Spontaneous coronary reperfusion with TIMI-3 flow is associated with favorable clinical outcomes in patients with acute myocardial infarction (AMI). We investigated the ability of analyzing cardiac cycle-dependent variation of myocardial integrated backscatter (IBS) for predicting spontaneous reperfusion in anterior AMI. We recorded IBS images on admission in 104 patients with first anterior wall AMI and subsequently performed coronary angiography and coronary intervention. We measured the cyclic variation of IBS within the infarct zone and expressed its magnitude as phase-corrected magnitude (PCM) by giving positive and negative values when it showed synchronous and asynchronous contraction, respectively. Twenty-three patients showing TIMI-3 flow at the initial coronary angiography had smaller peak creatine kinase value than 57 patients with initial TIMI-0/1 flow (864+/-961 versus 2358+/-1757 IU/L; P=0.0002) and better percent wall thickening within risk area (36.1+/-15.1%) than those with TIMI-2 (16.7+/-12.8%, P<0.0001) or TIMI-0/1 (5.1+/-11.6, P<0.0001). The patients with initial TIMI-3 had higher PCM (2.7+/-1.3 dB) than those with TIMI-2 (-0.3+/-2.2 dB, P<0.0001) or those with TIMI-0/1 (-1.1+/-2.4 dB, P<0.0001). Using PCM=1.0 dB as the cutoff point, PCM detected TIMI-3 flow with 95.7% sensitivity and 90.1% specificity. Multivariable logistic regression analysis revealed that only PCM is an independent predictor for spontaneous reperfusion among the hemodynamic, echocardiographic, and electrocardiographic variables. Analysis of myocardial IBS could detect spontaneous reperfusion noninvasively in the emergent stage of anterior AMI.