title: Intracardiac atrial signal amplitude in congenital and acquired complete heart block.
abstract: BACKGROUND
  Good and reliable atrial sensing is a fundamental part of atrioventricular (AV) synchrony in dual chamber pacemakers. Due to the floating nature of atrial sensing electrode in single pass dual chamber pacemakers (VDD) compared with two-lead dual chamber pacemakers (DDD), they are more prone to atrial under-sensing and the resulting loss of AV synchrony. We hypothesized that there is a relation between the chronicity of AV block and the amplitude of intracardiac atrial signal amplitudes (IASA).
  
  
  METHODS
  Detailed demographic, electrocardiographic and echocardiographic data were recorded in 34 consecutive patients with congenital and acquired complete heart block (CHB). The intracardiac atrial signal amplitudes (IASA) were recorded at implantation time, 48 hours and 2 months post-implantation and compared between the two groups of patients.
  
  
  RESULTS
  The mean age of the study group was 38.73±12.53 years (congenital: 30.08±11.07, acquired: 47.38±6.5). There were no important differences in left atrial or ventricular sizes and in P-wave amplitude in lead II, but the IASA was significantly higher in the congenital group at implantation time (5.21±1.86 vs. 3.38±0.84 mV, P<0.001) and during the follow-up.
  
  
  CONCLUSIONS
  The intracardiac atrial signal amplitudes were higher in congenital CHB compared with the acquired CHB. Chronicity (and may be the congenital type) of CHB may be an affecting factor in case selection for VDD pacemaker implantation.
authors.affiliation: Department of Electrophysiology, Chamran Heart Hospital, Isfahan University of Medical Science, Isfahan, Iran.
authors.forename: Mohammad Reza Samiei
authors.initials: MR
authors.lastname: Nasab
authors.forename: Mohammad Reza
authors.initials: MR
authors.lastname: Dehghani
authors.forename: Mehrdad
authors.initials: M
authors.lastname: Taherioun
authors.forename: Alireza
authors.initials: A
authors.lastname: Rostamzadeh