Normal and fractionated cardiac near fields and their relation to microstructure - an experimental approach

Quasi-continuous anisotrope conduction and discontinuous complex conduction in the rabbit heart was examined by recording and analyzing the cardiac near field E. electrically paced papillary muscles with tight microstructure were used as a model for continuous conduction, atrial preparations as substrate for branching and complex discontinuous conduction. Micro-miniature sensors positioned very close to the tissue (non-contact type) and a high-resolution data acquisition system revealed fine details of the field behavior not known before. Even strongly parallel oriented structures may induce small fractionations during slightly oblique propagation (quasi-continuous conduction). The vector-loops of E changed their morphology during very small changes of direction of conduction. The degree of fractionation of signals and of vector-loops of E increased with changing from longitudinal to transverse conduction (with respect to the fiber axis). With a new method to determine the individual directions of fractionated vector-loops of E produced by almost simultaneous events we were able to correlate the direction of the peaks of E with the complex microstructure found around the recording site.