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

Myocardial tissue Doppler echocardiography (TDE) has been proposed as a too l for the assessment of diastolic function. Controversy exists regarding wh ether TDE measurements are influenced by preload. In this study, left ventr icular volume and high-fidelity pressures were obtained in eight closed-che st dogs during intermittent caval occlusion. The time constant of isovolumi c ventricular relaxation (tau) was altered with varying doses of dobutamine and esmolol. Peak early diastolic myocardial (E-m) and transmitral (E) vel ocities were measured before and after preload reduction. The relative effe cts of changes in preload and relaxation were determined for E-m and compar ed with their effects on E. The following results were observed: caval occl usion significantly decreased E (DeltaE = 16.4 +/- 3.3 cm/s, 36.6 +/- 13.7% , P < 0.01) and E-m (<Delta>E-m = 1.3 +/- 0.4 cm/s, 32.5 +/- 26.1%, P < 0.0 1) under baseline conditions. However, preload reduction was similar for E under all lusitropic conditions (P = not significant), but these effects on E, decreased with worsening relaxation. At <tau> < 50 ms, changes in E, wi th preload reduction were significantly greater (<Delta>E-m = 2.8 +/- 0.6 c m/s) than at tau = 50-65 ms (DeltaE(m) = 1.2 +/- 0.2 cm/s) and at tau >65 m s (DeltaE(m) = 0.5 +/- 0.1 cm/s, P < 0.05). We concluded that TDE E-m is pr eload dependent. However, this effect decreases with worsening relaxation.