The usefulness of transesophageal atrial pacing combined with 2-dimensional echocardiography (echo-pacing) in predicting the presence and site of jeopardized myocardium, defined as areas of myocardium perfused by a vessel with a stenosis > or = 75% or by a collateral circulation if the supplying vessel was occluded, was evaluated in 31 patients with uncomplicated acute myocardial infarction who underwent coronary angiography. All 5 patients without jeopardized myocardium had a negative test, whereas 24 of 26 with jeopardized muscle had a positive test (sensitivity 92%; specificity 100%). To identify the site of jeopardized myocardium, tests that were positive for development of new asynergies were analyzed further, distinguishing those positive in the infarct or remote zone. Seven of 8 patients with new asynergies in the remote zone had areas of jeopardized myocardium outside the territory of distribution of the infarct-related vessel, whereas only 2 of 12 with new asynergies in the infarct zone had areas of jeopardized myocardium outside that territory (p < 0.01), correctly predicting the site of jeopardized myocardium in 17 of 20 cases. In conclusion, echo-pacing is useful for detecting the presence and site of jeopardized myocardium after an acute myocardial infarction.