Ninety patients, 65 +/- 16 years, 32 with Narrow-QRS <120 ms and 58 with wide QRS >or=120 ms (Wide-QRS) CMP who met criteria for significant mechanical asynchrony by 15 criteria before CRT were studied. Responders were patients in whom end-systolic volume (ESV) reduced by >or=15% post-CRT. There was no difference in the response to CRT in the Narrow-QRS (ESV 132 +/- 60 to 120 +/- 60 mL, P = 0.02) or Wide-QRS (123 +/- 54 to 102 +/- 50 mL, P < 0.01) groups at 1 +/- 2 month follow-up. A difference of >or=40% in time to peak contraction in a cardiac cycle on tissue velocity imaging between the earliest and the most delayed segment had the best area under curve for response to CRT, 0.71 (0.55-0.85), P = 0.02. Using logistic regression model, delay in mid-posterolateral segment of >or=20% in a cardiac cycle compared with remaining 10 segments was the only predictor of response to CRT in the overall study population. Conclusion In patients with CMP and mechanical asynchrony by multiple criteria, response to CRT in Narrow-QRS group is similar to those with Wide-QRS. Greater than or equal to 40% delay in systolic contraction between 12 left ventricular (LV) segments or >or=20% delay of posterolateral segment to other LV segments predicted CRT response.