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) which is the gold standard diagnostic technique. The presence of calcified components complicates the interpretation of the coronary stenosis severity. We present a case of discrepant assessment of coronary stenosis severity between CCTA/ FFRCT (significant obstructive CAD) and ICA (no apparent obstructive CAD). CCTA/FFRCT showed that the stenotic lesion was located in the middle segment of the left circumflex artery and was surrounded by plaque components. Proximal and distal portions of stenotic lesions consisted of 80.9% luminal volume, 0.2% low-attenuation plaque, 13.4% intermediate-attenuation plaque, and 5.5% calcified plaque, whereas stenotic lesion consisted of 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 lesion appearing as significant obstructive CAD on CCTA/FFRCT were likely overestimated due to the effects of extravascular calcified plaque. Advanced extravascular calcified plaque surrounding lesion may cause several artifacts (blooming and/or beam hardening artifacts) and/or vasodilator dysfunction (organic and/or functional), which may overestimate the severity of coronary stenosis with CCTA/FFRCT assessment.