title: Cardiac memory in cardiac resynchronization therapy: A vectorcardiographic comparison of biventricular and left ventricular pacing.
abstract: BACKGROUND
  "Cardiac memory" (CM) refers to a change in repolarization induced by an altered pathway of activation, manifested after resumption of spontaneous ventricular activation (SVA).
  
  
  OBJECTIVE
  To investigate for the first time in humans the effects of left ventricular (LV) pacing on CM development through vectorcardiography (VCG).
  
  
  METHODS
  We studied 28 patients with heart failure (HF) and left bundle branch block (LBBB) treated with cardiac resynchronization therapy (CRT). Fourteen patients underwent biventricular (BIV) stimulation; the other 14 underwent LV stimulation only. VCG was acquired during SVA at baseline and during AAI and DDD pacing immediately after and 7 and 90 days after the implant.
  
  
  RESULTS
  At baseline, in both groups, the QRS and T vectors angles were those specific of LBBB pattern. During DDD pacing, QRS vector angle changed to the right and upward in BIV patients while no significant differences were observed in LV patients. During AAI pacing, T vector angle changed significantly in BIV patients, following the direction of the paced QRS and amplitude significantly increased. In LV patients no significant differences in T vector angles were observed. Only T vector amplitude significantly increased at 7 days (p=0.03) and at 90 days (p=0.008 vs baseline).
  
  
  CONCLUSIONS
  In patients with LBBB, BIV pacing induces cardiac memory development as a significant change in T vector magnitude and angle, while LV pacing doesn't induce significant modifications in QRS and T vector angles and CM is manifested only as a significant T vector amplitude change.
authors.affiliation: University of Florence, Italy. Electronic address: laura_perrotta81@hotmail.com.
authors.forename: Laura
authors.initials: L
authors.lastname: Perrotta
authors.affiliation: University of Florence, Italy.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Ricciardi
authors.affiliation: University of Florence, Italy.
authors.forename: Paolo
authors.initials: P
authors.lastname: Pieragnoli
authors.affiliation: University of Florence, Italy.
authors.forename: Martina
authors.initials: M
authors.lastname: Nesti
authors.affiliation: University of Florence, Italy.
authors.forename: Giulia
authors.initials: G
authors.lastname: Pontecorboli
authors.affiliation: University of Florence, Italy.
authors.forename: Fabio
authors.initials: F
authors.lastname: Fantini
authors.affiliation: University of Florence, Italy.
authors.forename: Luigi
authors.initials: L
authors.lastname: Padeletti
mesh_terms: D000368:Aged; D002037:Bundle-Branch Block / Q000150:complications / Q000175:diagnosis* / Q000517:prevention & control*; D058406:Cardiac Resynchronization Therapy / Q000379:methods*; D005260:Female; D006333:Heart Failure / Q000150:complications / Q000175:diagnosis* / Q000517:prevention & control*; D006801:Humans; D008297:Male; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D016896:Treatment Outcome; D014672:Vectorcardiography / Q000379:methods*; D020257:Ventricular Remodeling
keywords: Cardiac memory; Cardiac resynchronization therapy; Left ventricular pacing; T-wave; Vectorcardiography