Determination of Location, Size, and Transmurality of Chronic Myocardial Infarction Without Exogenous Contrast Media by Using Cardiac Magnetic Resonance Imaging at 3 T

Abstract

Background LGE CMR is a powerful method for characterizing MI, but the requisite gadolinium infusion is estimated to be contraindicated in nearly 20% of MI patients due to end-stage chronic kidney disease. The purpose of this study is to investigate whether T1 Cardiovascular-Magnetic-Resonance Imaging (CMR) obtained without contrast agents at 3T could be an alternative to Late-Gadolinium-Enhanced (LGE) CMR for characterizing chronic myocardial infarctions (MIs) using a canine model of MI. Methods and Results Canines (n=29) underwent CMR at 7 days (acute, AMI) and 4 months (chronic, CMI) post-MI. Infarct location, size and transmurality measured using native T1 maps and LGE images at 1.5T and 3T were compared. Resolution of edema between AMI and CMI was examined with T2 maps. T1 maps overestimated infarct size and transmurality relative to LGE images in AMI (p=0.016 and p=0.007, respectively), which was not observed in CMI (p=0.49 and p=0.81, respectively), at 3T. T1 maps underestimated infarct size and transmurality relative to LGE images in AMI and CMI (p<0.001), at 1.5T. Relative to the remote territories, T1 of the infarcted myocardium was increased in CMI and AMI (p<0.05); and T2 of the infarcted myocardium was increased in AMI (p<0.001), but not in CMI (p >0.20) at both field strengths. Histology showed extensive replacement fibrosis within the CMI territories. CMI detection sensitivity and specificity of T1 CMR at 3T were 95% and 97%, respectively. Conclusions Native T1 maps at 3T can determine the location, size and transmurality of CMI with high diagnostic accuracy. Patient studies are necessary for clinical translation.

Native T 1 Mapping by 3-T CMR Imaging for Characterization of Chronic Myocardial Infarctions

“…Recent studies in a canine model of MI have shown that native T 1 mapping at 3-T can reliably characterize chronic MIs and can therefore be a potential alternative to LGE CMR (12). In this study, we investigated the clinical validity of the canine findings in 2 pilot patient populations with prior STEMI and NSTEMI, respectively.…”

“…Hence, a CMR approach that could visually detect and quantify chronic MI without exogenous contrast media would be immensely valuable in the overall diagnosis and management of MI patients. Using a canine model of reperfused chronic MI, we previously demonstrated that native T 1 mapping at 3-T provides significantly greater sensitivity and specificity for characterizing chronic MI over native T 1 mapping at 1.5-T (12). In this study, we examined whether native T 1 Patients were excluded from the study if they had symptoms of chest pain, electrocardiogram changes, or cardiac enzyme elevation within 1 year before the date of CMR examination; multiple infarctions; or were contraindicated in a magnetic resonance study (claustrophobia, metallic implants, glomerular filtration rate <45 ml/min/1.73 m 2 , and so on).…”

“…In both techniques, infarct was identified using the mean AE 5 SD criterion relative to the respective reference regions of interest (12,(15)(16)(17)(18). Hypointense cores on T 1 maps, suggestive of chronic iron deposition (12) or fat deposition (19-21), that were not detected as infarcted using the mean AE 5 SD criterion were manually included in the final analysis.…”

Novel cardiac nuclear magnetic resonance method for noninvasive assessment of myocardial fibrosis in hemodialysis patients

“…Visual assessment of the native T1 parametric maps was undertaken to look for areas of focal increased signal that likely indicate replacement fibrosis (23,24).…”

“…Fishers exact test confirmed there was a significant difference between HD and controls groups for areas of discrete mid-wall or insertion point hyperintensity (P=0.026). Figure 3 shows the mid-ventricular end-diastolic cine MRI and native T1 maps of 1 control and 3 HD patients with progressively increasing native T1 times (23).…”