LAUSR

Coronary computed tomography angiography-derived fractional flow reserve (FFR-CT) provides valuable information for decision-making regarding treatment strategies for coronary artery disease [1]. Although FFR-CT is a useful tool, we experienced a case demonstrating that caution should be exercised in its application. A 63-year-old man with a history of lupus nephritis and end-stage renal disease was referred to our hospital for decreased cardiac function. Coronary computed tomography (CT) showed severe stenosis in the mid-part of the left descending artery (LAD) and a slit-like lesion in the midpart of the right coronary artery (RCA) (Fig. 1A). The shortaxis images are shown in Supplementary Fig. S1. As the physiological significance of the RCA lesion was unclear, an FFR-CT was performed, and the values at 10.5 mm distal to the stenosis, which are reliable locations to assess lesion-specific ischemia, were 0.57 in the LAD and 0.84 in the RCA (Fig. 1B). The patient underwent invasive coronary angiography (CAG), and the LAD lesion was successfully treated. CAG showed a focal lesion in the mid-RCA. As a result, an invasive fractional flow reserve (FFR) was performed; the FFR values were 0.75 at 10.5 mm distal to the slit-like lesion and 0.74 at far distal RCA (Fig. 1C, D). For further ischemic evaluation, ammonia positron emission tomography (PET) was performed, which revealed decreased stress myocardial blood flow in the RCA territory. Although the FFR-CT value of the region of interest was 0.84, invasive FFR and ammonia PET showed evidence of myocardial ischemia; hence, PCI was performed for the RCA. Previously, Osawa et al. reported that a mismatch between FFR-CT and invasive FFR was commonly observed in bifurcation lesions with positive remodeling [2]. However, there have been no reports on its diagnostic accuracy for localized slit-like lesions. FFR-CT depends on the image quality of coronary CT, including spatial resolution. Consequently, it may not be possible to track the true lumen in localized lesions. This may be associated with an underestimation of the stenosis present. Therefore, particular attention should be paid when using FFR-CT for slit-like lesions.