Structural Remodeling Analysis of Induced Arrhythmias in Rabbit Heart

mouhamed zakiou kolawole A RAIMI1, Saleem Ullah2, Pamela Pinheiro Martins3, Fernanda Fogaça Ruiz4, MARCELA SORELLI CARNEIRO-RAMOS5, SILVIA HONDA TAKADA4, Joao Salinet6
1HearTLab, Federal University UFABC Brazil, 2Center for Engineering, modelling and applied social sciences (CECS), Federal University of ABC (UFABC), 3Center for Mathematics, Computing and Cognition - Neurohistology Laboratory - Federal University of ABC., 4Universidade Federal do ABC, 5Federal University of ABC, 6HEartLab, Federal University of ABC


Abstract

Background Cardiac arrhythmias, such fibrillation and tachycardias, are marked by disrupted electrical conduction and exacerbated interstitial fibrosis. This study aims to characterize the histological remodeling of rabbit heart tissue during induced arrhythmias. Four New Zealand White rabbits (3–4 kg) were divided into control (n=1) and experimental (n=3) groups. Isolated hearts were subjected to Langendorff perfusion. Arrhythmias were induced using 1 µM carbachol and S1-S2 protocol (100 bursts of 2 ms pulses at 1.3 s intervals) to trigger atrial tachycardia and ventricular fibrillation. After electrophysiological study, hearts were fixed in formalin, and tissue samples were collected from four defined atrial and ventricular regions. From each region, three slices (each with 3–6 sections, 5 µm thick) were prepared. Hematoxylin and eosin (H&E) staining assessed general tissue integrity, and histological parameters of the remodeling. Quantitative image analysis (ImageJ) compared structural differences between groups. Results Control group showed that hearts had preserved tissue architecture. In contrast, hearts that underwent arrhythmia exhibited increased interstitial fibrosis and cardiomyocyte hypertrophy, more pronounced in ventricular fibrillation, indicating significant cellular stress and structural remodeling. Conclusion This study identifies distinct structural alterations associated with atrial and ventricular arrhythmias in rabbit hearts. The ongoing study will compare cardiac tissue characterization with the heart electrical activity underneath mapped simultaneously with panoramic optical and epicardial electrical contact mapping.