Influence of coronary calcification on the diagnostic accuracy of 64-slice computed tomography coronary angiography: a systematic review and meta-analysis

Limits of the possible: diagnostic image quality in coronary angiography with third-generation dual-source CT

BACKGROUND

The usage of coronary CT angiography (CTA) is appropriate in patients with acute or chronic chest pain; however the diagnostic accuracy may be challenged with increased Agatston score (AS), increased heart rate, arrhythmia and severe obesity. Thus, we aim to determine the potential of the recently introduced third-generation dual-source CT (DSCT) for CTA in a 'real-life' clinical setting.

METHODS

Two hundred and sixty-eight consecutive patients (age: 67 ± 10 years; BMI: 27 ± 5 kg/m²; 61% male) undergoing clinically indicated CTA with DSCT were included in the retrospective single-center analysis. A contrast-enhanced volume dataset was acquired in sequential (SSM) (n = 151) or helical scan mode (HSM) (n = 117). Coronary segments were classified in diagnostic or non-diagnostic image quality. A subset underwent invasive angiography to determine the diagnostic accuracy of CTA.

RESULTS

SSM (96.8 ± 6%) and HSM (97.5 ± 8%) provided no significant differences in the overall diagnostic image quality. However, AS had significant influence on diagnostic image quality exclusively in SSM (B = 0.003; p = 0.0001), but not in HSM. Diagnostic image quality significantly decreased in SSM in patients with AS ≥2,000 (p = 0.03). SSM (sensitivity: 93.9%; specificity: 96.7%; PPV: 88.6%; NPV: 98.3%) and HSM (sensitivity: 97.4%; specificity: 94.3%; PPV: 86.0%; NPV: 99.0%) provided comparable diagnostic accuracy (p = n.s.). SSM yielded significantly lower radiation doses as compared to HSM (2.1 ± 2.0 vs. 5.1 ± 3.3 mSv; p = 0.0001) in age and BMI-matched cohorts.

CONCLUSION

SSM in third-generation DSCT enables significant dose savings and provides robust diagnostic image quality in patients with AS ≤2000 independent of heart rate, heart rhythm or obesity.

CT Determination of Fractional Flow Reserve in Coronary Lesions

Invasively determined fractional flow reserve (FFR) represents the gold-standard method for the functional evaluation of coronary lesions. Coronary computed tomography angiography (CCTA) provides characterization of the coronary anatomy, with important morphological information on the atherosclerotic plaques, but does not offer a hemodynamic evaluation of coronary artery lesions. CT evaluation of FFR (FFRCT) is a new noninvasive diagnostic method, which provides anatomical and functional assessment of the whole coronary tree, based on computational techniques, with no more radiation or hyperemic agent administration compared with routine CCTA. Recent studies demonstrated the safety and accuracy of FFRCT and its therapeutic use and cost benefits in real-world clinical use.

Coronary artery calcium score and coronary computed tomography angiography for patients with asymptomatic polyvascular (non-coronary) atherosclerosis

INTRODUCTION

The primary endpoint of this study was to determine the prevalence of coronary artery disease (CAD) and coronary artery calcium score (CACS) using coronary computed tomography angiography (CCTA) among patients with polyvascular atherosclerosis (PVA). Secondary endpoints were to evaluate the prevalence of cardiovascular risk factors and determine the predictors of PVA.

METHODS

The presence of atherosclerotic disease was assessed using ultrasonographic vascular examination in 515 asymptomatic patients. All patients with presence of stenosis over 50% and moderate-to-severe cardiovascular risk profile underwent CCTA to identify atherosclerotic coronary disease.

RESULTS

Among 515 participants, 143 patients had no evidence of atherosclerotic plaque. Of the 372 patients with atherosclerotic plaque, 184 patients had single-vessel disease, 111 patients had double-vessel disease and 77 patients had triple-vessel disease; among these patients, those who also presented with stenosis > 50% underwent CCTA. Coronary stenosis categories included: normal (6.4%); haemodynamically insignificant (34.6%); intermediate (28.7%); significant (26.6%); and total artery occlusion (3.7%). Based on the coronary vessel involved, the patients were categorised as having single- (41.0%), double- (42.0%) or triple- (17.0%) coronary disease. CACS was significantly higher in patients with double- or triple-vessel disease when compared to those with single-vessel disease.

CONCLUSION

Our study confirmed not only the high sensitivity of CCTA for highlighting CAD, but also its negative predictive value for excluding the presence of coronary stenosis or ischaemia. We found good correlation between PVA and CACS, and were able to confirm the risk factors for PVA.

Virtual Monochromatic Imaging in Patients with Intermediate to High Likelihood of Coronary Artery Disease: Impact of Coronary Calcification

RATIONALE AND OBJECTIVES

We sought to explore the image quality and diagnostic performance of virtual monochromatic imaging derived from dual-energy computed tomography coronary angiography (DE-CTCA) in patients with intermediate to high likelihood of coronary artery disease (CAD) and the influence of calcification.

MATERIALS AND METHODS

Consecutive symptomatic patients with suspected CAD referred for invasive coronary angiography who underwent DE-CTCA and a coronary artery calcium scoring before the invasive procedure comprised the study population.

RESULTS

Sixty-seven patients were included. Image quality was significantly lower at 45 keV reconstructions (mean Likert score 45 keV 3.57 ± 0.6, 65 keV 4.07 ± 0.5, and 85 keV 4.09 ± 0.6; P < .0001). Patients with moderate calcification showed a trend toward a significant improvement in the diagnostic performance with 65 keV vs 45 keV reconstructions (45 keV, area under the curve 0.92 [95% confidence interval 0.89-0.95] vs 65 keV, area under the curve 0.96 [95% confidence interval 0.93-0.98], P = .06). The diagnostic performance of DE-CTCA was significantly lower in segments with higher coronary artery calcium scoring compared to segments with none or mild calcification, independent of the energy level applied.

CONCLUSIONS

In patients with intermediate to high likelihood of CAD, DE-CTCA had a good diagnostic performance, although significantly lower in segments with severe calcification.

Modified Subtraction Coronary CT Angiography Method for Patients Unable to Perform Long Breath-Holds: A Preliminary Study

RATIONALE AND OBJECTIVES

Severe calcifications of the coronary arteries are still a major challenge in coronary computed tomography (CT) angiography (CCTA). Subtraction CCTA using a 320-detector row CT scanner has recently been introduced for patients with severe calcifications. However, the conventional subtraction CCTA method requires a long breath-holding time of approximately 20-40 seconds. This is a major problem in clinical practice because many patients may not be able to perform such a long breath-hold. We explored a modified subtraction CCTA method with a short breath-holding time to overcome this problem.

MATERIALS AND METHODS

This study was approved by our institutional review board, and all patients gave written informed consent. A total of 12 patients with a coronary calcium score of >400 were enrolled in this study. All patients were unable to hold their breath for more than 20 seconds. Modified subtraction CCTA was performed using the bolus-tracking method. The acquisition protocol was adjusted so that the mask scan was acquired 10 seconds after the postcontrast scan during a single breath-hold. The subtraction image was obtained by subtracting the mask image data from the postcontrast image data. The breath-holding times were recorded. Enhancement of the coronary arteries in the subtraction images was assessed. Subjective image quality was evaluated in a total of 32 segments using a 4-point scale.

RESULTS

The mean breath-holding time was 12.8 ± 0.8 seconds (range, 12-14 seconds). The average CT number in the coronary arteries was 288.6 ± 80.5 Hounsfield units (HU) in the subtraction images. Average image quality was significantly increased from 2.1 ± 0.9 with conventional CCTA to 3.1 ± 0.7 with subtraction CCTA (P < 0.001). With subtraction CCTA, the number of non-diagnostic segments was significantly reduced from 53% to 19% (P = 0.001).

CONCLUSIONS

This preliminary study has shown that our modified subtraction CCTA method allows the breath-holding time to be shortened to <15 seconds. This may substantially improve the success rate of subtraction CCTA by reducing artifacts and allowing this technique to be applied to patients who are unable to perform a long breath-hold.

Noninvasive FFR derived from coronary CT angiography in the management of coronary artery disease: technology and clinical update

After a decade of clinical use of coronary computed tomographic angiography (CCTA) to evaluate the anatomic severity of coronary artery disease, new methods of deriving functional information from CCTA have been developed. These methods utilize the anatomic information provided by CCTA in conjunction with computational fluid dynamics to calculate fractional flow reserve (FFR) values from CCTA image data sets. Computed tomography-derived FFR (CT-FFR) enables the identification of lesion-specific drop noninvasively. A three-dimensional CT-FFR modeling technique, which provides FFR values throughout the coronary tree (HeartFlow FFR_CT analysis), has been validated against measured FFR and is now approved by the US Food and Drug Administration for clinical use. This technique requires off-site supercomputer analysis. More recently, a one-dimensional computational analysis technique (Siemens cFFR), which can be performed on on-site workstations, has been developed and is currently under investigation. This article reviews CT-FFR technology and clinical evidence for its use in stable patients with suspected coronary artery disease.

Independent prognostic value of coronary artery calcium score and coronary computed tomography angiography in an outpatient cohort of low to intermediate risk chest pain patients

Background

Limited studies report on the additional prognostic value of coronary computed tomography angiography (CCTA) and the coronary artery calcium score (CACS).

Methods

For a median of 637 days, 1551 outpatients with chest pain, without known coronary artery disease (CAD) and low or intermediate pre-test probability of CAD, were followed for major adverse cardiac events (MACE), defined as death, myocardial infarction or late revascularisation. Cox proportional hazard regression was used to evaluate the independent prognostic value of CCTA and CACS.

Results

MACE occurred in 23 patients (1.5 %): death (3, 0.2 %), myocardial infarction (4, 0.3 %) and late revascularisation (16, 1.3 %). Multivariate analysis showed an independent prognostic value of CCTA (p < 0.001), CACS of 100–400 (p = 0.035) and CACS of > 400 (p = 0.021). CCTA showed obstructive CAD in 3.1 % of patients with CACS = 0. No events occurred in patients with CACS = 0 without obstructive CAD at CCTA, whereas 2/23 patients (9 %) with CACS = 0 with obstructive CAD had a MACE.

Conclusions

Our study shows that both CCTA and higher CACS categories have independent prognostic value in chest pain patients with low to intermediate pre-test probability of obstructive CAD, in which CCTA is appropriate. Furthermore a non-negligible amount of patients with CACS = 0 have obstructive CAD at CCTA. CCTA can be used in these patients to identify those at risk for MACE.

Diagnostic accuracy of coronary angiography using 64-slice computed tomography in coronary artery disease

Objectives:

To conduct a meta-analysis and investigate the diagnostic value of 64-slice computed tomography (CT) angiography for diagnosing coronary artery disease (CAD) in patients.

Methods:

A comprehensive literature search from March 2005 to August 2014 was performed on the following databases: Cochrane Library; Medline; EmBase; PubMed; and BioMed Central database. As a reference standard, studies that assessed 64-slice CT angiography in detecting coronary artery stenosis (CAS) with invasive coronary angiography were included. Coronary artery stenosis was defined as ≥50% diameter stenosis. Diagnostic value was determined by pooling sensitivity, specificity, positive likelihood ratio (PLR) and negative likelihood ratio (NLR) values at segment-level analysis. Diagnostic accuracy was undertaken using area under the curve (AUC) value and summary receiver operating characteristic (SROC) curves. Publication bias was examined by Deek’s funnel plot asymmetry test.

Results:

Eight studies were included in the analysis, enrolling a total of 579 patients (7,407 segment coronary vessels). At segment-level, pooled sensitivity value was 90% (95% confidence interval [CI]: 83-95%), specificity was 91% (95% CI: 61-98%), PLR value was 9.7 (95% CI: 1.8-53.3), and NLR value was 0.11 (95% CI: 0.05-0.22) for CAS. Optimal cut-off point of sensitivity was 90%, and specificity under the SROC curve was 91%. The AUC value was 0.94.

Conclusion:

The 64-slice CT angiography is a reliable tool for detection of CAD when using a cut-off of ≥50% diameter stenosis in elderly population.

Beyond Stenosis With Fractional Flow Reserve Via Computed Tomography and Advanced Plaque Analyses for the Diagnosis of Lesion-Specific Ischemia

In the treatment of stable coronary artery disease (CAD), the determination of stenosis severity by invasive coronary angiography (ICA) is a critical procedure, and for borderline lesions, the detection of ischemia through invasive fractional flow reserve (FFR) is the gold standard. With advances in computational fluid dynamics, FFR can now be calculated noninvasively using anatomic data from coronary computed tomographic angiography (CCTA). This technique is known as FFR_CT. The purpose of this review is to summarize the science of FFR_CT, describe its diagnostic accuracy, discuss its clinical and economic impact, and elucidate factors beyond stenosis severity that may mechanistically relate to lesion-specific ischemia. These factors include adverse atherosclerotic plaque characteristics such as positive remodelling, low-attenuation plaque, and spotty calcification, as well as aggregate plaque volume. These factors can be appreciated noninvasively by CCTA but not by ICA. The diagnostic accuracy of FFR_CT, compared with the gold standard of FFR, has been validated in 3 prospective multicentre blinded core laboratory-controlled trials, and as a result FFR_CT has been approved by the US Food and Drug Administration for clinical use. FFR_CT has also been shown in a clinical utility trial to better identify patients without obstructive CAD when compared with standard noninvasive assessment of stable CAD, thereby avoiding unnecessary angiograms. In addition, the use of FFR_CT has been shown to allow for a significant cost savings compared with traditional care. It is therefore important for cardiologists to appreciate the value of this important new methodology.

Assessment of coronary in-stent restenosis: value of subtraction coronary computed tomography angiography

In conventional coronary computed tomography angiography (CCTA), metal artifacts are frequently observed where stents are located, making it difficult to evaluate in-stent restenosis. This study was conducted to investigate whether subtraction CCTA can improve diagnostic accuracy in the evaluation of in-stent restenosis. Subtraction CCTA was performed using 320-row CT in 398 patients with previously placed stents who were able to hold their breath for 25 s and in whom mid-diastolic prospective one-beat scanning was possible. Among these patients, 126 patients (94 men and 32 women, age 74 ± 8 years) with 370 stents who also underwent invasive coronary angiography (ICA) were selected as the subjects of this study. With ICA findings considered the gold standard, conventional CCTA was compared against subtraction CCTA to determine whether subtraction can improve diagnostic accuracy in the evaluation of in-stent restenosis. When non-assessable stents were considered to be stenotic, the diagnostic accuracy in the evaluation of in-stent restenosis was 62.7 % for conventional CCTA and 89.5 % for subtraction CCTA. When the non-assessable stents were considered to be non-stenotic the diagnostic accuracy was 90.3 % for conventional CCTA and 94.31 % for subtraction CCTA. When subtraction CCTA was used to evaluate only the 138 stents that were judged to be non-assessable by conventional CCTA, 116 of these stents were judged to be assessable, and the findings for 109 of them agreed with those obtained by ICA. Even for stents with an internal diameter of 2.5-3 mm, the lumen can be evaluated in more than 80 % of patients. Subtraction CCTA provides significantly higher diagnostic accuracy than conventional CCTA in the evaluation of in-stent restenosis.

Influence of Coronary Calcification on the Diagnostic Performance of CT Angiography Derived FFR in Coronary Artery Disease: A Substudy of the NXT Trial

OBJECTIVES

The goal of this study was to examine the diagnostic performance of noninvasive fractional flow reserve (FFR) derived from coronary computed tomography angiography (CTA) (FFRCT) in relation to coronary calcification severity.

BACKGROUND

FFRCT has shown promising results in identifying lesion-specific ischemia. The extent to which the severity of coronary calcification affects the diagnostic performance of FFRCT is not known.

METHODS

Coronary calcification was assessed by using the Agatston score (AS) in 214 patients suspected of having coronary artery disease who underwent coronary CTA, FFRCT, and FFR (FFR examination was performed in 333 vessels). The diagnostic performance of FFRCT (≤0.80) in identifying vessel-specific ischemia (FFR ≤0.80) was investigated across AS quartiles (Q1 to Q4) and for discrimination of ischemia in patients and vessels with a low-mid AS (Q1 to Q3) versus a high AS (Q4). Coronary CTA stenosis was defined as lumen reduction >50%.

RESULTS

Mean ± SD per-patient and per-vessel AS were 302 ± 468 (range 0 to 3,599) and 95 ± 172 (range 0 to 1,703), respectively. There was no statistical difference in diagnostic accuracy, sensitivity, or specificity of FFRCT across AS quartiles. Discrimination of ischemia by FFRCT was high in patients with a high AS (416 to 3,599) and a low-mid AS (0 to 415), with no difference in area under the receiver-operating characteristic curve (AUC) (0.86 [95% confidence interval (CI): 0.76 to 0.96] vs. 0.92 [95% CI: 0.88 to 0.96]) (p = 0.45). Similarly, discrimination of ischemia by FFRCT was high in vessels with a high AS (121 to 1,703) and a low-mid AS (0 to 120) (AUC: 0.91 [95% CI: 0.85 to 0.97] vs. 0.95 [95% CI: 0.91 to 0.98]; p = 0.65). Diagnostic accuracy and specificity of FFRCT were significantly higher than for stenosis assessment in each AS quartile at the per-patient (p < 0.001) and per-vessel (p < 0.05) level with similar sensitivity. In vessels with a high AS, FFRCT exhibited improved discrimination of ischemia compared with coronary CTA alone (AUC: 0.91 vs. 0.71; p = 0.004), whereas on a per-patient level, the difference did not reach statistical significance (AUC: 0.86 vs. 0.72; p = 0.09).

CONCLUSIONS

FFRCT provided high and superior diagnostic performance compared with coronary CTA interpretation alone in patients and vessels with a high AS.

Feasibility of coronary calcium and stent image subtraction using 320-detector row CT angiography

BACKGROUND

The reader confidence and diagnostic accuracy of coronary CT angiography (CCTA) can be compromised by the presence of calcified plaques and stents causing blooming artifacts. Compared to conventional invasive coronary angiography (ICA), this may cause an overestimation of stenosis severity leading to false-positive results. In a pilot study, we tested the feasibility of a new coronary calcium image subtraction algorithm in relation to reader confidence and diagnostic accuracy.

METHODS

Forty-three patients underwent clinically indicated ICA and CCTA using a 320-detector row CT. Median Agatston score was 510. Two data sets were reconstructed: a conventional CCTA (CCTAconv) and a subtracted CCTA (CCTAsub), where calcifications detected on noncontrast images were subtracted from the CCTA. Reader confidence and concordance with ICA for identification of >50% stenosis were recorded. We defined target segments on CCTAconv as motion-free coronary segments with calcification or stent and low reader confidence. The effect of CCTAsub was assessed. No approval from the ethics committee was required according to Danish law.

RESULTS

A total of 76 target segments were identified. The use of coronary calcium image subtraction improved the reader confidence in 66% of these segments. In target segments, specificity (86% vs 65%; P < .01) and positive predictive value (71% vs 51%, P = .03) were improved using CCTAsub compared to CCTAconv without loss in negative predictive value.

CONCLUSIONS

Our initial experience with coronary calcium image subtraction suggests that it is feasible and could lead to an improvement in reader confidence and diagnostic accuracy for identification of significant coronary artery disease.

Additive prognostic value of coronary artery calcium score over coronary computed tomographic angiography stenosis assessment in symptomatic patients without known coronary artery disease

The objective of this study was to examine the additive prognostic performance of coronary artery calcium score (CACS) over coronary computed tomography angiography (CCTA) stenosis assessment in symptomatic patients suspected for coronary artery disease (CAD) undergoing CCTA. A total of 805 symptomatic patients without known history of CAD who underwent coronary evaluation by multidetector cardiac CT were analyzed. Mean age of the cohort was 58 ± 13 years. A total of 44% (354 of 805) of the patients had a 0 CACS, 27% (215 of 805) had CACS 1 to 100, 14% (111 of 805) had CACS 101 to 400, and 15% (125 of 805) had CACS >400. CCTA showed normal coronary arteries in 43% (349 of 805) of patients, ≤50% stenosis in 42% (333 of 805), and >50% stenosis in 15% (123 of 805). Patients were followed for 2.3 ± 0.9 years. Major adverse cardiac event (MACE) was defined as cardiac death, nonfatal myocardial infarction, and late coronary revascularization. Overall incidence of MACE was 1.4% per year. Both CACS and CCTA stenosis were independently associated with increased MACE (p <0.05 for both). Addition of CACS into the model with clinical risk factors and CCTA stenosis significantly improved predictive performance for MACE from the model with clinical risk factors and CCTA stenosis only (global chi-square score 108 vs 70; p = 0.019). In conclusion; in symptomatic patients without known CAD, both CACS and CCTA stenosis were independently associated with increased cardiac events, and performing non-contrast-enhanced CACS evaluation in addition to contrast-enhanced CCTA improved predictive ability for future cardiac events compared to CCTA stenosis assessment alone.

Subtraction coronary CT angiography using second-generation 320-detector row CT

The purpose of this study was to explore the feasibility of subtraction coronary computed tomography angiography (CCTA) by second-generation 320-detector row CT in patients with severe coronary artery calcification using invasive coronary angiography (ICA) as the gold standard. This study was approved by the institutional board, and all subjects provided written consent. Twenty patients with calcium scores of >400 underwent conventional CCTA and subtraction CCTA followed by ICA. A total of 82 segments were evaluated for image quality using a 4-point scale and the presence of significant (>50 %) luminal stenosis by two independent readers. The average image quality was 2.3 ± 0.8 with conventional CCTA and 3.2 ± 0.6 with subtraction CCTA (P < 0.001). The percentage of segments with non-diagnostic image quality was 43.9 % on conventional CCTA versus 8.5 % on subtraction CCTA (P = 0.004). The segment-based diagnostic accuracy for detecting significant stenosis according to ICA revealed an area under the receiver operating characteristics curve of 0.824 (95 % confidence interval [CI], 0.750-0.899) for conventional CCTA and 0.936 (95 % CI 0.889-0.936) for subtraction CCTA (P = 0.001). The sensitivity, specificity, positive predictive value, and negative predictive value for conventional CCTA were 88.2, 62.5, 62.5, and 88.2 %, respectively, and for subtraction CCTA they were 94.1, 85.4, 82.1, and 95.3 %, respectively. As compared to conventional, subtraction CCTA using a second-generation 320-detector row CT showed improvement in diagnostic accuracy at segment base analysis in patients with severe calcifications.

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.

Cardiac CT: atherosclerosis to acute coronary syndrome

Coronary computed tomographic angiography (CCTA) is a robust non-invasive method to assess coronary artery disease (CAD). Qualitative and quantitative assessment of atherosclerotic coronary stenosis with CCTA has been favourably compared with invasive coronary angiography (ICA) and intravascular ultrasound (IVUS). Importantly, it allows the study of preclinical stages of atherosclerotic disease, may help improve risk stratification and monitor the progressive course of the disease. The diagnostic accuracy of CCTA in the assessment of coronary artery bypass grafts (CABG) is excellent and the constantly improving technology is making the evaluation of stents feasible. Novel techniques are being developed to assess the functional significance of coronary stenosis. The excellent negative predictive value of CCTA in ruling out disease enables early and safe discharge of patients with suspected acute coronary syndromes (ACS) in the Emergency Department (ED). In addition, CCTA is useful in predicting clinical outcomes based on the extent of coronary atherosclerosis and also based on individual plaque characteristics such as low attenuation plaque (LAP), positive remodelling and spotty calcification. In this article, we review the role of CCTA in the detection of coronary atherosclerosis in native vessels, stented vessels, calcified arteries and grafts; the assessment of plaque progression, evaluation of chest pain in the ED, assessment of functional significance of stenosis and the prognostic significance of CCTA.

Incremental prognostic utility of coronary CT angiography for asymptomatic patients based upon extent and severity of coronary artery calcium: results from the COronary CT Angiography EvaluatioN For Clinical Outcomes InteRnational Multicenter (CONFIRM) study

AIM

Prior evidence observed no predictive utility of coronary CT angiography (CCTA) over the coronary artery calcium score (CACS) and the Framingham risk score (FRS), among asymptomatic individuals. Whether the prognostic value of CCTA differs for asymptomatic patients, when stratified by CACS severity, remains unknown.

METHODS AND RESULTS

From a 12-centre, 6-country observational registry, 3217 asymptomatic individuals without known coronary artery disease (CAD) underwent CACS and CCTA. Individuals were categorized by CACS as: 0-10, 11-100, 101-400, 401-1000, >1000. For CCTA analysis, the number of obstructive vessels-as defined by the per-patient presence of a ≥50% luminal stenosis-was used to grade the extent and severity of CAD. The incremental prognostic value of CCTA over and above FRS was measured by the likelihood ratio (LR) χ(2), C-statistic, and continuous net reclassification improvement (NRI) for prediction, discrimination, and reclassification of all-cause mortality and non-fatal myocardial infarction. During a median follow-up of 24 months (25th-75th percentile, 17-30 months), there were 58 composite end-points. The incremental value of CCTA over FRS was demonstrated in individuals with CACS >100 (LRχ(2), 25.34; increment in C-statistic, 0.24; NRI, 0.62, all P < 0.001), but not among those with CACS ≤100 (all P > 0.05). For subgroups with CACS >100, the utility of CCTA for predicting the study end-point was evident among individuals whose CACS ranged from 101 to 400; the observed predictive benefit attenuated with increasing CACS.

CONCLUSION

Coronary CT angiography provides incremental prognostic utility for prediction of mortality and non-fatal myocardial infarction for asymptomatic individuals with moderately high CACS, but not for lower or higher CACS.

Recent improvement in coronary computed tomography angiography diagnostic accuracy

Although invasive coronary angiography has been the gold standard for evaluating coronary artery disease (CAD), it should not be routinely performed as an initial test to assess CAD in subjects with suspected CAD by the recent guidelines, due to cost, invasiveness, and measurable risk. Coronary computed tomography angiography (CCTA) is a rapidly growing, noninvasive imaging modality that developed quickly over the last decade, and its role for evaluation of CAD becomes of great promise with high diagnostic accuracy. Although artifact issues have created some challenges for CCTA, recent advances-including the introduction of more detectors, leading to broader coverage, and faster and higher-definition scanners-allow improved precision and fewer uninterpretable studies. This review article summarizes the current key literature regarding the diagnostic accuracy of CCTA in native coronary arteries, stents, coronary artery bypass grafts, lesions with high calcification, and the functional assessment of CAD.

Improved evaluation of calcified segments on coronary CT angiography: a feasibility study of coronary calcium subtraction

We explore the feasibility of coronary calcium subtraction computed tomography angiography (CCTA) in patients with high calcium scores using invasive coronary angiography as the gold standard. Eleven patients with calcium scores of >400 underwent CCTA using a subtraction protocol followed by invasive coronary angiography. In addition to standard reconstructions, subtracted images were obtained using a dedicated subtraction algorithm. A total of 55 calcified segments were evaluated for image quality [using a 4-point scale ranging from 1 (uninterpretable) to 4 (good)] and the presence of significant (≥ 50 %) luminal stenosis. Conventional and subtracted CCTA were compared using quantitative coronary angiography (QCA) as the gold standard. The average image quality of conventional CCTA was 2.5 ± 0.6 versus 3.1 ± 0.6 on subtraction CCTA (P < 0.001). The percentage of segments with a score 1 or 2 was reduced from 41.8 to 12.7 % after coronary calcium subtraction (P = 0.002). On QCA, significant stenosis was observed in 16 segments. The area under the receiver operating characteristics curve to detect ≥ 50 % stenosis on QCA increased from 0.741 [95 % confidence interval (CI) 0.598-0.885] for conventional CCTA to 0.905 (95 % CI 0.791-1.000) for subtraction CCTA (P = 0.003). In patients with extensive calcifications undergoing CCTA, coronary calcium subtraction may improve the evaluation of calcified segments.

Accuracy and predictive value of coronary computed tomography angiography for the detection of obstructive coronary heart disease in patients with an Agatston calcium score above 400

PURPOSE

We assessed the accuracy of coronary computed tomography angiography (CTA) in patients with an Agatston calcium score (ACS) of greater than 400 by comparing it with invasive coronary angiography (ICA), and we evaluated the predictive value of CTA for obstructive coronary heart disease (CHD) compared with traditional clinical risk assessment.

METHODS

A total of 253 patients who had an ACS of greater than 400 were enrolled in this study. The degree of coronary stenosis was visually and quantitatively estimated by postprocessing imaging using 15-segment coronary models. All patients underwent ICA after a mean (SD) of 34 (24) days, and the degree of coronary stenosis was compared with the results of CTA.

RESULTS

Computed tomography angiography accurately diagnosed significant stenosis in 204 (99.0%) of 206 patients and in 649 (83.5%) of 777 segments. When the patients were considered based on their ACS (group A, 400 < ACS ≤ 1000, vs group B, ACS > 1000), group B showed lower specificity (9.1% vs 41.7%) and poorer agreement (k = 0.149 vs 0.495) than for ICA. By segment-based analysis, the agreement between CTA and ICA was good (k = 0.729), and there was no significant difference between groups A (k = 0.728) and B (k = 0.727). Computed tomography angiography was the most powerful predictor (odds ratio = 52.645, P < 0.001), whereas the 10-year CHD risk and pretest probability were not significantly correlated with obstructive CHD.

CONCLUSIONS

Despite good overall diagnostic accuracy, coronary CTA in this group of patients was limited by low specificity. However, CTA was a better predictor of obstructive CHD compared with clinical predictors, and it avoided unnecessary ICA, even in patients with extensive coronary artery calcification.

Significance of coronary calcification for prediction of coronary artery disease and cardiac events based on 64-slice coronary computed tomography angiography

This work aims to validate the clinical significance of coronary artery calcium score (CACS) in predicting coronary artery disease (CAD) and cardiac events in 100 symptomatic patients (aged 37-87 years, mean 62.5, 81 males) that were followed up for a mean of 5 years. Our results showed that patients with CAD and cardiac events had significantly higher CACS than those without CAD and cardiac events, respectively. The corresponding data were 1450.42 ± 3471.24 versus 130 ± 188.29 (P < 0.001) for CAD, and 1558.67 ± 513.29 versus 400.46 ± 104.47 (P = 0.031) for cardiac events. Of 72 patients with CAD, cardiac events were found in 56 (77.7%) patients. The prevalence of cardiac events in our cohort was 13.3% for calcium score 0, 50% for score 11-100, 56% for score 101-400, 68.7% for score 401-1,000, and 75.0% for score >1000. Increased CACS (>100) was also associated with an increased frequency of multi-vessel disease. Nonetheless, 3 (20%) out of 15 patients with zero CACS had single-vessel disease. Significant correlation (P < 0.001) was observed between CACS and CAD on a vessel-based analysis for coronary arteries. It is concluded that CACS is significantly correlated with CAD and cardiac events.

Assessment of coronary artery disease using coronary computed tomography angiography in patients with aortic valve stenosis referred for surgical aortic valve replacement

BACKGROUND

In patients referred for aortic valve replacement (AVR) a pre-surgical assessment of coronary artery disease is mandatory to determine the possible need for additional coronary artery bypass grafting. The diagnostic accuracy of coronary computed tomography angiography (coronary CTA) was evaluated in patients with aortic valve stenosis referred for surgical AVR.

METHODS

Between March 2008 and March 2010 a total of 181 consecutive patients were included. All patients underwent pre-surgical coronary CTA (64- or 320-detector CT scanner) and invasive coronary angiography (ICA). The analyses were performed blinded to each other.

RESULTS

The mean ± SD age of the included patients was 71 ± 9 years and 59% were male. The prevalence of significant coronary artery stenosis >70% by ICA was 36%. Average heart rate during coronary CTA was 65 ± 16 b pm. In a patient based analysis 94% of the patients (171/181) were considered fully evaluable. Coronary CTA had a sensitivity of 68%, a specificity of 91%, a positive predictive value of 81%, and a negative predictive value of 83%. Advanced age, obstructive lung disease, NYHA function class III/IV, and high Agatston score were found to be significantly associated with disagreement between ICA and coronary CTA in univariate analysis.

CONCLUSION

In patients with aortic valve stenosis referred for surgical AVR the diagnostic accuracy of coronary CTA to identify significant coronary artery disease is moderate. Coronary CTA may be used successfully in a subset of patients with low age, no chronic obstructive lung disease, NYHA function class<III and low coronary Agatston score.