BACKGROUND: A regional wall motion nonuniformity and a phase difference between LV posterior wall motion and transmitral flow are present during normal rapid filling period and are thought to be an evidence for involvement of ventricular restoring forces. To assess the role of nonuniformity on diastolic funtional impairment of asymmetric septal hypertrophy(ASH), the time relations between left ventricular regional wall motions and filling velocity were studied. METHOD: We measured the time intervals from A2 to peak rate of LV posterior wall(short axis) thinning(A2-(-)dpw/dt), peak rate of medial mitral annulus (long axis dimension) lengthening(A2-dL/dt) and peak mitral flow(A2-E) by M-mode and Doppler echocardiography. Result: In ASH patients, A2-(-)dpw/dt(106+/-6msec, mean SE) and the regional wall motion nonuniformity((-)dpw/dt-dL/dt, 89+/-11msec, mean SE) were increased significantly when compared with normal control values(88+/-4, 28+/-5msec, mean SE, p<0.01,respectively).In normal controls, peak mitral flow velocity lagged peak rate of regional wall motion, so the phase differences were present((-)dpw/dt-E :71+/-8msec, dL/dt-E:44+/-6msec). In ASH patients, (-)dpw/dt-E was present(90+/-16msec) but dL/dt-E was not present or reversed(-21+/-18 msec). So these chacteristic phase differences were disturbed. CONCLUSION: These data suggested that the relaxation nonuniformity of regional wall motion in ASH may act as an energy dissipating factor of restoring forces during rapid filling period.