Multi-Mode Quantitive Evaluation Of Myocardial Infarction With Non-Contrast Cardiac Magnetic Resonance Imaging

Objective:Cardiac Magnetic Resonance?CMR?is currently recognized as the best diagnostic method for myocardial infarction?MI?,which can provid more reference indicators and prognostic information.Late Gadolinium Enhancement?LGE?is the gold standard for accurately detecting irreversible myocardial injury,however,recent concerns of gadolinium-based contrast agents present challenges for its use in patients with severe renal dysfunction.To date,large animal and single center humanstudies have demonstrated that native T1 maps at 3T can be used to detect and characterize chronic MIs.The objective of this study was to investigate the diagnostic capacity of native T1mapping at 3T for characterizing chronic MIs in a multi-center setting.Furthermore,staging myocardial infarctions?MI?,particularly differentiating acute from chronic phase of MI,is a common requirement in making clinical decisions.Given T2 is sensitive to intramyocardial edema in acute MI,thisstudy attempted to stage MI by combining T1mapping with T2-based imaging without gadolinium-based contrast angets.Methods:A total of 105 patients with single prior MI were recruited in United States,Korea and China respectively.Non-contrast T1 mapping and LGE were performed at10.1 years?IQR 5.3-16.5years?post the first acute MI.Infarct size was measured as the percentage of total LV myocardial volume and transmurality was measured with the centerline chord method by two experienced observers using CVI⁴².Sensitivity,specificity,ROC metrics and inter-and intra-observer variabilities were assessed relative to LGE.For animal study,Hemorrhagic?n=15?and non-hemorrhagic?n=9?MIs were created in dogs.Multi-parametric non-contrast mapping?T1,T2 and T2*?and late-gadolinium enhancement?LGE?were performed in the acute and chronic phases of MI.T1,T2 and T2*values of the hemorrhagic,infarcted areas surrounding the hemorrhage?peri-hemorrhagic?,non-hemorrhagic and un-infarcted/remote territories were measured.The changes in T1,T2 and T2*between the MI territories from remote myocardium were compared with respect to infarct age and field strength.Histopathology and immunohistochemistry were performed to gain insight into CMR findings.Results:1.Sensitivity,specificity and AUC for identifying infarct location based on native T1 mapping relative to LGE were 88%,92%and 0.93,respectively.Native T1maps were not different for measuring infarct size?Native T1 maps:12.1%±7.5%;LGE:11.8%±7.2%,p=0.82?and were in agreement with LGE?R2=0.92,bias=0.09±2.6%?.Corresponding inter-and intra-observer assessments were also in agreement?inter-observer:R2=0.90,bias=0.18±2.4%;and intra-observer:R2=0.91,bias=0.28±2.1%?.Native T1 maps were not different for measuring infarct transmurality?Native T1 maps:49.1±15.8%;LGE:47.2±19.0%,p=0.56?and showed agreement?R2=0.71;bias=1.32±10.2%?.Corresponding inter-and intra-observer assessments were also in agreement?inter-observer:R2=0.81,bias=0.1±9.4%;and intra-observer:R2=0.91,bias=0.28±2.1%,respectively?.Sensitivity,specificity and AUC for identifying transmural infarction on native T1 maps relative to LGE were 71%,92%and 0.82,respectively.2.Native T1,T2 and T2*of MI territories and their relative change from remote myocardium showed significant dependence on infarct age and type.Specifically,in the chronic phase of MI,T2 of non-hemorrhagic MI territories resolved to remote levels?%difference in T2=0.0±3.2%?;however,T2 of peri-hemorrhagic zones remained elevated relative to remote territories?%difference in T2=8.6±5.1%?and was associated with ongoing active inflammation.Conclusion:1.Non-hemorrhagic MI and acute hemorrhagic MI can be differentiated from normal myocardium using native T1mapping,but the identification of chronic hemorrhagic MI requires T2*to spatially localize the infarcted area;2.Non-hemorrhagic MI can be staged based on T2 changes in the infarcted myocardium.However,for hemorrhagic MI,combined T2*is required to accurately locate the infarcted area for staging.Base on the conclusion of the above,the present study indicated that Native T1mapping combined with T2 and T2*mapping is a viable alternative for MI imaging to LGE.