Acute myocardial ischemia: Magnetic resonance contrast enhancement with gadolinium-DTPA

Gadolinium-DTPA (Gd-DTPA) was used to improve the diagnostic utility of magnetic resonance (MR) in detecting early ischemia, before the onset of infarction. Following one minute of left anterior descending coronary artery occlusion, 9 dogs were intravenously injected with either 0.5 mM/kg of Gd-DTPA (6 dogs) or normal saline (3 dogs). One more minute was allowed for perfusion of injectate prior to cardiectomy and MR imaging of the ex situ heart. There was no visible difference in intensity or alterations in magnetic relaxation times between normal and ischemic myocardium in the control (saline-injected) animals. The Gd-DTPA-injected dogs had a well-defined segment of high intensity representing the ischemic myocardium in the anterior wall of the left ventricle, due to significant T2 relaxation rate enhancement in the adjacent normal myocardium. Both T1 and T2 were significantly (p <0.01) shortened in the normal myocardium of the Gd-DTPA animals, but relatively greater T2 relaxation rate enhancement in the adjacent normal myocardium. Both T1 and T2 were significantly (p <0.01) shortened in the normal myocardium of the Gd-DTPA animals, but relatively greater T2 relaxation rate enhancement resulted in reduced intensity of normal myocardium, thus increasing contrast with ischemic myocardium. As a result of the significant shortening of T1 and T2 in the normal myocardium, improved delineation of the ischemic segment could be obtained using calculated T1 and T2 images. It is concluded that Gd-DTPA has the potential to expand the sensitivity and diagnostic utility of MR in the study of occlusive coronary artery disease.