Transient left bundle branch block due to massive increase of His bundle pacing threshold associated with acute heart failure in a patient with complete heart block

Figures

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  Figure 1. A: Baseline electrocardiogram (ECG) showing complete heart block (CHB) with right bundle branch block and left anterior fascicular block morphology escape rhythm. Precordial abnormal Q waves are also noted, suggesting old anterior myocardial infarction. B: Baseline ECG at the time of the first procedure, showing CHB with left bundle branch block (LBBB) morphology escape rhythm. C: Intracardiac electrograms demonstrating His-ventricle block. D: Intraoperative ECG at the final successful site. Pacing at 2.0 V @ 1 ms and above resulted in nonselective His bundle pacing (NS-HBP). Left bundle, right ventricle, and right bundle capture was lost at 1.9 V @ 1 ms, 1.1 V @ 1 ms, and 0.4 V @ 1 ms, respectively. NS-RBP = nonselective right bundle pacing; S-RBP = selective right bundle pacing.

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  Figure 2. A: Fluoroscopic image (right anterior oblique projection) at the time of lead revision, showing a new His bundle pacing (HBP) lead placed slightly proximal and inferior to the original lead. B: Intracardiac electrograms after a new lead fixation, showing distal HB potential with HB injury current (arrows). C: Intraoperative electrocardiogram at the successful site. Pacing at 1.6 V and above results in nonselective HBP (NS-HBP). Below 1.5 V, there is selective HB capture (S-HBP). At pacing output 0.6 V @ 1 ms, selective right bundle capture is seen just before loss of capture (right panel).

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  Figure 3. A: Electrocardiogram (ECG) at admission for acute heart failure, showing selective His bundle pacing (HBP) without correction of left bundle branch block because of an acute increase in the His bundle (left bundle) pacing threshold to 3.75 V @ 1 ms and programmed output setting at 3.0 V @ 1 ms. B: ECG at 1 year after last discharge, showing selective HBP with stable HBP threshold of 0.5 V @ 1 ms.