The endovascular treatment of infrapopliteal arterial disease is challenging, with an estimated 1-year reintervention rate of 70% following plain old balloon angioplasty (POBA) (1). Calcified lesions are the most difficult to treat and the most prone to immediate technical failure following POBA (2). Intravascular lithotripsy has been recently introduced into the therapeutic arsenal of vessel preparation to make calcified blood vessels more compliant prior to balloon angioplasty to reduce trauma to the vessel wall during the intervention (3). However, the superiority of IVL over POBA in the treatment of calcified tibial lesions remains to be established in the literature. The aim of this abstract is to present the initial results of an ongoing ex vivo experimental study comparing the mechanistic performance of IVL vessel preparation to POBA alone in calcified tibial arteries.

The study sample consisted of human amputated limbs with evidence of concentric calcification in at least one tibial artery. Prior to the experimental procedure, amputated limbs were scanned on a 7T MRI using UTE (Ultra-short echo time) and T2 weighted sequences to characterize target lesions at high resolution (200 mm x 200 mm x 200 mm isotropic). All experiments were conducted in a hybrid operating room under fluoroscopic guidance (Figure 1). The distal tibial artery was exposed and accessed with a micropuncture kit. A 0.014" wire was placed through-and-through, exiting the proximal tibial artery which was transected to allow for flushing of contrast and saline throughout the experiment. An angiogram was then obtained to delineate the stenotic lesions which were then randomized to receive either IVL prior to POBA (IVL-POBA) or POBA alone. The levels of the lesions were marked and intravascular ultrasound (IVUS) was performed for lesion measurements and vessel sizing. Intravscular lithotripsy was employed according to the manufacturer's instruction for use, prior to angioplasty with the same balloon. Balloon angioplasty was performed at the minimum pressure required for the balloon to reach its profile diameter. Completion angiograms and IVUS were then performed to measure the luminal gain post-intervention. Target lesions were harvested and imaged ex-vivo with microCT prior to decalcification and histologic processing with Movat's pentachrome and Hematoxylin & Eosin (H&E Staining).

9 lesions were treated in 3 amputated limbs; 1 above-the-knee and 2 below-the-knee amputations, and one procedure had to be aborted due to failure to achieve intraluminal access. All limbs had a history of failed revascularization attempts. 8 target lesions were identified in the anterior tibial and 1 in the peroneal artery. IVL-POBA was performed in 5/9 cases and POBA in 4/9. The mean diameter stenosis was 54±7% and 43±8% in the IVL-POBA and POBA groups respectively, relative to respective reference vessel diameters of 3±0.1mm and 3±0.2mm. The mean balloon inflation pressure was 6±1 for IVL-POBA versus 9±1 for POBA (p-value = 0.002), however, there was no significant difference in luminal gain (68±28%mm vs. 36±17%; p-value 0.15). Histology demonstrated intimo-medial dissection in 44% of IVL-POBA vessel rings versus 67% for POBA (p-value = 0.23). IVL-POBA rings also demonstrated micro-cracks in the vessel wall. (Figure 2).

The early results of this study demonstrate that vessel preparation with IVL is associated with lower inflation pressures and trend towards fewer uncontrolled dissections although no significant difference in luminal gain was observed. Future work will determine if IVL substantially improves luminal gain and/or reduces vessel dissections in calcified tibial arteries. This work will contribute to vascular surgeons making informed decisions on whether the added performance and safety of such IVL devices warrant the added costs and potential harm.

1. Rocha-Singh KJ, Zeller T, Jaff MR. Peripheral arterial calcification: Prevalence, mechanism, detection, and clinical implications. Catheter Cardiovasc Interv. 2014;83(6):E212-E220. doi:10.1002/ccd.25387 2. Fernandez N, McEnaney R, Marone LK, et al. Predictors of failure and success of tibial interventions for critical limb ischemia. Journal of Vascular Surgery. 2010;52(4):834-842. doi:10.1016/j.jvs.2010.04.070 3. Adams G, Soukas PA, Mehrle A, Bertolet B, Armstrong EJ. Intravascular Lithotripsy for Treatment of Calcified Infrapopliteal Lesions: Results from the Disrupt PAD III Observational Study. J Endovasc Ther. Published online August 12, 2021:15266028211032952. doi:10.1177/15266028211032953