Laboratory of Veterinary Physiology, Nihon University, Kanagawa, Japan.
Laboratory of Veterinary Biochemistry, Nihon University, Kanagawa, Japan.
J Vet Med Sci. 2023 Mar 1;85(3):334-339. doi: 10.1292/jvms.22-0367. Epub 2023 Jan 31.
Previous studies on dolphin electrocardiograms have shown that they are mainly composed of increased negative waves, similar to ungulates. The electrocardiogram waveform was determined by the distribution of the Purkinje fibers. Based on the waveform of the dolphin electrocardiogram, Hamlin predicted that the Purkinje fibers would be distributed within the ventricular muscle, as in ungulates. The purpose of this study was to confirm the histological distribution of Purkinje fibers in dolphins. In the present study, bottlenose dolphin hearts were observed both grossly and histologically, and the effects of Purkinje fiber distribution and cardiac morphology on electrocardiogram waveforms were examined. This study showed that the Purkinje fibers of dolphins run just below the endocardium, as in humans, dogs, and cats, whose electrocardiograms mainly show positive waves. When the cardiac morphology of dolphins was observed carefully, the right ventricle was found to be extremely dilated compared to that of terrestrial mammals. In human recreational divers, right ventricular dilatation is induced by diving. We hypothesized that the dolphin's heart is in a state similar to that of the right heart dilatation in terrestrial animals. The dolphin electrocardiogram waveform was considered to be due to right axis deviation. Based on the above, we concluded that the dolphin electrocardiogram waveform was due to its ability to live in water. We found that the dolphins are genetically related to ungulates, particularly the hippopotamus, but that their hearts have evolved differently.
先前对海豚心电图的研究表明，海豚的心电图主要由增强的负向波组成，与有蹄类动物相似。心电图的波形由浦肯野纤维的分布决定。基于海豚心电图的波形，Hamlin 预测浦肯野纤维会分布在心室肌内，就像有蹄类动物一样。本研究旨在确认海豚浦肯野纤维的组织学分布。在本研究中，我们对宽吻海豚的心脏进行了大体和组织学观察，并研究了浦肯野纤维分布和心脏形态对心电图波形的影响。本研究表明，海豚的浦肯野纤维像人类、狗和猫一样，就在心内膜下方运行，这些动物的心电图主要显示正向波。当仔细观察海豚的心脏形态时，我们发现与陆地哺乳动物相比，其右心室极度扩张。在人类休闲潜水员中，潜水会导致右心室扩张。我们假设海豚的心脏处于类似于陆地动物右心扩张的状态。海豚心电图的波形被认为是由于右轴偏离所致。基于以上结果，我们得出结论，海豚心电图的波形是由于其能够在水中生活所致。我们发现，海豚在基因上与有蹄类动物有关，特别是河马，但它们的心脏已经进化出不同的形态。
