Coronary 64-slice CT angiography predicts outcome in patients with known or suspected coronary artery disease

[Cardiac hybrid imaging]

CT coronary angiography and myocardial perfusion scintigraphy are both established noninvasive techniques for the diagnosis of coronary artery disease (CAD). Cardiac hybrid imaging consists of the combination (or fusion) of both modalities and allows obtaining complementary morphological (coronary anatomy, stenoses) and functional (myocardial perfusion) information in a single image. The increased availability of these techniques in clinical practice has also raised a controversy with regard to which patients should undergo such integrated examinations. The feasibility and clinical value of hybrid imaging has been documented in small cohort studies and selected series of patients. The incremental value of the hybrid technique arises from the spatial co-registration of perfusion defects with coronary stenoses. This allows an assessment of the hemodynamic relevance of coronary stenoses and the determination of the need for revascularization procedures in each individual artery. Thus, it can be anticipated that the ongoing efforts to reduce radiation exposure and the increasing clinical interest will further pave the way for an ever-increasing use of cardiac hybrid imaging in clinical practice.

Prognostic value of CT angiography for major adverse cardiac events in patients with acute chest pain from the emergency department: 2-year outcomes of the ROMICAT trial

OBJECTIVES

The aim of this study was to determine the 2-year prognostic value of cardiac computed tomography (CT) for predicting major adverse cardiac events (MACE) in patients presenting to the emergency department (ED) with acute chest pain.

BACKGROUND

CT has high potential for early triage of acute chest pain patients. However, there is a paucity of data regarding the prognostic value of CT in this ED cohort.

METHODS

We followed 368 patients from the ROMICAT (Rule Out Myocardial Infarction Using Computer Assisted Tomography) trial (age 53 ± 12 years; 61% male) who presented to the ED with acute chest pain, negative initial troponin, and a nonischemic electrocardiogram for 2 years. Contrast-enhanced 64-slice CT was obtained during index hospitalization, and caregivers and patients remained blinded to the results. CT was assessed for the presence of plaque, stenosis (>50% luminal narrowing), and left ventricular regional wall motion abnormalities (RWMA). The primary endpoint was MACE, defined as composite cardiac death, nonfatal myocardial infarction, or coronary revascularization.

RESULTS

Follow-up was completed in 333 patients (90.5%) with a median follow-up period of 23 months. At the end of the follow-up period, 25 patients (6.8%) experienced 35 MACE (no cardiac deaths, 12 myocardial infarctions, and 23 revascularizations). Cumulative probability of 2-year MACE increased across CT strata for coronary artery disease (CAD) (no CAD 0%; nonobstructive CAD 4.6%; obstructive CAD 30.3%; log-rank p < 0.0001) and across combined CT strata for CAD and RWMA (no stenosis or RWMA 0.9%; 1 feature-either RWMA [15.0%] or stenosis [10.1%], both stenosis and RWMA 62.4%; log-rank p < 0.0001). The c statistic for predicting MACE was 0.61 for clinical Thrombolysis In Myocardial Infarction risk score and improved to 0.84 by adding CT CAD data and improved further to 0.91 by adding RWMA (both p < 0.0001).

CONCLUSIONS

CT coronary and functional features predict MACE and have incremental prognostic value beyond clinical risk score in ED patients with acute chest pain. The absence of CAD on CT provides a 2-year MACE-free warranty period, whereas coronary stenosis with RWMA is associated with the highest risk of MACE.

The composition and extent of coronary artery plaque detected by multislice computed tomographic angiography provides incremental prognostic value in patients with suspected coronary artery disease

Multislice computed tomographic coronary angiography (CTCA) provides accurate noninvasive assessment of coronary artery disease (CAD). However, data on the prognostic value of CTCA in patients with suspected CAD are only beginning to emerge. The aim of the study was to assess the prognostic value of CTCA in patients with suspected CAD. Patients (males = 259, females = 235; mean age 58.2 ± 9.8 years) with suspected CAD who underwent 16- or 64-slice CTCA were followed for 1,308 ± 318 days for cardiac death, nonfatal myocaridal infarction (MI) and late (>90 days after CTCA) revascularization. Patient outcomes were related to clinical and CTCA data. Cox proportional-hazards model was applied in stepwise forward fashion to identify outcome predictors. Coronary artery plaque was found in 340 patients. Cardiac events occurred in 40 patients including cardiac death (n = 9), nonfatal MI (n = 8) and late revascularization (n = 23). A multivariable analysis identified the following independent predictors for adverse cardiac events: obstructive plaque in a proximal coronary artery segment (hazard ratio (HR) 2.73; 95% confidence interval (CI): 1.35-5.54; P = 0.005), the number of segments with noncalcified plaque(s) (HR 1.53 per segment; 95%CI: 1.21-1.92; P < 0.001), the number of segments with mixed plaque(s) (HR 1.56 per segment; 95%CI: 1.27-1.92; P < 0.001) and the number of segments with calcified plaque(s) (HR 1.21 per segment; 95%CI: 1.07-1.37; P = 0.002). In patients with suspected CAD, both the extent and composition of atherosclerotic plaque as determined by CTCA are prognostic of subsequent cardiac events.

Prognostic value of CT coronary angiography in diabetic and non-diabetic subjects with suspected CAD: importance of presenting symptoms

Aim

To assess the prognostic relevance of 64-slice computed tomography coronary angiography (CT-CA) and symptoms in diabetics and non-diabetics referred for cardiac evaluation.

Methods

We followed 210 patients with diabetes type 2 (DM) and 203 non-diabetic patients referred for CT-CA for ruling out coronary artery disease (CAD). Patients were without known history of CAD and were divided into four categories on the basis of symptoms at presentation (none, atypical angina, typical angina and dyspnoea). Clinical end points were major cardiac events (MACE): cardiac-related death, non-fatal myocardial infarction, unstable angina and cardiac revascularizations. Cox proportional hazard models, with and without adjustment for risk factors and multiplicative interaction term (obstructive CAD × DM), were developed to predict outcome.

Results

DM patients with dyspnoea or who were asymptomatic showed a higher prevalence of obstructive CAD than non-diabetics (p ≤ 0.01). At mean follow-up of 20.4 months, DM patients had worse cardiac event-free survival in comparison with non-DM patients (90% vs. 81%, p = 0.02). In multivariate analysis, CT-CA evidence of obstructive CAD (in DM patients: HR: 6.4; 95% CI: 2.3–17.5; p < 0.001; in non-DM patients: HR: 7.4; 95% CI: 2.1–26.7; p = 0.002) and the presence of typical angina (in DM patients: HR: 2.9; 95% CI: 1.3–6.3; p = 0.007; in non-DM patients: HR: 2.7; 95% CI: 1.1–7.1; p = 0.03) were independent predictors of MACE in both groups. Furthermore, other independent outcome predictors included dyspnoea (HR: 3.8; 95% CI: 1.7–8.5; p = 0.001), the number of segments with any CAD (HR: 1.1; 95% CI: 1.001–1.2; p = 0.04) in DM patients and coronary calcium score >100 in non-DM patients (HR: 5.6; 95% CI: 1.4–21.5; p = 0.01). In Cox regression analysis of the overall population, interaction term obstructive CAD × DM resulted in non-significance.

Conclusions

Among DM patients, dyspnoea carried a high event risk with a MACE rate four times higher. CT-CA findings were strongly predictive of outcome and proved valuable for further risk stratification.

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.

Multislice CT angiography in coronary artery disease: Technical developments, radiation dose and diagnostic value

Multislice computed tomography (CT) angiography has been increasingly used in the detection and diagnosis of coronary artery disease because of its rapid technical evolution from the early generation of 4-slice CT scanners to the latest models such as 64-slice, 256-slice and 320-slice CT scanners. Technical developments of multislice CT imaging enable improved diagnostic value in the detection of coronary artery disease, and this indicates that multislice CT can be used as a reliable less-invasive alternative to invasive coronary angiography in selected patients. In addition, multislice CT angiography has played a significant role in the prediction of disease progression and cardiac events. Despite promising results reported in the literature, multislice CT has the disadvantage of having a high radiation dose which could contribute to the radiation-induced malignancy. A variety of strategies have been currently undertaken to reduce the radiation dose associated with multislice CT coronary angiography while in the meantime acquiring diagnostic images. In this article, the author will review the technical developments, radiation dose associated with multislice CT coronary angiography, and strategies to reduce radiation dose. The diagnostic and prognostic value of multislice CT angiography in coronary artery disease is briefly discussed, and future directions of multislice CT angiography in the diagnosis of coronary artery disease will also be highlighted.

Noninvasive anatomical coronary artery imaging versus myocardial perfusion imaging: which confers superior diagnostic and prognostic information?

Myocardial perfusion imaging (MPI) has been a valuable diagnostic and prognosticating tool for decades, but recently it has been challenged by the growing evidence about either comparable or superior diagnostic and prognostic value of computed tomography (CT)-based anatomical imaging modalities. Although there are some studies suggesting synergy and potential for combined use of these modalities to better diagnose coronary artery disease (CAD), it is important to evaluate these approaches separately, given cost and other restraints. This review compares the noninvasive anatomical imaging modalities of coronary artery calcium scoring and coronary CT angiography to the functional assessment modality of MPI in the diagnosis and prognostication of significant CAD in symptomatic patients. A large number of studies investigating this subject are analyzed with a critical look on the evidence, underlying the strengths and limitations. Although the overall findings of the presented studies are favoring the use of CT-based anatomical imaging modalities over MPI in the diagnosis and prognosticating of CAD, the lack of a high number of large- scale, multicenter randomized controlled studies limits the generalizability of this early evidence. Further studies comparing the short- and long-term clinical outcomes and cost-effectiveness of these tests are required to determine their optimal role in the management of symptomatic patients with suspected CAD.

Clinical Role of Hybrid Imaging

Recent technological advances have fueled the growth in hybrid radionuclide and CT imaging of the heart. Noninvasive imaging studies are reliable means to diagnose coronary artery disease (CAD), stratify risk, and guide clinical management. Myocardial perfusion scintigraphy is a robust, widely available noninvasive modality for the evaluation of ischemia from known or suspected CAD. Cardiac CT (coronary artery calcium score and coronary CT angiography) has emerged as a clinically robust noninvasive anatomic imaging test, capable of rapidly diagnosing or excluding obstructive CAD. Both anatomic and functional modalities have strengths and weaknesses, and can complement each other by offering integrated structural and physiologic information. As we discuss below, in selected patients, hybrid imaging may facilitate more accurate diagnosis, risk stratification, and management in a "one-stop shop" setting.

Prognostic value of coronary computed tomographic angiography in comparison with calcium scoring and clinical risk scores

BACKGROUND

Several studies have demonstrated a high accuracy of coronary computed tomography angiography (CCTA) for detection of obstructive coronary artery disease (CAD), whereas some studies have also shown a good prediction of cardiac events. However, it remains to be proven whether CCTA is better predictive of events than conventional risk scores or calcium scoring. Therefore, we compared CCTA with calcium scoring and clinical risk scores for the ability to predict cardiac events.

METHODS AND RESULTS

Patients (n=2223) with suspected CAD undergoing CCTA were followed up for a median of 28 months. The end point was the occurrence of cardiac events (cardiac death, nonfatal myocardial infarction, unstable angina requiring hospitalization, and coronary revascularization later than 90 days after CCTA). Patients with obstructive CAD had a significantly higher event rate (2.9% per year; 95% confidence interval, 2.1 to 4.0) than those without obstructive CAD, having an event rate 0.3% per year (95% confidence interval, 0.1 to 0.5; hazard ratio, 13.5; 95% confidence interval, 6.7 to 27.2; P<0.001). CCTA had significant incremental predictive value when compared with calcium scoring, both with scores assessing the degree of stenosis (P<0.001) and with scores assessing the number of diseased coronary segments (P=0.027).

CONCLUSIONS

In patients with suspected CAD, CCTA not only detects coronary stenosis but also improves prediction of cardiac events over and above conventional risk scores and calcium scoring. This may result in a reclassification of cardiovascular risk in a substantial proportion of patients.

Prevalence and extent of coronary artery disease determined by 64-slice CTA in patients with zero coronary calcium score

The purpose of the study was to assess the presence and extent of atherosclerosis determined by 64-slice CTA in patients with 0 coronary calcium score (CACS) and to evaluate the affect of demographic features and risk factors on the atheroma burden of these patients. 883 cases (378 (42.8%) male, 505 (57.2%) female, mean age 51.28) with zero CACS were included in the study. Cases underwent CTA because of carrying risk factors or having chest pain or atypical symptoms. A non-enhanced CT scan was obtained for calcium scoring immediately before CTA in all cases. CT examinations were performed by 64-slice scanner (Toshiba, Aquillon 64, Toshiba Medical Systems, Otowara, Japan). Coronary artery disease (CAD) was graded according to CTA findings and five groups were defined. In 703 cases (79.6%) CTA was normal while 180 (20.4%) cases had positive CTA findings and 43 cases (4.9%) had CTA obstructive lesion. Cases with positive CTA findings were significantly older than those with normal CTA Diabetes was a significant risk factor of CAD in both male and female cases. Dyslipidemia was associated with CAD in males and family history of CAD was a significant risk factor for females with positive CTA findings. This study demonstrated that considerable amount of patients with zero CAC score have positive CTA findings. Age and diabetes are the risk factors, which were associated with positive CTA findings in both sexes. Dyslipidemia was a significant risk factor in males and family history of CAD in females. Especially in patients with risk factors CTA is better than CAC scoring in determining the atheroma burden.

Myocardial perfusion imaging with first-pass computed tomographic imaging: Measurement of coronary flow reserve in an animal model of regional hyperemia

BACKGROUND

The accurate assessment of myocardial blood flow (MBF) is a potential adjunct to the anatomy of CT coronary angiography.

PURPOSE

To compare semi-quantitative parameters from first-pass CT (FP CT) imaging with absolute measures of MBF in an animal model of altered MBF.

METHODS

A pig model of intracoronary adenosine (n = 8) was used during FP CT. This produces a zone with hyperemic MBF and a control zone within a slice. A subset of these animals also underwent LAD occlusion with imaging. Fluorescent microspheres (Mcsp) were injected into the left atrium to determine absolute MBF concurrent with CT imaging. Pigs were placed in a 64-slice (Philips) CT with acquisition performed during IC adenosine and occlusion. A 40% dilution of Iopamidol 370 (1 mL/kg) was injected IV at 5 mL/second. CT acquisition was ECG gated over 40 cardiac phases with the following parameters: 180 degrees axial mode (pitch = 0), field of view = 250 mmsq, 512 x 512 matrix, slice thickness = 2.5 mm x 10 slices, temporal resolution = 330 ms, 120 kV, 495 ma. Mcsp were injected immediately following CT imaging. The heart was sectioned into 2.5 mm slices to match the CT images and segmented. Time attenuation curves (TAC) were generated from CT in intervention and control zones based on Mcsp values. Mcsp coronary flow reserve (CFR) = hyperemic/control MBF, and CT CFR was derived from intervention/control area under curve from baseline corrected TIC.

RESULTS

MBF control = .65 +/- .28, MBF adenosine = 2.6 +/- .7 mL/min/g (P < .0001). CFR = 4.1 +/- 1.1, CT CFR = 4.3 +/- 1.4 (P = NS). There was a significant (r = .94, P < .0001) correlation between CFR and CT CFR.

CONCLUSIONS

CT first-pass myocardial perfusion imaging is feasible using a simple semi-quantitative analysis which provides reasonable estimates of MBF.

Diabetes: prognostic value of CT coronary angiography--comparison with a nondiabetic population

PURPOSE

To evaluate the prognostic value of multidetector computed tomographic (CT) coronary angiography in a diabetic population known to have or suspected of having coronary artery disease (CAD) compared with that in nondiabetic individuals.

MATERIALS AND METHODS

Institutional review board approval and patient informed consent were obtained. Three hundred thirteen patients with type 2 diabetes mellitus (DM) and 303 patients without DM underwent unenhanced 64-detector row CT, at which a calcium score was obtained, followed by CT angiography. Multidetector CT coronary angiograms were retrospectively classified as normal, showing nonobstructive CAD (<or=50% luminal narrowing), or showing obstructive CAD (>50% luminal narrowing). During follow-up after CT angiography, major events (cardiac death, nonfatal myocardial infarction, and unstable angina requiring hospitalization) and total events (major events plus coronary revascularizations) were recorded for each patient. Cox proportional hazards analysis and Kaplan-Meier analysis were used to compare survival rates.

RESULTS

In the group of 313 patients with DM, there were 213 men, and the mean age was 62 years +/- 11 (standard deviation). In the group of 303 patients without DM, there were 203 men, and the mean age was 63 years +/- 11. The mean number of diseased segments (5.6 vs 4.4, P = .001) and the rate of obstructive CAD (51% vs 37%, P < .001) were higher in patients with DM. Patients were followed up for a mean of 20 months +/- 5.4 (range, 6-44 months). At multivariate analysis, DM (P < .001) and evidence of obstructive CAD (P < .001) were independent predictors of outcome. Obstructive CAD remained a significant multivariate predictor for both patients with DM and patients without DM. In both patients with DM and patients without DM with absence of disease, the event rate was 0%. The event rate increased to 36% in patients without DM but with obstructive CAD and was highest (47%) in patients with DM and obstructive CAD.

CONCLUSION

In both patients with DM and patients without DM, multidetector CT coronary angiography provides incremental prognostic information over baseline clinical variables, and the absence of atherosclerosis at CT coronary angiography is associated with an excellent prognosis. Multidetector CT coronary angiography might be a clinically useful tool for improving risk stratification in both patients with DM and patients without DM.

Low dose CT of the heart: a quantum leap into a new era of cardiovascular imaging

In 10 years, computed tomography coronary angiography (CTCA) has shifted from an investigational tool to clinical reality. Even though CT technologies are very advanced and widely available, a large body of evidence supporting the clinical role of CTCA is missing. The reason is that the speed of technological development has outpaced the ability of the scientific community to demonstrate the clinical utility of the technique. In addition, with each new CT generation, there is a further broadening of actual and potential applications. In this review we examine the state of the art on CTCA. In particular, we focus on issues concerning technological development, radiation dose, implementation, training and organisation.

Prognostic value of absence or presence of coronary artery disease determined by 64-slice computed tomography coronary angiography a systematic review and meta-analysis

To determine via a meta-analysis the prognostic value of 64-slice computed tomography angiography (CTA) by quantifying risk of major adverse cardiac events (MACE) in different patient groups classified according to CT angiographic findings. A systematic literature search and meta-analyses was conducted on 10 studies examining stable, symptomatic and intermediate risk patients by 64-slice CTA. Patients were followed up for a mean of 21 month. Patient groups with CT-angiographic non-obstructive (stenosis <50% of luminal narrowing) or obstructive (stenosis ≥50% of luminal narrowing) CAD were compared to those having normal angiography without CAD. MACE (cardiac death, non-fatal myocardial infarction and revascularization) numbers were used to calculate odds ratios (OR) with 95% confidence interval (CI) in each group. Ten studies including 5,675 patients were eligible for meta-analysis. The cumulative MACE rate over 21 months were 0.5% in patients with normal CTA, 3.5% in non-obstructive CAD and 16% in obstructive CAD. Compared to normal CTA, non-obstructive CAD was associated with significant increased risk of MACE with OR=6.68 (3.01-14.82 CI 95%), P=0.0001. Obstructive CAD was associated with further significant increased risk of MACE with OR=41.19 (22.56-75.18, CI 95%), P=0.0001. The studies were homogenous, P-value >0.05 for heterogeneity. 64-slice CTA is able to differentiate low-risk from high-risk patients with suspected or known CAD. Absence of CAD predicts excellent prognosis, while obstructive CAD is associated with markedly increased risk of MACE.

Sex differences in mortality associated with computed tomographic angiographic measurements of obstructive and nonobstructive coronary artery disease: an exploratory analysis

BACKGROUND

Sex differences exist in the prevalence and severity of obstructive coronary artery disease (CAD). Limited data are available to explore sex differences in prognosis with coronary computed tomographic angiographic (CCTA) measurements of CAD including novel nonobstructive plaque extent.

METHODS AND RESULTS

A total of 1127 consecutive patients were clinically referred to 16-slice CCTA and followed for the occurrence of all-cause death. Time to death was calculated by univariable and multivariable Cox proportional hazard models. Four-year survival (92.1%) was similar by sex (P=0.52). Women more often had no coronary stenosis (54%) as compared with men (28%) (P<0.0001). Mortality worsened for both women (P<0.0001) and men (P=0.002) by the number of vessels with > or =50% stenosis. For women, overall mortality ranged from 3.5% for no CAD to 25.0% for women with 3-vessel plus left main obstructive CAD (P<0.0001). For men, overall mortality ranged from 2.7% for no CAD to 17.4% for males with 3-vessel plus left main obstructive CAD (P=0.002). Nonobstructive disease was prevalent in women (range, 24% to 66%) and men (range, 45% to 74%) ages 45 to > or =80 years. Nonobstructive CAD extent was a significant estimator of all-cause mortality when added to a model containing pretest CAD likelihood and obstructive CAD extent (P=0.039). For men, in a risk-adjusted model including pretest CAD likelihood and obstructive CAD, the number of nonobstructive lesions was not a significant estimator of mortality (P=0.9). For women, the relative hazard for mortality, in a multivariable model, was 1.3 per nonobstructive lesion (P=0.003), including pretest CAD likelihood and obstructive CAD as covariates. For women, risk-adjusted median mortality ranged from 2.9% to 10.9% for none to > or =4 nonobstructive lesions (P<0.0001).

CONCLUSIONS

Based on our preliminary analyses, CCTA obstructive and nonobstructive CAD adds incremental value to clinical assessment for risk stratification. Moreover, the extent of nonobstructive CAD by CCTA predicts mortality in women but not in men and may be helpful to optimize therapeutic strategies for women.

Computed tomography of the coronary arteries in diagnosis

IMPORTANCE OF THE FIELD

Cardiac computed tomography (CT) has recently emerged as a non-invasive alternative to catheter angiography for the assessment of coronary artery disease. Rapid technological advances have rendered coronary CT angiography to a robust, accurate and fast imaging modality to assess coronary artery disease in selected patients. The list of further indications in which cardiac CT is an appropriate test remains a topic of discussion.

AREAS COVERED IN THIS REVIEW

This review discusses the main literature available on the use of cardiac CT in the indications considered appropriate in the 2006 Appropriateness Criteria by the American College of Radiology with special emphasis on the temporal trends in the utilization of cardiac CT in clinical practice and in the opinion of the experts, and provides an outlook on how cardiac CT might evolve in the future.

WHAT THE READER WILL GAIN

The reader will gain insight into the strengths and shortcomings of CT of the coronary arteries in coronary artery diagnosis and will learn why cardiac CT is appropriate in some indications but not in others.

TAKE HOME MESSAGE

Recent research in cardiac CT has substantially improved the evaluation of the coronary arteries with CT, and the list of indications cardiac CT is appropriate for might expand further in the coming years.

The prognostic value of cardiac computed tomographic angiography

With advancements in temporal and spatial resolution, CT has excellent diagnostic characteristics for non-invasive evaluation of coronary artery disease in appropriate patients. Nevertheless, clinical usefulness of diagnostic testing requires not only high diagnostic accuracy but also risk stratification for patient management. Current guidelines for risk stratification of patients with coronary artery disease rely primarily upon functional testing; alternatively, anatomic risk stratification may also be performed with invasive coronary angiography. This article reviews current and emerging concepts in the prognostic value of cardiac CT angiography.

The role of calcium score and CT angiography in the medical management of patients with normal myocardial perfusion imaging

BACKGROUND

Individuals with normal myocardial perfusion imaging (MPI) may still have substantial coronary artery disease (CAD), which would benefit from aggressive medical therapy. The role of coronary artery calcium-score (CAC) and/or coronary CT Angiography (CTA) to identify additional treatment candidates in this population is unknown.

METHODS

Ninety-four patients completed the study protocol and underwent CAC and CTA after MPI.

RESULTS

In 81 patients who had a normal MPI, an algorithm using the clinical predictors, CAC, and then CTA was created to identify candidates for aggressive medical management; 24/81 patients had a high Framingham Risk Score (FRS) or diabetes, and need aggressive medical management, while 6/81 patients had a low FRS and low post-MPI probability of CAD. The use of CAC in 51/81 patients with intermediate clinical predictors would identify 23/51 patients with low risk (CAC < 100) and 11/51 patients (CAC > 400) for aggressive medical management. The remaining 17/51 patients with intermediate CAC scores (100-399) would require CTA, of which, would identify 8/17 additional patients with >50% stenosis for aggressive medical therapy.

CONCLUSION

A stepwise approach including history, CAC and CTA can identify about 50% of the patients with normal MPI who have a higher risk and may benefit from aggressive medical management.

The value of multi-slice-computed tomography coronary angiography for risk stratification

Multi-slice-computed tomography coronary angiography (CTA) provides direct non-invasive anatomic assessment of the coronary arteries allowing for early identification of coronary artery disease (CAD). This information is useful for diagnosis of CAD, particularly the rule out of CAD. In addition, early identification of CAD with CTA may also be useful for risk stratification. The purpose of this review is to provide an overview of the current literature on the prognostic value of CTA and to discuss how the prognostic information obtained with CTA can be used to further integrate the technique into clinical practice. Non-invasive anatomic assessment of plaque burden, location, composition, and remodeling using CTA may provide prognostically relevant information. This information has been shown to be incremental to the Framingham risk score, coronary artery calcium scoring, and myocardial perfusion imaging. Characterization of atherosclerosis non-invasively has the potential to provide important prognostic information enabling a more patient-tailored approach to disease management.Future studies assessing outcome after CTA-based risk adjustments are needed to further understand the value of detailed non-invasive anatomic imaging.

Coronary CTA: stenosis classification and quantification, including automated measures

The development of larger multidetector computed tomography (CT) systems has allowed increased accuracy in quantifying obstructive lesions involving the coronary arteries. This article reviews the accuracy of coronary CT angiography (CTA) in quantifying obstructive lesions, evaluating the extent of coronary artery disease, and classifying the composition of coronary plaques. In addition, several outcomes studies and some promising automated techniques for quantifying coronary CTA are reviewed.

Impact of coronary computed tomographic angiography findings on the medical treatment and control of coronary artery disease and its risk factors

Although coronary computed tomographic angiography (CCTA) has high diagnostic accuracy and increasing evidence of prognostic value for coronary artery disease (CAD), its downstream clinical impact is not established. In this study, the association of findings on CCTA with subsequent treatment and control of CAD risk factors was assessed in 208 consecutive symptomatic outpatients without known CAD who underwent CCTA. Blood pressure (BP), lipid levels, and CAD medications were compared before and after CCTA (mean follow-up period 8.1 +/- 6.6 months). CAD severity on CCTA was graded as absent, mild (1% to 49%), moderate (50% to 69%), or severe (> or =70%) stenosis. In patients with absent, mild, moderate, and severe CAD on CCTA, aspirin was initiated in 0%, 14%, 36%, and 15%; statins were initiated or increased in 4%, 23%, 44%, and 42% of patients; and BP medications were initiated or increased in 16%, 10%, 26%, and 38% of patients (p <0.05 for severe vs no CAD for all). Higher grades of CAD severity were independently associated with greater post-CCTA use of aspirin (odds ratio 3.2 per grade, p <0.001) and statins (odds ratio 3.6 per grade, p <0.001), but not BP medications. Greater CAD severity was independently associated with lower post-test total cholesterol (-8.2 mg/dl per grade, p = 0.02), low-density lipoprotein cholesterol (-6.8 mg/dl per grade, p = 0.04), and diastolic BP (-1.4 mm Hg per grade, p = 0.03), but not systolic BP. In conclusion, greater CAD severity on CCTA is associated with enhanced medical treatment and improved control of CAD risk factors.

Risk assessment and predictive value of coronary artery disease testing

This review highlights and compares risk assessment, predictive accuracy, and economic outcomes for 3 commonly applied cardiac imaging procedures: stress myocardial perfusion SPECT or PET and coronary CT angiography (CCTA). This review highlights an expansive evidence base for stress myocardial perfusion imaging and reveals a decided advantage for higher-risk patients, notably those who have established coronary artery disease (CAD). It is likely that the use of CCTA will continue to expand, particularly for patients with more atypical symptoms and patients with a lower likelihood of CAD. Despite a high level of evidence, comparative research is not available across modalities that could definitively drive utilization of cardiac imaging modalities.

Prognostic value of coronary computed tomographic angiography for prediction of cardiac events in patients with suspected coronary artery disease

OBJECTIVES

We assessed the rate of cardiac events after detection or exclusion of obstructive coronary artery disease (CAD) by coronary computed tomography angiography (CCTA).

BACKGROUND

Several studies have demonstrated a high diagnostic accuracy of CCTA for detection of obstructive CAD compared with invasive angiography, but data regarding the clinical prognostic value of CCTA are limited.

METHODS

In all, 1,256 consecutive patients with suspected CAD undergoing 64-slice CCTA in our institution between October 2004 and September 2006 were observed prospectively for the occurrence of severe cardiac events (cardiac death, myocardial infarction, or unstable angina requiring hospitalization: primary study end point) and all cardiac events (additionally including revascularization >90 days after CCTA). The observed rate of all cardiac events was compared with the event rate predicted by the Framingham risk score. Obstructive CAD was defined as > or = 50% diameter stenosis in any coronary artery.

RESULTS

During a median follow-up of 18 months (interquartile range 14 to 25 months), the overall rates of severe and all cardiac events were 0.6% and 1.8%, respectively. In 802 patients without obstructive CAD, there were 4 cardiac events, of which 1 was severe, whereas in 348 patients with obstructive CAD, there were 17 cardiac events, of which 5 were severe. The difference between the 2 groups was highly significant both for severe events (odds ratio: 17.3, 95% confidence interval: 3.6 to 82.5) and for all cardiac events (odds ratio: 16.1, 95% confidence interval: 7.2 to 36.0; both p < 0.001). The rate of all cardiac events in patients without obstructive CAD was significantly lower than predicted by the Framingham risk score (p = 0.01).

CONCLUSIONS

In patients with suspected CAD, CCTA has a significant prognostic impact on the prediction of cardiac events for the subsequent 18 months. The exclusion of obstructive CAD by CCTA identifies a patient population with an event risk lower than predicted by conventional risk factors.

Clinical effectiveness of coronary computed tomographic angiography in the triage of patients to cardiac catheterization and revascularization after inconclusive stress testing: results of a 2-year prospective trial

BACKGROUND

Management of patients with suspected coronary artery disease (CAD) and inconclusive stress imaging test findings may result in invasive coronary angiography (ICA). Coronary computed tomographic angiography (CCTA) may be useful in defining the risk of CAD and adverse outcomes in this patient population, as well as in reducing the need for ICA.

METHODS

We prospectively enrolled 199 sequential patients referred by cardiologists for CCTA after either inconclusive or nondiagnostic stress imaging tests. Before CCTA, physicians identified a "planned catheterization" group of patients who would undergo invasive angiography if CCTA were not available. After CCTA testing, patients were followed for >or=2 years. We established the added diagnostic value of the CCTA and its prognostic power in prediction of intermediate-term follow-up events in this patient population as compared to available historical and clinical predictors of CAD, stress ECG, and stress imaging test results using a multivariable Cox proportional hazards survival analysis.

RESULTS

Both observed data and results of the multivariable model for the prediction of obstructive CAD (>50% stenosis), or major cardiac events (death MI or revascularization), demonstrated that clinical, stress ECG, and imaging results were weakly predictive, whereas CCTA was found to be a strong independent and incremental predictor of the absence of either significant CAD or MACE in this population. None of the 93 patients with normal CCTA scans had MACE events, whereas 18 patients with evidence of CAD on the CCTA results underwent revascularization. Overall, physicians planned ICA in 125 patients (63.0%); after CCTA, ICA was performed in only 32 (16.0%) cases over 2 years. In this population with no other highly effective noninvasive clinical tools for diagnostic and prognostic estimation, the overall negative predictive value of CCTA for either CAD > 50% or MACE for 2 years was 99%.

CONCLUSION

Observations from this prospective study demonstrate the significant added diagnostic value and prognostic potential of CCTA in patients with suspected CAD and either inconclusive or nondiagnostic stress test results in real-world settings. Normal CCTA results are associated with excellent intermediate-term prognosis in this clinical subset, and invasive angiography can be safely avoided in the majority of these patients when the results of CCTA are available.

Three-year outcomes and cost analysis in patients receiving 64-slice computed tomographic coronary angiography for chest pain

Sixty-four slice computed tomographic coronary angiography (CTCA) is being used more often in the evaluation of patients with chest pain. The strength of this test is its high specificity and negative predictive value in exclusion of coronary artery disease (CAD). Its use remains controversial because there are theoretical risks of radiation, additional costs of the test, and no long-term data to suggest that excluding CAD by use of this test results in positive patient outcomes. A total of 436 patients underwent 64-slice CTCA because of chest pain thought to be anginal. Cardiac computed tomography was ordered by the primary physician or cardiologist based on a low to intermediate pretest probability of flow-limiting CAD. A smaller subset of patients initially underwent stress testing but had equivocal findings or continued symptoms that warranted further evaluation. Of the total patient cohort, 376 had "no significant CAD" based on computed tomographic coronary angiographic results. Of the 60 patients who were believed on computed tomographic coronary angiogram to have "flow-limiting" CAD, 34 (57%) ended up having percutaneous coronary intervention or coronary artery bypass grafting. The remaining 26 patients (43%) did not have true flow-limiting disease on coronary catheterization and were treated medically. With follow-up of 36 months, 376 of those patients (100%) with minimal or no disease by CTCA were free of events or intervention. In conclusion, in a real-world, clinical setting, the negative predictive value of low-risk CTCA is very high and exceptionally helpful in predicting freedom from events for up to 3 years. By avoiding further invasive treatments, there is a significant potential cost savings in patients who are sent for noninvasive coronary angiography rather than invasive angiography.