[Physiology of the heart valves].

Journal of cardiology. Supplement Pub Date : 1991-01-01
Y Nakamura
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Abstract

The function of healthy heart valves has been understood as the "on-off switch", which initiates and terminates blood flow in the cardiac cycle. It is believed that an impedance of the valves against blood flow is minimal and their closure is abrupt and complete. Clinically, an increase in impedance of the diseased valve is estimated by measuring pressure difference across that valve. However, the pressure gradient induced by acceleration of blood along the outflow tract of the ventricle or the artery during the early ejection phase, or along the inflow tract of the ventricle during the rapid filling phase can not be estimated separately from the pressure difference produced by valvular impedance in physiological state. Opening speed of the valve is related to the factors determining the velocity of blood flow. Mechanisms of a valve closure have been explained based on the Henderson and Johnson's concepts. Recent advances in ultrasonic technology can only confirm their concepts. Measurement of the pressure gradient across the semilunar valves in the late ejection phase has also several technical difficulties. Relationships among pressure, flow and valve motion have been extensively investigated, how-exact determination of the timing of the valve closure is not detected. The heart valves are considered to function as a passive organ throughout the cardiac cycle except for the atrioventricular valves including the subvalvular apparatus during systolic phase. The development of new methodology is necessary for the investigation of this field.

[心脏瓣膜的生理学]。
健康心脏瓣膜的功能被理解为“开关”,它启动和终止心脏循环中的血液流动。人们认为瓣膜对血流的阻抗是最小的,它们的关闭是突然和完全的。临床上,通过测量病变瓣膜的压差来估计瓣膜阻抗的增加。然而,在早期射血期沿心室流出道或动脉的血液加速引起的压力梯度,或在快速充盈期沿心室流入道的血液加速引起的压力梯度,不能单独与生理状态下瓣膜阻抗产生的压力差分开估计。阀门的开启速度与决定血流速度的因素有关。阀门关闭的机制已经根据亨德森和约翰逊的概念进行了解释。最近超声技术的进步只能证实他们的概念。在弹射后期测量半月阀的压力梯度也有一些技术上的困难。压力、流量和阀门运动之间的关系已经得到了广泛的研究,但如何精确确定阀门关闭的时间却没有被发现。心脏瓣膜在整个心脏周期中被认为是一个被动器官,除了在收缩期包括瓣下装置的房室瓣膜。发展新的研究方法对这一领域的研究是必要的。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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