OBJECTIVES: Our study attempted to validate a Doppler index of diastolic filling (E/E') during exercise with simultaneously measured left ventricular diastolic pressure (LVDP), investigate its association with exercise capacity, and understand which patients to select for testing. BACKGROUND: The ratio of early diastolic transmitral velocity to early diastolic tissue velocity approximates LVDP at rest, but there is limited validation of exercise E/E' with invasive hemodynamic measurement, and its clinical implications are unclear. METHODS: The ratio of early diastolic transmitral velocity to early diastolic tissue velocity was measured at rest and during supine cycle ergometry in 37 patients undergoing left heart catheterization. In addition to correlation between invasive and estimated LVDP, the accuracy of different cutoffs for identification of elevated LVDP (>15 mm Hg) was determined at both rest and exercise. Doppler index of diastolic filling was also measured at rest and immediately after maximal treadmill exercise in 166 patients to investigate the association between exercise E/E' and exercise capacity (<8 metabolic equivalents [METs]). RESULTS: In patients undergoing invasive measurement, nine (24%) had elevation of LVDP only during exercise. There was a good correlation between E/E' and LVDP at rest (r = 0.67) and during exercise (r = 0.59), and the regressions at rest and exercise corresponded closely. Receiver-operator curve analysis indicated that a cutoff value of 13 for exercise E/E' identified patients with an elevated LVDP during exercise. A post-exercise E/E' >13 was highly specific (90%) for reduced exercise capacity, and even after classification of resting E/E', exercise E/E' permitted classification of patients with exercise capacity <8 METs or > or =8 METs. CONCLUSIONS: The ratio of early diastolic transmitral velocity to early diastolic tissue velocity correlates with invasively measured LVDP during exercise. It can be used to reliably identify patients with elevated LVDP during exercise and reduced exercise capacity.