Current knowledge of upgrade procedure
HBP has been thought to be associated with several limitations, such as higher capture thresholds, especially in the setting of BBB or infranodal block; lower R-wave amplitudes; and increased risk for lead revisions from late threshold increase. Indeed, as abovementioned, survival prognosis of HBP application was still unclear due to lacking randomized evidence. Thus, HBP has not been widely generalized in clinical practice and is a class IIa indication in the latest guidelines for the management of bradyarrhythmia [15]. In our study, we found that the distal HBP and LBBP were helpful for the better capture thresholds and R-wave. The distal HBP and LBBP pacing, fixed in the septal myocardium, could provide ideal capture thresholds, high R-wave amplitudes. The key point for successful pacing is bypass conduction blocks area of distal his bundle or proximal left bundle. We were able to achieve distal HBP /LBBP in 34 of 36 patients with infranodal AV block in this study, which proved the possibility to achieve high success rates of physiologic pacing in patients dependent to ventricular pacing. The long-term effects of his-purkinje pacing on the septal contractile stress need to be further evaluated.