Fig. 6: Optical mapping of simultaneous voltage and intracellular calcium in the contracting pig heart.

a, b Schematic experimental setting for simultaneous voltage and calcium ratiometry (a) and flow-chart (b). Dye loading details are provided in the Suppl. Methods. c Quantification of differences between dominant frequency (DF) values of voltage and calcium signals during programmed atrial electrical stimulation. Programmed atrial stimulation in the hearts of animals with persistent atrial fibrillation (PsAF) was performed after voltage and calcium ratiometry during AF and subsequent cardioversion. d Sample 6-s voltage and calcium signals during AF in isolated Langendorff-perfused hearts from controls and persistent AF animals. Their respective power spectral density and DF peaks are also shown. e Quantification of differences between DF values of voltage and calcium signals during AF. For consistency with in vivo electromechanical assessment, the dissociation threshold for voltage/calcium optical mapping signals was also set at 0.32 Hz. A mixed model based on Generalized Estimating Equations (GEE) was used to test for significant differences and interactions. f Prevalence of voltage and calcium dissociation in optical movies of hearts from controls and AF animals at 3 different voltage frequency ranges. The Fisher’s exact test was used to assess differences. All optical movies were taken at 500 frames per second. Source data are provided as a Source Data file. ACh acetylcholine, Ao aorta, LA left atrium, PA pulmonary artery.