Today, I review, link to, and excerpt from 2022 use of coronary computed tomographic angiography for patients presenting with acute chest pain to the emergency department: An expert consensus document of the Society of cardiovascular computed tomography (SCCT). Endorsed by the American College of Radiology (ACR) and North American Society for cardiovascular Imaging (NASCI) [PubMed Abstract] [Full-Text HTML] [Full-Text PDF]. J Cardiovasc Comput Tomogr. 2023 Mar-Apr;17(2):146-163. doi: 10.1016/j.jcct.2022.09.003. Epub 2022 Sep 29.
All that follows is from the above resource.
3.1 Evaluating pre-test likelihood of ACS
Patient selection is primarily guided by the patient’s history, clinical presentation, ECG and initial biomarker assessment (Fig. 1). Clinically appropriate patients should have reasonable clinical suspicion of ACS. A careful history and physical examination should precede any cardiac testing, to exclude alternative non-coronary diagnoses and to help define the pre-test likelihood of ACS. ECG should be acquired and reviewed for STEMI within 10 minutes of arrival to the ED. Cardiac troponin or hs-cTn should be measured as soon as possible. High sensitivity troponin assays are preferred for establishing a diagnosis of acute myocardial infarction due to their improved performance over contemporary cTn.31,32 Clinicians should be familiar with 99th percentile upper reference limit for the hs-cTn or conventional cTn assay used at their local institution.
Risk stratification tools for ACS can help categorize patients into low-, intermediate- and high-risk. Commonly used tools in Emergency Medicine include the HEART pathway,77 EDACS,78 and ADAPT79 (based on the TIMI risk score), which incorporate the results of troponin testing and have established value in clinical practice (Table 1). Risk stratification should be performed in parallel with serial troponin measurements to exclude myocardial injury. For hs-cTn assays, baseline sample collection should be obtained followed by a repeat measurement in 1–3 hours, unless the baseline test is below the limit of detection in a low-risk patient. . For conventional troponin assays, repeat sample collections are generally advised between 3 and 6 hours (see Table 2a).
STEMI should be managed according to recent guidelines,80 with prompt ICA as the only appropriate imaging study. Patients with documented NSTEMI should also follow guidelines-directed management,81 with consideration of early coronary CTA in limited scenarios.
3.2 Clinical considerations
Clinical scenarios are provided in Table 2 to illustrate a sample diagnostic pathway that integrates appropriate coronary CTA utilization for patients with suspected or definite ACS. Institutional practices will vary, and all management decisions should be tailored to individual patients based on clinical judgment. In selecting the optimal diagnostic test for a patient, it is important to recognize that coronary CTA provides information about coronary atherosclerosis burden, plaque morphology, and stenosis severity. CT may also permit evaluation of regional and global ventricular function and wall motion at low radiation doses, which adds incremental value for the diagnosis of ACS beyond evaluation of coronary anatomy.82 By contrast, functional testing (including ECG-only stress testing and stress testing with the use of imaging such as echocardiography or SPECT MPI) evaluates for regional myocardial ischemia due to inadequate coronary flow reserve. There are advantages and disadvantages to each approach.
4 Clinical scenarios/diagnostic pathway
Patient scenarios are provided to illustrate a sample diagnostic pathway that integrates appropriate coronary CTA utilization with standard care for patients with suspected or definite ACS (Table 2a). Institutional practice will vary and all management decisions should be individualized for patients based on physicians’ clinical judgment. The appropriateness of an imaging examination is measured as “usually appropriate” (green score), “may be appropriate” (yellow score), and “usually not appropriate” (red score). More granular appropriateness such as a 1 (lowest appropriateness) – 9 (highest appropriateness) ranking is not considered. For example, a patient who presents with STEMI by ECG criteria would rarely undergo combined coronary CTA and CTP in lieu of going to the cardiac catheterization lab (Table 2b). Instead of numerically assigning a score of 1, the imaging study for this clinical scenario is designated simply as “red”.Prior to test selection, recent chest CT examinations should be reviewed for an estimate of CAC burden. Prior coronary angiograms (both CTA and invasive angiography) should also be reviewed for evidence of CAD, and prior stress test results reviewed for evidence of ischemia, to refine pre-test probability and guide appropriate test selection.
4.1 Patients with No known CAD
1.STEMI: In patients with documented STEMI, urgent cardiac catheterization is proven to be beneficial, with door-to-balloon time less than 90 minutes.80 CT imaging should not delay “door-to-balloon” time. As such, all CT imaging is considered inappropriate, categorized as “usually not appropriate” and designated a “red” score. While not formally considered in Table 2a, portable chest radiography may be appropriate (yellow) to exclude secondary pathology that will be treated before or during catheterization, such as pneumothorax or abnormal line placement.812.Leading Diagnosis NSTEMI: This scenario includes patients with 1) ST changes on ECG that are suggestive of myocardial ischemia, but without ST-elevation; and 2) elevated cTn or hs-cTn. The favored management is invasive coronary angiography within 24 hours.81 Coronary CTA is seldom indicated first-line in the setting of NSTEMI to determine whether invasive evaluation is appropriate. Recent evidence suggests a possible role to rapidly exclude obstructive CAD when the pretest likelihood is low, or when there is desire to avoid unnecessary invasive coronary angiography (i.e., during the Covid-19 pandemic).18,35,37,84,853.High Risk for ACS: This scenario includes patients at high pretest risk for CAD, but with no definite evidence of ACS by ECG and troponins. In patients considered high-risk by risk stratification tools (i.e., HEART score >6, TIMI risk score >4 (Table 1), but with normal or nonischemic ECG, and normal or equivocal troponins, coronary CTA may be appropriate, particularly at centers with local expertise and established high-quality coronary CTA programs. Alternatively, high-risk patients may be considered for functional testing or invasive angiography. Coronary CTA offers an opportunity to safely defer invasive angiography in patients with normal or nonobstructive CAD, which can represent up to 50% of this patient population.28,86 Among patients found to have nonobstructive disease, early recognition with coronary CTA offers the opportunity to optimize preventive therapy and medical management prior to ED discharge.874.Low-to-Intermediate Risk for ACS: Coronary CTA is most effective in patients with a low-to-intermediate pretest likelihood of ACS. This includes patients with normal or nonischemic ECG changes, and normal or equivocal baseline cTn, or baseline hs-cTn below the 99th percentile. Using risk stratification tools, low-to-intermediate pretest risk is defined by HEART scores 1–6, and TIMI risk scores 1–4. This category also includes patients with inadequate or mildly abnormal functional testing during the index ED visit or within the previous 1 year.The majority of randomized-controlled trial evidence supporting coronary CTA in the ED enrolled patients within the low-to-intermediate risk category risk.5,6,8,9,12,24 in this group of patients coronary CTA is most efficient; approximately 5–15% of patients will have obstructive CAD warranting further evaluation with invasive coronary angiography, while the majority of patients can be safely discharged from the ED with normal or nonobstructive disease.
5.Very Low Risk for ACS: This category refers to patients who are considered low-risk by risk stratification tools, with normal or nonischemic ECG, and normal baseline hs-cTn. Within this patient population, the 30-day risk of MACE is less than 1%.88 For many of these patients, further diagnostic testing for CAD is not necessary as the yield would likely be low. However, coronary CTA may be appropriate in some very low risk patients to confidently exclude CAD and provide risk stratification; for example, patients with recurrent ED visits for chest pain who desire further testing to confidently rule-out CAD. Testing during the index ED visit could expedite a more thorough coronary evaluation, including the presence of non-obstructive plaque and also evaluate for other potential sources of chest pain. Further, coronary CTA is considered appropriate in the 2015 multi-society appropriate use criteria for ED cardiac imaging in very low risk patients, defined by TIMI risk score zero and negative early hs-cTn.65 Shared decision making cannot be overemphasized in this patient population, so patients are well informed of the potential risks and benefits of additional testing.
