[The comparative characteristics of the heart rhythm in cetaceans].

In Amazon River dolphins, bottle-nosed dolphins and white whales, comparative studies have been made on cardiac electrical activity using electrocardiographic and telemetric techniques. In all the species investigated, certain dependence of cardiac cycle duration on the phase of respiratory pause was observed. A pronounced bradycardia was noted in diving animals which reflects the level of their adaptation to hypoxia and hypoxemia. Autocorrelation functions of the dynamic sequences of cardiac intervals were calculated. The presence of "slow" waves in cardiac cycle was shown which were considerably increased during diving.