title: Electrocardiographic parameters predict super-response in cardiac resynchronization therapy.
abstract: BACKGROUND
  Cardiac resynchronization therapy (CRT) is an established treatment for heart failure patients. However, determinants of response to CRT remain elusive. The aim of the study was to assess the value of ECG parameters to predict super-response in CRT patients.
  
  
  METHODS
  A 12-lead surface ECG was recorded at baseline and immediately after CRT-device implantation. Baseline ECG parameters (QRS duration, bundle branch morphology, axis, PR interval, QTc, intrinsicoid deflection) and post-implant paced QRS duration were analyzed; relative change in QRS duration was calculated. Decrease of left ventricular end-systolic volume ≥30% after 12 months was classified as super-response.
  
  
  RESULTS
  In group of 101 patients, 32 (31.7%) were super-responders. There were no significant differences in baseline ECG parameters between super-responders and other patients. Post-implant QRS duration was shorter in super-responders (148 ± 22 ms vs. 162 ± 28 ms; P=0.010). Only in super-responders was significant QRS reduction observed after implantation. Relative QRS shortening was higher in super-responders (12.1% (6.8 to 22.2) vs. 1.7% (-11.9 to 11.8); P=0.005). In a multivariable analysis post-implant QRS duration and relative QRS shortening remained independent predictor of super-response.
  
  
  CONCLUSIONS
  Absolute post-implant QRS duration and relative QRS shortening are the only ECG parameters associated with super-response in CRT. Further prospective studies on larger population are warranted to determine our findings.
authors.affiliation: University Medical Centre Ljubljana, Department of Cardiology, Ljubljana, Slovenia. Electronic address: marta.cvijic@gmail.com.
authors.forename: Marta
authors.initials: M
authors.lastname: Cvijić
authors.affiliation: University Medical Centre Ljubljana, Department of Cardiology, Ljubljana, Slovenia.
authors.forename: David
authors.initials: D
authors.lastname: Žižek
authors.affiliation: University Medical Centre Ljubljana, Department of Cardiology, Ljubljana, Slovenia.
authors.forename: Bor
authors.initials: B
authors.lastname: Antolič
authors.affiliation: University Medical Centre Ljubljana, Department of Cardiology, Ljubljana, Slovenia.
authors.forename: Igor
authors.initials: I
authors.lastname: Zupan
mesh_terms: D000465:Algorithms; D058406:Cardiac Resynchronization Therapy; D003936:Diagnosis, Computer-Assisted / Q000379:methods*; D004562:Electrocardiography / Q000379:methods*; D005260:Female; D006333:Heart Failure / Q000175:diagnosis* / Q000517:prevention & control*; D006801:Humans; D008297:Male; D008875:Middle Aged; D017063:Outcome Assessment, Health Care / Q000379:methods*; D011379:Prognosis; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D016896:Treatment Outcome
keywords: Cardiac resynchronization therapy; ECG; Super-response