title: Effect of left ventricular function on long-term left ventricular pacing and sensing threshold.
abstract: BACKGROUND
  The effect of left ventricular (LV) systolic function on the long-term left ventricular pacing and sensing threshold is unclear.
  
  
  RESULTS
  We studied the effect of LV ejection fraction (LVEF) on the LV pacing and sensing threshold in 56 patients (mean age: 70.2 +/- 10.5 years) underwent permanent LV pacing using a self-retaining coronary sinus lead (Model 1055 K, St Jude Medical, USA). In 49 patients, the LV lead was implanted for conventional pacemaker indication (sick sinus syndrome = 14, heart block = 26 or slow atrial fibrillation = 9). The remaining 7 patients were implanted for congestive heart failure. The LV pacing and sensing threshold, and lead impedance were compared between patients with LVEF <40% (Group 1, n = 28) and LVEF >40% (Group 2, n = 28) during implant and at 3-month follow up. The LV pacing lead was successfully implanted in all patients without any lead dislodgement on follow-up. At implant, Group 1 patients had a significant lower R wave amplitude, but similar LV pacing threshold and lead impedance as compared to Group 2. However, at 3-month follow-up, Group 1 patients had a significantly higher LV pacing threshold compared to Group 2 patients. There were no significant differences in the sensing threshold and lead impedance between the two groups. Furthermore, there was also a significant interval increase in LV pacing threshold in Group 1 patients (0.94 +/- 0.12 V) after 3 months, but not in Group 2 patients (0.16 +/- 0.08 V, p < 0.01).
  
  
  CONCLUSIONS
  The results of this study suggest that the LV systolic function has a significant impact on the long-term LV pacing threshold. The long-term left ventricular pacing threshold in patients with left ventricular systolic dysfunction increased after implant and was higher than patients with normal left ventricular systolic function.
authors.affiliation: Cardiology Division, Department of Medicine, University of Hong Kong, Queen Mary Hospital, Hong Kong, China.
authors.forename: Hung-Fat
authors.initials: HF
authors.lastname: Tse
authors.forename: Cannas
authors.initials: C
authors.lastname: Yu
authors.forename: Vince E
authors.initials: VE
authors.lastname: Paul
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Boriani
authors.forename: Andreas
authors.initials: A
authors.lastname: Schuchert
authors.forename: Juan Leal
authors.initials: JL
authors.lastname: del Ojo
authors.forename: Klaus
authors.initials: K
authors.lastname: Malinowski
authors.forename: Jean-Jacques
authors.initials: JJ
authors.lastname: Blanc
authors.forename: Chu-Pak
authors.initials: CP
authors.lastname: Lau
mesh_terms: D000368:Aged; D002304:Cardiac Pacing, Artificial; D017097:Electric Impedance; D006327:Heart Block / Q000503:physiopathology / Q000628:therapy; D006333:Heart Failure / Q000503:physiopathology / Q000628:therapy; D006801:Humans; D012684:Sensory Thresholds; D012804:Sick Sinus Syndrome / Q000503:physiopathology / Q000628:therapy; D013318:Stroke Volume; D013599:Systole; D018487:Ventricular Dysfunction, Left / Q000503:physiopathology / Q000628:therapy*; D016277:Ventricular Function, Left