Retrograde flow components in the brachial artery. A new hemodynamic index

Abstract

Arm elevation induces diastolic retrograde flow in the brachial artery and an incremental rise in arterial compliance in healthy subjects with no modifications in vascular resistance. In contrast, changes in resistance have been observed after handgrip exercise. Our objective was to investigate if the resistance change induced by isometric handgrip exercise is able to reverse diastolic retrograde flow induced by arm elevation in a healthy population and to explore these adaptive changes in hypertensive subjects. Arterial flow velocity Doppler measurements were obtained including: (a) a baseline measurement, (b) measurement 30 s after arm elevation, (c) measurement during handgrip maneuver with the arm elevated, (d) measurement during handgrip release with the arm elevated. Our findings showed that diastolic retrograde flow is induced by arm elevation, partially increased by arm-up handgrip and completely reversed during arm-up handgrip release both in healthy and hypertensive subjects. As compared with normal subjects, deceleration time was longer in the hypertensive subjects during baseline but not during the arm-up stage, handgrip contraction and handgrip release stages. An important increase in deceleration time values from baseline to arm-up and handgrip contraction stages was observed in normal subjects but not in the hypertensive group. We believe that the highly significant difference in reactivity to postural changes observed in deceleration time values constitutes a promising hemodynamic index to investigate. Also, our observation of complete reversal of the retrograde flow during arm-up handgrip release provides a new approach to postural and exercise-induced vasomotor responses.