Accurately estimating left atrial (LA) volume with Doppler echocardiography remains challenging. Using angiography for validation, Marino et al. determined LA volume throughout the cardiac cycle by integrating the velocity-time integrals of Doppler transmitral and pulmonary venous flow, assuming constant mitral valve and pulmonary vein areas. However, this LA volume determination method has never been compared to three-dimensional LA volume data from cardiac magnetic resonance imaging (MRI), the gold standard for cardiac chamber volume measurement. Previously, we determined that the effective mitral valve area is not constant, but varies as a function of time. Therefore, we sought to determine whether the effective pulmonary vein area (EPVA) might be time-varying as well, and also assessed Marino's method for estimating LA volume. We imaged ten normal subjects using cardiac MRI and concomitant transthoracic Doppler echocardiography. LA and left ventricular (LV) volumes were measured by MRI; transmitral and pulmonary vein flows were measured by Doppler echocardiography; time dependence was synchronized via the electrocardiogram. LA volume, estimated using Marino's method, was compared to the MRI measurements. Differences were observed, and the discrepancy between the echocardiographic and MRI methods was used to predict EPVA as a function of time. EPVA was also directly measured from short-axis MRI images and was found to be time-varying in concordance with predicted values. We conclude that because EPVA and LA volume time-dependence are in-phase, LA filling in systole and LV filling in diastole are both facilitated. Application to subjects in select pathophysiologic states is in progress.