Background: Biventricular pacing substantially improves LV systolic function and symptom status in some patients with dilated cardiomyopathy. Aims: To assess whether the long-term benefit could be predicted from the echocardiographic parameters. Methods and Results: Sixteen patients with dilated cardiomyopathy who underwent atrio-biventricular pacemaker implantation were analyzed in two groups: the responders (n = 11) were those with a symptomatic improvement of one or more NYHA functional class; the non-responders (n = 5) failed to improve at follow-up (7.6 +/- 5 months). Echocardiography was performed at baseline, the day after the implantation and then every 3 months. Besides the conventional parameters, the following variables were included: LV diastolic filling time (DFT); the duration of mitral regurgitation (dMR); and LV dP/dt obtained from the continuous wave mitral regurgitation curve. While the baseline DFT and dP/dt were not significantly different between non-responders and responders (256 +/- 105 vs. 358 +/- 115, P = 0.14 and 564 +/- 199 vs. 468 +/- 117, P = 0.44, respectively), the QRS width (149 +/- 15 vs. 175 +/- 24 ms, P = 0.05) and the dMR (343 +/- 70 vs. 443 +/- 49 ms, P = 0.007) were higher in the responders. The changes of dMR, DFT and QRS width by pacing were not significantly different between groups (P = 0.18, 0.30 and 0.77, respectively). However, the change of LV dP/dt by pacing in the responders was significantly different than for non-responders (from 468 +/- 117 to 676 +/- 216 mmHg/s vs. from 564 +/- 199 to 483 +/- 94, P = 0.002). An acute increase in LV dP/dt over 22% by pacing yielded only two false negatives and no false positives in predicting the long-term responsiveness. Conclusion: Patients with longer QRS and dMR are more likely to benefit from atrio-biventricular stimulation. The acute changes of Doppler derived LV dP/dt may provide valuable information in predicting the long-term response to biventricular pacing. (C) 2002 European Society of Cardiology. All rights reserved.