title: Avoidance of right ventricular pacing in cardiac resynchronization therapy improves right ventricular hemodynamics in heart failure patients.
abstract: BACKGROUND
  Cardiac resynchronization therapy (CRT) applied by pacing the left and right ventricles (BiV) has been shown to provide synchronous left ventricular (LV) contraction in heart failure patients. CRT may also be accomplished through synchronization of a properly timed LV pacing impulse with intrinsically conducted activation wave fronts. Elimination of right ventricular (RV) pacing may provide a more physiological RV contraction pattern and reduce device current drain. We evaluated the effects of LV and BiV pacing over a range of atrioventricular intervals on the performance of both ventricles.
  
  
  METHODS
  Acute LV and RV hemodynamic data from 17 patients with heart failure (EF = 30 +/- 1%) and a wide QRS (138 +/- 25 msec) or mechanical dyssynchrony were acquired during intrinsic rhythm, BiV, and LV pacing.
  
  
  RESULTS
  The highest LV dP/dt(max) was achieved during LV pre- (LV paced prior to an RV sense) and BiV pacing, followed by that obtained during LV post-pacing (LV paced after an RV sense) and the lowest LV dP/dt(max) was recorded during intrinsic rhythm. Compared with BiV pacing, LV pre-pacing significantly improved RV dP/dt(max) (378 +/- 136 mmHg/second vs 397 +/- 136 mmHg/second, P < 0.05) and preserved RV cycle efficiency (61.6 +/- 14.6% vs 68.6 +/- 11.4%, P < 0.05) and stroke volume (6.6 +/- 4.4 mL vs 9.0 +/- 6.3 mL, P < 0.05). Based on LV dP/dt(max), the optimal atrioventricular interval could be estimated by subtracting 30 msec from the intrinsic atrial to sensed RV interval.
  
  
  CONCLUSIONS
  Synchronized LV pacing produces acute LV and systemic hemodynamic benefits similar to BiV pacing. LV pacing at an appropriate atrioventricular interval prior to the RV sensed impulse provides superior RV hemodynamics compared with BiV pacing.
authors.affiliation: Division of Cardiology, Department of Medicine, Queen Mary Hospital, Hong Kong, China. klflee@hku.hk
authors.forename: Kathy L
authors.initials: KL
authors.lastname: Lee
authors.forename: John E
authors.initials: JE
authors.lastname: Burnes
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Mullen
authors.forename: Douglas A
authors.initials: DA
authors.lastname: Hettrick
authors.forename: Hung-Fat
authors.initials: HF
authors.lastname: Tse
authors.forename: Chu-Pak
authors.initials: CP
authors.lastname: Lau
mesh_terms: D002304:Cardiac Pacing, Artificial / Q000379:methods*; D005260:Female; D006333:Heart Failure / Q000150:complications / Q000517:prevention & control*; D006801:Humans; D008297:Male; D008875:Middle Aged; D016896:Treatment Outcome; D018487:Ventricular Dysfunction, Left / Q000209:etiology / Q000517:prevention & control*; D018497:Ventricular Dysfunction, Right / Q000209:etiology / Q000517:prevention & control*