title: Non-invasive, model-based measures of ventricular electrical dyssynchrony for predicting CRT outcomes.
abstract: OBJECTIVE
  Left ventricular activation delay due to left bundle branch block (LBBB) is an important determinant of the severity of dyssynchronous heart failure (DHF). We investigated whether patient-specific computational models constructed from non-invasive measurements can provide measures of baseline dyssynchrony and its reduction after CRT that may explain the degree of long-term reverse ventricular remodelling.
  
  
  RESULTS
  LV end-systolic volume reduction (ΔESVLV) measured by 2D trans-thoracic echocardiography in eight patients following 6 months of CRT was significantly (P < 0.05) greater in responders (26 ± 20%, n = 4) than non-responders (11 ± 16%, n = 4). LV reverse remodelling did not correlate with baseline QRS duration or its change after biventricular pacing, but did correlate with baseline LV endocardial activation measured by electroanatomic mapping (R2=0.71, P < 0.01). Patient-specific models of LBBB ventricular activation with parameters obtained by matching model-computed vectorcardiograms (VCG) to those derived from standard patient ECGs yielded LV endocardial activation times that correlated well with those measured from endocardial maps (R2=0.90). Model-computed 3D LV activation times correlated strongly with the reduction in LVESV (R2=0.93, P < 0.001). Computed decreases due to simulated CRT in the time delay between LV septal and lateral activation correlated strongly with ΔESVLV(R2=0.92, P < 0.001). Models also suggested that optimizing VV delays may improve resynchronization by this measure of activation delay.
  
  
  CONCLUSIONS
  Patient-specific computational models constructed from non-invasive measurements can compute estimates of LV dyssynchrony and their changes after CRT that may be as good as or better than electroanatomic mapping for predicting long-term reverse remodelling.
authors.affiliation: Department of Bioengineering, University of California, 9500 Gilman Drive, La Jolla, San Diego, CA 92093-0412, USA.|Department of Medicine (Cardiology), University of California, 9500 Gilman Drive, La Jolla, San Diego, CA 92093-0613, USA.
authors.forename: Christopher T
authors.initials: CT
authors.lastname: Villongco
authors.affiliation: Department of Medicine (Cardiology), University of California, 9500 Gilman Drive, La Jolla, San Diego, CA 92093-0613, USA.|US Department of Veterans Affairs San Diego Healthcare System, 3350 La Jolla Village Drive, San Diego, CA 92161, USA.
authors.forename: David E
authors.initials: DE
authors.lastname: Krummen
authors.affiliation: Department of Bioengineering, University of California, 9500 Gilman Drive, La Jolla, San Diego, CA 92093-0412, USA.|Department of Medicine (Cardiology), University of California, 9500 Gilman Drive, La Jolla, San Diego, CA 92093-0613, USA.
authors.forename: Jeffrey H
authors.initials: JH
authors.lastname: Omens
authors.affiliation: Department of Bioengineering, University of California, 9500 Gilman Drive, La Jolla, San Diego, CA 92093-0412, USA amcculloch@ucsd.edu.|Department of Medicine (Cardiology), University of California, 9500 Gilman Drive, La Jolla, San Diego, CA 92093-0613, USA.
authors.forename: Andrew D
authors.initials: AD
authors.lastname: McCulloch
mesh_terms: D000200:Action Potentials; D000368:Aged; D002037:Bundle-Branch Block / Q000175:diagnosis / Q000503:physiopathology / Q000628:therapy*; D058406:Cardiac Resynchronization Therapy / Q000379:methods*; D004562:Electrocardiography; D022062:Electrophysiologic Techniques, Cardiac; D006333:Heart Failure / Q000175:diagnosis / Q000503:physiopathology / Q000628:therapy*; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D008955:Models, Cardiovascular; D066230:Patient-Specific Modeling; D011237:Predictive Value of Tests; D020127:Recovery of Function; D012815:Signal Processing, Computer-Assisted; D013318:Stroke Volume; D013997:Time Factors; D016896:Treatment Outcome; D014672:Vectorcardiography; D018487:Ventricular Dysfunction, Left / Q000175:diagnosis / Q000503:physiopathology / Q000628:therapy*; D016277:Ventricular Function, Left; D020257:Ventricular Remodeling
keywords: Cardiac resynchronization therapy; Computational modelling; Electroanatomic mapping; Heart failure; Left bundle branch block; Vectorcardiogram