Electrical Inhomogeneities of Guinea Pig Atrial Tissue in High Resolution Optical Potential Mapping

Inhomogeneities in the tissue are a determining factor for cardiac function and can be either structural or functional. Using the voltage sensitive fluorescent dye di-4-ANEPPS on incubation stained guinea pig preparations allows to map the tissue's response to externally applied electric shocks. Previous work on ventricular muscle preparations revealed a membrane potential morphology that could be relevant during defibrillation [1]. Using a two pulse stimulus protocol we are able to map the excitation response to a short triggering field pulse and to consequently map the membrane potential morphology resulting from a second field pulse, which is applied in the depolarized state and is attributed to the interaction of the electric field with the tissue. This approach is now carried over to atrial preparations. A custom developed object-positioning and image-stitching method allows for wide view analysis of the atrial tissue structure. Objective-magnifications of 10x, 20x, 40x and 63x enable a multi-scale based analysis with resolutions up to 15 micrometers. This is augmented with information from transmitted light microscopy so that it is possible to correlate the membrane potential patterns with the visible structure of the atrial tissue, providing further insight into atrial excitation and conduction.[1] Windisch,H. et al. (2007) Quantification of shock-induced microscopic virtual electrodes assessed by subcellular resolution optical potential mapping in guinea pig papillary muscle. J Cardiovasc Electrophysiol; 18(10):1086-1094