Myocardial Viability Imaging using Manganese‐Enhanced MRI in the First Hours after Myocardial Infarction

Figure 1. Effects of manganese on cardiac electrophysiology and function: a) Upper panel: Representative optical action potential and Ca2+ transient traces from HL‐1 cardiomyocytes at baseline and at 2 and 5 min after superfusion with 0.1 mM MnCl2 with/out CaG supplement. Lower panel: APD50 and APD80 were not affected by 0.1 mM MnCl2 (n = 5), but Ca2+ transient amplitude was reduced by 0.1 mM MnCl2 and partially restored by supplement with 0.1 mM CaG (n = 4). Data were analyzed by paired two‐tailed Student's t‐test to compare with baseline **p = 0.0011 ****p < 0.0001 and unpaired two‐tailed Student's t‐test to compare MnCl2 to MnCl2+CaG‐ ## p = 0.0011 ### p = 0.0003). b) Representative optical action potential traces from human iPSC derived cardiomyocytes at baseline and at 2 and 5 min after superfusion with 0.1 mM MnCl2. APD50 and APD80 were not affected by 0.1 mM MnCl2 (n = 6). c) Representative end systolic ultrasound images acquired before and after injection of the compounds indicated. d) Time course of myocardial contractility quantified as fractional shortening showed immediate reduction in myocardial contractility after i.v. infusion of 0.1 mM MnCl2 (n = 6) which can be reversed…

Figure 2. Time course of manganese uptake in control mice. a) R1 values (mean ± SEM) in myocardium, liver, muscle, and blood at baseline, 10, 30, 60 min and 24 h post injection of 1) 0.02 mM MnCl2 i.v. (n = 6); 2) 0.1 mM MnCl2 + 0.1 mM CaG i.v. [MnCaG1:1] (n = 5); 3) 0.1 mM MnCl2 + 0.05 mM CaG i.v. [mnCaG2:1] (n = 5); or 4) 0.1 mM MnCl2 i.p. (n = 5). Data were analyzed by one‐way ANOVA. Myocardium 10, 30, and 60 min (****p < 0.0001); liver 10, 30 (****p < 0.0001), and 60 min (***p = 0.0002); muscle 60 min (**p < 0.0033); and blood 10 min (***p = 0.0008), 30 min (***p = 0.0005), and 60 min (****p < 0.0001). b) Representative images for each group at baseline, 10, 30, and 60 min and 24 h post injection.

Figure 3. T1 mapping of manganese uptake acutely after MI. a) Time course of changes in R1 over the first 3 h of MI from the area‐at‐risk segments (AAR‐MI, n = 8) and viable segments remote from the AAR (Remote‐MI, n = 8) of infarcted hearts; and naïve mice with the same Mn2+ infusion times (Viable‐Naïve, n = 5). Mice received i.p. injections of 0.1 mM MnCl2 40 min before permanent coronary occlusion. Measurements were repeated at 2 days (n = 5) after MI (60 min after re‐administration of 0.1 mM MnCl2). Statistical significance were calculated using one‐way ANOVA followed by Tukey's post hoc test to compare between groups at 1 h (***p = 0.0004), 2 h (***p = 0.0007), 3 h (***p = 0.0004), and 48 h and using two‐way repeated measures ANOVA followed by Tukey's post hoc test (Viable‐MI group, 1 h versus 3 h, # p = 0.0481). b) Representative T1 maps of infarcted and healthy mice. Blue arrow = Remote‐MI, Yellow arrow = AAR‐MI, Green arrow = Viable‐Naïve.

Figure 4. Direct comparison of MEMRI with LGE‐MRI in AMI. a) Representative MEMRI and LGE‐MRI images acquired in mice at 1 h, 1 and 14 days after MI and compared with 14 days histological TTC staining for delineation of infarct area. b) Mean of infarct size measured by MEMRI and LGE‐MRI at 1 h (n = 7), 1 day (n = 14), and 14 days (n = 10) after MI and compared with histological TTC staining. Data were analyzed using unpaired (MEMRI vs LGE‐MRI at 1 h, **p = 0.0015) and paired (MEMRI vs LGE‐MRI at 1 day and 14 days) two‐tailed t‐tests and one‐way ANOVA followed by Tukey's post hoc test (LGE‐MRI, 1 h vs 1 day, ## p = 0.0083 and 1 h vs 14 days, # p = 0.024). c) Correlation between 1 h versus 1 day MEMRI (p = 0.0003) and LGE‐MRI (ns) measurements of infarct size. d) Correlation between MEMRI versus LGE‐MRI measurements of infarct size at 1 (p = 0.0002) and 14 days post‐MI (p = 0.0001). Correlations were calculated using Pearson correlation.