Conduction system pacing: overview, definitions, and nomenclature

Figures

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  Figure 1. Dissection of the conduction system visualized from the right-sided chambers. The triangle of Koch is depicted by the red dotted triangle. Reproduced, with permission, from Cabrera et al.48 AV, atrioventricular; CSO, coronary sinus ostium; OF, fossa ovalis; RVA, right ventricular apex; RVOT, right ventricular outflow tract; STV, septal leaflet of the tricuspid valve.

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  Figure 2. Illustration of His, ventricular, and atrial tissue capture by the His bundle lead. Intrinsic rhythm: sinus rhythm with preserved atrioventricular conduction and left bundle branch block. During the threshold test with decrementing pacing output (V), various transitions were noted. NSHBP, non-selective His bundle pacing with capture of the His bundle + local myocardium; SHBP, selective His bundle pacing with correction of left bundle branch block and QRS displaying a right bundle branch block pattern (due to selective capture of conduction fibres destined for the left ventricle. Atrial: lowering of pacing output resulted in capture of the right atrium only, with 1:1 atrioventricular conduction.

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  Figure 3. Outline of capture types obtainable at various levels of the conduction system. HBP, His bundle pacing; LBBAP, left bundle branch area pacing; LBPP, left bundle branch pacing; LFP, left fascicular pacing; LVSP, left ventricular septal pacing; RBBP, right bundle branch pacing; LAFP, left anterior fascicle pacing; LPFP, left posterior fascicle pacing; LSFP, left septal fascicle pacing. Modified with permission from Burri et al.46

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  Figure 4. V6 R-wave peak time reflects activation time of the lateral wall of the left ventricle. It remains constant during native conduction and both selective and non-selective His bundle pacing. Loss of His bundle capture, that is right ventricular septal-only capture, results in prolongation of paced V6 R-wave peak time by 38 ms (from 90 to 128 ms). Reproduced with permission from Jastrzebski et al.64

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  Figure 5. QRS and V6 R-wave peak time difference between different His bundle area capture types. Patient with right bundle branch pacing, right bundle branch to ventricle interval of 30 ms, and potential to V6 R-wave peak time of 82 ms. Two QRS transitions with small (<20 ms) increments of V6 R-wave peak time were present. At high output, His bundle pacing was obtained with paced V6 R-wave peak time of 90 ms, similar to native potential to V6 R-wave peak time of 82 ms (±10 ms). At working output, right bundle branch pacing was observed, resulting in V6 R-wave peak time increase by 10 ms. At low output, loss of right bundle branch capture was observed resulting in right ventricular septal pacing and further increase of V6 R-wave peak time by 16 ms. Reproduced with permission from Jastrzebski et al.61

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  Figure 6. Examples of paced electrocardiogram patterns and endocardial electrograms during left bundle branch area pacing. Left bundle branch pacing characterized by left bundle branch potential to QRS interval of 34–25 ms and lead tip position ∼1.5 cm from the His bundle. Left fascicular pacing—characterized by potential to QRS of 0–24 ms and lead tip position ∼1.5–4.5 cm from His bundle. Left bundle fascicular pacing includes: left posterior fascicle pacing, left anterior fascicle pacing, left septal fascicle pacing. Left ventricular septal pacing: diagnosed when left bundle branch capture criteria are not met, any distance from His bundle. Heart drawing based on work by Patrick J. Lynch and C. Carl Jaffe, MD/CC-BY 2.5, https://commons.m.wikimedia.org/wiki/File:Heart_anterior_view_coronal_section.jpg, reproduced with permission from Jastrzebski et al.26