title: Four-chamber pacing in patients with poor ejection fraction but normal QRS durations undergoing open heart surgery.
abstract: BACKGROUND
  Poor ejection fraction (EF) comprises a critical risk factor in cardiac bypass surgery (CABG). It has been unclear, whether biventricular or four-chamber pacing confers benefit upon patients with intact atrioventricular and interventricular conduction especially following surgery.
  
  
  METHODS
  Twenty-one consecutive patients with an EF <or= 35% underwent hemodynamic evaluation (continuous pressures and thermodilution) 3, 6, and 18 hours post-CABG and biatrial (AA), biatrial-right ventricular (AAV), and biatrial-biventricular (AAVV) pacing were compared.
  
  
  RESULTS
  Patients (65 +/- 9 years) presented with an average EF of 29.5% (15-35%). 514 measurements of cardiac index (CI) were taken. Nineteen patients (91%) showed highly significant increases in CI with AAVV as compared to AA pacing (P < 0,001) at all times post surgery. The increase in CI with pacing mode varied from 6% to 25% and decreased with time following surgery. No consistent difference in CI was seen between four-chamber (AAVV) and biventricular pacing (AVV). The QRS-widths prior to surgery never exceeded 120 ms; postoperatively QRS-complexes widened in all patients on average by 15.9 ms +/-6 and returned to starting values by 48 hours.
  
  
  CONCLUSIONS
  Biventricular pacing improves CI in patients with poor EF following cardiac surgery in the absence of preoperative atrioventricular- or interventricular conduction block. This benefit decreases with time after surgery as the QRS width returns to preoperative values. Four-chamber pacing did not confer additional benefit as compared to biventricular pacing in this series. Biventricular pacing should be considered as an adjunct in patients with critically low EF undergoing cardiac surgery.
authors.affiliation: Department of Cardiac, Thoracic, Transplantation and Vascular Surgery, Hannover Medical School, Hannover, Germany. pichlmaier.maximilian@mh-hannover.de
authors.forename: Maximilian
authors.initials: M
authors.lastname: Pichlmaier
authors.forename: Eric
authors.initials: E
authors.lastname: Bagaev
authors.forename: Arthur
authors.initials: A
authors.lastname: Lichtenberg
authors.forename: Omke
authors.initials: O
authors.lastname: Teebken
authors.forename: Gunnar
authors.initials: G
authors.lastname: Klein
authors.forename: Michael
authors.initials: M
authors.lastname: Niehaus
authors.forename: Axel
authors.initials: A
authors.lastname: Haverich
mesh_terms: D000368:Aged; D006328:Cardiac Catheterization; D002302:Cardiac Output; D002304:Cardiac Pacing, Artificial / Q000379:methods*; D001026:Coronary Artery Bypass; D004452:Echocardiography; D004562:Electrocardiography; D005260:Female; D006439:Hemodynamics; D006801:Humans; D008297:Male; D011184:Postoperative Period; D011446:Prospective Studies; D012307:Risk Factors; D013318:Stroke Volume / Q000502:physiology*