6.2. “Ablate and pace” strategy
As already mentioned, the first clinical study for HBP was by Deshmukh et al. (2000), an observational, single-center study. In 18 patients scheduled for AV node ablation, with narrow QRS and LVEF <40%, with atrial fibrillation, using stylet-driven leads without a guiding catheter, improvement in LVEF, LV dimensions, and New York Heart Association (NYHA) Functional Classification achieved.8 Afterwards, Occhetta et al. (2006) conducted another small study with 16 patients, trying to achieve HBP again using stylet-driven leads without a guiding catheter, succeeding only in four of them HBP, while in the rest, para-Hisian pacing only recorded. In a follow-up period of 6 months, comparing HBP to RV pacing, the study recorded a better NYHA class, and a 6-min walk test (6MWT), while no difference observed in LVEF and LVESV.37
Because of the difficulty in approaching the His bundle, subsequent studies with improved leads conducted by Huang et al. (2017), Vijayaraman et al. (2017), and Wang et al. (2019) in 42, 40, and 44 patients, respectively.38-40 In all three of these studies, an improvement was noticed in LVEF, left ventricular dimensions, and NYHA class compared with baseline. The authors pointed out that AV node ablation may result in capture thresholds increase or lead dislodgments in a minority of patients and should be taken into account before implantation since patient safety comes first. Similar results were shown in the study by Su et al. (2020), who applied HBP combined with AV node ablation to 81 patients. Additionally, pre-procedure values of high pulmonary artery systolic pressure (PASP) ≥40 mmHg, serum creatinine levels ≥97 μmol/L (≥1.1 mg/dl), or reduced LVEF <40% pointed out as independent predictors of the composite endpoint of all-cause mortality and heart failure hospitalization.41 Finally, Zweerink et al. (2020) compared HBP with AV node ablation in 44 patients, applying either radiofrequency ablation or cryoablation. Although the results regarding the improvement in LVEF were similar to the previous studies regarding the ablation technique, cryoablation appeared as more procedural time-consuming, may require more redo procedures, and does not avoid the risk of compromising His capture thresholds.42 Be that as it may, all studies in the “ablate and pace” indication of HBP until now have been observational, single-center studies with few patients and a short follow-up of a few months. Most authors of all these studies underline the need to conduct large RCTs for this indication, as for the previous one.