Impact of electric spatially discordant alternans on cardiac magnetic field.

Spatially discordant alternans (SDA) play a crucial role in cardiac arrhythmogenesis by creating steep repolarization gradients facilitating conduction block and reentry. While traditionally studied using electrical indicators, this work provides an alternative perspective by characterizing SDA through their magnetic field signatures. Using a one-dimensional idealized cardiac fiber model, we demonstrate that magnetic-field measurements effectively detect SDA and temperature-dependent changes in cardiac action potentials, offering a noninvasive alternative to conventional electrophysiological metrics. Our results reveal that the spatial organization of SDA is mirrored in the distribution of the magnetic field, with SDA nodes clearly identifiable via spatial mapping. Notably, magnetic restitution curves exhibit a distinct pattern from action potential duration (APD)-based indicators, closely following the dynamics of the action potential upstroke. These findings establish the cardiac magnetic field as a powerful diagnostic tool for detecting SDA, opening alternative avenues for biomagnetic monitoring of arrhythmic risk.