title: Hemodynamic benefit of maintaining atrioventricular synchrony during cardiac pacing in critically ill patients.
abstract: OBJECTIVE
  To determine the hemodynamic effects of maintaining atrioventricular synchrony during emergency cardiac pacing in critically ill patients.
  
  
  METHODS
  Prospective, within patient double-blind study.
  
  
  METHODS
  ICU or coronary care unit patients in a university hospital.
  
  
  METHODS
  Forty (23 cardiac surgery, ten acute myocardial infarction, and seven general intensive care) seriously ill patients with severe symptomatic bradycardia.
  
  
  METHODS
  Initial randomization of patients to receive either a pacing mode where atrioventricular synchronization was maintained (atrioventricular pacing: atrial demand, atrioventricular sequential, atrioventricular universal) or a mode of pacing where atrioventricular synchrony was not preserved (ventricular demand pacing).
  
  
  RESULTS
  The cardiac output increased from a mean of 4.5 +/- 1.7 L/min (95% confidence intervals: 4.0 to 5.0 L/min) during ventricular demand pacing to 5.3 +/- 1.7 L/min (95% confidence intervals: 4.9 to 5.9 L/min) during atrioventricular pacing (p less than .0001) despite trivial decreases in CVP from 14 +/- 4 mm Hg (95% confidence intervals: 13 to 15 mm Hg) to 13 +/- 5 mm Hg (95% confidence intervals: 12 to 15 mm Hg) and pulmonary artery occlusion pressure from 18 +/- 5 mm Hg (95% confidence intervals: 16 to 20 mm Hg) to 17 +/- 5 mm Hg (95% confidence intervals: 15 to 18 mm Hg). At the same time, mean arterial pressure (MAP) increased from 74 +/- 15 mm Hg (95% confidence intervals: 64 to 79 mm Hg) to 83 +/- 15 mm Hg (95% confidence intervals: 80 to 88 mm Hg) and left ventricular stroke work index from 22 +/- 10 g.m/m2 (95% confidence intervals: 19 to 25 g.m/m2) to 30 +/- 11 g.m/m2 (95% confidence intervals: 26 to 33 g.m/m2). There was no significant change in mean pulmonary artery pressure, pulmonary vascular resistance index, or systemic vascular resistance index.
  
  
  CONCLUSIONS
  When cardiac pacing is required in critically ill patients, maintaining atrioventricular synchrony increases stroke volume, cardiac output, and MAP apparently with minimal effects on preload and afterload.
authors.affiliation: Intensive Care Unit, Royal Perth Hospital, Western Australia.
authors.forename: K D
authors.initials: KD
authors.lastname: Donovan
authors.forename: G J
authors.initials: GJ
authors.lastname: Dobb
authors.forename: K Y
authors.initials: KY
authors.lastname: Lee
mesh_terms: D000328:Adult; D000368:Aged; D001919:Bradycardia / Q000628:therapy*; D002304:Cardiac Pacing, Artificial; D003325:Coronary Care Units; D003422:Critical Care / Q000379:methods*; D004311:Double-Blind Method; D004630:Emergencies; D005260:Female; D006439:Hemodynamics; D006801:Humans; D007362:Intensive Care Units; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies