Color M-mode flow propagation velocity: is it really preload independent?

This study investigates the change in flow propagation velocity (FPV) in uremic patients who undergo regular hemodialysis (H/D).

We studied 93 uremic patients (44 men and 49 women; 59 +/- 14-years-old) receiving regular hemodialysis. Patients were separated by baseline left ventricular ejection fraction (LVEF): 71 patients with LVEF > 50% (group 1), 13 patients with LVEF 35-50% (group 2), 7 patients with LVEF < 35% (group 3). All patients were in sinus rhythm before H/D. They received complete transthoracic echocardiographic examinations. Flow propagation velocity was measured by color M-mode echocardiography in apical four chambers view. All these parameters were obtained before and after H/D. Paired data were compared. According to different H/D amounts, we viewed the FPV response after H/D in variant baseline LVEF groups.

The baseline FPV became lower in patients with low LVEF. After H/D, obvious decrement of FPV occurred in group 1, but there were no obvious changes in groups 2 and 3. In fact, a slight increment of FPV was found in group 3. In patients with baseline LVEF > 50%, FPV after H/D was almost always lower, regardless of H/D amount. But there was different response in patients with baseline LVEF < 50%.

Flow propagation velocity is preload independent in patients with LVEF < 50%, but it is preload-dependent in patients with LVEF > 50%.