title: Biventricular pacing: impact on exercise-induced increases in mitral insufficiency in patients with chronic heart failure.
abstract: BACKGROUND
  Mitral regurgitation (MR) in chronic heart failure (CHF) patients frequently worsens with exercise. Cardiac resynchronization therapy (CRT) reduces MR at rest, but its effects on exercise-induced worsening of MR are incompletely explored. The present study examined the influence of CRT on MR during submaximal exercise in CHF patients.
  
  
  METHODS
  Eleven patients with CHF who were treated with CRT underwent echocardiography while performing steady-state exercise during four conduction modes (intrinsic rhythm, right ventricular [RV], biventricular [BiV] and left ventricular [LV] pacing). Measurements of MR were jet area planimetry, effective regurgitant orifice area, peak MR flow rate and regurgitant volume.
  
  
  RESULTS
  At rest and during exercise, there were no differences in dyssynchrony between intrinsic rhythm and RV pacing. BiV and LV pacing reduced dyssynchrony at rest and during exercise compared with intrinsic conduction and RV pacing, and there were no differences in the magnitude of these effects between these two pacing modes. At rest, RV pacing increased MR compared with intrinsic conduction (MR regurgitant volume; P<0.05), whereas BiV and LV pacing reduced MR (reductions in effective regurgitant orifice area and jet area; P<0.02, and MR flow rate; P<0.05 with BiV pacing from intrinsic conduction). MR significantly increased on exercise with intrinsic rhythm and RV pacing, whereas with LV and BiV pacing, there were no significant exercise-induced increases in any MR variable. There were relationships between changes in measures of dyssynchrony and reductions in MR at rest and during exercise.
  
  
  CONCLUSIONS
  CRT reduces MR at rest and during exercise, and prevents exercise-induced MR. Reductions in MR during exercise correlate with improvements in dyssynchrony.
authors.affiliation: Department of Medicine, Mount Sinai and University Health Network Hospitals, University of Toronto, Toronto, Ontario.
authors.forename: Klaus K
authors.initials: KK
authors.lastname: Witte
authors.forename: Zion
authors.initials: Z
authors.lastname: Sasson
authors.forename: Joan A
authors.initials: JA
authors.lastname: Persaud
authors.forename: Robynn
authors.initials: R
authors.lastname: Jolliffe
authors.forename: Robert W
authors.initials: RW
authors.lastname: Wald
authors.forename: John D
authors.initials: JD
authors.lastname: Parker
mesh_terms: D002304:Cardiac Pacing, Artificial; D015444:Exercise; D005260:Female; D006333:Heart Failure / Q000503:physiopathology* / Q000628:therapy*; D006801:Humans; D008297:Male; D008875:Middle Aged; D008944:Mitral Valve Insufficiency / Q000503:physiopathology*; D010138:Pacemaker, Artificial