title: Cardiac resynchronization in chronic heart failure.
abstract: BACKGROUND
  Previous studies have suggested that cardiac resynchronization achieved through atrial-synchronized biventricular pacing produces clinical benefits in patients with heart failure who have an intraventricular conduction delay. We conducted a double-blind trial to evaluate this therapeutic approach.
  
  
  METHODS
  Four hundred fifty-three patients with moderate-to-severe symptoms of heart failure associated with an ejection fraction of 35 percent or less and a QRS interval of 130 msec or more were randomly assigned to a cardiac-resynchronization group (228 patients) or to a control group (225 patients) for six months, while conventional therapy for heart failure was maintained. The primary end points were the New York Heart Association functional class, quality of life, and the distance walked in six minutes.
  
  
  RESULTS
  As compared with the control group, patients assigned to cardiac resynchronization experienced an improvement in the distance walked in six minutes (+39 vs. +10 m, P=0.005), functional class (P<0.001), quality of life (-18.0 vs. -9.0 points, P= 0.001), time on the treadmill during exercise testing (+81 vs. +19 sec, P=0.001), and ejection fraction (+4.6 percent vs. -0.2 percent, P<0.001). In addition, fewer patients in the group assigned to cardiac resynchronization than control patients required hospitalization (8 percent vs. 15 percent) or intravenous medications (7 percent vs. 15 percent) for the treatment of heart failure (P<0.05 for both comparisons). Implantation of the device was unsuccessful in 8 percent of patients and was complicated by refractory hypotension, bradycardia, or asystole in four patients (two of whom died) and by perforation of the coronary sinus requiring pericardiocentesis in two others.
  
  
  CONCLUSIONS
  Cardiac resynchronization results in significant clinical improvement in patients who have moderate-to-severe heart failure and an intraventricular conduction delay.
authors.affiliation: Division of Cardiovascular Medicine, University of Kentucky College of Medicine, Lexington 40536-0284, USA. wtabra2@uky.edu
authors.forename: William T
authors.initials: WT
authors.lastname: Abraham
authors.forename: Westby G
authors.initials: WG
authors.lastname: Fisher
authors.forename: Andrew L
authors.initials: AL
authors.lastname: Smith
authors.forename: David B
authors.initials: DB
authors.lastname: Delurgio
authors.forename: Angel R
authors.initials: AR
authors.lastname: Leon
authors.forename: Evan
authors.initials: E
authors.lastname: Loh
authors.forename: Dusan Z
authors.initials: DZ
authors.lastname: Kocovic
authors.forename: Milton
authors.initials: M
authors.lastname: Packer
authors.forename: Alfredo L
authors.initials: AL
authors.lastname: Clavell
authors.forename: David L
authors.initials: DL
authors.lastname: Hayes
authors.forename: Myrvin
authors.initials: M
authors.lastname: Ellestad
authors.forename: Robin J
authors.initials: RJ
authors.lastname: Trupp
authors.forename: Jackie
authors.initials: J
authors.lastname: Underwood
authors.forename: Faith
authors.initials: F
authors.lastname: Pickering
authors.forename: Cindy
authors.initials: C
authors.lastname: Truex
authors.forename: Peggy
authors.initials: P
authors.lastname: McAtee
authors.forename: John
authors.initials: J
authors.lastname: Messenger
mesh_terms: D000368:Aged; D002304:Cardiac Pacing, Artificial / Q000009:adverse effects / Q000379:methods*; D004311:Double-Blind Method; D017079:Exercise Tolerance; D005260:Female; D006333:Heart Failure / Q000145:classification / Q000401:mortality / Q000503:physiopathology / Q000628:therapy*; D006760:Hospitalization; D006801:Humans; D008297:Male; D008875:Middle Aged; D010138:Pacemaker, Artificial / Q000009:adverse effects; D011788:Quality of Life; D013318:Stroke Volume; D016019:Survival Analysis