Recently, biventricular (BIV) pacing has emerged as a means of achieving cardiac resynchronization, and improvement was thought to be proportional to the degree of QRS shortening. Tissue Doppler Imaging (TDI) seemed to be a better way for assessing LV synchrony by detecting the onset of systolic wave in the LV&the EMD can be measured.Aim :To assess the effect of BIV pacing on LV function and on EMD and to evaluate the role of TDI in pt selection and prediction of hemodynamic improvement.Methods : We studied 20 pts (3 Female, 17 Male, mean age 61.3±7.7 yrs) with advanced HF (NYHA class III, IV) and wide QRS. Implantation of either BIV pacemakers (PM) or BIV defibrillators was done in all pts. LV pacing was achieved epicardially via the coronary sinus in 17 pts or endocardially via trans-septal approach in 3 pts. Clinical evaluation and quality of life (QOL) assessment using the Minnesota score was done before implantation. Echocardiography and TDI were done 1 day after PM implantation initially with no pacing and then with BIV pacing. The echo-Doppler parameters assessed included LV dimensions (LVEDD, LVESD), EF using Simpson’s rule and mitral regurgitation (MR) area. TDI was used to assess the onset of systolic wave of the myocardial tissue Doppler in the septal, lateral, anterior and inferior walls. Echo-Doppler and clinical evaluation to determine the NYHA class, the Minnesota score and EF were repeated after 3 month.Results : Patients were subdivided into 2 groups according to the EMD calculated as the difference between the latest and the earliest walls to be activated.Group1 (13 pts with EMD > 60ms): Compared to non-BIV pacing, EF significantly improved (24.8±6.5 vs. 30.58±8.13, p= .0001) after BIV pacing with no significant acute changes in LV dimensions and no significant QRS shortening (188.5±30.8 vs. 172.3±24.2 ms, p= NS). EMD measured with TDI significantly decreased after BIV pacing (123.08 ±45.1 vs. 36.38±13.5 ms, p= .0001), MR area decreased also significantly (6.98±5.8 vs. 5.2±4.7, p= .032). After 3 month follow up, Compared to baseline data the Minnesota QOL Score significantly improved (47.38±15.6 vs. 32.62±10.39, p= .0001) and EF showed significant improvement (24.8±6.5 vs. 35.64±7.3, p= .01). NYHA class Improved with at least one class in 12 out of the 13 patients of this group.Group2 (7 pts with EMD < 60ms): Compared to non-BIV pacing; there was no significant change in the measured parameters except for the QOL score (53.85±15.8 vs43.43±16.2, p= .005).Conclusion: In patients with end stage CHF, BIV pacing can achieve hemodynamic improvement immediately and on short term follow up. EMD detected by TDI is an easy non-invasive method for patient selection. It can also serve as a predictor of subsequent patient improvement if it showed significant shortening on acute basis.