Conduction system pacing on track to replace CRT? Review of current evidence and prospects of conduction system pacing

Figure 1. Normal cardiac conduction system.

Figure 2. Cardiac conduction system abnormalities.

Figure 3. Illustration of pacing techniques. (1) Atrial pacing. (2) Right ventricular (RV) pacing. (3) His bundle pacing (HBP). (4) Left bundle branch area pacing (LBBAP). (5) Biventricular pacing (BVP) with an epimyocardial left ventricular lead via the coronary sinus (CS).

Figure 4. Number of publications over the last 20 years based on three main pacing techniques of HBP (HIS bundle pacing), LBBAP (left bundle branch area pacing) and CRT (cardiac resynchronization therapy).

Figure 5. His bundle pacing with underlying block at the level of the atrioventricular (AV) node. (A) Non-Selective His bundle pacing with capture of both His bundle and the surrounding septal myocardium, resulting in a paced beat with a fusion pattern. (B) Selective His bundle pacing with capture of His bundle only, with a narrow complex paced beat.

Figure 6. Baseline left bundle branch block (LBBB) and respective QRS morphology and duration with pacing different parts of the conduction system. (A) Pacing above the level of block at the His Bundle with the paced beat resembling LBBB. (B) Non-Selective left bundle branch pacing (LBBP) with capture of both left bundle branch (LBB) and surrounding myocardium resulting in a paced beat with fusion pattern and atypical RBBB pattern with qR in V1. (C) Selective LBBP with capture of LBB only, resulting in a typical wider RBBB pattern with rSR′ in V1. LAF, left anterior fascicle; LPF, left posterior fascicle.