title: Optimal left ventricular endocardial pacing sites for cardiac resynchronization therapy in patients with ischemic cardiomyopathy.
abstract: OBJECTIVE
  We sought to investigate the impact of left ventricular (LV) pacing site on mechanical response to cardiac resynchronization therapy (CRT) in patients with ischemic cardiomyopathy (ICM).
  
  
  BACKGROUND
  CRT reduces morbidity and mortality in patients with dyssynchronous LV failure; however, variability in response, particularly in ICM patients, poses ongoing challenges. Endocardial biventricular (BiV) stimulation may provide more flexibility in LV site selection and yield more natural transmural activation patterns. Whether this applies to ICM and whether optimal LV endocardial pacing locations vary among ICM patients remain unknown.
  
  
  METHODS
  Peak rate of LV pressure increase (dP/dt(max)) was measured at baseline, during VDD pacing at the right ventricular apex, and during BiV pacing from the right ventricular apex and 51 +/- 14 different LV endocardial sites in patients with ICM (n = 11). Seven patients already had an epicardial LV lead (CRT) in place, allowing comparison of epicardial BiV stimulation with that using an endocardial site directly transmural to the CRT-coronary sinus lead tip. Electroanatomic 3-dimensional maps with color-coded dP/dt(max) response defined optimal pacing regions delivering >or=85% of maximal increase in dP/dt(max).
  
  
  RESULTS
  Endocardial BiV pacing improved dP/dt(max) over right ventricular apex pacing in all patients (mean increase 241 +/- 38 mm Hg/s; p < 0.0001). In patients with pre-existing CRT leads, LV endocardial versus epicardial pacing at transmural sites yielded equivalent dP/dt(max) values. However, dP/dt(max) at the best endocardial site exceeded that achieved with the pre-implanted CRT device (mean increase 111 +/- 25 mm Hg/s; p = 0.004). An average of approximately 2 optimal endocardial sites were identified for each patient, located at the extreme basal lateral wall (8 of 11 patients) and other regions (9 of 11). Standard mid-LV free wall pacing yielded suboptimal LV function in 73% of patients. Optimal pacing sites were typically located in LV territories remote (9.3 +/- 3.6 cm) from the infarct zone.
  
  
  CONCLUSIONS
  CRT delivered at best LV endocardial sites is more effective than via pre-implanted coronary sinus lead pacing. The location of optimal LV endocardial pacing varies among patients with ICM, and individual tailoring may improve CRT efficacy in such patients.
authors.affiliation: Division of Cardiology, Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21224, USA. dspragg1@jhmi.edu
authors.forename: David D
authors.initials: DD
authors.lastname: Spragg
authors.forename: Jun
authors.initials: J
authors.lastname: Dong
authors.forename: Barry J
authors.initials: BJ
authors.lastname: Fetics
authors.forename: Robert
authors.initials: R
authors.lastname: Helm
authors.forename: Joseph E
authors.initials: JE
authors.lastname: Marine
authors.forename: Alan
authors.initials: A
authors.lastname: Cheng
authors.forename: Charles A
authors.initials: CA
authors.lastname: Henrikson
authors.forename: David A
authors.initials: DA
authors.lastname: Kass
authors.forename: Ronald D
authors.initials: RD
authors.lastname: Berger
mesh_terms: D000368:Aged; D018780:Body Surface Potential Mapping; D002304:Cardiac Pacing, Artificial / Q000379:methods*; D009202:Cardiomyopathies / Q000503:physiopathology / Q000628:therapy*; D004699:Endocardium; D005260:Female; D006333:Heart Failure / Q000628:therapy; D006352:Heart Ventricles; D006439:Hemodynamics / Q000502:physiology; D006801:Humans; D007511:Ischemia / Q000628:therapy