Panel A: During spontaneous rhythm, a specific depolarization pattern of ventricles can be seen with the latest activation under leads V4-V6 and QRSd of 121 ms.
Panel B: During ns-HB capture on the annulus of the tricuspid valve with an HV interval of 52 ms, the pattern of ventricular depolarization was very similar to a spontaneous rhythm, with the latest activation under V4-V6. QRSd prolonged to 146 ms.
Panel C: During cSp, the tip of the pacing lead was placed approximately 14 mm below the plane of the tricuspid valve. Pacing in this location led to a minimal change in QRSd compared to a spontaneous rhythm, but the pattern of ventricular activation changed considerably. The first activated myocardial segments were under leads V1-V3, and the latest activation occurred simultaneously under leads V4-V8. The HV interval in this location was 40 ms.
Panel D: Placement of the pacing lead in the right ventricle following the signals of the right Tawara branch, with nonselective capture, led to prolongation of the LVLWd to 47 ms. The pattern of ventricular activation in this location was similar to cSp capture, but the delay between V1-V3 and V4-V8 was greater, and the activation under V4-V8 was less simultaneous. The HV interval was 28 ms.
Red dots show pacing lead positions. In panel C, the plane of the tricuspid valve is highlighted using a contrast agent; a white dashed line is used in panel B and D.