Background: Abnormalities of the left ventricular (LV) diastolic function are common in patients with hypertrophic cardiomyopathy (HCM). In patients with diastolic dysfunction, the abnormal relaxation velocity-versus-heart rate relationship prevents augmentation of relaxation velocity as heart rate increases during exercise. Doppler tissue imaging (DTI) has been introduced as a method to evaluate diastolic function or myocardial relaxation by measuring mitral annulus velocity during diastole. We hypothesized that augmentation of myocardial relaxation during exercise would be blunted in patients with HCM. Methods and Results: Mitral inflow and septal mitral annular velocities were measured at rest and during graded supine bicycle exercise (25W, 3 minutes increments) in 20 patients (16 male, mean age 56 years) with HCM and 29 patients (7 male, mean age 58 years) with control. There were no significant differences in mitral inflow velocities (E, E/A, DT) between the two groups except A velocity, which was higher in control group. However, early diastolic mitral annular velocity (E���) at rest and change of E��� with exercise was significantly lower in patients with HCM compared with control (figure). In conclusion, augmentation of myocardial relaxation during exercise, assessed with early diastolic mitral annular velocity, is blunted in patients with HCM, suggesting resting diastolic function as well as longitudinal diastolic functional reserve is abnormal in these patients.