title: Comparison of efficacy of reverse remodeling and clinical improvement for relatively narrow and wide QRS complexes after cardiac resynchronization therapy for heart failure.
abstract: BACKGROUND
  Cardiac resynchronization therapy (CRT) has been shown to reverse left ventricular (LV) remodeling and improve symptoms in heart failure patients with wide QRS complexes; however, its role in patients with mildly prolonged QRS complexes is unclear. This study investigated if CRT benefited patients with mildly prolonged QRS complexes >120 to 150 ms and explored if the severity of systolic asynchrony determined such a response.
  
  
  RESULTS
  Fifty-eight patients (age 66 +/- 11 years, 66% male) who had undergone CRT were studied prospectively. Of these patients, 27 had QRS duration between 120 and 150 ms (group A), and 31 had QRS duration >150 ms (group B). Tissue Doppler echocardiography and clinical assessment were performed at baseline and 3 months after CRT. Both groups had significant reduction of LV volume and increased ejection fraction, +dP/dt, and sphericity index (all P < 0.05). These improvements were greater in group B and were explained by the higher prevalence of systolic intraventricular asynchrony. Significant reverse remodeling (reduction of LV end-systolic volume >15%) was evident in 46% of group A patients and 68% of group B patients. Improvement in clinical endpoints was observed in both groups (all P < 0.01), although the changes in metabolic equivalent and New York Heart Association functional class were greater in group B. In both groups, systolic asynchrony index (TS-SD) was the most important predictor of reverse remodeling (r =-0.78, P < 0.001) and was the only independent predictor in the multivariate model (beta=-1.80, confidence interval =-2.18 to -1.42, P < 0.001); QRS duration was not. A predefined TS-SD value >32.6 ms had a sensitivity of 94% and specificity of 83% to predict reverse remodeling. Improvement of intraventricular asynchrony after CRT was evident only in responders (P = 0.01).
  
  
  CONCLUSIONS
  Improvement of LV remodeling and clinical status is evident after CRT in heart failure patients with QRS duration >120 to 150 ms. These responders are closely predicted by the severity of prepacing intraventricular asynchrony but not QRS duration.
authors.affiliation: Division of Cardiology, Department of Medicine and Therapeutics, Prince of Wales Hospital, The Chinese University of Hong Kong, Hong Kong. cmyu@cuhk.edu.hk
authors.forename: Cheuk-Man
authors.initials: CM
authors.lastname: Yu
authors.forename: Jeffrey Wing-Hong
authors.initials: JW
authors.lastname: Fung
authors.forename: Chi-Kin
authors.initials: CK
authors.lastname: Chan
authors.forename: Yat-Sun
authors.initials: YS
authors.lastname: Chan
authors.forename: Qing
authors.initials: Q
authors.lastname: Zhang
authors.forename: Hong
authors.initials: H
authors.lastname: Lin
authors.forename: Gabriel W K
authors.initials: GW
authors.lastname: Yip
authors.forename: Leo C C
authors.initials: LC
authors.lastname: Kum
authors.forename: Shun-Ling
authors.initials: SL
authors.lastname: Kong
authors.forename: Yan
authors.initials: Y
authors.lastname: Zhang
authors.forename: John E
authors.initials: JE
authors.lastname: Sanderson
mesh_terms: D000368:Aged; D001145:Arrhythmias, Cardiac / Q000503:physiopathology*; D002304:Cardiac Pacing, Artificial; D002908:Chronic Disease; D015150:Echocardiography, Doppler; D004562:Electrocardiography; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology; D006333:Heart Failure / Q000000981:diagnostic imaging / Q000628:therapy*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010138:Pacemaker, Artificial; D013599:Systole; D016896:Treatment Outcome; D020257:Ventricular Remodeling / Q000502:physiology*