Thomas J D, Weyman A E
Noninvasive Cardiac Laboratory, Massachusetts General Hospital, Boston 02114.
J Am Coll Cardiol. 1987 Oct;10(4):923-9. doi: 10.1016/s0735-1097(87)80290-5.
The Doppler determination of the mitral pressure half-time has gained widespread acceptance as a reliable estimate for mitral valve area, despite little theoretical basis for its "independence" of other hemodynamic variables. A simple model of the left atrium and mitral valve has been developed and a governing equation derived from fluid dynamics fundamentals. Solution of this equation indicates that the pressure half-time should vary inversely with mitral valve area, but also proportionally to net left atrial and ventricular compliance and to the square root of the peak transmitral gradient. This complex relation is apparently masked in the typical clinical situation because pressure and compliance tend to change in opposite directions, thereby partly offsetting each other. In several clinical settings, such as balloon mitral valvotomy, left ventricular hypertrophy and aortic regurgitation, changes in initial pressure and compliance may be large enough to alter the relation between mitral area and pressure half-time. This study reviews the development of the pressure half-time concept, presents an overall method for studying mitral valve flow using mathematical modeling and describes the effects of factors other than mitral valve area on pressure half-time.
尽管二尖瓣压力半衰期与其他血流动力学变量的“独立性”缺乏理论依据，但利用多普勒测定二尖瓣压力半衰期作为二尖瓣瓣口面积的可靠估计方法已被广泛接受。已建立了一个简单的左心房和二尖瓣模型，并从流体动力学基本原理推导出一个控制方程。该方程的解表明，压力半衰期应与二尖瓣瓣口面积成反比，但也与左心房和心室的净顺应性以及跨二尖瓣峰值压差的平方根成正比。在典型的临床情况下，这种复杂的关系显然被掩盖了，因为压力和顺应性往往呈相反方向变化，从而部分相互抵消。在一些临床情况下，如二尖瓣球囊成形术、左心室肥厚和主动脉瓣反流，初始压力和顺应性的变化可能足够大，足以改变二尖瓣瓣口面积与压力半衰期之间的关系。本研究回顾了压力半衰期概念的发展，提出了一种使用数学建模研究二尖瓣血流的总体方法，并描述了除二尖瓣瓣口面积外其他因素对压力半衰期的影响。
