Determinants of diastolic myocardial tissue Doppler velocities: Influences of relaxation and preload

Myocardial tissue Doppler echocardiography (TDE) has been proposed as a tool for the assessment of diastolic function. Controversy exists regarding whether TDE measurements are influenced by preload. In this study, left ventricular volume and high-fidelity pressures were obtained in eight closed-chest dogs during intermittent caval occlusion. The time constant of isovolumic ventricular relaxation (τ) was altered with varying doses of dobutamine and esmolol. Peak early diastolic myocardial (E_m) and transmitral (E) velocities were measured before and after preload reduction. The relative effects of changes in preload and relaxation were determined for E_m and compared with their effects on E. The following results were observed: caval occlusion significantly decreased E (ΔE = 16.4 ± 3.3 cm/s, 36.6 ± 13.7%, P < 0.01) and E_m (ΔE_m = 1.3 ± 0.4 cm/s, 32.5 ± 26.1%,P < 0.01) under baseline conditions. However, preload reduction was similar for E under all lusitropic conditions (P = not significant), but these effects on E_m decreased with worsening relaxation. At τ < 50 ms, changes in E_m with preload reduction were significantly greater (ΔE_m = 2.8 ± 0.6 cm/s) than at τ= 50-65 ms (ΔE_m = 1.2 ± 0.2 cm/s) and at τ>65 ms (ΔE_m = 0.5 ± 0.1 cm/s, P < 0.05). We concluded that TDE E_m is preload dependent. However, this effect decreases with worsening relaxation.