Left atrial filling in normal human subjects: relation between left atrial contraction and left atrial early filling

Relations between left atrial contraction and left atrial early filling were studied in eight subjects with atypical chest pain from simultaneous left atrial pressure recordings and left atrial cineangiograms. The left atrial ejection phase was defined as the interval from the onset of the sharp systolic rise in left atrial pressure (a point) to the point of minimum left atrial volume (Vmin). The left atrial filling phase was divided into (a) the early filling phase, the period from Vmin to the nadir of left atrial pressure (x), and (b) the late filling phase, the period from x to the point of maximum left atrial volume (Vmax). During the early filling phase, when the left atrium filled as left atrial pressure diminished, approximately 37% of total atrial filling took place. There was a direct relation between left atrial volume measured at a and x points (r = 0.91, p less than 0.01). The extension fraction, measured as the ratio of filling volume during the early filling phase to minimum left atrial volume, was significantly correlated with ejection fraction, measured as the ratio of ejected volume (delta V) during ejection phase to left atrial volume at the a point (r = 0.97, r = 0.01). Both mean and peak filling rates of left atrial volume change during the early filling phase were directly proportional to the ejected volume, the ejection fraction, and the mean ejection rate of left atrial volume change during the ejection phase. Thus these results suggest that there is close interaction between left atrial contraction and left atrial early filling.