In recent years invasive coronary angiography (ICA) has been supplemented by the measurement of fractional flow reserve (FFR) to determine whether a coronary stenosis impairs delivery of oxygen to the heart. However this technique has not previously been available through non-invasive methods. While the use of coronary computed tomography (CT) calcium scoring and angiography has been increasing, it remains a limitation of the technique that the haemodynamic significance of any lesions seen cannot be assessed.

The DeFACTO (Determination of Fractional Flow Reserve by Anatomic Computed Tomographic Angiography) study determined whether a noninvasive calculation of FFR derived from computational fluid dynamics (FFRCT) could diagnose haemodynamically significant coronary artery disease, using invasive FFR as the reference standard.

The study involved 252 stable patients with known or suspected coronary disease from 17 centers in 5 countries, all of whom under went CT, coronary angiography with FFR measurement, and FFRCT. The accuracy of FFRCT and CT for the diagnosis of ischaemia was compared to invasive FFR as the reference standard. The main outcome measure was whether FFRCT plus CT could improve the per-patient diagnostic accuracy.

137 participants in the study (54.4%) had an abnormal FFR. Although the study did not achieve its prespecified primary outcome goal, compared with obstructive coronary disease diagnosed by CT alone, FFRCT was associated with improved discrimination (P<.001).

Conclusions:

The use of noninvasive FFRCT plus CT was associated with improved diagnostic accuracy vs CT alone for the diagnosis of haemodynamically significant coronary artery disease.

• Min JK, Leipsic J, Pencina MJ et al. Diagnostic Accuracy of Fractional Flow Reserve From Anatomic CT Angiography. JAMA 2012;308:doi:10.1001/2012.jama.11274.