Mechanical Weakness of Thoracic Aorta Related to Aging or Dissection Predicted by Speed of Sound with Collagenase.

Scanning acoustic microscopy reveals information on histology and speed of sound (SOS) through tissues. Slower SOS corresponds to lower stiffness. The aim of the present study was to investigate whether SOS values reflect the degree of degeneration with aging or dissection and whether enzymatic digestion susceptibility is distinct. The SOSs of media other than the atheromatous areas of normal and surgical dissections were measured and compared using medial degeneration grade (MDG) scores. To evaluate the damage rate, SOS was assessed after collagenase digestion. SOS scores negatively correlated with aging and MDG scores. Dissected aortas had higher SOS and MDG scores without age correlation. Collagenase digestion was present in all aortas, but older aortas were more injured than younger aortas. Dissected aortas were more vulnerable to collagenase. Older and dissected aortas expressed specific extracellular matrix components to compensate for mechanical weakness. The present method can evaluate mechanical weakness corresponding to histology to investigate the cause of rupture.