Permanent his bundle pacing in suprahisian versus infrahisian atrioventricular block . A single center experience

Abstract

Type of funding sources: None. Permanent His bundle pacing is currently considered the most physiological form of cardiac pacing. The main benefit of the procedure, compared to right ventricular pacing, is encountered in atrioventricular block, where a high burden of ventricular pacing is expected. One of the limits of His bundle pacing is a distal conduction abnormality in the His-Purkinje system. Nevertheless, there is published data that shows the possibility of conduction system capture even in these patients. This retrospective study evaluated the feasibility of permanent His bundle pacing in patients with second or third degree AV block, taking into account the level of block : suprahisian vs. infrahisian. 45 patients with second or third degree AV block with an attempt at permanent His bundle pacing and an available intraprocedural hisian electrogram for review were included. The procedure went as follows: a lead delivery system including a preformed 3D shaped sheath and a lumenless lead with a fixed exposed helix was placed at the septal atrioventricular junction. Careful mapping was performed until a His bundle signal was recorded. At that site, the pacing response was evaluated at variable pacing outputs. The procedural criteria for success was conduction system capture (selective or non-selective) with an amplitude of less than 2,5V/1ms. If the criteria was met, the lead was fixed, an atrial lead was placed and both connected to a dual-chamber pacemaker. The periprocedural characteristics and those at the three-months follow-up were noted. 28 patients (62,2%) were diagnosed with suprahisian block, with a procedural success rate of 89 % and 17 (37,8%) with infrahisian block, with a procedural success rate of 59%. QRS duration was 96,4±21,6 ms in those with suprahisian block vs. 119,4±23,8 ms in those with infrahisian block (p=0,0027). There was no significant statistical difference regarding acute His bundle pacing thresholds (1,13±0,63 V/1ms vs. 1,25±0,76 V/1ms, p= 0,66), ventricular sensing (3,46±1,5 mV vs. 3,21±1,6 mV, p= 0,68) and fluoroscopy time (12,75±8,3 min vs. 10,78±9,5 min, p= 0,57) between suprahisian and infrahisian block. Also, the paced QRS duration was similar between the two groups (86,9±13,4 ms vs. 82±14,7 ms, p= 0,38) and narrower than the baseline complex. The three-months follow-up showed stable pacing and sensing parameters, without other procedural or lead related complications. In atrioventricular block, permanent His bundle pacing achieves atrioventricular resynchronization, while maintaining rapid and synchronous biventricular depolarization. As expected, in suprahisian blocks the success rate is superior to infrahisian blocks. Nevertheless, in a significant proportion of the latter cases, His bundle pacing can recrute the intrinsic conduction system.