In this study, we utilize 4D-flow MRI to investigate the relationship between hemodynamics and blood pressure change following hypotensor medication. Statistics indicated that FlowAPA significant increased when blood pressure drops. No differences were found in FlowIA, VAPA and VIA. This is probably because hypotensor medication has a vasodilatory effect, the widening of blood vessel will result in an increased flow. The results of this pilot study suggested that an acute blood pressure drop affects hemodynamic conditions of APA rather than IA.