Abstract Background It has been reported that patients with stent underexpansions are at high risk for adverse outcomes, including stent thromboses and in-stent restenoses, especially with calcified lesions. Although there have been several reports on the predictors of stent underexpansions in calcified lesions, little is known about the predictors of stent underexpansions in severely calcified lesions after suitable debulking using rotational atherectomy (RA) or orbital atherectomy (OA). Purpose We investigated predictors of stent underexpansion in severely calcified lesions after debulking using optical coherence tomography (OCT)-guided RA or OA. Methods The DIRO trial was a single-center, prospective, and randomized trial, which included patients with severely calcified lesions scheduled to undergo OCT-guided RA or OA in our institution between August 2019 and October 2021. Using the DIRO trial data, we compared the various parameters including the calcium and lipid parameters (lipid-rich plaque, thin cap fibroatheroma TCFA, maximum lipid arc, mean lipid arc, lipid length, and lipid volume index) between the adequate stent-expansion (ASE) group and under stent-expansion (USE) group. To find predictors of stent underexpansoin, multivariable analysis was performed using the significant factors from the univariable analysis. We also evaluated adverse events 8 months after the procedure. Results The USE group consisted of 57 patients (65.5%). After suitable debulking of severely calcified lesions using RA or OA, the calcium parameters did not correlate with stent underexpansions, but the lipid parameters, maximum lipid arc ≥224 °, and TCFA, significantly and independently correlated with it (Table). Approximately 45% of severely calcified lesions included partially lipid-rich lesions. Adverse events occurred more frequently in the USE group than ASE group. The possible mechanism of stent underexpansion in the lesions with both lipid and calcified plaque is as follows: If the lesion exhibited the same hardness throughout, the balloon pressure would act the same for the whole lesion, but if the lesion had both hard and soft parts (e.g., calcified part and lipid-rich part), a greater balloon expansion would occur in the soft part than in the hard part, and different expansions within the stent could occur. The border of the soft and hard parts especially may have been the most affected and could become deformed, which partially would induce a stent underexpansion (Figure). Conclusions To avoid stent underexpansions in severely calcified lesions after suitable debulking using RA or OA, the impact of calcium parameters may be weak, but the maximum lipid arc and TCFA are important.
Tanouchi et al. (Sat,) studied this question.