title: Effects of pacing rates on global and regional myocardial blood flow.
abstract: BACKGROUND
  Information is scarce on the effects of right ventricular apical (RVA) pacing on regional and global myocardial blood flow (MBF). The purpose of this study was to assess the relationship between pacing rate and both regional and global MBF.
  
  
  METHODS
  Four patients with exclusive atrial pacing and six patients with exclusive RVA pacing underwent three consecutive H(2) (15)O positron emission tomography scans at 60, 90, and 130 pulses per minute (ppm). For each pacing rate, regional and global MBF was determined. In all patients, the left ventricular (LV) function was normal.
  
  
  RESULTS
  By varying the atrial pacing rate from 60 to 130 ppm, the mean global MBF increased from 0.94 to 1.40 mL/g/min, whereas the mean septal to lateral MBF ratio decreased from 1.09 to 0.83. In ventricular-paced patients at corresponding rates, the mean global MBF also increased from 1.07 to 1.52 mL/g/min but here the mean septal to lateral MBF ratio increased from 0.83 to 1.0.
  
  
  CONCLUSIONS
  During both acute atrial and RVA pacing, regional and global MBF increases with higher pacing rates. However, the septal to lateral MBF ratio decreases with atrial pacing and increases with RVA pacing in patients with normal LV function. In RVA pacing, these different rate-dependent effects on regional MBF can be considered as a favorable factor that helps to understand why in some long-term paced patients, LV function is preserved.
authors: Department of Cardiology, St. Antonius Hospital, Nieuwegein, The Netherlands. timtencate@yahoo.com
authors: Tim J F
authors: TJ
authors: Ten Cate
authors: Paul
authors: P
authors: Knaapen
authors: Adriaan A
authors: AA
authors: Lammertsma
authors: Carel C
authors: CC
authors: De Cock
authors: Norbert M
authors: NM
authors: Van Hemel
authors: J Fred
authors: JF
authors: Verzijlbergen