title: Cardiac resynchronization therapy with sequential biventricular pacing: impact of echocardiography guided VV delay optimization on acute results.
abstract: BACKGROUND
  Cardiac resynchronization therapy (CRT) improves left ventricular synchrony as evaluated by tissue Doppler imaging (TDI), leading to improved left ventricular performance and reverse remodeling. New CRT devices enable programming of left and right VV delay. The aim of this study was to determine whether sequential biventricular (BiV) pacing by echo-guided programming of VV delay would enhance the response to CRT.
  
  
  METHODS
  15 consecutive patients with severe heart failure and left bundle branch block underwent CRT by BiV device implantation. They were studied with conventional and TDI echo the day before implantation. Left ventricular ejection fraction (LVEF) was determined, and the electromechanical delay (QS), defined as the time interval from the beginning of the QRS to the S wave in pulsed TDI, was assessed in each of the four left ventricular basal segments. The dyssynchrony index was calculated as the difference between the longest and shortest electromechanical delay (QS(max-min)). The parameters were re-evaluated the day after implantation during simultaneous BiV pacing and with seven different VV delays. The optimal VV delay was determined by finding the VV interval corresponding to the maximum aortic velocity time interval (VTI).
  
  
  RESULTS
  QS(max-min) decreased from 85.3 +/- 27.0 msec to 46.7 +/- 23.0 msec (p = 0.0002), LVEF increased from 21.7 +/- 7.3% to 30.0 +/- 7.7% (p = 0.0001) and aortic VTI increased from 12.7 +/- 3.6 cm to 15.2 +/- 4.0 cm (p < 0.0001), with simultaneous BiV pacing. The VV intervals were programmed as follows: LV pre-excitation by 10 msec in five patients, 20 msec in three, 30 msec in two, and 40 msec in three; and RV pre-excitation by 10 msec in one and by 20 msec in one. The maximal aortic VTI obtained with VV delay programming increased from 15.2 +/- 4.0 cm to 17.7 +/- 4.0 cm (p = 0.0005). During optimized sequential BiV pacing, QS(max-min) further decreased from 46.7 +/- 23.0 msec to 30.6 +/- 21.0 msec (p = 0.02) and LVEF further increased from 30.0 +/- 7.7% to 35.0 +/- 7.7% (p = 0.0003).
  
  
  CONCLUSIONS
  Sequential BiV pacing with VV delay optimized by evaluation of aortic VTI enhanced the response to CRT with additional improvements in left ventricular synchrony and left ventricular function compared to simultaneous CRT.
authors.affiliation: Serviço de Cardiologia, Hospital de São Bernardo, Setúbal, Portugal. lparreira@netvisao.pt
authors.forename: Leonor
authors.initials: L
authors.lastname: Parreira
authors.forename: José Ferreira
authors.initials: JF
authors.lastname: Santos
authors.forename: João
authors.initials: J
authors.lastname: Madeira
authors.forename: Lígia
authors.initials: L
authors.lastname: Mendes
authors.forename: Filipe
authors.initials: F
authors.lastname: Seixo
authors.forename: Filomena
authors.initials: F
authors.lastname: Caetano
authors.forename: Cláudia
authors.initials: C
authors.lastname: Lopes
authors.forename: José
authors.initials: J
authors.lastname: Venãncio
authors.forename: Arminda
authors.initials: A
authors.lastname: Mateus
authors.forename: J Lopes
authors.initials: JL
authors.lastname: Inês
authors.forename: Miguel
authors.initials: M
authors.lastname: Mendes
mesh_terms: D000368:Aged; D002037:Bundle-Branch Block / Q000000981:diagnostic imaging / Q000628:therapy*; D002304:Cardiac Pacing, Artificial / Q000379:methods*; D005260:Female; D006333:Heart Failure / Q000000981:diagnostic imaging / Q000628:therapy*; D006801:Humans; D008297:Male; D010138:Pacemaker, Artificial; D013997:Time Factors; D014463:Ultrasonography