Effect of Low Frequency Vibration on the Arterial Wall

Poststenotic dilation is accompanied by alteration of the elastic properties of the arterial wall in the region where a murmur occurs. The low frequency vibrations contained in a murmur may cause the changes observed. Isolated human external iliac arteries were distended with 100 mm Hg pressure and vibrated with specific frequencies from 30 to 400 Hz. When dilation occurred, the radius increased at a rate of 7.1±3.4 SD % per day. However, for each artery, dilation tended to occur with one frequency in preference to others. The amplitude, as long as sufficient to produce vibration of the wall, was not important in determining this tendency. The older the artery the higher the frequency necessary to produce dilation. Young vessels, under 45 years, responded best to frequencies <100 Hz, and vessels 45-60 years old responded to frequencies 100-200 Hz and older vessels, >60 years, dilated with frequencies >200 Hz. The elastic diagram of the vessel after dilation showed the major change to be in the elastin component of the arterial wall rather than the collagen. These findings correspond to those seen in a vessel displaying poststenotic dilation.