The cardiac electric field in psychrophilic and thermophilic fish during atrial depolarization

In psychrophilic and thermophilic fish, significant differences were revealed under an optimal body temperature in the heart rate, initial atrial activity duration and descending slope of the P _II wave. Differences were also detected in atrial electric activity during the initial and final periods of depolarization, reflecting different localization of the initial excitation area and the movement of the depolarization front toward the atrioventricular border.