Thompson Loren P
Department of Obstetrics, Gynecology, and Reproductive Sciences, University of Maryland School of Medicine, Baltimore, MD, USA.
High Alt Med Biol. 2003 Summer;4(2):215-24. doi: 10.1089/152702903322022811.
This review examines the effect of high altitude and/or chronic hypoxia on cardiac mechanisms that influence perfusion of the fetal heart (e.g., tissue metabolism, coronary vessel growth, and coronary blood flow and vessel responsiveness). In response to intrauterine hypoxia, the fetal heart may either reduce its energy demand or increase its substrate and oxygen delivery as a means of sustaining cardiac function. Cardiac glycolysis predominates as a metabolic pathway of ATP synthesis in the fetal heart under both normoxic and hypoxic conditions. During prolonged oxygen insufficiency, normal cardiac function is sustained by anaerobic glycolysis relying primarily on high levels of stored glycogen in the heart. Chronic hypoxia increases coronary vessel growth and myocardial vascularization in fetal hearts, although the response may depend on the presence of ventricular hypertrophy. Recent studies demonstrate that high altitude hypoxia increases both resting fetal coronary flow and coronary flow reserve as an adaptive response toward increasing oxygen delivery. Hypoxia may also directly effect local vascular smooth muscle mechanisms, resulting in altered coronary artery reactivity to circulating vasoactive substances and contributing to enhanced perfusion. Further study is needed to understand the relative importance of each of these cardiac adaptations in contributing to fetal survival. It is likely that differences in fetal coronary responses to intrauterine hypoxia are highly dependent on the gestational age and relative maturity of the animal species.
本综述探讨了高海拔和/或慢性缺氧对影响胎儿心脏灌注的心脏机制的作用（例如，组织代谢、冠状动脉生长、冠状动脉血流及血管反应性）。为应对宫内缺氧，胎儿心脏可能会降低其能量需求，或增加其底物和氧气供应，以此维持心脏功能。在常氧和缺氧条件下，心脏糖酵解均是胎儿心脏中ATP合成的主要代谢途径。在长时间缺氧期间，心脏主要依靠高水平储存的糖原通过无氧糖酵解来维持正常心脏功能。慢性缺氧会增加胎儿心脏的冠状动脉生长和心肌血管生成，不过这种反应可能取决于心室肥大的存在。最近的研究表明，高海拔缺氧会增加胎儿静息冠状动脉血流和冠状动脉血流储备，作为对增加氧气供应的适应性反应。缺氧还可能直接影响局部血管平滑肌机制，导致冠状动脉对循环血管活性物质的反应性改变，并有助于增强灌注。需要进一步研究以了解这些心脏适应性变化各自对胎儿存活的相对重要性。胎儿冠状动脉对宫内缺氧的反应差异很可能高度依赖于动物物种的胎龄和相对成熟度。
