探讨采用主动脉瓣反流连续多普勒频谱评价左心室松弛时间常数Tau的新方法。

12只健康成年比格犬，超声引导下经颈动脉介入制作主动脉瓣反流模型；压力导管测量升主动脉压力，由心尖处插入Millar测压导管至左心室测量左心室压；在超声引导下，反复间断将塑料微球悬液注入左冠状动脉窦，微栓塞冠状动脉，以左心室舒张末压升高≥5 mmHg（1 mmHg=0.133 kPa）为标准，诱发急性缺血性左心室功能障碍；静脉滴注多巴酚丁胺或艾司洛尔改变左心室功能，制造不同的血流动力学状态。在不同血流动力学状态下，采集主动脉瓣反流连续多普勒频谱及其原始音频信号，多导生理仪同步记录左心室压力曲线及其dp/dt曲线、主动脉压力曲线、心电图。测量-dp/dtmax大小及其所处时刻的左心室压力P，根据Weiss公式Tau= P/（-dp/dtmax），计算导管法测量的Tau（Tau_导管）。通过MATLAB后处理软件以每300 μs刷新一条频谱线的速度对主动脉瓣反流频谱原始音频数据进行后处理，在后处理的主动脉瓣反流频谱曲线上选取1、2、3 m/s速度点的时间值t1、t2、t3，带入相应Tau计算公式Tau=（t2-t1）/ln[（ADP-C-4）/（ADP-C-36）]和Tau=（t3-t1）/ln[（ADP-C-4）/（ADP-C-36）]，计算超声法测量的Tau（Tau_超声）。用配对t检验比较Tau_导管与Tau_超声的差异；采用Pearson相关分析分析Tau_导管与Tau_超声的相关性。

12只犬全部成功制作主动脉瓣反流模型。2只犬在急性缺血左心室舒张功能障碍模型制作过程中死于室颤。Tau_导管为27.12~86.88 ms，平均为（48.973± 14.667）ms；Tau_超声为28.13~90.18 ms，平均为（51.236±15.146）ms；两者差异无统计学意义（t=1.841，P>0.05）。Pearson相关分析结果显示，Tau_导管与Tau_超声呈正相关（r=0.89，P<0.01）。

测量主动脉瓣反流连续多普勒频谱上升支速度为1、2、3 m/s的时间t1、t2、t3，带入相应Tau公式即可计算出Tau，与导管法比较具有良好相关性。

To find a new method for evaluating the left ventricular relaxation time constant Tau with aortic regurgitation by continuous wave Doppler.

Twelve Beagle dogs were included in the study. The dog aortic regurgitation model was produced under ultrasound guiding by carotid artery puncture. Aortic pressure was measured by pressure catheter and left ventricular pressure was measured by Millar catheter which was introduced into the left ventricular through cardiac apex. Then microspheres were injected into the left coronary artery under the guidance of ultrasound to induce acute ischemic left ventricular dysfunction, when left ventricular end-diastolic pressure increased more than 5 mmHg (1 mmHg=0.133 kPa). Dobutamine or esmolol was infused to alter left ventricular function. Aortic regurgitation velocity spectrum was recorded by the continuous-wave Doppler echocardiography in different hemodynamic status. At the same time, left ventricular pressure, dp/dt, aortic pressure and continuous ECG tracing were displayed on the multi-channel physiological recorder. Measurement was recorded of –dp/dtmax in the dp/dt tracings and the pressure at the time of –dp/dtmax in the left ventricular pressure tracings. Tau =-P/(dp/dtmax), Tau was the catheter-derived time constant (Tau_catheter). Aortic regurgitation spectrum of original audio data was post-processed with MATLAB mathematical software. The spectral lines refresh time of about 300 μs was chosen to form a new Doppler spectrum. Three points: (t1,1 m/s), (t2, 2 m/s) and (t3, 3 m/s) were selected in aortic regurgitation velocity spectrum and t1, t2 and t3 was put into the corresponding Tau formula: Tau=(t2-t1)/ln[(ADP-C-4)/(ADP-C-16)], Tau=(t3-t1)/ln[(ADP-C-4)/(ADP-C-36)]. Tau was the aortic regurgitant time constant (Tau_ultrasound). The difference between Tau_catheter and Tau_ultrasound was compared by paired t test. The correlation between Tau_catheter and Tau_ultrasound was analyzed by Pearson correlation analysis.

Twelve dogs were successfully produced aortic regurgitation model. Two dogs died of ventricular fibrillation during the procedure of acute ischemic left ventricular diastolic dysfunction. The range of the Tau_catheter was between 27.12 ms and 86.88 ms with an average of (48.973±14.667) ms; the range of the Tau_ultrasound was between 28.13 ms and 90.18 ms with an average of (51.236±15.146) ms. The difference was not statistically significant (t=1.841, P>0.05). Pearson correlation analysis showed that Tau_catheter was positively correlated with Tau_ultrasound (r=0.89, P=0.000).

Choosing three points: (t1, 1 m/s), (t2, 2 m/s) and (t3, 3 m/s) in aortic regurgitant velocity spectrum and putting into the corresponding formula, we can calculate Tau, which had a good correlation with the catheter-derived Tau.