Peak early diastolic filling velocity may decrease with preload augmentation: effect of concomitant increase in the rate of left atrial pressure drop in early diastole.
Doppler-determined transmitral flow velocity pattern has been shown to depend on transmitral pressure gradient, and left atrial (LA) pressure has been considered to be important in determining transmitral pressure gradient in early diastole and peak early diastolic filling velocity (E). In recent studies in human beings, however, it was proved that E did not necessarily change with LA pressure. This may be because concomitant changes in other factors masked the effect of LA pressure. To investigate the relation between transmitral flow velocity pattern and hemodynamic parameters during preload intervention over the wide range of LA pressure, pulsed Doppler transmitral flow velocity pattern and high-fidelity LA and left ventricular (LV) pressures were simultaneously recorded during rapid volume loading to the LA. Data at three stages, at control, at moderate volume loading (the median LA-to-LV crossover pressure during the volume loading), and at advanced volume loading (the maximal crossover pressure during the volume loading), were compared with one another in 11 dogs. A mean value of E increased with the crossover pressure up to moderate volume loading but did not further increase at advanced volume loading. In the data pooled from all experimental stages in all dogs, the changes in E did not correlate with those in the crossover pressure, but correlated weakly with those in the difference between the crossover pressure and LV minimum pressure (r = 0.45, p < 0.05). E decreased at advanced volume loading in three of 11 dogs with a steep LA pressure drop in early diastole although the changes in the difference between the crossover pressure and LV minimum pressure in the three dogs were similar to those in the other eight dogs. The changes in a rate of LA pressure drop in early diastole associated with advanced volume loading inversely correlated with those in E (r = -0.79, p < 0.01). Thus, E may decrease with an extreme increase in LA pressure; this change may be due to an associated increase in a rate of LA pressure drop in early diastole. This finding suggests that at high LA pressure the increased rate of LA pressure drop in early diastole appears to decrease LV filling and hence to reduce stroke volume.