title: Cardiac output response to changes of the atrioventricular delay in different body positions and during exercise in patients receiving cardiac resynchronization therapy.
abstract: OBJECTIVE
  The aim of this study was to study the haemodynamic effect of atrioventricular delay (AVD) modifications within a narrow range in different body positions and during exercise in patients receiving cardiac resynchronization therapy (CRT).
  
  
  METHODS
  The previously optimized AVD was shortened and prolonged by 40 ms in 27 CRT patients and 9 controls without heart failure. Cardiac output (CO) was measured by inert gas rebreathing (Innocor) as the average over different body positions (left-lateral, supine, sitting, standing, and exercise). In eight CRT patients with an implantable haemodynamic monitor, the estimated pulmonary artery diastolic pressure (ePAD) was analysed.
  
  
  RESULTS
  The magnitude of CO response to AVD changes was greater in CRT patients than in controls (0.25 vs. 0.20 L/min, P<0.05), varied substantially between individuals (range: 0.12-0.56 L/min), and correlated with left atrial size (r=0.61, P<0.001). On average, AVD shortening decreased CO slightly (0.07+/-0.17 L/min) and increased ePAD (1.1+/-0.8 mmHg, both P<0.05), whereas prolongation had no significant effect.
  
  
  CONCLUSIONS
  The haemodynamic response to AVD modifications within a narrow range is larger in CRT patients than in normal controls and varies substantially between individuals. These findings suggest that optimal AVD tuning is clinically important in selected patients.
authors: Department of Cardiology, Karolinska Institutet, Karolinska University Hospital, S-17176 Stockholm, Sweden. marcus.stahlberg@ki.se
authors: Marcus
authors: M
authors: Ståhlberg
authors: Morten
authors: M
authors: Damgaard
authors: Peter
authors: P
authors: Norsk
authors: Anders
authors: A
authors: Gabrielsen
authors: Anders
authors: A
authors: Sahlén
authors: Cecilia
authors: C
authors: Linde
authors: Frieder
authors: F
authors: Braunschweig
mesh_terms: D000368:Aged; D001283:Atrioventricular Node / Q000503:physiopathology*; D002302:Cardiac Output; D002304:Cardiac Pacing, Artificial; D005260:Female; D006333:Heart Failure / Q000503:physiopathology* / Q000517:prevention & control*; D006339:Heart Rate; D006801:Humans; D008297:Male; D005082:Physical Exertion; D011187:Posture