An ultrasound phase-locked echo-tracking system was used for noninvasive measurements of diameter changes in the upper abdominal aorta of the anaesthetised cat. Comparisons were made between the noninvasively recorded diameter changes and central haemodynamic variables measured with inserted catheters and transducers. It was found that noninvasive observations of aortic diameter changes give reliable information on the direction and relative magnitude of the blood pressure change both in systole and in diastole. Indications of the direction of change of stroke volume, cardiac output, and aortic flow acceleration (a measure of cardiac inotropy) could also be gained. The information, taken together, comprises a pattern of response reflecting cardiovascular adjustments likely to have occurred. It is suggested that the technique is suitable for interpretation of (patho-) physiological changes in the foetus, as well as for determinations of great vessel compliance in man, i.e., in atherosclerosis research.
Animals Aorta, Abdominal