MR Imaging Evaluation of Myocardial Viability in the Setting of Equivocal SPECT Results with99mTc Sestamibi

Abstract

To determine if contrast material-enhanced magnetic resonance (MR) imaging is useful for assessment of myocardial viability in patients with equivocal stress-rest results from single photon emission computed tomographic (SPECT) examination with technetium 99m sestamibi. Twenty patients underwent stress-rest SPECT examinations with sestamibi. Results were considered equivocal for assessment of myocardial infarct on the basis of fixed perfusion defects that either had normal wall motion or exceeded any wall motion abnormalities. Patients then underwent (a). contrast-enhanced MR imaging for assessment of myocardial infarct and (b). cine MR imaging for assessment of wall motion. For image analyses, the left ventricle was divided into 14 segments. Wall motion and extent of infarct were assessed independently and compared. Forty-one segments were equivocal for infarct at SPECT, and most (21 of 41 [51%]) involved the posterior or inferior wall. Infarct was confirmed with MR imaging in 10 of 41 (24%) equivocal segments in eight patients (40%). An additional 29 segments in eight patients had infarct at MR imaging that was not suspected at SPECT, including segments in three patients with no clinical history of myocardial infarct prior to imaging. All cases of infarct except one that were equivocal or undetected with sestamibi at SPECT were nontransmural at MR imaging, and most of the unsuspected subendocardial infarcts (15 of 28 [54%]) had no associated wall motion abnormalities. Patients with radionuclide examination findings that are equivocal for infarct may benefit from contrast-enhanced MR imaging, particularly in the setting of nontransmural infarct.