Assessment of the Functional Significance of Coronary Stenoses Using Coronary CT-angiography and Non-invasive Fractional Flow Reserve Measurement.

Coronary Computed Tomography Angiography (cCTA) is a non-invasive imaging modality that provides high-resolution images of coronary lesions. cCTA shows good diagnostic performance in detecting or excluding coronary artery stenoses, but the severity of the lesions is often overestimated. With invasive coronary angiography (ICA) the hemodynamic consequences of obstructive lesions can be estimated using Fractional Flow Reserve measurement (FFR). There is a good correlation between FFR and non-invasive ischemia tests such as stress echocardiography, exercise tolerance test or Single Photon Emission Computed Tomography (SPECT). Measurement of FFR during ICA represents the "gold standard" for assessment of the hemodynamic significance of coronary artery lesions. The major disadvantage of FFR is that it is an invasive measurement, and consequently there is a risk of complications. Recently a non-invasive method to determine FFR has been developed (FFRct). FFRct is performed using standard cCTA images, and is based on computational fluid dynamics. The hemodynamic consequence of stenotic lesions is determined at rest and under simulated condition of hyperemia.

Acute myocardial infarction (MI) is divided into STEMI and NSTEMI on the basis of ECG changes. In Denmark patients with STEMI are treated with primary percutaneous intervention (PPCI) of the culprit lesion. Any non-culprit lesions are typically assessed with FFR after 3-4 weeks.

Even though the rate of complications during ICA with FFR is low, these complications can be severe. Also the procedure is quite resource demanding. Thus it would be desirable if it in these patients could be non-invasively evaluated whether further revascularisation is indicated.