Aim: Most cases of chest pain and almost all heart attacks are caused by atherosclerosis, a narrowing and hardening of the arteries that results from the accumulation of fatty deposits known as atheromas or plaques. The plaques typically comprise cholesterol- containing low- density lipoproteins (LDLs), smooth muscle cells, fibrous tissue, occasionally calcium and finally neovessels in advanced cases. The present study aimed to investigate the influence of cavitation effect of bubbles- induced by extracorporeal low- level combined high and low frequency unfocused ultrasound on advanced atherosclerotic plaque regression.

Methods: In this experimental study, the rabbits’ common carotid arteries were injured perivascularly by liquid nitrogen, followed by a 1.5% cholesterol-rich diet for eight weeks. Histology results showed severe stenosis (>70%) and neovascularization in the rabbits’ arteries. Then, the lesion region treated using extracorporeal low- level combined high (1MHz, 2 W/cm2) and low (150 KHz, 0.2 W/cm2) frequency unfocused ultrasound accompanied by discontinuation of cholesterol- rich diet in treatment group. Intraplaque contents were evaluated in the treatment group compared with the control group using B-mode ultrasonography and histology.

Results: B-mode ultrasonography and histopathology results showed a significant reduction in the mean value for intraplaque contents in treatment group compared with the other groups (P<0.05).