Calculation of left ventricular diastolic time constant(Tau) in dogs with aortic regurgitation using continuous-wave Doppler spectra

OBJECTIVE To investigate a new noninvasive method for calculating left ventricular diastolic time constant(Tau) through a continuous-wave aortic regurgitation Doppler spectrum.METHODS According to ultrasound guidance, twenty-four animal models(beagles) of aortic regurgitation and acute ischemic left ventricular diastolic dysfunction were created. The left ventricular diastolic function was manipulated with dobutamine or esmolol and fifty-nine hemodynamic stages were achieved. Raw audio signals of the continuous-wave Doppler spectra were collected, and new aortic regurgitation Doppler spectra were built after reprocessing by a personal computer. The updating time of the spectral line was 0.3 ms. The new Doppler spectra contour line was automated using MATLAB(MATrix LABoratory, MathWorks, Natick, MA, USA), and two time intervals,(t2–t1) and(t3–t1) were measured on the ascending branch of the aortic regurgitation Doppler spectrum. Then, the two time intervals were substituted into Bai's equations, and Doppler-derived Tau(Tau-D)was resolved and compared with catheter-derived Tau(Tau-c).RESULTS There is no significant difference between Tau-D and Tau-c(45.95 ± 16.90 ms and 46.81 ± 17.31 ms, respectively;P >0.05). Correlation analysis between Tau-c and Tau-D suggested a strong positive relationship(r = 0.97, P = 0.000). A Bland-Altman plot of Tau-c and Tau-D revealed fair agreement.CONCLUSIONS This new calculation method is simple, convenient, and shows a strong positive relationship and fair agreement with the catheter method.