Coronary flow reserve (CFR) was defined as the ability to increase coronary blood flow maximally in response to demand. The presence of viable myocardium in an infarcted zone indicates the presence of an intact microvasculature. We hypothesized that coronary flow reserve, which assesses the microcirculation, might be associated with the presence of viable myocardium.

Thirty seven patients with acute anterior myocardial infarction (mean age 55±10, 25 males) were enrolled and abnormal 127 segments were analyzed. Dobutamine stress echocard-iography (5 to 20 g/kg/min) was performed before coronary angiography (6±3 days after acute myocardial infarction (AMI)). Coronary flow reserve in infarct-related artery was measured at distal site to lesion immediately after successful angioplasty (7±2 days after AMI, with residual stenosis less than 20%) by using intracoronary Doppler flow wire. And follow-up 2-dimentional transthoracic echocardiography was performed in 26 patients during 333±161 (range of 109-780) days after acute myocardial infarction. Improvement of wall motion at least one segment by one more grade in dobutamine stress echocardiography was defined as contractile reserve. Viable myocardium was defined as the improvement of wall motion in transthoracic echocardiography during follow-up periods.

In 26 patients, viable myocardium was detected in 19 patients (73%) and their mean CFR was 1.74±0.42, which was significantly increased than 1.16±0.14 of CFR of patients without viable myocardium (p<0.001). The agreement of CFR score and presence of viable myocardium in AMI was excellent when CFR was above 1.3 (Area under the curve was 0.906 in receiver operating characteristic (ROC) curve). Sensitivity and specificity to detect viable myocardium in CFR more than 1.3 were 84% & 85% respectively.

CFR was increased in patients with viable myocardium, and the cut-off value of CFR more than 1.3 was agreed excellently to detect viable myocardium.