title: Determination of the optimal atrioventricular interval in sick sinus syndrome during DDD pacing.
abstract: BACKGROUND
  Although the AAI pacing mode has been shown to be electromechanically superior to the DDD pacing mode in sick sinus syndrome (SSS), there is evidence suggesting that during AAI pacing the presence of natural ventricular activation pattern is not enough for hemodynamic benefit to occur. Myocardial performance index (MPI) is a simply measurable Doppler-derived index of combined systolic and diastolic myocardial performance. The aim of this study was to investigate whether AAI pacing mode is electromechanically superior to the DDD mode in patients with SSS by using Doppler-derived MPI.
  
  
  METHODS
  Thirty-nine SSS patients with dual-chamber pacing devices were evaluated by using Doppler echocardiography in AAI mode and DDD mode. The optimal atrioventricular (AV) interval in DDD mode was determined and atrial stimulus-R interval was measured in AAI mode. The ratio of the atrial stimulus-R interval to the optimal AV interval was defined as relative AV interval (rAVI) and the ratio of MPI in AAI mode to that in DDD mode was defined as relative MPI (rMPI).
  
  
  RESULTS
  The rMPI was significantly correlated with atrial stimulus-R interval and rAVI (r = 0.57, P = 0.0002, and r = 0.67, P < 0.0001, respectively). A cutoff point of 1.73 for rAVI provided optimum sensitivity and specificity for rMPI >1 based on the receiver operator curves.
  
  
  CONCLUSIONS
  Even though the intrinsic AV conduction is moderately prolonged, some SSS patients with dual-chamber pacing devices benefit from the ventricular pacing with optimal AV interval. MPI is useful to determine the optimal pacing mode in acute experiment.
authors.affiliation: Department of Cardiology, Hiroshima City Asa Hospital, 2-1-1 Kabeminami, Asakita-ku, Hiroshima 731-0293, Japan. ms-katou@asa-hosp.city.hiroshima.jp
authors.forename: Masaya
authors.initials: M
authors.lastname: Kato
authors.forename: Keigo
authors.initials: K
authors.lastname: Dote
authors.forename: Shota
authors.initials: S
authors.lastname: Sasaki
authors.forename: Kenji
authors.initials: K
authors.lastname: Goto
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Takemoto
authors.forename: Seiji
authors.initials: S
authors.lastname: Habara
authors.forename: Daiji
authors.initials: D
authors.lastname: Hasegawa
authors.forename: Osamu
authors.initials: O
authors.lastname: Matsuda
mesh_terms: D000368:Aged; D001283:Atrioventricular Node / Q000503:physiopathology; D002304:Cardiac Pacing, Artificial / Q000379:methods*; D016009:Chi-Square Distribution; D015150:Echocardiography, Doppler; D005260:Female; D006801:Humans; D016014:Linear Models; D008297:Male; D010138:Pacemaker, Artificial; D012372:ROC Curve; D012804:Sick Sinus Syndrome / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000628:therapy*