University of Amsterdam, Amsterdam UMC, Department of Medical Biology, Amsterdam Cardiovascular Sciences, Amsterdam, The Netherlands.
Department of Biology, Zoophysiology, Aarhus University, Aarhus, Denmark.
J Gen Physiol. 2022 Feb 7;154(2). doi: 10.1085/jgp.202012761. Epub 2021 Dec 15.
Ectothermic vertebrates experience daily changes in body temperature, and anecdotal observations suggest these changes affect ventricular repolarization such that the T-wave in the ECG changes polarity. Mammals, in contrast, can maintain stable body temperatures, and their ventricular repolarization is strongly modulated by changes in heart rate and by sympathetic nervous system activity. The aim of this study was to assess the role of body temperature, heart rate, and circulating catecholamines on local repolarization gradients in the ectothermic ball python (Python regius). We recorded body-surface electrocardiograms and performed open-chest high-resolution epicardial mapping while increasing body temperature in five pythons, in all of which there was a change in T-wave polarity. However, the vector of repolarization differed between individuals, and only a subset of leads revealed T-wave polarity change. RNA sequencing revealed regional differences related to adrenergic signaling. In one denervated and Ringer's solution-perfused heart, heating and elevated heart rates did not induce change in T-wave polarity, whereas noradrenaline did. Accordingly, electrocardiograms in eight awake pythons receiving intra-arterial infusion of the β-adrenergic receptor agonists adrenaline and isoproterenol revealed T-wave inversion in most individuals. Conversely, blocking the β-adrenergic receptors using propranolol prevented T-wave change during heating. Our findings indicate that changes in ventricular repolarization in ball pythons are caused by increased tone of the sympathetic nervous system, not by changes in temperature. Therefore, ventricular repolarization in both pythons and mammals is modulated by evolutionary conserved mechanisms involving catecholaminergic stimulation.
变温动物的体温会发生日常变化，一些传闻观察表明这些变化会影响心室复极，导致心电图中的 T 波改变极性。相比之下，哺乳动物能够维持稳定的体温，其心室复极受心率变化和交感神经系统活动的强烈调节。本研究旨在评估体温、心率和循环儿茶酚胺在变温球蟒（Python regius）中的局部复极梯度中的作用。我们在五条蟒蛇中记录体表心电图并进行开胸高分辨率心外膜映射，在所有这些情况下，T 波极性都发生了变化。然而，复极向量在个体之间存在差异，只有一部分导联显示 T 波极性改变。RNA 测序揭示了与肾上腺素能信号相关的区域差异。在一个去神经和林格氏液灌注的心脏中，加热和心率升高不会引起 T 波极性改变，而去甲肾上腺素则会引起改变。因此，在接受动脉内输注β-肾上腺素能受体激动剂肾上腺素和异丙肾上腺素的八只清醒蟒蛇的心电图中，大多数个体的 T 波反转。相反，使用普萘洛尔阻断β-肾上腺素受体可防止在加热过程中 T 波改变。我们的发现表明，球蟒心室复极的变化是由交感神经系统张力增加引起的，而不是由温度变化引起的。因此，无论是在蟒蛇还是哺乳动物中，心室复极都受到涉及儿茶酚胺刺激的进化保守机制的调节。
