Clinical use of coronary computed tomographic angiography

INTRODUCTION — Coronary computed tomographic angiography (CCTA) is a well-validated and increasingly utilized noninvasive test for the assessment of coronary artery disease (CAD) in appropriately selected patients with suspected acute or chronic coronary syndromes. In addition to detecting CAD, CCTA is an excellent method to exclude angiographically significant coronary stenoses.

This topic will discuss the clinical role for CCTA in the evaluation of patients with suspected acute or chronic coronary syndromes. Discussions regarding coronary calcium scoring and other methods for evaluations of suspected CAD are presented separately.

●(See "Coronary artery calcium scoring (CAC): Overview and clinical utilization".)

●(See "Selecting the optimal cardiac stress test".)

●(See "Overview of stress radionuclide myocardial perfusion imaging".)

●(See "Overview of stress echocardiography".)

OVERVIEW OF INDICATIONS — The principal indications for CCTA include (image 1):

●As an alternative to stress testing as the initial test in patients with chronic (stable) symptoms suggestive of ischemic heart disease who do not have previously established CAD.

●As an alternative to invasive coronary angiography in patients with nondiagnostic or equivocal stress test results and persistent symptoms in whom a diagnosis of CAD is uncertain. (See 'Patients with nondiagnostic stress tests' below.)

●As the initial test in patients without known CAD who present with possible acute coronary syndrome (ACS) when highly sensitive troponin assay testing and the clinical evaluation cannot confidently exclude ACS. CCTA should not be performed in patients with ongoing chest pain who may have ACS since transporting them is unsafe and CT suites are generally not equipped to deal with potentially unstable patients. (See 'Low suspicion of ACS in low-risk patients' below and "Evaluation of emergency department patients with chest pain at low or intermediate risk for acute coronary syndrome", section on 'Noninvasive evaluation'.)

●As an alternative to stress testing or invasive coronary angiography in selected patients without previously known CAD who are diagnosed with non-ST-elevation ACS with clinically low-risk presentation (eg, absence of heart failure and refractory ischemic symptoms), and in whom there is a clinician or patient desire to avoid invasive coronary angiography, or when the cause for troponin elevation is uncertain. (See 'Patients with low-risk NSTEACS' below and "Risk stratification after non-ST elevation acute coronary syndrome", section on 'Stress testing' and "Stress testing in pre-discharge risk stratification of patients with non-ST elevation acute coronary syndrome", section on 'Who needs a stress test and when should it be performed' and "Non-ST-elevation acute coronary syndromes: Selecting an approach to revascularization", section on 'No objective evidence of ischemia (unstable angina)'.)

●CT-derived fractional flow reserve (CT-FFR) may be helpful in patients who have undergone invasive coronary angiography without invasive FFR and are found to have coronary lesions of intermediate angiographic severity (some experts define this as 50 to 70 percent, whereas others define it as 40 to 70 percent) in segments >2 mm in diameter when such information is likely to change clinical management. (See 'CT-FFR' below and "Cardiac imaging with computed tomography and magnetic resonance in the adult", section on 'Fractional flow reserve'.)

Although screening asymptomatic adults with CCTA frequently detects asymptomatic CAD, among 9533 patients ≥40 years of age, 46 percent had some plaque, 10 percent had “extensive” plaque (involving at least one-third of the coronary segments), and 10 percent had obstructive (≥50 percent stenosis) CAD. The presence of both extensive (regardless of stenosis) and obstructive CAD is independently related to future cardiovascular events (relative risk of myocardial infarction 8.28 [CI 3.75-18.32] and 9.19 [95% CI 4.49-18.11]). We do not recommend CCTA as a screening test in asymptomatic people, as coronary artery calcium scoring may be similarly predictive in asymptomatic patients, preventive measures in these patients have uncertain efficacy, the cost of widespread screening is significant, and due to the potential adverse effects such as radiation and incidental extracardiac findings [1].

DIAGNOSTIC ACCURACY — CCTA (≥64-slice) is highly accurate for the diagnosis of obstructive CAD using invasive coronary angiography (ICA) as the reference standard.

In the VERDICT trial, 1023 patients presenting with suspected non-ST-elevation acute coronary syndrome had CCTA performed prior to invasive coronary angiography in order to exclude coronary artery stenosis ≥50 percent [2]. The population was high risk; 24 percent had known atherosclerotic cardiovascular disease, 43 percent had GRACE score >140, and 78 percent had elevated cardiac troponins. CCTA had good diagnostic performance with a negative predictive value of 90.9 percent (95% CI 86.8-94.1 percent), positive predictive value of 87.9 percent (95% CI 85.3-90.1 percent), sensitivity 96.5 percent (95% CI 94.9-97.8 percent), and specificity of 72.4 percent (95% CI 67.2-77.1 percent) of obstructive CAD.

The strength of CCTA relative to other noninvasive tests for CAD is its high sensitivity for anatomic and functionally significant CAD, defined by ICA and invasive fractional flow reserve (FFR), respectively. Similar to invasive angiography, CCTA has modest specificity for identifying flow-limiting coronary artery lesions as defined by invasive FFR. (See "Clinical use of coronary artery pressure flow measurements".)

In a 2018 meta-analysis involving nine studies and 2078 patients who underwent both CCTA and invasive quantitative coronary angiography, the sensitivity and specificity of the former for ≥50 percent stenosis using ICA as the standard were 97 percent (95% CI 93-99 percent) and 78 percent (95% CI 67-86 percent), respectively [3]. Using invasive FFR ≤0.80 (seven studies, 1049 patients) rather than percent-diameter stenosis as the reference standard, CCTA was found to have sensitivity and specificity of 93 percent (95% CI 89-96 percent) and 53 percent (95% CI 37-68 percent), respectively. These findings were similar to a more recent study with over 1000 patients presenting with non-ST-elevation acute coronary syndrome [2].

Factors that may negatively impact the accuracy of CCTA include image artifacts resulting from coronary artery calcification, arrhythmias, or patient and/or coronary motion, as well as increased image noise due to obesity. Providers should attempt to adhere to Society of Cardiovascular Computed Tomography CCTA performance guidelines to ensure optimal patient selection and preparation (eg, heart rate control, breath hold practice) and CT image acquisition techniques to ensure diagnostic image quality while simultaneously minimizing patient radiation exposure [4]. Patients with known significant coronary calcification (ie, dense, multiple segments), inability to tolerate heart-rate-lowering medications (eg, beta blocker), advanced renal disease, concerns about radiation exposure (see 'Procedural risks' below), or allergy to iodinated contrast are not appropriate candidates for coronary CTA.

CT-FFR — As a purely anatomical test, standard CCTA has only modest specificity for the detection of lesions found to be physiologically significant by abnormal invasive FFR (see "Clinical use of coronary artery pressure flow measurements"). Estimates of invasive FFR based on proprietary computational fluid dynamic modeling applied to static coronary angiograms are commercially available. There have been multiple studies assessing the accuracy of CT-FFR as compared with invasive FFR. Most were performed in high-risk patients clinically referred for ICA and demonstrate that CT-FFR improves the specificity of CCTA for prediction of invasive FFR when utilized for the assessment of lesions of intermediate stenosis severity [5]. In the PACIFIC trial sub-study, investigators assessed high-risk patients undergoing ICA and found CT-FFR to be the most accurate modality for the discrimination of functionally significant CAD (invasive FFR <0.80) compared with CCTA, single photon emission CT (SPECT), and positron emission tomography (PET) alone [6]. The area under the receiver operating characteristic curve for identification of functionally significant lesions was 0.94 versus CCTA (0.83, p<0.01), SPECT (0.70, p<0.01), and PET (0.87, p<0.01). However, this study excluded 25 percent of patients who underwent CCTA who did not have adequate image quality for accurate CT-FFR analysis.

The accuracy of CT-FFR compared with invasive FFR may be lower in patients with CT-FFR values between 0.70 and 0.80 (so called "gray zone") [7]. The technique is not well-validated for the assessment of left main CAD or for patients with three-vessel CAD, particularly when involving total occlusions in the coronary vascular tree. Additionally, CT-FFR may overestimate lesion physiologic significance if CT-FFR values are taken from distal coronary segments well beyond (>2 cm distal to) the lesion in question. Finally, CT-FFR requires high image quality and may not be feasible in studies with significant misalignment or motion artifacts.

PROCEDURAL RISKS — Major potential complications of the procedure include radiation toxicity and contrast-induced nephropathy. Advances in cardiac CT technology and acquisition protocols have resulted in the ability to routinely perform highly diagnostic CCTA studies using significantly less radiation and iodinated contrast.

●Radiation exposure and CCTA image quality were assessed as part of the PROTECTION VI study. During a one-month period in 2017, data from CCTA performed in 61 centers across 32 countries was compared with data from a similar survey performed in 2007 [8]. Studies in 2017 were performed with 78 percent lower median radiation exposure (195 mGy*cm dose-length product) with no increase in nondiagnostic studies (1.9 percent of studies). Using a k-factor of 0.014 mSv/mGy*cm, this corresponds to a median dose of 2.7 mSv, which compares favorably to SPECT (7 to 12 mSv).

●In nonobese patients with slow, (ie, ≤65 beats per minute) stable heart rates, radiation doses during CCTA can be as low as 0.1 millisievert (mSv) and using low tube potential (<100 kVp) and dual-source rapid acquisition techniques (high-pitch helical) [9]. (See "Radiation-related risks of imaging" and "Radiation dose and risk of malignancy from cardiovascular imaging".)

●In patients without preexisting kidney dysfunction, intravenous contrast doses are typically less than 75 mL in most labs, a value associated with very low (<1 percent) rates of contrast-induced nephropathy or adverse outcomes in patients with normal renal function [10,11]. (See "Prevention of contrast-induced acute kidney injury associated with computed tomography" and "Contrast-associated and contrast-induced acute kidney injury: Clinical features, diagnosis, and management".)

PATIENTS WITH STABLE SYMPTOMS — In patients with stable symptoms, CCTA is an alternative diagnostic test to functional stress testing or invasive coronary angiography depending on the patient's clinical situation.

As an alternative to functional stress testing — The evidence presented below supports CCTA as an alternative to functional stress testing in appropriately selected patients. However, other tests such as echocardiography and cardiovascular magnetic resonance imaging may be better choices if noncoronary causes of cardiac symptoms are suspected. Patients who are good candidates for CCTA include those who can safely receive iodinated intravenous contrast and can be expected to achieve high image quality based on ability to achieve a slow, stable heart rate at the time of scanning, able to follow breath-hold instructions, and do not have known significant coronary artery calcification.

Large-scale registries and prospective studies have consistently demonstrated that the results of CCTA have strong prognostic value in stable patients. The following potential findings on CCTA are used for prognostication:

●Presence and extent (number of coronary segments and proximal location) of potentially flow-limiting stenosis (≥50 percent stenosis).

●Presence and extent of nonobstructive plaque (<50 percent stenosis).

●Plaque morphology: Presence of high-risk (vulnerable) plaque features associated with increased patient risk that include low-attenuation plaque (<30 Hounsfield units), positive (expansile) remodeling, spotty calcification (<3 mm), and the napkin-ring sign (low-attenuation surrounded by high attenuation).

Prospective studies comparing CCTA with functional testing have demonstrated that CCTA is a reasonable alternative to functional stress testing in stable patients without known CAD. Potential clinical advantages of CCTA include its high sensitivity (low likelihood to miss clinically significant CAD) and, most notably, its ability to identify nonobstructive (non-flow-limiting) coronary atherosclerosis that may refine estimates of atherosclerotic cardiovascular disease (ASCVD) risk and identify those who will likely benefit from more intensive preventive treatment, such as starting or intensifying statin therapy. (See "Prevention of cardiovascular disease events in those with established disease (secondary prevention) or at very high risk".)

Evidence to support the use of CCTA in clinical practice comes from registries and randomized trials. Examples of registries include:

●The CONFIRM Registry demonstrated that severity of CAD was superior to clinical risk factors, calcium score, and symptoms for predicting long-term patient risk [12].

●In approximately 2000 patients referred for CCTA, the absence of CAD on CCTA was associated with a very low risk of ASCVD events over 10 years of follow-up, with an annual event rate of 0.04 percent [13]. The presence of CAD, including the extent of nonobstructive (<50 percent stenosis) plaque, was superior to clinical risk factors and validated risk scores.

●In a nationwide Danish registry that included 53,744 patients (mean age 57 years) who underwent initial functional testing and 32,961 (mean age 57 years) who underwent initial CCTA, patients who underwent CCTA were significantly more likely to be subsequently prescribed statins (15.9 versus 9.1 percent) and aspirin (12.7 versus 8.5 percent), be referred for invasive coronary angiography (14.7 versus 10.1 percent), and undergo percutaneous coronary intervention (3.8 versus 2.1 percent) [14]. CCTA was associated with similar all-cause mortality (HR 0.96; 95% CI 0.88-1.05) and lower risk of incident myocardial infarction (MI; hazard ratio [HR] 0.74; 95% CI 0.61-0.82).

Examples of randomized trials include:

●SCOT-HEART was a prospective, randomized open-label trial that compared standard of care plus CCTA with standard of care alone in 4146 symptomatic patients (mean age 57 years; 37 percent typical angina). Most patients (85 percent) underwent nonimaging exercise treadmill testing as initial testing prior to enrollment [15]. The following findings were noted:

•After five years, patients randomized to CCTA had similar rates of invasive coronary angiography and revascularization.

•Patients randomized to CCTA had a 40 percent lower risk of death from coronary heart disease or nonfatal MI (HR 0.59; 95% CI 0.41-0.84) driven predominately by lower rate of MI. There were no between-group differences in the rates of cardiovascular or noncardiovascular deaths.

•Patients who underwent CCTA were 40 percent more likely to be prescribed aspirin or statin therapy as compared with patients undergoing usual care.

In a subsequent SCOT-HEART analysis (n = 1769), the volume (mm²) of low-attenuation plaque (<30 Hounsfield units) as quantified using semiautomated software provided the strongest predictive ability of incident MI [16].

●PROMISE randomly assigned 10,003 low-to-intermediate-risk symptomatic stable patients to CCTA or functional testing (67.5 percent nuclear stress testing) and assessed the composite outcome of death, MI, hospitalization for unstable angina, or major procedural complications [17]. After mean follow-up of 25 months, the following findings were noted:

•There was no difference in clinical outcomes between CCTA and functional testing with both groups experiencing low rates of total events (3 percent) during the trial. In the CCTA arm, almost all events occurred in patients with coronary atherosclerosis. In the functional testing group, 53 percent of events occurred in those with normal functional testing results.

•Among women, a positive compared with a negative CCTA was more strongly associated with subsequent clinical events (HR 5.9; 95% CI 3.3-10.4) than a positive versus a negative stress test (HR 2.3; 95% CI 1.2-4.3).

In subsequent analyses, CCTA findings (abnormal versus normal) were more predictive of events in patients under 65 years of age, with functional testing more accurate for event prediction in older patients [18].

As an alternative to coronary angiography

As an initial diagnostic test — CCTA may be an appropriate first diagnostic test for patients with stable chest pain who are at intermediate risk of CAD. Compared with invasive coronary angiography, CCTA may have fewer vascular complications. This is particularly relevant for women who have a higher risk of complications than men with invasive coronary angiography [19]. However, invasive angiography uses less iodinated contrast compared with CCTA and offers the opportunity for simultaneous intervention with diagnosis.

In a pragmatic randomized trial, 3561 patients with stable chest pain with intermediate probability of CAD were randomly assigned to CCTA or invasive angiography as their initial diagnostic test [20]. Patients were followed for 3.5 years for development of cardiovascular outcomes (including cardiovascular death, nonfatal MI, or nonfatal stroke) and secondary outcomes (procedure-related complications and angina). Cardiovascular events were similar in the CCTA versus invasive angiography groups (2.1 versus 3 percent; HR 0.70, 95% CI 0.46-1.07). Procedure-related complications occurred less frequently in the CCTA group (0.5 versus 1.9 percent; HR 0.26, 95% CI 0.13-0.55). Angina was reported in a similar proportion of patients during the last four weeks of the study (8.8 versus 7.5 percent; odds ratio 1.17, 95% CI 0.92-1.48)

Patients with nondiagnostic stress tests — CCTA can be considered as an alternative to invasive coronary angiography (ICA) in patients with equivocal or nondiagnostic noninvasive test results [21]. Patients for whom CCTA might be a reasonable option include those not interested in an invasive procedure, those at higher risk for complications of diagnostic coronary angiography (such as patients with severe peripheral artery disease), and those in whom the suspicion for CAD is not high (See "Complications of diagnostic cardiac catheterization".).

Large-scale observational registries suggest that approximately 50 percent of patients without known CAD who are referred for ICA following noninvasive functional stress testing are found to have no significant CAD on ICA [22]. CCTA, as a noninvasive coronary angiogram, has been studied as a method to reduce unnecessary referrals for ICA.

●In the PROMISE study, patients who underwent CCTA were significantly more likely to have an angiographically severe lesion on ICA as compared with functional stress tests (72.1 versus 47.5 percent) [17].

●In the CONSERVE trial, 1611 patients with stable symptoms and a nonurgent, guideline-endorsed indication (class II) for ICA (most based on stress imaging results) were randomized to CCTA or planned catheterization [23]. Patients with <50 percent stenosis on CCTA were recommended to cancel ICA and be treated conservatively, with ultimate management left up to their clinical providers. Performance of CCTA in CONSERVE resulted in a 78 percent reduction in planned ICA, and a 57 percent reduction in direct costs with no difference in clinical outcomes over one year of follow-up. The prevalence of obstructive CAD (≥50 percent) was 28 percent for CCTA and 39 percent for the direct referral to ICA arm.

CCTA should be considered as an alternative to ICA in patients with equivocal or nondiagnostic noninvasive test results [21].

Additional support for the use of CCTA comes from a meta-analysis of 13 prospective, randomized, clinical trials involving more than 20,000 symptomatic patients who were randomly assigned to CCTA or functional stress testing. Those receiving CCTA had a 29 percent relative lower rate of incident MI (risk ratio, 0.71; 95% CI, 0.53-0.96) during trials with <3 years of follow-up, a finding likely related to higher rates of statin and aspirin use in patients with plaque on CCTA imaging [24].

PATIENTS WITH ACUTE SYMPTOMS — Among patients with acute symptoms, the utility of CCTA depends on a patient risk and specific presentation.

Low suspicion of ACS in low-risk patients — Patients at low risk for acute coronary syndrome (ACS) according to highly sensitive troponin assays and guideline-endorsed clinical decision pathways may be safely discharged without testing [25]. These patients have a low likelihood of having ACS. (See "Stress testing in pre-discharge risk stratification of patients with non-ST elevation acute coronary syndrome", section on 'Who needs a stress test and when should it be performed' and "Evaluation of emergency department patients with chest pain at low or intermediate risk for acute coronary syndrome", section on 'Noninvasive evaluation'.)

Patients with low-risk NSTEACS — In patients with a low-risk ACS presentation (eg, absence of heart failure and refractory ischemic symptoms), clinical trials suggest CCTA may reduce the number of low-risk non-ST-elevation ACS (NSTEACS) patients who need invasive angiography.

In the multicenter RAPID-CCTA trial, 1748 patients in the United Kingdom with low-risk NSTEACS (ie, CAD, elevated troponin, and/or abnormal ECG) were randomly assigned to CCTA within 72 hours or standard care [26]. Patients had mean age of 62 years, 20 percent had prior MI, 20 percent had prior percutaneous coronary intervention or coronary artery bypass surgery, and 57 percent had elevated troponin values. Both groups had similar risks of death or MI at one year (5.8 versus 6.1 percent; hazard ratio [HR] 0.91, 95% CI 0.62-1.35). CCTA was associated with a lower rate of invasive coronary angiography (54.0 versus 60.8 percent; HR 0.81, 95% CI 0.72-0.92). There was no difference in coronary revascularization, use of drug treatment for ACS, or subsequent preventive treatments between the two groups.

Another small trial of 207 patients showed similar results with respect to cardiovascular outcomes [27]. This study also showed that patients assigned to CCTA had a similar incidence of the composite outcome of major adverse cardiovascular events or procedural complications compared with patients receiving initial invasive angiography (16 versus 23 percent).

Patients with intermediate-risk acute coronary syndrome — Along with stress testing, CCTA is an initial diagnostic testing option to exclude ACS in patients at intermediate risk for ACS when troponin and/or ECG studies are normal or inconclusive [28]

A meta-analysis of four randomized trials of nearly 1870 patients presenting to the emergency department with possible ACS compared the accuracy and efficacy of CCTA with usual care [29]. These trials found that the use of CCTA in the emergency department significantly reduced the time to diagnosis, time in the emergency department, and hospital admissions. One potential limitation of this analysis is that these clinical trials were performed prior to the widespread utilization of highly sensitive troponin assays

Still, the absence of significant CAD on CCTA has been shown to be highly accurate for excluding ACS and allows for safe early discharge of intermediate-risk patients without detectable troponin levels or concerning changes on ECG. In contrast, the presence of a stenosis ≥50 percent, especially when accompanied by high-risk plaque features, suggests a higher likelihood of ACS (image 1)

PATIENTS WITH PRIOR REVASCULARIZATION — CCTA is not typically recommended as a first-line test in patients with prior coronary artery revascularization. However, there may be clinical scenarios where it is useful to guide patient management.

For patients with prior percutaneous coronary intervention, stent material often results in "blooming" on CCTA images, a phenomenon that can obscure a portion of the coronary lumen within the stent and limit diagnostic accuracy. Patients with stents also often have extensive coronary calcification that can negatively impact diagnostic accuracy. As a result, CCTA is not routinely performed in patients with known intracoronary stents. However, high diagnostic accuracy can be expected in patients with larger diameter stents (≥3 mm) when excellent heart-rate control (ideally <60 bpm) at the time of imaging can be achieved. In a meta-analysis of 35 studies utilizing at least 64-slice CCTA (n = 2656 patients with 4131 stents), CCTA had a per-stent sensitivity of 90 percent (95% CI 0.85-0.94) and specificity of 0.94 (95% CI 0.91-0.96) [30]. The accuracy was highest for stents >3.0 mm, patients with heart rate <65 beats per minute, and those with thinner stent struts (<100 micrometers) as is seen in more contemporary stent platforms.

CCTA is highly accurate for the evaluation of coronary artery bypass graft patency and is considered an appropriate study when the patency of bypass graft conduits is the primary clinical question. However, CCTA has decreased diagnostic accuracy in native vessels in many patients with prior coronary artery bypass graft surgery, largely due to the high burden of calcified atherosclerosis, which limits its use in this population. The high diagnostic accuracy (>95 percent) of CCTA for the assessment of coronary artery bypass grafts is due to the relative lack of calcification and motion in bypass conduits. In a meta-analysis that included patients with 2482 coronary artery bypass grafts, the sensitivity and specificity for bypass graft stenosis >50 percent were 0.98 (95% CI 0.97-0.99) and 0.98 (95% CI 0.96-0.98),with an area under the curve of 0.99 regardless of type of bypass graft (venous versus arterial) [31].

USING THE RESULTS — Patients without or with low-risk CAD should be managed conservatively in accordance with current Society of Cardiovascular Computed Tomography Coronary Artery Disease Reporting and Data System recommendations [32]. Current guidelines now identify patients with CAD (obstructive and nonobstructive) identified on CCTA as having known CAD. Nonobstructive coronary atherosclerosis (<50 percent stenosis) on CCTA, especially when involving multiple segments or exhibiting high-risk plaque features, should prompt physicians and patients to maximally intensify cardiovascular prevention treatments and lifestyle changes. (See "Prevention of cardiovascular disease events in those with established disease (secondary prevention) or at very high risk".)

RECOMMENDATIONS OF OTHERS — Based on multiple randomized comparative effectiveness studies demonstrating its clinical utility in patients with acute or chronic coronary symptoms, CCTA is endorsed by some contemporary practice guidelines as a first-line test in symptomatic patients without established CAD and in those with equivocal or nondiagnostic functional test results [15,17,21,25,28,33,34]. (See "Prevention of cardiovascular disease events in those with established disease (secondary prevention) or at very high risk".)

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Multimodality cardiovascular imaging appropriate use criteria".)

SUMMARY AND RECOMMENDATIONS

●Indications – The major indications for coronary computed tomographic angiography (CCTA) by patient group are (image 1):

•Patients with stable symptoms – CCTA can be an initial test in patients with chronic (stable) symptoms concerning for ischemic heart disease (chronic coronary disease) who do not have previously established coronary artery disease (CAD). (See 'As an alternative to functional stress testing' above.)

In stable patients, CCTA may be an alternative to invasive coronary angiography as the initial diagnostic test; if the patient has nondiagnostic or equivocal stress test results and persistent symptoms and an uncertain diagnosis of CAD, a CCTA may be used. (See 'Patients with nondiagnostic stress tests' above.)

•Patients with possible acute coronary syndrome (ACS) – In patients with low-risk presentation of non-ST-elevation ACS (eg, absence of heart failure and refractory ischemic symptoms), when there is a clinician or patient desire to avoid invasive coronary angiography, or when the cause for troponin elevation is uncertain, CCTA may be used as an alternative to stress testing or invasive coronary angiography. (See 'Patients with low-risk NSTEACS' above.)

In patients at intermediate risk for ACS when troponin and/or electrocardiogram (ECG) studies are normal or inconclusive, CCTA, along with stress testing, is a first-line testing option to exclude ACS. (See 'Patients with intermediate-risk acute coronary syndrome' above.)

•Patients with prior revascularization – CCTA is not typically recommended as a first-line test in patients with prior coronary artery revascularization due to common occurrence of extensive coronary artery calcifications and stent artifacts. However, there may be clinical scenarios where it is useful to guide patient management. (See 'Patients with prior revascularization' above.)