title: Acute His-Bundle Injury Current during Permanent His-Bundle Pacing Predicts Excellent Pacing Outcomes.
abstract: BACKGROUND
  His-bundle (HB) pacing (P) is a physiological alternative to right ventricular pacing (RVP), but is technically challenging and limited by higher pacing thresholds. Myocardial injury current (IC) recorded during right ventricular lead placement implies good tissue contact and is associated with low-pacing thresholds. IC at the HB has not been previously described. We hypothesized that HBIC during permanent HBP may be associated with lower pacing thresholds.
  
  
  METHODS
  Permanent HBP was performed using Medtronic Select Secure(tm) (Medtronic Inc., Minneapolis, MN, USA) delivered via a fixed-curve (C315 His) sheath. HB electrogram (EGM) was recorded in a unipolar fashion from the lead tip. Presence or absence of HBIC was documented. HBP threshold, sensing, and impedances were recorded at implant, 2 weeks, 2 months, and 1 year.
  
  
  RESULTS
  Sixty patients (age 72 ± 15 years; male 55%, sick sinus syndrome 40%, atrioventricular block 60%, fluoroscopy duration 9.2 ± 3.7 minutes) underwent successful permanent HBP. HBIC was recorded in 22 (37%) patients (group I). HBEGM without IC was recorded in the remaining 38 (63%) patients (group II). Pacing threshold at implant, 2 weeks, 2 months, and 1 year were significantly lower in group I (1.16 ± 0.4 V; 1.18 ± 0.5 V; 1.23 ± 0.6 V; 1.3 ± 0.6 V @ 0.5 ms) compared to group II (1.75 ± 0.7 V; 1.82 ± 0.8 V; 1.93 ± 0.8 V; 1.98 ± 0.9 V @ 0.5 ms, P < 0.05), respectively.
  
  
  CONCLUSIONS
  IC can be recorded at the HB during permanent HBP in 37% of patients. HBIC is associated with significantly lower pacing thresholds compared to patients in whom HBIC was not recorded. HBIC may be a marker for superior short-term HBP thresholds.
authors.affiliation: Department of Cardiac Electrophysiology, Geisinger Heart and Vascular Institute, Wilkes-Barre, Pennsylvania.
authors.forename: Pugazhendhi
authors.initials: P
authors.lastname: Vijayaraman
authors.forename: Gopi
authors.initials: G
authors.lastname: Dandamudi
authors.forename: Sarah
authors.initials: S
authors.lastname: Worsnick
authors.forename: Kenneth A
authors.initials: KA
authors.lastname: Ellenbogen
mesh_terms: D000368:Aged; D054537:Atrioventricular Block / Q000503:physiopathology* / Q000628:therapy*; D002036:Bundle of His / Q000503:physiopathology*; D002304:Cardiac Pacing, Artificial / Q000379:methods*; D022062:Electrophysiologic Techniques, Cardiac; D005260:Female; D006801:Humans; D008297:Male; D012804:Sick Sinus Syndrome / Q000503:physiopathology* / Q000628:therapy*; D016896:Treatment Outcome
keywords: His-bundle pacing; heart failure; pacing