5. HBP: Implantation and follow-up
Despite the described difficulties of HBP, there are data from a small number of centers indeed that show encouraging results for this implantation technique, as well as for the follow-up of these patients regarding the variation of the pacing parameters within the time. In a recently published study including a total of 529 patients, in five years, with a mean 7-month follow-up, a relatively short learning curve was recorded, with an overall implant success rate of 81%, which improved to 87 % after completion of 40 cases.24 The mean fluoroscopy time was 11.7 ± 12.0 min, and His capture threshold decreased. HBP lead re-implantation occurred in 7.5% of successful procedures mainly due to threshold rise. It is worth noting that the QRS duration decreased by 26 msec in patients with an intrinsic QRS > 120 msec, while on the contrary, an insignificant increase in the QRS width by 12 msec observed in the patients with a narrow QRS.
Regarding the efficacy of HBP, in QRS duration change with non-selective or selective pacing, in the absence of BBB, selective and non-selective pacing minimally affected QRS duration, whereas, in the presence of BBB, QRS duration markedly decreased with both patterns of HBP.18 AV block morphology seems to affect the procedural success and needs to be considered before applying this type of pacing. In a recently published meta-analysis of 1438 patients, the implant success rate of the lead in the bundle of His averaged 84.8%, considerably higher than that with older stylet-driven leads with which the success rate reached up to just 70%. LVEF improved by an average of 5.9% during follow-up and even more in ventricles with impaired systolic performance <50%, while in preserved LVEFs, no statistically significant change recorded. Average pacing thresholds were 1.71 V at implant and 1.79 V at >3 months follow-up, with various pulse widths.25
Also, according to recently published data, both the intermediate-term and the long-term performance of HBP leads seem to be quite encouraging for the implantation success rate and the threshold maintenance. Nevertheless, threshold increase and the loss of selective pacing have not been overcome in this study, too, during a follow-up period of 1.5 years, and that may cause a lead revision in rates up to 10%.26 Additionally, in patients’ follow-up data for five years, HBP proved superior to RV pacing in paced QRS duration and LVEF improvement with significantly lower rates of occurrence of Pacing-Induced Cardiomyopathy, findings affecting clinical endpoints, such as death and heart failure hospitalizations, especially in patients with >40% ventricular pacing.27 A summary of published trials conducted in the last 15 years on HBP with clinical and/or echocardiographic follow-up is included in the 2021 ESC Guidelines’ supplementary data on cardiac pacing and cardiac resynchronization therapy.1 Therefore, according to all mentioned, the question of “when and in which patients” it is worth applying the HBP could be answered based on the following four axes, as shown in summary in Figure 4 .