Efficiency of orbital atherectomy for eccentric calcium in bending vessels: in-vitro vessel models

Abstract

Abstract Background/Introduction The mode of action of orbital atherectomy (OA) consists of a fast elliptical rotation of the crown, allowing for focal treatment with slow forward and backward movements. However, reports on the efficiency of OA for eccentric calcium in bending vessels are limited. Purpose This study aimed to clarify the mechanism of action of the crown and elucidate the anatomical condition for an efficient OA on eccentric calcium in bending lesions, via in vitro experimental models. Methods In total, 40 in vitro stenotic vessel models with eccentric calcium were developed; five models with a combination of two calcium positions (inner or outer side bending), two curvature radiuses (R, 10 or 20 mm), and two bending angles (A, 100º or 60º). Each model was connected to a whole aorta model and the procedures were performed using the Diamondback 360 coronary OA system through a 6F short-tip amplatz 1.0 guiding catheter. The protocol included two 30-second low-speed ablations followed by one 30-second high-speed ablation. Micro-computed tomography analyses of the models were performed before and after ablation to evaluate the ablated calcium volume and maximum depth. Results Eccentric calcium at inner side of the bending was more ablated than at outer side (6.6 mm3 vs 2.7 mm3, P < 0.0001). Among the inner side, the ablated calcium volume was higher in the R20/A60 model (8.28 mm3) than in R10/A100 (6.30 mm3; P = 0.14), R10/A60 (5.62 mm3, P = 0.04), and R20/A100 (6.06 mm3, P = 0.09) models (Figure 1A). The ablated maximum depth was also higher in the R20/A60 model (0.98 mm) than in other models (R10/A100: 0.84 mm, R10/A60: 0.90 mm, R20/A100: 0.78 mm); however, there were no significant differences. Moreover, among the outer side, the ablated calcium volume was higher in the R20/A100 model (5.17 mm3) than in the R10/A100 (1.95 mm3, P < 0.001), R10/A60 (2.12 mm3, P = 0.002), and R20/A60 (1.73 mm3, P < 0.001) models (Figure 1B). The ablated maximum depth was also significantly higher in the R20/A100 model (0.47 mm) than in other models (R10/A100: 0.32 mm, P = 0.03; R10/A60: 0.33 mm, P = 0.05; R20/A60: 0.27 mm, P = 0.01). Conclusions Curvature radius and bending angles could be associated with efficiency of OA for eccentric calcium in bending vessels. Although small curvature radiuses may be unsuitable for OA in the inner or outer side, it may be effective for inner side lesions with a large curvature radius and low bending angles, and outer side lesions with a large curvature radius and high bending angles.