title: Modulation of the sinus rate during ventricular fibrillation.
abstract: BACKGROUND
  During supraventricular and ventricular tachycardia, the arterial baroreflex predominates with minimal contribution from the cardiopulmonary reflex. To our knowledge, the role of the arterial baroreflex gain (BRG) during and immediately following termination of ventricular fibrillation (VF) has not been characterized.
  
  
  OBJECTIVE
  We hypothesized that (1) arterial BRG correlated with sinus node cycle length (SNCL) changes during VF, and that (2) the greater the arterial BRG, the greater the blood pressure (BP) recovery following successful defibrillation.
  
  
  METHODS
  Arterial BRG was assessed in 18 patients referred for the implantation of a defibrillator incorporating an atrial lead. The average SNCL was measured during the 5 seconds prior to VF induction and the last 5 seconds during VF before defibrillation. Percent SNCL change (%DeltaSNCL) was determined. Arterial BP recovery was calculated as the difference in mean BP following defibrillation compared to during VF.
  
  
  RESULTS
  Arterial BRG ranged between -3 and 18 ms/mmHg. During VF, SNCL shortened in 11 patients (group A, mean %DeltaSNCL =-15%), and surprisingly lengthened in seven patients (group B, mean %DeltaSNCL = 5%). There was no correlation between %DeltaSNCL and arterial BRG. In fact, arterial BRG in group A was lower when compared with group B (P = 0.075). Similarly, there was no correlation between arterial BRG and BP recovery.
  
  
  CONCLUSIONS
  We found no correlation between arterial BRG and %DeltaSNCL during VF, or BP recovery following defibrillation. Our findings of SNCL lengthening in 7 of 18 patients suggest that in some patients, arterial BRG plays a minor role during VF with a greater contribution from the cardiopulmonary BRG.
authors.affiliation: Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, Utah 84112-5000, USA. wasmund@cvrti.utah.edu
authors.forename: Stephen L
authors.initials: SL
authors.lastname: Wasmund
authors.forename: Rakesh K
authors.initials: RK
authors.lastname: Pai
authors.forename: Roger A
authors.initials: RA
authors.lastname: Freedman
authors.forename: Moeen
authors.initials: M
authors.lastname: Abedin
authors.forename: Marcos
authors.initials: M
authors.lastname: Daccarett
authors.forename: Nathan M
authors.initials: NM
authors.lastname: Segerson
authors.forename: Alexey V
authors.initials: AV
authors.lastname: Zaitsev
authors.forename: Mohamed H
authors.initials: MH
authors.lastname: Hamdan
mesh_terms: D000368:Aged; D017704:Baroreflex / Q000502:physiology; D001794:Blood Pressure / Q000502:physiology; D004554:Electric Countershock; D004562:Electrocardiography; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D012849:Sinoatrial Node / Q000503:physiopathology*; D014693:Ventricular Fibrillation / Q000503:physiopathology*