Chest pain represents a common reason for consultation to emergency room. This symptom can be explained by a broad spectrum of conditions, from benign musculoskeletal or esophageal pain to life-threatening disease such as aortic dissection, pulmonary embolism, and myocardial infarction.

There are already different diagnostic tools to quickly identify most dangerous diseases, for example electrocardiogram, blood samples with specific markers of cardiac injury, chest X-ray and echography. In case a doubt of disease is raised after the first clinical evaluation, it is possible to proceed with more complex, expensive and invasive examinations, namely a computed tomography (CT) scan or an invasive coronary angiography (ICA).

CT scan allows the diagnosis of various conditions such as pleural, pulmonary, pericardial and vascular disease such as pneumonia, pneumothorax, pleural and pericardial fluid, pulmonary embolism (PE), acute aortic dissection (AOD). In order to see the pulmonary, aortic and coronary arteries, a contrast injection is needed. Moreover, since the heart and the aortic root are continuously moving, specific technical measures to obtain good quality images are needed.

Recently, a new CT scan system has been developed. It allows to obtain good quality images of the heart and aortic root using an estimated heart rhythm, without ECG-gating. This allows to perform a CT scan of the heart in a reduced amount of time, and without need for controlling heart rate. Moreover, it is possible to obtain information on both aortic, coronary, and pulmonary artery with the same contrast injection. This may be of great interest in the context of patients presenting at the emergency room with chest pain and with a suspicion of pulmonary embolism, myocardial infarction, or aortic dissection, since with a single fast exam it is possible to rule out all these conditions.

Coronary arteries are very small vessels, and the accuracy of this new technique in identifying a significant obstruction is still to be proved. At present, patients with chest pain and a suspicion of myocardial infarction undergo an invasive coronary angiography. If this new tool proves to be reliable, it will be possible to reduce the number of useless invasive examination in patients in which the presence of coronary artery disease (CAD) is ruled-out. In addition, the CT scan can help quickly and effectively plan treatment when worrying abnormalities are detected in the coronary arteries that are associated with a higher risk.

Therefore, this clinical trial (further on referred to as "trial") will evaluate the investigational medicinal product (IMP), ECG-less Revolution Apex Elite system (GE Healthcare, Waukesha, WI -USA) for the diagnosis of coronary artery disease. The purpose of this trial is to learn about: the accuracy of this new CT system compared to the gold standard invasive coronary angiography in diagnosing coronary artery disease. The number of patients receiving an alternative diagnosis such as pulmonary embolism, aortic dissection, pulmonary, pleural or pericardial disease will be evaluated. Finally, the prognostic predictive value of the CT compared with ICA, in predicting myocardial infarction, coronary revascularization, and cardiac death at a follow-up of 18 months will be assessed. Patient will undergo a computer tomography examination with this new technique, evaluating both pulmonary, aortic, and coronary arteries. Then, as indicated by current guidelines, they will undergo an invasive coronary angiography.

1. Study Rationale The aim is to investigate the potential role of CCTA in patients presenting to the emergency room with thoracic pain and elevated troponins. Using a single contrast bolus and a lower radiation dose, the new ECG-less CCTA could help exclude life-threatening conditions such as PE and AAD, while providing valuable information about the coronary arteries. Patients with normal coronary arteries could be safely discharged without invasive examinations, thus avoiding pro-cedural risks and optimizing both time and resources for medical institutions. However, since the diagnostic role of ECG-less CCTA in ACS has not yet been demonstrated, current guidelines and best practices will be followed in the management of enrolled patients. Decisions regard-ing PCI will be based on coronary angiography, coronary physiology, and intravascular imaging, as currently recommended by international guidelines.

   The negative and positive predictive value of the ECG-less CCTA compared to the standard of care (ICA) in patients clinically considered at risk for NSTEMI will be assessed. Additionally, the prognostic predictive value of CCTA in this clinical context, in compari-son to ICA will be evaluated. If the prognostic value of CCTA is similar to that of ICA, it will be possible to reduce the use of invasive procedures in favor of non-invasive exams, thereby saving time, contrast, and radia-tion dose for the patient.

2. Primary Objectives

   • Evaluate the diagnostic accuracy of the non-ECG-gated CCTA in diagnosing CAD compared to the gold standard (ICA) in terms of negative and positive predictive value, sensitivity, and specificity.
   • Assess the accuracy in excluding high-risk CAD such as LM, proximal LAD and multivessel disease.
   • Describe the proportion of patients diagnosed as NSTE-ACS according to the ESC guidelines who will receive an alternative diagnosis thanks to the CCTA, in particular PE and AAD.

3. Secondary Objectives

   • Assess the capacity of the non-ECG-gated CCTA in predicting the mid and long-term out-come compared to the ICA.
   • Investigate the possibility of applying the tool of FFR-CT calculation at images obtained by means of non-ECG-gated CCTA.

4. Study Design Prospective, single-center, double-blinded study.

5. Study Population Patients presenting at the ER with acute chest pain and either a diagnosis of NSTEMI at "high-risk" according to the 2023 ESC guidelines on ACS or a troponin value in the "observe pathway" and a high clinical suspicion of MI.

6. Study protocol Patients presenting with acute chest pain and elevated troponin either in the "rule-in" or "ob-serve pathway" according to ESC guidelines on ACS will be offered to participate to this study evaluating the role of non-ECG-gated CTA in patients with NSTEMI. After giving the consent, patients will be sent for non-ECG-gated CTA for the evaluation of coronary arteries, ascendent aorta and pulmonary arteries. After the CT and within 24 hours, patients will undergo ICA. Both the patient and the interventional cardiologist will be blinded to the result of the CT, the only exception being the diagnosis of a disease other than CAD which is considered responsible for the clinical presentation. The analysis of the CT images will be repeated in a core lab by the consensus of two radiologist with a wide experience in CCTA. Readers will be blinded to clini-cal data and ICA results.

ECG-less CT Patients will undergo scanning with a Revolution Apex Elite system (GE Healthcare, WI, USA), using hyperdrive pulmonary CT angiography (523mm/s with 0.28s/rotation gantry speed). Images will be acquired using the ECG-less Cardiac software (GE Healthcare, WI, USA), without the need for patient-attached ECG leads. The system uses a wide detector coverage of 160mm to provide full heart coverage and a fast gantry speed of 0.23 seconds per rotation to perform imaging in a single cardiac cycle. An estimation of the heart rhythm must be provided, which is always available since emergency patients are already monitored with finger pulse oximeter. Based on the heart rhythm the scanner simulates an ECG signal. This simulated ECG signal provides virtual gating of the scan. Acquisition can be performed over one full heart cycle, three-quarters, or half cycle, depending on heart rate. Advanced software tools including SmartPhase (automated phase selection) and SnapShot Freeze 2 (optimized volume registration) will be used to enhance image quality and correct for motion. After a short delay of 5-12 sec, allowing contrast to pass from the pulmonary circulation into the aorta and coronary arteries, a coronary CT angiography will be performed using the same contrast bolus. No additional contrast will be administered for cardiac imaging. No intravenous β-blocker or sublingual nitroglycerin will be administered. The total added exam time (including heart rhythm assessment, scan preparation, delay, and the acquisition itself) is estimated at 1-2 minutes.

Invasive coronary angiography and revascularization Patients will undergo an ICA following local and international best practices. The UZ Brussel in-terventional department is a high-volume center with experience in complex percutaneous coronary interventions (PCI). The procedures will be performed with trans-radial access when feasible. Any attention will be paid to reduce the total amount of contrast.

In case of moderate stenosis, the operator will use the invasive FFR to indicate PCI. The use of intravascular imaging is encouraged.

In case of significant CAD, patients will be treated with PCI following the ESC guidelines. The choice of interventional technique and DAPT regimen is left to the operator and the treating cardiologist.

Complete revascularization will be pursued either during the same hospitalization or within one month.

Inclusion Criteria:

• Age ≥ 30 years old

• Admission at the ER with acute chest pain and at least one of the follow-ing:

  1. ECG abnormality;
  2. positive rule-in criteria according to the ESC guidelines (hs-cTnT ≥ 52 in at least one assay or 1h ∆ ≥ 5);
  3. troponine value in the "observe pathway" (hs-cTnT ≥ 12 in at least one assay or 1h ∆ ≥ 3) AND a high clinical suspicion of MI.

Exclusion Criteria:

• Indication for urgent ICA (ST-elevation, hemodynamic or electric instabil-ity, refractory chest pain, mechanical complications)
• eGFR < 30 ml/min
• Previous coronary stenting
• Previous CABG
• Recent ACS within 6 months
• Known severely reduced ejection fraction (EF < 30%)
• Contrast allergy
• Inability to provide informed consent
• Limited life expectancy < 2 years due to non-cardiac conditions
• Pregnant and breast-feeding women
• Known congenital heart disease
• Atrial fibrillation