目的 探讨采用二尖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.方法 9只健康成年比格犬,超声引导下经颈动脉鞘管采用活检钳钳夹二尖瓣腱索制作犬二尖瓣反流模型;超声引导下,经颈动脉鞘管将三聚氰胺微球溶液注射于左冠状动脉窦内,微栓塞冠状动脉,以左心室舒张末压升高≥5 mmHg(l mmHg=0.133 kPa)为标准,诱发急性缺血性左心室舒张功能障碍;静脉滴注多巴酚丁胺或盐酸艾司洛尔,改变血流动力学状态.在不同血流动力学状态下,超声采集二尖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、dP/dt曲线、左心房压力曲线、心电图.Matlab软件处理并形成新的二尖瓣反流频谱(频线刷新速度300 μs)、自动生成包络线、测量频谱减速支中速度分别为1、2、3 m/s的时间t1、t2、t3,代入相应公式计算Tau超声.根据Weiss公式采用导管法测量指标计算Tau导管.采用配对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.结果 共获得39个不同血流动力学状态下的反流频谱进行分析.Tau导管为21.03~78.45 ms,平均为(48.76±17.60) ms;Tau超声为21.24~94.60 ms,平均为(49.33±18.79) ms,两者差异无统计学意义(t=0.353,P=0.726).Pearson相关分析结果显示,Tau导管与Tau超声呈正相关(r=0.85,P<0.01).结论 通过测量二尖瓣反流连续多普勒频谱减速支中速度分别为1、2、3 m/s的时间t1、t2、t3,代入相应Tau计算公式即可计算Tau,与导管法比较具有良好相关性.
Objective To explore the new method for noninvasively measuring the time constant of left ventricular relaxation (Tau) in animals with mitral regurgitation by continuous-wave Doppler.Methods The acute ischaemic left diastolic heart failure with mitral regurgitation was produced in 9 dogs.Dobutamine hydrochloride or esmolol hydrochloride had been applied to change the hemodynamic states.In different hemodynamic states,left ventricular pressures,left atrial pressures,curves of dP/dt and continuous-wave mitral regurgitant spectra were synchronously recorded.Doppler spectra were laterly processed through Matlab workstation.Paired t-test was used to compare the difference between Tau-catheter (Tau-c) and Tau-doppler ultrasound (Tau-d),and the correlation between Tau-c and Tau-d was analyzed by Pearson correlation analysis.Results Thirty-nine hemodynamic status had been obtained in 9 dogs.Tau-c was 21.03-78.45 ms and the average was (48.76± 17.60) ms.Tau-d was 21.24-94.60 ms and the average was (49.33 ± 18.79) ms.There was no significant difference (t=0.353,P=0.726) between Tau-d and Tau-c.The correlation analysis between Tau-d and Tau-c suggested a strong positive relationship with the correlation coefficient (r=0.85,P < 0.001).Conclusions The dog aortic regurgitation model under ultrasound guidance is less traumatic.The method of inducing left ventricular diastolic dysfunction by repeatedly injecting microspheres into the left coronary sinus is safe and reliable.Choosing three points (t1,1 m/s;t2,2 m/s;t3,3 m/s) in aortic regurgitant velocity spectrum and putting them into the corresponding formula,we can obtain Tau,which had a good correlation with the catheter-derived Tau.