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Recent optical mapping studies of cardiac tissue suggest that membrane voltage (V m) and intracellular calcium concentrations (Ca) become dissociated during ventricular fibrillation (VF), generating a proarrhythmic substrate. However, experimental methods used in these studies may accentuate measured dissociation due to differences in fluorescent emission wavelengths of optical voltage/calcium (V opt/Ca opt) signals. Here, we simulate dual voltage-calcium optical mapping experiments using a monodomain-Luo-Rudy ventricular-tissue model coupled to a photon-diffusion model. Dissociation of both electrical, V m/Ca, and optical, V opt/Ca opt, signals is quantified by calculating mutual information (MI) for VF and rapid pacing protocols. We find that photon scattering decreases MI of V opt/Ca opt signals by 23% compared to unscattered V m/Ca signals during VF. Scattering effects are amplified by increasing wavelength separation between fluorescent voltage/calcium signals and respective measurement-location misalignment. In contrast, photon scattering does not affect MI during rapid pacing, but high calcium dye affinity can decrease MI by attenuating alternans in Ca opt but not in V opt. We conclude that some dissociation exists between voltage and calcium at the cellular level during VF, but MI differences are amplified by current optical mapping methods. © 2011 Biophysical Society.

Original publication

DOI

10.1016/j.bpj.2011.06.012

Type

Journal article

Journal

Biophysical Journal

Publication Date

20/07/2011

Volume

101

Pages

307 - 318