The phenomenon of concealed conduction in a case of His bundle pacing (HBP)

Figures

• 

  Figure 1.. Preoperative electrocardiogram shows 2: 1 atrioventricular block and complete left bundle branch block. The black arrows show P waves and the red arrows show QRS waves. Atrioventricular conduction is 2: 1. The QRS morphology of V1 is rS and that of V6 is RsR’, which represent left bundle branch block.

• 

  Figure 2.. Intraoperative intraluminal view shows the His bundle separation potential (white arrow). When atrioventricular block occurred, the conduction block was in the His bundle.

• 

  Figure 3.. During His bundle pacing, the rS wave of V1 leads became an rSR’ wave, and showed a pattern of continuous right bundle branch block and correction of complete left bundle branch block.

• 

  Figure 4.. Postoperative pacing electrocardiogram suggests correction of complete left bundle branch block. With His bundle pacing, the QRS wave in V1 leads is M-shaped (black arrow) and that in V5 and V6 leads is Rs (red arrow), which represent right bundle branch block along with disappearance of left bundle branch block.

• 

  Figure 5.. Fluoroscopic projection images. The left image was taken at the 45° left anterior oblique view and the right image was taken at the 30° right anterior oblique view.

• 

  Figure 6.. When the AV delay was prolonged, the pattern of right bundle branch block remained.

• 

  Figure 7.. When pacing was stopped, 2: 1 atrioventricular block with complete left bundle branch block occurred again.

• 

  Figure 8.. Schematic diagram. (a) Previous excitation generated a long refractory period through the right bundle branch, preventing the next excitation from being transmitted. (b) His bundle pacing induced left bundle branch excitation that could continue to produce concealed excitation of the right bundle branch. This prevented continuous transmission of upper excitation through the right bundle branch.