Tissue composition underlying local impedance in chronic infarction: an histological study

Abstract

Abstract Background Local impedance (LI) mapping is feasible and provides additional tissue characterization of the ventricular tachycardia (VT) substrate. VT isthmuses are usually located in areas of intermediate LI while low LI regions did not actively participate in the VT circuit. Histological studies evaluating the tissue composition underlying different LI values are lacking. Purpose To describe the tissue composition underling different LI subtypes in a chronic myocardial infarction (MI) swine model. Methods One-month after a non-reperfused anterior MI, five Landrace X Large White pigs underwent endocardial LI mapping (figure 1). LI thresholds were set using the blood-pool LI value to define low, intermediate, and high tissue resistance subtypes. A navigated needle-catheter was used to inject methylene-blue at sites with intermediate and low LI to guide the ex vivo tissue localization. Tissue was obtained for further histological analysis. Low and intermediate LI zones were analysed. Results A total of six and eight samples were analysed for low and intermediate LI, respectively. Compared to low LI zones, intermediate LI tissue displayed less Collagen I (1.03±0.26 vs. 0.34±0.35%, p=0.0082), Collagen III (9.92±2.98 vs. 6.47±1.80%, p=0.0380) and Collagen Volume Fraction (10.92±2.77 vs. 6.81±1.92, p=0.0163), without differences in the overall fibrotic and adipocytic deposition (figure 2). No significant differences in the Cx43, CTnI and SERCA2 expression were observed. Conclusion LI subtypes showed distinctive histological composition. Intermediate LI sites displayed less collagen content (I, III and collagen volume fraction) compared to those with low LI.Endocardial LI mappingHystological analysis: Collagen Content