Background and Objectives:The degree of diastolic dysfunction may explain the difference in clinical sym- ptoms between patients with similar degrees of systolic dysfunction. Pseudonormal mitral filling pattern with increased left ventricular filling pressure is a transitional stage of diastolic dysfunction and is difficult to distin- guish from normal. Preload is one of factors affecting the diastolic filling patterns and mitral flow patterns may be influenced by changes in preload in the absence of changes in the left ventricular pressure-volume curve. The changes in the mitral flow velocities caused by preload reduction may be useful in distinguishing patients with a pseudonormal pattern from those with normal. The aim of this study was to establish whether the effect of changes in pulmonary venous flow pattern by preload reduction may be useful in distinguishing pseudonormal pattern from normal. Materials and Methods:This study included 40 patients (men 25, female 15, average age 51.0±11.2 years underwent left side cardiac catheterization among patients with normal or pseudonormal patterns. All patients with pseudonormal group had increased LVEDPr (>15 mmHg. The Doppler mitral inflow & pulmonary venous flow parameters at baseline and during reduction of preload using Valsalva maneuver were recorded. Results:1 There were no difference in sex, diabetes mellitus, hypertension and lipid profiles between both groups. The left ventricular systolic function was better and mean age was younger in normal than pseudonormal group (p 1.0 during Valsalva maneuver in normal group (p<0.05. In pseudonormal group, E velocity was significantly decreased but A velocity was not significantly changed and the E/A ratio was <1.0 during Valsalva (p<0.05. Therefore the change revealed masked LV relaxation abnormality pattern. 3 S and D velocities of pulmonary venous flow were significantly decreased and S/D ratio was significantly increased in both groups (p<0.05. The % changes before and after Valsalva maneuver showed that S velocity was less decreased, D velocity was more decreased and S/D ratio was more significantly increased in pseudonormal than normal group (p<0.05. That revealed masked LV relaxation abnormality pattern. Conclusione:The