title: Twenty-millisecond interventricular difference as assessed by body surface potential mapping identifies patients with clinical improvement after implantation of cardiac resynchronization device.
abstract: OBJECTIVE
  There is little research on the ventricular electrical aspects following cardiac resynchronization therapy (CRT). This study sought to establish electrocardiographic criteria associated to the ventricular electrical activation process that could identify patients with functional class (FC) improvement after CRT, by using the noninvasive method of body surface potential mapping (BSPM).
  
  
  METHODS
  Fifty-six patients with chronic heart failure and left bundle-branch block (LBBB), who had undergone CRT, with mean age 59.9+/-10.8 years, left ventricular ejection fraction 30.9+/-8.3%, QRS 184+/-35 ms, FC (NYHA) II - 16%, III - 68% and IV - 16%, were selected. Through the 87-lead BSPM isochronous maps, ventricular activation times (VAT) of both right (RV) and left ventricles (LV) were analysed, in two situations: (1) native LBBB and (2) during biventricular pacing. After CRT, patients were divided in two groups: with and without FC improvement. The VATs were compared by the Mann-Whitney's test. The ratio of patients with and without FC improvement who showed RV-to-LV VAT difference =or<20 ms, and >20 ms, was compared using the Fisher's test. Significance level was accepted as p=or<0.05.
  
  
  RESULTS
  Clinical characteristics of patients before CRT were similar in the groups. Patients with FC improvement (47) had RV-to-LV VAT difference during biventricular pacing shorter than those without FC improvement (14.40+/-13.0 ms vs 23.8+/-9.4 ms, p=0.0151). Moreover, the majority of patients with FC improvement had an RV-to-LV VAT difference =or<20 ms during biventricular pacing (70% vs 22%, RR 5.8, CI 95% 1.334-25.517, p=0.01).
  
  
  CONCLUSIONS
  The RV-to-LV ventricular activation time difference of less than or equal to 20 milliseconds, as characterised by BSPM, could identify patients who presented with improved functional class after undergoing CRT.
authors.affiliation: Electrocardiology Service, Heart Institute of the University of São Paulo Medical School, São Paulo, Brazil. nsamesima@hotmail.com
authors.forename: Nelson
authors.initials: N
authors.lastname: Samesima
authors.forename: Roberto
authors.initials: R
authors.lastname: Douglas
authors.forename: Nancy
authors.initials: N
authors.lastname: Tobias
authors.forename: Anísio
authors.initials: A
authors.lastname: Pedrosa
authors.forename: Martino
authors.initials: M
authors.lastname: Martinelli Filho
authors.forename: José Antonio
authors.initials: JA
authors.lastname: Ramires
authors.forename: Carlos Alberto
authors.initials: CA
authors.lastname: Pastore
mesh_terms: D018780:Body Surface Potential Mapping; D002037:Bundle-Branch Block / Q000150:complications / Q000503:physiopathology* / Q000628:therapy; D002304:Cardiac Pacing, Artificial; D017147:Defibrillators, Implantable; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology*; D006333:Heart Failure / Q000150:complications / Q000503:physiopathology* / Q000628:therapy; D006801:Humans; D008297:Male; D008875:Middle Aged