Morphometry and Characterization of Electrograms in the Cavotricuspid Isthmus in Rabbit Hearts during Autonomic Sinus Rhythm

The cavotricuspid isthmus (CTI) in the right atrium is the origin of the most common type of atrial flutter (AFL) and therefore focus for arrhythmia research in anatomy and clinical electrophysiology. The impact of complexities and discontinuities of macro- and microstructure on the intercaval conduction in the subregions Crista Terminalis, Pectinate muscles and Vestibulum is little known in detail. Discontinuities of structure result in signals of non-uniform conduction with double or multiple deflections of signals indicating a fractionation of the depolarization wave. From experiments with 13 Rabbit hearts we analyzed topology and morphology of the CTI as well as the corresponding signal parameters taken at 1290 recording sites during sinus rhythm. A representative branching topology of the network of Pectinate muscles is described here with 4 proximal, 7 central and 4 sections. We found the largest portion of non-fractionated signals and of large signal amplitudes in Pectinate muscles, the highest portion of complex fractionated signals in the Vestibulum. The results allow to reconstruct a map of signal characteristic in detailed subregions of the CTI and to estimate the impact of macro- and microstructure on the activation sequence during sinus rhythm.