179-03: Hisian pacing with apical back-up: preliminary clinical experience

Purpose: Permanent His-bundle pacing entails ventricular activation by the conducting tissue and prevents ventricular desynchronization. However, the pacing threshold can be higher and the R-wave amplitude lower than at conventional pacing sites. The system reliability can be increased by a back-up lead positioned in RV apex, provided that back-up stimulation is inhibited as long as Hisian pacing is effective. We report our preliminary clinical experience on Hisian pacing with apical back-up on demand. Methods: The study includes 14 patients. Ten featured intrinsic or paced atrial rhythm and were implanted with a 3-chamber pacemaker allowing V2 sensing after V1 pacing. Channels V1 and V2 were connected to the Hisian and the apical lead, respectively, so that apical stimulation was only delivered if V2 sensing failed to occur within the VV delay. Four patients with chronic AF were implanted with a dual-chamber pacemaker, connecting the atrial and ventricular channels to the Hisian and apical lead, respectively. After Hisian pacing, apical stimulation was only released in the absence of apical sensing during the AV delay. Ventricular blanking and safety pacing were carefully programmed shorter than the His-apex conduction time (HACT), yet sufficiently long to avoid apical oversensing of the Hisian pulse. This risk was further prevented by haemodynamic surveillance based on transvalvular impedance (TVI) assessment: apical sensing must be followed by systolic TVI increase, indicating ventricular ejection, to inhibit the back-up pulse. Results: Effective Hisian pacing was obtained in all patients. Back-up pulse inhibition was achieved in 11/14 cases (79%), where the HACT averaged 97 ± 14 ms. Reliable apical sensing was not possible in 2 cases, since the minimum effective ventricular blanking exceeded the HACT, and in 1 case where the HACT was longer than the maximum programmable VV delay (120 ms). In patients with enabled apical sensing, the incidence of back-up stimulation never exceeded 1% of the follow-up time. Conclusion: Back-up apical stimulation on demand increases the safety of Hisian pacing with no relevant effect on the stimulator current drain and expected life.