Rationale: Patients with stable chest pain enter a diagnostic pathway where Coronary Computed Tomography Angiography (CCTA) is often the first line non-invasive test to detect coronary stenosis. An anatomically significant (≥ 50% luminal narrowing) stenosis on CCTA does however not always cause cardiac ischemia (i.e. hemodynamically significant stenosis). CCTA is often followed by invasive coronary angiography (ICA) to assess the hemodynamic significance of the stenosis which is the key determinant to decide on treatment (revascularization by coronary stenting or surgery). CCTA has a very high negative predictive value but the positive predictive value is moderate. Hence, anatomically significant stenoses on CCTA often turn out not to be hemodynamically significant on ICA. Fractional Flow Reserve from coronary computed tomography (FFRct) analysis is a new non-invasive technique that uses the CCTA images as a basis for complex software based calculations and modelling to provide additional functional information based on the anatomical CCTA images. Thus, FFRct is a totally non-invasive method. Adding the FFRct analysis to the anatomical assessment of CCTA is expected to reduce the number of patients being referred to ICA where no signs of hemodynamically significant stenosis are found on ICA.

In the Netherlands, annually 180.000 new patients present with stable chest pain - the most common symptom of coronary artery disease (CAD) [1]. Stable chest pain has a 1.5% 1-year mortality and 0.7% incidence of myocardial infarction [2]. The "Kennisagenda" of the Dutch Societies of Radiology and Cardiology include CAD diagnosis as a top 10 priority.

Patients with stable chest pain enter a diagnostic pathway to detect or exclude significant coronary stenosis which is defined as > 50% luminal narrowing.

The "Verbetersignalement pijn op de borst" published by the Zorginstituut, advocates that the diagnosis should be based on a single non-invasive first line test.

Based on the National Institute for Health and Excellence (NICE) and European Society of Cardiology (ESC) guidelines, the Coronary Computed Tomography Angiography (CCTA) is a good option as the first line test in low to intermediate risk patients.

CCTA is the most sensitive non-invasive technique available, but only provides anatomical information. CCTA has an excellent negative predictive value (99%), therefore CCTA can accurately rule out CAD. However the positive predictive value is moderate (64%). Hence, anatomically significant stenoses on CCTA often turn out not to be hemodynamically significant on ICA .

Patients with significant anatomical stenosis on CCTA are often referred for invasive coronary angiography (ICA) to confirm the presence of a stenosis and subsequent revascularization of hemodynamically significant stenoses. To determine the latter, invasive fractional flow reserve (FFR) measurements can be performed during ICA. In FFR, the pressure drop across an anatomical stenosis is measured, yielding a numerical value between 0 and 1, with 1 being normal and 0.80 considered a significant stenosis.

As with all invasive procedures, ICA is associated with morbidity, mortality, patient discomfort, time and costs. Due to the moderate specificity of CCTA, many patients referred for ICA turn out to not have hemodynamically significant coronary stenosis (28-41%) in Dutch populations.

To reduce the percentage of patients referred for ICA without significant CAD, the FFRct can be useful. FFRct is a non-invasive method that uses the already acquired CCTA images to calculate coronary FFR values as they would be expected if measured invasively.

Based on data of two randomised trials conducted in the Netherlands, around 20% of patients with chest pain referred for CCTA have at least 50% anatomical coronary stenosis on CCTA . Prior FFRct studies involved populations of different countries, with different risk and work-up There are no prospective data on the real-world use of FFRct in the Dutch population of stable chest pain patients with stenosis on CCTA. The effect of FFRct in reducing unnecessary ICA or other non-invasive tests compared to CCTA alone in the Dutch health care situation is unknown. Evidence in the specific Dutch situation and population is needed to evaluate the impact and cost-effectiveness in the Dutch healthcare system.

The FUSION study is a randomized controlled trial which will investigate the impact of adding the FFRct analysis in the diagnostic pathway of stable chest pain on the rate of unnecessary ICA's.

Inclusion Criteria:

• Age ≥ 18 years
• Stable chest pain and the patient underwent CCTA which demonstrated ≥50% but less than 90% stenosis in any major epicardial vessel with a diameter ≥ 2 mm.

Exclusion Criteria:

• Inability to provide informed consent
• Unstable angina according to ESC guidelines
• Unstable clinical status
• Expected inability to complete follow-up and comply with follow-up aspects of the protocol
• History of coronary revascularisation
• Non-invasive or invasive diagnostic testing for CAD within the past 12 months (with the exception of exercise ECG)
• Unsuitable for revascularisation if required (for example due to comorbidities or anatomical features)
• Poor CT quality with expected inability to perform FFRct analysis