title: Benefits of cardiac resynchronization therapy for heart failure patients with narrow QRS complexes and coexisting systolic asynchrony by echocardiography.
abstract: OBJECTIVE
  This study was designed to evaluate the role of cardiac resynchronization therapy (CRT) in heart failure (HF) patients with narrow QRS complexes (<120 ms) and echocardiographic evidence of mechanical asynchrony.
  
  
  BACKGROUND
  Cardiac resynchronization therapy is currently recommended to advanced HF patients with prolonged QRS duration. Echocardiographic assessment of systolic mechanical asynchrony has been proven useful to predict a favorable response after CRT.
  
  
  METHODS
  A total of 102 HF patients with New York Heart Association (NYHA) functional class III or IV were enrolled. Among them, 51 had wide QRS (>120 ms) and 51 had narrow QRS (<120 ms). Tissue Doppler imaging (TDI) was employed to select patients with systolic asynchrony (increased asynchrony index) in the narrow-QRS group. Clinical and echocardiographic assessments were performed at baseline and 3 months after CRT.
  
  
  RESULTS
  There was a significant reduction of left ventricular (LV) end-systolic volume in both narrow (122 +/- 42 cc vs. 103 +/- 47 cc, p < 0.001) and wide (148 +/- 74 cc vs. 112 +/- 64 cc, p < 0.001) QRS groups. Improvement of NYHA functional class (both p < 0.001), maximal exercise capacity (both p < 0.05), 6-min hall-walk distance (both p < 0.01), ejection fraction (both p < 0.001), and mitral regurgitation (both p < 0.005) was also observed. In both groups, the degree of baseline mechanical asynchrony determined LV reverse remodeling to a similar extent, as shown by the superimposed regression lines. Withholding CRT for 4 weeks resulted in loss of echocardiographic benefits.
  
  
  CONCLUSIONS
  Cardiac resynchronization therapy for HF patients with narrow QRS complexes and coexisting mechanical asynchrony by TDI results in LV reverse remodeling and improvement of clinical status. The amplitude of benefit is similar to the wide-QRS group provided that similar extent of systolic asynchrony is selected.
authors.affiliation: Division of Cardiology, S. H. Ho Cardiovascular and Stroke Centre, Institute of Vascular Medicine, Department of Medicine and Therapeutics, Prince of Wales Hospital, The Chinese University of Hong Kong, Hong Kong, China. cmyu@cuhk.edu.hk
authors.forename: Cheuk-Man
authors.initials: CM
authors.lastname: Yu
authors.forename: Yat-Sun
authors.initials: YS
authors.lastname: Chan
authors.forename: Qing
authors.initials: Q
authors.lastname: Zhang
authors.forename: Gabriel W K
authors.initials: GW
authors.lastname: Yip
authors.forename: Chi-Kin
authors.initials: CK
authors.lastname: Chan
authors.forename: Leo C C
authors.initials: LC
authors.lastname: Kum
authors.forename: LiWen
authors.initials: L
authors.lastname: Wu
authors.forename: Alex Pui-Wai
authors.initials: AP
authors.lastname: Lee
authors.forename: Yat-Yin
authors.initials: YY
authors.lastname: Lam
authors.forename: Jeffrey Wing-Hong
authors.initials: JW
authors.lastname: Fung
mesh_terms: D000368:Aged; D001145:Arrhythmias, Cardiac / Q000150:complications* / Q000000981:diagnostic imaging*; D002303:Cardiac Output, Low / Q000150:complications / Q000175:diagnosis / Q000503:physiopathology* / Q000628:therapy*; D002304:Cardiac Pacing, Artificial; D004452:Echocardiography; D004562:Electrocardiography; D005260:Female; D006321:Heart / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D012720:Severity of Illness Index; D016896:Treatment Outcome; D016277:Ventricular Function, Left; D020257:Ventricular Remodeling