Deceleration vs. acceleration: a haemodynamic parameter in the assessment of vascular reactivity. A preliminary study

The parameter deceleration vs. acceleration ( dc ac ) as derived from the instantaneous peak velocity is obtained by dividing the descending and ascending slopes of plotted velocity curves. Blood velocities were recorded with a specially designed continuous-wave ultrasonic Doppler unit which provides: the instantaneous peak velocity, the instantaneous mean velocity, the acceleration, and an indication of volume flow. A physical meaning to the dc ac parameter is given through an analysis, based on an electrical model, of a small portion of an artery. This gives a simple relationship which only takes account of the assumed vascular resistances. Measurements were performed in 67 male subjects; 39 were normotensive control subjects and 28 had established moderate hypertension. In both groups there was an increase of dc ac in passing from the supine to the erect position, the increase being more accentuated by hypertension. The variation of dc ac with age was significantly different in both groups. The results suggest that this parameter is a sensitive indicator of variations in vascular reactivity and as an indicator of structural changes in the arterial wall.