Session P87.1

Using Image Registration to Reconstruct Spatiotemporal Electrical Activity in Cardiac Optical Mapping Studies

M Svrcek*, S Rutheford, AYT Chen, I Provaznik

Brno University of Technology
Brno, Czech Repub.

Optical mapping provides an opportunity to study the propagation of electric activation across the heart surface. In order to do so, however, it is necessary to correct for artifact introduced by heart wall motion. This problem has been addressed by pharmacological uncoupling of electrical and mechanical activity or by using mechanical restraint to minimize heart wall motion. While pharmacological uncouplers are widely used in cardiac optical mapping, they perturb electrical activity through their effects on transmembrane ion channels. This paper describes a novel technique that enables electrical propagation on the heart surface to be reconstructed in the absence of pharmacological uncouplers. In this approach, image registration methods are used retrospectively to correct for heart wall motion. Isolated, Langendorff-perfused rat hearts were stained with the voltage-sensitive dye (Di-4-ANEPPS) and illuminated with blue and green LED arrays. Fluorescence emission was acquired with an EMCCD camera (Cascade128+, Photometrics) at 326 frame/s via a 600 nm long-pass filter. The field of view was 20x20 mm, 128x128 pixels at 16 bit resolution. Images were registered as follows. Bilinear interpolation was applied to separate image subregions, which were matched in successive frames on the basis of a cross correlation criterion using a linear transform that allows rotation and two-axis translation. A nonlinear transformation that accommodates image deformation was necessary for registration across the full image field. Image registration substantially reduced motion artifact and enabled the propagation of electrical activation to be reconstructed accurately with respect to well-defined material points on the heart surface. The process increases SNR at the cost of introducing some high frequency noise. Image registration also enables action potential duration to be estimated reliably at defined material locations in the absence of electro-mechanical uncouplers. We believe that this technique offers considerable advantages for future studies on the role of electro-mechanical interaction in reentrant arrhythmia.

(Abstract Control Number: 73)