Effect of left ventricular size on early diastolic left ventricular filling in neonates and in adults.

Peak early diastolic left ventricular (LV) filling rate has been used as an index of LV diastolic function. However, it is known to be affected by LV size. Peak early diastolic transmitral flow velocity measured by pulsed Doppler echocardiography has also been proposed as a noninvasive method of assessing LV diastolic function. To determine if peak early diastolic mitral flow velocity also is influenced by LV size, 20 normal neonates (age 2 days) and 21 normal adults (mean age 38 years) were studied using pulsed Doppler echocardiography to measure mitral flow velocity and M-mode echocardiography to estimate LV end-diastolic volume and mitral valvular area. Peak early diastolic LV filling rate was calculated by multiplying peak early diastolic mitral flow velocity by mitral valvular area. Adults had significantly larger LV end-diastolic volumes (mean +/- standard deviation 108 +/- 25 vs 7 +/- 3 ml) and higher peak early diastolic LV filling rates (305 +/- 75 vs 29 +/- 10 ml/s) than neonates (both p less than 0.001). However, no significant difference was found in peak early diastolic mitral flow velocity between adults and neonates (61 +/- 10 vs 58 +/- 11 cm/s). These data suggest that peak early diastolic mitral flow velocity is independent of LV size. Since peak LV filling rate is equal to the product of peak mitral flow velocity and mitral valvular area, the correlation between peak early diastolic LV filling rate and LV size is probably due to differences in mitral valvular area rather than differences in peak mitral flow velocity.