Red thrombus-like appearance of protruding calcification into the lumen of the coronary artery by optical coherence tomography

Calcification is usually identified by a well-delineated, low back-scattering heterogeneous region without signal attenuation on optical coherence tomography (OCT), whereas red-thrombus is characterized as a high-backscattering protrusion with attenuation. Although the visualization of intense dorsal shadowing must be interpreted as red-thrombus according to classical OCT diagnostic criteria, thick calcification ( 1.5 mm) may also generate intense posterior shadowing, due to inability of near-infrared light penetration. In this case, OCT images suggested redthrombus while MSCT/IVUS findings demonstrated calcification (Figure 1). Nodular calcification should be taken into account to prevent stent under-expansion or coronary perforation, even in cases with redthrombus on OCT.