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Whether coronary calcification process is correlated with plaque/media shrinkage (PS) remains unclear. The purpose of this study is to assess the relationship between calcification process and PS combining intravascular ultrasound (IVUS) and optical coherence tomography (OCT) from post-procedure to 5-year follow-up in patients treated with Bioresorbable Vascular Scaffolds (BVS).
In 15 patients, anatomic landmarks and radiopaque markers of BVS were used to match OCT and IVUS images for serial analysis. Plaque/media shrinkage (PS) was defined as relative decrease in plaque/media area>5%. The correlation between calcification process and PS was investigated.
Seventy-two grayscale-IVUS, echogenicity-IVUS and OCT pair-matched cross sections in- and out-scaffold segments were matched at baseline and follow-up (in total 432 images). In total, 35 out of the 72 cross sections showed PS, and 37 cross sections showed no PS (non-PS) at 5-year follow-up. PS showed inverse correlation with Δ calcium area on OCT (r=-0.65, p<0.001), Δ calcium arc (r=-0.63, p<0.001), Δ calcium length on OCT (r=-0.67, p<0.001), and Δ calcium arc on IVUS (r=-0.57, p<0.001) respectively. On echogenicity analysis, PS was associated with a decrease in hypoechogenicity (r=0.47, p<0.001). An increase in calcium area was inversely correlated to a decrease in hypoechogenicity (r=-0.40, p<0.001). Interestingly, the increase in calcium area was correlated to an increase in lumen area (r=0.37, p=0.002).
Calcification process is correlated counterintuitively with plaque/media shrinkage, hypoechogenic tissue decrease and lumen enlargement. Combining IVUS and OCT provides a unique method to assess the correlation between calcification process and plaque/media shrinkage.