A case report of far-field P-wave oversensing in left bundle branch area pacing

Figures

• 

  Figure 1. A: Paced QRS morphology on the perioperative surface electrocardiogram confirming conduction system pacing with a V6 R-wave peak time of 85 ms, a V1 R-wave peak time of 135, and a V6-V1 inter-peak interval of 50 ms. B, C: Twelve-lead electrocardiogram before (B) and after (C) pacemaker implantation demonstrating a change from intrinsic right bundle branch block to a QRS morphology consistent with left posterior fascicular pacing.

• 

  Figure 2. A: Anteroposterior chest radiography showing stable lead positions. B: Holter tracing demonstrating total atrioventricular block with intermittent absence of ventricular pacing, suggesting ventricular oversensing. C: Intracardiac electrogram during a unipolar sensing test revealing episodes of ventricular oversensing owing to far-field sensing of atrial activity. A ventricular-sensed event (Vs) with an amplitude of 1.0–1.3 mV is seen, which coincides with an atrial-sensed event (As) at the moment of the P wave on the electrocardiogram, indicating far-field P-wave oversensing. This is followed by another ventricular-sensed event, which represents the true ventricular activity, evidenced by the concurrent QRS on the surface electrocardiogram and the change on the intracardiac electrogram. This is annotated as a refractory sensed event (Vrs) because it follows the erroneous Vs owing to P-wave oversensing.

• 

  Figure 3. Left anterior oblique cranial (A) and short-axis views (B) on cardiac computed tomography showing a lead tip position (arrow) 12 mm inferiorly from the insertion point of the septal leaflet of the tricuspid valve (asterisk) and in the posterior third of the interventricular septum.