gms | German Medical Science

Question: The study of the relationships between epicardial depolarization and repolarization sequences and BSPD in fish and amphibians having simple ventricular activation patterns will clarify the mechanism of BSPD development.

Method used: Potential mapping was done in frogs (n=16) and pikes (n=12) using 32 body surface and 24 epicardial electrodes. BSPDs were studied and ventricular epicardial activation and repolarization sequences were determined.

Results: In pikes, the earliest epicardial depolarization was observed in the ventricular base. The latest activation areas were near the apex and at the arterial cone. The earliest repolarization was found in the apical area and the latest one – at the ventricular base. In the first third of the QRS, positive potentials were recorded cranially on the ventral body surface, and negative ones – on the rest surface. In the second third of the QRS, positive potential area extended caudally and ventral-dorsal BSPD developed. In the final QRS portion, the negative potentials were observed cranially and positive ones – caudally. In the T wave period the negative potentials were confined to the most cranial portion whereas positive potentials were recorded on the remainder body. In frogs, the epicardial excitation sequence is characterized by the spread of activation from the posterior base to the apex and anterior base. The heart apex was the first to and the base was the latest to be repolarized. Prior to the R peak a dorsal-ventral (negative-positive, respectively) BSPD developed. After the R peak the BSPD became cranial-caudal (positive-negative, respectively). During the T wave period a BSPD with the cranial-ventral negative area and wide caudal-dorsal positive area developed.

Conclusion: Thus, in spite of the differences in BSPDs during the QRS, the BSPDs during the T wave are rather similar in frogs and pikes. This resemblance is based on the similarities in epicardial recovery sequences in the both species.