His bundle pacing with no electrophysiological mapping system safe, viable: study

A single centre in Singapore has demonstrated the feasibility and safety of permanent His bundle pacing (HBP) even without the use of an electrophysiology (EP) recording system.

“This was successfully achieved in 75 percent of patients, with no adverse clinical outcomes during the follow-up period,” the researchers said.

Twenty-eight consecutive patients who underwent HBP from August 2018 to February 2019 participated in this study and had their data analysed. The researchers then compared the clinical and technical outcomes of the participants between two time periods of 3 months each. Finally, they followed the patients for 12 months.

Twenty-one (75 percent) patients (mean age 73.3 years, 47.6 percent female) achieved immediate technical success. The mean left ventricular ejection fraction was 53.9 percent. [Singapore Med J 2023;64:373-378]

The indications for HBP were as follows: atrioventricular block in 13 patients (61.9 percent), sinus node dysfunction in seven (33.3 percent), and upgrade from implantable cardioverter-defibrillator to His-cardiac resynchronization therapy in one (4.8 percent).

Baseline characteristics did not significantly differ between time periods 1 and 2, while mean fluoroscopy time improved between the two time frames. Notably, one HBP-related complication of lead displacement occurred during the first time period.

All patients who had successful HBP achieved nonselective His bundle (NSHB) capture, but only eight had selective His bundle capture. At the 12-month follow-up, both NSHB and SHB capture thresholds remained stable.

“The technique can be readily learned with high success rates comparable to those in the existing literature,” the researchers said.

Previous studies had demonstrated the safety and feasibility of permanent HBP, with a 65-percent success rate in the early experiences and 85 percent in the new era in a high-volume centre with experienced electrophyshiologists. [Europace 2010;12:527-533; Pacing Clin Electrophysiol 2010;34:339-347; Pacing Clin Electrophysiol 2010;34:339-347; J Am Coll Cardiol 2018;71:2319-2330]

“Our current study shows that the success rate was comparable to that in the study by Bhatt [and colleagues], in which the acute implant success rate was 75 percent at their experienced electrophysiology centre,” the researchers noted. [JACC Clin Electrophysiol 2018;4:1397-1406]

Barriers

A major obstacle to HBP is difficult lead implantation with acceptable capture threshold because of the much smaller potential target area for lead placement. Thus, higher pacemaker energies are necessary to attain His bundle capture relative to right ventricular (RV) capture. [Europace 2018;20:1819-1826; JACC Clin Electrophysiol 2018;4:1397-1406; J Cardiovasc Electrophysiol 2019;30:1984-1993]

In a prior meta-analysis, the average capture threshold was 1.71 V at the time of implant and 1.79 at >3 months follow-up at varying pulse width. [Europace 2018;20:1819-1826]

“Our study showed that the mean HBP capture threshold was acceptable for both NSHB (1.65 V at 1 ms) and SHB (0.56 V at 1 ms) at the time of implant,” the researchers said.

“We also showed the relative stability of the mean NSHB capture threshold (1.65 V at 1 ms and 1.68 V at 1 ms, respectively; p=0.39) and mean SHBP capture threshold (0.56 at 1 ms and 1.28 V at 1 ms, respectively; p=0.10) on the day of implant and at the 12-month follow-up,” they added.

Such findings support HBP as a feasible alternative to RV pacing even without the use of an EP recording system, according to the researchers.

“An alternative to mitigate this barrier would require further evolution of implantation tools and techniques for HBP, which includes changes in lead design, battery longevity, and capture management algorithms,” they said.