Scalia G M, Greenberg N L, McCarthy P M, Thomas J D, Vandervoort P M
Department of Cardiology, Cleveland, Clinic Foundation, OH 44195, USA.
Circulation. 1997 Jan 7;95(1):151-5. doi: 10.1161/01.cir.95.1.151.
The time constant of ventricular relaxation (tau) is a quantitative measure of diastolic performance requiring intraventricular pressure recording. This study validates in humans an equation relating tau to left ventricular pressure at peak -dP/dt (P0), pressure at mitral valve opening (PMV), and isovolumic relaxation time (IVRTinv). The clinically obtainable parameters peak systolic blood pressure (Ps), mean left atrial pressure (PLA), and Doppler-derived IVRT (IVRTDopp) are then substituted into this equation to obtain tau Dopp noninvasively.
High-fidelity left atrial and left ventricular pressure recordings with simultaneous Doppler by transesophageal echocardiography were obtained from 11 patients during cardiac surgery. Direct curve fitting to the left ventricular pressure trace by Levenberg-Marquardt regression assuming a zero asymptote generated tau LM, the "gold standard" against which tau calc (IVRT inv/[ln(P0)-ln(PMV)]) and tau Dopp [IVRTDopp/[ln(Ps)-ln(PLA)]] were compared. For 123 cycles analyzed in 18 hemodynamic states, mean tau LM was 53.8 +/- 12.9 ms. tau calc (51.5 +/- 11 ms) correlated closely with this standard (r = .87, SEE = 5.5 ms). Noninvasive tau Dopp (43.8 +/- 11 ms) underestimated tau LM but exhibited close linear correlation (n = 88, r = .75, SEE = 7.5 ms). Substituting PLA = 10 mm Hg into the equation yielded tau 10 (48.7 +/- 15 ms), which also closely correlated with the standard (r = .62, SEE = 11.6 ms).
The previously obtained analytical expression relating IVRT, invasive pressures, and tau is valid in humans. Furthermore, a more clinically obtainable, noninvasive method of obtaining tau also closely predicts this important measure of diastolic function.
心室舒张时间常数（tau）是舒张功能的一项定量指标，需要记录心室内压。本研究在人体中验证了一个将tau与左心室压力峰值-dP/dt（P0）、二尖瓣开放时的压力（PMV）以及等容舒张时间（IVRTinv）相关联的方程。然后将临床上可获取的参数收缩压峰值（Ps）、平均左心房压力（PLA）以及多普勒衍生的IVRT（IVRTDopp）代入该方程，以无创地获得tau Dopp。
在心脏手术期间，通过经食管超声心动图对11例患者进行了高保真左心房和左心室压力记录，并同步进行多普勒检查。采用Levenberg-Marquardt回归法对左心室压力曲线进行直接拟合，假设渐近线为零，得出tau LM，它是用于比较tau calc（IVRT inv/[ln(P0)-ln(PMV)]）和tau Dopp [IVRTDopp/[ln(Ps)-ln(PLA)]]的“金标准”。在18种血流动力学状态下分析的123个心动周期中，平均tau LM为53.8±12.9毫秒。tau calc（51.5±11毫秒）与该标准密切相关（r = 0.87，标准误 = 5.5毫秒）。无创的tau Dopp（43.8±11毫秒）低估了tau LM，但呈现出密切的线性相关性（n = 88，r = 0.75，标准误 = 7.5毫秒）。将PLA = 10毫米汞柱代入方程得出tau 10（48.7±15毫秒），它也与标准密切相关（r = 0.62，标准误 = 11.6毫秒）。
先前获得的将IVRT、有创压力和tau相关联的分析表达式在人体中是有效的。此外，一种更易于临床获取的无创获取tau的方法也能紧密预测这一重要的舒张功能指标。
