[Diastolic left ventricular pressure-mitral valve flow velocity curve: influence of heart rate change induced by atrial pacing].

Abstract

To assess the left ventricular (LV) diastolic properties, the influence of heart rate change induced by atrial pacing on LV pressure-mitral valve (MV) flow velocity curves was studied. Simultaneous recording of MV flow velocity using pulsed Doppler echocardiography and LV pressure via a catheter-tip micromanometer was performed in 12 cases with past history of Kawasaki disease. Heart rates were increased in gradations of 10 beats from rest to 180 beat/min, or to the time when A-V block occurred. Diastolic LV pressures and MV flow velocities were plotted manually every 10 msec to establish pressure-velocity relationships at each heart rate. The relationship of LV pressure and MV flow velocity was non-linear, and formed a loop. At rest, this loop showed counterclockwise rotation (CCR) in all cases. By increasing heart rate, rotation changed from CCR to clockwise rotation (CR), except in two cases. With much greater increase in heart rate, CCR reappeared in five cases (second CCR). CCR may indicate that the increment of MV flow is smaller than the fall in LV pressure in the early diastolic filling period, suggesting the existence of inflow resistance. This is thought to be physiologic, and it is suspected that it is produced mainly by the MV and subvalvular structures. CR indicates that the MV flow velocity increases more rapidly than the fall in LV pressure, demonstrating that the resistance to inflow is reduced by increasing heart rate, and the increment of left atrial (LA) driving pressure plays a main role. In a case with simultaneous recording of LA and LV pressures, LA pressure became elevated and the LA-LV pressure gradient increased with an increasing heart rate. This suggests that the increment of LA pressure relates to a decrease of inflow resistance. The second CCR suggests that a resistance is produced beyond a capacity to compensate for elevated LA pressure. It can be speculated that this resistance is related to visco-elasticity of the LV, in addition to the MV and subvalvular structures.