A pragmatic, prospective, multi-center, open label, randomized controlled, superiority trial.

The study will compare clinical outcomes between invasive versus non-invasive approach as next diagnostic step in symptomatic patients with non-high risk obstructive coronary artery disease (CAD) on coronary computed tomography-angiography (CCTA).

CCTA has been emerged as useful diagnostic tool to evaluate CAD. Besides high diagnostic accuracy, CCTA has additional benefit of measuring the cumulative atherosclerotic burden and more accurately discriminating obstructive CAD with additional fractional flow reserve by CT (FFRCT), making it more predictive of a patient's prognosis. Recently, several randomized clinical trials have demonstrated the clinical utility of CCTA when compared with noninvasive stress test, which has been previously widely used as an initial assessment for stable chest pain, or invasive coronary angiography, which is the gold standard for diagnosing obstructive CAD.

On this background, CCTA, along with stress imaging test, is recommended as first step to diagnose obstructive CAD in patients with intermediate to high pretest probabilities with stable chest pain and is increasingly utilized. Although CCTA is increasingly used as initial assessment tool in these patients, there are insufficient studies to clearly establish the next step after obstructive CAD is confirmed in CCTA. Without high-risk features of CAD on CCTA, current guidelines suggest noninvasive stress imaging or FFRCT as class IIA recommendation. However, supporting evidence of these suggestions are mostly based on studies with low level of evidence. Furthermore, given the limited diagnostic performance of noninvasive stress test, concern remains whether it is safe to defer invasive coronary angiography based on the result from noninvasive stress test in patients with obstructive CAD on CCTA.

Therefore, this trial aims to compare clinical outcomes between invasive versus non-invasive approach as next diagnostic step in symptomatic patients with non-high risk obstructive CAD on CCTA.

Inclusion Criteria:

1. Subject age ≥19 years old
2. Patients with new or worsening chest pain syndrome, equivalent symptoms, or abnormal laboratory test findings (suspected ischemic changes in electrocardiography, regional wall motion abnormality in echocardiography, or coronary calcium score > 100) suspected for clinically significant CAD who are evaluated by CCTA
3. Any other clinical circumstance in which physician judged to proceed CCTA
4. Obstructive CAD in CCTA (≥50% diameter stenosis)
5. Subject who can verbally confirm understandings of risks, benefits, and treatment alternatives of receiving invasive approach and he/she or his/her legally authorized representative provides written informed consent prior to any study related procedure.

Exclusion Criteria:

1. Diagnosed or suspected acute coronary syndrome (ACS) requiring hospitalization or urgent or emergent testing (elevated cardiac troponin or CK-MB)
2. High risk CAD (left main stenosis ≥ 50%; anatomically significant 3-vessel disease with ≥70% stenosis)
3. Hemodynamically or clinically unstable condition (systolic BP < 90 mmHg, ventricular arrhythmias, or persistent resting chest pain in ischemic nature despite adequate therapy
4. Known CAD with previous MI, percutaneous coronary intervention (PCI), coronary artery bypass graft (CABG)
5. Known true anaphylaxis to contrast medium (not allergic reaction but anaphylactic shock)
6. Known significant congenital, severe valvular or cardiomyopathic (hypertrophic or dilated cardiomyopathy, or any other forms) process which could explain cardiac symptoms.
7. Severe left ventricular systolic dysfunction (ejection fraction <30%)
8. Intolerance to Aspirin, Clopidogrel, or Heparin.
9. Non-cardiac co-morbid conditions are present with life expectancy <2 year or that may result in protocol non-compliance (per site investigator's medical judgment)
10. Unwillingness or inability to comply with the procedures described in this protocol.

After publication of first manuscript and trial results, the de-identified data will be shared by permission of principle investigator, when asked

After publication of first manuscript and trial results, the de-identified data will be shared by permission of principle investigator, when asked

After publication of first manuscript and trial results, the de-identified data will be shared by permission of principle investigator, when asked

Clinical outcome assessment will be performed under blinded assessment about the allocated treatment group.