title: Cardiac resynchronization therapy in patients with mildly impaired left ventricular function.
abstract: OBJECTIVE
  We sought to determine the unknown effects of cardiac resynchronization therapy (CRT) in patients with a left ventricular ejection fraction (LVEF) >35%. Because of its technical limitations, echocardiography (Echo) may underestimate LVEF, compared with cardiovascular magnetic resonance (CMR).
  
  
  METHODS
  Of 157 patients undergoing CRT (New York Heart Association [NYHA] functional class III or IV, QRS > or = 120 ms), all of whom had a preimplant Echo-LVEF < or =35%, 130 had a CMR-LVEF < or =35% (Group A, 19.7 +/- 7.0%[mean +/- standard deviation]) and 27 had a CMR-LVEF >35% (Group B, 43.6 +/- 7.7%). All patients underwent a CMR scan at baseline and a clinical evaluation, including a 6-minute walk test and a quality of life questionnaire, at baseline and after CRT.
  
  
  RESULTS
  Both groups derived similar improvements in NYHA functional class (A =-1.3, B =-1.2, [mean]), quality of life scores (A =-21.6, B =-33.0; all P < 0.0001 for changes from baseline), and 6-minute walking distance (A = 64.5, B = 70.1 m; P < 0.001 and P < 0.0001, respectively). Symptomatic response rates (increase by > or =1 NYHA classes or 25% 6-minute walking distance) were 79% in group A and 92% in group B. Over a maximum follow-up period of 5.9 years for events, patients in group A were at a higher risk of death from any cause, hospitalization for major cardiovascular events (P = 0.0232), or cardiovascular death (P = 0.0411). There were borderline differences in the risk of death from any cause (P = 0.0664) and cardiovascular death or hospitalization for heart failure (P = 0.0526).
  
  
  CONCLUSIONS
  This observational study suggests that the benefits of CRT extend to patients with a LVEF > 35%.
authors.affiliation: University of Birmingham, Department of Cardiology, Good Hope Hospital, Heart of England NHS Trust, Sutton Coldfield, United Kingdom.
authors.forename: Paul W X
authors.initials: PW
authors.lastname: Foley
authors.forename: Berthold
authors.initials: B
authors.lastname: Stegemann
authors.forename: Russell E A
authors.initials: RE
authors.lastname: Smith
authors.forename: John E
authors.initials: JE
authors.lastname: Sanderson
authors.forename: Francisco
authors.initials: F
authors.lastname: Leyva
mesh_terms: D000368:Aged; D002304:Cardiac Pacing, Artificial / Q000401:mortality*; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D009426:Netherlands / Q000453:epidemiology; D018570:Risk Assessment / Q000379:methods*; D012307:Risk Factors; D013318:Stroke Volume; D016019:Survival Analysis; D015996:Survival Rate; D016896:Treatment Outcome; D018487:Ventricular Dysfunction, Left / Q000175:diagnosis / Q000401:mortality* / Q000517:prevention & control*