Correlation between ventricular local impedance and tissue composition by MRI in chronic infarction

Abstract

Abstract Background Local impedance (LI) mapping is feasible and provides additional tissue characterization of the ventricular tachycardia substrate. Data on tissue composition underlying different LI values are lacking. Purpose To correlate LI with tissue composition evaluated by magnetic resonance imaging (MRI) in a chronic myocardial infarction (MI) swine model. Methods One-month after a non-reperfused anterior MI, eighteen Landrace X Large White pigs underwent delayed-enhancement MRI (deMRI) and endocardial LI mapping. deMRI images were post-processed off-line with commercially available dedicated software; scar subtypes (with thresholds set at 40-60% of maximal pixel signal intensity [PSI]), border-zone corridors and left ventricular wall thickness were measured. LI thresholds were set using the blood-pool LI value to define low, intermediate, and high tissue resistance subtypes. LI maps were co-registered with deMRI for analyses. Results Low LI zones correlated with deMRI dense and transmural scar (exhibiting endo and epicardial PSI >60% in 91% and 80% of the cases, respectively). Intermediate LI tissue exhibited predominantly subendocardial scar with more heterogeneous composition (8%, 47% and 45% of the points had <40%, 40-60% and >60% endocardial PSI, respectively), and with less epicardial involvement (50% of points had epicardial PSI <40%). Border-zone corridors co-localized with intermediate LI tissue in most of the cases (77%). Low LI zones exhibited more pronounced wall thinning compared to intermediate LI tissue (p<0.001) (Figure 1). Conclusions LI correlated with scar density and transmurality on deMRI. Areas of low LI had higher proportion of dense, transmural scar and wall thinning compared to intermediate LI areas. MRI-detected border-zone corridors colocalized with intermediate LI in most cases.LI and deMRI data (endo and epi scar)LI and deMRI data (tissue thickness)