AIMS: The aim of this study was to explore the use of prolonged occlusion flow-mediated dilatation (PO-FMD) to dilate the radial artery prior to cannulation to increase cannulation success, reduce puncture attempts and reduce access-site complications in transradial coronary angiography. METHODS AND RESULTS: A total of 1,156 patients undergoing transradial coronary angiography were randomised into PO-FMD and sham PO-FMD groups. PO-FMD was achieved by a 10-minute inflation of a blood pressure cuff on the arm to above systolic pressure, followed by deflation with resultant radial artery dilation. In the sham PO-FMD group the cuff was not inflated. Operators were blinded to the intervention. Five hundred and eighty (580) patients were randomised to the sham PO-FMD group and 576 to the PO-FMD group. Cannulation failure was reduced with PO-FMD, with cannulation failure rates of 2.7% in the PO-FMD group and 5.8% in the sham PO-FMD group (p=0.01).The number of puncture attempts was reduced with the use of PO-FMD, with a median of one attempt in the PO-FMD group and two in the sham PO-FMD group (p
