title: Delayed intrinsicoid deflection onset in surface ECG lateral leads predicts left ventricular reverse remodeling after cardiac resynchronization therapy.
abstract: BACKGROUND
  Up to one-third of the patients who undergo cardiac resynchronization therapy (CRT) are not responders.
  
  
  OBJECTIVE
  To demonstrate that delayed lateral left ventricular activation time determined through time to intrinsicoid deflection onset (ID) predicts response after CRT.
  
  
  METHODS
  The ID in leads I, aVL, V₁ and V₂, and V₅ and V₆ were measured in 135 patients who underwent CRT. A CRT response was defined as a decrease in left ventricular end-systolic volume (LVESV) exceeding 15% at 6 months.
  
  
  RESULTS
  In patients with left bundle branch block or nonspecific intraventricular conduction delay, response was predicted by longer ID in lead I (odds ratio [OR] 3.23; 95% confidence interval (CI) 1.4-7.4; per 20-ms increase), in lead aVL (OR 3.0; 95% CI 1.2-7.3; per 20-ms increase), and in lead I minus lead V₁ (OR 2.4; 95% CI 1.2-4.7) adjusting for baseline QRS duration and LVESV. Results were similar after adjusting for postimplant or change in QRS duration. The ID parameters were better predictors of response than QRS duration parameters. ID in lead I/QRS duration ratio (OR 3.1; 95% CI 1.6-5.9) also increased the odds of response after adjusting for baseline LVESV. Cutoff values for ID in leads--I, 110 ms; aVL, 130 ms; I minus V₁, 90 ms--and ID in lead I/QRS duration ratio of 0.69 yielded a sensitivity and a specificity as high as 83% and 81%.
  
  
  CONCLUSIONS
  Measurement of ID on surface electrocardiography permits a preimplant, noninvasive means of determining left ventricle activation delay; is a good predictor of CRT response; and represents a promising alternative to QRS duration parameters.
authors.affiliation: Division of Cardiovascular Diseases, Mayo Clinic, Rochester, Minnesota 55905, USA.
authors.forename: Freddy
authors.initials: F
authors.lastname: Del-Carpio Munoz
authors.forename: Brian D
authors.initials: BD
authors.lastname: Powell
authors.forename: Yong-Mei
authors.initials: YM
authors.lastname: Cha
authors.forename: Heather J
authors.initials: HJ
authors.lastname: Wiste
authors.forename: Margaret M
authors.initials: MM
authors.lastname: Redfield
authors.forename: Paul A
authors.initials: PA
authors.lastname: Friedman
authors.forename: Samuel J
authors.initials: SJ
authors.lastname: Asirvatham
mesh_terms: D000368:Aged; D002037:Bundle-Branch Block / Q000503:physiopathology / Q000628:therapy*; D058406:Cardiac Resynchronization Therapy / Q000379:methods*; D004562:Electrocardiography / Q000295:instrumentation*; D004566:Electrodes; D004867:Equipment Design; D005260:Female; D005500:Follow-Up Studies; D006329:Heart Conduction System / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D013318:Stroke Volume / Q000502:physiology; D016896:Treatment Outcome; D016277:Ventricular Function, Left / Q000502:physiology*; D020257:Ventricular Remodeling / Q000502:physiology*