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Compared with RV pacing, HBP capture thresholds are on average higher and sensing amplitudes lower. A recent observational study raised concern with regard to increasing HBP pacing thresholds with intermediate follow-up.426 The higher capture thresholds lead to shorter battery longevity (at 5 years there were 9% generator changes with HBP compared with 1% with RVP).427 Capture thresholds of HBP at implantation should aim to be <2.0 V/1 ms (or <2.5 V/ 0.4 ms) and bipolar R-wave sensing amplitude >2.0 mV. With experience, thresholds decrease as implanters gain confidence to reposition leads. Sensing issues include not only ventricular undersensing, but also oversensing of atrial or His potentials (which may be potentially lethal in a pacemaker-dependent patient). An RV backup lead should be considered if the implanter is inexperienced, or if there are high capture thresholds or sensing issues in pacemaker-dependent patients, in those scheduled for AVN ablation (where there is a risk of compromising HBP), or in patients with highdegree or infranodal block. Pros and cons are listed in Table 9. Several series have shown that the rate of mid-term lead revision is relatively high at 7%,318,423,427,428 (and reported to be as high as 11%426), and is higher than RV pacing, which is 23%.427,429 Therefore, it is advisable to follow-up these patients at least once every 6 months or place them on remote monitoring (ensuring that automatic threshold measurements correspond to those measured manually, as this may not be the case and depends on device configuration).430 Device programming should take into account specific requirements for HBP, which are covered in detail elsewhere.431,432

7.2.2 Indications 7.2.2.1 Pacing for bradycardia One study reported that in patients with AVB and normal baseline LVEF, the incidence of RV pacing-induced cardiomyopathy was 12.3% and the risk was increased if the percentage of ventricular pacing was >_20% (HR 6.76; P = 0.002).188 However, there are no data to support that any percentage of RV pacing can be considered as defining a true limit below which RV pacing is safe and beyond which RV pacing is harmful. Observational data indicate that patients with HBP fare better in terms of HF hospitalizations than patients with RV pacing if the percentage of ventricular pacing is >20% (HR 0.54; P = 0.01).42 Of note, the average baseline LVEF in patients with HBP in that study was 55% and the average QRS duration was 105 ms. HBP may therefore avoid clinical deterioration in these patients, particularly if the intrinsic QRS is narrow or if BBB is corrected by HBP.

In a series of 100 patients with AVB undergoing HBP by experienced operators, implantation was successful in 41/54 (76%) patients with infranodal AVB and higher in the case of nodal block (93%; P < 0.05).433 Over a mean follow-up of 19 ± 12 months, lead revision was necessary in 2/41 (5%) patients with infranodal block and in 3/43 (7%) with nodal block. Notably, the average LVEF in this series was 54%, and there are no data reported specifically on HBP in patients with AVB and reduced LVEF. HBP is an option in patients with a narrow QRS or if HBP corrects BBB, but otherwise biventricular pacing is indicated. There is a need for RCTs to compare the safety and efficacy of HBP with RV pacing. It is important to balance the potential benefits of HBP with the aforementioned issues of higher capture thresholds and shorter battery longevity, a higher rate of lead revision, and more frequent sensing issues, compared with RV pacing. It is also important to consider the operator’s experience and expertise with HBP, and whether a backup ventricular pacing lead is indicated. The patient’s safety should be first and foremost in decision-making.

7.2.2.2 Pace and ablate Seven observational series, totalling >240 patients treated with a ‘pace-and-ablate’ strategy for rapidly conducted AF, found an improvement in LVEF and NYHA class compared with baseline with HBP.197199,434 Long-term results with a median of 3 years of followup have been reported, with favourable outcomes.434 A singleblinded, randomized, crossover study in 16 patients compared HBP with RVA pacing over 6 months and found better NYHA and 6-min walk distance with HBP, without differences in echocardiographic parameters.200 However, only four patients in this study had confirmed HBP (with para-Hisian pacing in the remaining patients). These studies included patients with reduced as well as preserved LVEF,197,198 and QRS width was on average <120 ms. HBP is of particular interest in patients with a normal baseline QRS morphology as it preserves intrinsic ventricular synchrony, However, a caveat is that AVJ ablation may result in an increase in HBP capture thresholds or in lead dislodgments in a minority of patients.197,199,318,426 Owing to these issues and risk of HBP lead failure, a backup RV lead should be considered.

7.2.2.3 Role in cardiac resynchronization therapy In 1977, Narula showed that pacing of the His bundle can correct LBBB in a subset of patients, implying a proximal site of conduction disturbance with longitudinal dissociation within the His bundle.435 A recent mapping study reported intra-Hisian block in 46% of patients with LBBB, in whom 94% were corrected by temporary HBP.436 HBP may therefore be used in lieu of biventricular pacing for HBP-based CRT, as some data have shown that results are comparable (see Supplementary Table 10).437439 Nevertheless, especially in CRT candidates with LBBB, biventricular pacing has more solid evidence of efficacy and safety, and therefore remains first-line therapy. However, HBP should be considered as a bailout solution in the case of failed

Table 9 Advantages and disadvantages of a ‘backup’ ventricular lead with His bundle pacing

Advantages • Increased safety (in case of loss of capture of the HBP lead) • Can be used for sensing (lower risk of ventricular undersensing, no risk of His or atrial oversensing) • Programming of pacing output with lower safety margins • May serve to narrow the QRS with fusion pacing in the case of selective-HBP with uncorrected RBBB Disadvantages • Higher cost • More transvenous hardware • Risk associated with the additional lead (e.g. ventricular perforation) • More complex programming • “Off-label” use (current regulatory approval and MRI-conditionality for HBP is only granted for His leads connected to the RV port)

HBP = His bundle pacing; MRI = magnetic resonance imaging; RBBB = right bundle branch block. ESC 2021 Downloaded from academic.oup.com/eurheartj/article/42/35/3427/6358547 by guest on 07 October 2026