P.017 THE ROLE OF THE CORONARY MICROCIRCULATION IN DETERMINING BLOOD FLOW

The coronary flow velocity profile is strikingly different from that of the proximal aorta, even though they are only a few centimetres apart and have almost identical pressure waveforms. We use wave intensity analysis to help explain this phenomenon, and to explore the importance of the coronary microcirculation in the regulation of coronary blood flow. In 18 subjects (mean age 54 years, 12 female) we measured simultaneous pressure and Doppler velocity using intra-arterial wires in the proximal left main stem, left anterior descending, circumflex artery and proximal aorta. Wave intensity analysis was used to separate the pressure waveform into its proximal- and distal-originating components. In the aorta the flow velocity waveform follows the aortic pressure waveform reasonably closely, although the peak velocity occurs before the peak pressure. Using wave intensity analysis we found that more than 70