose. However, it is not clear which test should be preferred as initial diagnostic test. We evaluated the prevalence of documented coronary artery disease (CAD) according to calcium scores and exercise test results.

METHODS

Asymptomatic subjects with ST-T changes on a rest ECG were selected from the population based PREVEND cohort study and underwent measurement of calcium scores by electron beam tomography and exercise testing. With calcium scores > or =10 or a positive exercise test, myocardial perfusion imaging (MPS) or coronary angiography (CAG) was recommended. The primary endpoint was documented obstructive CAD (>/=50% stenosis).

RESULTS

Of 153 subjects included, 149 subjects completed the study protocol. Calcium scores > or =400, 100-399, 10-99 and <10 were found in 16, 29, 18 and 86 subjects and the primary endpoint was present in 11 (69%), 12 (41%), 0 (0%) and 1 (1%) subjects, respectively. A positive, nondiagnostic and negative exercise test was present in 33, 27 and 89 subjects and the primary endpoint was present in 13 (39%), 5 (19%) and 6 (7%) subjects, respectively. Receiver operator characteristics analysis showed that the area under the curve, as measure of diagnostic yield, of 0.91 (95% CI 0.84-0.97) for calcium scores was superior to 0.74 (95% CI 0.64-0.83) for exercise testing (p = 0.004).

CONCLUSION

Measurement of coronary calcium scores is an appropriate initial non-invasive test in asymptomatic subjects at increased coronary risk.

Coronary calcium progression rates with a zero initial score by electron beam tomography

BACKGROUND

A review of existing literature shows that for individuals with initial coronary calcium scores (CCS) of zero it would be reasonable to consider follow-up scanning no sooner than 3 years from the initial evaluation, however the data is very limited. In this study, we sought to determine the rate of new calcifications in patients initially presenting with a zero initial score on electron beam tomography (EBT).

METHODS AND RESULTS

We evaluated 710 physician-referred participants (253 women and 448 men, mean age=56+/-9 years [range=29 to 93]) with no coronary artery calcium (CAC) at baseline electron beam tomography (EBT) scan. The participants underwent a follow-up scan at least 12 months apart. In our study, 248 (35%) were followed for 1-3 years, 256 (36%) for 3-5 years and 204 (29%) for >5 years, respectively. Overall, more than half of the individuals (62%) did not develop any CAC (score remained zero) in the interim period, whereas only 2% had CAC progression >50 during the follow-up. The overall median (interquartile range) and mean+/-S.D. change/year in these individuals was 0 (0-0.8) and 1+/-3, respectively. Only 11 (2%) had CAC progression/year of 11-50, whereas 3 (1%) had CAC change/year >50. It is interesting to note that even among individuals with long-term follow-up (>5 years), very few individuals (2%) had CAC progression >50. Individuals with follow-up 3-5 years did not have a significantly higher odds ratio for CAC change >10 (p=0.17) as compared to the reference group (follow-up of 1-3 years). All the other individuals who had a longer follow-up (>5 years) had a significantly higher likelihood of CAC progression >10 (OR=6.6, 95% CI=2.6-16.9, p<0.0001) compared to the reference group.

CONCLUSION

In individuals with no detectable coronary calcium on an initial EBT scan, a repeat scan can be recommended no sooner than 5 years.

Sixty-four–slice computed tomographic coronary angiography: will the “triple rule out” change chest pain evaluation in the ED?

Sixty-four-slice computed tomographic (CT) coronary angiography is a new technique for the noninvasive visualization of the coronary arteries. It enables noninvasive detection of coronary plaque and determination of severity without instrumentation of the heart. Although not yet commonly used in the emergency department setting, it stands poised to dramatically change the way that patients with chest pain are evaluated. In addition to evaluation of the coronary arteries, CT angiography has long been used to evaluate patients for other dangerous causes of chest pain such as aortic dissection and pulmonary embolus. Although these new scanners excel at all of these diagnostic modalities, the true excitement is in the possibility of combining several different protocols into one, allowing for multiple causes of chest pain to be "ruled out" simultaneously. This article describes the current state of the art of cardiac CT, current state of research, and current areas of controversy.

Prevalence and predictors of cardiovascular calcium in chronic kidney disease (from the Prospective Longitudinal RRI-CKD Study)

Although the determinants of cardiovascular calcium have been well described in dialysis patients, the prevalence and predictors in predialysis chronic kidney disease (CKD) are less known. One hundred six patients with CKD from the Renal Research Institute-CKD Study underwent multidetector computed tomography for the assessment of calcium deposition at the level of coronary arteries, thoracic aorta, aortic valve, and mitral valve. Cardiovascular risk factors and renal function-related parameters (glomerular filtration rate, glomerular filtration rate slope, serum creatinine, serum urea nitrogen, hemoglobin, albumin, calcium, phosphate, and parathyroid hormone) were included in multivariate regression models to predict cardiovascular calcium. Prevalences of calcium deposition at the level of coronary arteries, thoracic aorta, aortic valve, and mitral valve were 69%, 46%, 39%, and 16%, respectively. On multivariate analysis, coronary artery calcium score was predicted by age (p < 0.0001), gender (p = 0.0001), diabetes (p = 0.024), and history of coronary artery disease (p = 0.016), but not by renal function related parameters. Similarly, renal function related parameters were not predictive of aortic or valvular calcium. In conclusion, predialysis CKD is associated with a high prevalence of cardiovascular calcium. The extent of cardiovascular calcium in patients with predialysis CKD is related to some of the traditional risk factors for atherosclerosis but not to indexes of abnormal renal function or progression in renal dysfunction.

Coronary artery calcium as a measure of biologic age

BACKGROUND

Age is assigned a heavy weight in the calculation of the total cardiovascular risk score but often the atherosclerotic disease burden varies from a patient's chronological age.

METHODS

We used measures of coronary artery calcium to estimate the number of life years lost (calcium-adjusted age) in 10,377 asymptomatic individuals referred for electron beam tomography (EBT) screening and followed for 5 years for all-cause mortality. Linear regression was used to calculate predicted age and time to death was estimated via a Cox proportional hazard model.

RESULTS

There was a direct relationship between coronary artery calcium and observed age (r = 0.32, p < 0.0001). In linear prediction models, a calcium score < 10 resulted in a reduction in observed age by 10 years in subjects older than 70 years, while a calcium score > 400 added as much as 30 years of age to younger patients. Calcium-adjusted age was a better predictor of mortality (model chi2 = 373, p < 0.0001) than observed age (model chi2 = 355, p < 0.0001). Detectable calcium was noted in 16% of men and 12% of women with an unadjusted low risk Framingham score (p < 0.0001). For those with an intermediate Framingham risk score, calcium scores > 10 were noted in 31 and 43% of men and women (p < 0.0001). Using calcium-adjustments to age, 55% of previously low risk Framingham scores to intermediate risk (p < 0.0001). Similarly, 45% of the unadjusted intermediate Framingham risk scores were re-classified as high risk based upon calcium-adjusted ages (p < 0.0001).

CONCLUSIONS

Measures of coronary artery calcium are related to survival and can be used to assess an individual's biological age. Undetected risk based upon current calculations of the Framingham risk may be improved based upon determination of a re-adjustment of a patient's age using the extent of coronary calcification.

Assessment of coronary plaque morphology by contrast-enhanced computed tomographic angiography: comparison with intravascular ultrasound

BACKGROUND

Computed tomographic (CT) angiography provides accurate noninvasive assessment for coronary artery stenosis. The ability of CT angiography to determine plaque morphology remains unclear.

METHODS

Twelve patients undergoing intravascular ultrasound for clinical indications underwent CT angiography for the evaluation of plaque morphology. Plaque morphology was classified as (1) soft, (2) fibrous, (3) fibrocalcific or (4) calcific. CT angiography data sets were evaluated for the presence and morphology of plaque in the coronary artery segments. The results were blindly compared with intravascular ultrasound results on a segment by segment basis using angiographic landmarks.

RESULTS

Fifty-nine coronary segments were analyzed; 10 segments were normal and 49 contained plaque. Plaque morphology by intravascular ultrasound was soft in 12 segments, fibrous in four, fibrocalcific in 29 and calcific in four. To determine coronary segments with any plaque, CT angiography had a sensitivity of 100% (49 of 49) and specificity of 90% (9 of 10). To determine plaque morphology as calcified (fibrocalcific and calcific) versus noncalcified (soft and fibrous), CT angiography had a sensitivity of 100% (33 of 33) and a specificity of 94% (15 of 16). Overall accuracy for CT angiography to determine plaque morphology was 92% (54 of 59). CT angiography density values (Hounsfield units, mean+/-standard deviation) were significantly different for each plaque morphology: soft 23+/-71, fibrous 108+/-79, fibrocalcific 299+/-112 and calcific 404+/-264 (P<0.0001).

CONCLUSIONS

CT angiography accurately characterized plaque morphology and may be a useful tool in noninvasive evaluation of plaque morphology during drug therapy trials.

Computed Tomographic Cardiovascular Imaging

Over the last decade, there has been increased recognition that atherosclerosis imaging adds greatly to the ability to identify patients at high risk for cardiac events. Technologies such as electron beam computed tomography and carotid intimal media thickness have contributed significantly to our understanding of the prevalence of preclinical atherosclerosis and its consequences. Current data suggest that elevated calcium scores are predictive of future cardiac events, independently and incrementally to traditional cardiac risk factors. The approximate predictive power is 10-fold for scores > 100, based upon current studies now reported. Guidelines and policy toward these modalities have shifted, with increased recognition of the importance among experts in cardiology, lipidology, and preventive medicine. Because most adverse events related to atherosclerosis occur in individuals at an intermediate risk, data suggest that it will be most cost-effective to concentrate screening efforts on this group of patients. This article reviews the current understanding of the value of coronary artery calcium screening in asymptomatic and symptomatic patients. Accurate measurement of subclinical coronary atherosclerosis should significantly improve the accuracy of global cardiovascular risk prediction, and allow for tracking of atherosclerosis burden, as well as better prediction of future cardiovascular events. Finally, by identifying high-risk patients, CAC may help select those patients who would benefit most from additional testing (e.g., non-invasive stress imaging) and intensification of medical therapy; CAC should have a significant impact on early detection and management of CAD.

Prognostic value of coronary artery calcium screening in asymptomatic smokers and non-smokers

AIMS

To determine the extent and prognostic significance of coronary artery calcium in asymptomatic smokers and non-smokers. Population data are available on the prognostic impact of smoking on atherosclerotic imaging measurements of the carotid and peripheral arteries. Limited data are available on the impact of cigarette smoking on the prognostic value of coronary calcium.

METHODS AND RESULTS

A referred patient registry of 10,377 asymptomatic individuals (40% were current smokers) was followed for death from all-causes at 5 years. Univariable and multivariable Cox proportional hazard models were calculated to estimate time to all-cause mortality. Cumulative 5-year survival was 96.9 and 98.4% for smokers when compared with non-smokers (P < 0.0001). Using a stratified Cox proportional hazards survival analysis, survival for non-smokers ranged from 99.7 to 89.6% with calcium score of 0-10 and >1000 (P < 0.0001). In comparison, smokers had survival rates ranging from 99.5 to 81.4% for calcium score of 0-10 to >1000 (P < 0.0001). When further evaluating the effect of age on prognosis by coronary calcium, there was an additive relationship between age and calcium that was exacerbated with smoking, resulting in higher relative risk ratios for older smokers with coronary calcium (P < 0.0001). For smokers <50 years of age, a calcium score >1000 was associated with a relative risk ratio that was elevated 8.9-fold (P = 0.029). Thus, resulting in an expected reduction in life expectancy of 4.8 years for smokers <50 years of age with a calcium score >400 (P < 0.0001).

CONCLUSION

The prognostic value of coronary artery calcium scoring was accurate in identifying a high-risk cohort of asymptomatic smokers and non-smokers. Young smokers with high-risk calcium scores have a four- to nine-fold increased risk of dying when compared with similarly aged non-smokers. When prospectively applied, evidence of a high-risk calcium score may be useful in educating patients as to their expected risk of dying over the next 5 years.

Effect of Varying Slice Thickness on Coronary Calcium Scoring With Multislice Computed Tomography in Vitro and in Vivo

OBJECTIVES

To compare coronary calcium scoring results (calcium volume, calcium mass, Agatston score, and number of lesions) of different slice thicknesses using a 16-slice CT (MSCT) scanner.

MATERIALS AND METHODS

A nonmoving anthropomorphic thorax phantom with calcium cylinders of different sizes and densities was scanned 30 times with repositioning applying a standardized retrospectively ECG-gated MSCT (SOMATOM Sensation 16; Siemens, Forchheim, Germany) scan protocol: collimation 12 x 0.75 mm, tube voltage 120 kV, effective tube current time-product 133 mAs(eff). Fifty patients (29 male; age 57.2 +/- 8.4 years) underwent a nonenhanced scan applying the same scan protocol. Two image sets (effective slice thicknesses 3 mm and 1 mm) were reconstructed at 60% of the RR interval. Image noise was measured in both studies. Calcium volume, calcium mass and Agatston score were calculated using a commercially available software tool.

RESULTS

Due to increased image noise in thinner slices, calcium scoring in all scans was performed applying a scoring threshold of 350 HU. In the phantom study, 1-mm slices showed significantly higher scoring results in respect to calcium volume (+8.2%), calcium mass (+12.5%), and Agatston score (+5.3%) (all P < 0.0001). In the patient study, 27 patients had coronary calcifications in 3-mm slices, and 31 patients had coronary calcifications in 1-mm slices. Thinner slices showed significantly higher scoring results in respect to volume (+47.1%), mass (+47.2%), and Agatston score (+29.7%) (all P < 0.0001).

CONCLUSIONS

When comparing 3-mm and 1-mm slices in coronary calcium scoring in MSCT, thinner slices lead to significantly increased scoring results.

Update on using coronary calcium screening by computed tomography to measure risk for coronary heart disease

Coronary artery disease (CAD) is the number one killer of adults in the United States, claiming one-half million deaths annually. Early detection and prevention strategies clearly remain a top priority for health care providers in order to reduce the high mortality rate of heart disease. As an unequivocal reflection of arteriosclerosis, coronary arterial calcium (CAC) may provide a means to qualitatively assess the overall disease severity and likewise serve as a means to assess risk for CHD. It is known that patients with heavy calcium burdens have more advanced CAD, a concomitantly a higher likelihood of coronary stenoses, and a concomitant higher risk for acute cardiac events. Computed tomography has been shown to be an accurate, non-invasive method to quantify coronary calcification burden in patients. Evidence shows that calcium measurements by CT correlate well with histological plaque analyses, and that CAC measurements accurately reflect disease severity and can be useful to assess individual risk for CHD. The purpose of this article is to summarize the currently available evidence that has attempted to validate CAC screening as a screening exam and risk predictor for coronary heart disease.

Comparison of coronary artery calcium screening image quality between C-150 and e-Speed electron beam scanners

RATIONALE AND OBJECTIVE

The newest generation of electron beam tomographic scanner (e-Speed) has increased spatial and temporal resolution compared with the C-150 XP scanner. The aim of this study was to evaluate coronary artery calcium screening image quality between the e-Speed and C-150 scanners (GE Imatron, San Francisco, CA).

MATERIALS AND METHODS

Studies from 41 patients (14 women and 27 men) who underwent serial coronary artery calcium screening with the C-150 (first study) and the e-Speed (second study) were analyzed. Individual computed tomography (CT) slices were assessed for coronary artery motion artifacts, and CT Hounsfield units (HU) and noise values (CT HU standard deviation) at 16 discrete cardiac sites were measured and averaged.

RESULTS

With the e-Speed scanner, there were significant decreases in right coronary artery motion artifacts compared with the C-150 scanner (0.3% versus 1.8%, P < .001) as well as decreased noise values (24.3 versus 32.0 HU, P < .001).

CONCLUSION

Image quality is significantly improved with use of the e-Speed scanner, due to its improved temporal and spatial resolution, compared with the C-150 scanner.

Visualising noncalcified coronary plaques by CT

Due to a rapid improvement of the new generation submillimetre multislice CT-technology noninvasive tomographic imaging of the coronary vessel wall has become reality. First clinical studies have shown the ability in particular of 16-slice CT to determine plaque burden, plaque composition and compensatory vessel-wall remodelling. These novel findings already constitute an important step forward to assess coronary atherosclerosis noninvasively in a detailed manner which opens promising new opportunities for a better understanding and riskstratification of coronary atherosclerosis. Current limitations, mainly the insufficient accuracy to detect small lesions in distal coronary segments, might be overcome by improved spatial and temporal resolution of the new generation scanners operating with 64 and more detectors.

Coronary age as a risk factor in the modified Framingham risk score

Background

Clinical guidelines emphasize risk assessment as vital to patient selection for medical primary intervention. However, risk assessment methods are restricted in their ability to predict further coronary events. The most widely accepted tool in the United States is the Framingham risk score. In these equations age is a powerful risk factor. Although the extent of coronary atherosclerosis increases with age, there is large inter-individual variability in the rate of development and progression of this disease. This fact limits the utility of Framingham scoring when applied to individuals. Electron beam tomography (EBT), which measures coronary calcium, provides a non-invasive method for assessing coronary plaque burden, thus offering the possibility of providing a more accurate estimate of an individual's "arterial age" than from chronological age alone.

Methods

In this paper we discuss a new and simple method for incorporating the coronary calcium score (CCS) to modify the Framingham Risk Assessment (FRA). Using this method, a coronary artery calcium (CAC) age equivalent is generated that replaces chronological age in Framingham scoring.

Results and discussion

Using a percentile table of CCS scores by age group and sex, individuals are matched to the age group whose calcium score most closely approximates their own individual score. The original 10-year absolute risk score of a 65-year old man with a CCS of 6 based on chronological age is 10%, whereas the modified absolute risk score based on CAC age equivalents is 2%.

Conclusion

Our approach of replacing chronological age with CAC age equivalents in the Framingham equations possesses simplicity of application combined with precision. Physicians can easily derive adjusted Framingham risk scores and prescribe intervention methods based on patients' ten-year risks. The adjusted ten-year risks are likely to be more accurate than unadjusted risks since they are based on coronary calcium score information. The modified FRA approach not only may increase the predicted risk for some patients, but also may decrease the predicted risk for others, making it a more precise adjustment than other methods.

Accuracy of multidetector spiral computed tomography in identifying and differentiating the composition of coronary atherosclerotic plaques

OBJECTIVES

We evaluated the accuracy of contrast-enhanced multidetector spiral computed tomography (MDCT) for the noninvasive detection and classification of coronary plaques and compared it with intracoronary ultrasound (ICUS).

BACKGROUND

Noninvasive determination of plaque composition and plaque burden may be important to improve risk stratification and to monitor progression of coronary atherosclerosis.

METHODS

We included 46 consecutive patients with a distinctive risk profile, who were investigated by ICUS (Goldvision, 20 MHz, Jomed Inc., Rancho Cordova, California). Due to the inability to slow the heart rate below 65 beats/min (n = 7) and due to renal insufficiency (n = 2), nine of 46 consecutive patients could not be studied by MDCT (Sensation 16, Siemens, Forchheim, Germany).

RESULTS

In the remaining 37 patients, 68 vessels were investigated by ICUS, and 58 of these vessels were visualized by MDCT with image quality sufficient for analysis. In these vessels that were divided in 3-mm sections, MDCT correctly classified 62 of 80 (78%) sections containing hypoechoic plaque areas, 87 of 112 (78%) sections containing hyperechoic plaque areas, and 150 of 158 (95%) sections containing calcified plaque tissue. In 484 of 525 (92%) sections, atherosclerotic lesions were correctly excluded. The MDCT-derived density measurements within coronary lesions revealed significantly different values for hypoechoic (49 HU [Hounsfield Units] +/- 22), hyperechoic (91 HU +/- 22), and calcified plaques (391 HU +/- 156, p < 0.02).

CONCLUSIONS

This study demonstrates that, in the case of diagnostic image quality, contrast-enhanced MDCT permits an accurate identification of coronary plaques and that computed tomography density values measured within plaques reflect echogenity and plaque composition.

Coronary artery calcification and cardiovascular risk factors: impact of the analytic approach

Coronary artery calcification (CAC) may help identify novel risk factors for coronary atherosclerosis. However, analysis of CAC is challenging because of the distribution of CAC in the population. This has resulted in difficulty in interpreting and comparing results across studies. We applied several analytic approaches to CAC data in order to determine the impact of analytic methods on the association with established cardiovascular risk factors in 914 asymptomatic subjects in the Study of Inherited Risk Factors for Coronary Atherosclerosis. Multivariable analyses included: (1) linear regression of different transformations of CAC scores; (2) tobit regression of the log of (CAC + 1); (3) logistic regression using CAC zero as a cut-point; and (4) ordinal logistic regression using CAC categories. Linear regression of the log CAC scores and logistic regression of CAC zero cut-point failed to detect associations with some risk factors. In contrast, linear and tobit regression of the log (CAC + 1) and ordinal regression of CAC categories identified more associations and provided consistent results. Commonly applied methods of CAC analysis may fail to detect associations with cardiovascular risk factors. We present analytic approaches that are likely to provide consistent results and recommend the use of at least two distinct multivariable methods.

Imaging of coronary calcification by computed tomography

As an unequivocal biomarker for arteriosclerosis, the presence of coronary calcium serves as a qualitative reflection of the severity of coronary artery disease (CAD). Greater calcium burdens correlate with more advanced disease, a higher likelihood of coronary stenoses, and a higher risk for coronary heart disease (CHD). Empirically, the quantification of coronary calcium not only provides an accurate reflection of disease severity, but also has great potential as a screening tool for CHD. Computed tomography (CT) has been shown to be capable of providing accurate, noninvasive measurements of coronary calcification. Evidence shows that calcium measurements by CT correlate well with histological plaque analyses, and that calcium burdens accurately reflect disease severity and can be used to assess individual risk for CHD. The purpose of this review article is to examine the accumulated evidence that has attempted to validate CT as a diagnostic tool for CAD and as a screening exam for CHD.