Mechanisms of increasing Arterial Compliance by intravascular Lithotripsy

Calcium plate fracture is a mechanism of Intravascular Lithotripsy (IVL). Using IVUS, POBA studies from the early 1990’s demonstrated the separation between the calcium – noncalcium plate junction (i.e., “debonding”). Importance of debonding has not been evaluated in the modern era of IVL. We hypothesize that debonding significantly contributes to improved compliance of IVL treated calcified vessels and evaluate the contribution of intimal tears. 20 calcified human coronary arteries were subjected to laser IVL. A Holmium laser (2J, 5Hz) with a 400μm fiber was utilized. Ultrasonic pressure waves at 62±0.4 atm were delivered circumferentially. OCT pullbacks were recorded pre- and post-IVL and arterial compliance was measured. Mechanisms for improved compliance was evaluated using histopathology, microCT, scanning electron microscopy (SEM) and finite element models (FEM). Lumen area increased from 2.3±0.4 to 4.3±0.8 mm2, p<0.01. Mean arterial compliance increased by 2.3±0.6 atm/mL, p<0.05. Post-IVL modifications including calcium plate fractures, calcium plate debonding and intimal tears were identified in 73% of arteries by OCT, microCT and SEM. FEM simulations suggest that calcium fractures contributed to increased vessel compliance, and changes correlate with the number of fractures. FEM also suggest de-bonding and intimal tears contributed a greater improvement in arterial compliance than calcium fractures alone. Results are consistent with three mechanisms contributing to increased arterial compliance, with debonding and intimal tears having a greater impact than calcium fractures alone.