(A-30) Modeling of vascular calcium fracture by intravascular lithotripsy

Introduction:: Vascular calcification is an increasingly prevalent pathophenotype in the coronary and peripheral vascular beds, which is associated with advanced age, diabetes mellitus, atherosclerotic cardiovascular disease, and chronic kidney disease. The presence of calcification portends lower procedural success rates, worse clinical outcomes, and adverse vascular events. Calcific plaques lead to difficulties in delivering and expanding stents in severely calcified vascular lesions with conventional percutaneous intervention strategies. Intravascular lithotripsy is a novel approach to treating stent underexpansion. This technique uses acoustic shockwaves in a balloon-based delivery system to fracture the calcific plaques and facilitates stent expansion. Whereas the safety and efficacy of intravascular lithotripsy have been reported in the treatment of severely calcified coronary and peripheral artery disease, the fracture mechanism of vascular calcium is not completely understood. Quantifying the impact of acoustic-solid interactions on calcium fracture and soft tissue injury is imperative for improving the technique and developing next-generation non-invasive treatment strategies.


Materials and Methods:: In this work, a computational framework is developed to study the fracture mechanisms and predict the fracture behaviors of calcium in the treatment of vascular calcification with the intravascular lithotripsy approach. A phase field method is developed to model the fracture of calcium. The acoustic-solid interactions are considered by explicitly coupling the propagation of shockwaves and the deformation of vascular calcium. The proposed model is implemented into finite element software by writing subroutines. The fracture of vascular calcium with different acoustic properties under different acoustic source properties is predicted. The impact of stress wave propagation in soft tissues is also analyzed to assess the safety of this technique. Moreover, the expansion of a stent in a severely calcified vascular lesion before and after the intravascular lithotripsy treatment is simulated to demonstrate the impact of calcium on stent expansion and the effectiveness of intravascular lithotripsy.


Results, Conclusions, and Discussions:: Results and discussions

The acoustic property of vascular calcium obviously influences the propagation of shockwaves within the calcium. Subjected to an identical acoustic source, calcium with a higher wave speed may suffer a severer segmentation. The acoustic source property plays a significant role in calcium fracture. The frequency and strength of the pulse and the distance of the source from the calcium dominate the fracture mode of calcium and thereby affect the treatment efficacy of intravascular lithotripsy. In addition, simulation results show that the vascular stent undergoes underexpansion before the treatment, while the lithotripsy treatment modifies calcium and facilities the stent deployment.

Conclusions

This study aims to develop a computational model for predicting calcium modification by intravascular lithotripsy and understanding the underlying mechanisms. This acoustic-solid coupling model can capture the vascular calcium fracture with different acoustic properties and quantify the role of lithotripsy emitters in calcium modification. The simulation results will contribute to improving and optimizing the safety and efficacy of intravascular lithotripsy.


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