The Use of Coronary Computed Tomography Angiography for Patients Presenting with Acute Coronary Syndrome

- Executive Summary

·   The clinician properly evaluates the patient before requesting CTA guided by the patient's history, clinical presentation, ECG, and initial biomarker assessment.  Good Practice Statement

·       The clinician should acquire ECG and review it for STEMI and Cardiac troponin should be measured as soon as possible. Good Practice Statement

·       The clinician should categorize patients into low-, intermediate- and high-risk according to risk stratification tools. The clinician should indicate the appropriate criteria for performing CCTA. Good Practice Statement

·       The clinician may request non-contrast coronary calcium scoring for asymptomatic individuals and intermediate-risk individuals (Framingham Risk Score 10%-20%) to document atherosclerotic cardiovascular disease risk stratification and guide preventive measures. Conditional recommendation

·       The clinician should not request non-contrast coronary calcium scoring for high-risk individuals, patients already receiving statin treatment or asymptomatic low-risk adults: Strong recommendation.

·       The radiologist should report non-contrast coronary calcium scoring  and categorize patients as no CAC (Agatston score 0), mild (1-100), moderate (101-400), or severe (>400). Strong recommendation

·       Clinicians should request CCTA as the first line test for evaluating patients with or without history of CAD who present with stable typical or atypical chest pain, or other symptoms that are thought to represent a possible anginal equivalent (e.g., dyspnea on exertion, jaw pain). Strong recommendation

·       Clinicians should request CCTA following a non-conclusive functional test to obtain more precision regarding diagnosis and prognosis if such information will influence subsequent patient management. Strong recommendation

·       Clinicians should request CCTA for patients at higher pretest risk for ACS, including patients with non-ST elevation myocardial infarction (NSTEMI) when the invasive strategy is not preferred (e.g., bleeding risk, vascular access issues, patient preference). Strong recommendation

·       Clinicians should not recommend CTA for low-risk patients or patients with high probability (cardiac catheterization is recommended).  Strong recommendation

·       Clinicians should request CTA for the assessment of coronary stents in symptomatic patients with coronary stents >3mm, with current generation drug-eluting stents that have struts <3mm, and with current generation drug-eluting stents that have struts <100µm. Strong recommendation

·       Clinicians may request CTA for the assessment of stents with smaller diameters (<3mm) as they are more challenging to assess, yet CTA may still be a reasonable test for assessing proximal, non-bifurcation thin strut stents that are <3mm. Conditional recommendation

·       Clinicians should request CCTA for the assessment patency of coronary artery bypass grafts in symptomatic patients. Strong recommendation

·       Clinicians should request CCTA for assessment of graft patency, anastomotic sites, and stenosis, in presurgical planning of redo bypass graft. Strong recommendation

·       Clinicians should request CCTA for assessment of coronary grafts and not for assessment of the native coronary arteries in patients with prior CABG as it is of limited value due to severe calcification of the native coronary artery. Strong recommendation

·       Clinicians may request CT-FFR for evaluation of lesion-specific physiology from a coronary CTA dataset using computational flow dynamic modeling and some hemodynamic assumptions, increasing the specificity of CCTA. Conditional recommendation

·       Clinicians may request CCTA for measuring extracellular volume fraction (ECV), yet the gold standard test for measuring ECV is Cardiac MRI. Conditional Recommendation

·       Clinicians may request CCTA for estimation of myocardial perfusion and viability as an alternative modality to Cardiac MR in patients with MRI contraindications. Conditional recommendation

·       Clinicians should educate the patient about the nature of the examination, its objectives, possible risks including radiation dose, their required cooperation, and the sensations they are likely to feel. Patients should be given a chance to request an alternative diagnostic strategy if they feel unable or unwilling to proceed.  Good Practice Statement

·       The radiologist should repeat the educational process after premedication, just before scanning, to ensure patients remember instructions on breath-holding and are prepared for the sensations likely to occur from nitroglycerin and contrast administration.  Good Practice Statement

·       The radiologist/radiographer should obtain CTA in minimum CT scanner specifications as 64-detector row or greater or dual-source scanners, axial resolution ≤0.5×0.5mm, Z-axis resolution ≤1mm and temporal resolution ≤250ms. Strong recommendation

·       The radiologist/radiographer should obtain Prospective ECG-triggering CCTA (the most commonly protocol) when the heart rate is regular and low (< 65 BPM). Strong recommendation;

·       The radiologist/radiographer should obtain Retrospective ECG gating for coronary artery evaluation when the heart rate is high and in cases of arrhythmia. Strong recommendation 

·       The radiologist/radiographer may obtain Retrospective ECG gating for ventricular functional assessment when other modalities are not available. Conditional recommendation

·       The radiologist is responsible for safety considerations of coronary CTA related to radiation exposure using the principle of As Low As Reasonably Achievable (ALARA). Strong recommendation

·       The radiologist/radiographer should perform CCTA with the minimum accepted radiation dose (approximately 3 mSv), by applying the radiation protection measures as ECG-based tube current modulation , a high-pitch helical scan , reducing the tube potential from 120 to 100 kVp, noise reduction methods such as iterative reconstruction and suitable Z-axis coverage . Strong recommendation

·       The radiologist/radiographer should perform CCTA after administration of intravenous iodinated water-soluble contrast media to ensure optimal vascular enhancement between 250 and 300HU in the ascending aorta. Strong recommendation

·       The radiologist is responsible for safety considerations of coronary CTA related to allergic reactions to iodinated contrast agents, and contrast-induced nephropathy. Strong recommendation

·       The radiologist should check the renal function tests before administration of the contrast media. If the eGFR value is greater than 30 the patient can receive IV iodinated contrast. If eGFR is less than or equal to 30 the case will need approval by the radiologist before IV contrast is used to minimize the risk of contrast-related AKI.  Strong recommendation

·       The radiologist should ensure the presence of patient safety equipment includings: advanced cardiovascular life support (ACLS) equipment in the patient preparation and scanner areas. Properly trained ACLS-certified nurses or similar qualified staff should supervise the premedication of patients as administration of beta blockers and nitrates. A rapid response team and/or an ACLS-certified physician should be readily available for prompt response to urgent or emergent complications. Strong recommendation

·       The radiologist should perform CCTA after preparing the patient by Beta-blocker (metoprolol) to control the heart rate for maximum image quality during low and regular heart rates. Strong recommendation

·       The radiologist should be familiar with the common contra-indications for beta-blockers such as heart block, hypotension, systolic dysfunction, poorly controlled asthma, severe aortic valve stenosis, severe bradycardia. Strong recommendation

·       The radiologist may perform CCTA after preparing the patient by giving oral (sublingual) nitroglycerin Conditional recommendations

·       The radiologist should be familiar with the common contraindications for nitroglycerin as erectile dysfunction medication (sildenafil, tadalafil, etc.) taken within the last 24-48 hr., increased intracranial pressure, right-sided myocardial infarction, severe anemia, known allergy or hypersensitivity . Conditional recommendations

·       The radiologist should process the axial source image in a dedicated workstation and get more advanced post-processing techniques to assess cardiac anatomy such as multiplanar reformats, curved multiplanar reformats, volume-rendered three-dimensional images, and cinematic rendering. If functional information is obtained, then segmentation of the ventricular cavities can be used to quantify ventricular volumes and systolic function. Good Practice Statement

·       The interpreting radiologist must be a physician adequately trained in cardiac CT as defined in recent training guidelines issued by the Society of Cardiovascular CT.  The interpreting radiologist should be promptly available in place or by phone for consultation about patient preparation and scan protocol. Good Practice Statement

·       The radiologist should report the radiological findings of CTA in one of the following formats: The Written Conventional Report or The Coronary Artery Disease-Reporting and Data System (CAD-RADS 2.0). The report should contain the relevant imaging findings, their interpretation, an overall summary/conclusion, and recommendations for further management. Good Practice Statement