From Pig to Human: Endo-Epicardial Substrate Characterization Using Dual Optical Mapping

Understanding the dissociation between endocardial and epicardial electrical activity is critical for investigating arrhythmia mechanisms. In this study, we used a dual optical mapping system to simultaneously record transmembrane voltage signals from both surfaces (endo-epi) in porcine and human hearts. Endocardium was paced at incrementally faster rates, starting with a pacing cycle length (PCL) of 1000 ms and continuing until conduction block or an arrhythmia. Porcine hearts showed an abrupt transition to fibrillation with negligible action potential duration (APD) alternans. In contrast, human hearts exhibited marked alternans and repolarization heterogeneity prior to fibrillation, with APD reaching up to 600 ms in the endocardium at PCL=230 ms. During fibrillation, endocardial maps revealed areas of conduction block and multiple reentrant sites, whereas epicardial activation was slower compared with the endocardium. These results shows endo-epicardial dissociation and species-specific differences in arrhythmogenesis, supporting the use of dual-surface optical mapping as a tool for translational cardiac research.