The Utility of a Combination of 99mTc-MIBI Washout Imaging and Cardiac Magnetic Resonance Imaging in the Evaluation of Cardiomyopathy.

Background: In cardiomyopathy, ^99mTc-MIBI washout can reflect mitochondrial dysfunction and late gadolinium enhancement (LGE) on cardiac magnetic imaging (MRI) is associated with tissue fibrosis. We sought to determine the relationship between ^99mTc-MIBI uptake, ^99mTc-MIBI washout, and LGE on MRI in patients with cardiomyopathy. Methods: Twenty-one patients underwent rest myocardial perfusion scintigraphy at 45 minutes (early) and 4 hours (delayed) after intravenous ^99mTc-MIBI administration and cardiac MRI. We assessed myocardial perfusion, ^99mTc-MIBI washout, and LGE. We divided the left ventricle (LV) wall into 16 segments using a polar map. Then, we classified each segment into 5 groups according to ^99mTc-MIBI uptake in early-rest images and washout. Additionally, we created a contingency table based on LGE presence/absence in the groups. Results: We evaluated 336 segments in 21 patients. ^99mTc-MIBI uptake was decreased in 168 segments in the early-rest ^99mTc-MIBI images. ^99mTc-MIBI washout was observed in 108 segments with either normal perfusion or reduced perfusion in the early-rest ^99mTc-MIBI images. LGE was positive in 104 segments. A contingency table analysis with Fisher's exact test showed that LGE was observed significantly more frequently in the segments with decreased ^99mTc-MIBI uptake (p<0.001). In segments without a decreased ^99mTc-MIBI uptake, there was a significant correlation between increased ^99mTc-MIBI washout and the presence of LGE (p=0.033). Conclusions: In cardiomyopathy, the mitochondrial dysfunction in the early stage is shown as ^99mTc-MIBI washout, and fibrotic changes in the myocardium in advanced stages are shown as LGE on cardiac MRI. The severity of myocardial damage and the clinical stage of cardiomyopathy can be evaluated using multimodal imaging.