The aim of this study was to compare blood flow determined by coloured microspheres vs. Doppler intravascular ultrasound (US) combined with angiograpby. A second endpoint was to assess cardiac troponin I (cTnI) as a marker of myocardial injury. Doppler and microspheres were compared in 11 closed chest pigs. Blood flow was measured by catheter-based percutaneous technique in the left circumflex artery (LCx) and compared with coloured microspheres injected in the left ventricle. cTnI was measured in all pigs (73). The mean blood flow (mL/min(-1)) was 23.3+/-8.7 vs. 21.9+/-12.1 by Doppler vs. microspheres (p=0.156), correlation coefficient r=0.90,p=0.006. The mean coronary flow with Doppler technique and microspheres in the middle LCx was 22.9+/-7.6 vs. 21.2+/-6.2 (p=0.077), and distal 23.9+/-10.9 vs. 23.1+/-12.1 (p=0.698). Coronary blood flow measured by Doppler and angiography was comparable to myocardial blood flow measured by coloured microspheres injected in the left atrium or the left ventricle. cTnI was more sensitive to ischaemia than CK-MB mass. (E-mail: vike@haukeland.no) (C) 2002 World Federation for Ultrasound in Medicine Biology.