title: Experimental validation of alternating transillumination for imaging intramural wave propagation.
abstract: Current techniques to map intramural activation patterns in ex vivo cardiac tissue have limited spatial resolution. Here, we report on the experimental validation of a novel optical technique that was recently proposed to resolve the size and depth of intramural wave fronts using alternating transillumination (AT). AT was achieved by simultaneously mapping the epi- and endocardial surfaces with two synchronized CCD cameras and rapidly alternating LED illumination between both surfaces. Optical phantoms were made based on tissue optical properties measured using a hybrid optical spectrometer. Spherical fluorescent sources (Scarlet microspheres, Invitrogen, UK) of varying sizes were embedded at known depths in the phantoms. Coronary-perfused procine left ventricular slab preparations were stained with DI-4-ANBDQBS (n = 3) and paced at known intramural depths. In phantoms we were able to reliably estimate the depth of the center of fluorescent sources (9.6 ± 5.4% error), as well as their transmural extent (15.7 ± 11.5% error). In ventricular slabs we were able to localize the sites of origin of intramural excitation waves with a precision of ± 1.6 mm. Transmural conduction velocities were, for the first time, measured optically from the surfaces and found to be 21.0 ± 12.4 cm/s. In conclusion, alternating transillumination is a promising technique for reliable reconstruction of depth and expansion rate of intramural activation wave fronts in cardiac tissue.
authors.affiliation: Faculty of Biological Sciences, Multidisciplinary Cardiovascular Research Centre, University of Leeds, Leeds, LS2 9JT UK. r.d.walton@leeds.ac.uk
authors.forename: Richard D
authors.initials: RD
authors.lastname: Walton
authors.forename: Christopher D Lawrence
authors.initials: CD
authors.lastname: Xavier
authors.forename: Ilias
authors.initials: I
authors.lastname: Tachtsidis
authors.forename: Olivier
authors.initials: O
authors.lastname: Bernus
mesh_terms: D000200:Action Potentials / Q000502:physiology*; D000818:Animals; D018780:Body Surface Potential Mapping / Q000379:methods*; D006329:Heart Conduction System / Q000502:physiology*; D008029:Lighting / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013552:Swine; D056969:Voltage-Sensitive Dye Imaging / Q000379:methods*