Impact of Advanced Extravascular Calcified Plaque on the Assessment of Coronary Stenosis Severity

Coronary computed tomography angiography (CCTA) and CT-derived fractional flow reserve (FFRCT) provide high diagnostic accuracy for coronary artery disease (CAD), consistent with invasive coronary angiography (ICA), the gold standard diagnostic technique. The presence of calcified components, however, complicates the interpretation of coronary stenosis severity. We present a case where there was a discrepant assessment of coronary stenosis severity between CCTA/FFRCT (indicating significant obstructive CAD) and ICA (showing no apparent obstructive CAD). CCTA/FFRCT revealed that the stenotic lesion, located in the middle segment of the left circumflex artery, was surrounded by plaque components. The proximal and distal portions of the stenotic lesion consisted of 80.9% luminal volume, 0.2% low-attenuation plaque, 13.4% intermediate-attenuation plaque, and 5.5% calcified plaque. In contrast, the stenotic lesion itself contained 50.0% luminal volume, 0.3% low-attenuation plaque, 26.7% intermediate-attenuation plaque, and 22.9% calcified plaque. Invasive coronary angiography showed no apparent obstructive CAD, implying that the lesions appearing as significant obstructive CAD on CCTA/FFRCT were likely overestimated due to the effects of extravascular calcified plaque. Advanced extravascular calcified plaque surrounding the lesion may cause several artifacts (such as blooming and/or beam hardening artifacts) and/or vasodilator dysfunction (either organic and/or functional), potentially leading to an overestimation of the severity of coronary stenosis in CCTA/FFRCT assessments.