Coronary artery calcium quantification at multi-detector row helical CT versus electron-beam CT

PURPOSE: To compare coronary artery calcium scores from a multi-detector row helical computed tomographic (CT) scanner with those from an electron-beam CT scanner, with emphasis on subjects with calcium scores less than 400. MATERIALS AND METHODS: Seventy-eight asymptomatic subjects (37 women, 41 men; age range, 39-78 years; mean age, 54.2 years) underwent multi-detector row CT and electron-beam CT. Volume and Agatston scores were calculated with a workstation. Statistical analyses included assessment of association between calcium scores from two scanners, calculation of percent absolute difference to assess score variability between scanners, equivalence analysis, construction of Bland-Altman plots to assess agreement between scores, and assessment of changes in score grouping and risk criteria based on score differences between scanners. RESULTS: Electron-beam CT calcium scores were higher than multi-detector row CT scores. Linear association between calcium scores obtained from paired scans was significant (r = 0.96-0.99, P <.001). Mean percent absolute differences were 67.9% and 65.0% for volume and Agatston scores, respectively (48.6% and 46.3% for corresponding natural log-transformed scores). In subjects with a score of 11 or greater, mean percent absolute differences between electron-beam CT and multi-detector row CT scores ranged from 15% to 30% (<10% for natural log-transformed calcium scores). With a 20% equivalence limit, calcium scores from the two scanners were statistically equivalent (P <.05). Score grouping would have been subject to change in 12 (11 increased and one decreased; six with scores of 11 or greater), and possible risk management decisions would have been subject to change in eight (16%) of 51 subjects who underwent electron-beam CT versus multi-detector row CT scanning. CONCLUSION: Multi-detector row CT appears to be comparable to electron-beam CT for coronary calcification screening, except in subjects with a calcium score less than 11.     

Spiral versus electron-beam CT for coronary artery calcium scoring

PURPOSE: To determine differences in coronary artery calcium detection, quantification, and reproducibility, as measured at electron-beam computed tomography (CT) and subsecond spiral CT with retrospective electrocardiogram gating in an asymptomatic adult population. MATERIALS AND METHODS: Seventy subjects asymptomatic for coronary heart disease underwent both electron-beam CT and subsecond spiral CT. In all subjects, two images each were obtained with both scanners. Two experienced readers using three different algorithms scored each of the four scans: one score for the electron-beam CT images and two scores for the spiral CT images. RESULTS: With a 130-HU threshold for the quantification of calcium, there were no significant differences in interscan and interobserver variation in calcium scores between the electron-beam CT and spiral CT images. There was greater interobserver (P <.001) and interscan (P <.03) variation in scores when a 90-HU threshold was used for spiral CT images. With a 130-HU threshold, when calcium scores were used for clinical risk stratification, there was a significant difference between the results obtained with electron-beam CT and those obtained with spiral CT (P <.05). CONCLUSION: Spiral CT has not yet proved to be a feasible alternative to electron-beam CT for coronary artery calcium quantification. There are systematic differences between calcium scores obtained with single-detector array subsecond spiral CT and those obtained with electron-beam CT.     

Causes of interscan variability of coronary artery calcium measurements at electron-beam CT

RATIONALE AND OBJECTIVES: The authors performed this study to investigate the causes of interscan variability of coronary artery calcium measurements at electron-beam computed tomography (CT). MATERIALS AND METHODS: Two sets of electron-beam CT scans were obtained in 298 consecutive patients who underwent electron-beam CT to screen for coronary artery calcium. Interscan variations of coronary artery calcium characteristics and the effects of heart rate, electrocardiographic (ECG) triggering method, image noise, and coronary motion on interscan variability were analyzed. RESULTS: The interscan mean variabilities were 21.6% (median, 11.7%) and 17.8% (median, 10.8%) with the Agatston and volumetric score, respectively (P < .01). Variability decreased with increasing calcification score (34.6% for a score of 11-50 and 9.4% for a score of 400-1,000, P < .0001). The absolute difference in Agatston score between scans was 44.1 +/- 95.6. The correlation coefficient between the first and second sets of scans was 0.99 (P < .0001). Lower interscan variability was found in younger patients (<60 years), patients with stable heart rates (heart rate changing less than 10 beats per minute during scanning), patients with no visible coronary motion, and those with an optimal ECG triggering method (P < .05 for all). Results of multivariate logistic analysis showed that changes in calcium volume, mean attenuation, and peak attenuation were significant predictors of interscan variability and caused the interscan variations of the coronary artery calcium measurements (r2 = 0.83, P < .0001). CONCLUSION: Coronary calcification at electron-beam CT varies from scan to scan. Volumetric scoring and optimal ECG triggering should be used to reduce interscan variability. Baseline calcium score and interscan variability must be considered in the evaluation of calcium progression.     

Calcium begets calcium: progression of coronary artery calcification in asymptomatic subjects

PURPOSE: To test the hypothesis that the rate of coronary artery calcium progression is sex specific, namely, that it is greater in men than in women, and that it is age related, particularly in women. MATERIALS AND METHODS: This was a retrospective study of the progression of coronary artery calcium in 217 consecutive asymptomatic subjects who underwent at least two electron-beam computed tomographic studies of the heart. Calcium in the distribution of the epicardial arteries was quantified by using both the conventional coronary artery calcium score (CCS) and the calcium volume score (CVS). Linear regression models were used to judge the joint influence of various risk factors, including sex and age, on rates of coronary artery calcium progression. RESULTS: This study included 103 women and 114 men. The mean interval between the subjects' first and last studies was 25 months +/- 11 (SD). Regression analyses clearly demonstrated that the amount of coronary artery calcium present at the initial study was the most important determinant of calcium progression. This was true when coronary artery calcium was quantified by using the conventional CCS (P <.001) or CVS (P <.001). Neither sex nor age was a significant predictor of coronary artery calcium progression. Among traditional risk factors, only hypertension (P =.02) and diabetes (P =.01) were significant independent factors for calcium progression. CONCLUSION: In asymptomatic subjects, the initial CCS and CVS were the most important factors that affected rate of coronary artery calcium progression. Neither age nor sex was as important as these factors in determination of coronary artery calcium progression.     

All-cause mortality in asymptomatic persons with extensive Agatston scores above 1000

BackgroundRisk assessment in the extensive calcified plaque phenotype has been limited by small sample size.ObjectiveWe studied all-cause mortality rates among asymptomatic patients with markedly elevated Agatston scores > 1000.MethodsWe studied a clinical cohort of 44,052 asymptomatic patients referred for coronary calcium scans. Mean follow-up was 5.6 years (range, 1–13 years). All-cause mortality rates were calculated after stratifying by Agatston score (0, 1–1000, 1001–1500, 1500–2000, and >2000). A multivariable Cox regression model adjusting for self-reported traditional risk factors was created to assess the relative mortality hazard of Agatston scores 1001 to 1500, 1501 to 2000, and >2000. With the use of post-estimation modeling, we assessed for the presence of an upper threshold of risk with high Agatston scores.ResultsA total of 1593 patients (4% of total population) had Agatston score > 1000. There was a continuous graded decrease in estimated 10-year survival across increasing Agatston score, continuing when Agatston score > 1000 (Agatston score 1001–1500, 78%; Agatston score 1501–2000, 74%; Agatston score > 2000, 51%). After multivariable adjustment, Agatston scores 1001 to 1500, 1501 to 2000, and >2000 were associated with an 8.05-, 7.45-, and 13.26-fold greater mortality risk, respectively, than for Agatston score of 0. Compared with Agatston score 1001 to 1500, Agatston score 1501 to 2000 had a similar all-cause mortality risk, whereas Agatston score > 2000 had an increased relative risk (Agatston score 1501–2000: hazard ratio [HR], 1.01 [95% CI, 0.67–1.51]; Agatston score > 2000: HR, 1.79 [95% CI, 1.30–2.46]). Graphical assessment of the predicted survival model suggests no upper threshold for risk associated with calcified plaque in coronary arteries.ConclusionIncreasing calcified plaque in coronary arteries continues to predict a graded decrease in survival among patients with extensive Agatston score > 1000 with no apparent upper threshold.     

Validation of the Coronary Artery Calcium Data and Reporting System (CAC-DRS): Dual importance of CAC score and CAC distribution from the Coronary Artery Calcium (CAC) consortium

BackgroundThe Coronary Artery Calcium Data and Reporting System (CAC-DRS), which takes into account the Agatston score category (A) and the number of calcified vessels (N) has not yet been validated in terms of its prognostic significance.MethodsWe included 54,678 patients from the CAC Consortium, a large retrospective clinical cohort of asymptomatic individuals free of baseline cardiovascular disease (CVD). CAC-DRS groups were derived from routine, cardiac-gated CAC scans. Cox proportional hazards regression models, adjusted for traditional CVD risk factors, were used to assess the association between CAC-DRS groups and CHD, CVD, and all-cause mortality. CAC-DRS was then compared to CAC score groups and regional CAC distribution using area under the curve (AUC) analysis.ResultsThe study population had a mean age of 54.2 ± 10.7, 34.4% female, and mean ASCVD score 7.3% ± 9.0. Over a mean follow-up of 12 ± 4 years, a total of 2,469 deaths (including 398 CHD deaths and 762 CVD deaths) were recorded. There was a graded risk for CHD, CVD and all-cause mortality with increasing CAC-DRS groups ranging from an all-cause mortality rate of 1.2 per 1,000 person-years for A0 to 15.4 per 1,000 person-years for A3/N4. In multivariable-adjusted models, those with CAC-DRS A3/N4 had significantly higher risk for CHD mortality (HR 5.9 (95% CI 3.6–9.9), CVD mortality (HR4.0 (95% CI 2.8–5.7), and all-cause mortality a (HR 2.5 (95% CI 2.1–3.0) compared to CAC-DRS A0. CAC-DRS had higher AUC than CAC score groups (0.762 vs 0.754, P < 0.001) and CAC distribution (0.762 vs 0.748, P < 0.001).ConclusionThe CAC-DRS system, combining the Agatston score and the number of vessels with CAC provides better stratification of risk for CHD, CVD, and all-cause death than the Agatston score alone. These prognostic data strongly support new SCCT guidelines recommending the use CAC-DRS scoring.     

Reproducibility of electron-beam CT measures of aortic valve calcification

RATIONALE AND OBJECTIVES: The authors performed this study to establish the interscan, interobserver, and intraobserver reproducibility of aortic valve calcification (AVC) measurements obtained with electron-beam computed tomography (CT). MATERIALS AND METHODS: The authors evaluated electron-beam CT scans from all patients who had undergone two serial examinations on the same day as part of a study of coronary artery calcification reproducibility. In patients in whom aortic valve calcium was identified at electron-beam CT, AVC scores were measured with both the Agatston and the volumetric methods, which were developed previously to quantify coronary calcium. RESULTS: Forty-four asymptomatic patients (mean age, 66 years +/- 9) with AVC at electron-beam CT were included in the analyses. AVC score reproducibility was excellent with both the Agatston and the volumetric methods (R2 = 0.99, P = .0001 for both), with median interscan variabilities of 7% and 6.2%, respectively. Interscan reproducibility was similar, whether the analysis included all scans or was restricted to those with scores greater than 10 or greater than 30. For the volumetric method, the median interobserver variability was 5% and the median intraobserver variability was 1%. CONCLUSION: The low interscan, interobserver, and intraobserver variabilities at electron-beam CT suggest that this method should be useful for the noninvasive monitoring of AVC changes over time and for assessing the efficacy of therapies aimed at slowing AVC accumulation.     

Coronary calcium measurements: effect of CT scanner type and calcium measure on rescan reproducibility--MESA study

PURPOSE: To evaluate the effect of scanner type and calcium measure on the reproducibility of calcium measurements. MATERIALS AND METHODS: This investigation was approved by the institutional review boards of each study site and by the Institutional Review Board of the Los Angeles Biomedical Research Institute. Informed consent for scanning and participation was obtained from all participants. The study was Health Insurance Portability and Accountability Act compliant. The Multi-Ethnic Study of Atherosclerosis (MESA) is a multicenter observational study of 6814 participants undergoing demographic, risk factor, and subclinical disease evaluations. Coronary artery calcium was measured by using duplicate CT scans. Three study centers used electron-beam computed tomography (CT), and three used multi-detector row CT. Coronary artery calcium was detected in 3355 participants. Three calcium measurement methods-Agatston score, calcium volume, and interpolated volume score-were evaluated. Mean absolute differences between calcium measures on scans 1 and 2, excluding cases for which both scans had a measure of zero, was modeled by using linear regression to compare reproducibility between scanner types. A repeated measures analysis of variance test was used to compare reproducibility across calcium measures, with mean percentage absolute difference as the outcome measure. Rescan reproducibility in relation to misregistrations, noise, and motion artifacts was also examined. Variables were log transformed to create a more normal distribution. RESULTS: Concordance for presence of calcium between duplicate scans was high and similar for both electron-beam and multi-detector row CT (96%, kappa = 0.92). Mean absolute difference between calcium scores for the two scans was 15.8 for electron-beam and 16.9 for multi-detector row CT scanners (P = .06). Mean relative differences were 20.1 for Agatston score, 18.3 for calcium volume, and 18.3 for interpolated volume score (P < .01). Reproducibility was lower for scans with versus those without image misregistrations or motion artifacts (P < .01 for both). CONCLUSION: Electron-beam and multi-detector row CT scanners have equivalent reproducibility for measuring coronary artery calcium. Calcium volumes and interpolated volume scores are slightly more reproducible than Agatston scores. Reproducibility is lower for scans with misregistrations or motion artifacts.     

Coronary artery calcium scoring in low risk patients with family history of coronary heart disease: Validation of the SCCT guideline approach in the coronary artery calcium consortium

BackgroundThe Society of Cardiovascular Computed Tomography (SCCT) recommends consideration of coronary artery calcium (CAC) scoring among individuals with a family history (FH) of coronary heart disease (CHD) and atherosclerotic cardiovascular disease (ASCVD) risk <5%. No dedicated study has examined the prognostic significance of CAC scoring among this population.MethodsThe CAC Consortium is a multi-center observational cohort study from four clinical centers linked to long-term follow-up for cause-specific mortality. All CAC scans were physician referred and performed in patients without a history of CHD. Our analysis includes 14,169 patients with ASCVD scores <5% and self-reported FH of CHD.ResultsThis cohort had a mean age of 48.1 (SD 7.4), was 91.3% white, 47.4% female, had an average ASCVD score of 2.3% (SD 1.3), and 59.4% had a CAC = 0. The event rate for all-cause mortality was 1.2 per 1000 person-years, 0.3 per 1000 person-years for CVD-specific mortality, and 0.2 per 1000 person-years for CHD-specific mortality. In multivariable Cox proportional hazard models, those with CAC>100 had a 2.2 (95% CI 1.5–3.3) higher risk of all-cause mortality, 4.3 (95% CI 1.9–9.5) times higher risk of CVD-specific mortality, and a 10.4 (95% CI 3.2–33.7) times higher risk of CHD-specific mortality compared to individuals with CAC = 0. The NNS to detect CAC >100 in this sample was 9.ConclusionIn otherwise low risk patients with FH of CHD, CAC>100 were associated with increased risk of all-cause and CHD mortality with event rates in a range that may benefit with preventive pharmacotherapy. These data strongly support new SCCT recommendations regarding testing of patients with a family history of CHD.     

Clinical usefulness of multidetector-row CT to evaluate coronary artery calcium score in type 2 diabetes

PURPOSE: According to recent studies, multidetector-row CT (MDCT) with a retrospective ECG-gating reconstruction algorithm shows a high correlation with coronary artery calcium score determined using electron-beam CT. Diabetes leads to many macrovascular complications, including coronary artery disease. The aim of this study was to evaluate risk factors for cardiac macroangiopathy in type 2 diabetes using MDCT. MATERIALS AND METHODS: An observational cross-sectional study was performed in 90 patients with diabetes mellitus. Coronary calcium data was acquired by MDCT (SOMATOM Volume Zoom, Siemens AG, Medical Solutions, Germany). Physical examinations, laboratory data, glycemic control, and control of other risk factors were analyzed. RESULTS: The coronary artery calcium score increased with age. Multivariant analysis revealed that the coronary calcium score was closely correlated with electrocardiogram evaluation and control of hypertension. CONCLUSIONS: Coronary artery calcium score as determined by MDCT can be used as a screening radiological examination for cardiac macroangiopathy in diabetes patients with electrocardiogram abnormality and hypertension.     

冠状动脉与颈动脉钙化的相关性分析及其危险因素

目的 评价冠状动脉钙化与颈动脉钙化的关系及其危险因素.方法 2周内先后完成冠状动脉和颈动脉CT平扫检查的162例患者,采用相同的重建条件,分别进行钙化积分的测量,用Spearman相关分析进行两者的比较.同时记录患者的性别、年龄、血压、总胆固醇、甘油三脂、高密度脂蛋白(HDL)、低密度脂蛋白(LDL)、糖尿病、吸烟史、冠心病早发病史等,用Logistic回归分析冠状动脉及颈动脉钙化积分与多个临床危险因素之间的关系.结果 在162例患者中,冠状动脉钙化积分(CACS)与颈动脉钙化积分之间存在线性正相关关系,r值为0.690,P<0.01.CACS的危险因素包括年龄、糖尿病、总胆固醇、LDL,颈动脉钙化的危险因素为年龄和糖尿病.结论 冠状动脉钙化与颈动脉钙化呈线性正相关,但冠状动脉与颈动脉钙化的危险因素不完全相同.     

Coronary calcification at electron-beam CT: effect of section thickness on calcium scoring in vitro and in vivo

PURPOSE: To compare the accuracy of electron-beam computed tomography (CT) with 3.0- and 1.5-mm section thickness for calcium quantification and the prevalence of coronary calcifications with each. MATERIALS AND METHODS: Electron-beam CT images were acquired with nonoverlapping 1.5- and 3.0-mm section thickness. Scans were obtained in an anthropomorphic thorax phantom with calcium cylinders of different sizes and densities, as well as in 1,302 study participants. A calcified lesion was defined as a minimum of 2 pixels (area, 0.52 mm2) with a minimum attenuation of 130 HU. The calcified lesions were quantified by means of a volumetric method with isotropic interpolation. From the phantom scans, mean volume scores, SDs, and measurement variations were calculated. From the participant scans, median volume scores and interquartile ranges were calculated. Participants were classified in categories based on cutoff levels for volume score quartiles for the 1.5-mm scans. An intraclass correlation coefficient (kappa value) was calculated as a measure of correlation between categories. RESULTS: In the phantom, deviations of calculated volumes from the true cylinder volumes and measurement variations were generally higher for the 3.0-mm protocol than for the 1.5-mm protocol. In the participants, the median volume score was 100 mm3 (interquartile range, 11-409 mm3) for the 3.0-mm protocol and 144 mm3 (interquartile range, 35-513 mm3) for the 1.5-mm protocol. Agreement between classifications of volume scores for the 1.5- and 3.0-mm scans was good (kappa = 0.62, P <.001). Compared with the quartile classification for the 1.5-mm scan, however, classifications for 370 (28%) participants were put in a different category with the 3.0-mm protocol. CONCLUSION: In a phantom, electron-beam CT scans with 3.0-mm section thickness yield less accurate estimates of calcified volume than do 1.5-mm scans. Electron-beam CT protocols with thinner sections considerably affect classification of individuals on the basis of the amount of coronary calcification depicted.     

Coronary calcium scanning independently detects coronary artery disease in asymptomatic firefighters: A prospective study

BackgroundSudden cardiac death is the leading cause of death among firefighters in the United States. Fire departments commonly maintain physical examination protocols, often with exercise stress testing, to detect risk of coronary heart disease.ObjectiveWe sought to determine whether coronary calcium detected by electron beam computed tomography (EBCT) adds incremental risk stratification beyond the traditional risk factors in asymptomatic community-based firefighters.MethodsThree hundred ninety nine asymptomatic firefighters underwent a coronary calcium scan on a GE/Imatron C-150 Ultrafast EBCT scanner, using standardized imaging protocols. Framingham risk factor data were obtained on each patient by using a questionnaire. Agatston scores were derived and compared with national database of Agatston scores for asymptomatic populations on the basis of age and sex, allowing determination of a calcium percentile for each score.ResultsCoronary calcium was found only in men >34 years of age. Of the 53% who had positive scans (Agatston score > 0), 87% had higher than average Agatston scores compared with a national database (P < 0.01). Agatston score above the 75th percentile was found in 57% of firefighters. No correlation was observed between traditional risk factors and those with and without coronary calcium.ConclusionsFirefighters have a high burden of calcified coronary atherosclerosis, greater than anticipated on the basis of age and coronary risk factors.     

Reproducibility and accuracy of coronary calcium measurements with multi-detector row versus electron-beam CT

PURPOSE: To methodically evaluate the reproducibility and accuracy of coronary arterial calcification measurements by using spiral multi-detector row and electron-beam computed tomography (CT) with a beating heart phantom. MATERIALS AND METHODS: A phantom was built to mimic a beating heart with coronary arteries and calcified plaques. The simulated vessels moved in a pattern similar to that of a beating heart. The phantom operated at a variety of pulse rates (0-140 beats per minute). The phantom was repeatedly scanned in various positions by using various protocols with electron-beam and multi-detector row CT scanners to assess interexamination variability. Statistical analysis was performed to determine significant differences in interexamination variability for various acquisition protocols. RESULTS: Electrocardiographically (EKG) gated volume coverage with spiral multi-detector row CT (2.5-mm collimation) and overlapping image reconstruction (1-mm increment) was found to significantly improve the reliability of coronary arterial calcium quantification, especially for small plaques (P <.05). Mean interexamination variability was reduced from 35% +/- 6 (SD) (Agatston score, standard electron-beam CT) to 4% +/- 2 (P <.05) (volumetric score, spiral EKG-gated multi-detector row CT). CONCLUSION: By coupling retrospective gating with nearly isotropic volumetric imaging data, spiral multi-detector row CT provides better input data for quantification of coronary arterial calcium volume. Multi-detector row CT allows precise and repeated measurement of coronary arterial calcification, with low interexamination variability.     

Prognostic significance of calcified plaque among symptomatic patients with nonobstructive coronary artery disease

Background

Coronary artery calcium (CAC) is a well-established predictor of clinical outcomes for population screening. Limited evidence is available as to its predictive value in symptomatic patients without obstructive coronary artery disease (CAD). The aim of the current study was to assess the prognostic value of CAC scores among symptomatic patients with nonobstructive CAD.

Methods

From the COronary Computed Tomographic Angiography EvaluatioN For Clinical Outcomes: An InteRnational Multicenter (CONFIRM) registry, 7,200 symptomatic patients with nonobstructive CAD (<50% coronary stenosis) on coronary-computed tomographic angiography were prospectively enrolled and followed for a median of 2.1 years. Patients were categorized as without (0% stenosis) or with (>0% but <50% coronary stenosis) a luminal stenosis. CAC scores were calculated using the Agatston method. Univariable and multivariable Cox proportional hazard models were employed to estimate all-cause mortality and/or myocardial infarction (MI). Four-year death and death or MI rates were 1.9% and 3.3%.

Results

Of the 4,380 patients with no luminal stenosis, 86% had CAC scores of <10 while those with a luminal stenosis had more prevalent and extensive CAC with 31.9% having a CAC score of ≥100. Among patients with no luminal stenosis, CAC was not predictive of all-cause mortality (P = .44). However, among patients with a luminal stenosis, 4-year mortality rates ranged from 0.8% to 9.8% for CAC scores of 0 to ≥400 (P < .0001). The mortality hazard was 6.0 (P = .004) and 13.3 (P < .0001) for patients with a CAC score of 100-399 and ≥400. In patients with a luminal stenosis, CAC remained independently predictive in all-cause mortality (P < .0001) and death or MI (P < .0001) in multivariable models containing CAD risk factors and presenting symptoms.

Conclusions

CAC allows for the identification of those at an increased hazard for death or MI in symptomatic patients with nonobstructive disease. From the CONFIRM registry, the extent of CAC was an independent estimator of long-term prognosis among symptomatic patients with luminal stenosis and may further define risk and guide preventive strategies in patients with nonobstructive CAD.     

Mortality impact of low CAC density predominantly occurs in early atherosclerosis: explainable ML in the CAC consortium

BackgroundMachine learning (ML) models of risk prediction with coronary artery calcium (CAC) and CAC characteristics exhibit high performance, but are not inherently interpretable.ObjectivesTo determine the direction and magnitude of impact of CAC characteristics on 10-year all-cause mortality (ACM) with explainable ML.MethodsWe analyzed asymptomatic subjects in the CAC consortium. We trained ML models on 80% and tested on 20% of the data with XGBoost, using clinical characteristics ?+ ?CAC (ML 1) and additional CAC characteristics of CAC density and number of calcified vessels (ML 2). We applied SHAP, an explainable ML tool, to explore the relationship of CAC and CAC characteristics with 10-year all-cause and CV mortality.Results2376 deaths occurred among 63,215 patients [68% male, median age 54 (IQR 47–61), CAC 3 (IQR 0–94.3)]. ML2 was similar to ML1 to predict all-cause mortality (Area Under the Curve (AUC) 0.819 vs 0.821, p ?= ?0.23), but superior for CV mortality (0.847 vs 0.845, p ?= ?0.03).Low CAC density increased mortality impact, particularly ≤0.75. Very low CAC density ≤0.75 was present in only 4.3% of the patients with measurable density, and 75% occurred in CAC1-100. The number of diseased vessels did not increase mortality overall when simultaneously accounting for CAC and CAC density.ConclusionCAC density contributes to mortality risk primarily when it is very low ≤0.75, which is primarily observed in CAC 1–100. CAC and CAC density are more important for mortality prediction than the number of diseased vessels, and improve prediction of CV but not all-cause mortality. Explainable ML techniques are useful to describe granular relationships in otherwise opaque prediction models.     

Prevalence of silent myocardial ischemia in asymptomatic individuals with subclinical atherosclerosis detected by electron beam tomography

BACKGROUND: Electron beam tomography coronary calcium imaging is an evolving technique for the early detection of coronary atherosclerosis, and recent studies have established its prognostic value in asymptomatic individuals. The relationship of coronary artery calcium scores (CAC) to obstructive coronary artery disease (CAD) has been poorly studied but is clinically relevant because it determines which individuals are likely to benefit from revascularization procedures. Hence, we prospectively evaluated the prevalence of myocardial ischemia in asymptomatic patients with cardiovascular risk factors and subclinical atherosclerosis. METHODS AND RESULTS: We studied 864 asymptomatic patients with no previous CAD but with cardiovascular risk factors, referred for electron beam tomography coronary calcium imaging to our institution over an 18-month period. From this group, 220 consecutive patients (85% men; mean age, 61 +/- 9 years; age range, 31-84 years) with moderate to severe atherosclerotic disease (coronary calcium score > or =100 Agatston units) were prospectively evaluated by technetium 99m sestamibi single photon emission computed tomography (SPECT). Patients were followed up (mean follow-up, 14 months) and data regarding their subsequent clinical management recorded. Of the 220 patients, 119 had moderate atherosclerosis (CAC score of 100-400 Agatston units) and 101 had severe atherosclerosis (CAC score > or =400 Agatston units). Abnormal SPECT findings were seen in 18% of patients with moderate atherosclerosis (n = 21) and 45% of patients with severe atherosclerosis (n = 45). Increasing severity of atherosclerosis was related to increasing ischemic burden (summed difference score = 1 +/- 0.2 for CAC score of 100-400 Agatston units and 3.2 +/- 0.5 for CAC score > or =400 Agatston units). In a multivariate linear regression model incorporating risk factors, CAC was the only predictor of silent ischemia. CONCLUSION: In comparison to previously published data, we detected a higher prevalence of silent ischemia even in patients with moderate coronary atherosclerosis (18%). This may reflect the differing risk factor profile of our patient population. When coronary calcium screening is used to preselect asymptomatic patients with cardiovascular risk factors for myocardial perfusion imaging, the optimum coronary calcium score threshold will depend on the population prevalence of risk factors and asymptomatic obstructive CAD.     

Are risk factors necessary for pretest probability assessment of coronary artery disease? A patient similarity network analysis of the PROMISE trial

BackgroundPretest probability (PTP) calculators utilize epidemiological-level findings to provide patient-level risk assessment of obstructive coronary artery disease (CAD). However, their limited accuracies question whether dissimilarities in risk factors necessarily result in differences in CAD. Using patient similarity network (PSN) analyses, we wished to assess the accuracy of risk factors and imaging markers to identify ≥50% luminal narrowing on coronary CT angiography (CCTA) in stable chest-pain patients.MethodsWe created four PSNs representing: patient characteristics, risk factors, non-coronary imaging markers and calcium score. We used spectral clustering to group individuals with similar risk profiles. We compared PSNs to a contemporary PTP score incorporating calcium score and risk factors to identify ≥50% luminal narrowing on CCTA in the CT-arm of the PROMISE trial. We also conducted subanalyses in different age and sex groups.ResultsIn 3556 individuals, the calcium score PSN significantly outperformed patient characteristic, risk factor, and non-coronary imaging marker PSNs (AUC: 0.81 vs. 0.57, 0.55, 0.54; respectively, p ?< ?0.001 for all). The calcium score PSN significantly outperformed the contemporary PTP score (AUC: 0.81 vs. 0.78, p ?< ?0.001), and using 0, 1–100 and ?> ?100 cut-offs provided comparable results (AUC: 0.81 vs. 0.81, p ?= ?0.06). Similar results were found in all subanalyses.ConclusionCalcium score on its own provides better individualized obstructive CAD prediction than contemporary PTP scores incorporating calcium score and risk factors. Risk factors may not be able to improve the diagnostic accuracy of calcium score to predict ≥50% luminal narrowing on CCTA.     

Assessment of cardiovascular risk status at CT colonography

PURPOSE: To retrospectively determine whether calcium scores of the abdominal aorta obtained during computed tomographic (CT) colonography relate to Framingham risk factors and clinical cardiac events. MATERIALS AND METHODS: The institutional review board approved the current HIPAA-compliant retrospective study and waived informed consent. Between 1995 and 1998, 480 patients underwent CT colonography; 467 patients were available for assessment. Calcium scores with a threshold attenuation value of 130 HU or greater were recorded for abdominal aorta (suprarenal, infrarenal, and aortic bifurcation regions and total). Patient histories were abstracted for established cardiac risk factors and subsequent cardiac events. Associations between calcium measurements and binary risk factors were assessed with Wilcoxon rank sum test; those with continuous risk factors, with Spearman rank correlation coefficient; and those with combined end points, with Cox proportional hazards model. RESULTS: Follow-up data were available for 467 patients with median age of 65 years (range, 34-83 years); 59% (275 of 467) were men. Nine patients had cardiac events subsequent to CT colonography. Results of proportional hazards regression analysis revealed a significant association between myocardial infarction or cardiac event-related death and calcium scores of the aortic bifurcation that exceeded 895, the value for the 75th percentile for this calcium variable (P < .01). Associations with established cardiac risk factors for all four calcium scores were significant (P < .05). Spearman rank correlation coefficients for associations between total calcium score and patient characteristics of age, number of pack-years of smoking, and systolic blood pressure were 0.51, 0.43, and 0.29, respectively (P < .001 for all). CONCLUSION: Aortic calcification scores at CT colonography are significantly associated with established cardiac risk factors and cardiac-related events. This screening information can be obtained without additional scanning or risk to the patient.     

Coronary calcium score as gatekeeper for 64-slice computed tomography coronary angiography in patients with chest pain: per-segment and per-patient analysis

We sought to investigate the performance of 64-slice CT in symptomatic patients with different coronary calcium scores. Two hundred patients undergoing 64-slice CT coronary angiography for suspected coronary artery disease were enrolled into five groups based on Agatston calcium score using the Mayo Clinic risk stratification: group 1: score 0, group 2: score 1–10, group 3: score 11–100, group 4: score 101–400, and group 5: score > 401. Diagnostic accuracy for the detection of significant (≥50% lumen reduction) coronary artery stenosis was assessed on a per-segment and per-patient base using quantitative coronary angiography as the gold standard. For groups 1 through 5, sensitivity was 97, 96, 91, 90, 92%, and specificity was 99, 98, 96, 88, 90%, respectively, on a per-segment basis. On a per-patient basis, the best diagnostic performance was obtained in group 1 (sensitivity 100% and specificity 100%) and group 5 (sensitivity 95% and specificity 100%). Progressively higher coronary calcium levels affect diagnostic accuracy of CT coronary angiography, decreasing sensitivity and specificity on a per-segment base. On a per-patient base, the best results in terms of diagnostic accuracy were obtained in the populations with very low and very high cardiovascular risk. Authors have no financial conflict of interest. Neither this paper nor any of its content has not been submitted to other journals.