Conduction of Cardiovascular Sound Along Arteries

The velocity of the transmission of the second heart sound in the thoracic aorta of dogs was measured. The average velocity was found to be 5.7 meters per second. The figure agrees well with the published figures for the pulse wave velocity in the thoracic aorta of dogs. It was shown in humans that the velocity with which the second heart sound is conducted along the carotid artery does not change appreciably with frequency between 25 and 100 cycles per second. The average increase in velocity of 2.7% per half octave increase in frequency is, with 30% probability, due to random errors. The fraction of the energy of a murmur transmitted in the form of a transverse vibration along the abdominal aorta of dogs was estimated from recordings made before and after the transverse motion of the arterial wall was impeded with a clamp. Most of the energy of the murmur was found to be transmitted in the form of a transverse vibration in the aortic wall. It was concluded that most of the energy of cardiovascular sound in arteries is transmitted in a mode which is exactly analogous to the transmission of the pulse wave. Some puzzling features of intravascular sound conduction, such as the apparent transmission of murmurs mainly in the direction of flow, could be explained on this basis.