We investigated the left ventricular (LV) systolic function and geometry in mitral valve replacement (MVR) with and without preservation of mitral apparatus. Five patients had conventional MVR without mitral annulus papillary muscle continuity (group C) and five patients had MVR with preservation of the continuity (group P). LV cineangiograms were assessed before and one month after surgery. LV volume was calculated by the method of Kennedy. Long axis dimension is defined as the distance between the apex and the center of mitral orifice in right anterior oblique projection. Short axis dimension is defined as the cross-sectional dimension at the middle point of the long axis. Paired Student's t tests were employed to compare the preoperative and postoperative data. LV ejection fraction decreased significantly from 69.4 +/- 9.5 to 51.8 +/- 10.5% in group C (p < 0.05) and did not change significantly in group P (from 51.6 +/- 19.9 to 56.8 +/- 12.9%). Fractional shortening of the long axis increased significantly from 15.0 +/- 11.8 to 21.2 +/- 14.0% in group P (p < 0.02) and did not change significantly in group C (from 16.5 +/- 8.6 to 13.1 +/- 3.3%). Ratio of LV end-systolic long axis to short axis dimension increased significantly from 1.76 +/- 0.31 to 2.12 +/- 0.21 in group C (p < 0.05) and did not change significantly in group P (from 1.90 +/- 0.22 to 1.95 +/- 0.22). We conclude that the ratio of systolic long to short axis increases, i.e., systolic LV shape changes to become longer and slender, and ejection fraction decreases after surgery in MVR without preservation of mitral apparatus. Conversely, preserving the mitral apparatus in MVR results in no significant change in systolic LV function and geometry, because of preserving fractional shortening of long axis.