title: Maximal electric separation-guided placement of right ventricular lead improves responders in cardiac resynchronization defibrillator therapy.
abstract: BACKGROUND
  Cardiac resynchronization therapy is widely used for the treatment of heart failure. Recent data suggest that electric separation during left ventricular pacing varies within the right ventricle (RV). We hypothesized that placement of the RV lead guided by maximal electric separation (MES) would improve response to cardiac resynchronization therapy compared with standard apical placement.
  
  
  RESULTS
  A single-blind, randomized controlled trial was conducted. Patients eligible for cardiac resynchronization therapy-D were enrolled. Left ventricular lead placement was performed at the coronary sinus branch. The RV outflow tract, septum, and apex were mapped during left ventricular pacing and MES recorded. Patients were randomized to receive either apical placement or RV lead placement at the site mapping MES. Left ventricular ejection fraction, 6-minute walk distance, and New York Heart Association functional class were recorded at baseline and 3 months by blinded observers. Response was defined as at least one of the following: 5% absolute increase in ejection fraction, 50 m increase in 6-minute walk distance, or an increase by >1 functional class. Primary end point was improvement in ejection fraction at 3 months. Fifty patients were randomized (25 MES-guided and 25 apical). Baseline characteristics were similar in the 2 groups. Electric separation was lower in the apex (143 ± 23 versus 168 ± 25 ms in MES group; P=0.01). MES was most commonly septal and rarely apical (4/50 patients). Responders in the MES-guided versus apical group are as follows: Echo 21 versus 13 patients (P=0.032), 6-minute walk distance 19 versus 12 patients (P=0.079), and functional class 22 versus 15 patients (P=0.051). No dislodgment or reposition for suboptimal defibrillation tests was reported.
  
  
  CONCLUSIONS
  MES-guided placement of the RV lead improves cardiac resynchronization therapy responders compared with standard apical placement.
authors.affiliation: Division of Cardiology, Kingston General Hospital, Queen's University, Kingston, Ontario, Canada.
authors.forename: Rodrigo I
authors.initials: RI
authors.lastname: Miranda
authors.forename: Michael
authors.initials: M
authors.lastname: Nault
authors.forename: Amer
authors.initials: A
authors.lastname: Johri
authors.forename: Christopher S
authors.initials: CS
authors.lastname: Simpson
authors.forename: Kevin A
authors.initials: KA
authors.lastname: Michael
authors.forename: Hoshiar
authors.initials: H
authors.lastname: Abdollah
authors.forename: Adrian
authors.initials: A
authors.lastname: Baranchuk
authors.forename: Damian P
authors.initials: DP
authors.lastname: Redfearn
mesh_terms: D000368:Aged; D000704:Analysis of Variance; D058406:Cardiac Resynchronization Therapy / Q000379:methods*; D004554:Electric Countershock / Q000295:instrumentation*; D023381:Endpoint Determination; D005260:Female; D006333:Heart Failure / Q000503:physiopathology* / Q000628:therapy*; D006352:Heart Ventricles / Q000503:physiopathology*; D006801:Humans; D008297:Male; D011446:Prospective Studies; D019919:Prosthesis Implantation / Q000379:methods*; D016037:Single-Blind Method; D018709:Statistics, Nonparametric; D013318:Stroke Volume; D016896:Treatment Outcome