Study of the mechanism of ultrasound angioplasty from human thrombi and bovine aorta.

Ultrasound angioplasty is a newly developed technology for percutaneous arterial recanalization. Data suggest that ultrasound is particularly effective in ablating fresh thrombi. Arterial walls were found to be resistant to ultrasound ablation. Thrombi, aortic wall segments, and hydroxyproline gelatin were studied in vitro to determine their respective ablation rates. The elasticity of the samples was determined in a force-mode apparatus. The cavitation threshold was determined in an arterial phantom apparatus. Thrombi displayed ablation rates that were > 20 times higher than those of aortic wall samples (591 +/- 82 vs 25 +/- 14 mg/s, p < 0.001). The differences in ablation rates were accompanied by significantly lower elasticities in the thrombus group compared with those in the aortic wall group (0.16 +/- 0.05 vs 312 +/- 37 g/cm2, p < 0.001). Experiments with hydroxyproline gelatin suggest a negative correlation (r = -0.90) between elasticity and ultrasound ablation. Ultrasound ablation of thrombi was evident only above the cavitation threshold. Thus, ultrasound angioplasty has the potential to induce the selective injury required for successful transluminal intervention in the treatment of thrombus-rich lesions.