Programmed His bundle pacing - a novel maneuver for the diagnosis of His bundle capture

BackgroundDuring permanent non-selective (ns) His bundle (HB) pacing, it is crucial to confirm HB capture / exclude that only right ventricle (RV)-myocardial septal pacing is present. Because the effective refractory period (ERP) of the working myocardium is different than the ERP of the HB, we hypothesized that it should be possible to differentiate ns-HB capture from RV-myocardial capture using programmed extra-stimulus technique.MethodsIn consecutive patients during HB pacemaker implantation, programmed HB pacing was delivered from the screwed-in HB pacing lead. Premature beats were introduced at 10 ms steps during intrinsic rhythm and also after a drive train of 600 ms. The longest coupling interval that resulted in an abrupt change of QRS morphology was considered equal to ERP of HB or RV-myocardium.ResultsProgrammed HB pacing was performed from 50 different sites in 32 patients. In 34/36 cases of ns-HB pacing, the RV-myocardial ERP was shorter than HB ERP (271.8±38 ms vs 353.0±30 ms, p < 0.0001). Programmed HB pacing using a drive train resulted in a typical abrupt change of paced QRS morphology: from ns-HB to RV-myocardial QRS (34/36 cases) or to selective HB QRS (2/36 cases). Programmed HB pacing delivered during supraventricular rhythm resulted in obtaining selective HB QRS in 20/34 and RV-myocardial QRS in 14/34 of the ns-HB cases. In RV-myocardial only pacing cases (“false ns-HB pacing”, n=14), such responses were not observed – the QRS morphology remained stable. Therefore, the PHB pacing correctly diagnosed all ns-HB cases and all RV-myocardial pacing cases.ConclusionsA novel maneuver for the diagnosis of HB capture, based on the differences in ERP between HB and myocardium was formulated, assessed and found as diagnostically valuable. This method is unique in enabling to visualize selective HB QRS in patients with otherwise obligatory ns-HB pacing (RV-myocardial capture threshold < HB capture threshold).What this study addsProgrammed His bundle pacing – a novel and straightforward method for unquestionable diagnosis of His bundle capture during non-selective pacing was developed and assessed.A method for visualization of selective HB capture QRS in patients with obligatory non-selective pacing (myocardial capture threshold < His bundle capture threshold) was discovered and physiology behind it explained.