The role of photon scattering in optical signal distortion during arrhythmia and defibrillation

Optical mapping of arrhythmias and de. brillation provides important insights; however, a limitation of the technique is signal distortion due to photon scattering. The goal of this experimental/simulation study is to investigate the role of three-dimensional photon scattering in optical signal distortion during ventricular tachycardia (VT) and de. brillation. A three-dimensional realistic bidomain rabbit ventricular model was combined with a model of photon transport. Shocks were applied via external electrodes to induce sustained VT, and transmembrane potentials (V-m) were compared with synthesized optical signals (V-opt). Fluorescent recordings were conducted in isolated rabbit hearts to validate simulation results. Results demonstrate that shock-induced membrane polarization magnitude is smaller in Vopt and in experimental signals as compared to Vm. This is due to transduction of potentials from weakly polarized midmyocardium to the epicardium. During shock-induced reentry and in sustained VT, photon scattering, combined with complex wavefront dynamics, results in optical action potentials near a. lament exhibiting i), elevated resting potential, ii), reduced amplitude relative to pacing, and iii), dual-humped morphologies. A shift of up to 4mm in the phase singularity location was observed in Vopt maps when compared to V-m. This combined experimental/simulation study provides an interpretation of optical recordings during VT and de. brillation.