We thank our colleagues Görich and Buß for pointing out the issue of computed tomography angiography (CTA) of coronary arteries and the possibility to estimate FFR (fractional flow reserve) by simulations based on CT datasets (1, 2). Indeed, the largest study published to date showed that, in comparative trials, FFA-CT scores with respect to a threshold of 0.80 were 81% consistent with invasively measured FFR for assessment of coronary lesions (1).
Incidentally, simulation of FFR is also successful on the basis of invasive coronary angiogram with similar software solutions (“FFR angio”) (3). However, these methods are not widespread and at least in part still in the development stage. In addition, patients enrolled in the comparative studies are selected, and prospective randomized controlled trials that demonstrate prognostic significance, as for invasive FFR, do not exist for either FFR-CT or FFR-angio.
These are certainly procedures whose further development, validation, and performance in clinical use should be followed with interest. However, it should be noted that FFR-CT in particular would occupy a slightly different place in the spectrum of cardiac examination procedures than coronary angiography using pressure wire measurement. CT angiography is already an examination procedure that is usually used early in the diagnostic sequence, especially in patients with a low-to-moderate pre-test probability of coronary heart disease. Invasive coronary artery diagnostics with the optional addition of pressure wire measurement are performed in non-invasive pathological examinations and for patients with high probability of pre-testing as well as for those with a clinical picture of an acute coronary syndrome. In this respect, the—potential—areas of application overlap only partially.
On Behalf of the Authors
Dr. med. Monique Tröbs
Universitätsklinikum Erlangen, Germany
Department of Medicine 2—Cardiology and Angiology
Conflict of interest statement
Dr. Tröbs has received consultant honoraria from Abbott Vascular.
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