Coronary flow velocity immediately after reperfusion reflects myocardial microcirculation in canine models of acute myocardial infarction

Recent reports indicate that the coronary microcirculation is sometimes inj ured, despite successful reperfusion in acute myocardial infarction (AMI). However, it is difficult to evaluate the coronary microcirculation immediat ely after reperfusion by using only angiography. The purpose of this study was to er;amine the relationship between the pattern of coronary blood flow velocity and myocardial microcirculatory injury immediately after reperfus ion in AMI. The authors recorded the left circumflex coronary flow velocity by using the Doppler guide wire method 10 minutes after reperfusion in a c anine model of AMI. In addition, myocardial contrast echocardiography was p erformed with the injection of contrast medium into the left circumflex cor onary artery before clamping of the coronary artery and 15 minutes after re lease of the clamp. From these images, the ratio of the normalized gray-lev el postreperfusion to preclamping in the contrast-enhanced area was determi ned. It was compared with coronary flow velocity variables. In the 10 dogs with a diastolic-to-systolic velocity ratio (DSVR) < 4.0, this velocity rat io 10 minutes after reperfusion correlated positively (r = 0.75,p <0.01) wi th the normalized gray-level ratio. However, the remaining three dogs with a DSVR greater than or equal to 4.0 markedly deviated from this pattern. Co ronary flow velocities in the three dogs were characterized by a greater de crease in systolic flow velocity and occurrence of early systolic retrograd e flow. Myocardial contrast echocardiographic images in these three dogs de monstrated a lower normalized gray-level ratio. In conclusion, the coronary flow velocity pattern immediately after reperfusion may reflect myocardial microcirculatory injury.