Puzzling pacing threshold in a patient with cardiac resynchronization therapy device

Song-yun Chu, Jing Zhou, Yan-sheng Ding

Figure 2. Comparison of the EGM and ECG during the procedure and after the initial implantation. A and B: testing of pacing thresholds of right ventricle and left ventricle with DDD-mode and shortened AV delay; C: the pseudocaptured QRS configuration was identical to the intrinsic LBBB pattern before the CRT implantation; D and E: EGM and ECG immediately after CRT implantation; F: EGM of intrinsic beats; G: so-called biventricular pacing capture. EGM: electrogram; ECG: electrocardiogram; AV: atrioventricular; LBBB: left bundle branch block; CRT: cardiac resynchronization therapy.