Impact of preload alteration on left ventricular mechanical dyssynchrony using tissue velocity imaging...

We lack full understanding on the determinants of left ventricular (LV) systolic mechanical dyssynchrony. We here tried to evaluate the effect of preload alterations on LV dyssynchrony using echocardiographic tissue velocity imaging.

Thirty-eight patients with a history of heart failure who were in sinus rhythm (24 men, mean age of 61 ± 12 years [range, 26-82]) were consecutively recruited. Twenty-four patients were allocated into a mild diastolic dysfunction group (Gr 1), and 14 to an advanced diastolic dysfunction group, which included pseudonormalization or restrictive mitral inflow patterns (Gr 2). The leg-raising maneuver was performed for 5 minutes in Gr 1, whereas two tablets (1.2 mg) of sublingual nitroglycerin (SLNG) were given to Gr 2 to manipulate preload status. An index representing LV systolic mechanical dyssynchony (DYSsys) was defined as the maximal differences in time intervals from the QRS onset to the systolic peak velocities in 4 basal segments derived from the apical four- and two-chamber views.

DYSsys decreased significantly after SLNG administration (74.2 ± 50.2 vs. 46.9 ± 34.8 ms, P < 0.01), whereas it showed a significant elevation after leg-raising maneuver (76.3 ± 33.5 vs. 88.8 ± 37.5 ms, P < 0.05). Maximal difference in DYSsys between before and after SLNG administration in a patient of Gr 2 was estimated to be 120.2, whereas with the leg-raising maneuver, maximal difference in DYSsys in a patient of Gr 1 was found to be 66.8. Changes in heart rate induced by preload manipulation did not display any association with changes in DYSsys.

DYSsys is significantly affected by preload alterations, and thus it can be considered a "dynamic" parameter that could be modified depending on the loading status. Therefore, loading status of individual patients should be considered when DYSsys is assessed.