title: Functional characteristics of left ventricular synchronization via right ventricular outflow-tract pacing detected by two-dimensional strain echocardiography.
abstract: BACKGROUND
  Recently, due to the detrimental effects on the ventricular function associated with right ventricular apical (RVA) pacing, right ventricular septal (RVS) pacing has become the preferred pacing method. However, the term RVS pacing refers to both right ventricular outflow-tract (RVOT) and mid-septal (RVMS) pacing, leading to a misinterpretation of the results of clinical studies. The purpose of this study, therefore, was to elucidate the functional differences of RVA, RVOT, and RVMS pacing in patients with atrioventricular block.
  
  
  METHODS
  We compared the QRS duration, global longitudinal strain (GLS), and left ventricular (LV) synchronization parameters at the three pacing sites in 47 patients. The peak systolic strain (PSS) time delay between the earliest and latest segments among the 18 LV segments and standard deviation (SD) of the time to the PSS were also calculated for the 18 LV segments at each pacing site using two-dimensional (2D) strain echocardiography.
  
  
  RESULTS
  RVMS pacing was associated with a significantly shorter QRS duration compared with RVA and RVOT pacing (154.4±21.4 vs 186.5±19.9 and 171.1±21.5 ms,P<0.001). In contrast, RVOT pacing revealed a greater GLS (-14.69±4.92 vs -13.12±4.76 and -13.51±4.81%,P<0.001), shorter PSS time delay between the earliest and latest segments (236.0±87.9 vs 271.3±102.9 and 281.9±126.6%,P=0.007), and shorter SD of the time to the PSS (70.8±23.8 vs 82.7±30.8 and 81.5±33.7 ms,P=0.002) compared with RVA and RVMS pacing.
  
  
  CONCLUSIONS
  These results suggest that the functional characteristics of RVOT pacing may be a more optimal pacing site than RVMS, regardless of the pacing QRS duration, in patients with atrioventricular conduction disorders.
authors.affiliation: Division of Cardiology, Hokkaido Cardiovascular Hospital, Sapporo, Japan.
authors.forename: Yasutaka
authors.initials: Y
authors.lastname: Hirayama
authors.affiliation: Department of Cardiology, Asahikawa Medical University, Asahikawa Medical University, Midorigaoka Higashi 2-1-1, Asahikawa, 078-8510, Japan.
authors.forename: Yuichiro
authors.initials: Y
authors.lastname: Kawamura
authors.affiliation: Department of Cardiology, Asahikawa Medical University, Asahikawa Medical University, Midorigaoka Higashi 2-1-1, Asahikawa, 078-8510, Japan.
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Sato
authors.affiliation: Division of Cardiovascular Surgery, Hokkaido Cardiovascular Hospital, Sapporo, Japan.
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Saito
authors.affiliation: Division of Cardiology, Hokkaido Cardiovascular Hospital, Sapporo, Japan.
authors.forename: Hideichi
authors.initials: H
authors.lastname: Tanaka
authors.affiliation: Division of Community Medicine and Epidemiology, Department of Health Science, Asahikawa Medical University, Midorigaoka Higashi 2-1-1, Asahikawa, 078-8510, Japan.
authors.forename: Yasuaki
authors.initials: Y
authors.lastname: Saijo
authors.affiliation: Division of Cardiology, Hokkaido Cardiovascular Hospital, Sapporo, Japan.
authors.forename: Kenjiro
authors.initials: K
authors.lastname: Kikuchi
authors.affiliation: Division of Cardiovascular Surgery, Hokkaido Cardiovascular Hospital, Sapporo, Japan.
authors.forename: Katsumi
authors.initials: K
authors.lastname: Ohori
authors.affiliation: Department of Cardiology, Asahikawa Medical University, Asahikawa Medical University, Midorigaoka Higashi 2-1-1, Asahikawa, 078-8510, Japan.
authors.forename: Naoyuki
authors.initials: N
authors.lastname: Hasebe
keywords: 2D strain echocardiography; Left ventricular synchronization; Right ventricular apical pacing; Right ventricular mid-septal pacing; Right ventricular outflow-tract pacing