Table 2: Electrical Responses in His Bundle Pacing for Broad Intrinsic QRS.
| Intrinsic QRS | Degree of BBB correction | His Bundle Pacing | |
|---|---|---|---|
| LBBB | Full correction |
S-HBP Normal QRS appearance (no BBB morphology) Stim-QRSend < H-QRSend paced QRSd < 120 ms < intrinsic QRSd |
NS-HBP Pre-excited normal QRS appearance (no BBB morphology) Stim-QRSend usually < H-QRSend paced QRSd >120 ms paced QRSd usually < intrinsic QRSd |
| Partial correction |
S-HBP LBBB morphology Stim-QRSend < H-QRSend paced QRSd < intrinsic QRSd |
NS-HBP LBBB QRS morphology Stim-QRSend </= H-QRSend paced QRSd >120 ms paced QRSd usually < intrinsic QRSd |
|
| No correction | Stim-QRSend = H-QRSend | ||
|
S-HBP LBBB morphology paced QRSd = intrinsic QRSd |
NS-HBP LBBB morphology paced QRSd > intrinsic QRSd |
||
| Myocardium-only capture | LBBB morphology Stim-QRSend usually > H-QRSend paced QRSd > intrinsic QRSd |
||
| RBBB* | Bundle recruitment |
S-HBP Normal QRS appearance (No BBB morphology) Stim-QRSend < H-QRSend paced QRSd < 120 ms < intrinsic QRSd |
NS-HBP Pre-excited normal QRS appearance (No BBB morphology) Stim-QRSend < H-QRSend paced QRSd </=/> intrinsic QRSd |
| Resynchronisation |
NS-HBP without right bundle recruitment Pre-excited normal QRS appearance (No BBB morphology) Stim-QRSend < H-QRSend paced QRSd < intrinsic QRSd |
||
| No bundle recruitment or resynchronisation |
S-HBP without right bundle recruitment RBBB morphology Stim-QRSend = H-QRSend paced QRSd = intrinsic QRSd |
||
| Myocardium-only capture | LBBB morphology Stim-QRSend > H-QRSend paced QRSd > intrinsic QRSd |
||
| IVCD | Partial correction | Variable response† | |
| No correction |
S-HBP Stim-QRSend = H-QRSend paced QRSd = intrinsic QRSd |
NS-HBP Stim-QRSend < H-QRSend paced QRSd </=/> intrinsic QRSd |
|
| Myocardium-only capture | LBBB morphology Stim-QRSend </=/> H-QRSend paced QRSd </=/> intrinsic QRSd |
Comparison of 12-lead ECG responses to different kinds of conduction system capture in His bundle pacing (HBP) for broad intrinsic QRS complex. *Right bundle branch block (RBBB) can be resynchronised in two ways: bundle recruitment with or without myocardial capture; and non-selective (NS)-HBP without bundle recruitment, which will resynchronise the right ventricle due to the presence of at least two wavefronts in the right ventricle (one from myocardial capture and at least one breakout from the left ventricle). †ECG response of intraventricular conduction delay (IVCD) to conduction system pacing depends on degree of correctable left- or right-sided conduction system delay present. BBB = bundle branch block; H-QRSend = duration from His potential to QRS offset; LBBB = left bundle branch block; QRSd = QRS duration; S-HBP = selective His bundle pacing; Stim-QRSend = duration from pacing stimulus to QRS offset.