PURPOSE--To determine the value of magnetic resonance imaging (MRI) in the noninvasive detection of infarct related coronary artery patency after thrombolysis. METHODS--We studied 26 patients with acute myocardial infarction submitted to thrombolysis underwent MRI studies before and after 0.1mmol/kg gadolinium-DTPA injection within the first 48 h of MI. Signal intensity was assessed by circumferential profile analysis techniques. RESULTS--The average ratio of signal intensity of infarcted tissue over normal myocardium (I/N) was significantly higher in patients with patent arteries (1.3 +/- 0.13 vs 1.12 +/- 0.07, p < 0.02). Compared to coronariography MRI, sensitivity of 81 and specificity of 100 for the diagnosis of coronary patency. CONCLUSION--Gadolinium infusion increased infarcted and normal myocardium differentiation. The study of gadolinium kinetics at MRI is a promising technique for noninvasive diagnosis of coronary patency.