Discordant versus concordant T-wave in left bundle branch block patients undergoing cardiac resynchronization therapy

Background: Left bundle branch block (LBBB) might be associated with discordant T waves (W) (negative TW in leads I, V5, V6) or concordant TW where these TW are positive. Discordant TW represent more advanced repolarization abnormalities with epicardium repolarizing later than endocardium. We investigated if discordant versus concordant TW is associated with different clinical course and different response to cardiac resynchronization therapy (CRT). Methods: Baseline ECGs of 1,270 pts with LBBB who were enrolled in the MADIT-CRT trial were reviewed regarding presence of discordant versus concordant TW. Presence of discordant and concordant TW was evaluated in association with the study primary endpoint of heart failure event or death, CRT benefit, and secondary endpoint of VT/VF or death. Results: Discordant TW was identified in 909 (72%) pts whereas concordant TW were found in 361 (28%) pts. Discordant TW were associated with significantly increased risk of primary endpoint (Figure) and somewhat increased risk of VT/VF/Death (p=0.079). LBBB pts with concordant TW showed more pronounced reduction in the risk of cardiac endpoints (31% in ICD vs. 10% in CRT-D) than LBBB pts with discordant TW (32% in ICD arm vs. 18% in CRT-D arm): hazard ratio in concordant = 0.28 vs. 0.52 in discordant (p for interaction =0.06) Conclusions: Discordant TW in heart failure pts with LBBB indicate increased risk of cardiac events. Pts with concordant TW seem to derive somewhat more benefit from CRT than those with discordant TW. (Graph presented).