Diagnostic one-stop-shop in suspected coronary artery disease gets closer. Coronary computed tomography angiography based fractional flow reserve

Current diagnostics of suspected coronary artery disease (CAD) significantly relies on coronary angiography. The traditional, invasive diagnostics is recommended in patients with high, but non-invasive coronary computed tomography angiography (CTA) in patients with intermediate pre-test probability of significant CAD [1]. Basically, the angiography is designed to reflect the anatomical status of the coronary artery lumen, especially concentrating on the presence and the degree of stenosis. Both anatomic methods of examination suffer from poor correlation with outcomes of functional testing for ischemia. Notably, invasive angiography is not superior in this respect to coronary CTA [2]. There is a consensus, reflected in the ESC guidelines, that stenoses above 90% are significant, i.e. allegedly cause ischemia, and those less than 50% are harmless. What lies between these thresholds, however, is called intermediate stenosis, and usually requires further functional evaluation prior to the potential intervention.
Given the indications for coronary CTA, relatively frequent diagnosis of intermediate coronary stenosis (50–90%) in a patient with intermediate probability of CAD, borderline symptoms or an equivocal functional test is particularly perplexing. On the other hand, patients with indications for invasive angiography should have typical symptoms, or confirmed ischemia, which limits the number of functionally ambiguous stenoses in this group. The lack of conclusive diagnosis in a significant number of patients with intermediate stenosis poses a serious limitation of coronary CTA, as it leads to further functional testing. Therefore, any additional information derived from the CTA datasets, which would confidently limit the grey zone of borderline stenoses, is desirable.
A gold standard for management of intermediate coronary stenoses in the catheterization laboratory comprises measurement of fractional flow reserve (FFR). Its appeal is based on diagnostic straightforwardness and perceived conceptual simplicity, providing a quick and concrete solution to the problem. The unequivocal threshold of ≤ 0.80 confirmed in randomized trials and endorsed by guidelines provides assurance to the operators. The first mention about potential application of the FFR concept to coronary CTA datasets can be traced back to the beginning of the twenty-first century. The main methodological barriers for simulation of the trans-lesional gradient was a difficulty...


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