Aggressive plaque modification with rotational atherectomy and cutting balloon for optimal stent expansion in calcified lesions

Objective To evaluate the factors affecting optimal stentt expansion in calcified lesions treated by aggressive plaque modification with rotational atherectomy （RA） and a cutting balloon （CB）. Methods From January 2014 to May 2015, 92 patients with moderate to severe coronary calcified lesions underwent rotational atherectomy and intravascular ultrasound imaging at Chinese PLA General Hospital （Beijing, China） were included in this study, They were divided into a rotational artherectomy combined with cutting balloon （RACB） group （46 patients treated with RA followed by CB angioplasty） and an RA group （46 patients treated with RA followed by plain balloon angioplasty）. Another 40 patients with similar severity of their calcified lesions treated with plain old balloon angioplasty （POBA） were de- mographically matched to the other groups and defined as the POBA group. All patients received a drug-eluting stent after plaque prepara- tion. Lumen diameter and lumen diameter stenosis （LDS） were measured by quantitative coronary angiography at baseline, after RA, after dilatation, and after stenting. Optimal stent expansion was defined as the final LDS 〈 10%. Results The initial and post-RA LDS values were similar among the three groups. However, after dilatation, the LDS significantly decreased in the RACB group （from 54.5% ± 8.9% to 36.1%＋ 7.1%） but only moderately decreased （from 55.7% ± 7.8% to 46.9% ± 9.4%） in the RA group （time × group, P 〈 0.001）. After stenting, there was a higher rate of optimal stent expansion in the RACB group （71.7% in the RACB group, 54.5% in the RA group, and 15% in the POBA group, P 〈 0.001）, and the final LDS was significantly diminished in the RACB group compared to the other two groups （6.0% ± 2.3%, 10.8% ± 3.3%, 12.7% ± 2.1%, P 〈 0.001）. Moreover, an LDS 〈 40% after plaque preparation （OR = 2.994, 95% CI： 1.297-6.911） was associated with optimal stent expansion, which also had a positive correlation with the appearance of a calcified ring split （r = 0,581, P 〈 0.001）. Conclusions Aggressive plaque modification with RA and CB achieve more optimal stent expansion. An LDS ≤ 40% after plaque modification was a predictive factor for optimal stent expansion in calcified lesions. This parameter was also associated with the presence of calcified ring split.

Experimental Study and Design of Balloon- expandable Endovascular Stent Expansion

The application background and experimental research overview of medical endovascular stent are presented. Based on the analytical comparison of the current research achievements, the life cycle of medical endovascular stent is pointed out and the characteristics of stent expansion in the life cycle are emphasized on. The experimental scheme of in vitro stent expansion based on the machine vision technology in LabVIEW is presented. The selection and usage of the chosen component devices and design of measurement program for experiment are expatiated. A special drug-loading stent was expanded on the assembled platform of selected equipments and experimental results were analyzed. The experimental scheme presented in the paper provides powerful experimental support for the optimization of stent design and computer simulation of stent expansion by the finite element analysis.

Mechanical formula for the plastic limit pressure of stent during expansion

The mechanics of cardiovascular stents during the process of expansion are very important for stent function and safety. In general, finite element method （FEM） or experi- ments are major methods used to ascertain mechanical prop- erties of the stent. In this paper, we develop a theoretical model of the tubular stent, derive formulas for the axial forces and moments on the stent end, and propose formu- las for the plastic limit pressure vs. the stent＇s radius during expansion. Examples covering different geometrical param- eters and material parameters are provided, and the plastic limit pressures calculated by FEM and the present method are compared, proving that the present formulas are acceptable and meaningful for the design and innovation of the stent.