An abrupt loss of capture during permanent His-bundle pacing: Assessment of mechanism underlying late capture threshold rise.

A His-bundle (HB) capture threshold rise is still a significant concern in permanent His-bundle pacing (HBP). We present a case where an abrupt increase in HB threshold and loss of capture occurred even after 3.5 years of stable permanent HBP for an atrioventricular block. The development of local fibrosis around the lead helix and the change in an insertion angle of the lead might adversely affect the HB capture threshold in the chronic phase.