title: Cardiac memory in humans: vectocardiographic quantification in cardiac resynchronization therapy.
abstract: BACKGROUND
  "Cardiac memory" (CM) refers to a change in repolarization induced by an altered pathway of activation. The effects of biventricular pacing on CM induction have not been investigated.
  
  
  OBJECTIVE
  To investigate the development of CM during cardiac resynchronization therapy (CRT) through vectorcardiography (VCG).
  
  
  METHODS
  Eleven patients undergoing CRT were enrolled. VCG was acquired during spontaneous ventricular activation at baseline and during AAI and DDD pacing immediately after and 7, 14, 21 and 60 days after the implantation.
  
  
  RESULTS
  At 1-week follow-up, during AAI pacing T vector angles significantly changed (azimuth 23 ± 19°; p = 0.002; elevation 23 ± 27°; p = 0.019) and magnitude significantly increased (baseline 1.13 ± 0.69 mV; 7 days: 1.77 ± 1.27 mV; p = 0.026). T angle changes remained stable throughout the follow-up period while a further significant increase in magnitude was observed at 60 days (2.21 ± 1.50 mV; p = 0.01 vs. baseline and p = 0.04 vs. 7 days). Paced T vector magnitude at implant (2.24 ± 1.25 mV) decreased significantly at 7 days (1.64 ± 1.26 mV; p = 0.030) with a further significant decrease at 60 days (1.40 ± 1.18 mV; p = 0.003 vs. baseline; p = 0.02 vs. 7 days).
  
  
  CONCLUSIONS
  CRT induces a significant change in T vector magnitude, azimuth, and elevation after resumption of spontaneous ventricular activation after 7 days from implantation. While further changes in T vector angle were not observed, after 2 months of CRT a significant decrease of paced T vector magnitude and a significant increase of spontaneous T vector magnitude were observed.
authors.affiliation: Institute of Internal Medicine and Cardiology, University of Florence, Viale Morgagni, 85, 50134, Florence, Italy. lpadeletti@interfree.it
authors.forename: Luigi
authors.initials: L
authors.lastname: Padeletti
authors.forename: Chiara
authors.initials: C
authors.lastname: Fantappiè
authors.forename: Laura
authors.initials: L
authors.lastname: Perrotta
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Ricciardi
authors.forename: Paolo
authors.initials: P
authors.lastname: Pieragnoli
authors.forename: Marco
authors.initials: M
authors.lastname: Chiostri
authors.forename: Sergio
authors.initials: S
authors.lastname: Valsecchi
authors.forename: Maria Cristina
authors.initials: MC
authors.lastname: Porciani
authors.forename: Antonio
authors.initials: A
authors.lastname: Michelucci
authors.forename: Fabio
authors.initials: F
authors.lastname: Fantini
mesh_terms: D000222:Adaptation, Physiological; D000368:Aged; D000369:Aged, 80 and over; D058406:Cardiac Resynchronization Therapy / Q000379:methods*; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology*; D006333:Heart Failure / Q000503:physiopathology* / Q000517:prevention & control*; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D014672:Vectorcardiography / Q000379:methods*
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