We analyzed Doppler echocardiographic data in 120 subjects with normal sinus rhythm; normals (NL, n=60, ages 54.1±15.1) and essential hypertensive patients (HT, n=60, ages 57.3±10.2). The IMP was calculated as follows: IMP=(ICT+IRT)/ET, ICT; isovolumic contraction time, IRT; isovolumic relaxation time, ET; ejection time. There were no significant differences in ejection fraction (EF), stroke volume index (SVI), cardiac index (CI), ET and ICT between NL and HT. There were, however, significant differences in deceleration time (DT), E/A ratio, IRT and the IMP between the two groups (199.5±45.6 msec vs 222.3±54.3 msec, p<0.01; 1.4±0.7 vs 0.9±0.2, p<0.01; 113.6±30.2 msec vs 134.2±29.6 msec, p<0.01; 0.6±0.1 vs 0.8±0.3, p<0.05). In HT, there were no differences in EF, SVI, CI, E/A ratio and DT between the NYHA I (Gp I, n=36) and II (Gp II, n=24) groups. However, ET of Gp II was significantly shorter than that of Gp I (259.4±43.5 msec vs 297.8±33.6 msec, p<0.01). ICT, IRT and the IMP were significantly increased in Gp II, compared to those of Gp I (64.4±23.9 msec vs 89.4±46.2 msec, p<0.05; 120.3±21.0 msec vs 155.2±28.5 msec, p<0.001; 0.6±0.2 vs 1.0±0.4, p<0.001). There were no differences in heart rate and mean blood pressure between Gp I and Gp II (70.9±11.4/min vs 66.3±11.4/min, p>0.05; 138.4±21.2 mmHg vs 131.3±19.9 mmHg, p>0.05). These data suggest that the IMP may be a useful parameter and an early indicator of left ventricular dysfunction in essential hypertensive patients with normal systolic function.