Zullo M A
New York Hospital-Cornell Medical Center, Cardiovascular Center, NY 10021.
Am Heart J. 1991 Jul;122(1 Pt 1):188-94. doi: 10.1016/0002-8703(91)90776-e.
The atria, strategically located at the junction of the venous and arterial circulation, contain a network of neural and humoral structures by which they sense and regulate intravascular volume. Atrial receptors, most commonly consisting of complex unencapsulated nerve endings discharging into myelinated vagal fibers, are located in the intrapericardial portions of the caval and pulmonary veins and the adjacent atrial walls. Receptor activation by atrial distension results in increased afferent vagal fiber discharge, which in turn leads to tachycardia (Bainbridge's reflex) and decreased renal sympathetic nerve activity, renal vasomotor tone, and antidiuretic hormone activity. In addition, atrial distension also releases ANF, a peptide with potent diuretic, natriuretic, and vasorelaxant actions. The combined effect of these neurohumoral changes is the production of a large hypotonic diuresis. In the clinical setting the volume-regulating role of the atria is demonstrated by the tachycardia-polyuria syndrome. Laboratory and clinical evidence points to the activation of atrial neurohumoral mechanisms in response to atrial distension as the mediators of the polyuria that often accompanies paroxysmal tachycardias. The involvement of these mechanisms in other forms of cardiac congestion and the capability to easily measure in the blood an index of atrial distension, namely ANF, provide the opportunity to elucidate the pathophysiology and hence to open new therapeutic avenues in many cardiac disorders.
心房位于静脉循环和动脉循环的交界处，位置关键，其内部包含神经和体液结构网络，借此感知并调节血管内容量。心房感受器最常见的构成是向有髓迷走神经纤维放电的复杂无被囊神经末梢，位于腔静脉、肺静脉的心包内部分以及相邻的心房壁。心房扩张激活感受器会导致迷走神经传入纤维放电增加，进而引发心动过速（贝恩布里奇反射），并降低肾交感神经活动、肾血管运动张力和抗利尿激素活性。此外，心房扩张还会释放心房钠尿肽，这是一种具有强效利尿、利钠和血管舒张作用的肽。这些神经体液变化的综合作用是产生大量低渗性利尿。在临床环境中，心动过速 - 多尿综合征证明了心房在容量调节方面的作用。实验室和临床证据表明，心房扩张时心房神经体液机制的激活是阵发性心动过速常伴随的多尿的介导因素。这些机制在其他形式的心脏充血中的参与情况，以及能够轻松在血液中测量心房扩张指标（即心房钠尿肽）的能力，为阐明病理生理学提供了机会，从而为许多心脏疾病开辟新的治疗途径。
