We have recently discovered that if ultrasound transmission is briefly suspended (triggered to just one frame per cardiac cycle) after very small doses of intravenous perfluorocarbon-exposed sonicated dextrose albumin, the myocardial contrast produced is significantly enhanced. The objective of this study was to test whether this technique (termed transient response imaging) could identify myocardial perfusion abnormalities during adenosine and dobutamine stress echocardiography. In 10 open-chest dogs with a significant (> 50%) coronary stenosis determined by quantitative angiography, intravenous perfluorocarbon-exposed sonicated dextrose albumin (0.005 to 0.01 ml/kg) was given at rest during peak dobutamine stress (20 to 30 micrograms/kg/min). Adenosine stress (100 to 140 micrograms/kg/min) was also given in seven of these dogs. The peak myocardial videointensity and spatial extent of contrast defect with transient response imaging (TRI) were compared with conventional 30 Hz frame rates, as well as wall thickening and coronary flow responses. In all 10 dogs there was visually evident myocardial contrast with TRI. In comparison, myocardial contrast was visually evident in only one of these dogs with conventional imaging. The peak myocardial videointensity ration in the stenosed perfusion bed divided by the normally perfused bed when TRI was used decreased in all dogs during dobutamine stress and correlated with minimal coronary lumen diameter (r = 0.70; p = 0.02). Visually evident myocardial contrast defects were detectable in nine of 10 dogs at peak dobutamine stress but only in one of the dogs with conventional imaging. All seven dogs that received adenosine demonstrated contrast defects with TRI, whereas none demonstrated contrast defects with conventional imaging. We conclude that the myocardial contrast produced with transient response imaging can be used to detect functionally significant coronary stenoses.