BACKGROUND AND OBJECTIVES: Few studies have invasively assessed diastolic functional reserve and serial changes in left ventricular hemodynamics in euvolemic patients with exertional dyspnea. In this study, sequential changes in left ventricular end-diastolic pressure (LVEDP) to leg-raise exercise were measured invasively in patients with early heart failure with preserved ejection fraction (HFpEF) to determine the association between these serial changes and echocardiographic results or clinical features. SUBJECTS AND METHODS: During their hospital stay, 181 patients with early HFpEF underwent left cardiac catheterization, coronary angiography, and transthoracic echocardiography (TTE). Leg-raise exercise was performed in two stages: during cardiac catheterization and again during TTE. RESULTS: Compared with the initial values, all the invasively measured LVEDP values increased significantly during the leg-raise exercise, whereas the septal e/e' ratio remained unchanged. Active leg-raise led to increased LVEDP, which caused dyspnea. The severity of symptoms correlated with the level and extent of changes in LVEDP. At the end of active leg-raise, LVEDP decreased in 40 patients (22.1%), who were younger and had significantly lower e/e' ratios. On multivariate analysis to predict the response of LVEDP to active leg-raise, age and the septal e/e' ratio remained significant predictors. CONCLUSION: Despite having similar LVEDP values at rest, patients may respond to exercise with different LVEDP levels and clinical manifestations, depending on their diastolic capacity. The leg-raise exercise in early HFpEF can elucidate individual diastolic profiles, and the LVEDP response to the leg-raise test may serve as a useful criterion in stratifying patients with early HFpEF with respect to functional reserve.