Diagnostic and prognostic value of absence of coronary artery calcification

Normal vascular function as a prerequisite for the absence of coronary calcification in patients free of cardiovascular disease and diabetes

BACKGROUND

The absence of coronary artery calcium (CAC) is a marker of very low cardiovascular risk. Endothelial cells may have an effect on the initiation and propagation of arterial calcification. We aimed to identify the relationship between the absence of CAC and endothelial function in individuals without cardiovascular disease and diabetes.

METHODS AND RESULTS

CAC was assessed using electron-beam computed tomography and the calcium score was then computed. Endothelial function was measured by assessing reactive hyperemia-induced vasodilation and expressed by the reactive hyperemia index (RHI). Of 82 patients, 39 had non-detectable calcium (CAC score=0) and 43 had a CAC score >0. In the CAC score=0 group, the prevalence of normal endothelial function was 84.6%, compared to 48.8% in the CAC score >0 group, P=0.001. The absence of CAC was highly correlated with normal endothelial function (γ=0.704, P<0.001). On average, endothelial function was significantly better in the CAC score=0 group than in the CAC score >0 group (RHI 2.2±0.6 vs. 1.8±0.5, P=0.002). In a multivariate logistic regression model, only normal endothelial function (odds ratio [OR] 5.03, 95% confidence interval [CI] 1.55-16.27, P=0.007) and age (years) (OR 0.91, 95% CI 0.86-0.96, P=0.002) were independently associated with the absence of CAC.

CONCLUSIONS

Normal functional status of the vasculature may be important for the prevention of coronary calcification and may partly account for the low cardiovascular risk of absent CAC.

Incremental prognostic value of different components of coronary atherosclerotic plaque at cardiac CT angiography beyond coronary calcification in patients with acute chest pain

PURPOSE

To systematically evaluate the incremental predictive value of cardiac computed tomographic (CT) angiography beyond the assessment of coronary artery calcium (CAC) in patients who present with acute chest pain but without evidence of acute coronary syndrome (ACS).

MATERIALS AND METHODS

The human research committee approved this study and waived the need for individual written informed consent. The study was HIPAA compliant. A total of 458 patients (36% male; mean age, 55 years ± 11) with acute chest pain at low to intermediate risk for coronary artery disease underwent coronary calcification assessment with cardiac CT angiography. All patients who did not experience ACS at index hospitalization were followed for instances of a major adverse cardiac event (MACE), such as a myocardial infarct, revascularization, cardiac death, or angina requiring hospitalization. CAC score and cardiac CT angiography were used to derive the presence and extent of atherosclerotic plaque (calcified, noncalcified, or mixed), and obstructive lesions (>50% luminal narrowing) were related to outcomes by using univariate and adjusted Cox proportional hazards models.

RESULTS

Of the 458 patients, 70 (15%) experienced MACE (median follow-up, 13 months). Patients with no plaque at cardiac CT angiography remained free of events during the follow-up period, while 11 (5%) of 215 patients with no CAC had MACE. The extent of plaque was the strongest predictor of MACE independent of traditional risk factors (hazard ratio [HR], 151.77 for four or more segments containing plaque as compared with those containing no plaque; P < .001). Patients with mixed plaque were more likely to experience MACE (HR, 86.96; P = .002) than those with exclusively noncalcified plaque (HR, 58.06; P = .005) or exclusively calcified plaque (HR, 32.94; P = .02).

CONCLUSION

The strong prognostic value of cardiac CT angiography is incremental to its known diagnostic value in patients with acute chest pain without ACS and is independent of traditional risk factors and CAC.

Coronary artery calcium findings in asymptomatic subjects with family history of premature coronary artery disease

Background

To evaluate the frequency of positive coronary arteries calcium (CAC) scores in a unique population of asymptomatic first degree relatives (FDRs) of patients with angiographically confirmed early onset of coronary artery disease (CAD) and to assess their association with carotid ultrasound findings and other cardiovascular risk factors.

Method and results

We scanned, using 64-slice multi-detector computed tomography, 57 asymptomatic FDRs (47 ± 9 years old; 44% male, 56% female), out of the 111 FDRs previously phenotyped for cardiovascular (CV) risk factors. The controls were 616 individuals (57 ± 10 years old; 76% male, 24% female) with no family history of cardiovascular disease, chest pain or diabetes selected out of the 3500 subjects scanned between 2002 and 2007. FDRs had higher risk of abnormal CAC scores compared to controls; odds ratio (OR) for the 75^th percentile was 1.96 (95% CI 1.04 – 3.67, p < 0.05).

Conclusion

The frequency of abnormal CAC scores is two-fold higher in asymptomatic FDRs than in controls. CAC scan provides additional information on CV risk assessment in asymptomatic FDRs, particularly for those in the intermediate risk category.

Clinical trial registration

NCT00387595

Interplay of coronary artery calcification and traditional risk factors for the prediction of all-cause mortality in asymptomatic individuals

BACKGROUND

Current guidelines recommend the use of coronary artery calcium (CAC) scoring for intermediate-risk patients; however, the potential role of CAC among individuals who have no risk factors (RFs) is less established. We sought to examine the relationship between the presence and burden of traditional RFs and CAC for the prediction of all-cause mortality.

METHODS AND RESULTS

The study cohort consisted of 44,052 consecutive asymptomatic individuals free of known coronary heart disease referred for computed tomography for the assessment of CAC. The following RFs were considered: (1) current cigarette smoking, (2) dyslipidemia, (3) diabetes mellitus, (4) hypertension, and (5) family history of coronary heart disease. Patients were followed for a mean of 5.6 ± 2.6 years for the primary end point of all-cause mortality. Among individuals who had no RF, Cox proportional model adjusted for age and sex identified that increasing CAC scores were associated with 3.00- to 13.38-fold higher mortality risk. The lowest survival rate was observed in those with no CAC and no RF, whereas those with CAC ≥ 400 and ≥3 RFs had the highest all-cause fatality rate. Notably, individuals with no RF and CAC ≥ 400 had a substantially higher mortality rate compared with individuals with ≥3 RFs in the absence of CAC (16.89 versus 2.72 per 1000 person-years).

CONCLUSIONS

By highlighting that individuals without RFs but elevated CAC have a substantially higher event rates than those who have multiple RFs but no CAC, these findings challenge the exclusive use of traditional risk assessment algorithms for guiding the intensity of primary prevention therapies.

Value of coronary computed tomography as a prognostic tool

Coronary computed tomography angiography (CCTA) has become an important part of our armamentarium for noninvasive diagnosis of coronary artery disease (CAD). Emerging technologies have produced lower radiation dose, improved spatial and temporal resolution, as well as information about coronary physiology. Although the prognostic role of coronary artery calcium scoring is known, similar evidence for CCTA has only recently emerged. Initial, small studies in various patient populations have indicated that CCTA-identified CAD may have a prognostic value. These findings were confirmed in a recent analysis of the international, prospective Coronary CT Angiography Evaluation For Clinical Outcomes: An International Multicenter (CONFIRM) registry. An incremental increase in mortality was found with a worse severity of CAD on a per-patient, per-vessel, and per-segment basis. In addition, age-, sex-, and ethnicity-based differences in mortality were also found. Whether changing our management algorithms based on these findings will affect outcomes is unclear. Large prospective studies utilizing targeted management strategies for obstructive and nonobstructive CAD are required to incorporate these recent findings into our daily practice.

Coronary CT and the coronary calcium score, the future of ED risk stratification?

Accurate and efficient evaluation of acute chest pain remains clinically challenging because traditional diagnostic modalities have many limitations. Recent improvement in non-invasive imaging technologies could potentially improve both diagnostic efficiency and clinical outcomes of patients with acute chest pain while reducing unnecessary hospitalizations. However, there is still controversy regarding much of the evidence for these technologies. This article reviews the role of coronary artery calcium score and the coronary computed tomography in the assessment of individual coronary risk and their usefulness in the emergency department in facilitating appropriate disposition decisions. The evidence base and clinical applications for both techniques are also described, together with cost- effectiveness and radiation exposure considerations.

Improvement of cardiovascular risk prediction using coronary imaging: subclinical atherosclerosis: the memory of lifetime risk factor exposure

Deaths from diseases of the heart are decreasing. Cardiovascular diseases (CVD) will be the main cause of morbidity and mortality in 2015 according to a WHO report. The main problem is related to the long-time delay between the start of the development of atherosclerosis in young adults and the manifestation many decades later. Despite a recent decline in a CVD mortality rate in men and women, the main problem is related to the acute manifestation as the acute coronary syndrome, which leads 30-50% of subjects to sudden and fatal outcomes. In addition, about 20% of first and recurrent acute myocardial infarctions are silent. The lifetime risk of coronary artery disease after 40 years is 49% for men and 32% for women. That means, we are confronted with a major health care problem. This is even more obvious, when the rate of coronary heart disease deaths out of the hospital are taken into account which amount to 70% in 2007. These data are confirmed for Europe despite a strong decline of hospital deaths. Another problem is related to the fact that the number of sudden cardiac death amounts to >300 000 in the general US population. It is about 10 times higher than in those patients who are defined as prone to sudden death due to low ejection fraction, ventricular arrhythmias, and acute myocardial infarction. For cardiologists, this general topic becomes even more obvious, because even well-known cardiologists experienced early (≤65 years) sudden cardiac deaths such as RW Campbell, JM Isner, PA Poole-Wilson, H Drexler, and recently the paediatric cardiologist from Hannover, A Wessels. These events underline again what has been emphasized 15 years ago by the MONICA study that two-thirds of patients die outside the hospital and that we have to concentrate on primary and secondary prevention, also in memory of these colleagues. This review will demonstrate the potential value of coronary artery calcification screening which can be used as a sign of subclinical coronary arteriosclerosis for improved risk prediction, the first step to prevention. Subclinical atherosclerosis represents the vessel memory of risk factor exposure.

Coronary artery calcification by computed tomography in epidemiologic research and cardiovascular disease prevention

Both American and European guidelines recommend coronary artery calcification (CAC) as a tool for screening asymptomatic individuals at intermediate risk for coronary heart disease (CHD). These recommendations are based on epidemiologic studies mostly in the United States. We review (1) the use of CAC in primary prevention of CHD in the United States, (2) epidemiologic studies of CAC in asymptomatic adults outside of the United States, and (3) international epidemiologic studies of CAC. This review will not consider clinical studies of CAC among patients or symptomatic individuals. US studies have shown that CAC is a strong independent predictor of CHD in both sexes among middle-aged and old age groups, various ethnic groups, and individuals with and without diabetes and that CAC plays an important role in reclassifying individuals from intermediate to high risk. Studies in Europe support these conclusions. The Electron-Beam Tomography, Risk Factor Assessment Among Japanese and US Men in the Post-World-War-II birth cohort (ERA JUMP) Study is the first international study to compare subclinical atherosclerosis, including CAC among Japanese, Japanese Americans, Koreans, and whites. It showed that as compared with whites, Japanese had lower levels of atherosclerosis, whereas Japanese Americans had similar or higher levels. CAC is being increasingly used as a screening tool for asymptomatic individuals in Europe and the United States. CAC is a powerful research tool, because it enables us to describe differences in atherosclerotic burden across populations. Such research could identify factors responsible for differences among populations, which may improve CHD prevention.

Prevalence of angiographically defined obstructive coronary artery disease in asymptomatic patients with type 2 diabetes according to the coronary calcium score

OBJECTIVE

The aim of this study was to determine whether the absence of coronary artery calcium (CAC) can safely exclude obstructive coronary artery disease (CAD) in asymptomatic patients with type 2 diabetes.

METHODS

We enrolled 478 consecutive asymptomatic patients with type 2 diabetes who visited the diabetes clinic of the Asan Medical Center between October 1, 2009 and December 31, 2010. All patients underwent 64-slice dual-source computed tomography (DSCT) for CAC scoring as well as computed tomography angiography (CTA). Patients with at least one significant coronary stenosis with >50% luminal narrowing were classified as having obstructive CAD. The findings were confirmed using conventional coronary angiography (CAG).

RESULTS

Among the 478 patients, 157 (33%) had a CAC score of 0 (CAC=0). Of these, 17 (11%) had obstructive CAD confirmed on CAG. The presence of CAC had a negative predictive value for obstructive CAD on CAG of 89% and a sensitivity of 88%, a specificity of 42% and a positive predictive value of 38%. A multivariate logistic regression analysis showed that current smoking habits were significantly associated with the presence of obstructive CAD in patients with CAC=0 after adjusting for traditional cardiovascular risk factors (odds ratio 4.87, 95% confidence interval 1.65-14.42, p=0.004).

CONCLUSION

Our findings suggest that CAC=0 on 64-slice DSCT cannot safely exclude obstructive CAD on CAG in asymptomatic patients with type 2 diabetes, particularly in current smokers. CTA should be combined with CAC scoring in screening for CAD in asymptomatic patients with type 2 diabetes.

Imaging for prevention

Cardiovascular disease deaths have declined considerably, with more than 35% reductions during the past two decades, yet a sizable detection gap remains. Cardiovascular disease remains the leading cause of morbidity and mortality in the United States and across the world, including in developing and developed nations. Recent statistics reveal that approximately 840,000 deaths were attributed to cardiovascular disease, approximately 300,000 more deaths than reported for cancer; three-quarters were reported in previously asymptomatic individuals, raising the question as to whether screening for cardiovascular disease is warranted in detecting potentially high-risk patients.

Significance of noncalcified coronary plaque in asymptomatic subjects with low coronary artery calcium score: assessment with coronary computed tomography angiography

We aimed to investigate the prevalence and severity of noncalcified coronary plaques (NCP) using coronary CT angiography (CCTA) and analyze predictors of significant coronary stenosis by NCP in asymptomatic subjects with low coronary artery calcium score (CACS). The institutional review board approved this retrospective study and all patients gave written, informed consent. The presence of plaque, severity of stenosis, plaque characteristics, and CACS were assessed in 7,515 asymptomatic subjects. We evaluated the prevalence and severity of NCP in subjects having low CACS (707 subjects; men with CACS from 1 to 50 and women from 1 to 10) in comparison to those having 0 CACS (6,040 subjects) as the reference standard. Conventional risk factors were assessed for predictors of NCP and significant stenosis by NCP. We also investigated the cardiac events of the patients through medical records. Compared to subjects with 0 CACS, those with low CACS showed higher prevalence of NCP (6.9% vs. 31.5%, P < 0.001) and significant stenosis caused by NCP (0.8% vs. 7.5%, P < 0.001). In the low CACS group, independent predictors for significant NCP included diabetes mellitus (DM), hypertension, and elevated low-density lipoprotein (LDL)-cholesterol (all P < 0.05). However, 47.2% of subjects with significant NCP were classified into the low to intermediate risk according to Framingham Risk Score. At the median follow up of 42 months (range: 3-60 months), cardiac events were significantly higher in the low CACS group compared to the 0 CACS group (2.6% vs. 0.27%, P < 0.001). In asymptomatic subjects having low CACS, the prevalence and severity of NCP were higher as compared to subjects having zero CACS and predictors of significant stenosis by NCP were DM, hypertension and LDL-Cholesterol. Therefore, CCTA may be useful for risk stratification of coronary artery disease as added value over CACS in selected populations with low CACS who have predictors of significant NCP.

Prevalence and severity of coronary artery disease and adverse events among symptomatic patients with coronary artery calcification scores of zero undergoing coronary computed tomography angiography: results from the CONFIRM (Coronary CT Angiography Evaluation for Clinical Outcomes: An International Multicenter) registry

OBJECTIVES

The purpose of this study was to describe the prevalence and severity of coronary artery disease (CAD) in relation to prognosis in symptomatic patients without coronary artery calcification (CAC) undergoing coronary computed tomography angiography (CCTA).

BACKGROUND

The frequency and clinical relevance of CAD in patients without CAC are unclear.

METHODS

We identified 10,037 symptomatic patients without CAD who underwent concomitant CCTA and CAC scoring. CAD was assessed as <50%, ≥50%, and ≥70% stenosis. All-cause mortality and the composite endpoint of mortality, myocardial infarction, or late coronary revascularization (≥90 days after CCTA) were assessed.

RESULTS

Mean age was 57 years, 56% were men, and 51% had a CAC score of 0. Among patients with a CAC score of 0, 84% had no CAD, 13% had nonobstructive stenosis, and 3.5% had ≥50% stenosis (1.4% had ≥70% stenosis) on CCTA. A CAC score >0 had a sensitivity, specificity, and negative and positive predictive values for stenosis ≥50% of 89%, 59%, 96%, and 29%, respectively. During a median of 2.1 years, there was no difference in mortality among patients with a CAC score of 0 irrespective of obstructive CAD. Among 8,907 patients with follow-up for the composite endpoint, 3.9% with a CAC score of 0 and ≥50% stenosis experienced an event (hazard ratio: 5.7; 95% confidence interval: 2.5 to 13.1; p < 0.001) compared with 0.8% of patients with a CAC score of 0 and no obstructive CAD. Receiver-operator characteristic curve analysis demonstrated that the CAC score did not add incremental prognostic information compared with CAD extent on CCTA for the composite endpoint (CCTA area under the curve = 0.825; CAC + CCTA area under the curve = 0.826; p = 0.84).

CONCLUSIONS

In symptomatic patients with a CAC score of 0, obstructive CAD is possible and is associated with increased cardiovascular events. CAC scoring did not add incremental prognostic information to CCTA.

Prognostic effect size of cardiovascular biomarkers in datasets from observational studies versus randomised trials: meta-epidemiology study

OBJECTIVE

To compare the reported effect sizes of cardiovascular biomarkers in datasets from observational studies with those in datasets from randomised controlled trials.

DESIGN

Review of meta-analyses.

STUDY SELECTION

Meta-analyses of emerging cardiovascular biomarkers (not part of the Framingham risk score) that included datasets from at least one observational study and at least one randomised controlled trial were identified through Medline (last update, January 2011).

DATA EXTRACTION

Study-specific risk ratios were extracted from all identified meta-analyses and synthesised with random effects for (a) all studies, and (b) separately for observational and for randomised controlled trial populations for comparison.

RESULTS

31 eligible meta-analyses were identified. For seven major biomarkers (C reactive protein, non-HDL cholesterol, lipoprotein(a), post-load glucose, fibrinogen, B-type natriuretic peptide, and troponins), the prognostic effect was significantly stronger in datasets from observational studies than in datasets from randomised controlled trials. For five of the biomarkers the effect was less than half as strong in the randomised controlled trial datasets. Across all 31 meta-analyses, on average datasets from observational studies suggested larger prognostic effects than those from randomised controlled trials; from a random effects meta-analysis, the estimated average difference in the effect size was 24% (95% CI 7% to 40%) of the overall biomarker effect.

CONCLUSIONS

Cardiovascular biomarkers often have less promising results in the evidence derived from randomised controlled trials than from observational studies.

Prevalence and predictors of atherosclerosis in symptomatic patients with zero calcium score

RATIONALE AND OBJECTIVES

Absence of coronary artery calcium (CAC) in symptomatic patients is associated with a very low risk of adverse cardiovascular events. However, patients with zero CAC may have noncalcified plaques (NCP). In this analysis, we sought to determine the prevalence and predictors of NCP in symptomatic patients with zero CAC.

MATERIALS AND METHODS

Coronary computed tomography angiography (CCTA) was performed in 333 consecutive symptomatic patients (mean age 50 ± 12, 65% males) with zero CAC and no known coronary artery disease (CAD). Pretest likelihood was estimated by Framingham risk score (FRS). Independent predictors of NCP were identified using multivariate logistic regression.

RESULTS

NCP was detected in 55 patients (17%) on CCTA, of which 6 patients (1.8%) had significant stenosis. In univariate analysis, patients with NCP were older (55 ± 7 vs. 50 ± 10 years, P = .009), with higher prevalence of hypertension (80% vs. 63%, P = .013). Using multivariate logistic regression, the independent predictors of NCP in this cohort were intermediate to high FRS (OR 2.3, 95%CI 1.3-4.1, P = .007), whereas baseline statin therapy was associated with lower prevalence of NCP (OR 0.38, 95%CI 0.17-0.89, P = .02).

CONCLUSION

Our analysis shows that nearly one in five patients with zero calcium score has NCP and one in three patients with zero calcium score and intermediate to high FRS have evidence of NCP on CCTA. The prognostic value of NCP in these patients needs further evaluation.

Noncalcified plaque: relationship between results of multislice computed tomography, risk factors, and late clinical outcome

BACKGROUND

Contrast-enhanced multislice computed tomographic angiography (MSCTA) detects noncalcified plaque (NCP) in coronary arteries and associated coronary stenoses. However, the clinical relevance of NCP is poorly defined.

OBJECTIVES

Our goal was to examine the relationship NCP, risk factors (RFs), and clinical follow-up in unselected outpatients undergoing MSCTA.

METHODS

Five hundred six patients undergoing contrast MSCTA were evaluated for NCP (intraluminal density 25 < Hounsfield units < 130). One hundred twenty-four patients (24.5%) had calcium scores (CAC) of zero. Of these, 111 patients were examined for RFs and followed clinically for a mean of 34 months.

RESULTS

Of 124 patients with zero CAC, 111 (89.5%) included 52 (46.8%) with no NCP, 40 (36.0%) with NCP, and mild luminal stenosis, 14 (12.6%) and 5 (4.5%) with NCP causing significant and severe stenosis, respectively. Patients in each group were similar in age but differed significantly in number of RFs. Current or former smokers, hypertensive, and obese patients had more NCP and associated stenosis. At a mean of 34 months, there were no events in the no NCP group, 2/54 (3.7%) events in the NCP without severe stenosis group (one sudden cardiac death and one ventricular tachycardia), and 2/5 (40.0%) patients had revascularization in the NCP with severe stenosis group.

CONCLUSIONS

(1) In patients with zero CAC, presence of NCP on MSCTA was associated with more RFs, especially smoking, obesity, and hypertension. (2) NCP can result in severe coronary stenosis. (3) NCP detected by MSCTA in patients with zero CAC may identify patients with late cardiac events.

Comparison of Framingham, PROCAM, SCORE, and Diamond Forrester to predict coronary atherosclerosis and cardiovascular events

BACKGROUND

Cardiologists are often confronted with patients presenting with chest pain, in whom clinical risk profiling is required. We studied four frequently used risk scores in their ability to predict for coronary artery disease (CAD) and major adverse cardiovascular events in patients presenting with stable chest pain at the cardiology outpatient clinic.

METHODS AND RESULTS

We enrolled 1,296 stable chest pain patients, who underwent cardiac computed tomographic angiography (CCTA) to assess CAD (any, significant: stenosis ≥50%). Framingham (FRS), PROCAM, SCORE risk score, and Diamond Forrester pre-test probability were calculated. All patients were followed up for a mean 19 ± 9 months for all cardiovascular events (mortality, acute coronary syndrome, revascularization >90 days after CCTA). In ROC-analysis for prediction of significant CAD, the areas under the curve for FRS; 0.68 (95% confidence interval: 0.64-0.72) and for SCORE; 0.69 (95% confidence interval: 0.65-0.72) were significantly higher than for PROCAM; 0.64 (95% confidence interval: 0.61-0.68; P ≤ .001), as well as marginally higher than for Diamond Forrester; 0.65 (95% confidence interval: 0.61-0.68; P ≤ .05). Low FRS category showed the lowest number of patients with significant CAD, compared to patients with low risk using PROCAM, SCORE or Diamond Forrester (P < .001). Also, low FRS category showed less events (compared to PROCAM and SCORE; P < .001, for Diamond Forrester; P = .14).

CONCLUSION

Our data show that in a stable chest pain population, the ability of FRS and SCORE to predict for CAD was similar and better compared to PROCAM and Diamond Forrester. The number of low risk patients showing significant CAD or events was lower using FRS. Consequently, risk categorization using FRS seems to be safest to stratify stable chest pain patients prior to CCTA.

First-line evaluation of coronary artery disease with coronary calcium scanning or exercise electrocardiography

BACKGROUND

Although conventional (CAG) and computed tomography angiography (CTA) are reliable diagnostic modalities for exclusion of obstructive coronary artery disease (CAD), they are costly and with considerable exposure to radiation and contrast media. We compared the accuracy of coronary calcium scanning (CCS) and exercise electrocardiography (X-ECG) as less expensive and non-invasive means to rule out obstructive CAD.

METHODS

In a rapid-access chest pain clinic, 791 consecutive patients with stable chest pain were planned to undergo X-ECG and dual-source CTA with CCS. According to the Duke pre-test probability of CAD patients were classified as low (<30%), intermediate (30-70%) or high risk (>70%). Angiographic obstructive CAD (>50% stenosis by CAG or CTA) was found in 210/791 (27%) patients, CAG overruling any CTA results.

RESULTS

Obstructive CAD was found in 12/281 (4%) patients with no coronary calcium and in 73/319 (23%) with a normal X-ECG (p<0.001). No coronary calcium was associated with a substantially lower likelihood ratio compared to X-ECG; 0.11, 0.13 and 0.13 vs. 0.93, 0.55 and 0.46 in the low, intermediate and high risk group. In low risk patients a negative calcium score reduced the likelihood of obstructive CAD to less than 5%, removing the need for further diagnostic work-up. CCS could be performed in 754/756 (100%) patients, while X-ECG was diagnostic in 448/756 (59%) patients (p<0.001).

CONCLUSIONS

In real-world patients with stable chest pain CCS is a reliable initial test to rule out obstructive CAD and can be performed in virtually all patients.

Associations between C-reactive protein, coronary artery calcium, and cardiovascular events: implications for the JUPITER population from MESA, a population-based cohort study

BACKGROUND

The JUPITER trial showed that some patients with LDL-cholesterol concentrations less than 3·37 mmol/L (<130 mg/dL) and high-sensitivity C-reactive protein (hsCRP) concentrations of 2 mg/L or more benefit from treatment with rosuvastatin, although absolute rates of cardiovascular events were low. In a population eligible for JUPITER, we established whether coronary artery calcium (CAC) might further stratify risk; additionally we compared hsCRP with CAC for risk prediction across the range of low and high hsCRP values.

METHODS

950 participants from the Multi-Ethnic Study of Atheroslcerosis (MESA) met all criteria for JUPITER entry. We compared coronary heart disease and cardiovascular disease event rates and multivariable-adjusted hazard ratios after stratifying by burden of CAC (scores of 0, 1-100, or >100). We calculated 5-year number needed to treat (NNT) by applying the benefit recorded in JUPITER to the event rates within each CAC strata.

FINDINGS

Median follow-up was 5·8 years (IQR 5·7-5·9). 444 (47%) patients in the MESA JUPITER population had CAC scores of 0 and, in this group, rates of coronary heart disease events were 0·8 per 1000 person-years. 74% of all coronary events were in the 239 (25%) of participants with CAC scores of more than 100 (20·2 per 1000 person-years). For coronary heart disease, the predicted 5-year NNT was 549 for CAC score 0, 94 for scores 1-100, and 24 for scores greater than 100. For cardiovascular disease, the NNT was 124, 54, and 19. In the total study population, presence of CAC was associated with a hazard ratio of 4·29 (95% CI 1·99-9·25) for coronary heart disease, and of 2·57 (1·48-4·48) for cardiovascular disease. hsCRP was not associated with either disease after multivariable adjustment.

INTERPRETATION

CAC seems to further stratify risk in patients eligible for JUPITER, and could be used to target subgroups of patients who are expected to derive the most, and the least, absolute benefit from statin treatment. Focusing of treatment on the subset of individuals with measurable atherosclerosis could allow for more appropriate allocation of resources.

FUNDING

National Institutes of Health-National Heart, Lung, and Blood Institute.

Computed tomography-coronary angiography in the detection of coronary artery disease

Computed tomography-coronary angiography (CT-CA) is a well-tolerated and reliable non-invasive imaging technique and can now be achieved at low levels of radiation exposure. CT-CA is highly valuable to exclude coronary artery disease, but due to over- and underestimation of the severity of coronary lesions, CT-CA cannot replace invasive coronary angiography. Coronary calcium scoring has an incremental independent prognostic value beyond traditional risk factor scores (Framingham, European Score) and may be useful to reclassify risk in asymptomatic individuals at intermediate risk. Appropriate indications for CT-CA are evolving, but studies are lacking to demonstrate that CT coronary imaging improves patient outcome.

Small calcified coronary atherosclerotic plaque simulation model: minimal size and attenuation detectable by 64-MDCT and MicroCT

Zero calcium score may not reflect the absence of calcifications as small calcifications could be missed. This study aimed to evaluate minimal size and minimal attenuation of coronary calcifications detectable by computed tomography (CT) and to determine the minimal spatial resolution required for detecting calcification onset. Using open source CT simulation software, CTSim^©, several 50%-stenotic coronary artery phantoms were designed with 5 μm resolution, realistic morphology and tissue-specific Hounsfield Unit (HU) values. The plaque had an attenuation resembling fibrous plaque and contained a single calcification. X-ray projections were simulated with settings resembling non-contrast-enhanced 64 multi detector-row CT (64-MDCT). Scanning and reconstruction were simulated with spatial resolution of a 64-MDCT (0.4mm) and of a MicroCT (48 μm). Starting from a single calcium granule, the calcification was simulated to grow in size and attenuation until it could be detected using clinically accepted calcium determination scheme on MicroCT and 64-MDCT images. The smallest coronary calcifications detectable at MicroCT and 64-MDCT, which had a realistic attenuation (−1,024 to 3,072 HU), were of 25 μm and 215 μm diameter, respectively. The area was overestimated 7.7 and 8.8 times, respectively. Calcifications with smaller size need to have an unrealistically high attenuation to be detectable by 64-MDCT. In conclusion, 64-MDCT is only able to detect coronary calcifications with minimal diameter of 215 μm. Consequently, early onset of calcification in coronary plaque will remain invisible when using CT and a zero calcium score can not exclude the presence of coronary calcification.

Multimodality imaging in diabetic heart disease

Diabetic heart disease is currently defined as left ventricular dysfunction that occurs independently of coronary artery disease and hypertension. Its underlying etiology is likely to be multifactorial, acting synergistically together to cause myocardial dysfunction. Multimodality cardiac imaging, such as echocardiography, nuclear, computed tomography, and magnetic resonance imaging, can provide invaluable insight into different aspects of the disease process, from imaging at the cellular level for altered myocardial metabolism to microvascular and endothelial dysfunction, autonomic neuropathy, coronary atherosclerosis, and finally, interstitial fibrosis with scar formation. Furthermore, cardiac imaging is pivotal in diagnosing diabetic heart disease. Thus, the aim of the present review is to illustrate the role of multimodality cardiac imaging in elucidating the underlying pathophysiologic mechanisms of diabetic heart disease.

Prevalence of computed tomographic angiography-verified high-risk plaques and significant luminal stenosis in patients with zero coronary calcium score

BACKGROUND

Some patients were detected with coronary artery disease even if the coronary artery calcium score was (CACS)=0. We evaluated the prevalence and predictor of significant stenosis and computed tomography (CT) based vulnerable plaque (CTVP) for patients with CACS=0.

METHODS

Subjects were 2160 patients (M/F=1110/1050, 64.7 ± 11.6 years) who underwent measurement of calcium score and CT coronary angiography. As for CACS=0 group, age, gender, coronary risk factor (family history (FH), hypertension (HT), hyperlipidemia (HL), diabetes (DM), and smoking), body mass index, history of cerebral infarction, the presence of chest symptom, and abnormal rest ECG findings were investigated as predictors for significant stenosis and CTVP by multivariate analysis using logistic regression analysis.

RESULTS

Out of 2160 patients, 1141 (52.8%, M/F=655/486, 68.4 ± 9.8 years) were of CACS>0 and 1019 (47.2%, M/F=455/564, 60.5 ± 12.0 years) were of CACS=0. In the CACS=0 group, 24 patients (2.4%) were found with significant stenosis and 47 (4.6%) with 2FPP. In 104 patients with spotty calcification (10.2%), 10 (9.6%) out of these 104 had significant stenosis and also had CTVP. Multivariate analysis using logistic regression analysis revealed significant predictor for significant stenosis to be only male (Odds ratio (OR): 3.075, 95%CI 1.166-8.109, p=0.0232) and significant predictor for CTVP to be age (OR: 1.032, 95%CI 1.001-1.063, p=0.0437) and male (OR: 2.386, 95%CI 1.193-4.775, p=0.0140).

CONCLUSIONS

The present study suggests that the presence of CTVP must be noted, when patients are male and elderly even if CACS=0 and the presence of spotty calcification increases the prevalence of significant stenosis and CTVP in patients with CACS=0.

Usefulness of the Agatston score = 0 to exclude ischemic cardiomyopathy in patients with heart failure

Quantification of coronary artery calcium has prognostic value and is commonly used in asymptomatic patients. Routine clinical use of coronary artery calcium in other populations remains uncertain. We sought to understand the potential application of the Agatston score in patients with heart failure (HF). For this purpose, 3 populations were identified: (1) patients with an Agatston score equal to 0, (2) patients with high-risk coronary artery disease (CAD) defined as 3-vessel, left main, or 2-vessel disease involving the proximal left anterior descending coronary artery, and (3) patients with HF symptoms and left ventricular (LV) ejection fraction <50%. Excluding patients with HF or LV dysfunction, 738 patients (mean age 52 ± 10 years, 43% men) had an Agatston score equal to 0. Of these, 18 (2%) had obstructive CAD (diameter stenosis ≥50%), 8 (1%) had diameter stenoses ≥70%, and none had high-risk CAD. The 74 patients with high-risk CAD without LV dysfunction had high Agatston scores (mean 895 ± 734, median 716, range 50 to 3,210). In total 153 patients with a history of HF and abnormal ejection fraction were identified. All 13 patients with ischemic cardiomyopathy had Agatston scores >0, whereas 46 of 140 patients (30.1%) with nonischemic causes had an Agatston score equal to 0. An Agatston score equal to 0 identified nonischemic causes with a specificity of 100% (confidence interval 90 to 100) and positive predictive value of 100% (confidence interval 90 to 100). Agatston score equal to 0 had incremental value to pretest probability for CAD. In conclusion, an Agatston score equal to 0 confers a very low likelihood of obstructive CAD, appears to rule out high-risk CAD, and thus may be used to rule out ischemic cardiomyopathy in patients with HF.

Diagnostic value of coronary artery calcium scoring in low-intermediate risk patients evaluated in the emergency department for acute coronary syndrome

Early and accurate triage of patients with possible ischemic chest pain remains challenging in the emergency department because current risk stratification techniques have significant cost and limited availability. The aim of this study was to determine the diagnostic value of the coronary artery calcium score (CACS) for the detection of obstructive coronary artery disease (CAD) in low- to intermediate-risk patients evaluated in the emergency department for suspected acute coronary syndromes. A total of 225 patients presenting to the emergency department with acute chest pain and Thrombolysis In Myocardial Infarction (TIMI) scores <4 who underwent non-contrast- and contrast-enhanced coronary computed tomographic angiography were included. CACS was calculated from the noncontrast scan using the Agatston method. The prevalence of obstructive CAD (defined from the contrast scan as ≥ 50% maximal reduction in luminal diameter in any segment) was 9% and increased significantly with higher scores (p <0.01 for trend). CACS of 0 were observed in 133 patients (59%), of whom only 2 (1.5%) had obstructive CAD. The diagnostic accuracy of CACS to detect obstructive CAD was good, with an area under the receiver-operating characteristic curve of 0.88 and a negative predictive value of 99% for a CACS of 0. In a multivariate model, CACS was independently associated with obstructive CAD (odds ratio 7.01, p = 0.02) and provided additional diagnostic value over traditional CAD risk factors. In conclusion, CACS appears to be an effective initial tool for risk stratification of low- to intermediate-risk patients with possible acute coronary syndromes, on the basis of its high negative predictive value and additive diagnostic value.

Prognostic value of cardiac computed tomography angiography: a systematic review and meta-analysis

OBJECTIVES

The purpose of this study was to systematically review and perform a meta-analysis of the ability of cardiac computed tomography angiography (CCTA) to predict future cardiovascular events and death.

BACKGROUND

The diagnostic accuracy of CCTA is well reported. The prognostic value of CCTA has been described in several studies, but many were underpowered. Pooling outcomes increases the power to predict rare events.

METHODS

We searched multiple databases for longitudinal studies of CCTA with at least 3 months follow-up of symptomatic patients with suspected coronary artery disease (CAD) reporting major adverse cardiovascular events (MACE), consisting of death, myocardial infarction (MI), and revascularization. Annualized event rates were pooled using a bivariate mixed-effects binomial regression model to calculate summary likelihood ratios and receiver-operating characteristic curves.

RESULTS

Eighteen studies evaluated 9,592 patients with a median follow-up of 20 months. The pooled annualized event rate for obstructive (any vessel with >50% luminal stenosis) versus normal CCTA was 8.8% versus 0.17% per year for MACE (p < 0.05) and 3.2% versus 0.15% for death or MI (p < 0.05). The pooled negative likelihood ratio for MACE after normal CCTA findings was 0.008 (95% confidence interval [CI]: 0.0004 to 0.17, p < 0.001), the positive likelihood ratio was 1.70 (95% CI: 1.42 to 2.02, p < 0.001), sensitivity was 0.99 (95% CI: 0.93 to 1.00, p < 0.001), and specificity was 0.41 (95% CI: 0.31 to 0.52, p < 0.001). Stratifying by no CAD, nonobstructive CAD (worst stenosis <50%), or obstructive CAD, there were incrementally increasing adverse events.

CONCLUSIONS

Adverse cardiovascular events among patients with normal findings on CCTA are rare. There are incrementally increasing future MACE with increasing CAD by CCTA.

The absence of coronary calcium: clinical and therapeutic implications for the clinical lipidologist

BACKGROUND

Cardiac computed tomography for coronary artery calcium scoring, a diagnostic test associated with relatively low radiation exposure, provides incremental coronary risk stratification above that provided by Framingham risk scoring in asymptomatic, intermediate-risk patients. Knowledge of the appropriate use of coronary calcium scoring enables the clinician to more appropriately match the intensity of preventive cardiovascular care to the individual's absolute risk of coronary heart disease (CHD).

METHODS

A Medline search was used for original articles pertinent to coronary artery calcium scoring from 2000 to 2010.

RESULTS

Despite the presence of coronary risk factors, up to 45% of asymptomatic, presumed intermediate-risk patients referred for coronary calcium scoring have no detectable coronary calcium, a finding associated with a 1 to 2% 10-year risk of CHD death or nonfatal myocardial infarction. Such patients could logically be given a more prolonged opportunity to respond to therapeutic lifestyle change and, if necessary, generic lipid-altering medication before more expensive treatment strategies are implemented.

CONCLUSIONS

Because coronary calcium scoring is usually a self-pay test, the test should be ordered only in those circumstances in which knowledge of the results will change coronary risk management. This review addresses these issues and attempts to place the clinical utility of this important diagnostic test in perspective for the clinician.

Coronary risk stratification, discrimination, and reclassification improvement based on quantification of subclinical coronary atherosclerosis: the Heinz Nixdorf Recall study

OBJECTIVES

The purpose of this study was to determine net reclassification improvement (NRI) and improved risk prediction based on coronary artery calcification (CAC) scoring in comparison with traditional risk factors.

BACKGROUND

CAC as a sign of subclinical coronary atherosclerosis can noninvasively be detected by CT and has been suggested to predict coronary events.

METHODS

In 4,129 subjects from the HNR (Heinz Nixdorf Recall) study (age 45 to 75 years, 53% female) without overt coronary artery disease at baseline, traditional risk factors and CAC scores were measured. Their risk was categorized into low, intermediate, and high according to the Framingham Risk Score (FRS) and National Cholesterol Education Panel Adult Treatment Panel (ATP) III guidelines, and the reclassification rate based on CAC results was calculated.

RESULTS

After 5 years of follow-up, 93 coronary deaths and nonfatal myocardial infarctions occurred (cumulative risk 2.3%; 95% confidence interval: 1.8% to 2.8%). Reclassifying intermediate (defined as 10% to 20% and 6% to 20%) risk subjects with CAC <100 to the low-risk category and with CAC ≥400 to the high-risk category yielded an NRI of 21.7% (p = 0.0002) and 30.6% (p < 0.0001) for the FRS, respectively. Integrated discrimination improvement using FRS variables and CAC was 1.52% (p < 0.0001). Adding CAC scores to the FRS and National Cholesterol Education Panel ATP III categories improved the area under the curve from 0.681 to 0.749 (p < 0.003) and from 0.653 to 0.755 (p = 0.0001), respectively.

CONCLUSIONS

CAC scoring results in a high reclassification rate in the intermediate-risk cohort, demonstrating the benefit of imaging of subclinical coronary atherosclerosis. Our study supports its application, especially in carefully selected individuals with intermediate risk.

Combining cardiac magnetic resonance and computed tomography coronary calcium scoring: added value for the assessment of morphological coronary disease?

To investigate prospectively, in patients with suspicion of coronary artery disease (CAD), the added value of coronary calcium scoring (CS) as adjunct to cardiac magnetic resonance (CMR) for the diagnosis of morphological coronary stenosis in comparison to catheter angiography (CA). Sixty consecutive patients (8 women; 64 ± 10 years) referred to CA underwent CMR (1.5 T) including perfusion and late gadolinium-enhancement imaging as well as CS with computed tomography. Diagnostic performance was evaluated for CMR and CS separately, and for both methods combined, with CA as reference standard. Best CS threshold combined with a specificity >90% to predict significant stenosis in patients without abnormalities on CMR was determined from receiver operator characteristics (ROC) analysis. Abnormal CMR results were considered to indicate significant stenosis regardless of CS; CS above threshold reclassified patients to have CAD regardless of CMR. CA identified 104/960 (11%) coronary segments with coronary artery stenosis >50% in 36/60 (60%) patients. ROC revealed an area-under-the-curve of 0.83 (95%CI: 0.68-0.99) with the best CS threshold of 495 Agatston score (sensitivity 50%). CMR depicted 128/960 (13%) myocardial segments with abnormalities in 31/60 (52%) patients. Sensitivity, specificity, negative (NPV) and positive predictive value (PPV) of CMR were 78, 88, 72 and 90%. When adding CS to CMR, sensitivity and NPV increased to 89 and 83%, while specificity and PPV slightly decreased to 83 and 89%. Accuracy of the combined approach (87%) was significantly (P < 0.05) higher than that of CMR (82%) alone. Adding CS to CMR improves the accuracy for the detection of morphological CAD.