Multicenter Study on the Diagnostic Performance of Native-T1 Cardiac Magnetic Resonance of Chronic Myocardial Infarctions at 3T.

Background: Preclinical studies and pilot patient studies have shown that chronic infarctions can be detected and characterized from cardiac magnetic resonance without gadolinium-based contrast agents using native-T1 maps at 3T. We aimed to investigate the diagnostic capacity of this approach for characterizing chronic myocardial infarctions (MIs) in a multi-center setting. Methods: Patients with a prior MI (n=105) were recruited at 3 different medical centers and were imaged with native-T1 mapping and late gadolinium enhancement (LGE) at 3T. Infarct location, size, and transmurality were determined from native-T1 maps and LGE. Sensitivity, specificity, receiver-operating characteristic metrics, and inter- and intraobserver variabilities were assessed relative to LGE. Results: Across all subjects, T1 of MI territory was 1621 +/- 110 ms, and remote territory was 1225 +/- 75 ms. Sensitivity, specificity, and area under curve for detecting MI location based on native-T1 mapping relative to LGE were 88%, 92%, and 0.93, respectively. Native-T1 maps 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 (R-2=0.92, bias, 0.09 +/- 2.6%). Corresponding inter- and intraobserver assessments were also highly correlated (interobserver:R-2=0.90, bias, 0.18 +/- 2.4%; and intraobserver:R-2=0.91, bias, 0.28 +/- 2.1%). Native T1 maps were not different for measuring MI transmurality (native-T1 maps: 49.1 +/- 15.8%; LGE: 47.2 +/- 19.0%,P=0.56) and showed agreement (R-2=0.71; bias, 1.32 +/- 10.2%). Corresponding inter- and intraobserver assessments were also in agreement (interobserver:R-2=0.81, bias, 0.1 +/- 9.4%; and intraobserver:R-2=0.91, bias, 0.28 +/- 2.1%, respectively). While the overall accuracy for detecting MI with native-T1 maps at 3T was high, logistic regression analysis showed that MI location was a prominent confounder. Conclusions: Native-T1 mapping can be used to image chronic MI with high degree of accuracy, and as such, it is a viable alternative for scar imaging in patients with chronic MI who are contraindicated for LGE. Technical advancements may be needed to overcome the imaging confounders that currently limit native-T1 mapping from reaching equivalent detection levels as LGE.