Danish Study of Non-Invasive Diagnostic Testing in Coronary Artery Disease 3 (Dan-NICAD 3)

CCTA has become the preferred diagnostic modality for symptomatic patients with low to intermediate risk of CAD. Of the patients examined, CCTA exclude cardiovascular disease in 70-80% with an excellent negative predictive value of more than 95%. Having a low positive predictive value, however, CCTA often overestimates the severity of CAD, especially in patients with moderate to severe coronary calcification. Following CCTA, patients are hence unnecessarily tested using golden standard ICA-FFR. These ICAs often show no obstructive coronary stenosis and are therefore not followed by revascularization. The issues outlined raises the question of whether it is possible (1) to make a more precise risk stratification and consequently better selection of patients prior to CCTA and (2) to reduce the number of patients referred for unnecessary ICAs following CCTA.

In patients with suspicion of coronary stenosis detected by CCTA, current guidelines recommend verification of myocardial ischemia. Dan-NICAD 3 investigate the diagnostic accuracy of advanced non-invasive myocardial perfusion imaging tests; Rb PET and 15O-water PET. These examinations have shown a high diagnostic accuracy in symptomatic patients with high risk of ischemic heart disease. However, the diagnostic accuracy is not investigated in patients as follow-up after CCTA. In addition, microcirculation may impact the correlation between PET and ICA-FFR which this study will investigate further.

An alternative way to increase the diagnostic accuracy of CCTA and thus avoid unnecessary downstream testing using ICA is to utilize the ability to extract physiological information from the anatomical CCTA images. CT-FFR has in previous studies shown promising results. In addition, calculated estimation of microcirculatiory function is under development and this study will validated these algorithms. Furthermore, the prognostic value of CT-FFR is unknown and will be tested in the pooled cohort of Dan-NICAD 1, 2 and 3.

Obtained during ICA, quantitative flow ratio (QFR) is a novel wire-free approach for fast computation of FFR with potential to increase the global use of physiological lesion assessment. QFR is superior to traditional assessment of intermediate coronary lesions based on quantitative coronary analysis of ICA. However, disagreement between ICA-FFR and QFR has been identified in up to 20% of all measurements. QFR will be validated compared to PET and ICA-FFR.