Dolphin hearts have the same characteristics as human

Previous studies of dolphin electrocardiograms showed that they are mainly composed of increased negative waves similar to ungulates. The electrocardiogram waveform is determined by the distribution of the location of the Purkinje fibers. Based on the waveform of the dolphin electrocardiogram, Hamlin predicted that the distribution of Purkinje fibers would be within the ventricular muscle, as in ungulates. In this study, bottlenose dolphin heart were observed both visually and histologically, and the effects of Purkinje fiber distribution and cardiac morphology on electrocardiogram waveforms were considered. This study showed that the Purkinje fibers of dolphins run just below the endocardium as in humans, dogs, and cats, whose electrocardiograms show mainly positive waves. When the cardiac morphology of dolphins was observed carefully again, the right ventricle was extremely dilated compared to terrestrial mammals. In human recreational divers, right ventricular dilatation is induced by diving. We hypothesized that the dolphin’s heart is in a similar state to that of right heart dilatation in terrestrial animals. The dolphin electrocardiogram waveform is considered to be due to right axis deviation. Based on the above, we concluded that the dolphin electrocardiogram waveform was due to its living in water. We found that the dolphin is genetically related to the ungulates, especially the hippopotamus, but that their hearts have evolved differently.