Improvement in early diastolic filling dynamics after aortic valve replacement. With use of ultrafast computed tomography, 13 patients undergoing aortic valve replacement for aortic stenosis were prospectively followed to evaluate the relation between left ventricular mass and diastolic function. Studies were done before intervention, and then at 4 and 8 months later. Mass decreased from 161 +/- 11 g/m2 (+/- standard error of the mean) at baseline to 106 +/- 5 g/m2, and then to 97 +/- 7 g/m2 at 4 and 8 months, respectively, in 12 patients who demonstrated significant (greater than 20%) mass regression after operation. One patient failed to show significant changes in mass. Diastolic function, as defined by the peak filling rate of early diastole, improved (p less than 0.02) in the group with mass regression, from 2.11 +/- 0.17 s-1 at baseline to 2.12 +/- 0.23 s-1, and then to 2.62 +/- 0.26 s-1 at 4 and 8 months, respectively. Improvement in the time to peak filling rate was also noted. Heart rates were unchanged, whereas end-diastolic volumes decreased and ejection fractions increased slightly. Postoperative increase in peak filling rate correlated with regression of ventricular mass to within normal range (+/- 2 standard deviations) and attainment of New York Heart Association class I status by 8 months (p less than 0.02). Thus, improvement in diastolic function can be seen after aortic valve surgery and is associated with improved functional class. Diastolic function improves later than the regression in wall mass and may imply a delayed remodeling of the ventricle. 