Determinants of left atrial systolic time intervals--assessment by pulsed Doppler echocardiography.

To evaluate the responsible factors for left atrial ejection, the left atrial preejection period (LAPEP), i.e., the time interval between atrial pacing pulse and onset of atrial ejection, and left atrial ejection time (LAET), i.e., the duration of atrial ejection, were determined from mitral inflow velocity patterns in 35 patients with various heart diseases using pulsed Doppler echocardiography. LAPEP ranged from 75 to 157 (mean 110 +/- 18) msec and LAET from 80 to 169 (mean 124 +/- 19) msec. The left atrial dimension before atrial contraction showed no significant correlation with LAPEP or LAET. Peak velocity during atrial contraction was negatively correlated with LAPEP (r = -0.42, p less than 0.05) and positively with LAET (r = 0.56, p less than 0.01). Left ventricular end-diastolic pressure (LVEDP) indicated a significant negative linear correlation with LAET (r = -0.44, p less than 0.05). LAPEP showed no significant linear correlation with LVEDP, but a significant curvilinear relationship was observed between them (LAPEP = 169 - 9.LVEDP + 0.28.LVEDP2, r = 0.63, p less than 0.001). Mean pulmonary capillary wedge pressure (mPCWP) was curvilinearly related to LAPEP (LAPEP = 168 - 11.mPCWP + 0.42.mPCWP2, r = 0.72, p less than 0.001) and LAET (111 + 4.1.mPCWP - 0.22.mPCWP2, r = 0.63, p less than 0.001). Although LAPEP decreased and LAET increased with increase in mPCWP up to about 15 mmHg, the reverse situation was noted for greater mPCWP. Thus, the major determinants of left atrial systolic time intervals are left atrial and ventricular pressures, and peak velocity during atrial contraction.