SOME DIFFICULTIES INVOLVED IN THE PREDICTION OF THE STROKE VOLUME FROM THE PULSE WAVE VELOCITY

Abstract

The use of the pulse wave velocity as a key to aortic distensibility, and hence to the stroke volume of the heart, is on insecure grounds. The internal viscosity of the aortic walls distorts the distensibility curve at its very start, which accelerates the pulse wave velocity. The total vol. uptake, however, is not seriously affected. This viscosity varies not only with the location along the aorta, but also with the diastolic pressure. The three elastic elements of the wall have different distensibility characteristics. The relative role of each in determining the whole resistance to stretch depends upon the initial vol. The greater the role of smooth muscle, the greater the discrepancy between pulse wave velocity and vol. uptake. Tone changes may therefore alter both velocity and aortic uptake to an unknown degree. Further, because of the sluggish return of the aortic wall to the initial vol. level, both velocity and aortic uptake may be altered by a reduction in the rest interval allowed between successive stretches, i. e., by a change in pulse rate.