Significance of doppler indices of diastolic filling of the left ventricle: Comparison with invasive hemodynamics in a canine model

Doppler measurements of mitral flow velocity curves have been proposed as a method for characterizing diastolic filling of the left ventricle. Different velocity curves have been empirically described in different disease states and under differing loading conditions in humans, but relating these various Doppler parameters to hemodynamic measurements of ventricular diastolic properties has not been fully elucidated. The effect of differing loading conditions (preload reduction, preload increase, afterload increase) on the Doppler mitral flow velocity and high-fidelity left atrial-left ventricular pressures was examined in seven closed-chest, anesthetized dogs. Preload reduction by balloon inflation in the inferior vena cave resulted in significant decreases in E velocity (early diastolic velocity) from 0.39 ± 0.09 m/sec to 0.29 ± 0.10 m/sec (p < 0.01) and prolongation of deceleration time from 131 ± 18 msec to 165 ± 60 msec (p < 0.05). Preload increase by infusion of fluids resulted in a significant increase in E velocity from 0.39 ± 0.09 m/sec to 0.49 ± 0.10 m/sec (p < 0.001) and shortening of the deceleration time from 131 ± 18 msec to 95 ± 15 msec (p < 0.001). The effect of afterload increase was variable and was dependent upon the left atrial pressure. Significant but weak positive correlations were noted between E velocity and maximal left atrial-left ventricular pressure gradient (r = 0.47, p < 0.001) and total change in left ventricular pressure (r = 0.68, p < 0.001), with inverse relationships between the deceleration time and these parameters. There was no overall relationship between the time constant tau and the E velocity, but an inverse relationship emerged when the data were examined according to different filling pressures. These results indicate that none of the mitral velocity measurements should be directly equated with other measurements of diastolic function. However, distinct velocity curves emerged under differing loading conditions that help in interpreting the meaning of these curves.