Tissue Doppler velocity is not totally preload-independent: a study in a uremic population after hemodialysis

The aim of this study was to investigate the changes of regional tissue Doppler velocity after volume removal following regular hemodialysis (HD) in uremic patients. Is tissue Doppler velocity really preload-independent?

Diastolic dysfunction was divided into four stages: normal pattern, abnormal relaxation pattern, pseudonormalization pattern, and restrictive pattern. Pulse wave Doppler and color Doppler echocardiography were important diagnostic tools for these forms of diastolic dysfunction. However, they were preload-dependent and sometimes there was confusion between the normal pattern and the pseudonormalization pattern. Tissue Doppler echocardiography was promising for problems in diastolic dysfunction and appeared to be preload-independent. However, there are still some disputes over this point.

Ninety-three uremic patients receiving regular HD were included in the study. There were 45 males and 48 females aged 59 +/- 14 years. The mean volume removed after HD was 2.3 +/- 0.9 kg. The mean heart rates before and after HD were 77 +/- 11 and 76 +/- 12 beats per minute, respectively (p = 0.73). All patients received complete transthoracic echocardiography examinations before and after HD. The studies included cardiac chamber size, left ventricular systolic performance, pulse wave Doppler echocardiographic data of mitral inflow and the right upper pulmonary vein including peak velocity of early diastolic E wave, E wave time velocity integral (TVI-E), peak velocity of late diastolic A wave, A wave TVI, systolic phase of pulmonary vein (S wave TVI), early diastolic phase of pulmonary vein (D wave TVI) and atrial contraction phase of pulmonary vein (Ar wave TVI). Pulsed tissue Doppler echocardiography (TDE) was performed and a 4-mm sample volume was placed at the 6 corners of the mitral annulus including septal, lateral, anterior, inferior, anteroseptal and posterior corners. Five to ten cardiac cycles were recorded and the data were averaged. Measurements performed included peak velocity of systolic phase (Sa), early diastolic phase (Ea), late diastolic phase (Aa), Ea/Aa ratio and time from the beginning of electrocardiogram Q wave to the beginning of Sa (Q-Sa time). The same measurements were repeated after HD.

After HD, left atrium diameter and left ventricular internal dimensions at end diastole became smaller. There were significant reductions for mitral peak E wave velocity, TVI-E, peak A wave velocity and E/A ratio. As for the pulmonary vein, systolic phase of pulmonary vein and early diastolic phase of pulmonary vein decreased significantly. Peak Ar wave did not change significantly. For TDE, Sa and Aa did not change but Ea did decrease.

After HD, there is a significant reduction of intravascular effective volume. No significant change is found for myocardial peak systolic velocity and peak late diastolic velocity. However, there is a significant reduction of myocardial early diastolic phase peak velocity. This suggests that TDE is not completely preload-independent; at least, it is phase-dependent within each cardiac cycle.