title: Comparison of the effects of VVI versus DDD pacing on cardiac baroreflex function.
abstract: BACKGROUND
  Conventional baroreceptor-heart rate (HR) reflex sensitivity cannot be examined in chronotropically incompetent patients or in pacemaker recipients. However, cardiac baroreceptor reflex sensitivity (BRS)-stroke volume (SV), which is closely and linearly correlated with BRS-HR, may be an alternative in that population. The aim of this study was to compare the BRS-SV in pacemaker recipients with a fixed HR paced in VVI versus DDD modes in the supine and upright positions.
  
  
  METHODS
  The pacing mode was set randomly to DDD or VVI with complete atrial and/or ventricular capture, then crossed over to the alternate mode in 9 recipients of dual-chamber pacemakers with atrioventricular (AV) block. Beat-to-beat mean blood pressure and SV were measured in the supine and upright positions, using a tilt table. The BRS-SV, expressed in %/mmHg, was the ratio of low-frequency (LF) power to total power (TP) of SV variability, measured by spectral analysis of spontaneous variations in mean blood pressure and SV.
  
  
  RESULTS
  BRS-SV was significantly lower in the VVI than in the DDD mode in the supine (37.2 +/- 26.7 vs 14.5 +/- 7.7%/mmHg) and upright (22.9 +/- 16.9 vs 10.6 +/- 6.6%/mmHg) positions (P < 0.05 for both comparisons).
  
  
  CONCLUSIONS
  VVI pacing is adverse from the standpoint of cardiac autonomic baroreflex function. A decreased BRS-SV may be one of the factors involved in the hemodynamic intolerance associated with VVI pacing.
authors: Second Department of Internal Medicine, School of Medicine, University of Occupational and Environmental Health, Kitakyushu, Japan.
authors: Yasushi
authors: Y
authors: Oginosawa
authors: Haruhiko
authors: H
authors: Abe
authors: Tomiya
authors: T
authors: Yasumasu
authors: Takuo
authors: T
authors: Tsurugi
authors: Ritsuko
authors: R
authors: Kohno